Comparison of physical fitness between rice farmers with and without chronic low back pain: a cross-sectional study.

PubMed

Taechasubamorn, Panada; Nopkesorn, Tawesak; Pannarunothai, Supasit

2010-12-01

To compare physical fitness between rice farmers with chronic low back pain (CLBP) and a healthy control group. Sixty-eight rice farmers with CLBP were matched according to age and sex with healthy farmers. All subjects underwent nine physical fitness tests for body composition, lifting capacity, static back extensor endurance, leg strength, static abdominal endurance, handgrip strength, hamstring flexibility, posterior leg and back muscles flexibility and abdominal flexibility. There was no significant difference between CLBP and healthy groups for all tests, except the static back extensor endurance. The back extensor endurance times of the CLBP group was significantly lower than that of the control group (p = 0.002). Static back extensor endurance is the deficient physical fitness in CLBP rice farmers. Back extensor endurance training should be emphasized in both prevention and rehabilitation programs.

Effect of whole body vibration training on lower limb performance in selected high-level ballet students.

PubMed

Annino, Giuseppe; Padua, Elvira; Castagna, Carlo; Di Salvo, Valter; Minichella, Stefano; Tsarpela, Olga; Manzi, Vincenzo; D'Ottavio, Stefano

2007-11-01

The aim of this study was to examine the effects of 8 weeks of whole body vibration (WBV) training on vertical jump ability (CMJ) and knee-extensor performance at selected external loads (50, 70, and 100 kg; leg-press exercise) in elite ballerinas. Twenty-two (age, 21.25 +/- 1.5 years) full-time ballerinas were assigned randomly to the experimental (E, n = 11) and control (C, n = 11) groups. The experimental group was submitted to WBV training 3 times per week before ballet practice. During the training period, the E and C groups undertook the same amount of ballet practice. Posttraining CMJ performance significantly increased in E group (6.3 +/- 3.8%, p < 0.001). Furthermore, E group showed significant (p < 0.05-0.001) posttraining average leg-press power and velocity improvements at all the external loads considered. Consequently, the force-velocity and power-velocity relationship shifted to the right after WBV training in the E group. The results of the present study show that WBV training is an effective short-term training methodology for inducing improvements in knee-extensor explosiveness in elite ballerinas.

Fatigue and recovery from dynamic contractions in men and women differ for arm and leg muscles.

PubMed

Senefeld, Jonathon; Yoon, Tejin; Bement, Marie Hoeger; Hunter, Sandra K

2013-09-01

Whether there is a gender difference in fatigue and recovery from maximal velocity fatiguing contractions and across muscles is not understood. Sixteen men and 19 women performed 90 isotonic contractions at maximal voluntary shortening velocity (maximal velocity concentric contractions, MVCC) with the elbow flexor and knee extensor muscles (separate days) at a load equivalent to 20% maximal voluntary isometric contraction (MVIC). Power (from MVCCs) decreased similarly for men and women for both muscles (P > 0.05). Men and women had similar declines in MVIC of elbow flexors, but men had greater reductions in knee extensor MVIC force and MVIC electromyogram activity than women (P < 0.05). The decline in MVIC and power was greater, and force recovery was slower for the elbow flexors compared with knee extensors. The gender difference in muscle fatigue often observed during isometric tasks was diminished during fast dynamic contractions for upper and lower limb muscles. Copyright © Published 2013 by Wiley Periodicals, Inc. This article is a US Government wmusork and, as such, is in the public domain in the United States of America.

Relationship between lower extremity isometric muscle strength and standing balance in patients with multiple sclerosis.

PubMed

Citaker, Seyit; Guclu-Gunduz, Arzu; Yazici, Gokhan; Bayraktar, Deniz; Nazliel, Bijen; Irkec, Ceyla

2013-01-01

Muscle strength and standing balance decrease in patients with Multiple Sclerosis (MS). The aim of the present study was to investigate the relationship between the lower extremity isometric muscle strength and standing balance in patients with MS. Forty-seven patients with MS and 10 healthy volunteers were included. Neurological disability level was assessed using Expanded Disability Status Scale (EDSS). Isometric strength of seven lower extremity muscles (hip flexor-extensor-abductor-adductor, knee flexor-extensor, and ankle dorsal flexor) was assessed using hand-held dynamometer. Duration of static one-leg standing balance was measured using digital chronometer. Hip flexor-extensor-abductor-adductor, knee flexor-extensor, and ankle dorsal flexor isometric muscle strength, and duration of one-leg standing balance were decreased in patients with MS when compared with controls (p < 0.05). All assessed lower extremity isometric muscle strength and EDSS level was related duration of one-leg standing balance in patients with MS. All assessed lower extremity isometric muscle strength (except ankle dorsal flexor) was related with EDSS. Hip flexor-extensor-abductor-adductor, knee flexor-extensor, and ankle dorsal flexor isometric muscle strength decreases in ambulatory MS patients. Lower extremity muscle weakness and neurological disability level are related with imbalance in MS population. Hip and knee region muscles weakness increases the neurological disability level. For the better balance and decrease neurological disability level whole lower extremity muscle strengthening should be included in rehabilitation programs.

Reconceptualizing Balance: Attributes associated with balance performance

PubMed Central

Thomas, Julia C.; Odonkor, Charles; Griffith, Laura; Holt, Nicole; Percac-Lima, Sanja; Leveille, Suzanne; Ni, Pensheng; Latham, Nancy K.; Jette, Alan M.; Bean, Jonathan F.

2014-01-01

Balance tests are commonly used to screen for impairments that put older adults at risk for falls. The purpose of this study was to determine the attributes that were associated with balance performance as measured by the The Frailty and Injuries: Cooperative Studies of Intervention Techniques (FICSIT) balance test. This study was a cross-sectional secondary analysis of baseline data from a longitudinal cohort study, the Boston Rehabilitative Impairment Study of the Elderly (Boston RISE). Boston RISE was performed in an outpatient rehabilitation research center and evaluated Boston area primary care patients aged 65 to 96 (N=364) with self-reported difficulty or task-modification climbing a flight of stairs or walking ½ of a mile. The outcome measure was standing balance as measured by the FICSIT-4 balance assessment. Other measures included: self-efficacy, pain, depression, executive function, vision, sensory loss, reaction time, kyphosis, leg range of motion, trunk extensor muscle endurance, leg strength and leg velocity at peak power. Participants were 67% female, had an average age of 76.5 (± 7.0) years, an average of 4.1 (± 2.0) chronic conditions, and an average FICSIT-4 score of 6.7 (± 2.2) out of 9. After adjusting for age and gender, attributes significantly associated with balance performance were falls self-efficacy, trunk extensor muscle endurance, sensory loss, and leg velocity at peak power. FICSIT-4 balance performance is associated with a number of behavioral and physiologic attributes, many of which are amenable to rehabilitative treatment. Our findings support a consideration of balance as multidimensional activity as proposed by the current International Classification of Functioning, Disability, and Health (ICF) model. PMID:24952097

Effects of once weekly NMES training on knee extensors fatigue and body composition in a person with spinal cord injury.

PubMed

Gorgey, Ashraf S; Caudill, Caelb; Khalil, Refka E

2016-01-01

Single-subject case (male, 33 years of age, T6 SCI AIS A). To determine the effect of surface neuromuscular electrical stimulation (NMES) training conducted once weekly on improving fatigue resistance as well as regional and whole body composition in an individual with spinal cord injury (SCI). Laboratory setting within a SCI Center. Surface NMES resistance training (RT) of the paralyzed knee extensors was conducted once weekly for 12 weeks using ankle weights. Knee extensor fatigue index was determined by the number of repetitions (reps) achieved out of 30 reps. Total and regional body composition including percentage body fat (%BF), fat mass (FM), lean mass (LM) were conducted before the first session and one week after the last training session using whole-body dual-energy X-ray absorptiometry. The participant had a compliance rate of 83% and he was able to lift 6 and 2 lbs on the right and left legs, respectively. Right knee extensors showed greater fatigue resistance compared to the left one. Leg LM increased by 6% accompanied with decrease in arm, trunk and total body LM by -4.7%, -13%, -5%, respectively. The %BF increased by 8%, 7.3%, 15.5%, 11.5% for arm, legs, trunk and total body. Once weekly of NMES RT evokes local positive changes in leg LM without reciprocating the continuous loss in LM or gain in FM in other regions and total body. Training was effective in increasing strength as well as fatigue resistance of the trained knee extensors.

THE ASSOCIATIONS BETWEEN HIP STRENGTH AND HIP KINEMATICS DURING A SINGLE LEG HOP IN RECREATIONAL ATHLETES POST ACL RECONSTRUCTION COMPARED TO HEALTHY CONTROLS.

PubMed

Tate, Jeremiah; Suckut, Tell; Wages, Jensen; Lyles, Heather; Perrin, Benjamin

2017-06-01

Only a small amount of evidence exists linking hip abductor weakness to dynamic knee valgus during static and dynamic activities. The associations of hip extensor strength and hip kinematics during the landing of a single leg hop are not known. Purpose: To determine if relationships exist between hip extensor and abductor strength and hip kinematics in both involved and uninvolved limb during the landing phase of a single leg hop in recreational athletes post anterior cruciate ligament (ACL) reconstruction. The presence of similar associations was also evaluated in healthy recreational athletes. Controlled Laboratory Study; Cross-sectional. Twenty-four recreational college-aged athletes participated in the study (12 post ACL reconstruction; 12 healthy controls). Sagittal and frontal plane hip kinematic data were collected for five trials during the landing of a single leg hop. Hip extensor and abductor isometric force production was measured using a hand-held dynamometer and normalized to participants' height and weight. Dependent and independent t-tests were used to analyze for any potential differences in hip strength or kinematics within and between groups, respectively. Pearson's r was used to demonstrate potential associations between hip strength and hip kinematics for both limbs in the ACL group and the right limb in the healthy control group. Independent t-tests revealed that participants post ACL reconstruction exhibited less hip extensor strength (0.18 N/Ht*BW vs. 0.25 N/Ht*BW, p=<.01) and landed with greater hip adduction (9.0 º vs. 0.8 º, p=<.01) compared with their healthy counterparts. In the ACL group, Pearson's r demonstrated a moderate and indirect relationship ( r =-.62, p=.03) between hip extensor strength and maximum hip abduction/adduction angle in the involved limb. A moderate and direct relationship between hip abductor strength and maximum hip flexion angle was demonstrated in the both the involved ( r =.62) and uninvolved limb ( r =.65, p=.02). No significant associations were demonstrated between hip extensor or abductor strength and hip flexion and/or abduction/adduction angles in the healthy group. The results suggest that hip extensors may play a role in minimizing hip adduction in the involved limb while the hip abductors seem to play a role in facilitating hip flexion during the landing phase of a single leg hop for both limbs following ACL reconstruction. Researchers and clinicians alike should consider the importance of the hip extensors in playing a more prominent role in contributing to frontal plane motion. Level 2a.

Do oarsmen have asymmetries in the strength of their back and leg muscles?

PubMed

Parkin, S; Nowicky, A V; Rutherford, O M; McGregor, A H

2001-07-01

The aim of this study was to establish whether asymmetry of the strength of the leg and trunk musculature is more prominent in rowers than in controls. Nineteen oarsmen and 20 male controls matched for age, height and body mass performed a series of isokinetic and isometric strength tests on an isokinetic dynamometer. These strength tests focused on the trunk and leg muscles. Comparisons of strength were made between and within groups for right and left symmetry patterns, hamstring: quadriceps ratios, and trunk flexor and extensor ratios. The results revealed no left and right asymmetries in either the knee extensor or flexor strength parameters (including both isometric and isokinetic measures). Knee extensor strength was significantly greater in the rowing population, but knee flexor strength was similar between the two groups. No difference was seen between the groups for the hamstring: quadriceps strength ratio. In the rowing population, stroke side had no influence on leg strength. No differences were observed in the isometric strength of the trunk flexors and extensors between groups, although EMG activity was significantly higher in the rowing population. Patterns of asymmetry of muscle activity were observed between the left and right erector spinae muscles during extension, which was significantly related to rowing side (P < 0.01). These observations could be related to the high incidence of low back pain in oarsmen.

Acute effects of static and dynamic stretching on leg flexor and extensor isokinetic strength in elite women athletes.

PubMed

Sekir, U; Arabaci, R; Akova, B; Kadagan, S M

2010-04-01

The aim of this study was to explore the effects of static and dynamic stretching of the leg flexors and extensors on concentric and eccentric peak torque (PT) and electromyography (EMG) amplitude of the leg extensors and flexors in women athletes. Ten elite women athletes completed the following intervention protocol in a randomized order on separate days: (a) non-stretching (control), (b) static stretching, and (c) dynamic stretching. Stretched muscles were the quadriceps and hamstring muscles. Before and after the stretching or control intervention, concentric and eccentric isokinetic PT and EMG activity of the leg extensors and flexors were measured at 60 and 180 degrees/s. Concentric and eccentric quadriceps and hamstring muscle strength at both test speeds displayed a significant decrease following static stretching (P<0.01-0.001). In contrast, a significant increase was observed after dynamic stretching for these strength parameters (P<0.05-0.001). Parallel to this, normalized EMG amplitude parameters exhibited significant decreases following static (P<0.05-0.001) and significant increases following dynamic stretching (P<0.05-0.001) during quadriceps and hamstring muscle actions at both concentric and eccentric testing modes. Our findings suggest that dynamic stretching, as opposed to static or no stretching, may be an effective technique for enhancing muscle performance during the pre-competition warm-up routine in elite women athletes.

Intra-dialytic electrostimulation of leg extensors may improve exercise tolerance and quality of life in hemodialyzed patients.

PubMed

Dobsak, Petr; Homolka, Pavel; Svojanovsky, Jan; Reichertova, Anna; Soucek, Miroslav; Novakova, Marie; Dusek, Ladislav; Vasku, Jaromir; Eicher, Jean-Christophe; Siegelova, Jarmila

2012-01-01

Hemodialyzed (HD) patients with end-stage renal disease (ESRD) exhibit lower fitness as a consequence of chronic uremic changes that trigger various structural, metabolic, and functional abnormalities in skeletal muscles. The aim of this randomized study was to compare the effect of rehabilitation (RHB) training on a bicycle ergometer and electromyostimulation (EMS) of leg extensors in HD patients with ESRD. Thirty-two HD patients (18 men/14 women; mean age 61.1 ± 8.8 years) were randomized into three groups: (i) exercise training (ET; n = 11) on bicycle ergometer 2 × 20 min; (ii) EMS (n = 11) where stimulation (10 Hz) of leg extensors was applied for 60 min; and (iii) controls (CON; n = 10) without exercise. Exercising was performed between the 2nd and the 3rd hour of HD, three times a week, 20 weeks in total. Ergometric test was performed in order to evaluate peak workload (W(peak)), 6-min corridor walking test (CWT) to evaluate the distance walked, and dynamometry of leg extensors to assess muscle power (F(max)). Urea clearance was monitored and expressed as standard parameters: spKt/V, spKt/V equilibrated (spKt/V-e), and the urea removal ratio (URR). Quality of life (QoL) was assessed by the questionnaire SF-36. A significant increase of F(max) (P = 0.040 in group ET; P = 0.032 in group EMS), of 6-min CWT (P < 0.001 in ET group; P = 0.042 in EMS group), and of W(peak) (P = 0.041 in ET group) was observed. In both exercising groups, significant increase of spKt/V, spKt/V-e, and URR was found as compared with initial values (P < 0.05). In both exercising groups, highly significant changes in summarized mental functions were found (P = 0.001); in summarized physical components, significant improvement was observed in the ET group (P = 0.006). Intradialytic RHB showed comparable positive effects on functional parameters, urea clearance, and QoL. Intradialytic EMS might represent wide therapeutic possibility in the near future. © 2011, Copyright the Authors. Artificial Organs © 2011, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Net joint moments and muscle activation in barbell squats without and with restricted anterior leg rotation.

PubMed

Chiu, Loren Z F; vonGaza, Gabriella L; Jean, Liane M Y

2017-01-01

Muscle utilisation in squat exercise depends on technique. The purpose of this study was to compare net joint moments (NJMs) and muscle activation during squats without and with restricted leg dorsiflexion. Experienced men (n = 5) and women (n = 4) performed full squats at 80% one repetition maximum. 3D motion analysis, force platform and (EMG) data were collected. Restricting anterior leg rotation reduced anterior leg (P = 0.001) and posterior thigh (P < 0.001) rotations, resulting in a smaller knee flexion range of motion (P < 0.001). At maximum squat depth, ankle plantar flexor (P < 0.001) and knee extensor (P < 0.001) NJM were higher in unrestricted squats. Hip extensor NJM (P = 0.14) was not different between squat types at maximum squat depth. Vastus lateralis (P > 0.05), vastus medialis (P > 0.05) and rectus femoris (P > 0.05) EMG were not different between squat types. Unrestricted squats have higher ankle plantar flexor and knee extensor NJM than previously reported from jumping and landing. However, ankle plantar flexor and knee extensor NJM are lower in restricted squats than previous studies of jumping and landing. The high NJM in unrestricted squat exercise performed through a full range of motion suggests this squat type would be more effective to stimulate adaptations in the lower extremity musculature than restricted squats.

THE ASSOCIATIONS BETWEEN HIP STRENGTH AND HIP KINEMATICS DURING A SINGLE LEG HOP IN RECREATIONAL ATHLETES POST ACL RECONSTRUCTION COMPARED TO HEALTHY CONTROLS

PubMed Central

Suckut, Tell; Wages, Jensen; Lyles, Heather; Perrin, Benjamin

2017-01-01

Background Only a small amount of evidence exists linking hip abductor weakness to dynamic knee valgus during static and dynamic activities. The associations of hip extensor strength and hip kinematics during the landing of a single leg hop are not known. Purpose: To determine if relationships exist between hip extensor and abductor strength and hip kinematics in both involved and uninvolved limb during the landing phase of a single leg hop in recreational athletes post anterior cruciate ligament (ACL) reconstruction. The presence of similar associations was also evaluated in healthy recreational athletes. Study Design Controlled Laboratory Study; Cross-sectional Methods Twenty-four recreational college-aged athletes participated in the study (12 post ACL reconstruction; 12 healthy controls). Sagittal and frontal plane hip kinematic data were collected for five trials during the landing of a single leg hop. Hip extensor and abductor isometric force production was measured using a hand-held dynamometer and normalized to participants’ height and weight. Dependent and independent t-tests were used to analyze for any potential differences in hip strength or kinematics within and between groups, respectively. Pearson's r was used to demonstrate potential associations between hip strength and hip kinematics for both limbs in the ACL group and the right limb in the healthy control group. Results Independent t-tests revealed that participants post ACL reconstruction exhibited less hip extensor strength (0.18 N/Ht*BW vs. 0.25 N/Ht*BW, p=<.01) and landed with greater hip adduction (9.0 º vs. 0.8 º, p=<.01) compared with their healthy counterparts. In the ACL group, Pearson's r demonstrated a moderate and indirect relationship (r=-.62, p=.03) between hip extensor strength and maximum hip abduction/adduction angle in the involved limb. A moderate and direct relationship between hip abductor strength and maximum hip flexion angle was demonstrated in the both the involved (r=.62) and uninvolved limb (r=.65, p=.02). No significant associations were demonstrated between hip extensor or abductor strength and hip flexion and/or abduction/adduction angles in the healthy group. Conclusion The results suggest that hip extensors may play a role in minimizing hip adduction in the involved limb while the hip abductors seem to play a role in facilitating hip flexion during the landing phase of a single leg hop for both limbs following ACL reconstruction. Researchers and clinicians alike should consider the importance of the hip extensors in playing a more prominent role in contributing to frontal plane motion. Levels of Evidence Level 2a PMID:28593088

Assessment of isokinetic knee strength in elite young female basketball players: correlation with vertical jump.

PubMed

Rouis, M; Coudrat, L; Jaafar, H; Filliard, J-R; Vandewalle, H; Barthelemy, Y; Driss, T

2015-12-01

To explore the isokinetic concentric strength of the knee muscle groups, and the relationship between the isokinetic knee extensors strength and the vertical jump performance in young elite female basketball players. Eighteen elite female basketball players performed a countermovement jump, and an isokinetic knee test using a Biodex dynamometer. The maximal isokinetic peak torque of the knee extensor and flexor muscles was recorded at four angular velocities (90°/s, 180°/s, 240°/s and 300°/s) for the dominant and non-dominant legs. The conventional hamstring/quadriceps ratio (H/Q) was assessed at each angular velocity for both legs. There was no significant difference between dominant and non-dominant leg whatever the angular velocity (all P>0.05). However, the H/Q ratio enhanced as the velocity increased from 180°/s to 300°/s (P<0.05). Furthermore, low to high significant positive correlations were detected between the isokinetic measures of the knee extensors and the vertical jump height. The highest one was found for the knee extensors peak torque at a velocity of 240°/s (r=0.88, P<0.001). The results accounted for an optimal velocity at which a strong relationship could be obtained between isokinetic knee extensors strength and vertical jump height. Interestingly, the H/Q ratio of the young elite female basketball players in the present study was unusual as it was close to that generally observed in regular sportsmen.

Nonparetic Knee Extensor Strength Is the Determinant of Exercise Capacity of Community-Dwelling Stroke Survivors

PubMed Central

Wang, Wei-Te; Huang, Ling-Tzu; Chou, Ya-Hui; Wei, Ta-Sen; Lin, Chung-Che

2014-01-01

Objective. To investigate the relationship among walking speed, exercise capacity, and leg strength in community dwelling stroke subjects and to evaluate which one was the leading determinant factor of them. Design. This is a descriptive, cross-sectional study. Thirty-five chronic stroke patients who were able to walk independently in their community were enrolled. Walking speed was evaluated by using the 12-meter walking test. A maximal exercise test was used to determine the stroke subjects' exercise capacity. Knee extensor strength, measured as isokinetic torque, was assessed by isokinetic dynamometer. Results. The main walking speed of our subjects was 0.52 m/s. Peak oxygen uptake (VO2 peak) was 1.21 ± 0.43 L/min. Knee extensor strength, no matter whether paretic or nonparetic side, was significantly correlated to 12-meter walking speed and exercise capacity. Linear regression also showed the strength of the affected knee extensor was the determinant of walking speed and that of the nonparetic knee extensor was the determinant of exercise capacity in community dwelling stroke subjects. Conclusions. Walking speed and peak oxygen uptake were markedly decreased after stroke. Knee extensor strength of nonparetic leg was the most important determinant of exercise capacity of the community-dwelling stroke subjects. Knee extensor strengthening should be emphasized to help stroke patient to achieve optimal community living. PMID:25197712

Nonparetic knee extensor strength is the determinant of exercise capacity of community-dwelling stroke survivors.

PubMed

Wang, Wei-Te; Huang, Ling-Tzu; Chou, Ya-Hui; Wei, Ta-Sen; Lin, Chung-Che

2014-01-01

To investigate the relationship among walking speed, exercise capacity, and leg strength in community dwelling stroke subjects and to evaluate which one was the leading determinant factor of them. This is a descriptive, cross-sectional study. Thirty-five chronic stroke patients who were able to walk independently in their community were enrolled. Walking speed was evaluated by using the 12-meter walking test. A maximal exercise test was used to determine the stroke subjects' exercise capacity. Knee extensor strength, measured as isokinetic torque, was assessed by isokinetic dynamometer. The main walking speed of our subjects was 0.52 m/s. Peak oxygen uptake (VO₂ peak) was 1.21 ± 0.43 L/min. Knee extensor strength, no matter whether paretic or nonparetic side, was significantly correlated to 12-meter walking speed and exercise capacity. Linear regression also showed the strength of the affected knee extensor was the determinant of walking speed and that of the nonparetic knee extensor was the determinant of exercise capacity in community dwelling stroke subjects. Walking speed and peak oxygen uptake were markedly decreased after stroke. Knee extensor strength of nonparetic leg was the most important determinant of exercise capacity of the community-dwelling stroke subjects. Knee extensor strengthening should be emphasized to help stroke patient to achieve optimal community living.

Effect of cold indoor environment on physical performance of older women living in the community.

PubMed

Lindemann, Ulrich; Oksa, Juha; Skelton, Dawn A; Beyer, Nina; Klenk, Jochen; Zscheile, Julia; Becker, Clemens

2014-07-01

the effects of cold on older persons' body and mind are not well documented, but with an increased number of older people with decreasing physical performance, these possible effects need to be understood. to investigate the effect of cold indoor environment on physical performance of older women. cross-sectional experimental study with two test conditions. movement laboratory in a climate chamber. eighty-eight community-dwelling, cognitively unimpaired older women (mean age 78 years). participants were exposed to moderately cold (15°C) and warm/normal (25°C) temperature in a climate chamber in random order with an interval of 1 week. The assessment protocol included leg extensor power (Nottingham Power Rig), sit-to-stand performance velocity (linear encoder), gait speed, walk-ratio (i.e. step length/cadence on an instrumented walk way), maximal quadriceps and hand grip strength. physical performance was lower in 15°C room temperature compared with 25°C room temperature for leg extensor power (P < 0.0001), sit-to-stand performance velocity (P < 0.0001), gait speed (P < 0.0001), walk-ratio (P = 0.016) and maximal quadriceps strength (P = 0.015), but not for hand grip strength. in healthy older women a moderately cold indoor environment decreased important physical performance measures necessary for independent living. © The Author 2014. Published by Oxford University Press on behalf of the British Geriatrics Society. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Characteristics and preliminary observations of the influence of electromyostimulation on the size and function of human skeletal muscle during 30 days of simulated microgravity

NASA Technical Reports Server (NTRS)

Duvoisin, Marc R.; Convertino, Victor A.; Buchanan, Paul; Gollnick, Philip A.; Dudley, Gary A.

1989-01-01

The effect of transcutaneous electromyostimulation (EMS) on the development of atrophy and the loss of strength in lower limb musculature in humans exposed to microgravity was determined in three subjects who received EMS twice daily in a 3-d on/1-d off cycle on their dominant leg during 30 days of bedrest. The output waveform from the stimulator was sequenced to the knee extensors, knee flexors, ankle extensors, and ankle flexors, and caused three isometric contractions of each muscle group per minute. It was found that, in the dominant leg, EMS acted to attenuate the changes caused by bedrest, such as reductions in the leg volume, muscle compartment size, cross-sectional area of slow- and fast-twitch fibers, strength, and aerobic enzyme activities, and an increase in leg compliance.

Salvage of the lower limb after a full thickness burn with loss of the knee extensor mechanism: a case report.

PubMed

Sarraf, Khaled M; Atherton, Duncan D; Jayaweera, Asantha R; Gibbons, Charles E; Jones, Isabel

2013-04-01

We report on a 79-year-old woman who underwent salvage of the knee and lower leg using a Whichita Fusion Nail for knee arthrodesis, combined with a medial gastrocnemius muscle flap for a 3% contact burn that resulted in loss of the extensor mechanism. This provided an alternative to above-knee amputation when extensor mechanism reconstruction was not feasible.

Leg kinematics and muscle activity during treadmill running in the cockroach, Blaberus discoidalis: I. Slow running.

PubMed

Watson, J T; Ritzmann, R E

1998-01-01

We have combined high-speed video motion analysis of leg movements with electromyogram (EMG) recordings from leg muscles in cockroaches running on a treadmill. The mesothoracic (T2) and metathoracic (T3) legs have different kinematics. While in each leg the coxa-femur (CF) joint moves in unison with the femurtibia (FT) joint, the relative joint excursions differ between T2 and T3 legs. In T3 legs, the two joints move through approximately the same excursion. In T2 legs, the FT joint moves through a narrower range of angles than the CF joint. In spite of these differences in motion, no differences between the T2 and T3 legs were seen in timing or qualitative patterns of depressor coxa and extensor tibia activity. The average firing frequencies of slow depressor coxa (Ds) and slow extensor tibia (SETi) motor neurons are directly proportional to the average angular velocity of their joints during stance. The average Ds and SETi firing frequency appears to be modulated on a cycle-by-cycle basis to control running speed and orientation. In contrast, while the frequency variations within Ds and SETi bursts were consistent across cycles, the variations within each burst did not parallel variations in the velocity of the relevant joints.

Sex Comparison of Knee Extensor Size, Strength and Fatigue Adaptation to Sprint Interval Training.

PubMed

Bagley, Liam; Al-Shanti, Nasser; Bradburn, Steven; Baig, Osamah; Slevin, Mark; McPhee, Jamie S

2018-03-12

Regular sprint interval training (SIT) improves whole-body aerobic capacity and muscle oxidative potential, but very little is known about knee extensor anabolic or fatigue resistance adaptations, or whether effects are similar for males and females. The purpose of this study was to compare sex-related differences in knee extensor size, torque-velocity relationship and fatigability adaptations to 12 weeks SIT. Sixteen males and fifteen females (mean (SEM) age: 41 (±2.5) yrs) completed measurements of total body composition assessed by DXA, quadriceps muscle cross-sectional area (CSAQ) assessed by MRI, the knee extensor torque-velocity relationship (covering 0 - 240°·sec) and fatigue resistance, which was measured as the decline in torque from the first to the last of 60 repeated concentric knee extensions performed at 180°·sec. SIT consisted of 4 x 20 second sprints on a cycle ergometer set at an initial power output of 175% of power at VO2max, three times per week for 12 weeks. CSAQ increased by 5% (p=0.023) and fatigue resistance improved 4.8% (p=0.048), with no sex differences in these adaptations (sex comparisons: p=0.140 and p=0.282, respectively). Knee extensor isometric and concentric torque was unaffected by SIT in both males and females (p>0.05 for all velocities). 12 weeks SIT, totalling 4 minutes very intense cycling per week, significantly increased fatigue resistance and CSAQ similarly in males and females, but did not significantly increase torque in males or females. These results suggest that SIT is a time-effective training modality for males and females to increase leg muscle size and fatigue resistance.

Muscle group specific changes in the electromechanical delay following short-term resistance training.

PubMed

Stock, Matt S; Olinghouse, Kendra D; Mota, Jacob A; Drusch, Alexander S; Thompson, Brennan J

2016-09-01

The time delay between the onset of a muscle's electrical activity and force is believed to have important functional implications, and has been shown to decrease following resistance training in males. The purpose of this investigation was to examine changes in the voluntary electromechanical delay (EMD) for the leg extensors and flexors following a short-term resistance training intervention in females. Pretest/posttest control group experiment. Twenty-two previously untrained females (mean±SD age=21±2 years; mass=65.4±13.3kg) were randomly assigned to training (n=10) and control (n=12) groups. The training group performed barbell back squats and deadlifts twice per week for four weeks. EMD for the vastus lateralis (extensors) and biceps femoris (flexors) was examined during maximal voluntary contractions at pre- and posttesting. Data were examined using analyses of covariance (ANCOVAs) with the pretest and posttest scores serving as the covariate and dependent variable, respectively, and by evaluating the number of participants that exceeded the minimal difference statistic. For the leg extensors, the adjusted EMD posttest mean for the training group was significantly lower than that for the control group (74.3 vs. 91.8ms; p=0.015; ή(2)=0.275), and five training participants displayed decreases that exceeded the minimal difference. The ANCOVA for the leg flexors was not significant (adjusted means=98.0 vs. 90.0ms; p=0.487; ή(2)=.026). Four weeks of multi-joint resistance training resulted in decreased EMD for the leg extensors, but not the flexors. Copyright © 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Fatigue-related firing of muscle nociceptors reduces voluntary activation of ipsilateral but not contralateral lower limb muscles.

PubMed

Kennedy, David S; Fitzpatrick, Siobhan C; Gandevia, Simon C; Taylor, Janet L

2015-02-15

During fatiguing upper limb exercise, maintained firing of group III/IV muscle afferents can limit voluntary drive to muscles within the same limb. It is not known if this effect occurs in the lower limb. We investigated the effects of group III/IV muscle afferent firing from fatigued ipsilateral and contralateral extensor muscles and ipsilateral flexor muscles of the knee on voluntary activation of the knee extensors. In three experiments, we examined voluntary activation of the knee extensors by measuring changes in superimposed twitches evoked by femoral nerve stimulation. Subjects attended on 2 days for each experiment. On one day a sphygmomanometer cuff occluded blood flow of the fatigued muscles to maintain firing of group III/IV muscle afferents. After a 2-min extensor contraction (experiment 1; n = 9), mean voluntary activation was lower with than without maintained ischemia (47 ± 19% vs. 87 ± 8%, respectively; P < 0.001). After a 2-min knee flexor maximal voluntary contraction (MVC) (experiment 2; n = 8), mean voluntary activation was also lower with than without ischemia (59 ± 21% vs. 79 ± 9%; P < 0.01). After the contralateral (left) MVC (experiment 3; n = 8), mean voluntary activation of the right leg was similar with or without ischemia (92 ± 6% vs. 93 ± 4%; P = 0.65). After fatiguing exercise, activity in group III/IV muscle afferents reduces voluntary activation of the fatigued muscle and nonfatigued antagonist muscles in the same leg. However, group III/IV muscle afferents from the fatigued left leg had no effect on the unfatigued right leg. This suggests that any "crossover" of central fatigue in the lower limbs is not mediated by group III/IV muscle afferents. Copyright © 2015 the American Physiological Society.

Kinetic comparison of older men and women during walk-to-stair descent transition.

PubMed

Singhal, Kunal; Kim, Jemin; Casebolt, Jeffrey; Lee, Sangwoo; Han, Ki Hoon; Kwon, Young-Hoo

2014-09-01

Stair walking is one of the most challenging tasks for older adults, with women reporting higher incidence of falls. The purpose of this study was to investigate the gender differences in kinetics during stair descent transition. Twenty-eight participants (12 male and 16 female; 68.5 and 69.0 years of mean age, respectively) performed stair descent from level walking in a step-over-step manner at a self-selected speed over a custom-made three-step staircase with embedded force plates. Kinematic and force data were combined using inverse dynamics to generate kinetic data for gender comparison. The top and the first step on the staircase were chosen for analysis. Women showed a higher trail leg peak hip abductor moment (-1.0 Nm/kg), lower trail leg peak knee extensor moment and eccentric power (0.74 Nm/kg and 3.15 W/kg), and lower peak concentric power at trail leg ankle joint (1.29 W/kg) as compared to men (p<0.05; -0.82 Nm/kg, 0.89 Nm/kg, 3.83 W/kg, and 1.78 W/kg, respectively). The lead leg knee eccentric power was also lower in women (p<0.05). This decreased ability to exert knee control during stair descent transition may predispose women to a higher risk of fall. Copyright © 2014 Elsevier B.V. All rights reserved.

The effects of two different frequencies of whole-body vibration on knee extensors strength in healthy young volunteers: a randomized trial

PubMed Central

Esmaeilzadeh, S.; Akpinar, M.; Polat, S.; Yildiz, A.; Oral, A.

2015-01-01

The aim of this study was to investigate the effects of two different frequencies of whole-body vibration (WBV) training on knee extensors muscle strength in healthy young volunteers. Twenty-two eligible healthy untrained young women aged 22-31 years were allocated randomly to the 30-Hz (n=11) and 50-Hz (n=11) groups. They participated in a supervised WBV training program that consisted of 24 sessions on a synchronous vertical vibration platform (peak-to-peak displacement: 2-4 mm; type of exercises: semi-squat, one-legged squat, and lunge positions on right leg; set numbers: 2-24) three times per week for 8 weeks. Isometric and dynamic strength of the knee extensors were measured prior to and at the end of the 8-week training. In the 30-Hz group, there was a significant increase in the maximal voluntary isometric contraction (p=0.039) and the concentric peak torque (p=0.018) of knee extensors and these changes were significant (p<0.05) compared with the 50-Hz group. In addition, the eccentric peak torque of knee extensors was increased significantly in both groups (p<0.05); however, there was no significant difference between the two groups (p=0.873). We concluded that 8 weeks WBV training in 30 Hz was more effective than 50 Hz to increase the isometric contraction and dynamic strength of knee extensors as measured using peak concentric torque and equally effective with 50 Hz in improving eccentric torque of knee extensors in healthy young untrained women. PMID:26636279

Lower extremity control during turns initiated with and without hip external rotation.

PubMed

Zaferiou, Antonia M; Flashner, Henryk; Wilcox, Rand R; McNitt-Gray, Jill L

2017-02-08

The pirouette turn is often initiated in neutral and externally rotated hip positions by dancers. This provides an opportunity to investigate how dancers satisfy the same mechanical objectives at the whole-body level when using different leg kinematics. The purpose of this study was to compare lower extremity control strategies during the turn initiation phase of pirouettes performed with and without hip external rotation. Skilled dancers (n=5) performed pirouette turns with and without hip external rotation. Joint kinetics during turn initiation were determined for both legs using ground reaction forces (GRFs) and segment kinematics. Hip muscle activations were monitored using electromyography. Using probability-based statistical methods, variables were compared across turn conditions as a group and within-dancer. Despite differences in GRFs and impulse generation between turn conditions, at least 90% of each GRF was aligned with the respective leg plane. A majority of the net joint moments at the ankle, knee, and hip acted about an axis perpendicular to the leg plane. However, differences in shank alignment relative to the leg plane affected the distribution of the knee net joint moment when represented with respect to the shank versus the thigh. During the initiation of both turns, most participants used ankle plantar flexor moments, knee extensor moments, flexor and abductor moments at the push leg׳s hip, and extensor and abductor moments at the turn leg׳s hip. Representation of joint kinetics using multiple reference systems assisted in understanding control priorities. Copyright © 2017 Elsevier Ltd. All rights reserved.

Measurement of maximal isometric torque and muscle quality of the knee extensors and flexors in healthy 50- to 70-year-old women.

PubMed

Francis, Peter; Toomey, Clodagh; Mc Cormack, William; Lyons, Mark; Jakeman, Philip

2017-07-01

Muscle quality is defined as strength per unit muscle mass. The aim of this study was to measure the maximal voluntary isometric torque of the knee extensor and flexor muscle groups in healthy older women and to develop an index of muscle quality based on the combined knee extensor and flexor torque per unit lean tissue mass (LTM) of the upper leg. One hundred and thirty-six healthy 50- to 70-year-old women completed an initial measurement of isometric peak torque of the knee extensors and flexors (Con-Trex MJ; CMV AG, Dubendorf, Switzerland) that was repeated 7 days later. Subsequently, 131 women returned for whole- and regional-body composition analysis (iDXA ™ ; GE Healthcare, Chalfont St Giles, Buckinghamshire, UK). Isometric peak torque demonstrated excellent within-assessment reliability for both the knee extensors and flexors (ICC range: 0·991-1·000). Test-retest reliability was lower (ICC range: 0·777-0·828) with an observed mean increase of 5% in peak torque [6·2 (17·2) N m] on the second day of assessment (P<0·001). The relative mean decrease in combined isometric peak torque (-12·2%; P = 0·001) was double that of the relative, non-significant, median difference in upper leg LTM (-5·3%; P = 0·102) between those in the 5th and 6th decade. The majority of difference in peak isometric torque came from the knee extensors (15·1 N m, P<0·001 versus 2·4 N m, P = 0·234). Isometric peak torque normalized for upper leg LTM (muscle quality) was 8% lower between decades (P = 0·029). These findings suggest strength per unit tissue may provide a better indication of age-related differences in muscle quality prior to change in LTM. © 2016 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

Dehydration reduces left ventricular filling at rest and during exercise independent of twist mechanics.

PubMed

Stöhr, Eric J; González-Alonso, José; Pearson, James; Low, David A; Ali, Leena; Barker, Horace; Shave, Rob

2011-09-01

The purpose of this study was to determine whether the reduction in stroke volume (SV), previously shown to occur with dehydration and increases in internal body temperatures during prolonged exercise, is caused by a reduction in left ventricular (LV) function, as indicated by LV volumes, strain, and twist ("LV mechanics"). Eight healthy men [age: 20 ± 2, maximal oxygen uptake (VO₂max): 58 ± 7 ml·kg⁻¹·min⁻¹] completed two, 1-h bouts of cycling in the heat (35°C, 50% peak power) without fluid replacement, resulting in 2% and 3.5% dehydration, respectively. Conventional and two-dimensional speckle-tracking echocardiography was used to determine LV volumes, strain, and twist at rest and during one-legged knee-extensor exercise at baseline, both levels of dehydration, and following rehydration. Progressive dehydration caused a significant reduction in end-diastolic volume (EDV) and SV at rest and during one-legged knee-extensor exercise (rest: Δ-33 ± 14 and Δ-21 ± 14 ml, respectively; exercise: Δ-30 ± 10 and Δ-22 ± 9 ml, respectively, during 3.5% dehydration). In contrast to the marked decline in EDV and SV, systolic and diastolic LV mechanics were either maintained or even enhanced with dehydration at rest and during knee-extensor exercise. We conclude that dehydration-induced reductions in SV at rest and during exercise are the result of reduced LV filling, as reflected by the decline in EDV. The concomitant maintenance of LV mechanics suggests that the decrease in LV filling, and consequently ejection, is likely caused by the reduction in blood volume and/or diminished filling time rather than impaired LV function.

Muscle Power Is an Independent Determinant of Pain and Quality of Life in Knee Osteoarthritis.

PubMed

Reid, Kieran F; Price, Lori Lyn; Harvey, William F; Driban, Jeffrey B; Hau, Cynthia; Fielding, Roger A; Wang, Chenchen

2015-12-01

This study examined the relationships between leg muscle strength, power, and perceived disease severity in subjects with knee osteoarthritis (OA) in order to determine whether dynamic leg extensor muscle power would be associated with pain and quality of life in knee OA. Baseline data on 190 subjects with knee OA (mean ± SD age 60.2 ± 10.4 years, body mass index 32.7 ± 7.2 kg/m(2) ) were obtained from a randomized controlled trial. Knee pain was measured using the Western Ontario and McMaster Universities Osteoarthritis Index, and health-related quality of life was assessed using the Short Form 36 (SF-36). One-repetition maximum (1RM) strength was assessed using the bilateral leg press, and peak muscle power was measured during 5 maximum voluntary velocity repetitions at 40% and 70% of 1RM. In univariate analysis, greater muscle power was significantly associated with pain (r = -0.17, P < 0.02) and also significantly and positively associated with SF-36 physical component summary (PCS) scores (r = 0.16, P < 0.05). After adjustment for multiple covariates, muscle power was a significant independent predictor of pain (P ≤ 0.05) and PCS scores (P ≤ 0.04). However, muscle strength was not an independent determinant of pain or quality of life (P ≥ 0.06). Muscle power is an independent determinant of pain and quality of life in knee OA. Compared to strength, muscle power may be a more clinically important measure of muscle function within this population. New trials to systematically examine the impact of muscle power training interventions on disease severity in knee OA are particularly warranted. © 2015, American College of Rheumatology.

Periodization effects during short-term resistance training with equated exercise variables in females.

PubMed

Pelzer, Thiemo; Ullrich, Boris; Pfeiffer, Mark

2017-03-01

During resistance training, volume and load can be altered either gradually (traditional periodization: TP) or with frequent changes between subsequent sessions (daily undulating periodization: DUP). We hypothesized that the periodization model employed would not impact upon training-induced adaptations when exercise variables are equated. Nineteen females (22.0 years, moderate resistance training experience of 27.9 months) performed 6 weeks of knee extensor training with 3 weekly sessions exercising one leg using TP and the contralateral leg using DUP. Training load varied between 40, 60, and 80% of one repetition maximum (1RM). Volume, range of motion, and time under tension were equated for each leg with a biofeedback software. Dynamometry, surface EMG and ultrasonography were used to determine temporal changes of knee extensor maximum voluntary strength (MVC), neural drive of the M. quadriceps femoris (QF) and vastus lateralis (VL) and rectus femoris (RF) muscle architecture. Significant (P < 0.05) gains for isometric (TP 15%, DUP 13%) and isokinetic-concentric (TP 8%, DUP 10%) MVC and knee extensor 1RM (TP 18%, DUP 24%) occurred post training. VL and RF-muscle thickness showed significant (P < 0.05) increases ranging from 12 to 20% for TP and from 13 to 19% for DUP. Furthermore, significant (P < 0.05) increases in VL-pennation angle and VL-fascicle length occurred in both legs while QF EMG remained unchanged. No significant temporal differences were found between both models, displaying similar small to large effect sizes. Periodization is no adaptation trigger during short-term resistance training with equated exercise variables.

The comparison of cold-water immersion and cold air therapy on maximal cycling performance and recovery markers following strength exercises

PubMed Central

Hayter, Kane J.; Schumann, Moritz; Deakin, Glen B.

2016-01-01

This study examined the effects of cold-water immersion (CWI) and cold air therapy (CAT) on maximal cycling performance (i.e. anaerobic power) and markers of muscle damage following a strength training session. Twenty endurance-trained but strength-untrained male (n = 10) and female (n = 10) participants were randomised into either: CWI (15 min in 14 °C water to iliac crest) or CAT (15 min in 14 °C air) immediately following strength training (i.e. 3 sets of leg press, leg extensions and leg curls at 6 repetition maximum, respectively). Creatine kinase, muscle soreness and fatigue, isometric knee extensor and flexor torque and cycling anaerobic power were measured prior to, immediately after and at 24 (T24), 48 (T48) and 72 (T72) h post-strength exercises. No significant differences were found between treatments for any of the measured variables (p > 0.05). However, trends suggested recovery was greater in CWI than CAT for cycling anaerobic power at T24 (10% ± 2%, ES = 0.90), T48 (8% ± 2%, ES = 0.64) and T72 (8% ± 7%, ES = 0.76). The findings suggest the combination of hydrostatic pressure and cold temperature may be favourable for recovery from strength training rather than cold temperature alone. PMID:27069791

The susceptibility of the knee extensors to eccentric exercise-induced muscle damage is not affected by leg dominance but by exercise order.

PubMed

Hody, S; Rogister, B; Leprince, P; Laglaine, T; Croisier, J-L

2013-09-01

The aims of this study were first to compare the response of dominant and non-dominant legs to eccentric exercise and second, to examine whether there is an effect of exercise order on the magnitude of symptoms associated with intense eccentric protocols. Eighteen young men performed three sets of 30 maximal eccentric isokinetic (60° s(-1)) contractions of the knee extensors (range of motion, ROM: 0°-100°, 0 = full extension) using either dominant or non-dominant leg. They repeated a similar eccentric bout using the contralateral leg 6 weeks later. The sequence of leg's use was allocated to create equally balanced groups. Four indirect markers of muscle damage including subjective pain intensity, maximal isometric strength, muscle stiffness and plasma creatine kinase (CK) activity were measured before and 24 h after exercise. All markers changed significantly following the eccentric bout performed either by dominant or non-dominant legs, but no significant difference was observed between legs. Interestingly, the comparison between the first and second eccentric bouts revealed that muscle soreness (-42%, P<0.001), CK activity (-62%, P<0.05) and strength loss (-54%, P<0.01) were significantly lower after the second bout. This study suggests that leg dominance does not influence the magnitude of exercise-induced muscle damage and supports for the first time the existence of a contralateral protection against exercise-induced muscle damage in the lower limbs. © 2013 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

Difficulties in measuring the effect of testosterone replacement therapy on muscle function in older men.

PubMed

Clague, J E; Wu, F C; Horan, M A

1999-08-01

Muscle wasting in older men may be related to androgen deficiency. We have assessed the effect of testosterone replacement therapy on muscle function in the upper and lower limbs of older (age > 60 years) men with blood testosterone levels < 14 nmol/L. Subjects (n = 7 per group) received testosterone enanthate 200 mg i.m. or placebo every 2 weeks in a double blind study over a 12-week period and underwent muscle testing every 4 weeks. A significant increase in blood levels of testosterone and a reduction in levels of sex hormone binding globulin occurred in the treatment group. Total body mass, haemoglobin and packed cell volume also increased significantly (p < 0.05). No improvements in handgrip strength, isometric strength of knee flexors and extensors or leg extensor power were seen in either group. Wide variability in all measures of muscle function were observed in these elderly men suggesting that very large study groups would be required to determine potential treatment benefits on muscle function.

Effects of the Competitive Season on the Isokinetic Muscle Parameters Changes in World-Class Handball Players.

PubMed

Maurelli, Olivier; Bernard, Pierre L; Dubois, Romain; Ahmaidi, Said; Prioux, Jacques

2018-05-25

Maurelli, O, Bernard, PL, Dubois, R, Ahmaidi, S, and Prioux, J. Effects of the competitive season on the isokinetic muscle parameters changes in world-class handball players. J Strength Cond Res XX(X): 000-000, 2018-The aim of this study is to investigate the effects of the competitive season on isokinetic muscular parameters of the lower limbs in world-class handball players. Nineteen, male, world-class, handball players (age, 26.6 ± 5.4 years) participated in the study. Two bilateral isokinetic tests of knee joint flexors (H; hamstring) and extensors (Q; quadriceps) were performed in the beginning and end of the competitive season to determine the peak torque (PT), the mean power, and agonist-antagonist ratio, dominant-nondominant ratio (DNDR), and combined ratio. The results showed a significant decrease in PT values at low angular velocity (60°·s) in concentric mode for Q on dominant leg (p < 0.001). The other PT values for dominant and nondominant legs at low and high angular velocities (240°·s) and in eccentric mode (30°·s) were not significantly different for Q and H. For mean power, values did not change at 60°·s. At 240°·s, we found a significant decrease in H for dominant leg (p < 0.001) but not for nondominant leg. In eccentric mode, the results showed a significant increase on both legs (p < 0.001). For the ratios, values significantly decreased for DNDR at 60°·s for Q (p < 0.03) and for agonist/antagonist ratio at 240°·s for the dominant leg (p < 0.01). The present results highlight the importance of integrating regular strength training sessions during the competitive season in world-class handball players. Accordingly, this study should help trainers to modify their planning to maximize strength and power qualities of the lower limbs of their players in addition to avoiding injuries.

Reliability of a Novel High Intensity One Leg Dynamic Exercise Protocol to Measure Muscle Endurance

PubMed Central

Lepers, Romuald; Marcora, Samuele M.

2016-01-01

We recently developed a high intensity one leg dynamic exercise (OLDE) protocol to measure muscle endurance and investigate the central and peripheral mechanisms of muscle fatigue. The aims of the present study were to establish the reliability of this novel protocol and describe the isokinetic muscle fatigue induced by high intensity OLDE and its recovery. Eight subjects performed the OLDE protocol (time to exhaustion test of the right leg at 85% of peak power output) three times over a week period. Isokinetic maximal voluntary contraction torque at 60 (MVC60), 100 (MVC100) and 140 (MVC140) deg/s was measured pre-exercise, shortly after exhaustion (13 ± 4 s), 20 s (P20) and 40 s (P40) post-exercise. Electromyographic (EMG) signal was analyzed via the root mean square (RMS) for all three superficial knee extensors. Mean time to exhaustion was 5.96 ± 1.40 min, coefficient of variation was 8.42 ± 6.24%, typical error of measurement was 0.30 min and intraclass correlation was 0.795. MVC torque decreased shortly after exhaustion for all angular velocities (all P < 0.001). MVC60 and MVC100 recovered between P20 (P < 0.05) and exhaustion and then plateaued. MVC140 recovered only at P40 (P < 0.05). High intensity OLDE did not alter maximal EMG RMS of the three superficial knee extensors during MVC. The results of this study demonstrate that this novel high intensity OLDE protocol could be reliably used to measure muscle endurance, and that muscle fatigue induced by high intensity OLDE should be examined within ~ 30 s following exhaustion. PMID:27706196

Elicitation and abrupt termination of behaviorally significant catchlike tension in a primitive insect.

PubMed

Hoyle, G; Field, L H

1983-07-01

Sustained steady contractural or catchlike tension (CT) occurs in the metathoracic extensor tibiae muscle of the primitive insect the weta (Orthoptera: Stenopelmatidae) during its characteristic leg-extension defense behavior or following leg-position conditioning. Similar action occurs occasionally in semi-intact preparations and is abruptly turned off by a single peripheral inhibitory impulse. These phenomena were reproduced routinely by first infusing saline containing 10(-8) M (or stronger) octopamine into the muscle for 12 min, and then stimulating the slow excitatory motor neuron SETi with a brief burst. Direct stimulation of the dorsal unpaired median neuron, innervating the extensor tibiae (DUMETi) prior to SETi stimulation, also led to CT. Both octopamine and DUMETi markedly enhanced the tension developed in response to a burst of impulses in SETi.

Effect of unilateral knee extensor fatigue on force and balance of the contralateral limb.

PubMed

Arora, Shruti; Budden, Shawn; Byrne, Jeannette M; Behm, David G

2015-10-01

Fatigue in one limb can decrease force production in the homologous muscle as well as other muscles of the non-fatigued limb affecting balance. The objective of the study was to examine the effect of unilateral knee extensor fatigue on the non-fatigued limb's standing balance, muscle force and activation. Sixteen healthy male subjects performed pre-fatigue balance trials, warm-up exercises, maximum voluntary isometric contractions, a knee extensors fatigue protocol, and post-fatigue balance trials. The fatigue protocol consisted of sets of 15 consecutive isometric contractions of 16 s each with 4 s recovery between repetitions, which were performed at 30% peak force for the dominant knee extensor muscles. Additional sets of contractions continued until a 50% decrease in MVIC knee extensor force was observed. Pre- and post-fatigue balance assessment consisted of transition from double to single leg standing and also single leg standing trials, which were performed bilaterally and in randomized order. The peak force and F100 were significantly decreased by 44.8% (ES = 2.54) and 39.9% (ES = 0.59), respectively, for the fatigued limb post-fatigue. There were no significant changes in the non-fatigued limb's muscle force, activation, muscle onset timing or postural stability parameters. While the lack of change in non-fatigued limb force production is in agreement with some of the previous literature in this area, the lack of effect on postural measures directly contradicts earlier work. It is hypothesized that discrepancies in the duration and the intensity of the fatigue protocol may have accounted for this discrepancy.

Effects of Short- and Long-Duration Space Flight on Neuromuscular Function

NASA Technical Reports Server (NTRS)

Buxton, Roxanne E.; Spiering, Barry A.; Ryder, Jeffrey W.; Ploutz-Snyder, Lori L.; Bloomberg, Jacob J.

2010-01-01

The Functional Task Tests (FTT) is an interdisciplinary study designed to correlate the changes in functional tasks (such as emergency egress, ladder climbing, and hatch opening) with changes in neuromuscular, cardiovascular, and sensorimotor function. One aspect of the FTT, the neuromuscular function test, is used to investigate the neuromuscular component underlying changes in the ability of astronauts to perform functional tasks (representative of critical mission tasks) safely and quickly after flight. PURPOSE: To describe neuromuscular function after short- and long-duration space flight. METHODS: To date, 5 crewmembers on short-duration (10- to 15-day) missions and 3 on long-duration missions have participated. Crewmembers were assessed 30 days before flight, on landing day (short-duration subjects only) and 1, 6, and 30 days after landing. The interpolated twitch technique, which utilizes a combination of maximal voluntary contractions and electrically evoked contractions, was used to assess the maximal voluntary isometric force (MIF) and central activation capacity of the knee extensors. Leg-press and bench-press devices were used to assess MIF and maximal dynamic power of the lower and upper body respectively. Specifically, power was measured during concentric-only ballistic throws of the leg-press sled and bench-press bar loaded to 40% and 30% of MIF respectively. RESULTS: Data are currently being collected from both Shuttle and ISS crewmembers. Emerging data indicate that measures of knee extensor muscle function are decreased with long-duration flight. DISCUSSION: The relationships between flight duration, neural drive, and muscle performance are of particular interest. Ongoing research will add to the current sample size and will focus on defining changes in muscle performance measures after long-duration space flight.

The effects of varying resistance-training loads on intermediate- and high-velocity-specific adaptations.

PubMed

Jones, K; Bishop, P; Hunter, G; Fleisig, G

2001-08-01

The purpose of this study was to compare changes in velocity-specific adaptations in moderately resistance-trained athletes who trained with either low or high resistances. The study used tests of sport-specific skills across an intermediate- to high-velocity spectrum. Thirty NCAA Division I baseball players were randomly assigned to either a low-resistance (40-60% 1 repetition maximum [1RM]) training group or a high-resistance (70-90% 1RM) training group. Both of the training groups intended to maximallv accelerate each repetition during the concentric phase (IMCA). The 10 weeks of training consisted of 4 training sessions a week using basic core exercises. Peak force, velocity, and power were evaluated during set angle and depth jumps as well as weighted jumps using 30 and 50% 1RM. Squat 1RMs were also tested. Although no interactions for any of the jump tests were found, trends supported the hypothesis of velocity-specific training. Percentage gains suggest that the combined use of heavier training loads (70-90% 1RM) and IMCA tend to increase peak force in the lower-body leg and hip extensors. Trends also show that the combined use of lighter training loads (40-60% 1RM) and IMCA tend to increase peak power and peak velocity in the lower-body leg and hip extensors. The high-resistance group improved squats more than the low-resistance group (p < 0.05; +22.7 vs. + 16.1 kg). The results of this study support the use of a combination of heavier training loads and IMCA to increase 1RM strength in the lower bodies of resistance-trained athletes.

Improvement of posture stability by vibratory stimulation following anterior cruciate ligament reconstruction.

PubMed

Brunetti, O; Filippi, G M; Lorenzini, M; Liti, A; Panichi, R; Roscini, M; Pettorossi, V E; Cerulli, G

2006-11-01

Surgical reconstruction of the anterior cruciate ligament (ACL) may reduce, but it does not always eliminate, knee and body instability because of a persisting proprioceptive deficit. In order to enhance body stability, a new protocol of treatment has been proposed consisting of mechanical vibration (100 Hz frequency and < 20 microm amplitude) of the quadriceps muscle in the leg that has undergone ACL reconstruction. In our trials, stimulation was performed when the quadriceps muscle was kept isometrically contracted. Treatment was started one month after surgery. Vibration was applied for short periods over three consecutive days. Nine months after treatment, postural stability was re-evaluated with the subjects standing on one leg with open and with closed eyes. The postural stability of the subjects having undergone vibration treatment, standing on the operated leg was significantly improved one day after treatment when evaluated as mean of speed and elliptic area of the center of pressure. The improvement persisted and increased during the following weeks. Peak torques of the operated leg extensor muscles also increased and reached values close to that of the leg, which had not been operated. Conversely, the balance of the untreated subjects standing on the operated leg did not improve and the restoration of the extensor muscle peak torque was poor. It is concluded that short lasting proprioceptive activation by vibration may lead to a faster and more complete equilibrium recovery probably by permanently changing the network controlling knee posture.

Can maximal and rapid isometric torque characteristics predict playing level in division I American collegiate football players?

PubMed

Thompson, Brennan J; Ryan, Eric D; Sobolewski, Eric J; Smith, Doug B; Conchola, Eric C; Akehi, Kazuma; Buckminster, Tyler

2013-03-01

The purpose of this study was to determine if maximal and rapid isometric torque characteristics could discriminate starters from nonstarters in elite Division I American collegiate football players. Sixteen starters (mean ± SD: age = 20.81 ± 1.28 years; height = 184.53 ± 6.58 cm; and mass = 108.69 ± 22.16 kg) and 15 nonstarters (20.40 ± 1.68 years; 182.27 ± 10.52 cm; and 104.60 ± 22.44 kg) performed isometric maximal voluntary contractions (MVCs) of the leg flexor and extensor muscle groups. Peak torque (PT), rate of torque development (RTD), the time to peak RTD (TTRTDpeak), contractile impulse (IMPULSE), and absolute torque values (TORQUE) at specific time intervals were calculated from a torque-time curve. The results indicated significant and nonsignificant differences between starters and nonstarters for the early rapid leg flexion torque characteristics that included RTD, IMPULSE, and TORQUE at 30 and 50 milliseconds, and TTRTDpeak. These variables also demonstrated the largest effect sizes of all the variables examined (0.71-0.82). None of the leg extensor variables, leg flexion PT, or later leg flexion rapid torque variables (≥ 100 milliseconds) were significant discriminators of playing level. These findings suggest that the early rapid leg flexion torque variables may provide an effective and sensitive muscle performance measurement in the identification of collegiate football talent. Further, coaches and practitioners may use these findings when designing training programs for collegiate football players with the intent to maximize rapid leg flexion characteristics.

Ischemic conditioning increases strength and volitional activation of paretic muscle in chronic stroke: a pilot study.

PubMed

Hyngstrom, Allison S; Murphy, Spencer A; Nguyen, Jennifer; Schmit, Brian D; Negro, Francesco; Gutterman, David D; Durand, Matthew J

2018-05-01

Ischemic conditioning (IC) on the arm or leg has emerged as an intervention to improve strength and performance in healthy populations, but the effects on neurological populations are unknown. The purpose of this study was to quantify the effects of a single session of IC on knee extensor strength and muscle activation in chronic stroke survivors. Maximal knee extensor torque measurements and surface EMG were quantified in 10 chronic stroke survivors (>1 yr poststroke) with hemiparesis before and after a single session of IC or sham on the paretic leg. IC consisted of 5 min of compression with a proximal thigh cuff (inflation pressure = 225 mmHg for IC or 25 mmHg for sham) followed by 5 min of rest. This was repeated five times. Maximal knee extensor strength, EMG magnitude, and motor unit firing behavior were measured before and immediately after IC or sham. IC increased paretic leg strength by 10.6 ± 8.5 Nm, whereas no difference was observed in the sham group (change in sham = 1.3 ± 2.9 Nm, P = 0.001 IC vs. sham). IC-induced increases in strength were accompanied by a 31 ± 15% increase in the magnitude of muscle EMG during maximal contractions and a 5% decrease in motor unit recruitment thresholds during submaximal contractions. Individuals who had the most asymmetry in strength between their paretic and nonparetic legs had the largest increases in strength ( r 2  = 0.54). This study provides evidence that a single session of IC can increase strength through improved muscle activation in chronic stroke survivors. NEW & NOTEWORTHY Present rehabilitation strategies for chronic stroke survivors do not optimally activate paretic muscle, and this limits potential strength gains. Ischemic conditioning of a limb has emerged as an effective strategy to improve muscle performance in healthy individuals but has never been tested in neurological populations. In this study, we show that ischemic conditioning on the paretic leg of chronic stroke survivors can increase leg strength and muscle activation while reducing motor unit recruitment thresholds.

Comparison Between Elite and Subelite Swimmers on Dry Land and Tumble Turn Leg Extensor Force-Time Characteristics.

PubMed

Jones, Julian V; Pyne, David B; Haff, G Greg; Newton, Robert U

2018-06-01

Jones, JV, Pyne, DB, Haff, GG, and Newton, RU. Comparison between elite and subelite swimmers on dry land and tumble turn leg extensor force-time characteristics. J Strength Cond Res 32(6): 1762-1769, 2018-Elite swimmers demonstrate faster swimming turn times that are potentially a result of having better strength-power characteristics than subelite swimmers. We quantified differences between dry-land and swimming turn force-time characteristics in elite swimmers and subelite swimmers. Subelite (11 males: 17.4 ± 0.6 years; 10 females: 17.1 ± 0.6 years) and elite swimmers (15 male: 23.2 ± 2.3 years; 7 female: 21.6 ± 2.5 years) were tested in a cross-sectional design. All swimmers performed a body weight and loaded (20 kg females, 30 kg males) squat jump (SJ) on a portable force platform. On the same day, all swimmers completed swimming turn analyses using a force platform fixed within the pool wall. The magnitude of difference between groups was estimated using a standardized mean difference (effect size statistic). Elite male and female swimmers had superior swimming turn and dry-land force-time characteristics to subelite swimmers in all tests. The standardized mean differences between groups ranged from small to very large. The largest differences were SJ peak velocity unloaded (3.07 ± 1.0 m·s males, 3.49 ± 2.29 m·s females; standardized mean difference ± 90% confidence limits) and SJ peak power unloaded (2.59 ± 0.79 w male, 2.80 ± 1.64 w female) with elite male and female swimmers having a ∼25-50% higher performance than the subelites in both characteristics. Elite swimmers exhibit superior strength and power characteristics for the swimming turn compared with younger and less experienced swimmers. A well-planned and executed strength and conditioning program is needed for emerging swimmers to develop these qualities, as they transition to senior levels.

Secreted Wnt Signaling Inhibitors in Disuse-Induced Bone Loss

DTIC Science & Technology

2014-07-01

goal, we proposed to in‐ duce disuse (using Botox‐induced paralysis of the quadriceps,  hamstrings , and soleus) in one hindlimb of a se‐ ries of mice...muscle paralysis of the lower limb via botulinum toxin (Botox; 20 U/kg) injec on into the  quadriceps,  hamstrings , triceps surae, and leg extensor...kg) injec on into the quadriceps,  hamstrings , tri‐ ceps surae, and leg extensor compartment of the right lower limb.   The le  lower limb was

The structure and function of serially homologous leg motor neurons in the locust. I. Anatomy.

PubMed

Wilson, J A

1979-01-01

Twenty-one prothoracic and 17 mesothoracic motor neurons innervating leg muscles have been identified physiologically and subsequently injected with dye from a microelectrode. A tract containing the primary neurites of motor neurons innervating the retractor unquis, levator and depressor tarsus, flexor tibiae, and reductor femora is described. All motor neurons studied have regions in which their dendritic branches overlap with those of other leg motor neurons. Identified, serially homologous motor neurons in the three thoracic ganglia were found to have: (1) cell bodies at similar locations and morphologically similar primary neurites (e.g., flexor tibiae motor neurons), (2) cell bodies at different locations in each ganglion and morphologically different primary neurites in each ganglion (e.g., fast retractor unguis motor neurons), or (3) cell bodies at similar locations and morphologically similar primary neurites but with a functional switch in one ganglion relative to the function of the neurons in the other two ganglia. As an example of the latter, the morphology of the metathoracic slow extensor tibiae (SETi) motor neurons was similar to that of pro- and mesothoracic fast extensor tibiae (FETi) motor neurons. Similarly the metathoracic FETi bears a striking resemblance to the pro- and the mesothoracic SETi. It is proposed that in the metathoracic ganglion the two extensor tibiae motor neurons have switched functions while retaining similar morphologies relative to the structure and function of their pro- and mesothoracic serial homologues.

Exercise metabolism in human skeletal muscle exposed to prior eccentric exercise

PubMed Central

Asp, Sven; Daugaard, Jens R; Kristiansen, Søren; Kiens, Bente; Richter, Erik A

1998-01-01

The effects of unaccustomed eccentric exercise on exercise metabolism during a subsequent bout of graded concentric exercise were investigated in seven healthy male subjects. Arterial and bilateral femoral venous catheters were inserted 2 days after eccentric exercise of one thigh (eccentric thigh) and blood samples were taken before and during graded two-legged concentric knee-extensor exercise. Muscle biopsies were obtained from the eccentric and control vastus lateralis before (rest) and after (post) the concentric exercise bout. Maximal knee-extensor concentric exercise capacity was decreased by an average of 23 % (P < 0.05) in the eccentric compared with the control thigh. The resting muscle glycogen content was lower in the eccentric thigh than in the control thigh (402 ± 30 mmol (kg dry wt)−1vs. 515 ± 26 mmol (kg dry wt)−1, means ± s.e.m., P < 0.05), and following the two-legged concentric exercise this difference substantially increased (190 ± 46 mmol (kg dry wt)−1vs. 379 ± 58 mmol (kg dry wt)−1, P < 0.05) despite identical power and duration of exercise with the two thighs. There was no measurable difference in glucose uptake between the eccentric and control thigh before or during the graded two-legged concentric exercise. Lactate release was higher from the eccentric thigh at rest and, just before termination of the exercise bout, release of lactate decreased from this thigh (suggesting decreased glycogenolysis), whereas no decrease was found from the contralateral control thigh. Lower glycerol release from the eccentric thigh during the first, lighter part of the exercise (P < 0.05) suggested impaired triacylglycerol breakdown. At rest, sarcolemmal GLUT4 glucose transporter content and glucose transport were similar in the two thighs, and concentric exercise increased sarcolemmal GLUT4 content and glucose transport capacity similarly in the two thighs. It is concluded that in muscle exposed to prior eccentric contractions, exercise at a given power output requires a higher relative workload than in undamaged muscle. This increases utilization of the decreased muscle glycogen stores, contributing to decreased endurance. PMID:9547403

Effects of combined and classic training on different isometric rate of force development parameters of leg extensors in female volleyball players: Discriminative analysis approach

PubMed Central

Branislav, Rajić; Milivoj, Dopsaj; Abella, Carlos Pablos; Deval, Vicente Caratalla; Siniša, Karišik

2013-01-01

Background: The aim of this study is to verify the effects of the combined and classic training of different isometric rates of force development (RFD) parameters of legs. Materials and Methods: Three groups of female athletes was tested: Experimental group (N = 12), classically trained group (N = 11), and control group (N = 20) of athletes. The isometric “standing leg extension” and “Rise on Toes” tests were conducted to evaluate the maximal force, time necessary time to reach it and the RFD analyzed at 100 ms, 180 ms, 250 ms from the onset, and 50-100% of its maximal result. Results: The maximal RFD of legs and calves are dominant explosive parameters. Special training enhanced the RFD of calves of GROUPSPEC at 100 ms (P = 0.05), at 180 ms (P = 0.039), at 250 ms (P = 0.039), at 50% of the Fmax (P = 0.031) and the Fmax (P = 0.05). Domination of GROUPSPEC toward GROUPCLASS and GROUPCONTROL is in case of legs at 100 ms (P = 0.04); at 180 ms (P = 0.04); at 250 ms (P = 0.00); at 50% of the Fmax (P = 0.01) and at the Fmax (P = 0.00); in case of calves at 100 ms (P = 0.07); 180 ms (P = 0.001); at 250 ms (P = 0.00); at 50% of the Fmax (P = 0.00) and at Fmax (P = 0.000). Conclusion: Dominant explosive factors are maximal RFD of leg extensors and calves, and legs at 250ms. Specific training enhanced explosiveness of calves of GROUPSPEC general and partial domination of GROUPSPEC by 87% over GROUPCLASS, and 35% over GROUPCONTROL. PMID:24497853

Effects of fatigue on motor unit firing rate versus recruitment threshold relationships.

PubMed

Stock, Matt S; Beck, Travis W; Defreitas, Jason M

2012-01-01

The purpose of this study was to examine the influence of fatigue on the average firing rate versus recruitment threshold relationships for the vastus lateralis (VL) and vastus medialis. Nineteen subjects performed ten maximum voluntary contractions of the dominant leg extensors. Before and after this fatiguing protocol, the subjects performed a trapezoid isometric muscle action of the leg extensors, and bipolar surface electromyographic signals were detected from both muscles. These signals were then decomposed into individual motor unit action potential trains. For each subject and muscle, the relationship between average firing rate and recruitment threshold was examined using linear regression analyses. For the VL, the linear slope coefficients and y-intercepts for these relationships increased and decreased, respectively, after fatigue. For both muscles, many of the motor units decreased their firing rates. With fatigue, recruitment of higher threshold motor units resulted in an increase in slope for the VL. Copyright © 2011 Wiley Periodicals, Inc.

Flexion Reflex Can Interrupt and Reset the Swimming Rhythm.

PubMed

Elson, Matthew S; Berkowitz, Ari

2016-03-02

The spinal cord can generate the hip flexor nerve activity underlying leg withdrawal (flexion reflex) and the rhythmic, alternating hip flexor and extensor activities underlying locomotion and scratching, even in the absence of brain inputs and movement-related sensory feedback. It has been hypothesized that a common set of spinal interneurons mediates flexion reflex and the flexion components of locomotion and scratching. Leg cutaneous stimuli that evoke flexion reflex can alter the timing of (i.e., reset) cat walking and turtle scratching rhythms; in addition, reflex responses to leg cutaneous stimuli can be modified during cat and human walking and turtle scratching. Both of these effects depend on the phase (flexion or extension) of the rhythm in which the stimuli occur. However, similar interactions between leg flexion reflex and swimming have not been reported. We show here that a tap to the foot interrupted and reset the rhythm of forward swimming in spinal, immobilized turtles if the tap occurred during the swim hip extensor phase. In addition, the hip flexor nerve response to an electrical foot stimulus was reduced or eliminated during the swim hip extensor phase. These two phase-dependent effects of flexion reflex on the swim rhythm and vice versa together demonstrate that the flexion reflex spinal circuit shares key components with or has strong interactions with the swimming spinal network, as has been shown previously for cat walking and turtle scratching. Therefore, leg flexion reflex circuits likely share key spinal interneurons with locomotion and scratching networks across limbed vertebrates generally. The spinal cord can generate leg withdrawal (flexion reflex), locomotion, and scratching in limbed vertebrates. It has been hypothesized that there is a common set of spinal cord neurons that produce hip flexion during flexion reflex, locomotion, and scratching based on evidence from studies of cat and human walking and turtle scratching. We show here that flexion reflex and swimming also share key spinal cord components based on evidence from turtles. Foot stimulation can reset the timing of the swimming rhythm and the response to each foot stimulation can itself be altered by the swim rhythm. Collectively, these studies suggest that spinal cord neuronal networks underlying flexion reflex, multiple forms of locomotion, and scratching share key components. Copyright © 2016 the authors 0270-6474/16/362819-08$15.00/0.

Vibration Platform Training in Women at Risk for Symptomatic Knee Osteoarthritis

PubMed Central

Segal, Neil A.; Glass, Natalie A.; Shakoor, Najia; Wallace, Robert

2013-01-01

Objective To determine whether a platform exercise program with vibration is more effective than the platform exercise alone for improving lower limb muscle strength and power in women age 45-60 with risk factors for knee osteoarthritis (OA). Design Randomized, controlled study Setting Academic center Participants 48 women age 45-60 years old with risk factors for knee OA (history of knee injury or surgery or BMI≥25kg/m2). Interventions Subjects were randomized to a twice weekly lower limb exercise program (quarter squat, posterolateral leg lifts, calf raises) on either a vertically vibrating (35Hz, 2mm), or a non-vibrating platform. Main Outcome Measurements The main outcome measures included change in isokinetic quadriceps strength, leg press power, and stair climb power by 12 weeks. Results 39 out of 48 enrolled participants completed the study (26 vibration and 13 control exercise). Nine participants discontinued the study after randomization mainly due to lack of time. There were no intergroup differences in age, BMI, or activity level. Isokinetic knee extensor strength did not significantly improve in either group. Leg press power improved by 92.0±69.7 W in the vibration group (p<.0001) and 58.2±96.2 W in the control group (p=0.0499), but did not differ between groups (p=0.2262). Stair climb power improved by 53.4±64.7 W in the vibration group (p=0.0004) and 55.7±83.3 W in the control group (p=0.0329), but did not differ between groups (p=0.9272). Conclusions Whole body vibration platforms have been marketed for increasing strength and power. In this group of asymptomatic middle-aged women with risk factors for knee OA, addition of vibration to a 12-week exercise program did not result in significantly greater improvement in lower limb strength or power than participation in the exercise program without vibration. PMID:22981005

Vibration platform training in women at risk for symptomatic knee osteoarthritis.

PubMed

Segal, Neil A; Glass, Natalie A; Shakoor, Najia; Wallace, Robert

2013-03-01

To determine whether a platform exercise program with vibration is more effective than platform exercise alone for improving lower limb muscle strength and power in women ages 45 to 60 with risk factors for knee osteoarthritis (OA). Randomized, controlled study. Academic center. A total of 48 women ages 45-60 years with risk factors for knee OA (a history of knee injury or surgery or body mass index ≥25 kg/m(2)). Subjects were randomly assigned to a twice-weekly lower limb exercise program (quarter squat, posterolateral leg lifts, calf raises, step-ups, and lunges) on either a vertically vibrating platform (35 Hz, 2 mm) or a nonvibrating platform. Change in isokinetic quadriceps strength, leg press power, and stair climb power by 12 weeks. A total of 39 of 48 enrolled participants completed the study (26 vibration and 13 control exercise). Nine participants discontinued the study after randomization mainly because of a lack of time. No intergroup differences in age, body mass index, or activity level existed. Isokinetic knee extensor strength did not significantly improve in either group. Leg press power improved by 92.0 ± 69.7 W in the vibration group (P < .0001) and 58.2 ± 96.2 W in the control group (P = .0499) but did not differ between groups (P = .2262). Stair climb power improved by 53.4 ± 64.7 W in the vibration group (P = .0004) and 55.7 ± 83.3 W in the control group (P = .0329) but did not differ between groups (P = .9272). Whole body vibration platforms have been marketed for increasing strength and power. In this group of asymptomatic middle-aged women with risk factors for knee OA, the addition of vibration to a 12-week exercise program did not result in significantly greater improvement in lower limb strength or power than did participation in the exercise program without vibration. Copyright © 2013 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

Severe pain as a possible cause of dropped head syndrome that was attenuated after amputation of an ischemic lower limb.

PubMed

Maki, Satoshi; Koda, Masao; Furuya, Takeo; Takahashi, Kazuhisa; Yamazaki, Masashi

2016-03-02

Dropped head syndrome (DHS) is defined as weakness of the neck extensor muscles causing a correctable chin-on-the-chest deformity. Here we report the case of a patient with severe pain from lower leg ischemia showing DHS whose symptoms were attenuated by pain relief after amputation of the severely ischemic lower leg. To our knowledge this is the first report indicating that severe pain can cause DHS. A 64-year-old Asian woman was referred to our department with a 1-month history of DHS. She also suffered from severe right foot pain because of limb ischemia. She began to complain of DHS as her gangrenous foot pain worsened. She had neck pain and difficulty with forward gaze. We found no clinical or laboratory findings of neuromuscular disorder or isolated neck extensor myopathy. We amputated her leg below the knee because of progressive foot gangrene. Her severe foot pain resolved after the surgery and her DHS was attenuated. Severe pain can cause DHS. If a patient with DHS has severe pain in another part of the body, we recommend considering aggressive pain relief as a treatment option.

Perioperative Testosterone Supplementation Increases Lean Mass in Healthy Men Undergoing Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial.

PubMed

Wu, Brian; Lorezanza, Dan; Badash, Ido; Berger, Max; Lane, Christianne; Sum, Jonathan C; Hatch, George F; Schroeder, E Todd

2017-08-01

Rehabilitation after repair of the anterior cruciate ligament (ACL) is complicated by the loss of leg muscle mass and strength. Prior studies have shown that preoperative rehabilitation may improve muscle strength and postoperative outcomes. Testosterone supplementation may likewise counteract this muscle loss and potentially improve clinical outcomes. The purpose was to investigate the effect of perioperative testosterone administration on lean mass after ACL reconstruction in men and to examine the effects of testosterone on leg strength and clinical outcome scores. It was hypothesized that testosterone would increase lean mass and leg strength and improve clinical outcome scores relative to placebo. Randomized controlled trial; Level of evidence, 1. Male patients (N = 13) scheduled for ACL reconstruction were randomized into 2 groups: testosterone and placebo. Participants in the testosterone group received 200 mg of intramuscular testosterone weekly for 8 weeks beginning 2 weeks before surgery. Participants in the placebo group received saline following the same schedule. Both groups participated in a standard rehabilitation protocol. The primary outcome was the change in total lean body mass at 6 and 12 weeks. Secondary outcomes were extensor muscle strength, Tegner activity score, and Knee injury and Osteoarthritis Outcome Score. There was an increase in lean mass of a mean 2.7 ± 1.7 kg at 6 weeks postoperatively in the testosterone group compared with a decrease of a mean 0.1 ± 1.5 kg in the placebo group ( P = .01). Extensor muscle strength of the uninjured leg also increased more from baseline in the testosterone group (+20.8 ± 25.6 Nm) compared with the placebo group (-21.4 ± 36.7 Nm) at 12 weeks ( P = .04). There were no significant between-group differences in injured leg strength or clinical outcome scores. There were no negative side effects of testosterone noted. Perioperative testosterone supplementation increased lean mass 6 weeks after ACL reconstruction, suggesting that this treatment may help minimize the effects of muscle atrophy associated with ACL injuries and repair. This study was not powered to detect differences in strength or clinical outcome scores to assess the incidence of testosterone-related adverse events. Supraphysiological testosterone supplementation may be a useful adjunct therapy for counteracting muscle atrophy after ACL reconstruction. Further investigation is necessary to determine the safety profile and effects of perioperative testosterone administration on leg strength and clinical outcomes after surgery. NCT01595581 (ClinicalTrials.gov).

Executive function moderates the role of muscular fitness in determining functional mobility in older adults.

PubMed

Forte, Roberta; Pesce, Caterina; Leite, Joao Costa; De Vito, Giuseppe; Gibney, Eileen R; Tomporowski, Phillip D; Boreham, Colin A G

2013-06-01

Both physical and cognitive factors are known to independently predict functional mobility in older people. However, the combined predictive value of both physical fitness and cognitive factors on functional mobility has been less investigated. The aim of the present study was to assess if cognitive executive functions moderate the role of physical fitness in determining functional mobility of older individuals. Fifty-seven 65- to 75-year-old healthy participants performed tests of functional mobility (habitual and maximal walking speed, maximal walking speed while picking up objects/stepping over obstacles), physical fitness (peak power, knee extensors torque, back/lower limb flexibility, aerobic fitness), and executive function (inhibition and cognitive flexibility). Maximal walking speeds were predicted by physical fitness parameters and their interaction with cognitive factors. Knee extensor torque emerged as the main predictor of all tested locomotor performances at maximal speed. The effect of peak power and back/lower limb flexibility was moderated by executive functions. In particular, inhibition and cognitive flexibility differed in the way in which they moderate the role of fitness. High levels of cognitive flexibility seem necessary to take advantage of leg power for walking at maximal speed. In contrast, high levels of inhibitory capacity seem to compensate for low levels of back/lower limb flexibility when picking up movements are added to a locomotor task. These findings may have important practical implications for the design and implementation of multi-component training programs aimed at optimizing functional abilities in older adults.

A Behavioral Mechanism of How Increases in Leg Strength Improve Old Adults’ Gait Speed

PubMed Central

Uematsu, Azusa; Tsuchiya, Kazushi; Kadono, Norio; Kobayashi, Hirofumi; Kaetsu, Takamasa; Hortobágyi, Tibor; Suzuki, Shuji

2014-01-01

We examined a behavioral mechanism of how increases in leg strength improve healthy old adults’ gait speed. Leg press strength training improved maximal leg press load 40% (p = 0.001) and isometric strength in 5 group of leg muscles 32% (p = 0.001) in a randomly allocated intervention group of healthy old adults (age 74, n = 15) but not in no-exercise control group (age 74, n = 8). Gait speed increased similarly in the training (9.9%) and control (8.6%) groups (time main effect, p = 0.001). However, in the training group only, in line with the concept of biomechanical plasticity of aging gait, hip extensors and ankle plantarflexors became the only significant predictors of self-selected and maximal gait speed. The study provides the first behavioral evidence regarding a mechanism of how increases in leg strength improve healthy old adults’ gait speed. PMID:25310220

Kinematic and kinetic analysis of the fouetté turn in classical ballet.

PubMed

Imura, Akiko; Iino, Yoichi; Kojima, Takeji

2010-11-01

The fouetté turn in classical ballet dancing is a continuous turn with the whipping of the gesture leg and the arms and the bending and stretching of the supporting leg. The knowledge of the movement intensities of both legs for the turn would be favorable for the conditioning of the dancer's body. The purpose of this study was to estimate the intensities. The hypothesis of this study was that the intensities were higher in the supporting leg than in the gesture leg. The joint torques of both legs were determined in the turns performed by seven experienced female classical ballet dancers with inverse dynamics using three high-speed cine cameras and a force platform. The hip abductor torque, knee extensor and plantar flexor torques of the supporting leg were estimated to be exerted up to their maximum levels and the peaks of the torques were larger than the peaks of their matching torques of the gesture leg. Thus, the hypothesis was partly supported. Training of the supporting leg rather than the gesture leg would help ballet dancers perform many revolutions of the fouetté turn continuously.

Validity and reliability of an instrumented leg-extension machine for measuring isometric muscle strength of the knee extensors.

PubMed

Ruschel, Caroline; Haupenthal, Alessandro; Jacomel, Gabriel Fernandes; Fontana, Heiliane de Brito; Santos, Daniela Pacheco dos; Scoz, Robson Dias; Roesler, Helio

2015-05-20

Isometric muscle strength of knee extensors has been assessed for estimating performance, evaluating progress during physical training, and investigating the relationship between isometric and dynamic/functional performance. To assess the validity and reliability of an adapted leg-extension machine for measuring isometric knee extensor force. Validity (concurrent approach) and reliability (test and test-retest approach) study. University laboratory. 70 healthy men and women aged between 20 and 30 y (39 in the validity study and 31 in the reliability study). Intraclass correlation coefficient (ICC) values calculated for the maximum voluntary isometric torque of knee extensors at 30°, 60°, and 90°, measured with the prototype and with an isokinetic dynamometer (ICC2,1, validity study) and measured with the prototype in test and retest sessions, scheduled from 48 h to 72 h apart (ICC1,1, reliability study). In the validity analysis, the prototype showed good agreement for measurements at 30° (ICC2,1 = .75, SEM = 18.2 Nm) and excellent agreement for measurements at 60° (ICC2,1 = .93, SEM = 9.6 Nm) and at 90° (ICC2,1 = .94, SEM = 8.9 Nm). Regarding the reliability analysis, between-days' ICC1,1 were good to excellent, ranging from .88 to .93. Standard error of measurement and minimal detectable difference based on test-retest ranged from 11.7 Nm to 18.1 Nm and 32.5 Nm to 50.1 Nm, respectively, for the 3 analyzed knee angles. The analysis of validity and repeatability of the prototype for measuring isometric muscle strength has shown to be good or excellent, depending on the knee joint angle analyzed. The new instrument, which presents a relative low cost and easiness of transportation when compared with an isokinetic dynamometer, is valid and provides consistent data concerning isometric strength of knee extensors and, for this reason, can be used for practical, clinical, and research purposes.

Eccentric activation and muscle damage: biomechanical and physiological considerations during downhill running.

PubMed Central

Eston, R G; Mickleborough, J; Baltzopoulos, V

1995-01-01

An eccentric muscle activation is the controlled lengthening of the muscle under tension. Functionally, most leg muscles work eccentrically for some part of a normal gait cycle, to support the weight of the body against gravity and to absorb shock. During downhill running the role of eccentric work of the 'anti-gravity' muscles--knee extensors, muscles of the anterior and posterior tibial compartments and hip extensors--is accentuated. The purpose of this paper is to review the relationship between eccentric muscle activation and muscle damage, particularly as it relates to running, and specifically, downhill running. PMID:7551767

Mildly disabled persons with multiple sclerosis use similar net joint power strategies as healthy controls when walking speed increases.

PubMed

Brincks, John; Christensen, Lars Ejsing; Rehnquist, Mette Voigt; Petersen, Jesper; Sørensen, Henrik; Dalgas, Ulrik

2018-01-01

To improve walking in persons with multiple sclerosis (MS), it is essential to understand the underlying mechanisms of walking. This study examined strategies in net joint power generated or absorbed by hip flexors, hip extensors, hip abductors, knee extensors, and plantar flexors in mildly disabled persons with MS and healthy controls at different walking speeds. Thirteen persons with MS and thirteen healthy controls participated and peak net joint power was calculated using 3D motion analysis. In general, no differences were found between speed-matched healthy controls and persons with MS, but the fastest walking speed was significantly higher in healthy controls (2.42 m/s vs. 1.70 m/s). The net joint power increased in hip flexors, hip extensors, hip abductors, knee extensors and plantar flexors in both groups, when walking speed increased. Significant correlations between changes in walking speed and changes in net joint power of plantar flexors, hip extensors and hip flexors existed in healthy controls and persons with MS, and in net knee extensor absorption power of persons with MS only. In contrast to previous studies, these findings suggest that mildly disabled persons with MS used similar kinetic strategies as healthy controls to increase walking speed.

Isokinetic Leg Strength and Power in Elite Handball Players

PubMed Central

González-Ravé, José M.; Juárez, Daniel; Rubio-Arias, Jacobo A.; Clemente-Suarez, Vicente J; Martinez-Valencia, María A; Abian-Vicen, Javier

2014-01-01

Isokinetic strength evaluation of the knee flexion and extension in concentric mode of contraction is an important part of the comprehensive evaluation of athletes. The aims of this study were to evaluate the isokinetic knee peak torque in both the extension and flexion movement in the dominant and non-dominant leg, and the relationship with jumping performance. Twelve elite male handball players from the top Spanish handball division voluntary participated in the study (age 27.68 ± 4.12 years; body mass 92.89 ± 12.34 kg; body height 1.90 ± 0.05 m). The knee extensor and flexor muscle peak torque of each leg were concentrically measured at 60º/s and 180º/s with an isokinetic dynamometer. The Squat Jump and Countermovement Jump were performed on a force platform to determine power and vertical jump height. Non-significant differences were observed between legs in the isokinetic knee extension (dominant= 2.91 ± 0.53 Nm/kg vs non-dominant = 2.70 ± 0.47 Nm/kg at 60º/s; dominant = 1.90 ± 0.31 Nm/kg vs non-dominant = 1.83 ± 0.29 Nm/kg at 180º/s) and flexion peak torques (dominant = 1.76 ± 0.29 Nm/kg vs non-dominant = 1.72 ± 0.39 Nm/kg at 60º/s; dominant = 1.30 ± 0.23 Nm/kg vs non-dominant = 1.27 ± 0.35 Nm/kg at 180º/s). Low and non-significant correlation coefficients were found between the isokinetic peak torques and vertical jumping performance (SJ = 31.21 ± 4.32 cm; CMJ = 35.89 ± 4.20 cm). Similar isokinetic strength was observed between the legs; therefore, no relationship was found between the isokinetic knee flexion and extension peak torques as well as vertical jumping performance in elite handball players. PMID:25114749

Isokinetic leg strength and power in elite handball players.

PubMed

González-Ravé, José M; Juárez, Daniel; Rubio-Arias, Jacobo A; Clemente-Suarez, Vicente J; Martinez-Valencia, María A; Abian-Vicen, Javier

2014-06-28

Isokinetic strength evaluation of the knee flexion and extension in concentric mode of contraction is an important part of the comprehensive evaluation of athletes. The aims of this study were to evaluate the isokinetic knee peak torque in both the extension and flexion movement in the dominant and non-dominant leg, and the relationship with jumping performance. Twelve elite male handball players from the top Spanish handball division voluntary participated in the study (age 27.68 ± 4.12 years; body mass 92.89 ± 12.34 kg; body height 1.90 ± 0.05 m). The knee extensor and flexor muscle peak torque of each leg were concentrically measured at 60º/s and 180º/s with an isokinetic dynamometer. The Squat Jump and Countermovement Jump were performed on a force platform to determine power and vertical jump height. Non-significant differences were observed between legs in the isokinetic knee extension (dominant= 2.91 ± 0.53 Nm/kg vs non-dominant = 2.70 ± 0.47 Nm/kg at 60º/s; dominant = 1.90 ± 0.31 Nm/kg vs non-dominant = 1.83 ± 0.29 Nm/kg at 180º/s) and flexion peak torques (dominant = 1.76 ± 0.29 Nm/kg vs non-dominant = 1.72 ± 0.39 Nm/kg at 60º/s; dominant = 1.30 ± 0.23 Nm/kg vs non-dominant = 1.27 ± 0.35 Nm/kg at 180º/s). Low and non-significant correlation coefficients were found between the isokinetic peak torques and vertical jumping performance (SJ = 31.21 ± 4.32 cm; CMJ = 35.89 ± 4.20 cm). Similar isokinetic strength was observed between the legs; therefore, no relationship was found between the isokinetic knee flexion and extension peak torques as well as vertical jumping performance in elite handball players.

Effects of feedback-based balance and core resistance training vs. Pilates training on balance and muscle function in older women: a randomized-controlled trial.

PubMed

Markovic, Goran; Sarabon, Nejc; Greblo, Zrinka; Krizanic, Valerija

2015-01-01

Aging is associated with decline in physical function that could result in the development of physical impairment and disability. Hence, interventions that simultaneously challenge balance ability, trunk (core) and extremity strength of older adults could be particularly effective in preserving and enhancing these physical functions. The purpose of this study was to compare the effects of feedback-based balance and core resistance training utilizing the a special computer-controlled device (Huber®) with the conventional Pilates training on balance ability, neuromuscular function and body composition of healthy older women. Thirty-four older women (age: 70±4 years) were randomly assigned to a Huber group (n=17) or Pilates group (n=17). Both groups trained for 8 weeks, 3 times a week. Maximal isometric strength of the trunk flexors, extensors, and lateral flexors, leg power, upper-body strength, single- and dual-task static balance, and body composition were measured before and after the intervention programs. Significant group×time interactions and main effects of time (p<0.05) were found for body composition, balance ability in standard and dual-task conditions, all trunk muscle strength variables, and leg power in favor of the Huber group. The observed improvements in balance ability under both standard and dual-task conditions in the Huber group were mainly the result of enhanced postural control in medial-lateral direction (p<0.05). Feedback-based balance and core resistance training proved to be more effective in improving single- and dual-task balance ability, trunk muscle strength, leg power, and body composition of healthy older women than the traditional Pilates training. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Postexercise blood flow restriction does not enhance muscle hypertrophy induced by multiple-set high-load resistance exercise.

PubMed

Madarame, Haruhiko; Nakada, Satoshi; Ohta, Takahisa; Ishii, Naokata

2018-05-01

To test the applicability of postexercise blood flow restriction (PEBFR) in practical training programmes, we investigated whether PEBFR enhances muscle hypertrophy induced by multiple-set high-load resistance exercise (RE). Seven men completed an eight-week RE programme for knee extensor muscles. Employing a within-subject design, one leg was subjected to RE + PEBFR, whereas contralateral leg to RE only. On each exercise session, participants performed three sets of unilateral knee extension exercise at approximately 70% of their one-repetition maximum for RE leg first, and then performed three sets for RE + PEBFR leg. Immediately after completion of the third set, the proximal portion of the RE + PEBFR leg was compressed with an air-pressure cuff for 5 min at a pressure ranging from 100 to 150 mmHg. If participants could perform 10 repetitions for three sets in two consecutive exercise sessions, the work load was increased by 5% at the next exercise session. Muscle thickness and strength of knee extensor muscles were measured before and after the eight-week training period and after the subsequent eight-week detraining period. There was a main effect of time but no condition × time interaction or main effect of condition for muscle thickness and strength. Both muscle thickness and strength increased after the training period independent of the condition. This result suggests that PEBFR would not be an effective training method at least in an early phase of adaptation to high-load resistance exercise. © 2017 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

Muscle "Building."

ERIC Educational Resources Information Center

Schlenker, Richard M.; And Others

1995-01-01

Describes the use of constructivism in teaching human anatomy. Provides directions for constructing arm-hand and leg-foot models that include extensor and flexor muscles and that are easily and cheaply constructed. Lists resources that provide ideas for using such models depending upon the curriculum implemented in a school or the course that is…

n-3 Fatty Acid Supplementation During 4 Weeks of Training Leads to Improved Anaerobic Endurance Capacity, but not Maximal Strength, Speed, or Power in Soccer Players.

PubMed

Gravina, Leyre; Brown, Frankie F; Alexander, Lee; Dick, James; Bell, Gordon; Witard, Oliver C; Galloway, Stuart D R

2017-08-01

Omega-3 fatty acid (n-3 FA) supplementation could promote adaptation to soccer-specific training. We examined the impact of a 4-week period of n-3 FA supplementation during training on adaptations in 1RM knee extensor strength, 20-m sprint speed, vertical jump power, and anaerobic endurance capacity (Yo-Yo test) in competitive soccer players. Twenty six soccer players were randomly assigned to one of two groups: n-3 FA supplementation (n-3 FA; n = 13) or placebo (n = 13). Both groups performed two experimental trial days. Assessments of physical function and respiratory function were conducted pre (PRE) and post (POST) supplementation. Training session intensity, competitive games and nutritional intake were monitored during the 4-week period. No differences were observed in respiratory measurements (FEV1, FVC) between groups. No main effect of treatment was observed for 1RM knee extensor strength, explosive leg power, or 20 m sprint performance, but strength improved as a result of the training period in both groups (p < .05). Yo-Yo test distance improved with training in the n-3 FA group only (p < .01). The mean difference (95% CI) in Yo-Yo test distance completed from PRE to POST was 203 (66-340) m for n-3 FA, and 62 (-94-217) m for placebo, with a moderate effect size (Cohen's d of 0.52). We conclude that 4 weeks of n-3 FA supplementation does not improve strength, power or speed assessments in competitive soccer players. However, the increase in anaerobic endurance capacity evident only in the n-3 FA treatment group suggests an interaction that requires further study.

The effect of age and unilateral leg immobilization for 2 weeks on substrate utilization during moderate-intensity exercise in human skeletal muscle.

PubMed

Vigelsø, A; Gram, M; Dybboe, R; Kuhlman, A B; Prats, C; Greenhaff, P L; Constantin-Teodosiu, D; Birk, J B; Wojtaszewski, J F P; Dela, F; Helge, J W

2016-04-15

This study aimed to provide molecular insight into the differential effects of age and physical inactivity on the regulation of substrate metabolism during moderate-intensity exercise. Using the arteriovenous balance technique, we studied the effect of immobilization of one leg for 2 weeks on leg substrate utilization in young and older men during two-legged dynamic knee-extensor moderate-intensity exercise, as well as changes in key proteins in muscle metabolism before and after exercise. Age and immobilization did not affect relative carbohydrate and fat utilization during exercise, but the older men had higher uptake of exogenous fatty acids, whereas the young men relied more on endogenous fatty acids during exercise. Using a combined whole-leg and molecular approach, we provide evidence that both age and physical inactivity result in intramuscular lipid accumulation, but this occurs only in part through the same mechanisms. Age and inactivity have been associated with intramuscular triglyceride (IMTG) accumulation. Here, we attempt to disentangle these factors by studying the effect of 2 weeks of unilateral leg immobilization on substrate utilization across the legs during moderate-intensity exercise in young (n = 17; 23 ± 1 years old) and older men (n = 15; 68 ± 1 years old), while the contralateral leg served as the control. After immobilization, the participants performed two-legged isolated knee-extensor exercise at 20 ± 1 W (∼50% maximal work capacity) for 45 min with catheters inserted in the brachial artery and both femoral veins. Biopsy samples obtained from vastus lateralis muscles of both legs before and after exercise were used for analysis of substrates, protein content and enzyme activities. During exercise, leg substrate utilization (respiratory quotient) did not differ between groups or legs. Leg fatty acid uptake was greater in older than in young men, and although young men demonstrated net leg glycerol release during exercise, older men showed net glycerol uptake. At baseline, IMTG, muscle pyruvate dehydrogenase complex activity and the protein content of adipose triglyceride lipase, acetyl-CoA carboxylase 2 and AMP-activated protein kinase (AMPK)γ3 were higher in young than in older men. Furthermore, adipose triglyceride lipase, plasma membrane-associated fatty acid binding protein and AMPKγ3 subunit protein contents were lower and IMTG was higher in the immobilized than the contralateral leg in young and older men. Thus, immobilization and age did not affect substrate choice (respiratory quotient) during moderate exercise, but the whole-leg and molecular differences in fatty acid mobilization could explain the age- and immobilization-induced IMTG accumulation. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

The effect of age and unilateral leg immobilization for 2 weeks on substrate utilization during moderate‐intensity exercise in human skeletal muscle

PubMed Central

Gram, M.; Dybboe, R.; Kuhlman, A. B.; Prats, C.; Greenhaff, P. L.; Constantin‐Teodosiu, D.; Birk, J. B.; Wojtaszewski, J. F. P.; Dela, F.; Helge, J. W.

2016-01-01

Key points This study aimed to provide molecular insight into the differential effects of age and physical inactivity on the regulation of substrate metabolism during moderate‐intensity exercise.Using the arteriovenous balance technique, we studied the effect of immobilization of one leg for 2 weeks on leg substrate utilization in young and older men during two‐legged dynamic knee‐extensor moderate‐intensity exercise, as well as changes in key proteins in muscle metabolism before and after exercise.Age and immobilization did not affect relative carbohydrate and fat utilization during exercise, but the older men had higher uptake of exogenous fatty acids, whereas the young men relied more on endogenous fatty acids during exercise.Using a combined whole‐leg and molecular approach, we provide evidence that both age and physical inactivity result in intramuscular lipid accumulation, but this occurs only in part through the same mechanisms. Abstract Age and inactivity have been associated with intramuscular triglyceride (IMTG) accumulation. Here, we attempt to disentangle these factors by studying the effect of 2 weeks of unilateral leg immobilization on substrate utilization across the legs during moderate‐intensity exercise in young (n = 17; 23 ± 1 years old) and older men (n = 15; 68 ± 1 years old), while the contralateral leg served as the control. After immobilization, the participants performed two‐legged isolated knee‐extensor exercise at 20 ± 1 W (∼50% maximal work capacity) for 45 min with catheters inserted in the brachial artery and both femoral veins. Biopsy samples obtained from vastus lateralis muscles of both legs before and after exercise were used for analysis of substrates, protein content and enzyme activities. During exercise, leg substrate utilization (respiratory quotient) did not differ between groups or legs. Leg fatty acid uptake was greater in older than in young men, and although young men demonstrated net leg glycerol release during exercise, older men showed net glycerol uptake. At baseline, IMTG, muscle pyruvate dehydrogenase complex activity and the protein content of adipose triglyceride lipase, acetyl‐CoA carboxylase 2 and AMP‐activated protein kinase (AMPK)γ3 were higher in young than in older men. Furthermore, adipose triglyceride lipase, plasma membrane‐associated fatty acid binding protein and AMPKγ3 subunit protein contents were lower and IMTG was higher in the immobilized than the contralateral leg in young and older men. Thus, immobilization and age did not affect substrate choice (respiratory quotient) during moderate exercise, but the whole‐leg and molecular differences in fatty acid mobilization could explain the age‐ and immobilization‐induced IMTG accumulation. PMID:26801521

Leg blood flow is impaired during small muscle mass exercise in patients with COPD.

PubMed

Iepsen, U W; Munch, G W; Rugbjerg, M; Ryrsø, C K; Secher, N H; Hellsten, Y; Lange, P; Pedersen, B K; Thaning, P; Mortensen, S P

2017-09-01

Skeletal muscle blood flow is regulated to match the oxygen demand and dysregulation could contribute to exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). We measured leg hemodynamics and metabolites from vasoactive compounds in muscle interstitial fluid and plasma at rest, during one-legged knee-extensor exercise, and during arterial infusions of sodium nitroprusside (SNP) and acetylcholine (ACh), respectively. Ten patients with moderate to severe COPD and eight age- and sex-matched healthy controls were studied. During knee-extensor exercise (10 W), leg blood flow was lower in the patients compared with the controls (1.82 ± 0.11 vs. 2.36 ± 0.14 l/min, respectively; P < 0.05), which compromised leg oxygen delivery (372 ± 26 vs. 453 ± 32 ml O 2 /min, respectively; P < 0.05). At rest, plasma endothelin-1 (vasoconstrictor) was higher in the patients with COPD ( P < 0.05) and also tended to be higher during exercise ( P = 0.07), whereas the formation of interstitial prostacyclin (vasodilator) was only increased in the controls. There was no difference between groups in the nitrite/nitrate levels (vasodilator) in plasma or interstitial fluid during exercise. Moreover, patients and controls showed similar vasodilatory capacity in response to both endothelium-independent (SNP) and endothelium-dependent (ACh) stimulation. The results suggest that leg muscle blood flow is impaired during small muscle mass exercise in patients with COPD possibly due to impaired formation of prostacyclin and increased levels of endothelin-1. NEW & NOTEWORTHY This study demonstrates that chronic obstructive pulmonary disease (COPD) is associated with a reduced blood flow to skeletal muscle during small muscle mass exercise. In contrast to healthy individuals, interstitial prostacyclin levels did not increase during exercise and plasma endothelin-1 levels were higher in the patients with COPD. Copyright © 2017 the American Physiological Society.

NOT ALL SINGLE LEG SQUATS ARE EQUAL: A BIOMECHANICAL COMPARISON OF THREE VARIATIONS.

PubMed

Khuu, Anne; Foch, Eric; Lewis, Cara L

2016-04-01

The single leg squat (SLS) is a functional task used by practitioners to evaluate and treat multiple pathologies of the lower extremity. Variations of the SLS may have different neuromuscular and biomechanical demands. The effect of altering the non-stance leg position during the SLS on trunk, pelvic, and lower extremity mechanics has not been reported. The purpose of this study was to compare trunk, pelvic, hip, knee, and ankle kinematics and hip, knee, and ankle kinetics of three variations of the SLS using different non-stance leg positions: SLS-Front, SLS-Middle, and SLS-Back. Sixteen healthy women performed the three SLS tasks while data were collected using a motion capture system and force plates. Joint mechanics in the sagittal, frontal, and transverse planes were compared for the SLS tasks using a separate repeated-measures analysis of variance (ANOVA) for each variable at two analysis points: peak knee flexion (PKF) and 60 ° of knee flexion (60KF). Different non-stance leg positions during the SLS resulted in distinct movement patterns and moments at the trunk, pelvis, and lower extremity. At PKF, SLS-Back exhibited the greatest kinematic differences (p < 0.05) from SLS-Front and SLS-Middle with greater ipsilateral trunk flexion, pelvic anterior tilt and drop, hip flexion and adduction, and external rotation as well as less knee flexion and abduction. SLS-Back also showed the greatest kinetic differences (p < 0.05) from SLS-Front and SLS-Middle with greater hip external rotator moment and knee extensor moment as well as less hip extensor moment and knee adductor moment at PKF. At 60KF, the findings were similar except at the knee. The mechanics of the trunk, pelvis, and lower extremity during the SLS were affected by the position of the non-stance leg in healthy females. Practitioners can use these findings to distinguish between SLS variations and to select the appropriate SLS for assessment and rehabilitation. 3.

Physical performance measures that predict faller status in community-dwelling older adults.

PubMed

Macrae, P G; Lacourse, M; Moldavon, R

1992-01-01

Falls are a leading cause of fatal and nonfatal injuries among the elderly. Accurate determination of risk factors associated with falls in older adults is necessary, not only for individual patient management, but also for the development of fall prevention programs. The purpose of this study was to evaluate the effectiveness of clinical measures, such as the one-legged stance test (OLST), sit-to-stand test (STST), manual muscle tests (MMT), and response speed in predicting faller status in community-dwelling older adults (N = 94, age 60-89 years). The variables assessed were single-leg standing (as measured by OLST), STST, and MMT of 12 different muscle groups (hip flexors, hip abductors, hip adductors, knee flexors, knee extensors, ankle dorsiflexors, ankle plantarflexors, shoulder flexors, shoulder abductors, elbow flexors, elbow extensors, and finger flexors), and speed of response (as measured by a visual hand reaction and movement time task). Of the 94 older adults assessed, 28 (29.7%) reported at least one fall within the previous year. The discriminant analysis revealed that there were six variables that significantly discriminated between fallers and nonfallers. These variables included MMT of the ankle dorsiflexors, knee flexors, hip abductors, and knee extensors, as well as time on the OLST and the STST. The results indicate that simple clinical measures of musculoskeletal function can discriminate fallers from nonfallers in community-dwelling older adults. J Orthop Sports Phys Ther 1992;16(3):123-128.

Whole-body heat stress and exercise stimulate the appearance of platelet microvesicles in plasma with limited influence of vascular shear stress.

PubMed

Wilhelm, Eurico N; González-Alonso, José; Chiesa, Scott T; Trangmar, Steven J; Kalsi, Kameljit K; Rakobowchuk, Mark

2017-11-01

Intense, large muscle mass exercise increases circulating microvesicles, but our understanding of microvesicle dynamics and mechanisms inducing their release remains limited. However, increased vascular shear stress is generally thought to be involved. Here, we manipulated exercise-independent and exercise-dependent shear stress using systemic heat stress with localized single-leg cooling (low shear) followed by single-leg knee extensor exercise with the cooled or heated leg (Study 1, n  = 8) and whole-body passive heat stress followed by cycling (Study 2, n  = 8). We quantified femoral artery shear rates (SRs) and arterial and venous platelet microvesicles (PMV-CD41 + ) and endothelial microvesicles (EMV-CD62E + ). In Study 1, mild passive heat stress while one leg remained cooled did not affect [microvesicle] ( P  ≥ 0.05). Single-leg knee extensor exercise increased active leg SRs by ~12-fold and increased arterial and venous [PMVs] by two- to threefold, even in the nonexercising contralateral leg ( P  < 0.05). In Study 2, moderate whole-body passive heat stress increased arterial [PMV] compared with baseline (mean±SE, from 19.9 ± 1.5 to 35.5 ± 5.4 PMV . μ L -1. 10 3 , P  < 0.05), and cycling with heat stress increased [PMV] further in the venous circulation (from 27.5 ± 2.2 at baseline to 57.5 ± 7.2 PMV . μ L -1. 10 3 during cycling with heat stress, P  < 0.05), with a tendency for increased appearance of PMV across exercising limbs. Taken together, these findings demonstrate that whole-body heat stress may increase arterial [PMV], and intense exercise engaging either large or small muscle mass promote PMV formation locally and systemically, with no influence upon [EMV]. Local shear stress, however, does not appear to be the major stimulus modulating PMV formation in healthy humans. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Lower extremity muscle functions during full squats.

PubMed

Robertson, D G E; Wilson, Jean-Marie J; St Pierre, Taunya A

2008-11-01

The purpose of this research was to determine the functions of the gluteus maximus, biceps femoris, semitendinosus, rectus femoris, vastus lateralis, soleus, gastrocnemius, and tibialis anterior muscles about their associated joints during full (deep-knee) squats. Muscle function was determined from joint kinematics, inverse dynamics, electromyography, and muscle length changes. The subjects were six experienced, male weight lifters. Analyses revealed that the prime movers during ascent were the monoarticular gluteus maximus and vasti muscles (as exemplified by vastus lateralis) and to a lesser extent the soleus muscles. The biarticular muscles functioned mainly as stabilizers of the ankle, knee, and hip joints by working eccentrically to control descent or transferring energy among the segments during scent. During the ascent phase, the hip extensor moments of force produced the largest powers followed by the ankle plantar flexors and then the knee extensors. The hip and knee extensors provided the initial bursts of power during ascent with the ankle extensors and especially a second burst from the hip extensors adding power during the latter half of the ascent.

Muscle function in elite master weightlifters.

PubMed

Pearson, Stephen J; Young, Archie; Macaluso, Andrea; Devito, Giuseppe; Nimmo, Myra A; Cobbold, Matthew; Harridge, Stephen D R

2002-07-01

To determine whether explosive power and isometric strength of the lower-limb muscles in elite master Olympic weightlifters declines at a similar rate to nontrained healthy controls with increasing age. 54 elite level masters weightlifters (aged 40-87), who were competitors at the World Masters Weightlifting Championships (1999), were compared with a similar number of aged-matched, healthy untrained individuals. Isometric knee extensor strength and lower-limb explosive power were tested. Extent of antagonist co-contraction during isometric knee extension was determined by EMG and power loading characteristics by using a variable inertial system. Muscle volume was estimated using anthropometry. On average, the weightlifters were able to generate 32% more peak power (P < 0.05) in the lower limbs and 32% more isometric knee extensor force (P < 0.05) than the control subjects. No significant differences in lower-leg volume were observed between the two groups. Peak power declined at a similar rate with increasing age in the weightlifters and controls (1.2 and 1.3% of a 45-yr-old's value per year), as did strength, but at a lower rate (0.6 and 0.5% per year). The inertial load at which the weightlifters achieved their maximal peak power output was greater (P < 0.05) than the controls. The torque generated at this optimal inertia was also greater in the weightlifters (P < 0.05), whereas the time taken for the weightlifters to reach their maximal peak power was on average 13% shorter (P < 0.05). No differences in antagonist co-contraction during isometric knee extension were observed between the two groups. Muscle power and isometric strength decline at a similar rate with increasing age in elite master weightlifters and healthy controls. In spite of inertial load optimization, muscle power declined in both groups at approximately twice the rate of isometric strength. Although similar rates of decline were observed, the absolute differences between the weightlifters and controls were such that an 85-yr-old weightlifter was as powerful as a 65-yr-old control subject. This would therefore represent an apparent age advantage of approximately 20 yr for the weightlifters.

Age Differences in Dynamic Fatigability and Variability of Arm and Leg Muscles: Associations with Physical Function

PubMed Central

Senefeld, Jonathon; Yoon, Tejin; Hunter, Sandra K.

2016-01-01

Introduction It is not known whether the age-related increase in fatigability of fast dynamic contractions in lower limb muscles also occurs in upper limb muscles. We compared age-related fatigability and variability of maximal-effort repeated dynamic contractions in the knee extensor and elbow flexor muscles; and determined associations between fatigability, variability of velocity between contractions and functional performance. Methods 35 young (16 males; 21.0±2.6 years) and 32 old (18 males; 71.3±6.2 years) adults performed a dynamic fatiguing task involving 90 maximal-effort, fast, concentric, isotonic contractions (1 contraction/3 s) with a load equivalent to 20% maximal voluntary isometric contraction (MVIC) torque with the elbow flexor and knee extensor muscles on separate days. Old adults also performed tests of balance and walking endurance. Results Old adults had greater fatigue-related reductions in peak velocity compared with young adults for both the elbow flexor and knee extensor muscles (P<0.05) with no sex differences (P>0.05). Old adults had greater variability of peak velocity during the knee extensor, but not during the elbow flexor fatiguing task. The age difference in fatigability was greater for the knee extensor muscles (35.9%) compared with elbow flexor muscles (9.7%, P<0.05). Less fatigability of the knee extensor muscles was associated with greater walking endurance (r=−0.34, P=0.048) and balance (r=−0.41, P=0.014) among old adults. Conclusions An age-related increase in fatigability of a dynamic fatiguing task was greater for the knee extensor compared with the elbow flexor muscles in males and females, and greater fatigability was associated with lesser walking endurance and balance. PMID:27989926

Knee Extensor and Flexor Torque Development with Concentric and Eccentric Isokinetic Training

ERIC Educational Resources Information Center

Miller, Larry E.; Pierson, Lee M.; Nickols-Richardson, Sharon M.; Wootten, David F.; Selmon, Serah E.; Ramp, Warren K.; Herbert, William G.

2006-01-01

This study assessed muscular torque and rate of torque development following concentric (CON) or eccentric (ECC) isokinetic training. Thirty-eight women were randomly assigned to either CON or ECC training groups. Training consisted of knee extension and flexion of the nondominant leg three times per week for 20 weeks (SD = 1). Eccentric training…

Measures of Strength and Fitness for Older Populations.

ERIC Educational Resources Information Center

Osness, Wayne H.; Hiebert, Lujean M.

The overall strength of the musculature does not require testing of large numbers of muscle groups and can be accomplished from three or four tests. Small batteries of strength tests have been devised to predict total strength. The best combination of tests for males are thigh flexors, leg extensors, arm flexors, and pectoralis major. The battery…

Soreness-related changes in three-dimensional running biomechanics following eccentric knee extensor exercise.

PubMed

Paquette, Max R; Peel, Shelby A; Schilling, Brian K; Melcher, Dan A; Bloomer, Richard J

2017-06-01

Runners often experience delayed onset muscle soreness (DOMS), especially of the knee extensors, following prolonged running. Sagittal knee joint biomechanics are altered in the presence of knee extensor DOMS but it is unclear how muscle soreness affects lower limb biomechanics in other planes of motion. The purpose of this study was to assess the effects of knee extensor DOMS on three-dimensional (3D) lower limb biomechanics during running. Thirty-three healthy men (25.8 ± 6.8 years; 84.1 ± 9.2 kg; 1.77 ± 0.07 m) completed an isolated eccentric knee extensor damaging protocol to elicit DOMS. Biomechanics of over-ground running at a set speed of 3.35 m s -1 ±5% were measured before eccentric exercise (baseline) and, 24 h and 48 h following exercise in the presence of knee extensor DOMS. Knee flexion ROM was reduced at 48 h (P = 0.01; d = 0.26), and peak knee extensor moment was reduced at 24 h (P = 0.001; d = 0.49) and 48 h (P < 0.001; d = 0.68) compared to baseline. Frontal and transverse plane biomechanics were unaffected by the presence of DOMS (P > 0.05). Peak positive ankle and knee joint powers and, peak negative knee joint power were all reduced from baseline to 24 h and 48 h (P < 0.05). These findings suggest that knee extensor DOMS greatly influences sagittal knee joint angular kinetics and, reduces sagittal power production at the ankle joint. However, knee extensor DOMS does not affect frontal and transverse plane lower limb joint biomechanics during running.

Influences of the extensor portion of the gluteus maximus muscle on pelvic tilt before and after the performance of a fatigue protocol.

PubMed

Alvim, Felipe C; Peixoto, Jennifer G; Vicente, Eduardo J D; Chagas, Paula S C; Fonseca, Diogo S

2010-01-01

There is a lack of data in the literature for determining the influences of the extensor portion of the gluteus maximus muscle on pelvic tilting and, thus, on lumbar stability. To assess the influences of the extensor portion of the gluteus maximus muscle on pelvic tilt. Ten healthy young subjects were recruited, with a body mass index (BMI) below 24.9 kg/m(2) and leg length discrepancy below 1 cm. The BMI, pelvic perimeter and lower-limb lengths were assessed and, subsequently, the degrees of hemi-pelvic tilt and asymmetry between them were analyzed using lateral view photographs of the subjects in a standing position, using SAPO (Software for Postural Assessment). Next, fatigue was induced in the extensor portion of the gluteus maximus muscle on the dominant side, and after that the hemi-pelvic tilt and the asymmetry between the hemi-pelvises were reassessed. The Pearson r and Student t tests were conducted at the significance level of alpha=0.05. There were no significant correlations between the confounding variables and asymmetry of the hemi-pelvic angles. There were significant changes in the hemi-pelvic angle of the dominant side (t=3.760; p=0.004). Fatigue in the extensor portion of the gluteus maximus muscle can generate increases in the tilt angle of the ipsilateral pelvis.

Relationship between isometric thigh muscle strength and minimum clinically important differences in knee function in osteoarthritis: data from the osteoarthritis initiative.

PubMed

Ruhdorfer, Anja; Wirth, Wolfgang; Eckstein, Felix

2015-04-01

To determine the relationship between thigh muscle strength and clinically relevant differences in self-assessed lower leg function. Isometric knee extensor and flexor strength of 4,553 Osteoarthritis Initiative participants (2,651 women and 1,902 men) was related to the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function scores by linear regression. Further, groups of male and female participant strata with minimum clinically important differences (MCIDs) in WOMAC function scores (6 of 68 units) were compared across the full range of observed values and to participants without functional deficits (WOMAC score 0). The effect of WOMAC knee pain and body mass index on the above relationships was explored using stepwise regression. Per regression equations, a 3.7% reduction in extensor strength and a 4.0% reduction in flexor strength were associated with an MCID in WOMAC function in women, and, respectively, a 3.6% and 4.8% reduction in men. For strength divided by body weight, reductions were 5.2% and 6.7%, respectively, in women and 5.8% and 6.7%, respectively, in men. Comparing MCID strata across the full observed range of WOMAC function confirmed the above estimates and did not suggest nonlinear relationships across the spectrum of observed values. WOMAC pain correlated strongly with WOMAC function, but extensor (and flexor) muscle strength contributed significant independent information. Reductions of approximately 4% in isometric muscle strength and of 6% in strength per body weight were related to a clinically relevant difference in WOMAC functional disability. Longitudinal studies will need to confirm these relationships within persons. Muscle extensor (and flexor) strength (per body weight) provided significant independent information in addition to pain in explaining variability in lower leg function. Copyright © 2015 by the American College of Rheumatology.

Reactivity, stability, and strength performance capacity in motor sports.

PubMed

Baur, H; Müller, S; Hirschmüller, A; Huber, G; Mayer, F

2006-11-01

Racing drivers require multifaceted cognitive and physical abilities in a multitasking situation. A knowledge of their physical capacities may help to improve fitness and performance. To compare reaction time, stability performance capacity, and strength performance capacity of élite racing drivers with those of age-matched, physically active controls. Eight élite racing drivers and 10 physically active controls matched for age and weight were tested in a reaction and determination test requiring upper and lower extremity responses to visual and audio cues. Further tests comprised evaluation of one-leg postural stability on a two-dimensional moveable platform, measures of maximum strength performance capacity of the extensors of the leg on a leg press, and a test of force capacity of the arms in a sitting position at a steering wheel. An additional arm endurance test consisted of isometric work at the steering wheel at +30 degrees and -30 degrees where an eccentric threshold load of 30 N.m was applied. Subjects had to hold the end positions above this threshold until exhaustion. Univariate one way analysis of variance (alpha = 0.05) including a Bonferroni adjustment was used to detect group differences between the drivers and controls. The reaction time of the racing drivers was significantly faster than the controls (p = 0.004). The following motor reaction time and reaction times in the multiple determination test did not differ between the groups. No significant differences (p>0.05) were found for postural stability, leg extensor strength, or arm strength and endurance. Racing drivers have faster reaction times than age-matched physically active controls. Further development of motor sport-specific test protocols is suggested. According to the requirements of motor racing, strength and sensorimotor performance capacity can potentially be improved.

Fiber-type distribution in insect leg muscles parallels similarities and differences in the functional role of insect walking legs.

PubMed

Godlewska-Hammel, Elzbieta; Büschges, Ansgar; Gruhn, Matthias

2017-10-01

Previous studies have demonstrated that myofibrillar ATPase (mATPase) enzyme activity in muscle fibers determines their contraction properties. We analyzed mATPase activities in muscles of the front, middle and hind legs of the orthopteran stick insect (Carausius morosus) to test the hypothesis that differences in muscle fiber types and distributions reflected differences in their behavioral functions. Our data show that all muscles are composed of at least three fiber types, fast, intermediate and slow, and demonstrate that: (1) in the femoral muscles (extensor and flexor tibiae) of all legs, the number of fast fibers decreases from proximal to distal, with a concomitant increase in the number of slow fibers. (2) The swing phase muscles protractor coxae and levator trochanteris, have smaller percentages of slow fibers compared to the antagonist stance muscles retractor coxae and depressor trochanteris. (3) The percentage of slow fibers in the retractor coxae and depressor trochanteris increases significantly from front to hind legs. These results suggest that fiber-type distribution in leg muscles of insects is not identical across leg muscles but tuned towards the specific function of a given muscle in the locomotor system.

Optimisation of sprinting performance in running, cycling and speed skating.

PubMed

van Ingen Schenau, G J; de Koning, J J; de Groot, G

1994-04-01

Sprinting performances rely strongly on a fast acceleration at the start of a sprint and on the capacity to maintain a high velocity in the phase following the start. Simulations based on a model developed in which the generation of metabolic power is related to the mechanical destinations of power showed that for short-lasting sprinting events, the best pacing strategy is an all out effort, even if this strategy causes a strong reduction of the velocity at the end of the race. Even pacing strategies should only be used in exercises lasting longer than 80 to 100 seconds. Sprint runners, speed skaters and cyclists need a large rate of breakdown of energy rich phosphates in the first 4 to 5 seconds of the race (mechanical equivalent > 20 W/kg) in order to accelerate their body, and a power output of more than 10 W/kg in the phase following the start to maintain a high velocity. Maximal speed in running is mainly limited by the necessity to rotate the legs forwards and backwards relative to the hip joint. The acceleration phase, however, relies on powerful extensions of all leg joints. Through a comparison of the hindlimb design of highly specialised animal sprinters (as can be found among predators) and of long distance animal runners (as found among hoofed animals), it is illustrated that these 2 phases of a sprint rely on conflicting requirements: improvement of maximal speed would require lower moments of inertia of the legs whereas a faster acceleration would require the involvement of more muscle mass (not only of the hip and knee extensors but also of the plantar flexors). Maximal speed in cycling and speed skating is not limited by the necessity to move leg segments but rather on air friction and rolling or ice friction. Since the drag coefficients found for speed skaters and cyclists (about 0.8) are considerably higher than those of more streamlined bodies, much progress can still be expected from the reduction of air friction. Speed skaters and especially cyclists show much smaller accelerations during the start than do sprint runners. Skaters might try to improve their very first push off by developing a start technique that allows a much more horizontally directed propulsive force. The small propulsive force at the onset of a cycling sprint is due to the gearing system.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of Balance Training on Postural Sway, Leg Extensor Strength, and Jumping Height in Adolescents

ERIC Educational Resources Information Center

Granacher, Urs; Gollhofer, Albert; Kriemler, Susi

2010-01-01

Deficits in strength of the lower extremities and postural control have been associated with a high risk of sustaining sport-related injuries. Such injuries often occur during physical education (PE) classes and mostly affect the lower extremities. Thus, the objectives of this study were to investigate the effects of balance training on postural…

Back Strength Predicts Walking Improvement in Obese, Older Adults With Chronic Low Back Pain

PubMed Central

Vincent, Heather K.; Vincent, Kevin R.; Seay, Amanda N.; Conrad, Bryan P.; Hurley, Robert W.; George, Steven Z.

2014-01-01

Objective To compare the effects of 4 months of isolated lumbar resistance exercise and total body resistance exercise on walking performance in obese, older adults with chronic low back pain. A secondary analysis examined whether responsiveness to training modulated walking improvement. Design Randomized, controlled trial. Setting Research laboratory affiliated with tertiary care facility. Methods and Intervention Participants (N = 49; 60–85 years) were randomized into a 4-month resistance exercise intervention (TOTRX), lumbar extensor exercise intervention (LEXT), or a control group (CON). Main Outcome Measurements Walking performance, maximal low back strength and leg strength, and average resting and low back pain severity score (from an 11-point numerical pain rating scale; NRSpain) were collected at baseline and month 4. Results The TOTRX and LEXT improved lumbar extensor strength relative to CON and the TOTRX (P < .05). NRSpain scores at month 4 were lowest in the TOTRX group compared with the LEXT and CON groups, respectively (2.0 ± 1.7 points vs 3.7 ± 2.6 points and 4.6 ± 2.4 points; P < .006). A total of 53% and 67% of participants in the TOTRX and LEXT groups were responders who made lumbar extensor strength gains that achieved ≥20% greater than baseline values. Although the TOTRX demonstrated the greatest improvement in walking endurance among the intervention groups, this did not reach significance (10.1 ± 12.2% improvement in TOTRX vs 7.4 ± 30.0% LEXT and −1.7 ± 17.4% CON; P = .11). Gait speed increased most in the TOTRX (9.0 ± 13.5%) compared with the LEXT and CON groups (P < .05). The change in lumbar extensor strength explained 10.6% of the variance of the regression model for the change in walking endurance (P = .024). Conclusions The use of LEXT and TOTRX produced similar modest improvements in patients’ walking endurance. Lumbar extensor strength gain compared with leg strength gain is a moderate but important contributor to walking endurance in obese older adults with chronic low back pain. Responders to resistance exercise programs (event those with only lumbar extension exercise) who make at least a 20% improvement in strength can expect better improvement in walking endurance than those who do not achieve this strength improvement. PMID:24211698

Neuromuscular plasticity in the locust after permanent removal of an excitatory motoneuron of the extensor tibiae muscle.

PubMed

Büschges, A; Djokaj, S; Bässler, D; Bässler, U; Rathmayer, W

2000-01-01

The capacity of the larval insect nervous system to compensate for the permanent loss of one of the two excitatory motoneurons innervating a leg muscle was investigated in the locust (Locusta migratoria). In the fourth instar, the fast extensor tibiae (FETi) motoneuron in the mesothoracic ganglion was permanently removed by photoinactivation with a helium-cadmium laser. Subsequently, the animals were allowed to develop into adulthood. When experimental animals were tested as adults after final ecdysis, fast-contracting fibers in the most proximal region of the corresponding extensor muscle, which are normally predominantly innervated by FETi only, uniformly responded to activity of the slow extensor tibiae (SETi) neuron. In adult operated animals, single pulses to SETi elicited large junctional responses in the fibers which resulted in twitch contractions of these fibers similar to the responses to FETi activity in control animals. The total number of muscle fibers, their properties as histochemically determined contractional types (fast and slow), and their distribution were not affected by photoinactivation of FETi. Possible mechanisms enabling the larval neuromuscular system to compensate for the loss of FETi through functionally similar innervation by a different motoneuron, i.e. SETi, are discussed. Copyright 2000 John Wiley & Sons, Inc.

Characterizing rapid-onset vasodilation to single muscle contractions in the human leg

PubMed Central

Credeur, Daniel P.; Holwerda, Seth W.; Restaino, Robert M.; King, Phillip M.; Crutcher, Kiera L.; Laughlin, M. Harold; Padilla, Jaume

2014-01-01

Rapid-onset vasodilation (ROV) following single muscle contractions has been examined in the forearm of humans, but has not yet been characterized in the leg. Given known vascular differences between the arm and leg, we sought to characterize ROV following single muscle contractions in the leg. Sixteen healthy men performed random ordered single contractions at 5, 10, 20, 40, and 60% of their maximum voluntary contraction (MVC) using isometric knee extension made with the leg above and below heart level, and these were compared with single isometric contractions of the forearm (handgrip). Single thigh cuff compressions (300 mmHg) were utilized to estimate the mechanical contribution to leg ROV. Continuous blood flow was determined by duplex-Doppler ultrasound and blood pressure via finger photoplethysmography (Finometer). Single isometric knee extensor contractions produced intensity-dependent increases in peak leg vascular conductance that were significantly greater than the forearm in both the above- and below-heart level positions (e.g., above heart level: leg 20% MVC, +138 ± 28% vs. arm 20% MVC, +89 ± 17%; P < 0.05). Thigh cuff compressions also produced a significant hyperemic response, but these were brief and smaller in magnitude compared with single isometric contractions in the leg. Collectively, these data demonstrate the presence of a rapid and robust vasodilation to single muscle contractions in the leg that is largely independent of mechanical factors, thus establishing the leg as a viable model to study ROV in humans. PMID:25539935

Atorvastatin Increases Exercise Leg Blood Flow in Healthy Adults

PubMed Central

Parker, Beth A.; Capizzi, Jeffrey A.; Augeri, Amanda L.; Grimaldi, Adam S.; White, C. Michael; Thompson, Paul D.

2011-01-01

OBJECTIVES We sought to examine the effect of atorvastatin therapy on exercise leg blood flow in healthy middle-aged and older, men and women. BACKGROUND The vasodilatory response to exercise decreases in humans with aging and disease and this reduction may contribute to reduced exercise capacity. METHODS We used a double-blind, randomly assigned, placebo-controlled protocol to assess the effect of atorvastatin treatment on exercising leg hemodynamics. We measured femoral artery blood flow (FBF) using Doppler ultrasound and calculated femoral vascular conductance (FVC) from brachial mean arterial pressure (MAP) before and during single knee-extensor exercise in healthy adults (ages 40–71) before (PRE) and after (POST) 6 months of 80 mg atorvastatin (A: 14 men, 16 women) or placebo (P: 14 men, 22 women) treatment. FBF and FVC were normalized to exercise power output and estimated quadriceps muscle mass. RESULTS Atorvastatin reduced LDL cholesterol by approximately 50%, but not in the placebo group (p < 0.01). Atorvastatin also increased exercise FBF from 44.2 ± 19.0 to 51.4 ± 22.0 mL/min/W/kg muscle whereas FBF in the placebo group was unchanged (40.1 ± 16.0 vs 39.5 ± 16.1) (p <0.01). FVC also increased with atorvastatin from 0.5 ± 0.2 to. 0.6 ± 0.2 mL/min/mmHg/W/kg muscle, but not in the placebo subjects (P: 0.4 ± 0.2 vs 0.4 ± 0.2) ( p < 0.01). CONCLUSIONS High-dose atorvastatin augments exercising leg hyperemia. Statins may mitigate reductions in the exercise vasodilatory response in humans that are associated with aging and disease. PMID:22018642

Physiological and anthropometric characteristics of starters and non-starters and playing positions in elite Australian Rules Football: a case study.

PubMed

Young, W B; Newton, R U; Doyle, T L A; Chapman, D; Cormack, S; Stewart, G; Dawson, B

2005-09-01

A purpose of this study was to determine if pre-season anthropometric and physiological measures were significantly different for the players from one Australian Football League (AFL) club selected to play in the first game of the season compared to the players not selected. Another purpose was to compare fitness test results for defenders, forwards and mid-fielders in the same AFL club. Thirty-four players were tested for isolated quadriceps and hamstrings strength, leg extensor muscle strength and power, upper body strength, sprinting speed, vertical jump (VJ), endurance, skinfolds and hamstring flexibility. The starters who were selected to play the first game were a significantly older and more experienced playing group, and were significantly better (p < 0.05) in measures of leg power, sprinting speed and the distance covered in the Yo Yo intermittent recovery test compared to the non-starters. Although there were trends for the superiority of the starters, the differences in lower and upper body strength, VJ and predicted VO2max were non-significant. The forwards generally produced the worst fitness scores of the playing positions with the midfielders having significantly lower skinfolds and the defenders possessing better hamstring strength and VJ compared to the forwards. It was concluded that some fitness qualities can differentiate between starters and non-starters, at least in one AFL club. Comparisons of playing positions and the development of fitness norms for AFL players require further research.

Lean muscle volume of the thigh has a stronger relationship with muscle power than muscle strength in women with knee osteoarthritis.

PubMed

Davison, Michael J; Maly, Monica R; Keir, Peter J; Hapuhennedige, Sandani M; Kron, Amie T; Adachi, Jonathan D; Beattie, Karen A

2017-01-01

Thigh lean muscle and intramuscular fat have been implicated in the impairment of physical function observed in people with knee osteoarthritis. We investigated the relationships of quadriceps and hamstrings intramuscular fat fraction and lean muscle volume with muscle power and strength, controlling for neuromuscular activation, and physical performance in women with knee OA. Women (n=20) 55years or older with symptomatic, radiographic knee osteoarthritis underwent a 3.0T magnetic resonance imaging scan of the thigh of their most symptomatic knee. Axial fat-separated images were analyzed using software to quantify intramuscular fat and lean muscle volumes of the quadriceps and hamstrings. To quantify strength and power of the knee extensors and flexors, participants performed maximum voluntary isometric contraction and isotonic knee extensions and flexions, respectively. Electromyography of the quadriceps and hamstrings was measured. Participants also completed five physical performance tests. Quadriceps and hamstrings lean muscle volumes were related to isotonic knee extensor (B=0.624; p=0.017) and flexor (B=1.518; p=0.032) power, but not knee extensor (B=0.001; p=0.615) or flexor (B=0.001; p=0.564) isometric strength. Intramuscular fat fractions were not related to isotonic knee extensor or flexor power, nor isometric strength. No relationships were found between intramuscular fat or lean muscle volume and physical performance. Muscle power may be more sensitive than strength to lean muscle mass in women with knee osteoarthritis. Thigh lean muscle mass, but neither intramuscular nor intermuscular fat, is related to knee extensor and flexor power in women with knee osteoarthritis. Copyright © 2016 Elsevier Ltd. All rights reserved.

Quadriceps Strength in Patients With Isolated Cartilage Defects of the Knee: Results of Isokinetic Strength Measurements and Their Correlation With Clinical and Functional Results

PubMed Central

Hirschmüller, Anja; Andres, Tasja; Schoch, Wolfgang; Baur, Heiner; Konstantinidis, Lukas; Südkamp, Norbert P.; Niemeyer, Philipp

2017-01-01

Background: Recent studies have found a significant deficit of maximum quadriceps strength after autologous chondrocyte implantation (ACI) of the knee. However, it is unclear whether muscular strength deficits in patients with cartilage damage exist prior to operative treatment. Purpose: To isokinetically test maximum quadriceps muscle strength and quantify the impact of possible strength deficits on functional and clinical test results. Study Design: Cross-sectional study; Level of evidence, 3. Methods: To identify clinically relevant muscular strength deficits, 24 patients (5 females, 19 males; mean age, 34.5 years; body mass index, 25.9 kg/m2) with isolated cartilage defects (mean onset, 5.05 years; SD, 7.8 years) in the knee joint underwent isokinetic strength measurements. Maximal quadriceps strength was recorded in 3 different testing modes: pure concentric contraction (flexors and extensors alternating work; con1), concentric-eccentric (only the extensors work concentrically and eccentrically; con2), and eccentric contraction in the alternating mode (ecc). Results were compared for functional performance (single-leg hop test), pain scales (visual analog scale [VAS], numeric rating scale [NRS]), self-reported questionnaires (International Knee Documentation Committee [IKDC], Knee Injury and Osteoarthritis Outcome Scale [KOOS]), and defect size (cm2). Results: Compared with the uninjured leg, significantly lower quadriceps strength was detected in the injured leg in all isokinetic working modes (con1 difference, 27.76 N·m [SD 17.47; P = .003]; con2 difference, 21.45 N·m [SD, 18.45; P =.025]; ecc difference, 29.48 N·m [SD, 21.51; P = .001]), with the largest deficits found for eccentric muscle performance. Moderate negative correlations were observed for the subjective pain scales NRS and VAS. The results of the IKDC and KOOS questionnaires showed low, nonsignificant correlations with findings in the isokinetic measurement. Moreover, defect sizes (mean, 3.13 cm2) were of no importance regarding the prediction of the strength deficit. The quadriceps strength deficit between the injured and the uninjured leg was best predicted by the results of the single-leg hop test. Conclusion: Patients with isolated cartilage defects of the knee joint have significant deficits in quadriceps muscle strength of the injured leg compared with the uninjured leg. The single-leg hop test may be used to predict quadriceps strength deficits. Future research should address whether preoperative strength training in patients with cartilage defects of the knee could be effective and should be taken into consideration in addition to surgical treatment. PMID:28596973

Octopamine mediated relaxation of maintained and catch tension in locust skeletal muscle.

PubMed

Evans, P D; Siegler, M V

1982-03-01

1. The modulatory actions of an identified octopaminergic neurone (DUMETi) that projects to the extensor-tibiae muscle of the locust hind leg depend upon the frequency of stimulation of the slow motoneurone (SETi) to this muscle. 2. At low frequencies of SETi stimulation (1Hz and below) the predominant modulatory effects are increases in the amplitude and relaxation rate of twitch tension. At higher frequencies, where twitches summate but tetanus is incomplete (up to 20 Hz), the reduction of maintained tension becomes considerably more important. 3. Both octopamine application and DUMETi stimulation reduce the amount of catch tension displayed by the extensor muscle when SETi is fired in a variety of different stimulus patterns. The extensor-tibiae muscle is itself 'pattern sensitive' since is shows a 'positive spacing effect' when SETi is stimulated at an average frequency of 1 Hz. 4. It is suggested that a primary function of DUMETi is to change the response of the muscle from one that favours maintenance of posture to one that favours rapid changes in joint position or force, such as might occur during locomotion.

Octopamine mediated relaxation of maintained and catch tension in locust skeletal muscle.

PubMed Central

Evans, P D; Siegler, M V

1982-01-01

1. The modulatory actions of an identified octopaminergic neurone (DUMETi) that projects to the extensor-tibiae muscle of the locust hind leg depend upon the frequency of stimulation of the slow motoneurone (SETi) to this muscle. 2. At low frequencies of SETi stimulation (1Hz and below) the predominant modulatory effects are increases in the amplitude and relaxation rate of twitch tension. At higher frequencies, where twitches summate but tetanus is incomplete (up to 20 Hz), the reduction of maintained tension becomes considerably more important. 3. Both octopamine application and DUMETi stimulation reduce the amount of catch tension displayed by the extensor muscle when SETi is fired in a variety of different stimulus patterns. The extensor-tibiae muscle is itself 'pattern sensitive' since is shows a 'positive spacing effect' when SETi is stimulated at an average frequency of 1 Hz. 4. It is suggested that a primary function of DUMETi is to change the response of the muscle from one that favours maintenance of posture to one that favours rapid changes in joint position or force, such as might occur during locomotion. PMID:6808122

Factors predicting dynamic balance and quality of life in home-dwelling elderly women.

PubMed

Karinkanta, S; Heinonen, A; Sievanen, H; Uusi-Rasi, K; Kannus, P

2005-01-01

Proper balance seems to be a critical factor in terms of fall prevention among the elderly. The purpose of this cross-sectional study was to examine factors that are associated with dynamic balance and health-related quality of life in home-dwelling elderly women. One hundred and fifty-three healthy postmenopausal women (mean age: 72 years, height: 159 cm, weight: 72 kg) were examined. General health and physical activity were assessed by a questionnaire. Quality of life was measured using a health-related quality of life questionnaire (Rand 36-Item Health Survey 1.0). Dynamic balance (agility) was tested by a figure-of-eight running test. Static balance (postural sway) was tested on an unstable platform. Maximal isometric strength of the leg extensors was measured with a leg press dynamometer. Dynamic muscle strength of lower limbs was tested by measuring ground reaction forces with a force platform during common daily activities (sit-to-stand and step-on-a-stair tests). Concerning physical activity, 33% of the subjects reported brisk exercise (walking, Nordic walking, cross-country skiing, swimming and aquatic exercises) at least twice a week, and 22% some kind of brisk activity once a week in addition to lighter physical exercise. The remaining 45% did not exercise regularly and were classified as sedentary. The correlations of step-on-a-stair and sit-to-stand ground reaction forces, and leg extensor strength to dynamic balance were from -0.32 to -0.43 (the better the strength, the better the balance). In the regression analysis with backward elimination, step-on-a-stair and sit-to-stand ground reaction forces, and leg extensor strength, age, brisk physical activity, number of diseases and dynamic postural stability explained 42% of the variance in the dynamic balance. Similarly, dynamic balance (figure-of-eight running time), number of diseases and walking more than 3 km per day explained 14% of the variance in the quality of life score. Of these, figure-of-eight running time was the strongest predictor of the quality of life score, explaining 9% of its variance. This study emphasizes the concept that in home-dwelling elderly women good muscle strength in lower limbs is crucial for proper body balance and that dynamic balance is an independent predictor of a standardized quality of life estimate. The results provide important and useful information when planning meaningful contents for studies related to fall prevention and quality of life and interventions in elderly women. Copyright (c) 2005 S. Karger AG, Basel.

Effects of fatiguing constant versus alternating intensity intermittent isometric muscle actions on maximal torque and neuromuscular responses

PubMed Central

Smith, C.M.; Housh, T.J.; Hill, E.C.; Cochrane, K.C.; Jenkins, N.D.M.; Schmidt, R.J.; Johnson, G.O.

2016-01-01

Objective: To determine the effects of constant versus alternating applications of torque during fatiguing, intermittent isometric muscle actions of the leg extensors on maximal voluntary isometric contraction (MVIC) torque and neuromuscular responses. Methods: Sixteen subjects performed two protocols, each consisting of 50 intermittent isometric muscle actions of the leg extensors with equal average load at a constant 60% MVIC or alternating 40 then 80% (40/80%) MVIC with a work-to-rest ratio of 6-s on and 2-s off. MVIC torque as well as electromyographic signals from the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) and mechanomyographic signals from the VL were recorded pretest, immediately posttest, and 5-min posttest. Results: The results indicated that there were no time-related differences between the 60% MVIC and 40/80% MVIC protocols. The MVIC torque decreased posttest (22 to 26%) and remained depressed 5-min posttest (9%). There were decreases in electromyographic frequency (14 to 19%) and mechanomyographic frequency (23 to 24%) posttest that returned to pretest levels 5-min posttest. There were no changes in electromyographic amplitude and mechanomyogrpahic amplitude. Conclusions: These findings suggested that these neuromuscular parameters did not track the fatigue-induced changes in MVIC torque after 5-min of recovery. PMID:27973384

Relationship between strength qualities and short track speed skating performance in young athletes.

PubMed

Felser, S; Behrens, M; Fischer, S; Heise, S; Bäumler, M; Salomon, R; Bruhn, S

2016-02-01

This study analyzed the relationships between isometric as well as concentric maximum voluntary contraction (MVC) strength of the leg muscles and the times as well as speeds over different distances in 17 young short track speed skaters. Isometric as well as concentric single-joint MVC strength and multi-joint MVC strength in a stable (without skates) and unstable (with skates) condition were tested. Furthermore, time during maximum skating performances on ice was measured. Results indicate that maximum torques during eversion and dorsal flexion have a significant influence on skating speed. Concentric MVC strength of the knee extensors was higher correlated with times as well as speeds over the different distances than isometric MVC strength. Multi-joint MVC testing revealed that the force loss between measurements without and with skates amounts to 25%, while biceps femoris and soleus showed decreased muscle activity and peroneus longus, tibialis anterior, as well as rectus femoris exhibited increased muscle activity. The results of this study depict evidence that the skating times and speeds are primarily influenced by concentric MVC strength of the leg extensors. To be able to transfer the strength onto ice in an optimal way, it is necessary to stabilize the knee and ankle joints. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Effects of the innervation zone on the time and frequency domain parameters of the surface electromyographic signal.

PubMed

Smith, Cory M; Housh, Terry J; Herda, Trent J; Zuniga, Jorge M; Ryan, Eric D; Camic, Clayton L; Bergstrom, Haley C; Smith, Doug B; Weir, Joseph P; Cramer, Joel T; Hill, Ethan C; Cochrane, Kristen C; Jenkins, Nathaniel D M; Schmidt, Richard J; Johnson, Glen O

2015-08-01

The purposes of the present study were to examine the effects of electrode placements over, proximal, and distal to the innervation zone (IZ) on electromyographic (EMG) amplitude (RMS) and frequency (MPF) responses during: (1) a maximal voluntary isometric contraction (MVIC), and; (2) a sustained, submaximal isometric muscle action. A linear array was used to record EMG signals from the vastus lateralis over the IZ, 30mm proximal, and 30mm distal to the IZ during an MVIC and a sustained isometric muscle action of the leg extensors at 50% MVIC. During the MVIC, lower EMG RMS (p>0.05) and greater EMG MPF (p<0.05) values were recorded over the IZ compared to away from the IZ, however, no differences in slope coefficients for the EMG RMS and MPF versus time relationships over, proximal, and distal to the IZ occurred. Thus, the results of the present study indicated that during an MVIC, EMG RMS and MPF values recorded over the IZ are not comparable to those away from the IZ. However, the rates of fatigue-induced changes in EMG RMS and MPF during sustained, submaximal isometric muscle actions of the leg extensors were the same regardless of the electrode placement locations relative to the IZ. Copyright © 2015 Elsevier Ltd. All rights reserved.

The effects of resisted sprint training on acceleration performance and kinematics in soccer, rugby union, and Australian football players.

PubMed

Spinks, Christopher D; Murphy, Aron J; Spinks, Warwick L; Lockie, Robert G

2007-02-01

Acceleration is a significant feature of game-deciding situations in the various codes of football. However little is known about the acceleration characteristics of football players, the effects of acceleration training, or the effectiveness of different training modalities. This study examined the effects of resisted sprint (RS) training (weighted sled towing) on acceleration performance (0-15 m), leg power (countermovement jump [CMJ], 5-bound test [5BT], and 50-cm drop jump [50DJ]), gait (foot contact time, stride length, stride frequency, step length, and flight time), and joint (shoulder, elbow, hip, and knee) kinematics in men (N = 30) currently playing soccer, rugby union, or Australian football. Gait and kinematic measurements were derived from the first and second strides of an acceleration effort. Participants were randomly assigned to 1 of 3 treatment conditions: (a) 8-week sprint training of two 1-h sessions x wk(-1) plus RS training (RS group, n = 10), (b) 8-week nonresisted sprint training program of two 1-h sessions x wk(-1) (NRS group, n = 10), or (c) control (n = 10). The results indicated that an 8-week RS training program (a) significantly improves acceleration and leg power (CMJ and 5BT) performance but is no more effective than an 8-week NRS training program, (b) significantly improves reactive strength (50DJ), and (c) has minimal impact on gait and upper- and lower-body kinematics during acceleration performance compared to an 8-week NRS training program. These findings suggest that RS training will not adversely affect acceleration kinematics and gait. Although apparently no more effective than NRS training, this training modality provides an overload stimulus to acceleration mechanics and recruitment of the hip and knee extensors, resulting in greater application of horizontal power.

Effects of Heavy-Resistance Strength and Balance Training on Unilateral and Bilateral Leg Strength Performance in Old Adults

PubMed Central

Beurskens, Rainer; Gollhofer, Albert; Muehlbauer, Thomas; Cardinale, Marco; Granacher, Urs

2015-01-01

The term “bilateral deficit” (BLD) has been used to describe a reduction in performance during bilateral contractions when compared to the sum of identical unilateral contractions. In old age, maximal isometric force production (MIF) decreases and BLD increases indicating the need for training interventions to mitigate this impact in seniors. In a cross-sectional approach, we examined age-related differences in MIF and BLD in young (age: 20–30 years) and old adults (age: >65 years). In addition, a randomized-controlled trial was conducted to investigate training-specific effects of resistance vs. balance training on MIF and BLD of the leg extensors in old adults. Subjects were randomly assigned to resistance training (n = 19), balance training (n = 14), or a control group (n = 20). Bilateral heavy-resistance training for the lower extremities was performed for 13 weeks (3 × / week) at 80% of the one repetition maximum. Balance training was conducted using predominately unilateral exercises on wobble boards, soft mats, and uneven surfaces for the same duration. Pre- and post-tests included uni- and bilateral measurements of maximal isometric leg extension force. At baseline, young subjects outperformed older adults in uni- and bilateral MIF (all p < .001; d = 2.61–3.37) and in measures of BLD (p < .001; d = 2.04). We also found significant increases in uni- and bilateral MIF after resistance training (all p < .001, d = 1.8-5.7) and balance training (all p < .05, d = 1.3-3.2). In addition, BLD decreased following resistance (p < .001, d = 3.4) and balance training (p < .001, d = 2.6). It can be concluded that both training regimens resulted in increased MIF and decreased BLD of the leg extensors (HRT-group more than BAL-group), almost reaching the levels of young adults. PMID:25695770

Per meal dose and frequency of protein consumption is associated with lean mass and muscle performance.

PubMed

Loenneke, Jeremy P; Loprinzi, Paul D; Murphy, Caoileann H; Phillips, Stuart M

2016-12-01

It has been hypothesized that for older adults evenly distributing consumption of protein at 30-40 g per meal throughout the day may result in more favorable retention of lean mass and muscular strength. Such a thesis has not, to our knowledge, been tested outside of short-term studies or acute measures of muscle protein synthesis. To examine whether the number of times an individual consumed a minimum of 30 g of protein at a meal is associated with leg lean mass and knee extensor strength. Data from the 1999-2002 NHANES were used, with 1081 adults (50-85 y) constituting the analytic sample. A "multiple pass" 24-h dietary interview format was used to collect detailed information about the participants' dietary intake. Knee extensor strength was assessed objectively using the Kin Com MP dynamometer. Leg lean mass was estimated from whole-body dual-energy X-ray absorptiometry (DXA) scans. Participants with 1 vs. 0 (β adjusted  = 23.6, p = 0.002) and 2 vs. 0 (β adjusted  = 51.1, p = 0.001) meals of ≥30 g protein/meal had greater strength and leg lean mass (1 vs. 0, β adjusted  = 1160, p < 0.05 and 2 vs. 0, β adjusted  = 2389, p < 0.05). The association of protein frequency with leg lean mass and strength plateaued at ∼45 g protein/meal for those consuming 2 vs. 0 meals above the evaluated protein/meal threshold. However, for those with only 1 meal at or above the evaluated threshold, the response plateaued at 30 g/meal. Leg lean mass mediated the relationship between protein frequency and strength, with the proportion of the total effect mediated being 64%. We found that more frequent consumption of meals containing between 30 and 45 g protein/meal produced the greatest association with leg lean mass and strength. Thus, the consumption of 1-2 daily meals with protein content from 30 to 45 g may be an important strategy for increasing and/or maintaining lean body mass and muscle strength with aging. Copyright © 2016 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

Effects of neck and circumoesophageal connective lesions on posture and locomotion in the cockroach.

PubMed

Ridgel, Angela L; Ritzmann, Roy E

2005-06-01

Few studies in arthropods have documented to what extent local control centers in the thorax can support locomotion in absence of inputs from head ganglia. Posture, walking, and leg motor activity was examined in cockroaches with lesions of neck or circumoesophageal connectives. Early in recovery, cockroaches with neck lesions had hyper-extended postures and did not walk. After recovery, posture was less hyper-extended and animals initiated slow leg movements for multiple cycles. Neck lesioned individuals showed an increase in walking after injection of either octopamine or pilocarpine. The phase of leg movement between segments was reduced in neck lesioned cockroaches from that seen in intact animals, while phases in the same segment remained constant. Neither octopamine nor pilocarpine initiated changes in coordination between segments in neck lesioned individuals. Animals with lesions of the circumoesophageal connectives had postures similar to intact individuals but walked in a tripod gait for extended periods of time. Changes in activity of slow tibial extensor and coxal depressor motor neurons and concomitant changes in leg joint angles were present after the lesions. This suggests that thoracic circuits are sufficient to produce leg movements but coordinated walking with normal motor patterns requires descending input from head ganglia.

An investigation of leg and trunk strength and reaction times of hard-style martial arts practitioners.

PubMed

Donovan, Oliver O; Cheung, Jeanette; Catley, Maria; McGregor, Alison H; Strutton, Paul H

2006-01-01

The purpose of this study was to investigate trunk and knee strength in practitioners of hard-style martial arts. An additional objective was to examine reaction times in these participants by measuring simple reaction times (SRT), choice reaction times (CRT) and movement times (MT). Thirteen high-level martial artists and twelve sedentary participants were tested under isokinetic and isometric conditions on an isokinetic dynamometer. Response and movement times were also measured in response to simple and choice auditory cues. Results indicated that the martial arts group generated a greater body-weight adjusted peak torque with both legs at all speeds during isokinetic extension and flexion, and in isometric extension but not flexion. In isokinetic and isometric trunk flexion and extension, martial artists tended to have higher peak torques than controls, but they were not significantly different (p > 0.05). During the SRT and CRT tasks the martial artists were no quicker in lifting their hand off a button in response to the stimulus [reaction time (RT)] but were significantly faster in moving to press another button [movement time (MT)]. In conclusion, the results reveal that training in a martial art increases the strength of both the flexors and extensors of the leg. Furthermore, they have faster movement times to auditory stimuli. These results are consistent with the physical aspects of the martial arts. Key PointsMartial artists undertaking hard-style martial arts have greater strength in their knee flexor and extensor muscles as tested under isokinetic testing. Under isometric testing conditions they have stronger knee extensors only.The trunk musculature is generally higher under both conditions of testing in the martial artists, although not significantly.The total reaction times of the martial artists to an auditory stimulus were significantly faster than the control participants. When analysed further it was revealed that the decrease in reaction time was due to the movement time component of the total reaction time.The training involved for the practice of the hard-style martial arts increases the strength of muscles involved in kicking. This increased strength is not seen in the trunk muscles. Furthermore, martial artists have a faster response time; the cause of which appears to be only the faster movement time.

An Investigation Of Leg And Trunk Strength And Reaction Times Of Hard-Style Martial Arts Practitioners

PubMed Central

Donovan, Oliver O; Cheung, Jeanette; Catley, Maria; McGregor, Alison H.; Strutton, Paul H.

2006-01-01

The purpose of this study was to investigate trunk and knee strength in practitioners of hard-style martial arts. An additional objective was to examine reaction times in these participants by measuring simple reaction times (SRT), choice reaction times (CRT) and movement times (MT). Thirteen high-level martial artists and twelve sedentary participants were tested under isokinetic and isometric conditions on an isokinetic dynamometer. Response and movement times were also measured in response to simple and choice auditory cues. Results indicated that the martial arts group generated a greater body-weight adjusted peak torque with both legs at all speeds during isokinetic extension and flexion, and in isometric extension but not flexion. In isokinetic and isometric trunk flexion and extension, martial artists tended to have higher peak torques than controls, but they were not significantly different (p > 0.05). During the SRT and CRT tasks the martial artists were no quicker in lifting their hand off a button in response to the stimulus [reaction time (RT)] but were significantly faster in moving to press another button [movement time (MT)]. In conclusion, the results reveal that training in a martial art increases the strength of both the flexors and extensors of the leg. Furthermore, they have faster movement times to auditory stimuli. These results are consistent with the physical aspects of the martial arts. Key Points Martial artists undertaking hard-style martial arts have greater strength in their knee flexor and extensor muscles as tested under isokinetic testing. Under isometric testing conditions they have stronger knee extensors only. The trunk musculature is generally higher under both conditions of testing in the martial artists, although not significantly. The total reaction times of the martial artists to an auditory stimulus were significantly faster than the control participants. When analysed further it was revealed that the decrease in reaction time was due to the movement time component of the total reaction time. The training involved for the practice of the hard-style martial arts increases the strength of muscles involved in kicking. This increased strength is not seen in the trunk muscles. Furthermore, martial artists have a faster response time; the cause of which appears to be only the faster movement time. PMID:24376366

Two families with MYH7 distal myopathy associated with cardiomyopathy and core formations.

PubMed

Naddaf, Elie; Waclawik, Andrew J

2015-03-01

Laing distal myopathy is caused by MYH7 gene mutations. Multiple families have been reported with varying patterns of skeletal and cardiac involvement as well as histopathological findings. We report 2 families with p.Glu1508del mutation with detailed electrophysiological and muscle pathology findings. All patients displayed the classic phenotype with weakness starting in the anterior compartment of the legs with a "hanging great toe." It was followed by finger extensors involvement, relatively sparing the extensor indicis proprius, giving the appearance of a "pointing index" finger. All the affected individuals had a dilated cardiomyopathy and core formations on muscle biopsy. Unexpectedly, neurogenic changes were also observed in some individuals. Both families were initially misdiagnosed with either central core disease or hereditary neuropathy. Recognizing the classic phenotype, screening for cardiac involvement that may be clinically silent, and determining the mode of inheritance help with selecting the appropriate genetic test.

Body weight-supported training in Becker and limb girdle 2I muscular dystrophy.

PubMed

Jensen, Bente R; Berthelsen, Martin P; Husu, Edith; Christensen, Sofie B; Prahm, Kira P; Vissing, John

2016-08-01

We studied the functional effects of combined strength and aerobic anti-gravity training in severely affected patients with Becker and Limb-Girdle muscular dystrophies. Eight patients performed 10-week progressive combined strength (squats, calf raises, lunges) and aerobic (walk/run, jogging in place or high knee-lift) training 3 times/week in a lower-body positive pressure environment. Closed-kinetic-chain leg muscle strength, isometric knee strength, rate of force development (RFD), and reaction time were evaluated. Baseline data indicated an intact neural activation pattern but showed compromised muscle contractile properties. Training (compliance 91%) improved functional leg muscle strength. Squat series performance increased 30%, calf raises 45%, and lunges 23%. Anti-gravity training improved closed-kinetic-chain leg muscle strength despite no changes in isometric knee extension strength and absolute RFD. The improved closed-kinetic-chain performance may relate to neural adaptation involving motor learning and/or improved muscle strength of other muscles than the weak knee extensors. Muscle Nerve 54: 239-243, 2016. © 2016 Wiley Periodicals, Inc.

Magnetic Resonance Assessment of Hypertrophic and Pseudo-Hypertrophic Changes in Lower Leg Muscles of Boys with Duchenne Muscular Dystrophy and Their Relationship to Functional Measurements.

PubMed

Vohra, Ravneet S; Lott, Donovan; Mathur, Sunita; Senesac, Claudia; Deol, Jasjit; Germain, Sean; Bendixen, Roxanna; Forbes, Sean C; Sweeney, H Lee; Walter, Glenn A; Vandenborne, Krista

2015-01-01

The primary objectives of this study were to evaluate contractile and non-contractile content of lower leg muscles of boys with Duchenne muscular dystrophy (DMD) and determine the relationships between non-contractile content and functional abilities. Lower leg muscles of thirty-two boys with DMD and sixteen age matched unaffected controls were imaged. Non-contractile content, contractile cross sectional area and non-contractile cross sectional area of lower leg muscles (tibialis anterior, extensor digitorum longus, peroneal, medial gastrocnemius and soleus) were assessed by magnetic resonance imaging (MRI). Muscle strength, timed functional tests and the Brooke lower extremity score were also assessed. Non-contractile content of lower leg muscles (peroneal, medial gastrocnemius, and soleus) was significantly greater than control group (p<0.05). Non-contractile content of lower leg muscles correlated with Brooke score (rs = 0.64-0.84) and 30 feet walk (rs = 0.66-0.80). Dorsiflexor (DF) and plantarflexor (PF) specific torque was significantly different between the groups. Overall, non-contractile content of the lower leg muscles was greater in DMD than controls. Furthermore, there was an age dependent increase in contractile content in the medial gastrocnemius of boys with DMD. The findings of this study suggest that T1 weighted MR images can be used to monitor disease progression and provide a quantitative estimate of contractile and non-contractile content of tissue in children with DMD.

Magnetic Resonance Assessment of Hypertrophic and Pseudo-Hypertrophic Changes in Lower Leg Muscles of Boys with Duchenne Muscular Dystrophy and Their Relationship to Functional Measurements

PubMed Central

Vohra, Ravneet S.; Lott, Donovan; Mathur, Sunita; Senesac, Claudia; Deol, Jasjit; Germain, Sean; Bendixen, Roxanna; Forbes, Sean C.; Sweeney, H. Lee; Walter, Glenn A.; Vandenborne, Krista

2015-01-01

Introduction The primary objectives of this study were to evaluate contractile and non-contractile content of lower leg muscles of boys with Duchenne muscular dystrophy (DMD) and determine the relationships between non-contractile content and functional abilities. Methods Lower leg muscles of thirty-two boys with DMD and sixteen age matched unaffected controls were imaged. Non-contractile content, contractile cross sectional area and non-contractile cross sectional area of lower leg muscles (tibialis anterior, extensor digitorum longus, peroneal, medial gastrocnemius and soleus) were assessed by magnetic resonance imaging (MRI). Muscle strength, timed functional tests and the Brooke lower extremity score were also assessed. Results Non-contractile content of lower leg muscles (peroneal, medial gastrocnemius, and soleus) was significantly greater than control group (p<0.05). Non-contractile content of lower leg muscles correlated with Brooke score (rs = 0.64-0.84) and 30 feet walk (rs = 0.66-0.80). Dorsiflexor (DF) and plantarflexor (PF) specific torque was significantly different between the groups. Discussion Overall, non-contractile content of the lower leg muscles was greater in DMD than controls. Furthermore, there was an age dependent increase in contractile content in the medial gastrocnemius of boys with DMD. The findings of this study suggest that T1 weighted MR images can be used to monitor disease progression and provide a quantitative estimate of contractile and non-contractile content of tissue in children with DMD. PMID:26103164

Interaction between descending input and thoracic reflexes for joint coordination in cockroach: I. descending influence on thoracic sensory reflexes.

PubMed

Mu, Laiyong; Ritzmann, Roy E

2008-03-01

Tethered cockroaches turn from unilateral antennal contact using asymmetrical movements of mesothoracic (T2) legs (Mu and Ritzmann in J Comp Physiol A 191:1037-1054, 2005). During the turn, the leg on the inside of the turn (the inside T2 leg) has distinctly different motor patterns from those in straight walking. One possible neural mechanism for the transformation from walking to inside leg turning could be that the descending commands alter a few critical reflexes that start a cascade of physical changes in leg movement or posture, leading to further alterations. This hypothesis has two implications: first, the descending activities must be able to influence thoracic reflexes. Second, one should be able to initiate the turning motor pattern without descending signals by mimicking a point farther down in the reflex cascade. We addressed the first implication in this paper by experiments on chordotonal organ reflexes. The activity of depressor muscle (Ds) and slow extensor tibia muscle (SETi) was excited and inhibited by stretching and relaxing the femoral chordotonal organ. However, the Ds responses were altered after eliminating the descending activity, while the SETi responses remain similar. The inhibition to Ds activity by stretching the coxal chordotonal organ was also altered after eliminating the descending activity.

Quadriceps strengthening with and without blood flow restriction in the treatment of patellofemoral pain: a double-blind randomised trial.

PubMed

Giles, Lachlan; Webster, Kate E; McClelland, Jodie; Cook, Jill L

2017-12-01

Quadriceps strengthening exercises are part of the treatment of patellofemoral pain (PFP), but the heavy resistance exercises may aggravate knee pain. Blood flow restriction (BFR) training may provide a low-load quadriceps strengthening method to treat PFP. Seventy-nine participants were randomly allocated to a standardised quadriceps strengthening (standard) or low-load BFR. Both groups performed 8 weeks of leg press and leg extension, the standard group at 70% of 1 repetition maximum (1RM) and the BFR group at 30% of 1RM. Interventions were compared using repeated-measures analysis of variance for Kujala Patellofemoral Score, Visual Analogue Scale for 'worst pain' and 'pain with daily activity', isometric knee extensor torque (Newton metre) and quadriceps muscle thickness (cm). Subgroup analyses were performed on those participants with painful resisted knee extension at 60°. Sixty-nine participants (87%) completed the study (standard, n=34; BFR, n=35). The BFR group had a 93% greater reduction in pain with activities of daily living (p=0.02) than the standard group. Participants with painful resisted knee extension (n=39) had greater increases in knee extensor torque with BFR than standard (p<0.01). No between-group differences were found for change in Kujala Patellofemoral Score (p=0.31), worst pain (p=0.24), knee extensor torque (p=0.07) or quadriceps thickness (p=0.2). No difference was found between interventions at 6 months. Compared with standard quadriceps strengthening, low load with BFR produced greater reduction in pain with daily living at 8 weeks in people with PFP. Improvements were similar between groups in worst pain and Kujala score. The subgroup with painful resisted knee extension had larger improvements in quadriceps strength from BFR. 12614001164684. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Decreased Muscle Strength Relates to Self-Reported Stooping, Crouching, or Kneeling Difficulty in Older Adults

PubMed Central

Goldberg, Allon; Alexander, Neil B.

2010-01-01

Background Bending down and kneeling are fundamental tasks of daily living, yet nearly a quarter of older adults report having difficulty performing or being unable to perform these movements. Older adults with stooping, crouching, or kneeling (SCK) difficulty have demonstrated an increased fall risk. Strength (force-generating capacity) measures may be useful for determining both SCK difficulty and fall risk. Objective The purposes of this study were: (1) to examine muscle strength differences in older adults with and without SCK difficulty and (2) to examine the relative contributions of trunk and leg muscle strength to SCK difficulty. Design This was a cross-sectional observational study. Methods Community-dwelling older adults (age [X̅±SD]=75.5±6.0 years) with SCK difficulty (n=27) or without SCK difficulty (n=21) were tested for leg and trunk strength and functional mobility. Isometric strength at the trunk, hip, knee, and ankle also was normalized by body weight and height. Results Compared with older adults with no SCK difficulty, those with SCK difficulty had significant decreases in normalized trunk extensor, knee extensor, and ankle dorsiflexor and plantar-flexor strength. In 2 separate multivariate analyses, raw ankle plantar-flexor strength (odds ratio [OR]=0.97, 95% confidence interval [CI]=0.95–0.99) and normalized knee extensor strength (OR=0.61, 95% CI=0.44–0.82) were significantly associated with SCK difficulty. Stooping, crouching, and kneeling difficulty also correlated with measures of functional balance and falls. Limitations Although muscle groups that were key to rising from SCK were examined, there are other muscle groups that may contribute to safe SCK performance. Conclusions Decreased muscle strength, particularly when normalized for body size, predicts SCK difficulty. These data emphasize the importance of strength measurement at multiple levels in predicting self-reported functional impairment. PMID:19942678

Localization and function of ATP-sensitive potassium channels in human skeletal muscle.

PubMed

Nielsen, Jens Jung; Kristensen, Michael; Hellsten, Ylva; Bangsbo, Jens; Juel, Carsten

2003-02-01

The present study investigated the localization of ATP-sensitive K+ (KATP) channels in human skeletal muscle and the functional importance of these channels for human muscle K+ distribution at rest and during muscle activity. Membrane fractionation based on the giant vesicle technique or the sucrose-gradient technique in combination with Western blotting demonstrated that the KATP channels are mainly located in the sarcolemma. This localization was confirmed by immunohistochemical measurements. With the microdialysis technique, it was demonstrated that local application of the KATP channel inhibitor glibenclamide reduced (P < 0.05) interstitial K+ at rest from approximately 4.5 to 4.0 mM, whereas the concentration in the control leg remained constant. Glibenclamide had no effect on the interstitial K+ accumulation during knee-extensor exercise at a power output of 60 W. In contrast to in vitro conditions, the present study demonstrated that under in vivo conditions the KATP channels are active at rest and contribute to the accumulation of interstitial K+.

Muscle damage induced by stretch-shortening cycle exercise.

PubMed

Kyröläinen, H; Takala, T E; Komi, P V

1998-03-01

Strenuous stretch-shortening cycle exercise was used as a model to study the leakage of proteins from skeletal muscle. The analysis included serum levels of creatine kinase (S-CK), myoglobin (S-Mb), and carbonic anhydrase (S-CA III). Blood samples from power- (N=11) and endurance-trained (N=10) athletes were collected before, 0, and 2 h after the exercise, which consisted of a total of 400 jumps. The levels of all determined myocellular proteins increased immediately after the exercise (P < 0.05-0.001) among both subject groups. In the endurance group, the protein levels increased (P < 0.05-0.001) further during the following 2 h after the exercise, and the ratio of S-CA III and S-Mb decreased (P < 0.05) in a before-after comparison. This was not the case among the power group despite their greater mechanical work (P < 0.001) and higher ratio of eccentric and concentric EMG activity of the leg extensor muscles (P < 0.05). The differences of the determined protein levels between the subject groups might be due to obvious differences in the muscle fiber distribution, differences in recruitment order of motor units, and/or differences in training background.

The Motor and the Brake of the Trailing Leg in Human Walking: Leg Force Control Through Ankle Modulation and Knee Covariance

PubMed Central

Toney, Megan E.; Chang, Young-Hui

2016-01-01

Human walking is a complex task, and we lack a complete understanding of how the neuromuscular system organizes its numerous muscles and joints to achieve consistent and efficient walking mechanics. Focused control of select influential task-level variables may simplify the higher-level control of steady state walking and reduce demand on the neuromuscular system. As trailing leg power generation and force application can affect the mechanical efficiency of step-to-step transitions, we investigated how joint torques are organized to control leg force and leg power during human walking. We tested whether timing of trailing leg force control corresponded with timing of peak leg power generation. We also applied a modified uncontrolled manifold analysis to test whether individual or coordinated joint torque strategies most contributed to leg force control. We found that leg force magnitude was adjusted from step-to-step to maintain consistent leg power generation. Leg force modulation was primarily determined by adjustments in the timing of peak ankle plantar-flexion torque, while knee torque was simultaneously covaried to dampen the effect of ankle torque on leg force. We propose a coordinated joint torque control strategy in which the trailing leg ankle acts as a motor to drive leg power production while trailing leg knee torque acts as a brake to refine leg power production. PMID:27334888

The Relationship among Leg Strength, Leg Power and Alpine Skiing Success.

ERIC Educational Resources Information Center

Gettman, Larry R.; Huckel, Jack R.

The purpose of this study was to relate leg strength and power to alpine skiing success as measured by FIS points. Isometric leg strength was represented by the knee extension test described by Clarke. Leg power was measured by the vertical jump test and the Margaria-Kalamen stair run. Results in the strength and power tests were correlated with…

Muscle Adaptations Following Short-Duration Bed Rest with Integrated Resistance, Interval, and Aerobic Exercise

NASA Technical Reports Server (NTRS)

Hackney, Kyle J.; Scott, Jessica M.; Buxton, Roxanne; Redd-Goetchius, Elizabeth; Crowell, J. Brent; Everett, Meghan E.; Wickwire, Jason; Ryder, Jeffrey W.; Bloomberg, Jacob J.; Ploutz-Snyder, Lori L.

2011-01-01

Unloading of the musculoskeletal system during space flight results in deconditioning that may impair mission-related task performance in astronauts. Exercise countermeasures have been frequently tested during bed rest (BR) and limb suspension; however, high-intensity, short-duration exercise prescriptions have not been fully explored. PURPOSE: To determine if a high intensity resistance, interval, and aerobic exercise program could protect against muscle atrophy and dysfunction when performed during short duration BR. METHODS: Nine subjects (1 female, 8 male) performed a combination of supine exercises during 2 weeks of horizontal BR. Resistance exercise (3 d / wk) consisted of squat, leg press, hamstring curl, and heel raise exercises (3 sets, 12 repetitions). Aerobic (6 d / wk) sessions alternated continuous (75% VO2 peak) and interval exercise (30 s, 2 min, and 4 min) and were completed on a supine cycle ergometer and vertical treadmill, respectively. Muscle volumes of the upper leg were calculated pre, mid, and post-BR using magnetic resonance imaging. Maximal isometric force (MIF), rate of force development (RFD), and peak power of the lower body extensors were measured twice before BR (averaged to represent pre) and once post BR. ANOVA with repeated measures and a priori planned contrasts were used to test for differences. RESULTS: There were no changes to quadriceps, hamstring, and adductor muscle volumes at mid and post BR time points compared to pre BR (Table 1). Peak power increased significantly from 1614 +/- 372 W to 1739 +/- 359 W post BR (+7.7%, p = 0.035). Neither MIF (pre: 1676 +/- 320 N vs. post: 1711 +/- 250 N, +2.1%, p = 0.333) nor RFD (pre: 7534 +/- 1265 N/ms vs. post: 6951 +/- 1241 N/ms, -7.7%, p = 0.136) were significantly impaired post BR.

Sensitivity of sensor-based sit-to-stand peak power to the effects of training leg strength, leg power and balance in older adults.

PubMed

Regterschot, G Ruben H; Folkersma, Marjanne; Zhang, Wei; Baldus, Heribert; Stevens, Martin; Zijlstra, Wiebren

2014-01-01

Increasing leg strength, leg power and overall balance can improve mobility and reduce fall risk. Sensor-based assessment of peak power during the sit-to-stand (STS) transfer may be useful for detecting changes in mobility and fall risk. Therefore, this study investigated whether sensor-based STS peak power and related measures are sensitive to the effects of increasing leg strength, leg power and overall balance in older adults. A further aim was to compare sensitivity between sensor-based STS measures and standard clinical measures of leg strength, leg power, balance, mobility and fall risk, following an exercise-based intervention. To achieve these aims, 26 older adults (age: 70-84 years) participated in an eight-week exercise program aimed at improving leg strength, leg power and balance. Before and after the intervention, performance on normal and fast STS transfers was evaluated with a hybrid motion sensor worn on the hip. In addition, standard clinical tests (isometric quadriceps strength, Timed Up and Go test, Berg Balance Scale) were performed. Standard clinical tests as well as sensor-based measures of peak power, maximal velocity and duration of normal and fast STS showed significant improvements. Sensor-based measurement of peak power, maximal velocity and duration of normal STS demonstrated a higher sensitivity (absolute standardized response mean (SRM): ≥ 0.69) to the effects of training leg strength, leg power and balance than standard clinical measures (absolute SRM: ≤ 0.61). Therefore, the presented sensor-based method appears to be useful for detecting changes in mobility and fall risk. Copyright © 2013 Elsevier B.V. All rights reserved.

The role of active muscle mass in determining the magnitude of peripheral fatigue during dynamic exercise.

PubMed

Rossman, Matthew J; Garten, Ryan S; Venturelli, Massimo; Amann, Markus; Richardson, Russell S

2014-06-15

Greater peripheral quadriceps fatigue at the voluntary termination of single-leg knee-extensor exercise (KE), compared with whole-body cycling, has been attributed to confining group III and IV skeletal muscle afferent feedback to a small muscle mass, enabling the central nervous system (CNS) to tolerate greater peripheral fatigue. However, as task specificity and vastly differing systemic challenges may have complicated this interpretation, eight males were studied during constant workload trials to exhaustion at 85% of peak workload during single-leg and double-leg KE. It was hypothesized that because of the smaller muscle mass engaged during single-leg KE, a greater magnitude of peripheral quadriceps fatigue would be present at exhaustion. Vastus lateralis integrated electromyogram (iEMG) signal relative to the first minute of exercise, preexercise to postexercise maximal voluntary contractions (MVCs) of the quadriceps, and twitch-force evoked by supramaximal magnetic femoral nerve stimulation (Qtw,pot) quantified peripheral quadriceps fatigue. Trials performed with single-leg KE (8.1 ± 1.2 min; 45 ± 4 W) resulted in significantly greater peripheral quadriceps fatigue than double-leg KE (10 ± 1.3 min; 83 ± 7 W), as documented by changes in the iEMG signal (147 ± 24 vs. 85 ± 13%), MVC (-25 ± 3 vs. -12 ± 3%), and Qtw,pot (-44 ± 6 vs. -33 ± 7%), for single-leg and double-leg KE, respectively. Therefore, avoiding concerns over task specificity and cardiorespiratory limitations, this study reveals that a reduction in muscle mass permits the development of greater peripheral muscle fatigue and supports the concept that the CNS tolerates a greater magnitude of peripheral fatigue when the source of group III/IV afferent feedback is limited to a small muscle mass.

[Pattern of paralysis and reconstructive operations after traumatic brachial plexus lesions].

PubMed

Rühmann, O; Schmolke, S; Carls, J; Wirth, C J

2002-12-01

The aim of this study was to evaluate persistent patterns of paralysis after traumatic brachial plexus lesions. As a result, consecutive reconstructive operations according to our differential therapy concept are presented. Between 04/1994 and 12/2000 in 104 patients with brachial plexus palsy, the grade of muscle power of the affected upper extremities was evaluated prospectively. The neuromuscular patterns of defect showed, in most cases, insufficient muscle power grades of 0-2 for the deltoid muscle (90%), supraspinatus muscle (82%), infraspinatus muscle (93%), elbow flexors (67% to 77%), hand and finger extensors (69% to 71%), and the abductor and extensors of the thumb (67% to 70%). In corresponding frequency, the following operations were performed between 04/1994 and 06/2002: shoulder arthrodesis (n 26), trapezius transfer (n 80), rotation osteotomy of humerus (n 10), triceps to biceps transposition (n 11), transposition of forearm flexors or extensors/Steindler operation (n 12), latissimus transfer (n 7), pectoralis transfer (n 1), teres major transfer (n 1), transposition of forearm flexors to the tendons of extensor digitorum (n 19) and of the extensor pollicis longus (n 9), and wrist arthrodesis (n 5). On malfunction of muscles following brachial plexus lesions, taking into account the individual neuromuscular defect, passive joint function, and bony deformities, different procedures such as muscle transposition, arthrodesis, and corrective osteotomy can be performed to improve function of the upper extremity.

Musculoskeletal profile of middle-aged Ving Tsun Chinese martial art practitioners

PubMed Central

Fong, Shirley S.M.; Chan, Jessie S.M.; Bae, Young-Hyeon; Yam, Timothy T.T.; Chung, Louisa M.Y.; Ma, Ada W.W.; Kuisma, Raija

2017-01-01

Abstract This cross-sectional exploratory study aimed to quantify and compare the axial and appendicular bone mineral density (BMD), muscle mass, and muscle strength of middle-aged practitioners of Ving Tsun (VT; a hard-style Chinese martial art) with those of nonpractitioners. Eighteen VT practitioners (mean age ± standard deviation = 51.8 ± 17.7 years; 12 men and six women) and 36 active controls (mean age ± standard deviation = 58.7 ± 11.0 years; 18 men and 18 women) participated in the study. All participants underwent a 1-day battery of musculoskeletal examinations. The BMD of the total radius, total hip, femoral neck, and lumbar spine was measured using dual-energy X-ray absorptiometry, as was the lean mass of the arm, leg, and trunk. Muscle strength of the upper and lower limbs was assessed using a Jamar dynamometer and an isokinetic dynamometer at 60°/second, respectively. VT-trained participants had a 11.5% higher total radius BMD (P = 0.023), a 17.8% higher leg lean mass (P = 0.014), a 56.4% higher isokinetic body weight-adjusted peak torque of the knee extensors (P < 0.001), a 60.8% higher isokinetic body weight-adjusted peak torque of knee flexors (P < 0.001), and a 31.4% shorter time to reach peak torque in the knee flexors (P = 0.001) than the active controls. No significant differences were found in any of the other musculoskeletal outcomes between the 2 groups (P > 0.05). Middle-aged VT practitioners displayed a higher total radius BMD and leg lean mass and better knee extensor and flexor muscular performances than their healthy active counterparts. Healthcare professionals may consider using this alternative method of training to improve the musculoskeletal health of middle-aged adults. PMID:28121945

Altered biomechanical strategies and medio-lateral control of the knee represent incomplete recovery of individuals with injury during single leg hop.

PubMed

Roos, Paulien E; Button, Kate; Sparkes, Valerie; van Deursen, Robert W M

2014-02-07

Anterior cruciate ligament (ACL) injury can result in failure to return to pre-injury activity levels and future osteoarthritis predisposition. Single leg hop is used in late rehabilitation to evaluate recovery and inform treatment but biomechanical understanding of this activity is insufficient. This study investigated single leg hop for distance aiming to evaluate if ACL patients had recovered: (1) landing strategies and (2) medio-lateral knee control. We hypothesized that patients with reconstructive surgery (ACLR) would have more similar landing strategies and knee control to healthy controls than patients treated conservatively (ACLD). 16 ACLD and 23 ACLR subjects were compared to 20 healthy controls (CONT). Kinematic and ground reaction force data were collected while subjects hopped their maximum distance. The main output parameters were hop distance, peak knee flexor angles and extensor moments and Fluency (a measure introduced to represent medio-lateral knee control). Statistical differences between ACL and control groups were analyzed using a general linear model univariate analysis, with COM velocity prior to landing as covariate. Hop distance was the smallest for ACLD and largest for CONT (p<0.001; ACLD 57.1±14.1; ACLR 75.1±17.8; CONT 77.7±14.07% height). ACLR used a similar kinematic strategy to CONT, but had a reduced peak knee extensor moment (p<0.001; ACLD 0.32±0.14; ACLR 0.31±0.16; CONT 0.42±0.13 BW.height). Fluency was reduced in both ACLD and ACLR (p=0.006; ACLD 0.13±0.34; ACLR 0.14±0.34; CONT 0.17±0.41s). Clinical practice uses hopping distance to evaluate ACL patients' recovery. This study demonstrated that aspects such as movement strategies and knee control need to be evaluated. © 2013 Published by Elsevier Ltd.

Musculoskeletal profile of middle-aged Ving Tsun Chinese martial art practitioners: A cross-sectional study.

PubMed

Fong, Shirley S M; Chan, Jessie S M; Bae, Young-Hyeon; Yam, Timothy T T; Chung, Louisa M Y; Ma, Ada W W; Kuisma, Raija

2017-01-01

This cross-sectional exploratory study aimed to quantify and compare the axial and appendicular bone mineral density (BMD), muscle mass, and muscle strength of middle-aged practitioners of Ving Tsun (VT; a hard-style Chinese martial art) with those of nonpractitioners.Eighteen VT practitioners (mean age ± standard deviation = 51.8 ± 17.7 years; 12 men and six women) and 36 active controls (mean age ± standard deviation = 58.7 ± 11.0 years; 18 men and 18 women) participated in the study. All participants underwent a 1-day battery of musculoskeletal examinations. The BMD of the total radius, total hip, femoral neck, and lumbar spine was measured using dual-energy X-ray absorptiometry, as was the lean mass of the arm, leg, and trunk. Muscle strength of the upper and lower limbs was assessed using a Jamar dynamometer and an isokinetic dynamometer at 60°/second, respectively.VT-trained participants had a 11.5% higher total radius BMD (P = 0.023), a 17.8% higher leg lean mass (P = 0.014), a 56.4% higher isokinetic body weight-adjusted peak torque of the knee extensors (P < 0.001), a 60.8% higher isokinetic body weight-adjusted peak torque of knee flexors (P < 0.001), and a 31.4% shorter time to reach peak torque in the knee flexors (P = 0.001) than the active controls. No significant differences were found in any of the other musculoskeletal outcomes between the 2 groups (P > 0.05).Middle-aged VT practitioners displayed a higher total radius BMD and leg lean mass and better knee extensor and flexor muscular performances than their healthy active counterparts. Healthcare professionals may consider using this alternative method of training to improve the musculoskeletal health of middle-aged adults.

Strength testing and training of rowers: a review.

PubMed

Lawton, Trent W; Cronin, John B; McGuigan, Michael R

2011-05-01

In the quest to maximize average propulsive stroke impulses over 2000-m racing, testing and training of various strength parameters have been incorporated into the physical conditioning plans of rowers. Thus, the purpose of this review was 2-fold: to identify strength tests that were reliable and valid correlates (predictors) of rowing performance; and, to establish the benefits gained when strength training was integrated into the physical preparation plans of rowers. The reliability of maximal strength and power tests involving leg extension (e.g. leg pressing) and arm pulling (e.g. prone bench pull) was high (intra-class correlations 0.82-0.99), revealing that elite rowers were significantly stronger than their less competitive peers. The greater strength of elite rowers was in part attributed to the correlation between strength and greater lean body mass (r = 0.57-0.63). Dynamic lower body strength tests that determined the maximal external load for a one-repetition maximum (1RM) leg press (kg), isokinetic leg extension peak force (N) or leg press peak power (W) proved to be moderately to strongly associated with 2000-m ergometer times (r = -0.54 to -0.68; p < 0.05). Repetition tests that assess muscular or strength endurance by quantifying the number of repetitions accrued at a fixed percentage of the strength maximum (e.g. 50-70% 1RM leg press) or set absolute load (e.g. 40 kg prone bench pulls) were less reliable and more time consuming when compared with briefer maximal strength tests. Only leg press repetition tests were correlated with 2000-m ergometer times (e.g. r = -0.67; p < 0.05). However, these tests differentiate training experience and muscle morphology, in that those individuals with greater training experience and/or proportions of slow twitch fibres performed more repetitions. Muscle balance ratios derived from strength data (e.g. hamstring-quadriceps ratio <45% or knee extensor-elbow flexor ratio around 4.2 ± 0.22 to 1) appeared useful in the pathological assessment of low back pain or rib injury history associated with rowing. While strength partially explained variances in 2000-m ergometer performance, concurrent endurance training may be counterproductive to strength development over the shorter term (i.e. <12 weeks). Therefore, prioritization of strength training within the sequence of training units should be considered, particularly over the non-competition phase (e.g. 2-6 sets × 4-12 repetitions, three sessions a week). Maximal strength was sustained when infrequent (e.g. one or two sessions a week) but intense (e.g. 73-79% of maximum) strength training units were scheduled; however, it was unclear whether training adaptations should emphasize maximal strength, endurance or power in order to enhance performance during the competition phase. Additionally, specific on-water strength training practices such as towing ropes had not been reported. Further research should examine the on-water benefits associated with various strength training protocols, in the context of the training phase, weight division, experience and level of rower, if limitations to the reliability and precision of performance data (e.g. 2000-m time or rank) can be controlled. In conclusion, while positive ergometer time-trial benefits of clinical and practical significance were reported with strength training, a lack of statistical significance was noted, primarily due to an absence of quality long-term controlled experimental research designs.

Does insulin-like growth factor 1 genotype influence muscle power response to strength training in older men and women?

PubMed

Sood, Suchi; Hanson, Erik D; Delmonico, Matthew J; Kostek, Matthew C; Hand, Brian D; Roth, Stephen M; Hurley, Ben F

2012-02-01

The CA-repeat polymorphism in the insulin-like growth factor 1 (IGF1) gene promoter region has been associated with strength and circulating IGF-I protein levels. The purpose of the study was to determine if the IGF1 CA-repeat polymorphism influences muscle power at baseline and in response to ST in older adults. Knee extensor peak power (PP) was measured at 50, 60, and 70% of 1-RM strength before and after 10 weeks of unilateral knee extensor ST in older adults, aged 50-85 years, to determine the changes in absolute and relative PP with ST. Subjects (N = 114) were genotyped for the IGF1 CA-repeat polymorphism and grouped as homozygous for the 192 allele, heterozygous, or non-carriers of the 192 allele. The 192 homozygotes had significantly lower baseline PP at 50, 60, and 70% of 1-RM strength than the non-carriers when age, sex, and baseline fat-free mass were covaried (all P < 0.05). This same relationship was observed when the highest PP within these ranges was compared (e.g., 317.6 ± 13.5 for 192 homozygotes and 380.2 ± 16.3 for non-carriers of the 192 allele, P < 0.05). Both absolute and relative PP increased significantly with ST in all genotype groups as expected, but there were no significant relationships among IGF1 genotypes and any of the PP changes. Despite a significant relationship between IGF1 genotype and knee extensor peak power at baseline, IGF1 genotype does not appear to influence changes in knee extensor peak power with ST.

Statin myalgia is not associated with reduced muscle strength, mass or protein turnover in older male volunteers, but is allied with a slowing of time to peak power output, insulin resistance and differential muscle mRNA expression

PubMed Central

Mallinson, Joanne E.; Marimuthu, Kanagaraj; Murton, Andrew; Selby, Anna; Smith, Kenneth; Constantin‐Teodosiu, Dumitru; Rennie, Michael J.

2015-01-01

Key points Statins cause muscle‐specific side effects, most commonly muscle aches/weakness (myalgia), particularly in older people. Furthermore, evidence has linked statin use to increased risk of type 2 diabetes. However, the mechanisms involved are unknown.This is the first study to measure muscle protein turnover rates and insulin sensitivity in statin myalgic volunteers and age‐matched, non‐statin users under controlled fasting and fed conditions using gold standard methods.We demonstrate in older people that chronic statin myalgia is not associated with deficits in muscle strength and lean mass or the dysregulation of muscle protein turnover compared to non‐statin users. Furthermore, there were no between‐group differences in blood or muscle inflammatory markers.Statin users did, however, show blunting of muscle power output at the onset of dynamic exercise, increased abdominal adiposity, whole body and leg insulin resistance, and clear differential expression of muscle genes linked to mitochondrial dysfunction and apoptosis, which warrant further investigation. Abstract Statins are associated with muscle myalgia and myopathy, which probably reduce habitual physical activity. This is particularly relevant to older people who are less active, sarcopaenic and at increased risk of statin myalgia. We hypothesised that statin myalgia would be allied to impaired strength and work capacity in older people, and determined whether differences aligned with divergences in lean mass, protein turnover, insulin sensitivity and the molecular regulation of these processes. Knee extensor strength and work output during 30 maximal isokinetic contractions were assessed in healthy male volunteers, nine with no statin use (control 70.4 ± 0.7 years) and nine with statin myalgia (71.5 ± 0.9 years). Whole body and leg glucose disposal, muscle myofibrillar protein synthesis (MPS) and leg protein breakdown (LPB) were measured during fasting (≈5 mU l−1 insulin) and fed (≈40 mU l−1 insulin + hyperaminoacidaemia) euglyceamic clamps. Muscle biopsies were taken before and after each clamp. Lean mass, MPS, LPB and strength were not different but work output during the initial three isokinetic contractions was 19% lower (P < 0.05) in statin myalgic subjects due to a delay in time to reach peak power output. Statin myalgic subjects had reduced whole body (P = 0.05) and leg (P < 0.01) glucose disposal, greater abdominal adiposity (P < 0.05) and differential expression of 33 muscle mRNAs (5% false discovery rate (FDR)), six of which, linked to mitochondrial dysfunction and apoptosis, increased at 1% FDR. Statin myalgia was associated with impaired muscle function, increased abdominal adiposity, whole body and leg insulin resistance, and evidence of mitochondrial dysfunction and apoptosis. PMID:25620655

Relationship between hip and core strength and frontal plane alignment during a single leg squat.

PubMed

Stickler, Laurie; Finley, Margaret; Gulgin, Heather

2015-02-01

The purpose of this study was to examine the relationship between frontal plane kinematics of the single leg squat and strength of the trunk and hip in females. Forty healthy females participated in this study. An isometric "make" test using a dynamometer was used to assess peak force normalized to body weight for hip abduction, hip extension, hip external rotation, and a sidelying plank test. Two-dimensional software was used to analyze the frontal plane projection angle (FPPA) and pelvic angle during a single leg squat to 60°. All 4 strength factors were significantly correlated with the FPPA, ranging from r = 0.396 to r = 0.466. During multiple regression analysis, hip abduction strength was the greatest predictor of the variation in FPPA at r(2) = 0.22, p = 0.002. Thus, hip abduction strength accounted for 22% of the variation in the FPPA during the single leg squat. The only strength factor demonstrating a significant correlation with the pelvic angle was hip extension strength (r = 0.550, p < 0.001). Clinicians should consider the role of the hip abductors, hip external rotators, hip extensors and core musculature on the impact on the FPPA during a single squat, with focus on the hip abductors. Copyright © 2014 Elsevier Ltd. All rights reserved.

Use of muscle synergies and wavelet transforms to identify fatigue during squatting.

PubMed

Smale, Kenneth B; Shourijeh, Mohammad S; Benoit, Daniel L

2016-06-01

The objective of this study was to supplement continuous wavelet transforms with muscle synergies in a fatigue analysis to better describe the combination of decreased firing frequency and altered activation profiles during dynamic muscle contractions. Nine healthy young individuals completed the dynamic tasks before and after they squatted with a standard Olympic bar until complete exhaustion. Electromyography (EMG) profiles were analyzed with a novel concatenated non-negative matrix factorization method that decomposed EMG signals into muscle synergies. Muscle synergy analysis provides the activation pattern of the muscles while continuous wavelet transforms output the temporal frequency content of the EMG signals. Synergy analysis revealed subtle changes in two-legged squatting after fatigue while differences in one-legged squatting were more pronounced and included the shift from a general co-activation of muscles in the pre-fatigue state to a knee extensor dominant weighting post-fatigue. Continuous wavelet transforms showed major frequency content decreases in two-legged squatting after fatigue while very few frequency changes occurred in one-legged squatting. It was observed that the combination of methods is an effective way of describing muscle fatigue and that muscle activation patterns play a very important role in maintaining the overall joint kinetics after fatigue. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dynamics of neurons controlling movements of a locust hind leg. III. Extensor tibiae motor neurons.

PubMed

Newland, P L; Kondoh, Y

1997-06-01

Imposed movements of the apodeme of the femoral chordotonal organ (FeCO) of the locust hind leg elicit resistance reflexes in extensor and flexor tibiae motor neurons. The synaptic responses of the fast and slow extensor tibiae motor neurons (FETi and SETi, respectively) and the spike responses of SETi were analyzed with the use of the Wiener kernel white noise method to determine their response properties. The first-order Wiener kernels computed from soma recordings were essentially monophasic, or low passed, indicating that the motor neurons were primarily sensitive to the position of the tibia about the femorotibial joint. The responses of both extensor motor neurons had large nonlinear components. The second-order kernels of the synaptic responses of FETi and SETi had large on-diagonal peaks with two small off-diagonal valleys. That of SETi had an additional elongated valley on the diagonal, which was accompanied by two off-diagonal depolarizing peaks at a cutoff frequency of 58 Hz. These second-order components represent a half-wave rectification of the position-sensitive depolarizing response in FETi and SETi, and a delayed inhibitory input to SETi, indicating that both motor neurons were directionally sensitive. Model predictions of the responses of the motor neurons showed that the first-order (linear) characterization poorly predicted the actual responses of FETi and SETi to FeCO stimulation, whereas the addition of the second-order (nonlinear) term markedly improved the performance of the model. Simultaneous recordings from the soma and a neuropilar process of FETi showed that its synaptic responses to FeCO stimulation were phase delayed by about -30 degrees at 20 Hz, and reduced in amplitude by 30-40% when recorded in the soma. Similar configurations of the first and second-order kernels indicated that the primary process of FETi acted as a low-pass filter. Cross-correlation between a white noise stimulus and a unitized spike discharge of SETi again produced well-defined first- and second-order kernels that showed that the SETi spike response was also dependent on positional inputs. An elongated negative valley on the diagonal, characteristic of the second-order kernel of the synaptic response in SETi, was absent in the kernel from the spike component, suggesting that information is lost in the spike production process. The functional significance of these results is discussed in relation to the behavior of the locust.

Embryonic development of the innervation of the locust extensor tibiae muscle by identified neurons: formation and elimination of inappropriate axon branches.

PubMed

Myers, C M; Whitington, P M; Ball, E E

1990-01-01

Intracellular dye fills have been used to reveal the pattern of embryonic growth of each of the four neurons which innervate the extensor tibiae muscle (ETi) of the hind leg of the locust. The growth cone of the slow extensor tibiae motoneuron (SETi), the first of the four neurons to leave the central nervous system, pioneers nerve 3 (N3). The fast extensor motoneuron (FETi), the next neuron to grow out, follows earlier outgrowing motoneurons into the periphery in nerve 5 (N5) and then rejoins SETi in N3. As it transfers from N5 to N3, it is transiently dye-coupled to the Tr1 pioneer neuron which spans the gap between the two nerves. It then follows SETi onto the ETi muscle in the femur. The common inhibitory neuron and the dorsal unpaired median neuron (DUMETi) follow SETi and FETi in nerves 3B2 and 5B1, respectively. SETi's growth cone requires almost twice as long to reach ETi as those of the three later motoneurons, all of which follow preexisting neural pathways. At least three of the four developing motoneurons form one or more axon branches not found in the adult. These branches may occur (1) at segmental boundaries; (2) where the nerve, which the growth cone is following, itself branches or the growth cone encounters another nerve; or (3) when the axon continues to grow beyond its target muscle. These findings contrast with the apparent absence of inappropriate axon branches in another developing locust neuromuscular system and during the innervation of zebrafish myotomes, but resemble in some ways the transient production of inappropriate axonal branches reported for embryonic leech motoneurons.

Relationship between strength, power and balance performance in seniors.

PubMed

Muehlbauer, Thomas; Besemer, Carmen; Wehrle, Anja; Gollhofer, Albert; Granacher, Urs

2012-01-01

Deficits in strength, power and balance represent important intrinsic risk factors for falls in seniors. The purpose of this study was to investigate the relationship between variables of lower extremity muscle strength/power and balance, assessed under various task conditions. Twenty-four healthy and physically active older adults (mean age: 70 ± 5 years) were tested for their isometric strength (i.e. maximal isometric force of the leg extensors) and muscle power (i.e. countermovement jump height and power) as well as for their steady-state (i.e. unperturbed standing, 10-meter walk), proactive (i.e. Timed Up & Go test, Functional Reach Test) and reactive (i.e. perturbed standing) balance. Balance tests were conducted under single (i.e. standing or walking alone) and dual task conditions (i.e. standing or walking plus cognitive and motor interference task). Significant positive correlations were found between measures of isometric strength and muscle power of the lower extremities (r values ranged between 0.608 and 0.720, p < 0.01). Hardly any significant associations were found between variables of strength, power and balance (i.e. no significant association in 20 out of 21 cases). Additionally, no significant correlations were found between measures of steady-state, proactive and reactive balance or balance tests performed under single and dual task conditions (all p > 0.05). The predominately nonsignificant correlations between different types of balance imply that balance performance is task specific in healthy and physically active seniors. Further, strength, power and balance as well as balance under single and dual task conditions seem to be independent of each other and may have to be tested and trained complementarily. Copyright © 2012 S. Karger AG, Basel.

Muscular strength profile in Tunisian male national judo team.

PubMed

Ghrairi, Mourad; Hammouda, Omar; Malliaropoulos, Nikos

2014-04-01

it is well established that muscle strength is a determinant factor in judo. However, little data are available for African athletes. Therefore, the aim of this study was to provide reference data of the muscular strength profile (MSP) for an African team, Tunisian judo team. the study was conducted among ten international judo athletes from Tunisia. To determine their MSP, we used an isokinetic dynamometer to assess Hamstrings, Quadriceps of both knees and external, internal rotators of both shoulders. The angular velocities of the assessments were; 90, 180, 240°/s for the knees and 60, 120°/s for the shoulders. MSP was determined based on two parameters; the maximum peak torque (PT) of each muscle and the ratio agonistic/antagonistic muscles (R). The knee extensors and flexors in the "supporting leg" had higher PT than in the "attacking leg"; respectively, 245N.m versus 237 (p<0.05) and 147 N.m versus 145 (p>0.05). R was normal for both legs. Furthermore, both rotators of the dominant shoulder had higher PT; 84 N.m versus 71 for the internal rotators (p<0.05) and 34,7 N.m versus 29,0 for the lateral rotators (p<0.05). Inversely, R was higher in the non-dominant side; 45% versus 35, p<0.05). the MSP of the selected elites Tunisian judo athletes was characterized by 3 major features; a strength of the quadriceps in the standing leg significantly higher than in the attacking leg, a normal muscular balance Hamstrings/quadriceps in both legs and a strength of the shoulder' rotators higher in the dominant side.

Functional anatomy and muscle moment arms of the pelvic limb of an elite sprinting athlete: the racing greyhound (Canis familiaris)

PubMed Central

Williams, S B; Wilson, A M; Rhodes, L; Andrews, J; Payne, R C

2008-01-01

We provide quantitative anatomical data on the muscle–tendon architecture and geometry of the pelvic limb of an elite sprint athlete, the racing greyhound. Specifically, muscle masses, muscle lengths, fascicle lengths, pennation angles and muscle moment arms were measured. Maximum isometric force and power of muscles, the maximum muscle torque at joints and tendon stress and strain were estimated. We compare data with that published for a generalized breed of canid, and other cursorial mammals such as the horse and hare. The pelvic limb of the racing greyhound had a relatively large volume of hip extensor muscle, which is likely to be required for power production. Per unit body mass, some pelvic limb muscles were relatively larger than those in less specialized canines, and many hip extensor muscles had longer fascicle lengths. It was estimated that substantial extensor moments could be created about the tarsus and hip of the greyhound allowing high power output and potential for rapid acceleration. The racing greyhound hence possesses substantial specializations for enhanced sprint performance. PMID:18657259

Functional anatomy and muscle moment arms of the pelvic limb of an elite sprinting athlete: the racing greyhound (Canis familiaris).

PubMed

Williams, S B; Wilson, A M; Rhodes, L; Andrews, J; Payne, R C

2008-10-01

We provide quantitative anatomical data on the muscle-tendon architecture and geometry of the pelvic limb of an elite sprint athlete, the racing greyhound. Specifically, muscle masses, muscle lengths, fascicle lengths, pennation angles and muscle moment arms were measured. Maximum isometric force and power of muscles, the maximum muscle torque at joints and tendon stress and strain were estimated. We compare data with that published for a generalized breed of canid, and other cursorial mammals such as the horse and hare. The pelvic limb of the racing greyhound had a relatively large volume of hip extensor muscle, which is likely to be required for power production. Per unit body mass, some pelvic limb muscles were relatively larger than those in less specialized canines, and many hip extensor muscles had longer fascicle lengths. It was estimated that substantial extensor moments could be created about the tarsus and hip of the greyhound allowing high power output and potential for rapid acceleration. The racing greyhound hence possesses substantial specializations for enhanced sprint performance.

Changes in the activity of trunk and hip extensor muscles during bridge exercises with variations in unilateral knee joint angle.

PubMed

Kim, Juseung; Park, Minchul

2016-09-01

[Purpose] This study compared abdominal and hip extensor muscle activity during a bridge exercise with various knee joint angles. [Subjects and Methods] Twenty-two healthy male subjects performed a bridge exercise in which the knee joint angle was altered. While subjects performed the bridge exercise, external oblique, internal oblique, gluteus maximus, and semitendinosus muscle activity was measured using electromyography. [Results] The bilateral external and internal oblique muscle activity was significantly higher at 0° knee flexion compared to 120°, 90°, and 60°. The bilateral gluteus maximus muscle activity was significantly different at 0° of knee flexion compared to 120°, 90°, and 60°. The ipsilateral semitendinosus muscle activity was significantly increased at 90° and 60° of knee flexion compared to 120°, and significantly decreased at 0° knee flexion compared with 120°, 90°, and 60°. The contralateral semitendinosus muscle activity was significantly higher at 60° of knee flexion than at 120°, and significantly higher at 0° of knee flexion than at 120°, 90°, and 60°. [Conclusion] Bridge exercises performed with knee flexion less than 90° may be used to train the ipsilateral semitendinosus. Furthermore, bridge exercise performed with one leg may be used to train abdominal and hip extensor muscles.

Muscle blood flow at onset of dynamic exercise in humans.

PubMed

Rådegran, G; Saltin, B

1998-01-01

To evaluate the temporal relationship between blood flow, blood pressure, and muscle contractions, we continuously measured femoral arterial inflow with ultrasound Doppler at onset of passive exercise and voluntary, one-legged, dynamic knee-extensor exercise in humans. Blood velocity and inflow increased (P < 0.006) with the first relaxation of passive and voluntary exercise, whereas the arterial-venous pressure difference was unaltered [P = not significant (NS)]. During steady-state exercise, and with arterial pressure as a superimposed influence, blood velocity was affected by the muscle pump, peaking (P < 0.001) at approximately 2.5 +/- 0.3 m/s as the relaxation coincided with peak systolic arterial blood pressure; blood velocity decreased (P < 0.001) to 44.2 +/- 8.6 and 28.5 +/- 5.5% of peak velocity at the second dicrotic and diastolic blood pressure notches, respectively. Mechanical hindrance occurred (P < 0.001) during the contraction phase at blood pressures less than or equal to that at the second dicrotic notch. The increase in blood flow (Q) was characterized by a one-component (approximately 15% of peak power output), two-component (approximately 40-70% of peak power output), or three-component exponential model (> or = 75% of peak power output), where Q(t) = Qpassive + delta Q1.[1 - e-(t - TD1/tau 1)]+ delta Q2.[1 - e-(t - TD2/tau 2)]+ delta Q3.[1 - e-(t - TD3/tau 3)]; Qpassive, the blood flow during passive leg movement, equals 1.17 +/- 0.11 l/min; TD is the onset latency; tau is the time constant; delta Q is the magnitude of blood flow rise; and subscripts 1-3 refer to the first, second, and third components of the exponential model, respectively. The time to reach 50% of the difference between passive and voluntary asymptotic blood flow was approximately 2.2-8.9 s. The blood flow leveled off after approximately 10-150 s, related to the power outputs. It is concluded that the elevation in blood flow with the first duty cycle(s) is due to muscle mechanical factors, but vasodilators initiate a more potent amplification within the second to fourth contraction.

The influence of electromyographic recording methods and the innervation zone on the mean power frequency-torque relationships.

PubMed

Herda, Trent J; Zuniga, Jorge M; Ryan, Eric D; Camic, Clayton L; Bergstrom, Haley C; Smith, Doug B; Weir, Joseph P; Cramer, Joel T; Housh, Terry J

2015-06-01

This study examined the effects of electromyographic (EMG) recording methods and innervation zone (IZ) on the mean power frequency (MPF)-torque relationships. Nine subjects performed isometric ramp muscle actions of the leg extensors from 5% to 100% of maximal voluntary contraction with an eight channel linear electrode array over the IZ of the vastus lateralis. The slopes were calculated from the log-transformed monopolar and bipolar EMG MPF-torque relationships for each channel and subject and 95% confidence intervals (CI) were constructed around the slopes for each relationship and the composite of the slopes. Twenty-two to 55% of the subjects exhibited 95% CIs that did not include a slope of zero for the monopolar EMG MPF-torque relationships while 25-75% of the subjects exhibited 95% CIs that did not include a slope of zero for the bipolar EMG MPF-torque relationships. The composite of the slopes from the EMG MPF-torque relationships were not significantly different from zero for any method or channel, however, the method and IZ location slightly influenced the number of significant slopes on a subject-by-subject basis. The log-transform model indicated that EMG MPF-torque patterns were nonlinear regardless of recording method or distance from the IZ. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of the forearm support band on wrist extensor muscle fatigue.

PubMed

Knebel, P T; Avery, D W; Gebhardt, T L; Koppenhaver, S L; Allison, S C; Bryan, J M; Kelly, A

1999-11-01

A crossover experimental design with repeated measures. To determine whether the forearm support band alters wrist extensor muscle fatigue. Fatigue of the wrist extensor muscles is thought to be a contributing factor in the development of lateral epicondylitis. The forearm support band is purported to reduce or prevent symptoms of lateral epicondylitis but the mechanism of action is unknown. Fifty unimpaired subjects (36 men, 14 women; mean age = 29 +/- 6 years) were tested with and without a forearm support band before and after a fatiguing bout of exercise. Peak wrist extension isometric force, peak isometric grip force, and median power spectral frequency for wrist extensor electromyographic activity were measured before and after exercise and with and without the forearm support band. A 2 x 2 repeated measures multivariate analysis of variance was used to analyze the data, followed by univariate analysis of variance and Tukey's multiple comparison tests. Peak wrist extension isometric force, peak grip isometric force, and median power spectral frequency were all reduced after exercise. However, there was a significant reduction in peak grip isometric force and peak wrist extension isometric force values for the with-forearm support band condition (grip force 28%, wrist extension force 26%) compared to the without-forearm support band condition (grip force 18%, wrist extension force 15%). Wearing the forearm support band increased the rate of fatigue in unimpaired individuals. Our findings do not support the premise that wearing the forearm support band reduces muscle fatigue in the wrist extensors.

Effects of graded exercise-induced dehydration and rehydration on circulatory markers of oxidative stress across the resting and exercising human leg.

PubMed

Laitano, Orlando; Kalsi, Kameljit Kaur; Pearson, James; Lotlikar, Makra; Reischak-Oliveira, Alvaro; González-Alonso, José

2012-05-01

Exercise in the heat enhances oxidative stress markers in the human circulation, but the contribution of active skeletal muscle and the influence of hydration status remain unknown. To address this question, we measured leg exchange of glutathione (GSH), glutathione disulfide (GSSG), superoxide dismutase activity (SOD) and isoprostanes in seven males at rest and during submaximal one-legged knee extensor exercise in the following four conditions: (1) control euhydration (0% reduction in body mass), (2) mild-dehydration (2%), (3) moderate-dehydration (3.5%), (4) rehydration (0%). In all resting and control exercise conditions, a net GSH uptake was observed across the leg. In contrast, a significant leg release of GSH into the circulation (-354 ± 221 μmol/min, P < 0.05) was observed during exercise with moderate-dehydration, which was still present following full rehydration (-206 ± 122 μmol/min, P < 0.05). During exercise, mild and moderate-dehydration decreased both femoral venous erythrocyte SOD activity (195 ± 6 vs. 180 ± 5 U/L, P < 0.05) and plasma isoprostanes (30 ± 1.1 vs. 25.9 ± 1.3 pg/L, P < 0.05), but during rehydration these were not different from control. In conclusion, these findings suggest that active skeletal muscles release GSH into the circulation under moderate dehydration and subsequent rehydration, possibly to enhance the antioxidant defense.

Hip joint torques during the golf swing of young and senior healthy males.

PubMed

Foxworth, Judy L; Millar, Audrey L; Long, Benjamin L; Way, Michael; Vellucci, Matthew W; Vogler, Joshua D

2013-09-01

Descriptive, laboratory study. To compare the 3-D hip torques during a golf swing between young and senior healthy male amateur golfers. The secondary purpose was to compare the 3-D hip joint torques between the trail leg and lead leg. The generation of hip torques from the hip musculature is an important aspect of the golf swing. Golf is a very popular activity, and estimates of hip torques during the golf swing have not been reported. Twenty healthy male golfers were divided into a young group (mean ± SD age, 25.1 ± 3.1 years) and a senior group (age, 56.9 ± 4.7 years). All subjects completed 10 golf swings using their personal driver. A motion capture system and force plates were used to obtain kinematic and kinetic data. Inverse dynamic analyses were used to calculate 3-D hip joint torques of the trail and lead limbs. Two-way analyses of covariance (group by leg), with club-head velocity as a covariate, were used to compare peak hip torques between groups and limbs. Trail-limb hip external rotator torque was significantly greater in the younger group compared to the senior group, and greater in the trail leg versus the lead leg. When adjusting for club-head velocity, young and senior healthy male amateur golfers generated comparable hip torques during a golf swing, with the exception of the trail-limb hip external rotator torque. The largest hip torque found was the trail-limb hip extensor torque.

The effects of low-repetition and light-load power training on bone mineral density in postmenopausal women with sarcopenia: a pilot study.

PubMed

Hamaguchi, Kanako; Kurihara, Toshiyuki; Fujimoto, Masahiro; Iemitsu, Motoyuki; Sato, Koji; Hamaoka, Takafumi; Sanada, Kiyoshi

2017-05-02

Age-related reduction in bone mineral density (BMD) is generally accelerated in women after menopause, and could be even more pronounced in individuals with sarcopenia. Light-load power training with a low number of repetitions would increase BMD, significantly reducing bone loss in individuals at risk of osteoporosis. This study investigated the effects of low-repetition, light-load power training on BMD in Japanese postmenopausal women with sarcopenia. The training group (n = 7) followed a progressive power training protocol that increased the load with a weighted vest, for two sessions per week, over the course of 6 weeks. The training exercise comprised five kinds of exercises (squats, front lunges, side lunges, calf raises, and toe raises), and each exercise contained eight sets of three repetitions with a 15-s rest between each set. The control group (n = 8) did not undergo any training intervention. We measured BMD, muscle strength, and anthropometric data. Within-group changes in pelvis BMD and knee extensor strength were significantly greater in the training group than the control group (p = 0.029 and 0.030 for pelvis BMD and knee extensor strength, respectively). After low-repetition, light-load power training, we noted improvements in pelvis BMD (1.6%) and knee extensor strength (15.5%). No significant within- or between-group differences were observed for anthropometric data or forearm BMD. Six weeks of low-repetition, light-load power training improved pelvis BMD and knee extensor strength in postmenopausal women with sarcopenia. Since this training program does not require high-load exercise and is therefore easily implementable as daily exercise, it could be an effective form of exercise for sedentary adults at risk for osteoporosis who are fearful of heavy loads and/or training that could cause fatigue. This trial was registered with the University Hospital Medical Information Network on 31 October 2016 ( UMIN000024651 ).

Partially irreversible paresis of the deep peroneal nerve caused by osteocartilaginous exostosis of the fibula without affecting the tibialis anterior muscle.

PubMed

Paprottka, Felix Julian; Machens, Hans-Günther; Lohmeyer, Jörn Andreas

2012-08-01

Dysfunction of the lower limb's muscles can cause severe impairment and immobilisation of the patient. As one of the leg's major motor and sensory nerves, the deep peroneal nerve (synonym: deep fibular nerve) plays a very important role in muscle innervation in the lower extremities. We report the case of a 19-year-old female patient, who suffered from a brace-like exostosis 6-cm underneath her left fibular head causing a partially irreversible paresis of her deep peroneal nerve. This nerve damage resulted in complete atrophy of her extensor digitorum longus and extensor hallucis longus muscle, and in painful sensory disturbance at her left shin and first web space. The tibialis anterior muscle stayed intact because its motor branch left the deep peroneal nerve proximal to the nerve lesion. Diagnosis was first verified 6 years after the onset of symptoms by a magnetic resonance imaging (MRI) scan of her complete left lower leg. Subsequently, the patient was operated on in our clinic, where a neurolysis was performed and the 4-cm-long osteocartilaginous exostosis was removed. Paralysis was already irreversible but sensibility returned completely after neurolysis. The presented case shows that an osteocartilaginous exostosis can be the cause for partial deep peroneal nerve paresis. If this disorder is diagnosed at an early stage, nerve damage is reversible. Typical for an exostosis is its first appearance during the juvenile growth phase. Copyright © 2012 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

Specificity of endurance, sprint and strength training on physical performance capacity in young athletes.

PubMed

Häkkinen, K; Mero, A; Kauhanen, H

1989-03-01

Three prebubescent athlete groups of endurance runners (E; n = 4), sprinters (S; n = 4) and weightlifters (WL; n = 4) and one control group (C; n = 6) as well as one junior but postpubescent weightlifter group (JWL; n = 6) volunteered as subjects in order to investigate specific effects of endurance, sprint and strength training on physical performance capacity during a 1 year follow-up period. The prepubescent E-group had higher (p less than 0.05) VO2 max (66.5 +/- 2.9 ml x kg1 x min-1) already at the beginning of the study than the other three groups. The prepubescent WL-group demonstrated greater (p less than 0.05) maximal muscular strength than the E-group and the WL-group increased its strength greatly by 21.4% (p less than 0.05) during the follow-up. No significant differences were observed in physical performance capacity between the prepubescent WL- and S-groups. Both groups demonstrated a slightly (ns.) better force-time curve recorded from the leg extensor muscles than the E-group and significant (p less than 0.05) increases occurred in these two groups in dynamic explosive performance during the follow-up. The postpubescent JWL-group demonstrated much greater (p less than 0.001) muscular mass and maximal strength than the prepubescent groups. No significant changes occurred in explosive types of performances in these athletes but significant (p less than 0.05) increase took place in the maximal neural activation and strength of the leg extensor muscles during the 1 year.(ABSTRACT TRUNCATED AT 250 WORDS)

EFFECTS OF STRENGTH TRAINING ON PHYSICAL FUNCTION: INFLUENCE OF POWER, STRENGTH, AND BODY COMPOSITION

PubMed Central

Hanson, Erik D.; Srivatsan, Sindhu R.; Agrawal, Siddhartha; Menon, Kalapurakkal S.; Delmonico, Matthew J.; Wang, Min Q.; Hurley, Ben F.

2010-01-01

The purpose of this study was to determine (a) the effects of strength training (ST) on physical function and (b) the influence of strength, power, muscle volume (MV), and body composition on physical function. Healthy, inactive adults (n = 50) aged 65 years and older underwent strength, power, total body composition (% fat and fat free mass [FFM]), and physical function testing before and after 22 weeks of ST. Physical function testing consisted of tasks designed to mimic common physical activities of daily living (ADL). To improve internal validity of the assessment of mid-thigh intermuscular fat, subcutaneous fat, and knee extensors MV, a 10-week unilateral ST program using the untrained leg as an internal control preceded 12 weeks of whole-body ST. Strength, power, and FFM increased significantly with ST (all p < 0.05), whereas rapid walk, 5 chair stands, and get up and go time decreased significantly with ST in the overall group (all p < 0.05). Women improved significantly in both walking test times (both p < 0.05) but not in the stair climb test, whereas men improved in the stair climb test (p < 0.05) but not in walking test times. Multiple regression analysis revealed the highest R2 (0.28) for the change in chair stands time, followed by stair climb and usual walk at 0.27 and 0.21, respectively. ST improves performance in functional tasks important for ADLs. Changes in strength, power, and FFM are predictors of ST-induced improvements in these tasks. PMID:19910811

A Novel Two-Velocity Method for Elaborate Isokinetic Testing of Knee Extensors.

PubMed

Grbic, Vladimir; Djuric, Sasa; Knezevic, Olivera M; Mirkov, Dragan M; Nedeljkovic, Aleksandar; Jaric, Slobodan

2017-09-01

Single outcomes of standard isokinetic dynamometry tests do not discern between various muscle mechanical capacities. In this study, we aimed to (1) evaluate the shape and strength of the force-velocity relationship of knee extensors, as observed in isokinetic tests conducted at a wide range of angular velocities, and (2) explore the concurrent validity of a simple 2-velocity method. Thirteen physically active females were tested for both the peak and averaged knee extensor concentric force exerted at the angular velocities of 30°-240°/s recorded in the 90°-170° range of knee extension. The results revealed strong (0.960

Lower Limb Symmetry: Comparison of Muscular Power Between Dominant and Nondominant Legs in Healthy Young Adults Associated With Single-Leg-Dominant Sports.

PubMed

Vaisman, Alex; Guiloff, Rodrigo; Rojas, Juan; Delgado, Iris; Figueroa, David; Calvo, Rafael

2017-12-01

Achieving a symmetrical power performance (difference <15%) between lower limbs is generally recommended during sports rehabilitation. However, athletes in single-leg-dominant sports, such as professional soccer players, could develop significant asymmetry between their dominant and nondominant legs, such that symmetry does not act as a viable comparison. To (1) compare maximal muscular power between the dominant and nondominant legs in healthy young adults, (2) evaluate the effect of a single-leg-dominant sport activity performed at the professional level, and (3) propose a parameter of normality for maximal power difference in the lower limbs of this young adult population. Controlled laboratory study. A total of 78 healthy, male, young adults were divided into 2 groups according to sport activity level. Group 1 consisted of 51 nonathletes (mean ± SD age, 20.8 ± 1.5 years; weight, 71.9 ± 10.5 kg) who participated in less than 8 hours a week of recreational physical activity with nonspecific training; group 2 consisted of 27 single-leg-dominant professional soccer players (age, 18.4 ± 0.6 years; weight, 70.1 ± 7.5 kg) who specifically trained and competed at their particular activity 8 hours or more a week. For assessment of maximal leg power, both groups completed the single-leg squat jump test. Dominance was determined when participants completed 2 of 3 specific tests with the same extremity. Statistical analysis included the Student t test. No statistical difference was found for maximal power between dominant and nondominant legs for nonathletes ( t = -1.01, P = .316) or single-leg-dominant professional soccer players ( t = -1.10, P = .281). A majority (95%) of participants studied showed a power difference of less than 15% between their lower extremities. Among young healthy adults, symmetrical power performance is expected between lower extremities independent of the existence of dominance and difference in sport activity level. A less than 15% difference in power seems to be a proper parameter to define symmetrical power performance assessed by vertical single-leg jump tests.

Alpha-actinin-3 (ACTN3) R577X polymorphism influences knee extensor peak power response to strength training in older men and women.

PubMed

Delmonico, Matthew J; Kostek, Matthew C; Doldo, Neil A; Hand, Brian D; Walsh, Sean; Conway, Joan M; Carignan, Craig R; Roth, Stephen M; Hurley, Ben F

2007-02-01

The alpha-actinin-3 (ACTN3) R577X polymorphism has been associated with muscle power performance in cross-sectional studies. We examined baseline knee extensor concentric peak power (PP) and PP change with approximately 10 weeks of unilateral knee extensor strength training (ST) using air-powered resistance machines in 71 older men (65 [standard deviation = 8] years) and 86 older women (64 [standard deviation = 9] years). At baseline in women, the XX genotype group had an absolute (same resistance) PP that was higher than the RR (p =.005) and RX genotype groups (p =.02). The women XX group also had a relative (70% of one-repetition maximum [1-RM]) PP that was higher than that in the RR (p =.002) and RX groups (p =.008). No differences in baseline absolute or relative PP were observed between ACTN3 genotype groups in men. In men, absolute PP change with ST in the RR (n = 16) group approached a significantly higher value than in the XX group (n = 9; p =.07). In women, relative PP change with ST in the RR group (n = 16) was higher than in the XX group (n = 17; p =.02). The results indicate that the ACTN3 R577X polymorphism influences the response of quadriceps muscle power to ST in older adults.

Comparison of isokinetic muscle strength and muscle power by types of warm-up.

PubMed

Sim, Young-Je; Byun, Yong-Hyun; Yoo, Jaehyun

2015-05-01

[Purpose] The purpose of this study was to clarify the influence of static stretching at warm-up on the isokinetic muscle torque (at 60°/sec) and muscle power (at 180°/sec) of the flexor muscle and extensor muscle of the knee joint. [Subjects and Methods] The subjects of this study were 10 healthy students with no medically specific findings. The warm-up group and warm-up with stretching group performed their respective warm-up prior to the isokinetic muscle torque evaluation of the knee joint. One-way ANOVA was performed by randomized block design for each variable. [Results] The results were as follows: First, the flexor peak torque and extensor peak torque of the knee joint tended to decrease at 60°/sec in the warm-up with stretching group compared with the control group and warm-up group, but without statistical significance. Second, extensor power at 180°/sec was also not statistically significant. However, it was found that flexor power increased significantly in the warm-up with stretching group at 180°/sec compared with the control group and warm-up group in which stretching was not performed. [Conclusion] Therefore, it is considered that in healthy adults, warm-up including two sets of stretching for 20 seconds per muscle group does not decrease muscle strength and muscle power.

Oral antioxidants improve leg blood flow during exercise in patients with chronic obstructive pulmonary disease

PubMed Central

Rossman, Matthew J.; Trinity, Joel D.; Garten, Ryan S.; Ives, Stephen J.; Conklin, Jamie D.; Barrett-O'Keefe, Zachary; Witman, Melissa A. H.; Bledsoe, Amber D.; Morgan, David E.; Runnels, Sean; Reese, Van R.; Zhao, Jia; Amann, Markus; Wray, D. Walter

2015-01-01

The consequence of elevated oxidative stress on exercising skeletal muscle blood flow as well as the transport and utilization of O2 in patients with chronic obstructive pulmonary disease (COPD) is not well understood. The present study examined the impact of an oral antioxidant cocktail (AOC) on leg blood flow (LBF) and O2 consumption during dynamic exercise in 16 patients with COPD and 16 healthy subjects. Subjects performed submaximal (3, 6, and 9 W) single-leg knee extensor exercise while LBF (Doppler ultrasound), mean arterial blood pressure, leg vascular conductance, arterial O2 saturation, leg arterial-venous O2 difference, and leg O2 consumption (direct Fick) were evaluated under control conditions and after AOC administration. AOC administration increased LBF (3 W: 1,604 ± 100 vs. 1,798 ± 128 ml/min, 6 W: 1,832 ± 109 vs. 1,992 ± 120 ml/min, and 9W: 2,035 ± 114 vs. 2,187 ± 136 ml/min, P < 0.05, control vs. AOC, respectively), leg vascular conductance, and leg O2 consumption (3 W: 173 ± 12 vs. 210 ± 15 ml O2/min, 6 W: 217 ± 14 vs. 237 ± 15 ml O2/min, and 9 W: 244 ± 16 vs 260 ± 18 ml O2/min, P < 0.05, control vs. AOC, respectively) during exercise in COPD, whereas no effect was observed in healthy subjects. In addition, the AOC afforded a small, but significant, improvement in arterial O2 saturation only in patients with COPD. Thus, these data demonstrate a novel beneficial role of AOC administration on exercising LBF, O2 consumption, and arterial O2 saturation in patients with COPD, implicating oxidative stress as a potential therapeutic target for impaired exercise capacity in this population. PMID:26188020

Injury of leg somatotopy of corticospinal tract at corona radiata by ventriculoperitoneal shunt

PubMed Central

Jang, Sung Ho; Kwon, Younghyeon

2018-01-01

Abstract Rationale: A 45-year-old right-handed female patient suffered head trauma after being hit by a truck that ran into a house. Patient concerns: The patient lost consciousness for 1 hour and experienced posttraumatic amnesia for 1 month after the accident. Diagnoses: She underwent conservative management for a subdural hematoma in the left frontotemporal lobes and intracerebral hematoma in the left frontal lobe. Interventions: The patient's Glasgow Coma Scale score was 11. She underwent a VP shunt operation, approached through the right posterior parietal area of the brain, at 4 months after onset. Approximately, 6 months after onset, she was admitted to the rehabilitation department of a university hospital. She presented with moderate weakness of the left leg: Medical Research Council scores: hip flexor; 3, knee extensor; 3+, ankle dorsiflexor; 3–. Brain magnetic resonance imaging revealed a leukomalactic lesion in the right posterior corona radiata along the shunt. Outcomes: On 6-month (2 months after the shunt operation) diffusion tensor tractography, the left CST showed partial injury in the posterior portion compared with the right CST. On 6-month transcranial magnetic stimulation study, the motor-evoked potential obtained at the left tibialis anterior muscle revealed lower amplitude than that on the right side. Lessons: Injury of leg somatotopy of a CST was demonstrated in a patient with leg weakness following a VP shunt operation. PMID:29517704

The Effects of Blood Flow Restricted Electrostimulation on Strength and Hypertrophy.

PubMed

Slysz, Joshua T; Burr, Jamie F

2018-05-22

The combined effect of neuromuscular electrical stimulation (NMES) and blood flow restriction (BFR) on muscle mass and strength has not been thoroughly investigated. To examine the effects of combined and independent BFR and a low-intensity NMES on skeletal muscle adaptation. Exploratory study. Laboratory. Twenty recreationally active subjects. Subjects had each leg randomly allocated to 1 of 4 possible intervention groups: (1) cyclic BFR alone, (2) NMES alone, (3) BFR + NMES, or (4) control. Each leg was stimulated in its respective intervention group for 32 minutes, 4 days per week for 6 weeks. Mean differences in size (in grams) and isometric strength (in kilograms), between week 0 and week 6, were calculated for each group. Leg strength increased 32 (19) kg in the BFR + NMES group, which differed from the 3 (11) kg change in the control group (P = .03). The isolated NMES and BFR groups revealed increases of 16 (28) kg and 18 (17) kg, respectively, but these did not statistically differ from the control, or one another. No alterations were statistically significant for leg size. Compared with a control that received no treatment, the novel combination of BFR and NMES led to increasing muscular strength of the knee extensors, but not muscle mass which had a large interindividual variability in response.

Injury of leg somatotopy of corticospinal tract at corona radiata by ventriculoperitoneal shunt: A case report.

PubMed

Jang, Sung Ho; Kwon, Younghyeon

2018-03-01

A 45-year-old right-handed female patient suffered head trauma after being hit by a truck that ran into a house. The patient lost consciousness for 1 hour and experienced posttraumatic amnesia for 1 month after the accident. She underwent conservative management for a subdural hematoma in the left frontotemporal lobes and intracerebral hematoma in the left frontal lobe. The patient's Glasgow Coma Scale score was 11. She underwent a VP shunt operation, approached through the right posterior parietal area of the brain, at 4 months after onset. Approximately, 6 months after onset, she was admitted to the rehabilitation department of a university hospital. She presented with moderate weakness of the left leg: Medical Research Council scores: hip flexor; 3, knee extensor; 3+, ankle dorsiflexor; 3-. Brain magnetic resonance imaging revealed a leukomalactic lesion in the right posterior corona radiata along the shunt. On 6-month (2 months after the shunt operation) diffusion tensor tractography, the left CST showed partial injury in the posterior portion compared with the right CST. On 6-month transcranial magnetic stimulation study, the motor-evoked potential obtained at the left tibialis anterior muscle revealed lower amplitude than that on the right side. Injury of leg somatotopy of a CST was demonstrated in a patient with leg weakness following a VP shunt operation.

Is stair climb power a clinically relevant measure of leg power impairments in at-risk older adults?

PubMed

Bean, Jonathan F; Kiely, Dan K; LaRose, Sharon; Alian, Joda; Frontera, Walter R

2007-05-01

To test the clinical relevance of the stair climb power test (SCPT) as a measure of leg power impairments in mobility-limited older adults. Cross-sectional analysis of baseline data from participants within a randomized controlled trial. Rehabilitation research gym. Community-dwelling older adults (N=138; mean age, 75.4 y) with mobility limitations as defined by the Short Physical Performance Battery (SPPB). Not applicable. Leg power measures included the SCPT and double leg press power measured at 40% (DLP40) and 70% (DLP70) of the 1 repetition maximum. Mobility performance tests included the SPPB and its 3 components: gait speed, chair stand time, and standing balance. Stair climb power per kilogram (SCP/kg) had correlations of moderate strength (r=.47, r=.52) with DLP40/kg and DLP70/kg, respectively. All 3 leg power measures correlated with each of the mobility performance measures with the exception of DLP40/kg (r=.11, P=.27) and DLP70/kg (r=.11, P=.18) with standing balance. Magnitudes of association, as described by the Pearson correlation coefficient, did not differ substantively among the separate power measures as they related to SPPB performance overall. Separate adjusted multivariate models evaluating the relationship between leg power and SPPB performance were all statistically significant and described equivalent amounts of the total variance (R(2)) in SPPB performance (SCP/kg, R(2)=.30; DLP40, R(2)=.32; DLP70, R(2)=.31). Analyses of the components of the SPPB show that the SCPT had stronger associations than the other leg power impairment measures with models predicting chair stand (SCP/kg, R(2)=.25; DLP40, R(2)=.12; DLP70, R(2)=.13), whereas both types of leg press power testing had stronger associations with models predicting gait speed (SCP/kg, R(2)=.16; DLP40, R(2)=.34; DLP70, R(2)=.34). Stair climb power was the only power measure that was a significant component of models predicting standing balance (SCP/kg R(2)=.20). The SCPT is a clinically relevant measure of leg power impairments. It is associated with more complex modes of testing leg power impairments and is meaningfully associated with mobility performance, making it suitable for clinical settings in which impairment-mobility relationships are of interest.

The re-establishment of the normal blood lactate response to exercise in humans after prolonged acclimatization to altitude

PubMed Central

van Hall, G; Calbet, J A L; Søndergaard, H; Saltin, B

2001-01-01

One to five weeks of chronic exposure to hypoxia has been shown to reduce peak blood lactate concentration compared to acute exposure to hypoxia during exercise, the high altitude ‘lactate paradox’. However, we hypothesize that a sufficiently long exposure to hypoxia would result in a blood lactate and net lactate release from the active leg to an extent similar to that observed in acute hypoxia, independent of work intensity. Six Danish lowlanders (25–26 years) were studied during graded incremental bicycle exercise under four conditions: at sea level breathing either ambient air (0 m normoxia) or a low-oxygen gas mixture (10 % O2 in N2, 0 m acute hypoxia) and after 9 weeks of acclimatization to 5260 m breathing either ambient air (5260 m chronic hypoxia) or a normoxic gas mixture (47 % O2 in N2, 5260 m acute normoxia). In addition, one-leg knee-extensor exercise was performed during 5260 m chronic hypoxia and 5260 m acute normoxia. During incremental bicycle exercise, the arterial lactate concentrations were similar at sub-maximal work at 0 m acute hypoxia and 5260 m chronic hypoxia but higher compared to both 0 m normoxia and 5260 m acute normoxia. However, peak lactate concentration was similar under all conditions (10.0 ± 1.3, 10.7 ± 2.0, 10.9 ± 2.3 and 11.0 ± 1.0 mmol l−1) at 0 m normoxia, 0 m acute hypoxia, 5260 m chronic hypoxia and 5260 m acute normoxia, respectively. Despite a similar lactate concentration at sub-maximal and maximal workload, the net lactate release from the leg was lower during 0 m acute hypoxia (peak 8.4 ± 1.6 mmol min−1) than at 5260 m chronic hypoxia (peak 12.8 ± 2.2 mmol min−1). The same was observed for 0 m normoxia (peak 8.9 ± 2.0 mmol min−1) compared to 5260 m acute normoxia (peak 12.6 ± 3.6 mmol min−1). Exercise after acclimatization with a small muscle mass (one-leg knee-extensor) elicited similar lactate concentrations (peak 4.4 ± 0.2 vs. 3.9 ± 0.3 mmol l−1) and net lactate release (peak 16.4 ± 1.8 vs. 14.3 mmol l−1) from the active leg at 5260 m chronic hypoxia and 5260 m acute normoxia. In conclusion, in lowlanders acclimatized for 9 weeks to an altitude of 5260 m, the arterial lactate concentration was similar at 0 m acute hypoxia and 5260 m chronic hypoxia. The net lactate release from the active leg was higher at 5260 m chronic hypoxia compared to 0 m acute hypoxia, implying an enhanced lactate utilization with prolonged acclimatization to altitude. The present study clearly shows the absence of a lactate paradox in lowlanders sufficiently acclimatized to altitude. PMID:11691888

Effects of Progressive Resistance Strength Training on Knee Biomechanics During Single Leg Step-up in Persons with Mild Knee Osteoarthritis

PubMed Central

McQuade, Kevin James; de Oliveira, Anamaria Siriani

2011-01-01

Background The goal of this study was to determine if increasing strength in primary knee extensors and flexors would directly affect net knee joint moments during a common functional task in persons with knee osteoarthritis. Methods An exploratory single sample clinical trial with pre-post treatment measures was used to study volunteers with clinical diagnosis of mild knee OA in one knee. Subjects participated in an individually supervised training program 3 times a week for eight weeks consisting of progressive resistive exercises for knee extensors and knee flexors. Pre and post training outcome assessments included: 1. Net internal knee joint moments, 2. Electromyography of primary knee extensors and flexors, and 3. Self-report measures of knee pain and function. The distribution of lower extremity joint moments as a percent of the total support moment was also investigated. Findings Pain, symptoms, activities of daily life, quality of life, stiffness, and function scores showed significant improvement following strength training. Knee internal valgus and hip internal rotation moments showed increasing but non-statistically significant changes post-training. There were no significant differences in muscle co-contraction activation of the Quadriceps and Hamstrings. Interpretations While exercise continues to be an important element of OA management, the results of this study suggest improvements in function, pain, and other symptoms, as a result of strength training may not be causally related to specific biomechanical changes in net joint moments. PMID:21514018

Relationship between Muscle Function, Muscle Typology and Postural Performance According to Different Postural Conditions in Young and Older Adults

PubMed Central

Paillard, Thierry

2017-01-01

Although motor output of the postural function clearly influences postural performance in young and older subjects, no relationship has been formally established between them. However, the relationship between lower-extremity muscle strength/power and postural performance is often pointed out, especially in older subjects. In fact, the influence of motor output may vary according to the postural condition considered (e.g., static, dynamic, challenging, disturbing). In static postural condition, there may be a relationship between lower-extremity muscle strength and postural performance when the value of muscle strength is below a certain threshold in older subjects. Above this threshold of muscle strength, this relationship may disappear. In dynamic postural condition, lower-extremity muscle power could facilitate compensatory postural actions, limiting induced body imbalance likely to generate falls in older subjects. In young subjects, there could be a relationship between very early rapid torque of the leg extensor muscles and postural performance. In the case of postural reaction to (external) perturbations, a high percentage of type II muscle fibers could be associated with the ability to react quickly to postural perturbations in young subjects, while it may enable a reduction in the risk of falls in older subjects. In practice, in older subjects, muscle strength and/or power training contributes to reducing the risk of falls, as well as slowing down the involution of muscle typology regarding type II muscle fibers. PMID:28861000

Relationship between Muscle Function, Muscle Typology and Postural Performance According to Different Postural Conditions in Young and Older Adults.

PubMed

Paillard, Thierry

2017-01-01

Although motor output of the postural function clearly influences postural performance in young and older subjects, no relationship has been formally established between them. However, the relationship between lower-extremity muscle strength/power and postural performance is often pointed out, especially in older subjects. In fact, the influence of motor output may vary according to the postural condition considered (e.g., static, dynamic, challenging, disturbing). In static postural condition, there may be a relationship between lower-extremity muscle strength and postural performance when the value of muscle strength is below a certain threshold in older subjects. Above this threshold of muscle strength, this relationship may disappear. In dynamic postural condition, lower-extremity muscle power could facilitate compensatory postural actions, limiting induced body imbalance likely to generate falls in older subjects. In young subjects, there could be a relationship between very early rapid torque of the leg extensor muscles and postural performance. In the case of postural reaction to (external) perturbations, a high percentage of type II muscle fibers could be associated with the ability to react quickly to postural perturbations in young subjects, while it may enable a reduction in the risk of falls in older subjects. In practice, in older subjects, muscle strength and/or power training contributes to reducing the risk of falls, as well as slowing down the involution of muscle typology regarding type II muscle fibers.

Do patients with knee osteoarthritis perform sit-to-stand motion efficiently?

PubMed

Anan, Masaya; Shinkoda, Koichi; Suzuki, Kentaro; Yagi, Masahide; Ibara, Takuya; Kito, Nobuhiro

2015-02-01

The sit-to-stand motion (STS) is a frequently executed activity that is affected by weakness in the quadriceps femoris muscle and knee joint pain in patients with knee osteoarthritis (OA). We investigated whether patients with knee OA can efficiently perform STS through mechanical energy transfer assessments. Participants were 20 women with knee OA and 17 age-matched asymptomatic controls. The center of mass (COM), segment angles, joint moments, and powers during STS were measured. The negative mechanical work in the proximal portion of the shank, negative mean powers in the distal portion of the pelvis and proximal portion of the shank, and the positive mean power in the proximal and distal portions of the thigh were significantly lower in the knee OA group than in the control group. Patients with knee OA primarily performed thoracic forward lean movement, shifting their COM closer to the base of support provided by the feet alone, in an attempt to achieve stability at and after buttocks-off. However, control ability, which generates and absorbs kinetic energy quickly, was not enhanced in these patients, and their motion was unable to increase absorption of the mechanical energy in hip extensors and reduce the load on knee extensors. Furthermore, STS in patients with knee OA had reduced energy absorption in the knee extensors from the shank forward lean movement after buttocks-off, had reduced knee extensor efficiency, and made greater use of physiological energy. These findings suggest that, from the standpoint of mechanical energy transfer, patients with knee OA do not perform STS efficiently. Copyright © 2014 Elsevier B.V. All rights reserved.

Improved Exercise Tolerance with Caffeine Is Associated with Modulation of both Peripheral and Central Neural Processes in Human Participants.

PubMed

Bowtell, Joanna L; Mohr, Magni; Fulford, Jonathan; Jackman, Sarah R; Ermidis, Georgios; Krustrup, Peter; Mileva, Katya N

2018-01-01

Caffeine has been shown to enhance exercise performance and capacity. The mechanisms remain unclear but are suggested to relate to adenosine receptor antagonism, resulting in increased central motor drive, reduced perception of effort, and altered peripheral processes such as enhanced calcium handling and extracellular potassium regulation. Our aims were to investigate how caffeine (i) affects knee extensor PCr kinetics and pH during repeated sets of single-leg knee extensor exercise to task failure and (ii) modulates the interplay between central and peripheral neural processes. We hypothesized that the caffeine-induced extension of exercise capacity during repeated sets of exercise would occur despite greater disturbance of the muscle milieu due to enhanced peripheral and corticospinal excitatory output, central motor drive, and muscle contractility. Nine healthy active young men performed five sets of intense single-leg knee extensor exercise to task failure on four separate occasions: for two visits (6 mg·kg -1 caffeine vs placebo), quadriceps 31 P-magnetic resonance spectroscopy scans were performed to quantify phosphocreatine kinetics and pH, and for the remaining two visits (6 mg·kg -1 caffeine vs placebo), femoral nerve electrical and transcranial magnetic stimulation of the quadriceps cortical motor area were applied pre- and post exercise. The total exercise time was 17.9 ± 6.0% longer in the caffeine (1,225 ± 86 s) than in the placebo trial (1,049 ± 73 s, p  = 0.016), and muscle phosphocreatine concentration and pH ( p < 0.05) were significantly lower in the latter sets of exercise after caffeine ingestion. Voluntary activation (VA) (peripheral, p  = 0.007; but not supraspinal, p  = 0.074), motor-evoked potential (MEP) amplitude ( p  = 0.007), and contractility (contraction time, p  = 0.009; and relaxation rate, p  = 0.003) were significantly higher after caffeine consumption, but at task failure MEP amplitude and VA were not different from placebo. Caffeine prevented the reduction in M-wave amplitude that occurred at task failure ( p  = 0.039). Caffeine supplementation improved high-intensity exercise tolerance despite greater-end exercise knee extensor phosphocreatine depletion and H + accumulation. Caffeine-induced increases in central motor drive and corticospinal excitability were attenuated at task failure. This may have been induced by the afferent feedback of the greater disturbance of the muscle milieu, resulting in a stronger inhibitory input to the spinal and supraspinal motor neurons. However, causality needs to be established through further experiments.

Butterfly Sprint Swimming Technique, Analysis of Somatic and Spatial-Temporal Coordination Variables

PubMed Central

Stanula, Arkadiusz; Krężałek, Piotr; Ostrowski, Andrzej; Kaca, Marcin; Głąb, Grzegorz

2017-01-01

Abstract The aim of this study was to investigate somatic properties and force production of leg extensor muscles measured in the countermovement jump test (CMJ), as well as to analyse kinematic variables of sprint surface butterfly swimming. Thirty-four male competitive swimmers were recruited with an average age of 19.3 ± 1.83 years. Their average body height (BH) was 183.7 ± 5.93 cm, body fat content 10.8 ± 2.64% and body mass (BM) 78.3 ± 5.0 kg. Length measurements of particular body segments were taken and a counter movement jump (CMJ) as well as an all-out 50 m butterfly speed test were completed. The underwater movements of the swimmers’ bodies were recorded with a digital camera providing side-shots. We registered a significant relationship between body mass (r = 0.46), lean body mass (r = 0.48) and sprint surface butterfly swimming (VSBF). The anaerobic power measured in the CMJ test, total body length (TBL) as well as upper and lower extremity length indices did not influence swimming speed significantly. The temporal entry-kick index (the time ratio between the first kick and arm entry) significantly influenced VSBF (r = -0.45). Similarly, medium power of the coefficient was indicated between a) stroke rate kinematics (SR), b) duration of the first leg kick (LP1), c) air phase duration of arm recovery (Fly-arm), and VSBF (r = 0.40; r = 0.40 and r = 0.41, respectively). The entry-kick temporal index showed that, in the butterfly cycle, an appropriately early executed initial kick when compared to arm entry was associated with a longer arm propulsion phase, which in turn was associated with minimizing resistive gliding phases and enabled relatively longer and less resistive air arm recovery (higher value of the fly-arm index). The higher value of SR kinematic was another important element of the best butterfly results in this study. PMID:29339985

Characteristics and Preliminary Observations of the Influence of Electromyostimulation on the Size and Function of Human Skeletal Muscle During 30 Days of Simulated Microgravity

NASA Technical Reports Server (NTRS)

Duvoisin, Marc R.; Convertino, Victor A; Buchanan, Paul; Gollinick, Philip D.; Dudley, Gary A.

1989-01-01

During 30 days (d) of bedrest, the practicality of using Elec- troMyoStimulation (EMS) as a deterrent to atrophy and strength loss of lower limb musculature was examined. An EMS system was developed that provided variable but quantifiable levels of EMS, and measured torque. The dominant log of three male subjects was stimulated twice daily in a 3-d on/1-d off cycle during bedrest. The non-dominant leg of each subject acted as a control. A stimulator, using a 0.3 ms monophasic 60 Hz pulse waveform, activated muscle tissue for 4 s. The output waveform from the stimulator was sequenced to the Knee Extensors (KE), Knee Flex- ors (KF), Ankle Extensors (AE), and Ankle Flexors (AF), and caused three isometric contractions of each muscle group per minute. Subject tolerance determined EMS Intensity. Each muscle group received four 5-min bouts of EMS each session with a 10 -min rest between bouts. EMS and torque levels for each muscle action were recorded directly an a computer. Overall average EMS Intensity was 197, 197, 195, and 188 mA for the KE, KF, AF, and AE, respectively. Overall average torque development for these muscle groups was 70, 16, 12, and 27 Nm, respectively. EMS intensity doubled during the study, and average torque increased 2.5 times. Average maximum torque throughout a session reached 54% of maximal voluntary for the KE and 29% for the KF. Reductions in leg volume, muscle compartment size, cross-sectional area of slow and fast-twitch fibers, strength, and aerobic enzyme activities, and increased log compliance were attenuated in the legs which received EMS during bedrest. These results indicate that similar EMS levels induce different torques among different muscle groups and that repeated exposure to EMS increases tolerance and torque development. Longer orien- tation periods, therefore, may enhance its effectiveness. Our preliminary data suggest that the efficacy of EMS as an effective countermeasure for muscle atrophy and strength loss during long duration space travel warrants further investigation.

Explosive Strength Imbalances in Professional Basketball Players

PubMed Central

Schiltz, Marc; Lehance, Cédric; Maquet, Didier; Bury, Thierry; Crielaard, Jean-Michel; Croisier, Jean-Louis

2009-01-01

Context: Despite the high rate of lower limb injuries in basketball players, studies of the dominant-limb effect in elite athletes often neglect injury history. Objective: To determine lower limb explosive-strength asymmetries in professional basketball players compared with junior basketball players and control participants. Design: Cohort study. Setting: Academic medical institution. Patients or Other Participants: 15 professional basketball players, 10 junior basketball players, and 20 healthy men. Main Outcome Measure(s): We performed an isokinetic examination to evaluate the knee extensor (Ext) and flexor (Fl) concentric peak torque at 60°·s−1 and 240°·s−1 and (Fl only) eccentric peak torque at 30°·s−1 and 120°·s−1. Functional evaluation included countermovement jump, countermovement jump with arms, 10-m sprint, single-leg drop jump, and single-leg, 10-second continuous jumping. Variables were compared among groups using analysis of variance or a generalized linear mixed model for bilateral variables. Results: The 2 groups of basketball players demonstrated better isokinetic and functional performances than the control group did. No differences in functional or relative isokinetic variables were noted between professional and junior basketball players. Professional players with a history of knee injury failed to reach normal knee extensor strength at 60°·s−1. Knee Ext (60°·s−1) and Fl (eccentric 120°·s−1) torque values as well as 10-second continuous jumping scores were higher in those professional players without a history of knee injury than those with such a history. Compared with the group without a history of knee injury, the group with a history of knee injury maintained leg asymmetry ratios greater than 10% for almost all isokinetic variables and more than 15% for unilateral functional variables. Conclusions: The relative isokinetic and functional performances of professional basketball players were similar to those of junior players, with no dominant-side effect. A history of knee injury in the professional athlete, however, was reflected in bilateral isokinetic and functional asymmetries and should be considered in future studies of explosive strength. PMID:19180217

Greater Hip Extension but Not Hip Abduction Explosive Strength Is Associated With Lesser Hip Adduction and Knee Valgus Motion During a Single-Leg Jump-Cut

PubMed Central

Cronin, Baker; Johnson, Samuel T.; Chang, Eunwook; Pollard, Christine D.; Norcross, Marc F.

2016-01-01

Background: The relationships between hip abductor and extensor strength and frontal plane hip and knee motions that are associated with anterior cruciate ligament injury risk are equivocal. However, previous research on these relationships has evaluated relatively low-level movement tasks and peak torque rather than a time-critical strength measure such as the rate of torque development (RTD). Hypothesis: Females with greater hip abduction and extension RTD would exhibit lesser frontal plane hip and knee motion during a single-leg jump-cutting task. Study Design: Descriptive laboratory study. Methods: Forty recreationally active females performed maximal isometric contractions and single-leg jump-cuts. From recorded torque data, hip extension and abduction RTD was calculated from torque onset to 200 ms after onset. Three-dimensional motion analysis was used to quantify frontal plane hip and knee kinematics during the movement task. For each RTD measure, jump-cut biomechanics were compared between participants in the highest (high) and lowest (low) RTD tertiles. Results: No differences in frontal plane hip and knee kinematics were identified between high and low hip abduction RTD groups. However, those in the high hip extension RTD group exhibited lower hip adduction (high, 3.8° ± 3.0°; low, 6.5° ± 3.0°; P = .019) and knee valgus (high, –2.5° ± 2.3°; low, –4.4° ± 3.2°; P = .046) displacements during the jump-cut. Conclusion: In movements such as cutting that are performed with the hip in a relatively abducted and flexed position, the ability of the gluteus medius to control hip adduction may be compromised. However, the gluteus maximus, functioning as a hip abductor, may take on a pivotal role in controlling hip adduction and knee valgus motion during these types of tasks. Clinical Relevance: Training with a specific emphasis on increasing explosive strength of the hip extensors may be a means through which to improve frontal plane hip and knee control during high-risk maneuvers such as cutting. PMID:27104207

Utilization of stored elastic energy in leg extensor muscles by men and women.

PubMed

Komi, P V; Bosco, C

1978-01-01

An alternating cycle of eccentric-concentric contractions in locomotion represents a sequence when storage and utilization of elastic energy takes place. It is possible that this storage capacity and its utilization depends on the imposed stretch loads in activated muscles, and that sex differences may be present in these phenomena. To investigate these assumed differences, subjects from both sexes and of good physical condition performed vertical jumps on the force-platform from the following experimental conditions: squatting jump (SJ) from a static starting position; counter-movement jump (CMJ) from a free standing position and with a preparatory counter-movement; drop jumps (DJ) from the various heights (20 to 100 cm) on to the platform followed immediately by a vertical jump. In all subjects the SJ, in which condition no appreciable storage of elastic energy takes place, produced the lowest height of rise of the whole body center of gravity (C.G.). The stretch load (drop height) influenced the performance so that height of rise of C. of G. increased when the drop height increased from 26 up to 62 cm (males) and from 20 to 50 cm (females). In all jumping conditions the men jumped higher than the women. However, examination of the utilization of elastic energy indicated that in CMJ the female subjects were able to utilize most (congruent to 90%) of the energy produced in the prestretching phase. Similarly, in DJ the overall change in positive energy over SJ condition was higher in women as compared to men. Thus the results suggest that although the leg extensor muscles of the men subjects could sustain much higher stretch loads, the females may be able to utilize a greater portion of the stored elastic energy in jumping activities.

Age-related degeneration in leg-extensor muscle-tendon units decreases recovery performance after a forward fall: compensation with running experience.

PubMed

Karamanidis, Kiros; Arampatzis, Adamantios

2007-01-01

The goals of this study were to investigate whether the lower muscle-tendon units (MTUs) capacities in older affect their ability to recover balance with a single-step after a fall, and to examine whether running experience enhances and protects this motor skill in young and old adults. The investigation was conducted on 30 older and 19 younger divided into two subgroups: runners versus non-active. In previous studies we documented that the older had lower leg extensor muscle strength and tendon stiffness while running had no effect on MTUs capacities. The current study examined recovery mechanics of the same individuals after an induced forward fall. Younger were better able to recover balance with a single-step compared to older (P < 0.001); this ability was associated with a more effective body configuration at touchdown (more posterior COM position relative to the recovery foot, P <0.001). MTUs capacities classified 88.6% of the subjects into single- or multiple-steppers. Runners showed a superior ability to recover balance with a single-step (P < 0.001) compared to non-active subjects due to a more effective mechanical response during the stance phase (greater knee joint flexion, P <0.05). We concluded that the age-related degeneration of the MTUs significantly diminished the older adults' ability to restore balance with a single-step. Running seems to enhance and protect this motor skill. We suggested that runners, due to their running experience, could update the internal representation of mechanisms responsible for the control of dynamic stability during a forward fall and, thus, were able to restore balance more often with a single-step compared to the non-active subjects.

Effects of strength training on muscle strength characteristics, functional capabilities, and balance in middle-aged and older women.

PubMed

Holviala, Jarkko H S; Sallinen, Janne M; Kraemer, William J; Alen, Markku J; Häkkinen, Keijo K T

2006-05-01

Progressive strength training can lead to substantial increases in maximal strength and mass of trained muscles, even in older women and men, but little information is available about the effects of strength training on functional capabilities and balance. Thus, the effects of 21 weeks of heavy resistance training--including lower loads performed with high movement velocities--twice a week on isometric maximal force (ISOmax) and force-time curve (force produced in 500 milliseconds, F0-500) and dynamic 1 repetition maximum (1RM) strength of the leg extensors, 10-m walking time (10WALK) and dynamic balance test (DYN.D) were investigated in 26 middle-aged (MI; 52.8 +/- 2.4 years) and 22 older women (O; 63.8 +/- 3.8 years). 1RM, ISOmax, and F0-500 increased significantly in MI by 28 +/- 10%, 20 +/- 19%, 31 +/- 34%, and in O by 27 +/- 8%, 20 +/- 16%, 18 +/- 45%, respectively. 10WALK (MI and O, p < 0.001) shortened and DYN.D improved (MI and O, p < 0.001). The present strength-training protocol led to large increases in maximal and explosive strength characteristics of leg extensors and in walking speed, as well to an improvement in the present dynamic balance test performance in both age groups. Although training-induced increase in explosive strength is an important factor for aging women, there are other factors that contribute to improvements in dynamic balance capacity. This study indicates that total body heavy resistance training, including explosive dynamic training, may be applied in rehabilitation or preventive exercise protocols in aging women to improve dynamic balance capabilities.

Effect of knee flexion angle on ground reaction forces, knee moments and muscle co-contraction during an impact-like deceleration landing: implications for the non-contact mechanism of ACL injury.

PubMed

Podraza, Jeffery T; White, Scott C

2010-08-01

Investigating landing kinetics and neuromuscular control strategies during rapid deceleration movements is a prerequisite to understanding the non-contact mechanism of ACL injury. The purpose of this study was to quantify the effect of knee flexion angle on ground reaction forces, net knee joint moments, muscle co-contraction and lower extremity muscles during an impact-like, deceleration task. Ground reaction forces and knee joint moments were determined from video and force plate records of 10 healthy male subjects performing rapid deceleration single leg landings from a 10.5 cm height with different degrees of knee flexion at landing. Muscle co-contraction was based on muscle moments calculated from an EMG-to-moment processing model. Ground reaction forces and co-contraction indices decreased while knee extensor moments increased significantly with increased degrees of knee flexion at landing (all p<0.005). Higher ground reaction forces when landing in an extended knee position suggests they are a contributing factor in non-contact ACL injuries. Increased knee extensor moments and less co-contraction with flexed knee landings suggest that quadriceps overload may not be the primary cause of non-contact ACL injuries. The results bring into question the counterbalancing role of the hamstrings during dynamic movements. The soleus may be a valuable synergist stabilizing the tibia against anterior translation at landing. Movement strategies that lessen the propagation of reaction forces up the kinetic chain may help prevent non-contact ACL injuries. The relative interaction of all involved thigh and lower leg muscles, not just the quadriceps and hamstrings should be considered when interpreting non-contact ACL injury mechanisms. Copyright 2010 Elsevier B.V. All rights reserved.

Propulsion phase of the single leg triple hop test in women with patellofemoral pain syndrome: a biomechanical study.

PubMed

Bley, Andre Serra; Correa, João Carlos Ferrari; Dos Reis, Amir Curcio; Rabelo, Nayra Deise Dos Anjos; Marchetti, Paulo Henrique; Lucareli, Paulo Roberto Garcia

2014-01-01

Asymmetry in the alignment of the lower limbs during weight-bearing activities is associated with patellofemoral pain syndrome (PFPS), caused by an increase in patellofemoral (PF) joint stress. High neuromuscular demands are placed on the lower limb during the propulsion phase of the single leg triple hop test (SLTHT), which may influence biomechanical behavior. The aim of the present cross-sectional study was to compare kinematic, kinetic and muscle activity in the trunk and lower limb during propulsion in the SLTHT using women with PFPS and pain free controls. The following measurements were made using 20 women with PFPS and 20 controls during propulsion in the SLTHT: kinematics of the trunk, pelvis, hip, and knee; kinetics of the hip, knee and ankle; and muscle activation of the gluteus maximus (GM), gluteus medius (GMed), biceps femoris (BF) and vastus lateralis (VL). Differences between groups were calculated using three separate sets of multivariate analysis of variance for kinematics, kinetics, and electromyographic data. Women with PFPS exhibited ipsilateral trunk lean; greater trunk flexion; greater contralateral pelvic drop; greater hip adduction and internal rotation; greater ankle pronation; greater internal hip abductor and ankle supinator moments; lower internal hip, knee and ankle extensor moments; and greater GM, GMed, BL, and VL muscle activity. The results of the present study are related to abnormal movement patterns in women with PFPS. We speculated that these findings constitute strategies to control a deficient dynamic alignment of the trunk and lower limb and to avoid PF pain. However, the greater BF and VL activity and the extensor pattern found for the hip, knee, and ankle of women with PFPS may contribute to increased PF stress.

Propulsion Phase of the Single Leg Triple Hop Test in Women with Patellofemoral Pain Syndrome: A Biomechanical Study

PubMed Central

Bley, Andre Serra; Correa, João Carlos Ferrari; Reis, Amir Curcio Dos; Rabelo, Nayra Deise Dos Anjos; Marchetti, Paulo Henrique; Lucareli, Paulo Roberto Garcia

2014-01-01

Asymmetry in the alignment of the lower limbs during weight-bearing activities is associated with patellofemoral pain syndrome (PFPS), caused by an increase in patellofemoral (PF) joint stress. High neuromuscular demands are placed on the lower limb during the propulsion phase of the single leg triple hop test (SLTHT), which may influence biomechanical behavior. The aim of the present cross-sectional study was to compare kinematic, kinetic and muscle activity in the trunk and lower limb during propulsion in the SLTHT using women with PFPS and pain free controls. The following measurements were made using 20 women with PFPS and 20 controls during propulsion in the SLTHT: kinematics of the trunk, pelvis, hip, and knee; kinetics of the hip, knee and ankle; and muscle activation of the gluteus maximus (GM), gluteus medius (GMed), biceps femoris (BF) and vastus lateralis (VL). Differences between groups were calculated using three separate sets of multivariate analysis of variance for kinematics, kinetics, and electromyographic data. Women with PFPS exhibited ipsilateral trunk lean; greater trunk flexion; greater contralateral pelvic drop; greater hip adduction and internal rotation; greater ankle pronation; greater internal hip abductor and ankle supinator moments; lower internal hip, knee and ankle extensor moments; and greater GM, GMed, BL, and VL muscle activity. The results of the present study are related to abnormal movement patterns in women with PFPS. We speculated that these findings constitute strategies to control a deficient dynamic alignment of the trunk and lower limb and to avoid PF pain. However, the greater BF and VL activity and the extensor pattern found for the hip, knee, and ankle of women with PFPS may contribute to increased PF stress. PMID:24830289

Four weeks one-leg training and high fat diet does not alter PPARalpha protein or mRNA expression in human skeletal muscle.

PubMed

Helge, J W; Bentley, D; Schjerling, P; Willer, M; Gibala, M J; Franch, J; Tapia-Laliena, M A; Daugaard, J R; Andersen, J L

2007-09-01

Fatty acid metabolism is influenced by training and diet with exercise training mediating this through activation of nuclear hormone receptor peroxisome proliferator-activated receptor alpha (PPARalpha) in skeletal muscle. This study investigated the effect of training and high fat or normal diet on PPARalpha expression in human skeletal muscle. Thirteen men trained one leg (T) four weeks (31.5 h in total), while the other leg (UT) served as control. During the 4 weeks six subjects consumed high fat (FAT) diet and seven subjects maintained a normal (CHO) diet. Biopsies were obtained from vastus lateralis muscle in both legs before and after training. After the biopsy, one-leg extension exercise was performed in random order with both legs 30 min at 95% of workload max. A training effect was evident as citrate synthase activity increased (P < 0.05) by 15% in the trained, but not the control leg in both groups. During exercise respiratory exchange ratio was lower in FAT (0.86 +/- 0.01, 0.83 +/- 0.01, mean +/- SEM) than CHO (0.96 +/- 0.02, 0.94 +/- 0.03) and in UT than T legs, respectively. The PPARalpha protein (144 +/- 44, 104 +/- 28, 79 +/- 15, 79 +/- 14, % of pre level) and PPARalpha mRNA (69 +/- [2, 2], 78 +/- [7, 6], 92 +/- [22, 18], 106 +/- [21, 18], % of pre level, geometric mean +/- SEM) expression remained unchanged by diet and training in FAT (UT, T) and CHO (UT, T), respectively. After the training and diet CS, HAD, PPARalpha, UCP2, UCP3 and mFABP mRNA content remained unchanged, whereas GLUT4 mRNA was lower in both groups and LDHA mRNA was lower (P < 0.05) only in FAT. 4 weeks one leg knee extensor training did not affect PPARalpha protein or mRNA expression. Furthermore, higher fat oxidation during exercise after fat rich diet was not accompanied by an increased PPARalpha protein or mRNA expression after 4 weeks.

Synthesis of amino acids in weight bearing and non-weight bearing leg muscles of suspended rats

NASA Technical Reports Server (NTRS)

Tischler, M. E.; Jaspers, S. R.

1982-01-01

The effect of hypokinesia (HYP) for 6 days on the de novo synthesis of glutamine (GLN) and glutamate (GLU), and of alanine was tested in isolated leg muscles of intact, adrenalectomized (ADX) and ADX cortisol-treated rats. The net synthesis of GLN and GLU was lower in soleus muscles of HYP animals of these three groups of rats. The synthesis of alanine was lowered by HYP in ADX animals and apparently raised by HYP in ADX cortisol-treated rats. No HYP effect was seen in the extensor digitorum longus (EDL) muscles of these animals. Although ADX lowered the synthesis of GLN and GLU in soleus muscles of control rats, while cortisol treatment restored this process to near normal, neither ADX nor cortisol treatment produced any effect in the HYP animals. However, effects of ADX and cortisol treatment on synthesis of GLN and GLU in EDL muscles and of alanine in both muscles seemed normal in HYP animals.

Poor correlation between handgrip strength and isokinetic performance of knee flexor and extensor muscles in community-dwelling elderly women.

PubMed

Felicio, Diogo Carvalho; Pereira, Daniele Sirineu; Assumpção, Alexandra Miranda; de Jesus-Moraleida, Fabianna Resende; de Queiroz, Barbara Zille; da Silva, Juscelio Pereira; de Brito Rosa, Naysa Maciel; Dias, João Marcos Domingues; Pereira, Leani Souza Máximo

2014-01-01

To investigate the correlation between handgrip strength and performance of knee flexor and extensor muscles determined using an isokinetic dynamometer in community-dwelling elderly women. This was a cross-sectional study. Sample selection for the study was made by convenience, and 221 (71.07 ± 4.93 years) community-dwelling elderly women were included. Knee flexor and extensor muscle performance was measured using an isokinetic dynamometer Biodex System 3 Pro. The isokinetic variables chosen for analysis were peak torque, peak torque/bodyweight, total work/bodyweight, total work, average power, and agonist/antagonist ratio at the angular velocities of 60°/s and 180°/s. Assessment of handgrip strength was carried out using the Jamar dynamometer. Spearman's correlation coefficient was calculated to identify intervariable correlations. Only knee flexor peak torque (60°/s) and average power (60°/s), and knee extensor peak torque (180°/s) and total work (180°/s) were significantly (P < 0.05), yet poorly, correlated with handgrip strength (r < 0.30). The majority of analyses did not show any correlation between variables assessed by isokinetic dynamometer and handgrip dynamometer. Caution is required when generalizing handgrip strength as a predictor of global muscle strength in community-dwelling elderly women. © 2013 Japan Geriatrics Society.

The effect of epoch length on time and frequency domain parameters of electromyographic and mechanomyographic signals.

PubMed

Keller, Joshua L; Housh, Terry J; Camic, Clayton L; Bergstrom, Haley C; Smith, Doug B; Smith, Cory M; Hill, Ethan C; Schmidt, Richard J; Johnson, Glen O; Zuniga, Jorge M

2018-06-01

The selection of epoch lengths affects the time and frequency resolution of electromyographic (EMG) and mechanomyographic (MMG) signals, as well as decisions regarding the signal processing techniques to use for determining the power density spectrum. No previous studies, however, have examined the effects of epoch length on parameters of the MMG signal. The purpose of this study was to examine the differences between epoch lengths for EMG amplitude, EMG mean power frequency (MPF), MMG amplitude, and MMG MPF from the VL and VM muscles during MVIC muscle actions as well as at each 10% of the time to exhaustion (TTE) during a continuous isometric muscle action of the leg extensors at 50% of MVIC. During the MVIC trial, there were no significant (p > 0.05) differences between epoch lengths (0.25, 0.50, 1.00, and 2.00-s) for mean absolute values for any of the EMG or MMG parameters. During the submaximal, sustained muscle action, however, absolute MMG amplitude and MMG MPF were affected by the length of epoch. All epoch related differences were eliminated by normalizing the absolute values to MVIC. These findings supported normalizing EMG and MMG parameter values to MVIC and utilizing epoch lengths that ranged from 0.25 to 2.00-s. Copyright © 2018 Elsevier Ltd. All rights reserved.

Relationship between isometric shoulder strength and arms-only swimming power among male collegiate swimmers: study of valid clinical assessment methods.

PubMed

Awatani, Takenori; Morikita, Ikuhiro; Mori, Seigo; Shinohara, Junji; Tatsumi, Yasutaka

2018-04-01

[Purpose] The purpose of the present study was to confirm the relationships between shoulder strength (extensor strength and internal rotator strength) of the abducted position and swimming power during arm-only swimming. [Subjects and Methods] Fourteen healthy male collegiate swimmers participated in the study. Main measures were shoulder strength (strength using torque that was calculated from the upper extremity length and the isometric force of the abducted position) and swimming power. [Results] Internal rotation torque of the dominant side in the abducted external rotated position (r=0.85) was significantly correlated with maximum swimming power. The rate of bilateral difference in extension torque in the maximum abducted position (r=-0.728) was significantly correlated with the swimming velocity-to-swimming power ratio. [Conclusion] The results of this study suggest that internal rotator strength measurement in the abducted external rotated position and extensor strength measurement in the maximum abducted position are valid assessment methods for swimmers.

Pelvic movement strategies and leg extension power in patients with end-stage medial compartment knee osteoarthritis: a cross-sectional study.

PubMed

Kierkegaard, Signe; Jørgensen, Peter Bo; Dalgas, Ulrik; Søballe, Kjeld; Mechlenburg, Inger

2015-09-01

During movement tasks, patients with medial compartment knee osteoarthritis use compensatory strategies to minimise the joint load of the affected leg. Movement strategies of the knees and trunk have been investigated, but less is known about movement strategies of the pelvis during advancing functional tasks, and how these strategies are associated with leg extension power. The aim of the study was to investigate pelvic movement strategies and leg extension power in patients with end-stage medial compartment knee osteoarthritis compared with controls. 57 patients (mean age 65.6 years) scheduled for medial uni-compartmental knee arthroplasty, and 29 age and gender matched controls were included in this cross-sectional study. Leg extension power was tested with the Nottingham Leg Extension Power-Rig. Pelvic range of motion was derived from an inertia-based measurement unit placed over the sacrum bone during walking, stair climbing and stepping. Patients had lower leg extension power than controls (20-39 %, P < 0.01) and used greater pelvic range of motion during stair and step ascending and descending (P ≤ 0.03, except for pelvic range of motion in the frontal plane during ascending, P > 0.06). Furthermore, an inverse association (coefficient: -0.03 to -0.04; R (2) = 13-22 %) between leg extension power and pelvic range of motion during stair and step descending was found in the patients. Compared to controls, patients with medial compartment knee osteoarthritis use greater pelvic movements during advanced functional performance tests, particularly when these involve descending tasks. Further studies should investigate if it is possible to alter these movement strategies by an intervention aimed at increasing strength and power for the patients.

An approach to counteracting long-term microgravity-induced muscle atrophy

NASA Technical Reports Server (NTRS)

Tesch, P. A.; Buchanan, P.; Dudley, G. A.

1990-01-01

To find means of alleviating muscle atrophy induced by long-term microgravity, the effects of a 19-week-long heavy-resistance training regime (using either concentric muscle actions only or concentric and eccentric muscle actions) on the strengths of the exercised knee extensor muscle group were investigated in two groups of male human subjects performing two types of training exercises: supine leg press or/and seated knee extension. Results show that a training program in which both the concentric and the eccentric muscle action was performed led to substantially greater increases in maximal muscle strength than when only concentric exercises were performed.

Effects of stretching and disuse on amino acids in muscles of rat hind limbs

NASA Technical Reports Server (NTRS)

Jaspers, Stephen R.; Henriksen, Erik J.; Satarug, Soisungwan; Tischler, Marc E.

1989-01-01

The effects of disuse and passive stretch on the concentrations of amino acids and ammonia in the unloaded soleus muscle was investigated in hindquarter-suspended (for six days by casting one foot in dorsiflexion) tail-casted rats. For a comparison with the condition of unloading, amino acids and ammonia were also measured in shortened extensor digitorum longus in the same casted limb and in denervated leg muscles. The results obtained suggest that passive stretch diminishes some of the characteristic alterations of amino acid concentrations due to unloading. This effect of stretch is considered to be due to the maintenance of muscle tension.

Flexibility training in preadolescent female athletes: Acute and long-term effects of intermittent and continuous static stretching.

PubMed

Donti, Οlyvia; Papia, Konstantina; Toubekis, Argyris; Donti, Anastasia; Sands, William A; Bogdanis, Gregory C

2018-07-01

This study compared the acute and long-term effects of intermittent and continuous static stretching training on straight leg raise range of motion (ROM). Seventy-seven preadolescent female gymnasts were divided into a stretching (n = 57), and a control group (n = 20). The stretching group performed static stretching of the hip extensors of both legs, three times per week for 15 weeks. One leg performed intermittent (3 × 30 s with 30 s rest) while the other leg performed continuous stretching (90 s). ROM pre- and post-stretching was measured at baseline, on weeks 3, 6, 9, 12, 15 and after 2 weeks of detraining. ROM was increased during both intermittent and continuous stretching training, but remained unchanged in the control group. Intermittent stretching conferred a larger improvement in ROM compared to both continuous stretching and control from week 3, until the end of training, and following detraining (p = 0.045 to 0.001 and d = 0.80 to 1.41). During detraining, ROM after the intermittent protocol decreased (p = 0.001), while it was maintained after the continuous protocol (p = 0.36). Acute increases in ROM following the intermittent stretching were also larger than in the continuous (p = 0.038). Intermittent stretching was more effective than continuous, for both long-term and acute ROM enhancement in preadolescent female athletes.

Sex differences in neuromuscular function after repeated eccentric contractions of the knee extensor muscles.

PubMed

Lee, Andrea; Baxter, Jake; Eischer, Claire; Gage, Matt; Hunter, Sandra; Yoon, Tejin

2017-06-01

This study examined the mechanisms for force and power reduction during and up to 48 h after maximal eccentric contractions of the knee extensor muscles in young men and women. 13 men (22.8 ± 2.6 years) and 13 women (21.6 ± 2.2 years) performed 150 maximal effort eccentric contractions (5 sets of 30) with the knee extensor muscles at 60° s -1 . Maximal voluntary isometric contractions (MVIC) and maximal voluntary concentric contractions (MVCC) were performed before and after the 150 eccentric contractions. The MVCCs involved a set of two isokinetic contractions at 60° s -1 and sets of isotonic contractions performed at seven different resistance loads (1 N m, 10, 20, 30, 40, 50, and 60% MVIC). Electrical stimulation was used during the MVICs and at rest to determine changes in voluntary activation and contractile properties. At baseline, men were stronger than women (MVIC: 276 ± 48 vs. 133 ± 37 N m) and more powerful (MVCC: 649 ± 77 vs. 346 ± 78 W). At termination of the eccentric contractions, voluntary activation, resting twitch amplitude, and peak power during concentric contractions at the seven loads and at 60° s -1 decreased (P < 0.05) similarly in the men and women. At 48 h post-exercise, the MVIC torque, power (for loads ≥20-60% MVIC), and voluntary activation remained depressed (P < 0.05), but the resting twitch had returned to baseline (P > 0.05) with no sex differences. Central mechanisms were primarily responsible for the depressed maximal force production up to 48 h after repeated eccentric contractions of the knee extensors and these mechanisms were similar in men and women.

Exercise Training in Treatment and Rehabilitation of Hip Osteoarthritis: A 12-Week Pilot Trial

PubMed Central

Patil, Radhika; Karinkanta, Saija; Tokola, Kari; Kannus, Pekka

2017-01-01

Introduction. Osteoarthritis (OA) of the hip is one of the major causes of pain and disability in the older population. Although exercise is an effective treatment for knee OA, there is lack of evidence regarding hip OA. The aim of this trial was to test the safety and feasibility of a specifically designed exercise program in relieving hip pain and improving function in hip OA participants and to evaluate various methods to measure changes in their physical functioning. Materials and Methods. 13 women aged ≥ 65 years with hip OA were recruited in this 12-week pilot study. Results. Pain declined significantly over 30% from baseline, and joint function and health-related quality of life improved slightly. Objective assessment of physical functioning showed statistically significant improvement in the maximal isometric leg extensor strength by 20% and in the hip extension range of motion by 30%. Conclusions. The exercise program was found to be safe and feasible. The present evidence indicates that the exercise program is effective in the short term. However, adequate powered RCTs are needed to determine effects of long-term exercise therapy on pain and progression of hip OA. PMID:28116214

Effects of combined high intensity arm and leg training on performance and cardio-respiratory measures.

PubMed

Zinner, Christoph; Sperlich, Billy; Born, Dennis-Peter; Michels, Guido

2017-01-01

The purpose of this study was to investigate the effects of combined arm and leg high-intensity low-volume interval training (HIITarm+leg) on maximal oxygen uptake, myocardial measures (i.e. stroke volume, cardiac output, ejection fraction), Tissue Oxygenation Index (TOI) of the vastus lateralis and triceps brachii, as well as power output in comparison to leg HIIT (HIITleg) only. The 20 healthy, male and female volunteers completed six sessions of either HIITleg on a cycle ergometer or HIITarm+leg on an arm and leg cycle ergometer. During pre- and post-testing, the volunteers completed a submaximal and incremental test to exhaustion on a cycle ergometer. Magnitude based interference revealed likely to very likely beneficial effects for HIITarm+leg compared to HIITleg in maximal oxygen uptake, cardiac measures as well peak power output. The TOI following HIITarm+leg demonstrated likely to very likely increased oxygenation in the triceps brachii or the vastus lateralis when compared to HIITleg. The results suggest that six sessions of HIITarm+leg may likely to very likely improve maximal oxygen uptake, some inotropy-related cardiac measures with improved tissue oxygenation of the triceps brachii and vastus lateralis muscles resulting in greater leg peak power output.

Reduced oxygen cost of running is related to alignment of the resultant GRF and leg axis vector: A pilot study.

PubMed

Moore, I S; Jones, A M; Dixon, S J

2016-07-01

This pilot study investigated whether a 10-week running program (10wkRP), which reduced the oxygen cost of running, affected resultant ground reaction force (GRF), leg axis alignment, joint moment characteristics, and gear ratios. Ten novice, female runners completed a 10wkRP. Running kinematics and kinetics, in addition to oxygen consumption ( V ˙ O 2 ) during steady-state running, were recorded pre- and post-10wkRP. V ˙ O 2 decreased (8%) from pre-10wkRP to post-10wkRP. There was a better alignment of the resultant GRF and leg axis at peak propulsion post-10wkRP compared with pre-10wkRP (10.8 ± 4.9 vs 1.6 ± 1.2°), as the resultant GRF vector was applied 7 ± 0.6° (P = 0.008) more horizontally. There were shorter external ankle moment arms (24%) and smaller knee extensor moments (23%) at peak braking post-10wkRP. The change in V ˙ O 2 was associated with the change in alignment of the resultant GRF and leg axis (rs  = 0.88, P = 0.003). As runners became more economical, they exhibited a more aligned resultant GRF vector and leg axis at peak propulsion. This appears to be a self-optimization strategy that may improve performance. Additionally, changes to external ankle moment arms indicated beneficial low gear ratios were achieved at the time of peak braking force. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Interdependence of torque, joint angle, angular velocity and muscle action during human multi-joint leg extension.

PubMed

Hahn, Daniel; Herzog, Walter; Schwirtz, Ansgar

2014-08-01

Force and torque production of human muscles depends upon their lengths and contraction velocity. However, these factors are widely assumed to be independent of each other and the few studies that dealt with interactions of torque, angle and angular velocity are based on isolated single-joint movements. Thus, the purpose of this study was to determine force/torque-angle and force/torque-angular velocity properties for multi-joint leg extensions. Human leg extension was investigated (n = 18) on a motor-driven leg press dynamometer while measuring external reaction forces at the feet. Extensor torque in the knee joint was calculated using inverse dynamics. Isometric contractions were performed at eight joint angle configurations of the lower limb corresponding to increments of 10° at the knee from 30 to 100° of knee flexion. Concentric and eccentric contractions were performed over the same range of motion at mean angular velocities of the knee from 30 to 240° s(-1). For contractions of increasing velocity, optimum knee angle shifted from 52 ± 7 to 64 ± 4° knee flexion. Furthermore, the curvature of the concentric force/torque-angular velocity relations varied with joint angles and maximum angular velocities increased from 866 ± 79 to 1,238 ± 132° s(-1) for 90-50° knee flexion. Normalised eccentric forces/torques ranged from 0.85 ± 0.12 to 1.32 ± 0.16 of their isometric reference, only showing significant increases above isometric and an effect of angular velocity for joint angles greater than optimum knee angle. The findings reveal that force/torque production during multi-joint leg extension depends on the combined effects of angle and angular velocity. This finding should be accounted for in modelling and optimisation of human movement.

Muscle strength and soft tissue composition as measured by dual energy x-ray absorptiometry in women aged 18-87 years.

PubMed

Madsen, O R; Lauridsen, U B; Hartkopp, A; Sørensen, O H

1997-01-01

Dual energy x-ray absorptiometry (DEXA) offers the possibility of assessing regional soft tissue composition, i.e. lean mass (LM) and fat mass: LM may be considered a measure of muscle mass. We examined age-related differences in LM, percentage fat (%fat) and muscle strength in 100 healthy non-athletic women aged 18-87 years. Relationships between muscle strength and leg LM in 20 elite female weight lifters and in 18 inactive women with previous hip fractures were also studied. The LM and %fat of the whole body, trunk, arms and legs were derived from a whole body DEXA scan. Isokinetic knee extensor strength (KES) and flexor strength (KFS) at 30 degrees.s-1 were assessed using an isokinetic dynamometer. The women aged 71-87 years had 35% lower KES and KFS than the women aged 18-40 years (P < 0.0001). Differences in LM were less pronounced. The LM of the legs, for instance, was 15% lower in the old than in the young women (P < 0.0001). In a multiple regression analysis with age, body mass, height and leg LM or KES as independent variables and KES or leg LM as the dependent variable, age was the most important predictor of KES (r(partial) = -0.74, P < 0.0001). The same applied to KFS. Body mass, not age, was the most important predictor of leg LM (r(partial) = 0.65, P < 0.0001) and of LM at all other measurement sites. The LM measured at different regions decreased equally with increasing age. The KES:leg LM ratio was negatively correlated with age (r = -0.70, P < 0.0001). The weight lifters had significantly higher KES:leg LM ratios than age-matched controls (+ 12%, P < 0.0001) and vice versa for the women with previous hip fractures (-36%, P < 0.0001). In conclusion, from our study it would seem that in healthy nonathletic women, age is a more important determinant of muscle strength than is LM as measured by DEXA. Muscle strengthening exercises and inactivity seem to have a considerably stronger influence on muscle strength than on LM.

Reliability and Validity of a New Method for Isometric Back Extensor Strength Evaluation Using A Hand-Held Dynamometer.

PubMed

Park, Hee-Won; Baek, Sora; Kim, Hong Young; Park, Jung-Gyoo; Kang, Eun Kyoung

2017-10-01

To investigate the reliability and validity of a new method for isometric back extensor strength measurement using a portable dynamometer. A chair equipped with a small portable dynamometer was designed (Power Track II Commander Muscle Tester). A total of 15 men (mean age, 34.8±7.5 years) and 15 women (mean age, 33.1±5.5 years) with no current back problems or previous history of back surgery were recruited. Subjects were asked to push the back of the chair while seated, and their isometric back extensor strength was measured by the portable dynamometer. Test-retest reliability was assessed with intraclass correlation coefficient (ICC). For the validity assessment, isometric back extensor strength of all subjects was measured by a widely used physical performance evaluation instrument, BTE PrimusRS system. The limit of agreement (LoA) from the Bland-Altman plot was evaluated between two methods. The test-retest reliability was excellent (ICC=0.82; 95% confidence interval, 0.65-0.91). The Bland-Altman plots demonstrated acceptable agreement between the two methods: the lower 95% LoA was -63.1 N and the upper 95% LoA was 61.1 N. This study shows that isometric back extensor strength measurement using a portable dynamometer has good reliability and validity.

Gait biomechanics of skipping are substantially different than those of running.

PubMed

McDonnell, Jessica; Willson, John D; Zwetsloot, Kevin A; Houmard, Joseph; DeVita, Paul

2017-11-07

The inherit injury risk associated with high-impact exercises calls for alternative ways to achieve the benefits of aerobic exercise while minimizing excessive stresses to body tissues. Skipping presents such an alternative, incorporating double support, flight, and single support phases. We used ground reaction forces (GRFs), lower extremity joint torques and powers to compare skipping and running in 20 healthy adults. The two consecutive skipping steps on each limb differed significantly from each other, and from running. Running had the longest step length, the highest peak vertical GRF, peak knee extensor torque, and peak knee negative and positive power and negative and positive work. Skipping had the greater cadence, peak horizontal GRF, peak hip and ankle extensor torques, peak ankle negative power and work, and peak ankle positive power. The second vs first skipping step had the shorter step length, higher cadence, peak horizontal GRF, peak ankle extensor torque, and peak ankle negative power, negative work, and positive power and positive work. The first skipping step utilized predominately net negative joint work (eccentric muscle action) while the second utilized predominately net positive joint work (concentric muscle action). The skipping data further highlight the persistence of net negative work performed at the knee and net positive work performed at the ankle across locomotion gaits. Evidence of step segregation was seen in distribution of the braking and propelling impulses and net work produced across the hip, knee, and ankle joints. Skipping was substantially different than running and was temporally and spatially asymmetrical with successive foot falls partitioned into a dominant function, either braking or propelling whereas running had a single, repeated step in which both braking and propelling actions were performed equally. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of Pilates on muscle strength, postural balance and quality of life of older adults: a randomized, controlled, clinical trial

PubMed Central

Campos de Oliveira, Laís; Gonçalves de Oliveira, Raphael; Pires-Oliveira, Deise Aparecida de Almeida

2015-01-01

[Purpose] The aim of the present study was to determine the effects of Pilates on lower leg strength, postural balance and the health-related quality of life (HRQoL) of older adults. [Subjects and Methods] Thirty-two older adults were randomly allocated either to the experimental group (EG, n = 16; mean age, 63.62 ± 1.02 years), which performed two sessions of Pilates per week for 12 weeks, or to the control group (CG, n = 16; mean age, 64.21 ± 0.80), which performed two sessions of static stretching per week for 12 weeks. The following evaluations were performed before and after the interventions: isokinetic torque of knee extensors and flexors at 300°/s, the Timed Up and Go (TUG) test, the Berg Balance Scale, and the Health Survey assessment (SF-36). [Results] In the intra-group analysis, the EG demonstrated significant improvement in all variables. In the inter-group analysis, the EG demonstrated significant improvement in most variables. [Conclusion] Pilates exercises led to significant improvement in isokinetic torque of the knee extensors and flexors, postural balance and aspects of the health-related quality of life of older adults. PMID:25931749

Relation between isokinetic muscle strength and functional capacity in recreational athletes with chondromalacia patellae.

PubMed

Yildiz, Y; Aydin, T; Sekir, U; Cetin, C; Ors, F; Alp Kalyon, T

2003-12-01

To investigate the effects of isokinetic exercise on pain and functional test scores of recreational athletes with chondromalacia patellae (CMP) and to examine the correlation between isokinetic parameters and functional tests or pain score. The functional ability of 30 recreational athletes with unilateral CMP was evaluated using six different tests. Pain scores were assessed during daily activities before and after the treatment protocol. Isokinetic exercise sessions were carried out at angular velocities of 60 degrees /s (25-90 degrees range of flexion) and 180 degrees /s (full range). These sessions were repeated three times a week for six weeks. Quadriceps and hamstring peak torque, total work, and endurance ratios had improved significantly after the treatment, as did the functional parameters and pain scores. There was a poor correlation between the extensor endurance ratio and one leg standing test. A moderate correlation between the visual analogue scale and the extensor endurance ratio or flexion endurance ratio was also found. The isokinetic exercise programme used in this study had a positive effect on muscle strength, pain score, and functional ability of knees with CMP. The improvement in the functional capacity did not correlate with the isokinetic parameters.

Effects of Swiss-ball core strength training on strength, endurance, flexibility, and balance in sedentary women.

PubMed

Sekendiz, Betül; Cuğ, Mutlu; Korkusuz, Feza

2010-11-01

The purpose of this study was to investigate the effects of Swiss-ball core strength training on trunk extensor (abdominal)/flexor (lower back) and lower limb extensor (quadriceps)/flexor (hamstring) muscular strength, abdominal, lower back and leg endurance, flexibility and dynamic balance in sedentary women (n = 21; age = 34 ± 8.09; height = 1.63 ± 6.91 cm; weight = 64 ± 8.69 kg) trained for 45 minutes, 3 d·wk-1 for 12 weeks. Results of multivariate analysis revealed significant difference (p ≤ 0.05) between pre and postmeasures of 60 and 90° s trunk flexion/extension, 60 and 240° s-1 lower limb flexion/extension (Biodex Isokinetic Dynamometer), abdominal endurance (curl-up test), lower back muscular endurance (modified Sorensen test), lower limb endurance (repetitive squat test), lower back flexibility (sit and reach test), and dynamic balance (functional reach test). The results support the fact that Swiss-ball core strength training exercises can be used to provide improvement in the aforementioned measures in sedentary women. In conclusion, this study provides practical implications for sedentary individuals, physiotherapists, strength and conditioning specialists who can benefit from core strength training with Swiss balls.

Musculoskeletal injuries in the ultramarathon: the 1990 Westfield Sydney to Melbourne run.

PubMed Central

Fallon, K E

1996-01-01

OBJECTIVE: To document the injuries sustained by participants in a 1005 km ultramarathon. METHODS: Clinical notes were reviewed on entrants in the 1005 km Sydney to Melbourne ultramarathon. An injury was recorded following self referral by a participant or if the history obtained from the runner or his support crew indicated the likelihood of a significant injury which could have an impact upon performance. RESULTS: 64 injuries were found in 32 runners. The knee (31.3%) and ankle (28.1%) regions were most commonly injured. The most common single diagnosis was retropatellar pain syndrome, and Achilles tendinitis and medial tibial stress syndrome were the next most common injuries. Peritendinitis/tendinitis of the tendons passing under the extensor retinaculum at the ankle, an injury infrequently reported in other sports, was common (19% of all injuries). CONCLUSIONS: The injuries were typically associated with running but 12 (19% of the total) involved the tendons of the muscles of the anterior compartment of the lower leg, and in almost every case the major site of inflammation was at the extensor retinaculum at the anterior aspect of the ankle. This injury appears to be relatively specific to the ultramarathon-"ultramarathoner's ankle". Images p321-a PMID:9015594

Investigating the Effects of Typical Rowing Strength Training Practices on Strength and Power Development and 2,000 m Rowing Performance

PubMed Central

Caplan, Nicholas; Christian Gibbon, Karl; Howatson, Glyn; Grant Thompson, Kevin

2016-01-01

Abstract This study aimed to determine the effects of a short-term, strength training intervention, typically undertaken by club-standard rowers, on 2,000 m rowing performance and strength and power development. Twenty-eight male rowers were randomly assigned to intervention or control groups. All participants performed baseline testing involving assessments of muscle soreness, creatine kinase activity (CK), maximal voluntary contraction (leg-extensors) (MVC), static-squat jumps (SSJ), counter-movement jumps (CMJ), maximal rowing power strokes (PS) and a 2,000 m rowing ergometer time-trial (2,000 m) with accompanying respiratory-exchange and electromyography (EMG) analysis. Intervention group participants subsequently performed three identical strength training (ST) sessions, in the space of five days, repeating all assessments 24 h following the final ST. The control group completed the same testing procedure but with no ST. Following ST, the intervention group experienced significant elevations in soreness and CK activity, and decrements in MVC, SSJ, CMJ and PS (p < 0.01). However, 2,000 m rowing performance, pacing strategy and gas exchange were unchanged across trials in either condition. Following ST, significant increases occurred for EMG (p < 0.05), and there were non-significant trends for decreased blood lactate and anaerobic energy liberation (p = 0.063 – 0.086). In summary, club-standard rowers, following an intensive period of strength training, maintained their 2,000 m rowing performance despite suffering symptoms of muscle damage and disruption to muscle function. This disruption likely reflected the presence of acute residual fatigue, potentially in type II muscle fibres as strength and power development were affected. PMID:28149354

Maximum step length: relationships to age and knee and hip extensor capacities.

PubMed

Schulz, Brian W; Ashton-Miller, James A; Alexander, Neil B

2007-07-01

Maximum Step Length may be used to identify older adults at increased risk for falls. Since leg muscle weakness is a risk factor for falls, we tested the hypotheses that maximum knee and hip extension speed, strength, and power capacities would significantly correlate with Maximum Step Length and also that the "step out and back" Maximum Step Length [Medell, J.L., Alexander, N.B., 2000. A clinical measure of maximal and rapid stepping in older women. J. Gerontol. A Biol. Sci. Med. Sci. 55, M429-M433.] would also correlate with the Maximum Step Length of its two sub-tasks: stepping "out only" and stepping "back only". These sub-tasks will be referred to as versions of Maximum Step Length. Unimpaired younger (N=11, age=24[3]years) and older (N=10, age=73[5]years) women performed the above three versions of Maximum Step Length. Knee and hip extension speed, strength, and power capacities were determined on a separate day and regressed on Maximum Step Length and age group. Version and practice effects were quantified and subjective impressions of test difficulty recorded. Hypotheses were tested using linear regressions, analysis of variance, and Fisher's exact test. Maximum Step Length explained 6-22% additional variance in knee and hip extension speed, strength, and power capacities after controlling for age group. Within- and between-block and test-retest correlation values were high (>0.9) for all test versions. Shorter Maximum Step Lengths are associated with reduced knee and hip extension speed, strength, and power capacities after controlling for age. A single out-and-back step of maximal length is a feasible, rapid screening measure that may provide insight into underlying functional impairment, regardless of age.

On the Biomimetic Design of Agile-Robot Legs

PubMed Central

Garcia, Elena; Arevalo, Juan Carlos; Muñoz, Gustavo; Gonzalez-de-Santos, Pablo

2011-01-01

The development of functional legged robots has encountered its limits in human-made actuation technology. This paper describes research on the biomimetic design of legs for agile quadrupeds. A biomimetic leg concept that extracts key principles from horse legs which are responsible for the agile and powerful locomotion of these animals is presented. The proposed biomimetic leg model defines the effective leg length, leg kinematics, limb mass distribution, actuator power, and elastic energy recovery as determinants of agile locomotion, and values for these five key elements are given. The transfer of the extracted principles to technological instantiations is analyzed in detail, considering the availability of current materials, structures and actuators. A real leg prototype has been developed following the biomimetic leg concept proposed. The actuation system is based on the hybrid use of series elasticity and magneto-rheological dampers which provides variable compliance for natural motion. From the experimental evaluation of this prototype, conclusions on the current technological barriers to achieve real functional legged robots to walk dynamically in agile locomotion are presented. PMID:22247667

On the biomimetic design of agile-robot legs.

PubMed

Garcia, Elena; Arevalo, Juan Carlos; Muñoz, Gustavo; Gonzalez-de-Santos, Pablo

2011-01-01

The development of functional legged robots has encountered its limits in human-made actuation technology. This paper describes research on the biomimetic design of legs for agile quadrupeds. A biomimetic leg concept that extracts key principles from horse legs which are responsible for the agile and powerful locomotion of these animals is presented. The proposed biomimetic leg model defines the effective leg length, leg kinematics, limb mass distribution, actuator power, and elastic energy recovery as determinants of agile locomotion, and values for these five key elements are given. The transfer of the extracted principles to technological instantiations is analyzed in detail, considering the availability of current materials, structures and actuators. A real leg prototype has been developed following the biomimetic leg concept proposed. The actuation system is based on the hybrid use of series elasticity and magneto-rheological dampers which provides variable compliance for natural motion. From the experimental evaluation of this prototype, conclusions on the current technological barriers to achieve real functional legged robots to walk dynamically in agile locomotion are presented.

Relationships Between Lower-Body Muscle Structure and, Lower-Body Strength, Explosiveness and Eccentric Leg Stiffness in Adolescent Athletes

PubMed Central

Secomb, Josh L.; Nimphius, Sophia; Farley, Oliver R.L.; Lundgren, Lina E.; Tran, Tai T.; Sheppard, Jeremy M.

2015-01-01

The purpose of the present study was to determine whether any relationships were present between lower-body muscle structure and, lower-body strength, variables measured during a countermovement jump (CMJ) and squat jump (SJ), and eccentric leg stiffness, in adolescent athletes. Thirty junior male (n = 23) and female (n = 7) surfing athletes (14.8 ± 1.7 y; 1.63 ± 0.09 m; 54.8 ± 12.1 kg) undertook lower-body muscle structure assessment with ultrasonography and performed a; CMJ, SJ and an isometric mid-thigh pull (IMTP). In addition, eccentric leg stiffness was calculated from variables of the CMJ and IMTP. Moderate to very large relationships (r = 0.46-0.73) were identified between the thickness of the vastus lateralis (VL) and lateral gastrocnemius (LG) muscles, and VL pennation angle and; peak force (PF) in the CMJ, SJ and IMTP. Additionally, moderate to large relationships (r = 0.37-0.59) were found between eccentric leg stiffness and; VL and LG thickness, VL pennation angle, and LG fascicle length, with a large relationship (r = 0.59) also present with IMTP PF. These results suggest that greater thickness of the VL and LG were related to improved maximal dynamic and isometric strength, likely due to increased hypertrophy of the extensor muscles. Furthermore, this increased thickness was related to greater eccentric leg stiffness, as the associated enhanced lower-body strength likely allowed for greater neuromuscular activation, and hence less compliance, during a stretch-shortening cycle. Key points Greater thickness of the VL and LG muscles were significantly related to an enhanced ability to express higher levels of isometric and dynamic strength, and explosiveness in adolescent athletes. Isometric strength underpinned performance in the CMJ and SJ in these athletes. Greater lower-body isometric strength was significantly related to eccentric leg stiffness, which is potentially the result of greater neuromuscular activation in the muscle-tendon unit. PMID:26664263

A Biomechanical Comparison of Single-Leg Landing and Unplanned Sidestepping.

PubMed

Chinnasee, Chamnan; Weir, Gillian; Sasimontonkul, Siriporn; Alderson, Jacqueline; Donnelly, Cyril

2018-06-14

Unplanned sidestepping and single-leg landing have both been used to screen athletes for injury risk in sport. The aim of this study was to directly compare the lower limb mechanics of three single-leg landing tasks and an unplanned sidestepping task. Thirteen elite female team sport athletes completed a series of non-contact single-leg drop landings, single-leg countermovement jumps, single-leg jump landings and unplanned sidestepping in a randomized counterbalanced design. Three dimensional kinematics (250 Hz) and ground reaction force (2,000 Hz) data with a participant specific lower limb skeletal model were used to calculate and compare hip, knee and ankle joint kinematics, peak joint moments, instantaneous joint power and joint work during the weight acceptance phase of each sporting task (α=0.05). Peak knee joint moments and relevant injury risk thresholds were used to classify each athlete's anterior cruciate ligament injury risk during unplanned sidestepping and single-leg jump landing. Results showed that peak joint moments, power and work were greater during the single-leg jump landing task when compared to the single-leg drop landings and single-leg countermovement jumps tasks. Peak frontal and sagittal plane knee joint moments, knee joint power, as well as hip and knee joint work were greater during unplanned sidestepping when compared to the landing tasks. Peak ankle joint moments, power and work were greater during the landing tasks when compared to unplanned sidestepping. For 4 of the 13 athletes tested, their anterior cruciate ligament injury risk classification changed depending on whether they performed an unplanned sidestepping or single-leg jump landing testing procedure. To summarize, a single-leg jump landing testing procedure places a larger mechanical on the ankle joint when compared to single-leg drop landings, single-leg countermovement jumps and unplanned sidestepping. An unplanned sidestepping testing procedure places a larger mechanical demand on the knee joint when compared to single-leg landing tasks. Both unplanned sidestepping and single-leg jump landing testing procedures are recommended for classifying an athlete's anterior cruciate ligament injury risk in sport. © Georg Thieme Verlag KG Stuttgart · New York.

Short-Term High Intensity Plyometric Training Program Improves Strength, Power and Agility in Male Soccer Players

PubMed Central

Váczi, Márk; Tollár, József; Meszler, Balázs; Juhász, Ivett; Karsai, István

2013-01-01

The aim of the present study was to investigate the effects of a short-term in-season plyometric training program on power, agility and knee extensor strength. Male soccer players from a third league team were assigned into an experimental and a control group. The experimental group, beside its regular soccer training sessions, performed a periodized plyometric training program for six weeks. The program included two training sessions per week, and maximal intensity unilateral and bilateral plyometric exercises (total of 40 – 100 foot contacts/session) were executed. Controls participated only in the same soccer training routine, and did not perform plyometrics. Depth vertical jump height, agility (Illinois Agility Test, T Agility Test) and maximal voluntary isometric torque in knee extensors using Multicont II dynamometer were evaluated before and after the experiment. In the experimental group small but significant improvements were found in both agility tests, while depth jump height and isometric torque increments were greater. The control group did not improve in any of the measures. Results of the study indicate that plyometric training consisting of high impact unilateral and bilateral exercises induced remarkable improvements in lower extremity power and maximal knee extensor strength, and smaller improvements in soccer-specific agility. Therefore, it is concluded that short-term plyometric training should be incorporated in the in-season preparation of lower level players to improve specific performance in soccer. PMID:23717351

Short-term high intensity plyometric training program improves strength, power and agility in male soccer players.

PubMed

Váczi, Márk; Tollár, József; Meszler, Balázs; Juhász, Ivett; Karsai, István

2013-03-01

The aim of the present study was to investigate the effects of a short-term in-season plyometric training program on power, agility and knee extensor strength. Male soccer players from a third league team were assigned into an experimental and a control group. The experimental group, beside its regular soccer training sessions, performed a periodized plyometric training program for six weeks. The program included two training sessions per week, and maximal intensity unilateral and bilateral plyometric exercises (total of 40 - 100 foot contacts/session) were executed. Controls participated only in the same soccer training routine, and did not perform plyometrics. Depth vertical jump height, agility (Illinois Agility Test, T Agility Test) and maximal voluntary isometric torque in knee extensors using Multicont II dynamometer were evaluated before and after the experiment. In the experimental group small but significant improvements were found in both agility tests, while depth jump height and isometric torque increments were greater. The control group did not improve in any of the measures. Results of the study indicate that plyometric training consisting of high impact unilateral and bilateral exercises induced remarkable improvements in lower extremity power and maximal knee extensor strength, and smaller improvements in soccer-specific agility. Therefore, it is concluded that short-term plyometric training should be incorporated in the in-season preparation of lower level players to improve specific performance in soccer.

Towards a Comparative Measure of Legged Agility

DTIC Science & Technology

2014-06-01

body movement with change of velocity or direction in response to a stimulus” [18]. Notwithstanding the many informative and inspiring studies of legged...specific power (watts per kilogram taken over a gait cycle of leg power output relative to leg muscle mass or body mass) [22, 26–28] but it is not scale...closest to the body mass normalized mea- sure we will introduce below. In contrast, characterizing directional aspects of agility performance seems

Metabolism of branched-chain amino acids in leg muscles from tail-cast suspended intact and adrenalectomized rats

NASA Technical Reports Server (NTRS)

Jaspers, Stephen R.; Henriksen, Erik; Jacob, Stephan; Tischler, Marc E.

1989-01-01

The effects of muscle unloading, adrenalectomy, and cortisol treatment on the metabolism of branched-chain amino acids in the soleus and extensor digitorum longus of tail-cast suspended rats were investigated using C-14-labeled lucine, isoleucine, and valine in incubation studies. It was found that, compared to not suspended controls, the degradation of branched-chain amino acids in hind limb muscles was accelerated in tail-cast suspended rats. Adrenalectomy was found to abolish the aminotransferase flux and to diminish the dehydrogenase flux in the soleus. The data also suggest that cortisol treatment increases the rate of metabolism of branched-chain amino acids at the dehydrogenase step.

Motor unit number estimates correlate with strength in polio survivors.

PubMed

Sorenson, Eric J; Daube, Jasper R; Windebank, Anthony J

2006-11-01

Motor unit number estimation (MUNE) has been proposed as an outcome measure in clinical trials for the motor neuron diseases. One major criticism of MUNE is that it may not represent a clinically meaningful endpoint. We prospectively studied a cohort of polio survivors over a period of 15 years with respect to MUNE and strength. We identified a significant association between thenar MUNE and arm strength, extensor digitorum brevis MUNE and leg strength, and the summated MUNE and global strength of the polio survivors. These findings confirm the clinical relevance of MUNE as an outcome measure in the motor neuron diseases and provide further validation for its use in clinical trial research.

Extended healing validation of an artificial tendon to connect the quadriceps muscle to the Tibia: 180-day study.

PubMed

Melvin, Alan J; Litsky, Alan S; Mayerson, Joel L; Stringer, Keith; Juncosa-Melvin, Natalia

2012-07-01

Whenever a tendon or its bone insertion is disrupted or removed, existing surgical techniques provide a temporary connection or scaffolding to promote healing, but the interface of living to non-living materials soon breaks down under the stress of these applications, if it must bear the load more than acutely. Patients are thus disabled whose prostheses, defect size, or mere anatomy limit the availability or outcomes of such treatments. Our group developed the OrthoCoupler™ device to join skeletal muscle to prosthetic or natural structures without this interface breakdown. In this study, the goat knee extensor mechanism (quadriceps tendon, patella, and patellar tendon) was removed from the right hind limb in 16 goats. The device connected the quadriceps muscle to a stainless steel bone plate on the tibia. Mechanical testing and histology specimens were collected from each operated leg and contralateral unoperated control legs at 180 days. Maximum forces in the operated leg (vs. unoperated) were 1,400 ± 93 N (vs. 1,179 ± 61 N), linear stiffnesses were 33 ± 3 N/mm (vs. 37 ± 4 N/mm), and elongations at failure were 92.1 ± 5.3 mm (vs. 68.4 ± 3.8 mm; mean ± SEM). Higher maximum forces (p = 0.02) and elongations at failure (p=0.008) of legs with the device versus unoperated controls were significant; linear stiffnesses were not (p=0.3). We believe this technology will yield improved procedures for clinical challenges in orthopedic oncology, revision arthroplasty, tendon transfer, and tendon injury reconstruction. Copyright © 2011 Orthopaedic Research Society.

Ground reaction force and 3D biomechanical characteristics of walking in short-leg walkers.

PubMed

Zhang, Songning; Clowers, Kurt G; Powell, Douglas

2006-12-01

Short-leg walking boots offer several advantages over traditional casts. However, their effects on ground reaction forces (GRF) and three-dimensional (3D) biomechanics are not fully understood. The purpose of the study was to examine 3D lower extremity kinematics and joint dynamics during walking in two different short-leg walking boots. Eleven (five females and six males) healthy subjects performed five level walking trials in each of three conditions: two testing boot conditions, Gait Walker (DeRoyal Industries, Inc.) and Equalizer (Royce Medical Co.), and one pair of laboratory shoes (Noveto, Adidas). A force platform and a 6-camera Vicon motion analysis system were used to collect GRFs and 3D kinematic data during the testing session. A one-way repeated measures analysis of variance (ANOVA) was used to evaluate selected kinematic, GRF, and joint kinetic variables (p<0.05). The results revealed that both short-leg walking boots were effective in minimizing ankle eversion and hip adduction. Neither walker increased the bimodal vertical GRF peaks typically observed in normal walking. However, they did impose a small initial peak (<1BW) earlier in the stance phase. The Gait Walker also exhibited a slightly increased vertical GRF during midstance. These characteristics may be related to the sole materials/design, the restriction of ankle movements, and/or the elevated heel heights of the tested walkers. Both walkers appeared to increase the demand on the knee extensors while they decreased the demand of the knee and hip abductors based on the joint kinetic results.

Experimental muscle pain challenges the postural stability during quiet stance and unexpected posture perturbation.

PubMed

Hirata, Rogério Pessoto; Ervilha, Ulysses Fernandes; Arendt-Nielsen, Lars; Graven-Nielsen, Thomas

2011-08-01

Musculoskeletal pain impairs postural control and stability. Nine subjects stood as quietly as possible on a moveable force platform before, during, and after experimental pain in the right leg muscles. A moveable force platform was used to measure the center of pressure and provided unexpected perturbations. Lower limb muscle activity, joint angles, and foot pressure distributions were measured. Hypertonic saline was used to induce pain in the vastus lateralis, vastus medialis, or biceps femoris muscle of the right leg. Compared to baseline and control sessions, pain in the knee extensor muscles during quiet standing evoked: 1) larger sway area, greater medial-lateral center of pressure displacement and higher speed (P < .05); 2) increased sway displacement in the anterior-posterior direction (P < .05); and 3) increased electromyography (EMG) activity for left tibialis anterior and left erector spinae muscles (P < .05). Pain provoked longer time to return to an equilibrium posture after forward EMG activity for, and pain in vastus medialis muscle decreased the time for the maximum hip flexion during this perturbation (P < .05). These results show that muscle pain impairs postural stability during quiet standing and after unexpected perturbation, which suggest that people suffering from leg muscle pain are more vulnerable to falls. This article presents the acute responses to leg muscle pain on the postural control. This measure could potentially help clinicians who seek to assess how pain responses may contribute to patient's postural control and stability during quiet standing and after recovering from unexpected perturbations. Copyright © 2011 American Pain Society. Published by Elsevier Inc. All rights reserved.

Ischemic contracture of the foot and ankle: principles of management and prevention.

PubMed

Botte, M J; Santi, M D; Prestianni, C A; Abrams, R A

1996-03-01

A variety of clinical presentations can be encountered following compartment syndrome of the leg and foot. Deformity and functional impairment in the foot and ankle secondary to ischemia are determined by: 1) which leg compartments have been affected and to what degree extrinsic flexor or extensor "overpull" is exhibited, 2) degree of nerve injury sustained causing weakness or paralysis of extrinsic or intrinsic foot and ankle muscles, 3) which foot compartments have been affected and to what degree intrinsic "overpull" is exhibited, and 4) degree of sensory nerve injury leading to anesthesia, hypoesthesia, or hyperesthesia of the foot. Nonoperative therapy attempts to obtain or preserve joint mobility, increase strength, and provide corrective bracing and accommodative foot wear. Operative management is undertaken for treatment of residual nerve compression or refractory problematic deformities. Established surgical protocols are performed in a stepwise fashion, and include: 1) release of residual or secondary nerve compression; 2) release of fixed contractures, using infarct excision, myotendinous lengthening, muscle recession, or tenotomy; 3) tendon transfers or arthrodesis to increase function; and 4) osteotomy or amputation for severe, non-salvageable deformities.

Reliability and Validity of a New Method for Isometric Back Extensor Strength Evaluation Using A Hand-Held Dynamometer

PubMed Central

2017-01-01

Objective To investigate the reliability and validity of a new method for isometric back extensor strength measurement using a portable dynamometer. Methods A chair equipped with a small portable dynamometer was designed (Power Track II Commander Muscle Tester). A total of 15 men (mean age, 34.8±7.5 years) and 15 women (mean age, 33.1±5.5 years) with no current back problems or previous history of back surgery were recruited. Subjects were asked to push the back of the chair while seated, and their isometric back extensor strength was measured by the portable dynamometer. Test-retest reliability was assessed with intraclass correlation coefficient (ICC). For the validity assessment, isometric back extensor strength of all subjects was measured by a widely used physical performance evaluation instrument, BTE PrimusRS system. The limit of agreement (LoA) from the Bland-Altman plot was evaluated between two methods. Results The test-retest reliability was excellent (ICC=0.82; 95% confidence interval, 0.65–0.91). The Bland-Altman plots demonstrated acceptable agreement between the two methods: the lower 95% LoA was −63.1 N and the upper 95% LoA was 61.1 N. Conclusion This study shows that isometric back extensor strength measurement using a portable dynamometer has good reliability and validity. PMID:29201818

Comparing two methods to record maximal voluntary contractions and different electrode positions in recordings of forearm extensor muscle activity: Refining risk assessments for work-related wrist disorders.

PubMed

Dahlqvist, Camilla; Nordander, Catarina; Granqvist, Lothy; Forsman, Mikael; Hansson, Gert-Åke

2018-01-01

Wrist disorders are common in force demanding industrial repetitive work. Visual assessment of force demands have a low reliability, instead surface electromyography (EMG) may be used as part of a risk assessment for work-related wrist disorders. For normalization of EMG recordings, a power grip (hand grip) is often used as maximal voluntary contraction (MVC) of the forearm extensor muscles. However, the test-retest reproducibility is poor and EMG amplitudes exceeding 100% have occasionally been recorded during work. An alternative MVC is resisted wrist extension, which may be more reliable. To compare hand grip and resisted wrist extension MVCs, in terms of amplitude and reproducibility, and to examine the effect of electrode positioning. Twelve subjects participated. EMG from right forearm extensors, from four electrode pairs, was recorded during MVCs, on three separate occasions. The group mean EMG amplitudes for resisted wrist extension were 1.2-1.7 times greater than those for hand grip. Resisted wrist extension showed better reproducibility than hand grip. The results indicate that the use of resisted wrist extension is a more accurate measurement of maximal effort of wrist extensor contractions than using hand grip and should increase the precision in EMG recordings from forearm extensor muscles, which in turn will increase the quality of risk assessments that are based on these.

Relationships between maximal anaerobic power of the arms and legs and javelin performance.

PubMed

Bouhlel, E; Chelly, M S; Tabka, Z; Shephard, R

2007-06-01

The aim of this study was to examine relationships between maximal anaerobic power, as measured by leg and arm force-velocity tests, estimates of local muscle volume and javelin performance. Ten trained national level male javelin throwers (mean age 19.6+/- 2 years) participated in this study. Maximal anaerobic power, maximal force and maximal velocity were measured during leg (Wmax-L) and arm (Wmax-A) force-velocity tests, performed on appropriately modified forms of Monark cycle ergometer. Estimates of leg and arm muscle volume were made using a standard anthropometric kit. Maximal force of the leg (Fmax-L) was significantly correlated with estimated leg muscle volume (r=0.71, P<0.05). Wmax-L and Wmax-A were both significantly correlated with javelin performance (r=0.76, P<0.01; r=0.71, P <0.05, respectively). Maximal velocity of the leg (Vmax-L) was also significantly correlated with throwing performance (r=0.83; P<0.001). Wmax of both legs and arms were significantly correlated with javelin performance, the closest correlation being for Wmax-L; this emphasizes the importance of the leg muscles in this sport. Fmax-L and Vmax-L were related to muscle volume and to javelin performance, respectively. Force-velocity testing may have value in regulating conditioning and rehabilitation in sports involving throwing.

Fatigue and muscle-tendon stiffness after stretch-shortening cycle and isometric exercise.

PubMed

Toumi, Hechmi; Poumarat, Georges; Best, Thomas M; Martin, Alain; Fairclough, John; Benjamin, Mike

2006-10-01

The purpose of the present study was to compare vertical jump performance after 2 different fatigue protocols. In the first protocol, subjects performed consecutive sets of 10 repetitions of stretch-shortening cycle (SSC) contractions. In the second protocol, successive sets of 10 repetitions of isometric contractions were performed for 10 s with the knee at 90 degrees of flexion. The exercises were stopped when the subjects failed to reach 50% of their maximum voluntary isometric contractions. Maximal isometric force and maximal concentric power were assessed by performing supine leg presses, squat jumps, and drop jumps. Surface EMG was used to determine changes in muscle activation before and after fatigue. In both groups, the fatigue exercises reduced voluntary isometric force, maximal concentric power, and drop jump performance. Kinematic data showed a decrease in knee muscle-tendon stiffness accompanied by a lengthened ground contact time. EMG analysis showed that the squat and drop jumps were performed similarly before and after the fatigue exercise for both groups. Although it was expected that the stiffness would decrease more after SSC than after isometric fatigue (as a result of a greater alteration of the reflex sensitivity SSC), our results showed that both protocols had a similar effect on knee muscle stiffness during jumping exercises. Both fatigue protocols induced muscle fatigue, and the decrease in jump performance was linked to a decrease in the strength and stiffness of the knee extensor muscles.

Gait adaptations in patients with chronic posterior instability of the knee.

PubMed

Hooper, D M; Morrissey, M C; Crookenden, R; Ireland, J; Beacon, J P

2002-03-01

A retrospective analysis was performed to assess gait in individuals with a long history of posterior knee instability. Descriptive study. There are few studies in the literature concerning evaluation of the biomechanics of the knee in patients with knee posterior instability. Nine individuals with posterior knee instability and a matched control group of uninjured subjects were tested in regards to knee kinematics and kinetics while walking and ascending and descending stairs. The mean follow up time for the individuals with posterior instability was 11.1 years. Individual satisfaction with the knee was measured by having participants complete the Flandry (also known as Hughston Clinic) self-assessment questionnaire. It was found that patients with knee posterior instability who indicated a higher level of satisfaction on the Flandry score walked in a manner that demonstrated greater peak knee extensor torque during stance phase, while less satisfied patients with knee posterior instability demonstrated lower peak knee extensor torque. There was a significant correlation between the self-assessment score and the peak knee extensor torque during level walking (P=0.003). During stair ascent and descent, patients with posterior instability averaged lower knee extensor torque and power than the control subjects, but those differences were only statistically significant in power while descending stairs (P=0.048). Individuals with chronic knee posterior instability modify their gait, and the adaptation can be predicted based upon the individuals self-assessment of their knee using the Flandry questionnaire. These data suggest that gait retraining may be a valuable addition to the traditional muscle strengthening programs, which are commonly used during conservative management of knee posterior instability.

[Upright posture of man and morphologic evolution of the musculi extensores digitorum pedis with reference to evolutionary myology. III].

PubMed

Kaneff, A

1986-01-01

The following anatomical objects were studied with regard to myology during evolution: M. extensor hallucis longus (MEHL), M. extensor digitorum longus (MEDL) with M. peroneus tertius (MP III), M. peroneus brevis (MPB) with M. peroneus digiti V (MPD V), M. extensor hallucis brevis (MEHB), M. extensor digitorum brevis (MEDB), and the Retinaculum musculorum extensorum imum (RMEI). The study was carried out by the preparation of 3 different groups of material. The 1st group consists of lower extremities of humans. The number of the extremities differs for the particular objects between 151 and 358 (see page 381). The 2nd group of material consists of 122 Membra pelvina from Marsupialia, Insectivora, and Primates. Table 1 shows as well the mammalian species as the number of the studied extremities. The extremities of the 1st and 2nd group were preserved in an manner suitable for a macroscopic preparation. The 3rd group of material consists of 71 lower extremities from embryos and fetus. The lower legs and feet were stained either according to the method described by Morel and Bassal with eosin added or according to Weigert. From this material, complete series of cross sections were prepared. Table 2 shows the age of the embryos (VCL [mm]) as well as the number of the studied extremities. It is important that up to the age of 46 mm VCL the difference in the age of the embryos usually amounts from 0.5 to 1.0 mm. This small difference in the age of the embryos and fetus allows a very good follow up of the changes in construction during the organogenesis. The comparison of the 3 different groups shows the following changes for the above mentioned muscles: The M. extensor hallucis longus (MEHL) is a muscle which is not split. The same result applies for its tendon which inserts at the distal phalanx of the hallux. This primitive form of the muscle amounts actually to 51.12% in human beings. In 48.88% of the cases, additional tendons and muscles are formed by the MEHL. Most of these supplements are positioned on the medial side of the main tendon, only a few lie to the lateral side. For the supplement tendons, the medial one as well as the lateral one occasionally possess a muscle belly. The muscle of the medial tendon is split off from the proximal margin of the MEHL. The muscle of the lateral tendon is split off from the distal margin of the MEHL.(ABSTRACT TRUNCATED AT 400 WORDS)

Different fatigue-resistant leg muscles and EMG response during whole-body vibration.

PubMed

Simsek, Deniz

2017-12-01

The purpose of this study was to determine the effects of static whole-body vibration (WBV) on the Electromyograhic (EMG) responses of leg muscles, which are fatigue-resistant in different manner. The study population was divided into two groups according to the values obtained by the Fatigue Index [Group I: Less Fatigue Resistant (LFR), n=11; Group II: More Fatigue Resistant (MFR), n=11]. The repeated electromyographic (EMG) activities of four leg muscles were analyzed the following determinants: (1) frequency (30 Hz, 35 Hz and 40 Hz); (2) stance position (static squat position); (3) amplitude (2 mm and 4 mm) and (4) knee flexion angle (120°), (5) vertical vibration platform. Vibration data were analyzed using Minitab 16 (Minitab Ltd, State College, PA, USA). The significance level was set at p<.05. The study results showed that static WBV stimuli given at different frequencies and amplitudes resulted in a significant increase (p<.05) in compared, the LFR group showed significantly (1) higher rates of quadriceps femoris and hamstring muscle fatigue (p<.05), (2) higher levels of knee extensor and flexor torque (p<.05) and (3) higher percentage increases in EMG activation at higher frequencies (max at 40 Hz) and amplitudes (4 mm) (p<.05). The present study can be used for the optimal prescription of vibration exercise and can serve to guide the development of training programs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Contributions of muscles and passive dynamics to swing initiation over a range of walking speeds.

PubMed

Fox, Melanie D; Delp, Scott L

2010-05-28

Stiff-knee gait is a common walking problem in cerebral palsy characterized by insufficient knee flexion during swing. To identify factors that may limit knee flexion in swing, it is necessary to understand how unimpaired subjects successfully coordinate muscles and passive dynamics (gravity and velocity-related forces) to accelerate the knee into flexion during double support, a critical phase just prior to swing that establishes the conditions for achieving sufficient knee flexion during swing. It is also necessary to understand how contributions to swing initiation change with walking speed, since patients with stiff-knee gait often walk slowly. We analyzed muscle-driven dynamic simulations of eight unimpaired subjects walking at four speeds to quantify the contributions of muscles, gravity, and velocity-related forces (i.e. Coriolis and centrifugal forces) to preswing knee flexion acceleration during double support at each speed. Analysis of the simulations revealed contributions from muscles and passive dynamics varied systematically with walking speed. Preswing knee flexion acceleration was achieved primarily by hip flexor muscles on the preswing leg with assistance from biceps femoris short head. Hip flexors on the preswing leg were primarily responsible for the increase in preswing knee flexion acceleration during double support with faster walking speed. The hip extensors and abductors on the contralateral leg and velocity-related forces opposed preswing knee flexion acceleration during double support. Copyright 2010 Elsevier Ltd. All rights reserved.

Contributions of muscles and passive dynamics to swing initiation over a range of walking speeds

PubMed Central

Fox, Melanie D.; Delp, Scott L.

2010-01-01

Stiff-knee gait is a common walking problem in cerebral palsy characterized by insufficient knee flexion during swing. To identify factors that may limit knee flexion in swing, it is necessary to understand how unimpaired subjects successfully coordinate muscles and passive dynamics (gravity and velocity-related forces) to accelerate the knee into flexion during double support, a critical phase just prior to swing that establishes the conditions for achieving sufficient knee flexion during swing. It is also necessary to understand how contributions to swing initiation change with walking speed, since patients with stiff-knee gait often walk slowly. We analyzed muscle-driven dynamic simulations of eight unimpaired subjects walking at four speeds to quantify the contributions of muscles, gravity, and velocity-related forces (i.e. Coriolis and centrifugal forces) to preswing knee flexion acceleration during double support at each speed. Analysis of the simulations revealed contributions from muscles and passive dynamics varied systematically with walking speed. Preswing knee flexion acceleration was achieved primarily by hip flexor muscles on the preswing leg with assistance from biceps femoris short head. Hip flexors on the preswing leg were primarily responsible for the increase in preswing knee flexion acceleration during double support with faster walking speed. The hip extensors and abductors on the contralateral leg and velocity-related forces opposed preswing knee flexion acceleration during double support. PMID:20236644

Individual Muscle use in Hamstring Exercises by Soccer Players Assessed using Functional MRI.

PubMed

Fernandez-Gonzalo, R; Tesch, P A; Linnehan, R M; Kreider, R B; Di Salvo, V; Suarez-Arrones, L; Alomar, X; Mendez-Villanueva, A; Rodas, G

2016-06-01

This study used functional magnetic resonance imaging (fMRI) to compare individual muscle use in exercises aimed at preventing hamstring injuries. Thirty-six professional soccer players were randomized into 4 groups, each performing either Nordic hamstring, flywheel leg curl, Russian belt or conic-pulley exercise. MRIs were performed before and immediately after a bout of 4 sets of 8 repetitions. Pre-post exercise differences in contrast shift (T2) were analyzed for the long (BFLh) and short head (BFSh) of biceps femoris, semitendinosus (ST), semimembranosus (SM) and gracilis (GR) muscles. Flywheel leg curl increased (P<0.001) T2 of GR (95%), ST (65%), BFSh (51%) and BFLh (14%). After the Nordic hamstring, GR (39%), ST (16%) and BFSh (14%) showed increased T2 (P<0.001). Russian belt and conic-pulley exercise produced subtle (P<0.02) T2 increases of ST (9 and 6%, respectively) and BFLh (7 and 6%, respectively). Russian belt increased T2 of SM (7%). Among exercises examined, flywheel leg curl showed the most substantial hamstring and GR muscle use. However, no single exercise executed was able to increase T2 of all hamstring and synergist muscles analyzed. It is therefore suggested that multiple exercises must be carried out to bring in, and fully activate all knee flexors and hip extensors. © Georg Thieme Verlag KG Stuttgart · New York.

Supplemental Stimulation Improves Swing Phase Kinematics During Exoskeleton Assisted Gait of SCI Subjects With Severe Muscle Spasticity.

PubMed

Ekelem, Andrew; Goldfarb, Michael

2018-01-01

Spasticity is a common comorbidity associated with spinal cord injury (SCI). Robotic exoskeletons have recently emerged to facilitate legged mobility in people with motor complete SCI. Involuntary muscle activity attributed to spasticity, however, can prevent such individuals from using an exoskeleton. Specifically, although most exoskeleton technologies can accommodate low to moderate spasticity, the presence of moderate to severe spasticity can significantly impair gait kinematics when using an exoskeleton. In an effort to potentially enable individuals with moderate to severe spasticity to use exoskeletons more effectively, this study investigates the use of common peroneal stimulation in conjunction with exoskeleton gait assistance. The electrical stimulation is timed with the exoskeleton swing phase, and is intended to acutely suppress extensor spasticity through recruitment of the flexion withdrawal reflex (i.e., while the stimulation is activated) to enable improved exoskeletal walking. In order to examine the potential efficacy of this approach, two SCI subjects with severe extensor spasticity (i.e., modified Ashworth ratings of three to four) walked in an exoskeleton with and without supplemental stimulation while knee and hip motion was measured during swing phase. Stimulation was alternated on and off every ten steps to eliminate transient therapeutic effects, enabling the acute effects of stimulation to be isolated. These experiments indicated that common peroneal stimulation on average increased peak hip flexion during the swing phase of walking by 21.1° (236%) and peak knee flexion by 14.4° (56%). Additionally, use of the stimulation decreased the swing phase RMS motor current by 228 mA (15%) at the hip motors and 734 mA (38%) at the knee motors, indicating improved kinematics were achieved with reduced effort from the exoskeleton. Walking with the exoskeleton did not have a significant effect on modified Ashworth scores, indicating the common peroneal stimulation has only acute effects on suppressing extensor tone and aiding flexion. This preliminary data indicates that such supplemental stimulation may be used to improve the quality of movement provided by exoskeletons for persons with severe extensor spasticity in the lower limb.

Supplemental Stimulation Improves Swing Phase Kinematics During Exoskeleton Assisted Gait of SCI Subjects With Severe Muscle Spasticity

PubMed Central

Ekelem, Andrew; Goldfarb, Michael

2018-01-01

Spasticity is a common comorbidity associated with spinal cord injury (SCI). Robotic exoskeletons have recently emerged to facilitate legged mobility in people with motor complete SCI. Involuntary muscle activity attributed to spasticity, however, can prevent such individuals from using an exoskeleton. Specifically, although most exoskeleton technologies can accommodate low to moderate spasticity, the presence of moderate to severe spasticity can significantly impair gait kinematics when using an exoskeleton. In an effort to potentially enable individuals with moderate to severe spasticity to use exoskeletons more effectively, this study investigates the use of common peroneal stimulation in conjunction with exoskeleton gait assistance. The electrical stimulation is timed with the exoskeleton swing phase, and is intended to acutely suppress extensor spasticity through recruitment of the flexion withdrawal reflex (i.e., while the stimulation is activated) to enable improved exoskeletal walking. In order to examine the potential efficacy of this approach, two SCI subjects with severe extensor spasticity (i.e., modified Ashworth ratings of three to four) walked in an exoskeleton with and without supplemental stimulation while knee and hip motion was measured during swing phase. Stimulation was alternated on and off every ten steps to eliminate transient therapeutic effects, enabling the acute effects of stimulation to be isolated. These experiments indicated that common peroneal stimulation on average increased peak hip flexion during the swing phase of walking by 21.1° (236%) and peak knee flexion by 14.4° (56%). Additionally, use of the stimulation decreased the swing phase RMS motor current by 228 mA (15%) at the hip motors and 734 mA (38%) at the knee motors, indicating improved kinematics were achieved with reduced effort from the exoskeleton. Walking with the exoskeleton did not have a significant effect on modified Ashworth scores, indicating the common peroneal stimulation has only acute effects on suppressing extensor tone and aiding flexion. This preliminary data indicates that such supplemental stimulation may be used to improve the quality of movement provided by exoskeletons for persons with severe extensor spasticity in the lower limb. PMID:29910710

Effect of Exercise-Induced Enhancement of the Leg-Extensor Muscle-Tendon Unit Capacities on Ambulatory Mechanics and Knee Osteoarthritis Markers in the Elderly

PubMed Central

Karamanidis, Kiros; Oberländer, Kai Daniel; Niehoff, Anja; Epro, Gaspar; Brüggemann, Gert-Peter

2014-01-01

Objective Leg-extensor muscle weakness could be a key component in knee joint degeneration in the elderly because it may result in altered muscular control during locomotion influencing the mechanical environment within the joint. This work aimed to examine whether an exercise-induced enhancement of the triceps surae (TS) and quadriceps femoris (QF) muscle-tendon unit (MTU) capacities would affect mechanical and biological markers for knee osteoarthritis in the elderly. Methods Twelve older women completed a 14-week TS and QF MTU exercise intervention, which had already been established as increasing muscle strength and tendon stiffness. Locomotion mechanics and serum cartilage oligomeric matrix protein (COMP) levels were examined during incline walking. MTU mechanical properties were assessed using simultaneously ultrasonography and dynamometry. Results Post exercise intervention, the elderly had higher TS and QF contractile strength and tendon-aponeurosis stiffness. Regarding the incline gait task, the subjects demonstrated a lower external knee adduction moment and lower knee adduction angular impulse during the stance phase post-intervention. Furthermore, post-intervention compared to pre-intervention, the elderly showed lower external hip adduction moment, but revealed higher plantarflexion pushoff moment. The changes in the external knee adduction moment were significantly correlated with the improvement in ankle pushoff function. Serum COMP concentration increased in response to the 0.5-h incline walking exercise with no differences in the magnitude of increment between pre- and post-intervention. Conclusions This work emphasizes the important role played by the ankle pushoff function in knee joint mechanical loading during locomotion, and may justify the inclusion of the TS MTU in prevention programs aiming to positively influence specific mechanical markers for knee osteoarthritis in the elderly. However, the study was unable to show that COMP is amenable to change in the elderly following a 14-week exercise intervention and, therefore, the physiological benefit of improved muscle function for knee cartilage requires further investigation. PMID:24905024

Effect of exercise-induced enhancement of the leg-extensor muscle-tendon unit capacities on ambulatory mechanics and knee osteoarthritis markers in the elderly.

PubMed

Karamanidis, Kiros; Oberländer, Kai Daniel; Niehoff, Anja; Epro, Gaspar; Brüggemann, Gert-Peter

2014-01-01

Leg-extensor muscle weakness could be a key component in knee joint degeneration in the elderly because it may result in altered muscular control during locomotion influencing the mechanical environment within the joint. This work aimed to examine whether an exercise-induced enhancement of the triceps surae (TS) and quadriceps femoris (QF) muscle-tendon unit (MTU) capacities would affect mechanical and biological markers for knee osteoarthritis in the elderly. Twelve older women completed a 14-week TS and QF MTU exercise intervention, which had already been established as increasing muscle strength and tendon stiffness. Locomotion mechanics and serum cartilage oligomeric matrix protein (COMP) levels were examined during incline walking. MTU mechanical properties were assessed using simultaneously ultrasonography and dynamometry. Post exercise intervention, the elderly had higher TS and QF contractile strength and tendon-aponeurosis stiffness. Regarding the incline gait task, the subjects demonstrated a lower external knee adduction moment and lower knee adduction angular impulse during the stance phase post-intervention. Furthermore, post-intervention compared to pre-intervention, the elderly showed lower external hip adduction moment, but revealed higher plantarflexion pushoff moment. The changes in the external knee adduction moment were significantly correlated with the improvement in ankle pushoff function. Serum COMP concentration increased in response to the 0.5-h incline walking exercise with no differences in the magnitude of increment between pre- and post-intervention. This work emphasizes the important role played by the ankle pushoff function in knee joint mechanical loading during locomotion, and may justify the inclusion of the TS MTU in prevention programs aiming to positively influence specific mechanical markers for knee osteoarthritis in the elderly. However, the study was unable to show that COMP is amenable to change in the elderly following a 14-week exercise intervention and, therefore, the physiological benefit of improved muscle function for knee cartilage requires further investigation.

Body composition and cross-sectional areas of limb lean tissues in Olympic weight lifters.

PubMed

Kanehisa, H; Ikegawa, S; Fukunaga, T

1998-10-01

The cross-sectional area (CSAs) of bone and muscle tissues in the forearm, upper arm, lower leg, and thigh and body composition were determined by B-mode ultrasound and underwater weighing methods, respectively for 56 college Olympic weight lifters and 28 age-matched non-athletes to investigate the magnitude of musculoskeletal development in the strength-trained athletes belonging to the weight-classified sports event. The average value of fat-free mass (FFM) for the weight lifters ranked 12.6 kg above the regression line of FFM on stature for untrained subjects. In the weight lifters, however, the percentage of fat mass to body mass was also highly correlated to body mass index. Bone and muscle CSAs in every site were significantly larger in the weight lifter than in the untrained subjects with relative differences of 22 to 58% and 17 to 56%, respectively. Moreover, as a result of regression analysis for the mixed data from weight lifters and untrained subjects, significant correlation was found between bone and muscle CSAs in every site (r = 0.620 to 0.791, P < 0.05). The differences in lean (bone + muscle) CSA were still significant in all sites except for the lower leg even when the difference in body size was statistically controlled. The comparisons between the weight lifters and untrained subjects on the lean CSA ratios of site to site and muscle CSA ratios of flexors to extensors indicated that the weight lifters had achieved a high relative distribution of lean tissues in the arms and a dominant development in elbow and knee extensors. Thus, the present results suggested that participation in weight lifting exercises for a long period could increase bone CSA as well as muscle CSA, and induce in the participants a noticeable enlargement in given sites and muscle groups responsible for performing the Olympic lifts.

Exercise training, but not resveratrol, improves metabolic and inflammatory status in skeletal muscle of aged men

PubMed Central

Olesen, Jesper; Gliemann, Lasse; Biensø, Rasmus; Schmidt, Jakob; Hellsten, Ylva; Pilegaard, Henriette

2014-01-01

The aim was to investigate the metabolic and anti-inflammatory effects of resveratrol alone and when combined with exercise training in skeletal muscle of aged human subjects. Healthy, physically inactive men (60–72 years old) were randomized to either 8 weeks of daily intake of 250 mg resveratrol or placebo or to 8 weeks of high-intensity exercise training with 250 mg resveratrol or placebo. Before and after the interventions, resting blood samples and muscle biopsies were obtained and a one-legged knee-extensor endurance exercise test was performed. Exercise training increased skeletal muscle peroxisome proliferator-activated receptor-γ co-activator-1α mRNA ∼1.5-fold, cytochrome c protein ∼1.3-fold, cytochrome c oxidase I protein ∼1.5-fold, citrate synthase activity ∼1.3-fold, 3-hydroxyacyl-CoA dehydrogenase activity ∼1.3-fold, inhibitor of κB-α and inhibitor of κB-β protein content ∼1.3-fold and time to exhaustion in the one-legged knee-extensor endurance exercise test by ∼1.2-fold, with no significant additive or adverse effects of resveratrol on these parameters. Despite an overall ∼25% reduction in total acetylation level in skeletal muscle with resveratrol, no exclusive resveratrol-mediated metabolic effects were observed on the investigated parameters. Notably, however, resveratrol blunted an exercise training-induced decrease (∼20%) in protein carbonylation and decrease (∼40%) in tumour necrosis factor α mRNA content in skeletal muscle. In conclusion, resveratrol did not elicit metabolic improvements in healthy aged subjects; in fact, resveratrol even impaired the observed exercise training-induced improvements in markers of oxidative stress and inflammation in skeletal muscle. Collectively, this highlights the metabolic efficacy of exercise training in aged subjects and does not support the contention that resveratrol is a potential exercise mimetic in healthy aged subjects. PMID:24514907

Experimental effective shape control of a powered transfemoral prosthesis.

PubMed

Gregg, Robert D; Lenzi, Tommaso; Fey, Nicholas P; Hargrove, Levi J; Sensinger, Jonathon W

2013-06-01

This paper presents the design and experimental implementation of a novel feedback control strategy that regulates effective shape on a powered transfemoral prosthesis. The human effective shape is the effective geometry to which the biological leg conforms--through movement of ground reaction forces and leg joints--during the stance period of gait. Able-bodied humans regulate effective shapes to be invariant across conditions such as heel height, walking speed, and body weight, so this measure has proven to be a very useful tool for the alignment and design of passive prostheses. However, leg joints must be actively controlled to assume different effective shapes that are unique to tasks such as standing, walking, and stair climbing. Using our previous simulation studies as a starting point, we model and control the effective shape as a virtual kinematic constraint on the powered Vanderbilt prosthetic leg with a custom instrumented foot. An able-bodied subject used a by-pass adapter to walk on the controlled leg over ground and over a treadmill. These preliminary experiments demonstrate, for the first time, that effective shape (or virtual constraints in general) can be used to control a powered prosthetic leg.

Muscle mechanical advantage of human walking and running: implications for energy cost.

PubMed

Biewener, Andrew A; Farley, Claire T; Roberts, Thomas J; Temaner, Marco

2004-12-01

Muscular forces generated during locomotion depend on an animal's speed, gait, and size and underlie the energy demand to power locomotion. Changes in limb posture affect muscle forces by altering the mechanical advantage of the ground reaction force (R) and therefore the effective mechanical advantage (EMA = r/R, where r is the muscle mechanical advantage) for muscle force production. We used inverse dynamics based on force plate and kinematic recordings of humans as they walked and ran at steady speeds to examine how changes in muscle EMA affect muscle force-generating requirements at these gaits. We found a 68% decrease in knee extensor EMA when humans changed gait from a walk to a run compared with an 18% increase in hip extensor EMA and a 23% increase in ankle extensor EMA. Whereas the knee joint was extended (154-176 degrees) during much of the support phase of walking, its flexed position (134-164 degrees) during running resulted in a 5.2-fold increase in quadriceps impulse (time-integrated force during stance) needed to support body weight on the ground. This increase was associated with a 4.9-fold increase in the ground reaction force moment about the knee. In contrast, extensor impulse decreased 37% (P < 0.05) at the hip and did not change at the ankle when subjects switched from a walk to a run. We conclude that the decrease in limb mechanical advantage (mean limb extensor EMA) and increase in knee extensor impulse during running likely contribute to the higher metabolic cost of transport in running than in walking. The low mechanical advantage in running humans may also explain previous observations of a greater metabolic cost of transport for running humans compared with trotting and galloping quadrupeds of similar size.

Anthropometrical, physiological, and tracked power profiles of elite taekwondo athletes 9 weeks before the Olympic competition phase.

PubMed

Ball, Nick; Nolan, Emily; Wheeler, Keane

2011-10-01

Physiological, anthropometric, and power profiling data were retrospectively analyzed from 4 elite taekwondo athletes from the Australian National Olympic team 9 weeks from Olympic departure. Power profiling data were collected weekly throughout the 9-week period. Anthropometric skinfolds generated a lean mass index (LMI). Physiological tests included a squat jump and bench throw power profile, bleep test, 20-m sprint test, running VO2max test, and bench press and squat 3 repetition maximum (3RM) strength tests. After this, the athletes power, velocity, and acceleration profile during unweighted squat jumps and single-leg jumps were tracked using a linear position transducer. Increases in power, velocity, and acceleration between weeks and bilateral comparisons were analyzed. Athletes had an LMI of 37.1 ± 0.4 and were 173.9 ± 0.2 m and 67 ± 1.1 kg. Relatively weaker upper body (56 ± 11.97 kg 3RM bench press) compared to lower body strength (88 ± 2.89 kg 3RM squat) was shown alongside a VO2max of 53.29 ml(-1)·min(-1)·kg, and a 20-m sprint time of 3.37 seconds. Increases in all power variables for single-leg squat and squat jumps were found from the first session to the last. Absolute peak power in single-leg squat jumps increased by 13.4-16% for the left and right legs with a 12.9% increase in squat jump peak power. Allometrically scaled peak power showed greater increases for single-leg (right leg: 18.55%; left: 23.49%) and squat jump (14.49%). The athlete's weight did not change significantly throughout the 9-week mesocycle. Progressions in power increases throughout the weeks were undulating and can be related to the intensity of the prior week's training and athlete injury. This analysis has shown that a 9-week mesocycle before Olympic departure that focuses on core lifts has the ability to improve power considerably.

Squatting Exercises in Older Adults: Kinematic and Kinetic Comparisons

PubMed Central

FLANAGAN, SEAN; SALEM, GEORGE J.; WANG, MAN-YING; SANKER, SERENA E.; GREENDALE, GAIL A.

2012-01-01

Purpose Squatting activities may be used, within exercise programs, to preserve physical function in older adults. This study characterized the lower-extremity peak joint angles, peak moments, powers, work, impulse, and muscle recruitment patterns (electromyographic; EMG) associated with two types of squatting activities in elders. Methods Twenty-two healthy, older adults (ages 70–85) performed three trials each of: 1) a squat to a self-selected depth (normal squat; SQ) and 2) a squat onto a chair with a standardized height of 43.8 cm (chair squat; CSQ). Descending and ascending phase joint kinematics and kinetics were obtained using a motion analysis system and inverse dynamics techniques. Results were averaged across the three trials. A 2 × 2 (activity × phase) ANOVA with repeated measures was used to examine the biomechanical differences among the two activities and phases. EMG temporal characteristics were qualitatively examined. Results CSQ generated greater hip flexion angles, peak moments, power, and work, whereas SQ generated greater knee and ankle flexion angles, peak moments, power, and work. SQ generated a greater knee extensor impulse, a greater plantar flexor impulse and a greater total support impulse. The EMG temporal patterns were consistent with the kinetic data. Conclusions The results suggest that, with older adults, CSQ places greater demand on the hip extensors, whereas SQ places greater demand on the knee extensors and ankle plantar flexors. Clinicians may use these discriminate findings to more effectively target specific lower-extremity muscle groups when prescribing exercise for older adults. PMID:12673148

Associations Between Balance and Muscle Strength, Power Performance in Male Youth Athletes of Different Maturity Status.

PubMed

Hammami, Raouf; Chaouachi, Anis; Makhlouf, Issam; Granacher, Urs; Behm, David G

2016-11-01

Balance, strength and power relationships may contain important information at various maturational stages to determine training priorities. The objective was to examine maturity-specific relationships of static/dynamic balance with strength and power measures in young male athletes. Soccer players (N = 130) aged 10-16 were assessed with the Stork and Y balance (YBT) tests. Strength/power measures included back extensor muscle strength, standing long jump (SLJ), countermovement jump (CMJ), and 3-hop jump tests. Associations between balance with strength/power variables were calculated according to peak-height-velocity (PHV). There were significant medium-large sized correlations between all balance measures with back extensor strength (r = .486-.791) and large associations with power (r = .511-.827). These correlation coefficients were significantly different between pre-PHV and circa PHV as well as pre-PHV and post-PHV with larger associations in the more mature groups. Irrespective of maturity-status, SLJ was the best strength/power predictor with the highest proportion of variance (12-47%) for balance (i.e., Stork eyes opened) and the YBT was the best balance predictor with the highest proportion of variance (43-78%) for all strength/power variables. The associations between balance and muscle strength/power measures in youth athletes that increase with maturity may imply transfer effects from balance to strength/power training and vice versa in youth athletes.

Association of Quadriceps Strength and Psychosocial Factors With Single-Leg Hop Performance in Patients With Meniscectomy.

PubMed

Hsu, Chao-Jung; George, Steven Z; Chmielewski, Terese L

2016-12-01

Clinicians use the single-leg hop test to assess readiness for return to sports after knee injury. Few studies have reported the results of single-leg hop testing after meniscectomy. Additionally, the contributions of impairments in quadriceps strength and psychosocial factors to single-leg hop performance are unknown. To compare single-leg hop performance (distance and landing mechanics) between limbs and to examine the association of single-leg hop performance with quadriceps strength and psychosocial factors in patients with meniscectomy. Descriptive laboratory study. A total of 22 subjects who underwent meniscectomy for traumatic meniscal tears received either standard rehabilitation alone or with additional quadriceps strengthening. Testing was conducted immediately postrehabilitation and at 1 year postsurgery. A single-leg hop test was performed bilaterally, and hop distance was used to create a hop symmetry index. Landing mechanics (peak knee flexion angle, knee extension moment, and peak vertical ground-reaction force) were analyzed with a motion-capture system and a force plate. An isokinetic dynamometer (60 deg/s) assessed knee extensor peak torque and rate of torque development (RTD 0-200ms and RTD 0-peak torque ). Questionnaires assessed fear of reinjury (Tampa Scale for Kinesiophobia [TSK-11]) and self-efficacy (Knee Activity Self-Efficacy [KASE]). Rehabilitation groups did not significantly differ in single-leg hop performance; therefore, groups were combined for further analyses. The mean hop symmetry index was 88.6% and 98.9% at postrehabilitation and 1 year postsurgery, respectively. Compared with the nonsurgical limb, the surgical limb showed decreased peak knee flexion angle at postrehabilitation and decreased knee extension moment at 1 year postsurgery. The hop symmetry index was positively associated with peak torque, RTD 0-200ms , and the KASE score at postrehabilitation. Moreover, at postrehabilitation, the peak knee flexion angle was positively associated with peak torque and RTD 0-200ms , and the knee extension moment was positively associated with RTD 0-200ms . At 1 year postsurgery, peak knee flexion angle and knee extension moment were both positively associated with peak torque, RTD 0-200ms , and RTD 0-peak torque . Although the hop symmetry index could be considered satisfactory for returning to sports, asymmetries in landing mechanics still exist in the first year postmeniscectomy. Greater quadriceps strength was associated with greater single-leg hop distance and better landing mechanics at both postrehabilitation and 1 year postsurgery. Knee activity self-efficacy was the only psychosocial factor associated with single-leg hop performance and isolated to a positive association with single-leg hop distance at postrehabilitation. Rate of development is not typically measured in the clinic but can be an additional quadriceps measure to monitor for single-leg hop performance. Quadriceps strength and psychosocial factors appear to have separate influence on single-leg hop performance after meniscectomy, which has implications for developing appropriate interventions for optimal single-leg hop performance.

Association of Quadriceps Strength and Psychosocial Factors With Single-Leg Hop Performance in Patients With Meniscectomy

PubMed Central

Hsu, Chao-Jung; George, Steven Z.; Chmielewski, Terese L.

2016-01-01

Background: Clinicians use the single-leg hop test to assess readiness for return to sports after knee injury. Few studies have reported the results of single-leg hop testing after meniscectomy. Additionally, the contributions of impairments in quadriceps strength and psychosocial factors to single-leg hop performance are unknown. Purpose: To compare single-leg hop performance (distance and landing mechanics) between limbs and to examine the association of single-leg hop performance with quadriceps strength and psychosocial factors in patients with meniscectomy. Study Design: Descriptive laboratory study. Methods: A total of 22 subjects who underwent meniscectomy for traumatic meniscal tears received either standard rehabilitation alone or with additional quadriceps strengthening. Testing was conducted immediately postrehabilitation and at 1 year postsurgery. A single-leg hop test was performed bilaterally, and hop distance was used to create a hop symmetry index. Landing mechanics (peak knee flexion angle, knee extension moment, and peak vertical ground-reaction force) were analyzed with a motion-capture system and a force plate. An isokinetic dynamometer (60 deg/s) assessed knee extensor peak torque and rate of torque development (RTD0-200ms and RTD0–peak torque). Questionnaires assessed fear of reinjury (Tampa Scale for Kinesiophobia [TSK-11]) and self-efficacy (Knee Activity Self-Efficacy [KASE]). Results: Rehabilitation groups did not significantly differ in single-leg hop performance; therefore, groups were combined for further analyses. The mean hop symmetry index was 88.6% and 98.9% at postrehabilitation and 1 year postsurgery, respectively. Compared with the nonsurgical limb, the surgical limb showed decreased peak knee flexion angle at postrehabilitation and decreased knee extension moment at 1 year postsurgery. The hop symmetry index was positively associated with peak torque, RTD0-200ms, and the KASE score at postrehabilitation. Moreover, at postrehabilitation, the peak knee flexion angle was positively associated with peak torque and RTD0-200ms, and the knee extension moment was positively associated with RTD0-200ms. At 1 year postsurgery, peak knee flexion angle and knee extension moment were both positively associated with peak torque, RTD0-200ms, and RTD0–peak torque. Conclusion: Although the hop symmetry index could be considered satisfactory for returning to sports, asymmetries in landing mechanics still exist in the first year postmeniscectomy. Greater quadriceps strength was associated with greater single-leg hop distance and better landing mechanics at both postrehabilitation and 1 year postsurgery. Knee activity self-efficacy was the only psychosocial factor associated with single-leg hop performance and isolated to a positive association with single-leg hop distance at postrehabilitation. Clinical Relevance: Rate of development is not typically measured in the clinic but can be an additional quadriceps measure to monitor for single-leg hop performance. Quadriceps strength and psychosocial factors appear to have separate influence on single-leg hop performance after meniscectomy, which has implications for developing appropriate interventions for optimal single-leg hop performance. PMID:28210647

Exposure to extremely low frequency electromagnetic fields alters the behaviour, physiology and stress protein levels of desert locusts

PubMed Central

Wyszkowska, Joanna; Shepherd, Sebastian; Sharkh, Suleiman; Jackson, Christopher W.; Newland, Philip L.

2016-01-01

Electromagnetic fields (EMFs) are present throughout the modern world and are derived from many man-made sources including overhead transmission lines. The risks of extremely-low frequency (ELF) electromagnetic fields are particularly poorly understood especially at high field strengths as they are rarely encountered at ground level. Flying insects, however, can approach close to high field strength transmission lines prompting the question as to how these high levels of exposure affect behaviour and physiology. Here we utilise the accessible nervous system of the locust to ask how exposure to high levels of ELF EMF impact at multiple levels. We show that exposure to ELF EMFs above 4 mT leads to reduced walking. Moreover, intracellular recordings from an identified motor neuron, the fast extensor tibiae motor neuron, show increased spike latency and a broadening of its spike in exposed animals. In addition, hind leg kick force, produced by stimulating the extensor tibiae muscle, was reduced following exposure, while stress-protein levels (Hsp70) increased. Together these results suggest that ELF EMF exposure has the capacity to cause dramatic effects from behaviour to physiology and protein expression, and this study lays the foundation to explore the ecological significance of these effects in other flying insects. PMID:27808167

Relation between isokinetic muscle strength and functional capacity in recreational athletes with chondromalacia patellae

PubMed Central

Yildiz, Y; Aydin, T; Sekir, U; Cetin, C; Ors, F; Alp, K

2003-01-01

Objectives: To investigate the effects of isokinetic exercise on pain and functional test scores of recreational athletes with chondromalacia patellae (CMP) and to examine the correlation between isokinetic parameters and functional tests or pain score. Methods: The functional ability of 30 recreational athletes with unilateral CMP was evaluated using six different tests. Pain scores were assessed during daily activities before and after the treatment protocol. Isokinetic exercise sessions were carried out at angular velocities of 60°/s (25–90° range of flexion) and 180°/s (full range). These sessions were repeated three times a week for six weeks. Results: Quadriceps and hamstring peak torque, total work, and endurance ratios had improved significantly after the treatment, as did the functional parameters and pain scores. There was a poor correlation between the extensor endurance ratio and one leg standing test. A moderate correlation between the visual analogue scale and the extensor endurance ratio or flexion endurance ratio was also found. Conclusions: The isokinetic exercise programme used in this study had a positive effect on muscle strength, pain score, and functional ability of knees with CMP. The improvement in the functional capacity did not correlate with the isokinetic parameters. PMID:14665581

Muscular activity and torque of the foot dorsiflexor muscles during decremental isometric test: A cross-sectional study.

PubMed

Ruiz-Muñoz, Maria; González-Sánchez, Manuel; Martín-Martín, Jaime; Cuesta-Vargas, Antonio I

2017-06-01

To analyse the torque variation level that could be explained by the muscle activation (EMG) amplitude of the three major foot dorsiflexor muscles (tibialis anterior (TA), extensor digitorum longus (EDL), extensor hallucis longus (EHL)) during isometric foot dorsiflexion at different intensities. In a cross-sectional study, forty-one subjects performed foot dorsiflexion at 100%, 75%, 50% and 25% of maximal voluntary contractions (MVC) with the hip and knee flexed 90° and the ankle in neutral position (90° between leg and foot). Three foot dorsiflexions were performed for each intensity. Outcome variables were: maximum (100% MVC) and relative torque (75%, 50%, 25% MVC), maximum and relative EMG amplitude. A linear regression analysis was calculated for each intensity of the isometric foot dorsiflexion. The degree of torque variation (dependent variable) from the independent variables explain (EMG amplitude of the three major foot dorsiflexor muscles) the increases when the foot dorsiflexion intensity is increased, with values of R 2 that range from 0.194 (during 25% MVC) to 0.753 (during 100% MVC). The reliability of the outcome variables was excellent. The EMG amplitude of the three main foot dorsiflexors exhibited more variance in the dependent variable (torque) when foot dorsiflexion intensity increases. Copyright © 2016 Elsevier Ltd. All rights reserved.

Short physical performance battery for middle-aged and older adult cardiovascular disease patients: implication for strength tests and lower extremity morphological evaluation.

PubMed

Yasuda, Tomohiro; Fukumura, Kazuya; Nakajima, Toshiaki

2017-04-01

[Purpose] To examine if the SPPB is higher with healthy subjects than outpatients, which was higher than inpatients and if the SPPB can be validated assessment tool for strength tests and lower extremity morphological evaluation in cardiovascular disease patients. [Subjects and Methods] Twenty-four middle aged and older adults with cardiovascular disease were recruited from inpatient and outpatient facilities and assigned to separate experimental groups. Twelve age-matched healthy volunteers were assigned to a control group. SPPB test was used to assess balance and functional motilities. The test outcomes were compared with level of care (inpatient vs. outpatient), physical characteristics, strength and lower extremity morphology. [Results] Total SPPB scores, strength tests (knee extensor muscle strength), and lower extremity morphological evaluation (muscle thickness of anterior and posterior mid-thigh and posterior lower-leg) were greater in healthy subjects and outpatients groups compared with inpatients. To predict total Short Physical Performance Battery scores, the predicted knee extension and anterior mid-thigh muscle thickness were calculated. [Conclusion] The SPPB is an effective tool as the strength tests and lower extremity morphological evaluation for middle-aged and older adult cardiovascular disease patients. Notably, high knee extensor muscle strength and quadriceps femoris muscle thickness are positively associated with high SPPB scores.

Health-related quality of life and fitness of the caregiver of patient with dementia.

PubMed

Gusi, Narcís; Prieto, Josue; Madruga, Miguel; Garcia, Jose M; Gonzalez-Guerrero, Jose L

2009-06-01

: The aim was to assess the health-related quality of life and physical fitness of women who care for a relative with dementia compared with an age-matched group of noncaregiver women, for the purpose of designing adequate physical exercise programs. : A cross-sectional study was conducted in Extremadura, Spain, with 54 caregivers and 56 noncaregivers who were assessed by the SF-36 questionnaire and a battery of fitness tests. : The reported mental health (mental, emotional role, and social categories of SF-36) of the carers was 22% lower than that of the noncaregivers, but both groups were similar in physical health. On the whole, the reported general health of the carers was 11% lower than that of the noncarers. In fitness outcomes, caregivers had better scores in body composition, bimanual strength, and leg strength but lower scores in the endurance capacity of the trunk extensor muscles. : Relative to the standard exercise programs of the general population, exercise programs for female caregivers should be more focused on preventing back pain by developing the endurance strength of the trunk extensors. A supervised exercise program including the interaction between caregiver and health professional could also help to minimize the psychosocial components that affect the health-related quality of life.

Hemodynamic and hormonal responses to lower body negative pressure in men with varying profiles of strength and aerobic power

NASA Technical Reports Server (NTRS)

Convertino, V. A.; Mathes, K. L.; Lasley, M. L.; Tomaselli, C. M.; Frey, M. A.; Hoffler, G. W.

1993-01-01

Hemodynamic, cardiac, and hormonal responses to lower-body negative pressure (LBNP) were examined in 24 healthy men to test the hypothesis that responsiveness of reflex control of blood pressure during orthostatic challenge is associated with interactions between strength and aerobic power. Subjects underwent treadmill tests to determine peak oxygen uptake (VO2max) and isokinetic dynamometer tests to determine knee extensor strength. Based on predetermined criteria, subjects were classified into one of four fitness profiles of six subjects each, matched for age, height, and body mass: (a) low strength/average aerobic fitness, (b) low strength/high aerobic fitness, (c) high strength/average aerobic fitness, and (d) high strength/high aerobic fitness. Following 90 min of 0.11 rad (6 degrees) head-down tilt (HDT), each subject underwent graded LBNP to -6.7 kPa or presyncope, with maximal duration 15 min, while hemodynamic, cardiac, and hormonal responses were measured. All groups exhibited typical hemodynamic, hormonal, and fluid shift responses during LBNP, with no intergroup differences between high and low strength characteristics. Subjects with high aerobic power exhibited greater (P < 0.05) stroke volume and lower (P < 0.05) heart rate, vascular peripheral resistance, and mean arterial pressure during rest, HDT, and LBNP. Seven subjects, distributed among the four fitness profiles, became presyncopal. These subjects showed greatest reduction in mean arterial pressure during LBNP, had greater elevations in vasopressin, and lesser increases in heart rate and peripheral resistance. Neither VO2max nor leg strength were associated with fall in arterial pressure or with syncopal episodes. We conclude that interactions between aerobic and strength fitness characteristics do not influence responses to LBNP challenge.

A biological micro actuator: graded and closed-loop control of insect leg motion by electrical stimulation of muscles.

PubMed

Cao, Feng; Zhang, Chao; Vo Doan, Tat Thang; Li, Yao; Sangi, Daniyal Haider; Koh, Jie Sheng; Huynh, Ngoc Anh; Bin Aziz, Mohamed Fareez; Choo, Hao Yu; Ikeda, Kazuo; Abbeel, Pieter; Maharbiz, Michel M; Sato, Hirotaka

2014-01-01

In this study, a biological microactuator was demonstrated by closed-loop motion control of the front leg of an insect (Mecynorrhina torquata, beetle) via electrical stimulation of the leg muscles. The three antagonistic pairs of muscle groups in the front leg enabled the actuator to have three degrees of freedom: protraction/retraction, levation/depression, and extension/flexion. We observed that the threshold amplitude (voltage) required to elicit leg motions was approximately 1.0 V; thus, we fixed the stimulation amplitude at 1.5 V to ensure a muscle response. The leg motions were finely graded by alternation of the stimulation frequencies: higher stimulation frequencies elicited larger leg angular displacement. A closed-loop control system was then developed, where the stimulation frequency was the manipulated variable for leg-muscle stimulation (output from the final control element to the leg muscle) and the angular displacement of the leg motion was the system response. This closed-loop control system, with an optimized proportional gain and update time, regulated the leg to set at predetermined angular positions. The average electrical stimulation power consumption per muscle group was 148 µW. These findings related to and demonstrations of the leg motion control offer promise for the future development of a reliable, low-power, biological legged machine (i.e., an insect-machine hybrid legged robot).

The influence of caffeine ingestion on strength and power performance in female team-sport players.

PubMed

Ali, Ajmol; O'Donnell, Jemma; Foskett, Andrew; Rutherfurd-Markwick, Kay

2016-01-01

The aim of this study was to examine the influence of caffeine supplementation on knee flexor and knee extensor strength before, during and after intermittent running exercise in female team-sport players taking oral contraceptive steroids (OCS). Ten healthy females (24 ± 4 years; 59.7 ± 3.5 kg; undertaking 2-6 training sessions per week) taking low-dose monophasic oral contraceptives of the same hormonal composition took part in a randomised, double-blind, placebo-controlled crossover-design trial. Sixty minutes following the ingestion of a capsule containing 6 mg∙kg -1 body mass anhydrous caffeine or artificial sweetener (placebo), participants completed a 90-min intermittent treadmill-running protocol. Isometric strength performance and eccentric and concentric strength and power of the knee flexors and knee extensors (using isokinetic dynamometer), as well as countermovement jump (CMJ), was measured before, during and after the exercise protocol, as well as ~12 h post-exercise. Blood samples were taken before, during and post-exercise to measure glucose, insulin and free fatty acids (FFA). Caffeine supplementation significantly increased eccentric strength of the knee flexors ( P  < 0.05) and eccentric power of both the knee flexors ( P  < 0.05) and extensors ( P  < 0.05). However, there was no effect on isometric or concentric parameters, or CMJ performance. FFA was elevated with caffeine supplementation over time ( P  < 0.05) while levels of glucose and insulin were not affected by caffeine intake. Caffeine supplementation increased eccentric strength and power in female team-sport players taking OCS both during an intermittent running protocol and the following morning.

Using Maximal Isometric Force to Determine the Optimal Load for Measuring Dynamic Muscle Power

NASA Technical Reports Server (NTRS)

Spiering, Barry A.; Lee, Stuart M. C.; Mulavara, Ajitkumar P.; Bentley, Jason R.; Nash, Roxanne E.; Sinka, Joseph; Bloomberg, Jacob J.

2009-01-01

Maximal power output occurs when subjects perform ballistic exercises using loads of 30-50% of one-repetition maximum (1-RM). However, performing 1-RM testing prior to power measurement requires considerable time, especially when testing involves multiple exercises. Maximal isometric force (MIF), which requires substantially less time to measure than 1-RM, might be an acceptable alternative for determining the optimal load for power testing. PURPOSE: To determine the optimal load based on MIF for maximizing dynamic power output during leg press and bench press exercises. METHODS: Twenty healthy volunteers (12 men and 8 women; mean +/- SD age: 31+/-6 y; body mass: 72 +/- 15 kg) performed isometric leg press and bench press movements, during which MIF was measured using force plates. Subsequently, subjects performed ballistic leg press and bench press exercises using loads corresponding to 20%, 30%, 40%, 50%, and 60% of MIF presented in randomized order. Maximal instantaneous power was calculated during the ballistic exercise tests using force plates and position transducers. Repeated-measures ANOVA and Fisher LSD post hoc tests were used to determine the load(s) that elicited maximal power output. RESULTS: For the leg press power test, six subjects were unable to be tested at 20% and 30% MIF because these loads were less than the lightest possible load (i.e., the weight of the unloaded leg press sled assembly [31.4 kg]). For the bench press power test, five subjects were unable to be tested at 20% MIF because these loads were less than the weight of the unloaded aluminum bar (i.e., 11.4 kg). Therefore, these loads were excluded from analysis. A trend (p = 0.07) for a main effect of load existed for the leg press exercise, indicating that the 40% MIF load tended to elicit greater power output than the 60% MIF load (effect size = 0.38). A significant (p . 0.05) main effect of load existed for the bench press exercise; post hoc analysis indicated that the effect of load on power output was: 30% > 40% > 50% = 60%. CONCLUSION: Loads of 40% and 30% of MIF elicit maximal power output during dynamic leg presses and bench presses, respectively. These findings are similar to those obtained when loading is based on 1-RM.

Haemodynamic responses to dehydration in the resting and exercising human leg.

PubMed

Pearson, James; Kalsi, Kameljit K; Stöhr, Eric J; Low, David A; Barker, Horace; Ali, Leena; González-Alonso, José

2013-06-01

Dehydration and hyperthermia reduces leg blood flow (LBF), cardiac output ([Formula: see text]) and arterial pressure during whole-body exercise. It is unknown whether the reductions in blood flow are associated with dehydration-induced alterations in arterial blood oxygen content (C aO2) and O2-dependent signalling. This study investigated the impact of dehydration and concomitant alterations in C aO2 upon LBF and [Formula: see text]. Haemodynamics, arterial and femoral venous blood parameters and plasma [ATP] were measured at rest and during one-legged knee-extensor exercise in 7 males in four conditions: (1) control, (2) mild dehydration, (3) moderate dehydration, and (4) rehydration. Relative to control, C aO2 and LBF increased with dehydration at rest and during exercise (C aO2: from 199 ± 1 to 208 ± 2, and 202 ± 2 to 210 ± 2 ml L(-1) and LBF: from 0.38 ± 0.04 to 0.77 ± 0.09, and 1.64 ± 0.09 to 1.88 ± 0.1 L min(-1), respectively). Similarly, [Formula: see text] was unchanged or increased with dehydration at rest and during exercise, whereas arterial and leg perfusion pressures declined. Following rehydration, C aO2 declined (to 193 ± 2 mL L(-1)) but LBF remained elevated. Alterations in LBF were unrelated to C aO2 (r (2) = 0.13-0.27, P = 0.48-0.64) and plasma [ATP]. These findings suggest dehydration and concomitant alterations in C aO2 do not compromise LBF despite reductions in plasma [ATP]. While an additive or synergistic effect cannot be excluded, reductions in LBF during exercise with dehydration may not necessarily be associated with alterations in C aO2 and/or intravascular [ATP].

Muscular strength profile in Tunisian male national judo team

PubMed Central

Ghrairi, Mourad; Hammouda, Omar; Malliaropoulos, Nikos

2014-01-01

Summary Background: it is well established that muscle strength is a determinant factor in judo. However, little data are available for African athletes. Therefore, the aim of this study was to provide reference data of the muscular strength profile (MSP) for an African team, Tunisian judo team. Methods: the study was conducted among ten international judo athletes from Tunisia. To determine their MSP, we used an isokinetic dynamometer to assess Hamstrings, Quadriceps of both knees and external, internal rotators of both shoulders. The angular velocities of the assessments were; 90, 180, 240°/s for the knees and 60, 120°/s for the shoulders. Results: MSP was determined based on two parameters; the maximum peak torque (PT) of each muscle and the ratio agonistic/antagonistic muscles (R). The knee extensors and flexors in the “supporting leg” had higher PT than in the “attacking leg”; respectively, 245N.m versus 237 (p<0.05) and 147 N.m versus 145 (p>0.05). R was normal for both legs. Furthermore, both rotators of the dominant shoulder had higher PT; 84 N.m versus 71 for the internal rotators (p<0.05) and 34,7 N.m versus 29,0 for the lateral rotators (p<0.05). Inversely, R was higher in the non-dominant side; 45% versus 35, p<0.05). Conclusion: the MSP of the selected elites Tunisian judo athletes was characterized by 3 major features; a strength of the quadriceps in the standing leg significantly higher than in the attacking leg, a normal muscular balance Hamstrings/quadriceps in both legs and a strength of the shoulder’ rotators higher in the dominant side. PMID:25332926

Effects of low-level laser therapy applied before or after plyometric exercise on muscle damage markers: randomized, double-blind, placebo-controlled trial.

PubMed

Fritsch, Carolina Gassen; Dornelles, Maurício Pinto; Severo-Silveira, Lucas; Marques, Vanessa Bernardes; Rosso, Isabele de Albuquerque; Baroni, Bruno Manfredini

2016-12-01

Promising effects of phototherapy on markers of exercise-induced muscle damage has been already demonstrated in constant load or isokinetic protocols. However, its effects on more functional situations, such as plyometric exercises, and when is the best moment to apply this treatment (pre- or post-exercise) remain unclear. Therefore, the purpose of this study was to investigate the effect of low-level laser therapy (LLLT) before or after plyometric exercise on quadriceps muscle damage markers. A randomized, double-blinded, placebo-controlled trial was conducted with 24 healthy men, 12 at pre-exercise treatment group and 12 at post-exercise treatment group. Placebo and LLLT (810 nm, 200 mW per diode, 6 J per diode, 240 J per leg) were randomly applied on right/left knee extensor muscles of each volunteer before/after a plyometric exercise protocol. Muscular echo intensity (ultrasonography images), soreness (visual analogue scale - VAS), and strength impairment (maximal voluntary contraction - MVC) were assessed at baseline, 24, 48, and 72 h post-exercise. Legs treated with LLLT before or after exercise presented significantly smaller increments of echo intensity (values up to 1 %) compared to placebo treatments (increased up to ∼7 %). No significant treatment effect was found for VAS and MVC, although a trend toward better results on LLLT legs have been found for VAS (mean values up to 30 % lesser than placebo leg). In conclusion, LLLT applied before or after plyometric exercise reduces the muscle echo intensity response and possibly attenuates the muscle soreness. However, these positive results were not observed on strength impairment.

Electromyographic analyses of muscle pre-activation induced by single joint exercise.

PubMed

Júnior, Valdinar A R; Bottaro, Martim; Pereira, Maria C C; Andrade, Marcelino M; P Júnior, Paulo R W; Carmo, Jake C

2010-01-01

To investigate whether performing a low-intensity, single-joint exercises for knee extensors was an efficient strategy for increasing the number of motor units recruited in the vastus lateralis muscle during a subsequent multi-joint exercises. Nine healthy male participants (23.33+/-3.46 yrs) underwent bouts of exercise in which knee extension and 45 degrees , and leg press exercises were performed in sequence. In the low-intensity bout (R30), 15 unilateral knee extensions were performed, followed by 15 repetitions of the leg presses at 30% and 60% of one maximum repetition load (1-MR), respectively. In the high-intensity bout (R60), the same sequence was performed, but the applied load was 60% of 1-MR for both exercises. A single set of 15 repetitions of the leg press at 60% of 1-MR was performed as a control exercise (CR). The surface electromyographic signals of the vastus lateralis muscle were recorded by means of a linear electrode array. The root mean square (RMS) values were determined for each repetition of the leg press, and linear regressions were calculated from these results. The slopes of the straight lines obtained were then normalized using the linear coefficients of the regression equations and compared using one-way ANOVAs for repeated measures. The slopes observed in the CR were significantly lower than those in the R30 and R60 (p<0.05). The results indicated that the recruitment of motor units was more effective when a single-joint exercise preceded the multi-joint exercise. Article registered in the Australian New Zealand Clinical Trials Registry (ANZCTR) under the number ACTRN12609000413224.

Potentiation of cGMP signaling increases oxygen delivery and oxidative metabolism in contracting skeletal muscle of older but not young humans

PubMed Central

Nyberg, Michael; Piil, Peter; Egelund, Jon; Sprague, Randy S; Mortensen, Stefan P; Hellsten, Ylva

2015-01-01

Aging is associated with progressive loss of cardiovascular and skeletal muscle function. The impairment in physical capacity with advancing age could be related to an insufficient peripheral O2 delivery to the exercising muscles. Furthermore, the mechanisms underlying an impaired blood flow regulation remain unresolved. Cyclic guanosine monophosphate (cGMP) is one of the main second messengers that mediate smooth muscle vasodilation and alterations in cGMP signaling could, therefore, be one mechanism by which skeletal muscle perfusion is impaired with advancing age. The current study aimed to evaluate the effect of inhibiting the main enzyme involved in cGMP degradation, phosphodiesterase 5 (PDE5), on blood flow and O2 delivery in contracting skeletal muscle of young and older humans. A group of young (23 ± 1 years) and a group of older (72 ± 2 years) male human subjects performed submaximal knee-extensor exercise in a control setting and following intake of the highly selective PDE5 inhibitor sildenafil. Sildenafil increased leg O2 delivery (6–9%) and leg O2 uptake (10–12%) at all three exercise intensities in older but not young subjects. The increase in leg O2 delivery with sildenafil in the older subjects correlated with the increase in leg O2 uptake (r2 = 0.843). These findings suggest an insufficient O2 delivery to the contracting skeletal muscle of aged individuals and that reduced cGMP availability is a novel mechanism underlying impaired skeletal muscle perfusion with advancing age. PMID:26272735

High doses of anti-inflammatory drugs compromise muscle strength and hypertrophic adaptations to resistance training in young adults.

PubMed

Lilja, M; Mandić, M; Apró, W; Melin, M; Olsson, K; Rosenborg, S; Gustafsson, T; Lundberg, T R

2018-02-01

This study tested the hypothesis that high doses of anti-inflammatory drugs would attenuate the adaptive response to resistance training compared with low doses. Healthy men and women (aged 18-35 years) were randomly assigned to daily consumption of ibuprofen (IBU; 1200 mg; n = 15) or acetylsalicylic acid (ASA; 75 mg; n = 16) for 8 weeks. During this period, subjects completed supervised knee-extensor resistance training where one leg was subjected to training with maximal volitional effort in each repetition using a flywheel ergometer (FW), while the other leg performed conventional (work-matched across groups) weight-stack training (WS). Before and after training, muscle volume (MRI) and strength were assessed, and muscle biopsies were analysed for gene and protein expression of muscle growth regulators. The increase in m. quadriceps volume was similar between FW and WS, yet was (averaged across legs) greater in ASA (7.5%) compared with IBU (3.7%, group difference 34 cm 3 ; P = 0.029). In the WS leg, muscle strength improved similarly (11-20%) across groups. In the FW leg, increases (10-23%) in muscle strength were evident in both groups yet they were generally greater (interaction effects P < 0.05) for ASA compared with IBU. While our molecular analysis revealed several training effects, the only group interaction (P < 0.0001) arose from a downregulated mRNA expression of IL-6 in IBU. Maximal over-the-counter doses of ibuprofen attenuate strength and muscle hypertrophic adaptations to 8 weeks of resistance training in young adults. Thus, young individuals using resistance training to maximize muscle growth or strength should avoid excessive intake of anti-inflammatory drugs. © 2017 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

A Powered Lower Limb Orthosis for Providing Legged Mobility in Paraplegic Individuals.

PubMed

Quintero, Hugo A; Farris, Ryan J; Hartigan, Clare; Clesson, Ismari; Goldfarb, Michael

2011-01-01

This paper presents preliminary results on the development of a powered lower limb orthosis intended to provide legged mobility (with the use of a stability aid, such as forearm crutches) to paraplegic individuals. The orthosis contains electric motors at both hip and both knee joints, which in conjunction with ankle-foot orthoses, provides appropriate joint kinematics for legged locomotion. The paper describes the orthosis and the nature of the controller that enables the SCI patient to command the device, and presents data from preliminary trials that indicate the efficacy of the orthosis and controller in providing legged mobility.

Design of a Quasi-Passive Parallel Leg Exoskeleton to Augment Load Carrying for Walking

DTIC Science & Technology

2005-08-01

cycle,’ which is time normalized. The following figure is a pictorial illustration of the gait cycle. The gait cycle begins with the heel strike ...Positive Power – Stabilization during heel strike . (H2) Negative Power – Body pendulums over the leg and stretches the quadriceps. (H3) Positive Power...Explanations: (K1) Negative Power – Knee braking/bending after heel strike . (K2) Positive Power – Knee straightening. (K3) Negligible Power

Are Changes in Leg Power Responsible for Clinically Meaningful Improvements in Mobility Among Older Adults?

PubMed Central

Bean, Jonathan F.; Kiely, Dan K.; LaRose, Sharon; Goldstein, Richard; Frontera, Walter R.; Leveille, Suzanne G.

2010-01-01

Objectives Mobility as measured by the Short Physical Performance Battery (SPPB) or habitual Gait Speed (GS) is predictive of mortality and disability among older adults. Clinically meaningful changes of these measures have been identified. Among physiologic attributes commonly targeted in rehabilitation, we sought to identify those attributes in which changes led to clinically meaningful differences (CMD) in the mobility outcomes. Participants Community-dwelling, mobility-limited older adults (n=116) participating in a 16-week randomized controlled trial (RCT) of two modes of exercise Setting Outpatient rehabilitation centers Design Secondary analysis of data collected for a RCT of exercise using binary outcomes defined by recording a large CMD (SPPB=1 unit; GS=.1m/s). Iterative models were performed to evaluate possible confounding between physiologic variables and relevant covariates. Measures Physiologic measures included leg power, leg strength, balance as measured by the Performance Oriented Mobility Assessment (POMA), rate pressure product (RPP) at the maximal stage of an exercise tolerance test. Outcomes included GS and SPPB. Leg power and leg strength were measured using computerized pneumatic strength training equipment and recorded in Watts and Newtons respectively. Results Participants were 68% female, had a mean age of 75.2 years, with a mean of 5.5 chronic conditions and a baseline mean SPPB score of 8.7. After controlling for age, site, group assignment, and baseline outcome values, leg power was the only attribute in which changes were significantly associated with a large CMD in SPPB (OR 1.48, 95% CI 1.09, 2.02) and GS (OR1.31, 95% CI 1.01, 1.70). Conclusion Improvements in leg power, independent of strength, appear to make an important contribution towards clinically meaningful improvements in both SPPB and GS. PMID:21143443

Normalized knee-extension strength or leg-press power after fast-track total knee arthroplasty: which measure is most closely associated with performance-based and self-reported function?

PubMed

Aalund, Peter K; Larsen, Kristian; Hansen, Torben B; Bandholm, Thomas

2013-02-01

To investigate which of the 2 muscle-impairment measures for the operated leg, normalized knee extension strength or leg press power, was most closely associated with performance-based and self-reported measures of function shortly after total knee arthroplasty (TKA). Cross-sectional, exploratory study. Laboratory at a regional hospital. Individuals (N=39) with an average age ± SD of 65.5±10.3 years, who all had unilateral TKA 28 days prior. None. The patients performed maximal isometric knee extensions and dynamic leg presses to determine their body-mass normalized knee extension strength and leg press power, respectively. The 10-meter fast speed walking- and 30-second chair stand tests were used to determine performance-based function, while the Western Ontario and McMaster Universities Osteoarthritis Index and Oxford Knee Scores were used to determine self-reported function. Normalized leg press power was more closely associated with both performance-based (r=.82, P<.001) and self-reported (r=.48, P=.002) measures of function compared with normalized knee extension strength (r=.51, P=.001 and r=.39, P=.015, respectively). Normalized leg press power was more closely associated with both performance-based and self-reported function early after TKA than normalized knee extension strength. It may be explained by the fact that performance-based measures of function are typically closed kinetic chain tasks, such as walking or rising from a chair, and self-reported measures of function typically include questions that address perceived difficulty with performing these same tasks. Copyright © 2013 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Are changes in leg power responsible for clinically meaningful improvements in mobility in older adults?

PubMed

Bean, Jonathan F; Kiely, Dan K; LaRose, Sharon; Goldstein, Richard; Frontera, Walter R; Leveille, Suzanne G

2010-12-01

From among physiological attributes commonly targeted in rehabilitation, to identify those in which changes led to clinically meaningful differences (CMDs) in mobility outcomes. Secondary analysis of data collected for a randomized controlled trial of exercise using binary outcomes defined by recording a large CMD (Short Physical Performance Battery (SPPB)=1 unit; gait speed (GS)=0.1 m/s). Iterative models were performed to evaluate possible confounding between physiological variables and relevant covariates. Outpatient rehabilitation centers. Community-dwelling mobility-limited older adults (n=116) participating in a 16-week randomized controlled trial of two modes of exercise. Physiological measures included leg power, leg strength, balance as measured according to the Performance-Oriented Mobility Assessment (POMA), and rate pressure product at the maximal stage of an exercise tolerance test. Outcomes included GS and SPPB. Leg power and leg strength were measured using computerized pneumatic strength training equipment and recorded in Watts and Newtons, respectively. Participants were 68% female, had a mean age of 75.2, a mean of 5.5 chronic conditions, and a baseline mean SPPB score of 8.7. After controlling for age, site, group assignment, and baseline outcome values, leg power was the only attribute in which changes were significantly associated with a large CMD in SPPB (odds ratio (OR)=1.48, 95% confidence interval (CI)=1.09-2.02) and GS (OR=1.31, 95% CI=1.01-1.70). Improvements in leg power, independent of strength, appear to make an important contribution to clinically meaningful improvements in SPPB and GS. © 2010, Copyright the Authors. Journal compilation © 2010, The American Geriatrics Society.

Relation between Peak Power Output in Sprint Cycling and Maximum Voluntary Isometric Torque Production.

PubMed

Kordi, Mehdi; Goodall, Stuart; Barratt, Paul; Rowley, Nicola; Leeder, Jonathan; Howatson, Glyn

2017-08-01

From a cycling paradigm, little has been done to understand the relationships between maximal isometric strength of different single joint lower body muscle groups and their relation with, and ability to predict PPO and how they compare to an isometric cycling specific task. The aim of this study was to establish relationships between maximal voluntary torque production from isometric single-joint and cycling specific tasks and assess their ability to predict PPO. Twenty male trained cyclists participated in this study. Peak torque was measured by performing maximum voluntary contractions (MVC) of knee extensors, knee flexors, dorsi flexors and hip extensors whilst instrumented cranks measured isometric peak torque from MVC when participants were in their cycling specific position (ISOCYC). A stepwise regression showed that peak torque of the knee extensors was the only significant predictor of PPO when using SJD and accounted for 47% of the variance. However, when compared to ISOCYC, the only significant predictor of PPO was ISOCYC, which accounted for 77% of the variance. This suggests that peak torque of the knee extensors was the best single-joint predictor of PPO in sprint cycling. Furthermore, a stronger prediction can be made from a task specific isometric task. Copyright © 2017 Elsevier Ltd. All rights reserved.

Hip and knee extensor moments predict vertical jump height in adolescent girls.

PubMed

Ford, Kevin R; Myer, Gregory D; Brent, Jensen L; Hewett, Timothy E

2009-07-01

Biomechanical factors, such as hip and knee extensor moments, related to drop jump (DJ) performance have not been investigated in adolescent girls. The purpose of this study was to determine the key independent biomechanical variables that predict overall vertical jump performance in adolescent girls. Sixteen high school adolescent girls from club-sponsored and high school-sponsored volleyball teams performed DJ at 3 different drop heights (15, 30, and 45 cm). A motion analysis system consisting of 10 digital cameras and a force platform was used to calculate vertical jump height, joint angles, and joint moments during the tasks. A multiple linear regression was used to determine the biomechanical parameters that were best predictive of vertical jump height at each box drop distance. The 2 predictor variables in all 3 models were knee and hip extensor moments. The models predicted 82.9, 81.9, and 88% of the vertical jump height variance in the 15, 30, and 45 cm trials, respectively. The results of the investigation indicate that knee and hip joint moments are the main contributors to vertical jump height during the DJ in adolescent girls. Strength and conditioning specialists attempting to improve vertical jump performance should target power and strength training to the hip and knee extensors in their athletes.

Hip Abductor Strengthening Improves Physical Function Following Total Knee Replacement: One-Year Follow-Up of a Randomized Pilot Study.

PubMed

Harikesavan, Karvannan; Chakravarty, Raj D; Maiya, Arun G; Hegde, Sanjay P; Y Shivanna, Shivakumar

2017-01-01

Total knee replacement (TKR) is the commonest surgical procedure for patients with severe pain and impaired physical function following end stage knee osteoarthritis. The hip abductors are well renowned in stabilization of the trunk and hip during walking, maintaining the lower limb position, and transferring the forces from the lower limbs to the pelvis. To assess the efficacy of hip abductor strengthening exercise on functional outcome using performance based outcome measures following total knee replacement. An observer blinded randomized pilot trial design was conducted at Manipal hospital, Bangalore, India. Participants designated for elective TKR were randomized to experimental group hip abductor strengthening along with standard rehabilitation (n=10) or control group standard rehabilitation alone (n=10). Participants followed for one year to assess physical function using performance based outcomes, such as timed up and go test, single leg stance test, six minute walk test, knee extensor strength and hip abductor strength. Eighteen participants with a mean age of 63.1 ± 5.5 years (8 Males and 10 Females) completed the study. Improvement in hip abduction strength, single leg stand test was superior in hip abductor strengthening group at 3 months and 1 year when compared to standard rehabilitation alone. Hip abductor strengthening showed superior improvements in single leg stance test and six minute walk test. Hip abductor strengthening exercises has the potential to improve physical function following total knee replacement.

Hip Abductor Strengthening Improves Physical Function Following Total Knee Replacement: One-Year Follow-Up of a Randomized Pilot Study

PubMed Central

Harikesavan, Karvannan; Chakravarty, Raj D.; Maiya, Arun G; Hegde, Sanjay P.; Y. Shivanna, Shivakumar

2017-01-01

Background: Total knee replacement (TKR) is the commonest surgical procedure for patients with severe pain and impaired physical function following end stage knee osteoarthritis. The hip abductors are well renowned in stabilization of the trunk and hip during walking, maintaining the lower limb position, and transferring the forces from the lower limbs to the pelvis. Objective: To assess the efficacy of hip abductor strengthening exercise on functional outcome using performance based outcome measures following total knee replacement. Methods: An observer blinded randomized pilot trial design was conducted at Manipal hospital, Bangalore, India. Participants designated for elective TKR were randomized to experimental group hip abductor strengthening along with standard rehabilitation (n=10) or control group standard rehabilitation alone (n=10). Participants followed for one year to assess physical function using performance based outcomes, such as timed up and go test, single leg stance test, six minute walk test, knee extensor strength and hip abductor strength. Result: Eighteen participants with a mean age of 63.1 ± 5.5 years (8 Males and 10 Females) completed the study. Improvement in hip abduction strength, single leg stand test was superior in hip abductor strengthening group at 3 months and 1 year when compared to standard rehabilitation alone. Conclusion: Hip abductor strengthening showed superior improvements in single leg stance test and six minute walk test. Hip abductor strengthening exercises has the potential to improve physical function following total knee replacement. PMID:28567148

Active and Inactive Leg Hemodynamics during Sequential Single-Leg Interval Cycling.

PubMed

Gordon, Nicole; Abbiss, Chris R; Ihsan, Mohammed; Maiorana, Andrew J; Peiffer, Jeremiah J

2018-06-01

Leg order during sequential single-leg cycling (i.e., exercising both legs independently within a single session) may affect local muscular responses potentially influencing adaptations. This study examined the cardiovascular and skeletal muscle hemodynamic responses during double-leg and sequential single-leg cycling. Ten young healthy adults (28 ± 6 yr) completed six 1-min double-leg intervals interspersed with 1 min of passive recovery and, on a separate occasion, 12 (six with one leg followed by six with the other leg) 1-min single-leg intervals interspersed with 1 min of passive recovery. Oxygen consumption, heart rate, blood pressure, muscle oxygenation, muscle blood volume, and power output were measured throughout each session. Oxygen consumption, heart rate, and power output were not different between sets of single-leg intervals, but the average of both sets was lower than the double-leg intervals. Mean arterial pressure was higher during double-leg compared with sequential single-leg intervals (115 ± 9 vs 104 ± 9 mm Hg, P < 0.05) and higher during the initial compared with second set of single-leg intervals (108 ± 10 vs 101 ± 10 mm Hg, P < 0.05). The increase in muscle blood volume from baseline was similar between the active single leg and the double leg (267 ± 150 vs 214 ± 169 μM·cm, P = 0.26). The pattern of change in muscle blood volume from the initial to second set of intervals was significantly different (P < 0.05) when the leg was active in the initial (-52.3% ± 111.6%) compared with second set (65.1% ± 152.9%). These data indicate that the order in which each leg performs sequential single-leg cycling influences the local hemodynamic responses, with the inactive muscle influencing the stimulus experienced by the contralateral leg.

Spontaneous motor rhythms of the back and legs in a patient with a complete spinal cord transection.

PubMed

Nadeau, Sylvie; Jacquemin, Géraldine; Fournier, Christine; Lamarre, Yves; Rossignol, Serge

2010-05-01

Spontaneous activity originating from the spinal cord has been sporadically reported in humans. Investigation of such rhythmic activity of the trunk and legs in a 49-year-old male patient who had a complete severance of the spinal cord at the fifth thoracic vertebra. A multichannel electromyography (EMG) study was performed together with kinematics measurements obtained from an Optotrak system. Episodes of rhythmic trunk and lower limb movements started 6 to 7 years after the spinal lesion, recurred at 2 to 3 month intervals, and continued uninterrupted for 2 to 3 days despite continuous delivery of intrathecal baclofen. Several muscles discharged more or less synchronously on both sides but others clearly alternated, for instance, between hip flexors and knee or ankle extensors. Sensory stimuli (hip repositioning or skin pinch) altered significantly the baseline rhythm of about 1 Hz. The patient had both hips injected with corticosteroids and was free of these episodic rhythmic crises for more than 6 months. The rhythmic activity observed in the patient appeared related to the activation of a spinal pattern generator akin to what has been described in most animal species after complete spinal lesions.

Muscle performance following an acute bout of plyometric training combined with low or high intensity weight exercise.

PubMed

Beneka, Anastasia G; Malliou, Paraskevi K; Missailidou, Victoria; Chatzinikolaou, Athanasios; Fatouros, Ioannis; Gourgoulis, Vassilios; Georgiadis, Elias

2013-01-01

To determine the time course of performance responses after an acute bout of plyometric exercise combined with high and low intensity weight training, a 3-group (including a control group), repeated-measures design was employed. Changes in performance were monitored through jumping ability by measuring countermovement and squat jumping, and strength performance assessment through isometric and isokinetic testing of knee extensors (at two different velocities). Participants in both experimental groups performed a plyometric protocol consisting of 50 jumps over 50 cm hurdles and 50 drop jumps from a 50 cm plyometric box. Additionally, each group performed two basic weight exercises consisting of leg presses and leg extensions at 90-95% of maximum muscle strength for the high intensity group and 60% of maximum muscle strength for the low intensity group. The results of the study suggest that an acute bout of intense plyometric exercise combined with weight exercise induces time-dependent changes in performance, which are also dependent on the nature of exercise protocol and testing procedures. In conclusion, acute plyometric exercise with weight exercise may induce a substantial decline in jumping performance for as long as 72 hours but not in other forms of muscle strength.

Using leg muscles as shock absorbers: theoretical predictions and experimental results of drop landing performance.

PubMed

Minetti, A E; Ardigò, L P; Susta, D; Cotelli, F

1998-12-01

The use of muscles as power dissipators is investigated in this study, both from the modellistic and the experimental points of view. Theoretical predictions of the drop landing manoeuvre for a range of initial conditions have been obtained by accounting for the mechanical characteristics of knee extensor muscles, the limb geometry and assuming maximum neural activation. Resulting dynamics have been represented in the phase plane (vertical displacement versus speed) to better classify the damping performance. Predictions of safe landing in sedentary subjects were associated to dropping from a maximum (feet) height of 1.6-2.0 m (about 11 m on the moon). Athletes can extend up to 2.6-3.0 m, while for obese males (m = 100 kg, standard stature) the limit should reduce to 0.9-1.3 m. These results have been calculated by including in the model the estimated stiffness of the 'global elastic elements' acting below the squat position. Experimental landings from a height of 0.4, 0.7, 1.1 m (sedentary males (SM) and male (AM) and female (AF) athletes from the alpine ski national team) showed dynamics similar to the model predictions. While the peak power (for a drop height of about 0.7 m) was similar in SM and AF (AM shows a +40% increase, about 33 W/kg), AF stopped the downward movement after a time interval (0.219 +/- 0.030 s) from touch-down 20% significantly shorter than SM. Landing strategy and the effect of anatomical constraints are discussed in the paper.

Improved walking ability with wearable robot-assisted training in patients suffering chronic stroke.

PubMed

Li, Lifang; Ding, Li; Chen, Na; Mao, Yurong; Huang, Dongfeng; Li, Le

2015-01-01

Wearable robotic devices provide safe and intensive rehabilitation, enabling repeated motions for motor function recovery in stroke patients. The aim of this small case series was to demonstrate the training effects of a three-week robotic leg orthosis, and to investigate possible mechanisms of the sensory-motor alterations and improvements by using gait analysis and EMG. Three survivors of chronic strokes participated in robot-assisted gait therapy for three weeks. EMG signals from the rectus femoris (RF), tibialis anterior (TA), biceps femoris (BF), and medial gastrocnemius (MG), as well as kinetics and kinematics data of the lower limb, were recorded before and after the training. The normalized root mean squared (RMS) values of the muscles, the joint moments, joint angles, and the results of two clinical scales (Berg Balance scale, BBS, and the lower extremity subscale of Fugl-Meyer assessment, LE-FMA) were used for analysis. All participants experienced improved balance and functional performances and increased BBS and LE-FMA scores. The EMG results showed there was an increase of the normalized RMS values of the MG and BF on the affected side. Additionally, EMG activities of the agonist and antagonist pair (i.e. RF and BF) appeared to return to similar levels after training. The peak moment of hip flexor, knee extensor, and plantar flexor, which all contributed to push-off power, were found to have increased after training. In summary, the three-week training period using the wearable RLO improved the three participants' gait performance by regaining push-off power and improved muscle activation and walking speed.

Robot and robot system

NASA Technical Reports Server (NTRS)

Behar, Alberto E. (Inventor); Marzwell, Neville I. (Inventor); Wall, Jonathan N. (Inventor); Poole, Michael D. (Inventor)

2011-01-01

A robot and robot system that are capable of functioning in a zero-gravity environment are provided. The robot can include a body having a longitudinal axis and having a control unit and a power source. The robot can include a first leg pair including a first leg and a second leg. Each leg of the first leg pair can be pivotally attached to the body and constrained to pivot in a first leg pair plane that is substantially perpendicular to the longitudinal axis of the body.

Leg exoskeleton reduces the metabolic cost of human hopping.

PubMed

Grabowski, Alena M; Herr, Hugh M

2009-09-01

During bouncing gaits such as hopping and running, leg muscles generate force to enable elastic energy storage and return primarily from tendons and, thus, demand metabolic energy. In an effort to reduce metabolic demand, we designed two elastic leg exoskeletons that act in parallel with the wearer's legs; one exoskeleton consisted of a multiple leaf (MLE) and the other of a single leaf (SLE) set of fiberglass springs. We hypothesized that hoppers, hopping on both legs, would adjust their leg stiffness while wearing an exoskeleton so that the combination of the hopper and exoskeleton would behave as a linear spring-mass system with the same total stiffness as during normal hopping. We also hypothesized that decreased leg force generation while wearing an exoskeleton would reduce the metabolic power required for hopping. Nine subjects hopped in place at 2.0, 2.2, 2.4, and 2.6 Hz with and without an exoskeleton while we measured ground reaction forces, exoskeletal compression, and metabolic rates. While wearing an exoskeleton, hoppers adjusted their leg stiffness to maintain linear spring-mass mechanics and a total stiffness similar to normal hopping. Without accounting for the added weight of each exoskeleton, wearing the MLE reduced net metabolic power by an average of 6% and wearing the SLE reduced net metabolic power by an average of 24% compared with hopping normally at frequencies between 2.0 and 2.6 Hz. Thus, when hoppers used external parallel springs, they likely decreased the mechanical work performed by the legs and substantially reduced metabolic demand compared with hopping without wearing an exoskeleton.

Lower extremity joint kinetics and energetics during backward running.

PubMed

DeVita, P; Stribling, J

1991-05-01

The purpose of this study was to measure lower extremity joint moments of force and joint muscle powers used to perform backward running. Ten trials of high speed (100 Hz) sagittal plane film records and ground reaction force data (1000 Hz) describing backward running were obtained from each of five male runners. Fifteen trials of forward running data were obtained from one of these subjects. Inverse dynamics were performed on these data to obtain the joint moments and powers, which were normalized to body mass to make between-subject comparisons. Backward running hip moment and power patterns were similar in magnitude and opposite in direction to forward running curves and produced more positive work in stance. Functional roles of knee and ankle muscles were interchanged between backward and forward running. Knee extensors were the primary source of propulsion in backward running owing to greater moment and power output (peak moment = 3.60 N.m.kg-1; peak power = 12.40 W.kg-1) compared with the ankle (peak moment = 1.92 N.m.kg-1; peak power = 7.05 W.kg-1). The ankle plantarflexors were the primary shock absorbers, producing the greatest negative power (peak = -6.77 W.kg-1) during early stance. Forward running had greater ankle moment and power output for propulsion and greater knee negative power for impact attenuation. The large knee moment in backward running supported previous findings indicating that backward running training leads to increased knee extensor torque capabilities.

Neuromuscular fatigue following constant versus variable-intensity endurance cycling in triathletes.

PubMed

Lepers, R; Theurel, J; Hausswirth, C; Bernard, T

2008-07-01

The aim of this study was to determine whether or not variable power cycling produced greater neuromuscular fatigue of knee extensor muscles than constant power cycling at the same mean power output. Eight male triathletes (age: 33+/-5 years, mass: 74+/-4 kg, VO2max: 62+/-5 mL kg(-1) min(-1), maximal aerobic power: 392+/-17 W) performed two 30 min trials on a cycle ergometer in a random order. Cycling exercise was performed either at a constant power output (CP) corresponding to 75% of the maximal aerobic power (MAP) or a variable power output (VP) with alternating +/-15%, +/-5%, and +/-10% of 75% MAP approximately every 5 min. Maximal voluntary contraction (MVC) torque, maximal voluntary activation level and excitation-contraction coupling process of knee extensor muscles were evaluated before and immediately after the exercise using the technique of electrically evoked contractions (single and paired stimulations). Oxygen uptake, ventilation and heart rate were also measured at regular intervals during the exercise. Averaged metabolic variables were not significantly different between the two conditions. Similarly, reductions in MVC torque (approximately -11%, P<0.05) after cycling were not different (P>0.05) between CP and VP trials. The magnitude of central and peripheral fatigue was also similar at the end of the two cycling exercises. It is concluded that, following 30 min of endurance cycling, semi-elite triathletes experienced no additional neuromuscular fatigue by varying power (from +/-5% to 15%) compared with a protocol that involved a constant power.

A Powered Lower Limb Orthosis for Providing Legged Mobility in Paraplegic Individuals

PubMed Central

Quintero, Hugo A.; Farris, Ryan J.; Hartigan, Clare; Clesson, Ismari; Goldfarb, Michael

2012-01-01

This paper presents preliminary results on the development of a powered lower limb orthosis intended to provide legged mobility (with the use of a stability aid, such as forearm crutches) to paraplegic individuals. The orthosis contains electric motors at both hip and both knee joints, which in conjunction with ankle-foot orthoses, provides appropriate joint kinematics for legged locomotion. The paper describes the orthosis and the nature of the controller that enables the SCI patient to command the device, and presents data from preliminary trials that indicate the efficacy of the orthosis and controller in providing legged mobility. PMID:22707874

The influence of ACE ID and ACTN3 R577X polymorphisms on lower-extremity function in older women in response to high-speed power training.

PubMed

Pereira, Ana; Costa, Aldo M; Leitão, José C; Monteiro, António M; Izquierdo, Mikel; Silva, António J; Bastos, Estela; Marques, Mário C

2013-12-06

We studied the influence of the ACE I/D and ACTN3 R577X polymorphisms (single or combined) on lower-extremity function in older women in response to high-speed power training. One hundred and thirty-nine healthy older Caucasian women participated in this study (age: 65.5 ± 8.2 years, body mass: 67.0 ± 10.0 kg and height: 1.57 ± 0.06 m). Walking speed (S10) performance and functional capacity assessed by the "get-up and go" (GUG) mobility test were measured at baseline (T1) and after a consecutive 12-week period of high-speed power training (40-75% of one repetition maximum in arm and leg extensor exercises; 3 sets 4-12 reps, and two power exercises for upper and lower extremity). Genomic DNA was extracted from blood samples, and genotyping analyses were performed by PCR methods. Genotype distributions between groups were compared by Chi-Square test and the gains in physical performance were analyzed by two-way, repeated-measures ANOVA. There were no significant differences between genotype groups in men or women for adjusted baseline phenotypes (P > 0.05). ACE I/D and ACTN3 polymorphisms showed a significant interaction genotype-training only in S10 (P = 0.012 and P = 0.044, respectively) and not in the GUG test (P = 0.311 and P = 0.477, respectively). Analyses of the combined effects between genotypes showed no other significant differences in all phenotypes (P < 0.05) at baseline. However, in response to high-speed power training, a significant interaction on walking speed (P = 0.048) was observed between the "power" (ACTN3 RR + RX & ACE DD) versus "non-power" muscularity-oriented genotypes (ACTN3 XX & ACE II + ID)]. Thus, ACE I/D and ACTN3 R577X polymorphisms are likely candidates in the modulation of exercise-related gait speed phenotype in older women but not a significant influence in mobility traits.

Effects of a powered ankle-foot prosthesis on kinetic loading of the unaffected leg during level-ground walking

PubMed Central

2013-01-01

Background People with a lower-extremity amputation that use conventional passive-elastic ankle-foot prostheses encounter a series of stress-related challenges during walking such as greater forces on their unaffected leg, and may thus be predisposed to secondary musculoskeletal injuries such as chronic joint disorders. Specifically, people with a unilateral transtibial amputation have an increased susceptibility to knee osteoarthritis, especially in their unaffected leg. Previous studies have hypothesized that the development of this disorder is linked to the abnormally high peak knee external adduction moments encountered during walking. An ankle-foot prosthesis that supplies biomimetic power could potentially mitigate the forces and knee adduction moments applied to the unaffected leg of a person with a transtibial amputation, which could, in turn, reduce the risk of knee osteoarthritis. We hypothesized that compared to using a passive-elastic prosthesis, people with a transtibial amputation using a powered ankle-foot prosthesis would have lower peak resultant ground reaction forces, peak external knee adduction moments, and corresponding loading rates applied to their unaffected leg during walking over a wide range of speeds. Methods We analyzed ground reaction forces and knee joint kinetics of the unaffected leg of seven participants with a unilateral transtibial amputation and seven age-, height- and weight-matched non-amputees during level-ground walking at 0.75, 1.00, 1.25, 1.50, and 1.75 m/s. Subjects with an amputation walked while using their own passive-elastic prosthesis and a powered ankle-foot prosthesis capable of providing net positive mechanical work and powered ankle plantar flexion during late stance. Results Use of the powered prosthesis significantly decreased unaffected leg peak resultant forces by 2-11% at 0.75-1.50 m/s, and first peak knee external adduction moments by 21 and 12% at 1.50 and 1.75 m/s, respectively. Loading rates were not significantly different between prosthetic feet. Conclusions Use of a biomimetic powered ankle-foot prosthesis decreased peak resultant force at slow and moderate speeds and knee external adduction moment at moderate and fast speeds on the unaffected leg of people with a transtibial amputation during level-ground walking. Thus, use of an ankle-foot prosthesis that provides net positive mechanical work could reduce the risk of comorbidities such as knee osteoarthritis. PMID:23758860

Endothelial mechanotransduction proteins and vascular function are altered by dietary sucrose supplementation in healthy young male subjects.

PubMed

Gliemann, Lasse; Rytter, Nicolai; Lindskrog, Mads; Slingsby, Martina H Lundberg; Åkerström, Thorbjörn; Sylow, Lykke; Richter, Erik A; Hellsten, Ylva

2017-08-15

Mechanotransduction in endothelial cells is a central mechanism in the regulation of vascular tone and vascular remodelling Mechanotransduction and vascular function may be affected by high sugar levels in plasma because of a resulting increase in oxidative stress and increased levels of advanced glycation end-products (AGE). In healthy young subjects, 2 weeks of daily supplementation with 3 × 75 g of sucrose was found to reduce blood flow in response to passive lower leg movement and in response to 12 W of knee extensor exercise. This vascular impairment was paralleled by up-regulation of platelet endothelial cell adhesion molecule (PECAM)-1, endothelial nitric oxide synthase, NADPH oxidase and Rho family GTPase Rac1 protein expression, an increased basal phosphorylation status of vascular endothelial growth factor receptor 2 and a reduced phosphorylation status of PECAM-1. There were no measurable changes in AGE levels. The findings of the present study demonstrate that daily high sucrose intake markedly affects mechanotransduction proteins and has a detrimental effect on vascular function. Endothelial mechanotransduction is important for vascular function but alterations and activation of vascular mechanosensory proteins have not been investigated in humans. In endothelial cell culture, simple sugars effectively impair mechanosensor proteins. To study mechanosensor- and vascular function in humans, 12 young healthy male subjects supplemented their diet with 3 × 75 g sucrose day -1 for 14 days in a randomized cross-over design. Before and after the intervention period, the hyperaemic response to passive lower leg movement and active knee extensor exercise was determined by ultrasound doppler. A muscle biopsy was obtained from the thigh muscle before and after acute passive leg movement to allow assessment of protein amounts and the phosphorylation status of mechanosensory proteins and NADPH oxidase. The sucrose intervention led to a reduced flow response to passive movement (by 17 ± 2%) and to 12 W of active exercise (by 9 ± 1%), indicating impaired vascular function. A reduced flow response to passive and active exercise was paralleled by a significant up-regulation of platelet endothelial cell adhesion molecule (PECAM-1), endothelial nitric oxide synthase, NADPH oxidase and the Rho family GTPase Rac1 protein expression in the muscle tissue, as well as an increased basal phosphorylation status of vascular endothelial growth factor receptor 2 and a reduced phosphorylation status of PECAM-1. The phosphorylation status was not acutely altered with passive leg movement. These findings indicate that a regular intake of high levels of sucrose can impair vascular mechanotransduction and increase the oxidative stress potential, and suggest that dietary excessive sugar intake may contribute to the development of vascular disease. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

Quantitative Evaluation of Muscle Function, Gait, and Postural Control in People Experiencing Critical Illness After Discharge From the Intensive Care Unit.

PubMed

Kiriella, Jeevaka B; Araujo, Tamara; Vergara, Martin; Lopez-Hernandez, Laura; Cameron, Jill I; Herridge, Margaret; Gage, William H; Mathur, Sunita

2018-01-01

The path to recovery of muscle strength and mobility following discharge from the intensive care unit (ICU) has not been well described. The study objective was to quantify muscle function, gait, and postural control at 3 and 6 months after discharge in people who were recovering from critical illness and who were ventilated for 7 days or more. This was a nested longitudinal study with continuous inclusion of individuals over a 2-year period and with age- and sex-matched controls. Twenty-four people were tested at 3 months after ICU discharge; 16 of them (67%) were reevaluated at 6 months (post-ICU group). Healthy controls (n = 12) were tested at a single time point. Muscle function of the knee extensors (KEs), plantar flexors (PFs), and dorsiflexors (DFs) was assessed on a dynamometer. Gait was measured using an electronic walkway, and postural control was measured with 2 portable force plates. Muscle weakness was observed across all muscle groups at 3 months, with the greatest strength reductions in the ankle PFs (45%) and DFs (30%). Muscle power was reduced in the PFs and DFs but was not reduced in the KEs. Gait in the post-ICU group was characterized by a narrower step, longer stride, and longer double-support time than in the controls. Improvements were found in KE strength and in stride time and double-support time during gait at 6 months. Leg muscle strength and power had moderate associations with gait velocity, step width, and stride length (r = .44-.65). The small heterogeneous sample of people with a high level of function was a limitation of this study. Muscle strength and power were impaired at 6 months after ICU discharge and were associated with gait parameters. Future studies are needed to examine the role of muscle strength and power training in post-ICU rehabilitation programs to improve mobility. © 2017 American Physical Therapy Association

Physical activity as intervention for age-related loss of muscle mass and function: protocol for a randomised controlled trial (the LISA study)

PubMed Central

Eriksen, Christian Skou; Garde, Ellen; Reislev, Nina Linde; Wimmelmann, Cathrine Lawaetz; Bieler, Theresa; Ziegler, Andreas Kraag; Gylling, Anne Theil; Dideriksen, Kasper Juel; Siebner, Hartwig Roman; Mortensen, Erik Lykke; Kjaer, Michael

2016-01-01

Introduction Physical and cognitive function decline with age, accelerating during the 6th decade. Loss of muscle power (force×velocity product) is a dominant physical determinant for loss of functional ability, especially if the lower extremities are affected. Muscle strength training is known to maintain or even improve muscle power as well as physical function in older adults, but the optimal type of training for beneficial long-term training effects over several years is unknown. Moreover, the impact of muscle strength training on cognitive function and brain structure remains speculative. The primary aim of this randomised controlled trial is to compare the efficacy of two different 1 year strength training regimens on immediate and long-lasting improvements in muscle power in retirement-age individuals. Secondary aims are to evaluate the effect on muscle strength, muscle mass, physical and cognitive function, mental well-being, health-related quality of life and brain morphology. Methods and analysis The study includes 450 home-dwelling men and women (62–70 years). Participants are randomly allocated to (1) 1 year of supervised, centre-based heavy resistance training, (2) home-based moderate intensity resistance training or (3) habitual physical activity (control). Changes in primary (leg extensor power) and secondary outcomes are analysed according to the intention to treat principle and per protocol at 1, 2, 4, 7 and 10 years. Ethics and dissemination The study is expected to generate new insights into training-induced promotion of functional ability and independency after retirement and will help to formulate national recommendations regarding physical activity schemes for the growing population of older individuals in western societies. Results will be published in scientific peer-reviewed journals, in PhD theses and at public meetings. The study is approved by the Regional Ethical Committee (Capital Region, Copenhagen, Denmark, number H-3-2014-017). Trial registration number NCT02123641. PMID:27913559

Core stability training on lower limb balance strength.

PubMed

Dello Iacono, Antonio; Padulo, Johnny; Ayalon, Moshe

2016-01-01

This study aimed to assess the effects of core stability training on lower limbs' muscular asymmetries and imbalances in team sport. Twenty footballers were divided into two groups, either core stability or control group. Before each daily practice, core stability group (n = 10) performed a core stability training programme, while control group (n = 10) did a standard warm-up. The effects of the core stability training programme were assessed by performing isokinetic tests and single-leg countermovement jumps. Significant improvement was found for knee extensors peak torque at 3.14 rad · s(-1) (14%; P < 0.05), knee flexors peak torque at 1.05 and 3.14 rad · s(-1) (19% and 22% with P < 0.01 and P < 0.01, respectively) and peak torque flexors/extensors ratios at 1.05 and 3.14 rad · s(-1) (7.7% and 8.5% with P < 0.05 and P < 0.05, respectively) only in the core stability group. The jump tests showed a significant reduction in the strength asymmetries in core stability group (-71.4%; P = 0.02) while a concurrent increase was seen in the control group (33.3%; P < 0.05). This study provides practical evidence in combining core exercises for optimal lower limbs strength balance development in young soccer players.

Association of activities of daily living with the load during step ascent motion in nursing home-residing elderly individuals.

PubMed

Masaki, Mitsuhiro; Ikezoe, Tome; Kamiya, Midori; Araki, Kojiro; Isono, Ryo; Kato, Takehiro; Kusano, Ken; Tanaka, Masayo; Sato, Syunsuke; Hirono, Tetsuya; Kita, Kiyoshi; Tsuboyama, Tadao; Ichihashi, Noriaki

2018-04-19

This study aimed to examine the association of independence in ADL with the loads during step ascent motion and other motor functions in 32 nursing home-residing elderly individuals. Independence in ADL was assessed by using the functional independence measure (FIM). The loads at the upper (i.e., pulling up) and lower (i.e., pushing up) levels during step ascent task was measured on a step ascent platform. Hip extensor, knee extensor, plantar flexor muscle, and quadriceps setting strengths; lower extremity agility using the stepping test; and hip and knee joint pain severities were measured. One-legged stance and functional reach distance for balance, and maximal walking speed, timed up-and-go (TUG) time, five-chair-stand time, and step ascent time were also measured to assess mobility. Stepwise regression analysis revealed that the load at pushing up during step ascent motion and TUG time were significant and independent determinants of FIM score. FIM score decreased with decreased the load at pushing up and increased TUG time. The study results suggest that depending on task specificity, both one step up task's push up peak load during step ascent motion and TUG, can partially explain ADL's FIM score in the nursing home-residing elderly individuals. Lower extremity muscle strength, agility, pain or balance measures did not add to the prediction.

Reduced high-frequency motor neuron firing, EMG fractionation, and gait variability in awake walking ALS mice

PubMed Central

Hadzipasic, Muhamed; Ni, Weiming; Nagy, Maria; Steenrod, Natalie; McGinley, Matthew J.; Kaushal, Adi; Thomas, Eleanor; McCormick, David A.

2016-01-01

Amyotrophic lateral sclerosis (ALS) is a lethal neurodegenerative disease prominently featuring motor neuron (MN) loss and paralysis. A recent study using whole-cell patch clamp recording of MNs in acute spinal cord slices from symptomatic adult ALS mice showed that the fastest firing MNs are preferentially lost. To measure the in vivo effects of such loss, awake symptomatic-stage ALS mice performing self-initiated walking on a wheel were studied. Both single-unit extracellular recordings within spinal cord MN pools for lower leg flexor and extensor muscles and the electromyograms (EMGs) of the corresponding muscles were recorded. In the ALS mice, we observed absent or truncated high-frequency firing of MNs at the appropriate time in the step cycle and step-to-step variability of the EMG, as well as flexor-extensor coactivation. In turn, kinematic analysis of walking showed step-to-step variability of gait. At the MN level, the higher frequencies absent from recordings from mutant mice corresponded with the upper range of frequencies observed for fast-firing MNs in earlier slice measurements. These results suggest that, in SOD1-linked ALS mice, symptoms are a product of abnormal MN firing due at least in part to loss of neurons that fire at high frequency, associated with altered EMG patterns and hindlimb kinematics during gait. PMID:27821773

Baseline Mechanical and Neuromuscular Profile of Knee Extensor and Flexor Muscles in Professional Soccer Players at the Start of the Pre-Season.

PubMed

García-García, Oscar; Serrano-Gómez, Virginia; Hernández-Mendo, Antonio; Morales-Sánchez, Verónica

2017-09-01

The aim of the study was to determine the mechanical and neuromuscular profile of knee extensor and flexor muscles in professional soccer players at the start of the pre-season, and to calculate percentages for symmetry, as well as examine differences according to the player's positional role. The vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF) and biceps femoris (BF) of 16 professional soccer players were evaluated by means of tensiomyography (TMG) on the first day of the pre-season. A paired-samples t test (p < .05) was used to compare the dominant and non-dominant lower limb. One-way ANOVA was applied, with the positional role as an independent factor. No differences were observed between the dominant and non-dominant leg. The highest degree of symmetry corresponded to the VM (92.5 ± 2.7%), and the lowest to the BF (80.7 ± 10.9%). The positional role was associated with significant differences in some of the variables for the BF, RF and VM, although only the half-relaxation time in the BF and the time to sustain force in the VM differed across all the playing positions considered. TMG was shown to be a useful way of evaluating the neuromuscular characteristics of soccer players at the start of the pre-season, and of establishing baseline values for individual players.

Contribution of knee flexor and extensor strength on sex-specific energy absorption and torsional joint stiffness during drop jumping.

PubMed

Schmitz, Randy J; Shultz, Sandra J

2010-01-01

Lower extremity injury often occurs during abrupt deceleration when attempting to change the body's direction. Although sex-specific biomechanics have been implicated in the greater risk of acute knee injury in women than in men, it is unknown if sex differences in thigh strength affect sex-specific energy absorption and torsional joint stiffness patterns. To determine sex differences in energy absorption patterns and joint stiffnesses of the lower extremity during a drop jump and to determine if these sex differences were predicted by knee extensor and flexor strength. Cross-sectional study. Laboratory environment. Recreationally active, college-aged students (41 women: age  =  22.1 ± 2.9 years, height  =  1.63 ± 0.07 m, mass  =  59.3 ± 8.0 kg; 40 men: age  =  22.4 ± 2.8 years, height  =  1.77 ± 0.1 m, mass  =  80.9 ± 14.1 kg). Participants performed knee flexor and extensor maximal voluntary isometric contractions followed by double-leg drop-jump landings. Lower extremity joint energetics (J × N(-1) × m(-1)) and torsional joint stiffnesses (Nm × N(-1) × m(-1) × degrees(-1)) were calculated for the hip, knee, and ankle during the initial landing phase. Body weight was measured in newtons and height was measured in meters. Sex comparisons were made and sex-specific regressions determined if thigh muscle strength (Nm/kg) predicted sagittal-plane landing energetics and stiffnesses. Women absorbed 69% more knee energy and had 36% less hip torsional stiffness than men. In women, greater knee extensor strength predicted greater knee energy absorption (R(2)  =  0.11, P  =  .04), and greater knee flexor strength predicted greater hip torsional stiffness (R(2)  =  0.12, P  =  .03). Sex-specific biomechanics during the deceleration phase of a drop jump revealed that women used a strategy to attempt to decrease system stiffness. Additionally, only female strength values were predictive of landing energetics and stiffnesses. These findings collectively demonstrated that the task may have been more difficult for women, resulting in a different movement strategy among those with different levels of thigh strength to safely complete the task. Future researchers should look at other predictive factors of observed sex differences.

Comparison of muscle cross-sectional areas between weight lifters and wrestlers.

PubMed

Kanehisa, H; Ikegawa, S; Fukunaga, T

1998-05-01

The purpose of this study was to investigate the difference in the magnitude of muscular development between Olympic weight lifters and wrestlers through the measurements of fat-free mass (FFM) and limb muscle cross-sectional area (CSA). Subjects were college Olympic weight lifters (N = 34, age = 20.0 +/- 1.3 years, stature = 1.67 +/- 0.07 m, body mass = 70.1 +/- 10.2 kg, X +/- SD) and wrestlers (N = 33,20.3 +/- 1.2 years, 1.69 +/- 0.06 m, 71.0 +/- 1.8 kg) who had identical range of body mass. Body density and the CSAs of reciprocal muscle groups in the forearm, upper arm, lower leg and thigh were measured by underwater weighing and B-mode ultrasound methods, respectively. No significant difference was found in body density between the weight lifters (1.077 +/- 0.007 g x ml(-3)) and wrestlers (1.076 +/- 0.008 g x ml(-3)). Moreover, FFM and the CSA values of all muscle groups tested were similar in the two groups of weight-classified athletes, with an exception that the wrist flexor CSA was significantly larger in wrestlers than in weight lifters, and the knee extensor and thigh (extensors + flexors) CSAs were larger in weight lifters than in wrestlers. The total muscle CSA of every site was significantly correlated to FFM2/3 in the separate groups; r = 0.714 to 0.815 (p < 0.05) in weight lifters and r = 0.769 to 0.919 (p < 0.05) in wrestlers. While the CSA-to-FFM2/3 ratios of the upper arm and wrist flexor muscles were significantly higher in wrestlers than in weight lifters, those of the thigh and knee extensor muscles were higher in weight lifters than in wrestlers. Thus, the present results suggest that an event-related difference exists in the magnitude of limb muscle CSA between competitive weight lifters and wrestlers of similar FFM.

High-intensity aerobic interval training can lead to improvement in skeletal muscle power among in-hospital patients with advanced heart failure.

PubMed

Taya, Masanobu; Amiya, Eisuke; Hatano, Masaru; Maki, Hisataka; Nitta, Daisuke; Saito, Akihito; Tsuji, Masaki; Hosoya, Yumiko; Minatsuki, Shun; Nakayama, Atsuko; Fujiwara, Takayuki; Konishi, Yuto; Yokota, Kazuhiko; Watanabe, Masafumi; Morita, Hiroyuki; Haga, Nobuhiko; Komuro, Issei

2018-01-15

This study investigated the effectiveness and safety of interval training during in-hospital treatment of patients with advanced heart failure. Twenty-four consecutive patients with advanced symptomatic heart failure who were referred for cardiac transplant evaluation were recruited. After performing aerobic exercise for approximate intensity, high-intensity interval training (HIIT) was performed. The protocol consisted of 3 or 4 sessions of 1-min high-intensity exercise aimed at 80% of peak VO 2 or 80% heart rate reserve, followed by 4-min recovery periods of low intensity. In addition to the necessary laboratory data, hand grip strength and knee extensor strength were evaluated at the start of exercise training and both at the start and the end of HIIT. Knee extensor strength was standardized by body weight. The BNP level at the start of exercise training was 432 (812) pg/mL and it significantly decreased to 254 (400) pg/mL (p < 0.001) at the end of HIIT. Hand grip strength did not change during course. By contrast, knee extensor strength significantly increased during HIIT [4.42 ± 1.43 → 5.28 ± 1.45 N/kg, p < 0.001], whereas the improvement of knee extensor strength was not significant from the start of exercise training to the start of HIIT. In addition, the change in knee extensor strength during HIIT was significantly associated with the hemoglobin A1c level at the start of exercise (R = - 0.55; p = 0.015). HIIT has a positive impact on skeletal muscle strength among in-hospital patients with advanced heart failure.

An index for breathlessness and leg fatigue.

PubMed

Borg, E; Borg, G; Larsson, K; Letzter, M; Sundblad, B-M

2010-08-01

The features of perceived symptoms causing discontinuation of strenuous exercise have been scarcely studied. The aim was to characterize the two main symptoms causing the discontinuation of heavy work in healthy persons as well as describe the growth of symptoms during exercise. Breathlessness (b) and leg fatigue (l) were assessed using the Borg CR10 Scale and the Borg CR100 (centiMax) Scale, during a standardized exercise test in 38 healthy subjects (24-71 years). The b/l-relationships were calculated for terminal perceptions (ERI(b/l)), and the growth of symptoms determined by power functions for the whole test, as well as by growth response indexes (GRI). This latter index was constructed as a ratio between power levels corresponding to a very strong and a moderate perception. In the majority (71%) of the test subjects, leg fatigue was the dominant symptom at the conclusion of exercise (P<0.001) and the b/l ratio was 0.77 (CR10) and 0.75 (CR100), respectively. The GRI for breathlessness and leg fatigue was similar, with good correlations between GRI and the power function exponent (P<0.005). In healthy subjects, leg fatigue is the most common cause for discontinuing an incremental exercise test. The growth functions for breathlessness and leg fatigue during work are, however, almost parallel.

Skeletal muscle water T2 as a biomarker of disease status and exercise effects in patients with Duchenne muscular dystrophy.

PubMed

Mankodi, Ami; Azzabou, Noura; Bulea, Thomas; Reyngoudt, Harmen; Shimellis, Hirity; Ren, Yupeng; Kim, Eunhee; Fischbeck, Kenneth H; Carlier, Pierre G

2017-08-01

The purpose of this study was to examine exercise effects on muscle water T 2 in patients with Duchenne muscular dystrophy (DMD). In 12 DMD subjects and 19 controls, lower leg muscle fat (%) was measured by Dixon and muscle water T 2 and R 2 (1/T 2 ) by the tri-exponential model. Muscle water R 2 was measured again at 3 hours after an ankle dorsiflexion exercise. The muscle fat fraction was higher in DMD participants than in controls (p < .001) except in the tibialis posterior muscle. Muscle water T 2 was measured independent of the degree of fatty degeneration in DMD muscle. At baseline, muscle water T 2 was higher in all but the extensor digitorum longus muscles of DMD participants than controls (p < .001). DMD participants had a lower muscle torque (p < .001) and exerted less power (p < .01) during exercise than controls. Nevertheless, muscle water R 2 decreased (T 2 increased) after exercise from baseline in DMD subjects and controls with greater changes in the target muscles of the exercise than in ankle plantarflexor muscles. Skeletal muscle water T 2 is a sensitive biomarker of the disease status in DMD and of the exercise response in DMD patients and controls. Published by Elsevier B.V.

An unusual presenting symptom of graves' disease: myalgia.

PubMed

Papanikolaou, N; Perros, P

2013-01-01

A 50-year-old female patient presented with severe myalgia involving her proximal muscles for 3-4 weeks. She also reported mild thyrotoxic symptoms over the same time period. Examination revealed mild thyrotoxicosis, a moderate diffuse goiter and no eye signs. The clinical picture was dominated by muscle pain and tenderness involving mainly her proximal arms and legs, her calves and her fingers, requiring opiate analgesia. Muscle power and tendon reflexes were normal. Laboratory evaluation revealed undetectable serum thyroid stimulating hormone (TSH) with raised FT4, FT3 and positive TSH receptor antibodies. Treatment with carbimazole was started. Additional laboratory investigations were negative (inflammatory markers, creatine kinase and antibodies to antinuclear antibodies, gastric parietal cell, smooth muscle, mitochondrial, dsDNA, centromere, extractable nuclear antigen (ENA) ribonucleoprotein, ENA Sm, ENA Ro, ENA Anti-La, ENA Scl70, ENA Jo-1, anti-CCP and rheumatoid factor). Further assessment in the rheumatology clinic confirmed there was no small joint tenderness or loss of range of movement of her limbs, but widespread and profound muscle tenderness of the common extensors of the forearms, biceps, trapezius, calves and thighs. She was treated symptomatically with analgesic medication and continued on carbimazole. A month later she was euthyroid and her myalgia had resolved. Hyperthyroidism has a profound effect on skeletal muscle and often leads to myopathy. Severe myalgia in association with Graves' disease is rare and resolves with the restoration of euthyroidism.

Effects of whole-body cryotherapy (-110 °C) on proprioception and indices of muscle damage.

PubMed

Costello, J T; Algar, L A; Donnelly, A E

2012-04-01

The purpose of this study was to investigate the effects of whole-body cryotherapy (WBC) on proprioceptive function, muscle force recovery following eccentric muscle contractions and tympanic temperature (T(TY) ). Thirty-six subjects were randomly assigned to a group receiving two 3-min treatments of -110 ± 3 °C or 15 ± 3 °C. Knee joint position sense (JPS), maximal voluntary isometric contraction (MVIC) of the knee extensors, force proprioception and T(TY) were recorded before, immediately after the exposure and again 15 min later. A convenience sample of 18 subjects also underwent an eccentric exercise protocol on their contralateral left leg 24 h before exposure. MVIC (left knee), peak power output (PPO) during a repeated sprint on a cycle ergometer and muscles soreness were measured pre-, 24, 48 and 72h post-treatment. WBC reduced T(TY) , by 0.3 °C, when compared with the control group (P<0.001). However, JPS, MVIC or force proprioception was not affected. Similarly, WBC did not effect MVIC, PPO or muscle soreness following eccentric exercise. WBC, administered 24 h after eccentric exercise, is ineffective in alleviating muscle soreness or enhancing muscle force recovery. The results of this study also indicate no increased risk of proprioceptive-related injury following WBC. © 2011 John Wiley & Sons A/S.

Effects of two neuromuscular training programs on running biomechanics with load carriage: a study protocol for a randomised controlled trial.

PubMed

Liew, Bernard X W; Morris, Susan; Keogh, Justin W L; Appleby, Brendyn; Netto, Kevin

2016-10-22

In recent years, athletes have ventured into ultra-endurance and adventure racing events, which tests their ability to race, navigate, and survive. These events often require race participants to carry some form of load, to bear equipment for navigation and survival purposes. Previous studies have reported specific alterations in biomechanics when running with load which potentially influence running performance and injury risk. We hypothesize that a biomechanically informed neuromuscular training program would optimize running mechanics during load carriage to a greater extent than a generic strength training program. This will be a two group, parallel randomized controlled trial design, with single assessor blinding. Thirty healthy runners will be recruited to participate in a six weeks neuromuscular training program. Participants will be randomized into either a generic training group, or a biomechanically informed training group. Primary outcomes include self-determined running velocity with a 20 % body weight load, jump power, hopping leg stiffness, knee extensor and triceps-surae strength. Secondary outcomes include running kinetics and kinematics. Assessments will occur at baseline and post-training. To our knowledge, no training programs are available that specifically targets a runner's ability to carry load while running. This will provide sport scientists and coaches with a foundation to base their exercise prescription on. ANZCTR ( ACTRN12616000023459 ) (14 Jan 2016).

Isolated and soft-switched power converter

DOEpatents

Peng, Fang Zheng; Adams, Donald Joe

2002-01-01

An isolated and soft-switched power converter is used for DC/DC and DC/DC/AC power conversion. The power converter includes two resonant tank circuits coupled back-to-back through an isolation transformer. Each resonant tank circuit includes a pair of resonant capacitors connected in series as a resonant leg, a pair of tank capacitors connected in series as a tank leg, and a pair of switching devices with anti-parallel clamping diodes coupled in series as resonant switches and clamping devices for the resonant leg. The power converter is well suited for DC/DC and DC/DC/AC power conversion applications in which high-voltage isolation, DC to DC voltage boost, bidirectional power flow, and a minimal number of conventional switching components are important design objectives. For example, the power converter is especially well suited to electric vehicle applications and load-side electric generation and storage systems, and other applications in which these objectives are important. The power converter may be used for many different applications, including electric vehicles, hybrid combustion/electric vehicles, fuel-cell powered vehicles with low-voltage starting, remote power sources utilizing low-voltage DC power sources, such as photovoltaics and others, electric power backup systems, and load-side electric storage and generation systems.

The Benslimane's Artistic Model for Leg Beauty.

PubMed

Benslimane, Fahd

2012-08-01

In 2000, the author started observing legs considered to be attractive. The goal was to have an ideal aesthetic model and compare the disparity between this model and a patient's reality. This could prove helpful during leg sculpturing to get closer to this ideal. Postoperatively, the result could then be compared to the ideal curves of the model legs and any remaining deviations from the ideal curves could be pointed out and eventually corrected in a second session. The lack of anthropometric studies of legs from the knee to the ankle led the author to select and study attractive legs to find out the common denominators of their beauty. The study consisted in analyzing the features that make legs look attractive. The legs of models in magazines were scanned and inserted into a PowerPoint program. The legs of live models, Barbie dolls, and athletes were photographed. Artistic drawings by Leonardo da Vinci were reviewed and Greek sculptures studied. Sculptures from the National Archaeological Museum of Athens were photographed and included in the PowerPoint program. This study shows that the first criterion for beautiful legs is the straightness of the leg column. Not a single attractive leg was found to deviate from the vertical, and each was in absolute continuity with the thigh. The second criterion is the similarity of curve distribution and progression from knee to ankle. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors at www.springer.com/00266.

Effects of back posture education on elementary schoolchildren's back function.

PubMed

Geldhof, Elisabeth; Cardon, Greet; De Bourdeaudhuij, Ilse; Danneels, Lieven; Coorevits, Pascal; Vanderstraeten, Guy; De Clercq, Dirk

2007-06-01

The possible effects of back education on children's back function were never evaluated. Therefore, main aim of the present study was to evaluate the effects of back education in elementary schoolchildren on back function parameters. Since the reliability of back function measurement in children is poorly defined, another objective was to test the selected instruments for reliability in 8-11-year olds. The multi-factorial intervention lasting two school-years consisted of a back education program and the stimulation of postural dynamism in the class. Trunk muscle endurance, leg muscle capacity and spinal curvature were evaluated in a pre-post design including 41 children who received the back education program (mean age at post-test: 11.2 +/- 0.9 years) and 28 controls (mean age at post-test: 11.4 +/- 0.6 years). Besides, test-retest reliability with a 1-week interval was investigated in a separate sample. Therefore, 47 children (mean age: 10.1 +/- 0.5 years) were tested for reliability of trunk muscle endurance and 40 children (mean age: 10.2 +/- 0.7 years) for the assessment of spinal curvatures. Reliability of endurance testing was very good to good for the trunk flexors (ICC = 0.82) and trunk extensors (ICC = 0.63). The assessment of the thoracic (ICC = 0.69) and the lumbar curvature (ICC = 0.52) in seating position showed good to acceptable reliability. Low ICCs were found for the assessment of the thoracic (ICC = 0.39) and the lumbar curvature (ICC = 0.37) in stance. The effects of 2 year back education showed an increase in trunk flexor endurance in the intervention group compared to a decrease in the controls and a trend towards significance for a higher increase in trunk extensor endurance in the intervention group. For leg muscle capacity and spinal curvature no intervention effects were found. The small samples recommend cautious interpretation of intervention effects. However, the present study's findings favor the implementation of back education with focus on postural dynamism in the class as an integral part of the elementary school curriculum in the scope of optimizing spinal loading through the school environment.

Relationship between occlusal force and falls among community-dwelling elderly in Japan: a cross-sectional correlative study.

PubMed

Eto, Maki; Miyauchi, Shinji

2018-05-09

Falls may cause serious health conditions among older population. Fall-related physical factors are thought to be associated with occlusal conditions. However, few studies examined the relationship between occlusal force and falls. To identify the association between occlusal force and falls among community-dwelling elderly individuals in Japan, public health nurses conducted a cross-sectional descriptive study. We performed extensive physical assessments of five items: maximum occlusal force, handgrip strength, maximal knee extensor strength, one-leg standing time with eyes open and body sway. We also conducted a questionnaire survey concerning the participants' demographic characteristics, health status and fall experience during the past year. Mean scores and standard deviations were calculated for age and the total points of the index of activities of daily living. Associations were examined using Mann-Whitney tests and logistic regression. We examined 159 community-dwelling people aged ≥65 years, who were independent and active, including 38 participants (24.5%) with experience of falls in the past year. Maximum occlusal force had significant correlation with handgrip strength, maximal knee extensor strength, and one-leg standing time and body sway (P < .05, respectively). We found weak associations between participants with and without a history of falls in terms of the five physical measurements. Logistic regression analysis showed that fall experience was significantly associated with maximum occlusal force (P = 0.004). This is the first study, led by public health nursing researchers, to examine the associations between maximum occlusal force and falls among community-dwelling elderly in Japan. The results showed that maximum occlusal force was significantly related to the other four extensive physical assessments, and might also suggest that maximum occlusal force assessment by public health nurses could contribute to more sophisticated and precise prediction of fall risks among the community-dwelling elderly. The latest occlusal force measurement device is non-invasive and easy to use. Public health nurses can introduce it at periodical community health checkup assembly events, which might contribute to raising awareness among community-dwelling elderly individuals and public health nurses about fall prevention and prediction.

Twelve-week combined resistance and aerobic training confers greater benefits than aerobic training alone in nondialysis CKD.

PubMed

Watson, Emma L; Gould, Douglas W; Wilkinson, Thomas J; Xenophontos, Soteris; Clarke, Amy L; Vogt, Barbara Perez; Viana, João L; Smith, Alice C

2018-06-01

There is a growing consensus that patients with chronic kidney disease (CKD) should engage in regular exercise, but there is a lack of formal guidelines. In this report, we determined whether combined aerobic and resistance exercise would elicit superior physiological gains, in particular muscular strength, compared with aerobic training alone in nondialysis CKD. Nondialysis patients with CKD stages 3b-5 were randomly allocated to aerobic exercise {AE, n = 21; 9 men; median age 63 [interquartile range (IQR) 58-71] yr; median estimated glomerular filtration rate (eGFR) 24 (IQR 20-30) ml·min -1 ·1.73 m -2 } or combined exercise [CE, n = 20, 9 men, median age 63 (IQR 51-69) yr, median eGFR 27 (IQR 22-32) ml·min -1 ·1.73 m -2 ], preceded by a 6-wk run-in control period. Patients then underwent 12 wk of supervised AE (treadmill, rowing, or cycling exercise) or CE training (as AE plus leg extension and leg press exercise) performed three times per week. Outcome assessments of knee extensor muscle strength, quadriceps muscle volume, exercise capacity, and central hemodynamics were performed at baseline, following the 6-wk control period, and at the end of the intervention. AE and CE resulted in significant increases in knee extensor strength of 16 ± 19% (mean ± SD; P = 0.001) and 48 ± 37% ( P < 0.001), respectively, which were greater after CE ( P = 0.02). AE and CE resulted in 5 ± 7% ( P = 0.04) and 9 ± 7% ( P < 0.001) increases in quadriceps volume, respectively ( P < 0.001), which were greater after CE ( P = 0.01). Both AE and CE increased distance walked in the incremental shuttle walk test [28 ± 44 m ( P = 0.01) and 32 ± 45 m ( P = 0.01), respectively]. In nondialysis CKD, the addition of resistance exercise to aerobic exercise confers greater increases in muscle mass and strength than aerobic exercise alone.

Stance controlled knee flexion improves stimulation driven walking after spinal cord injury

PubMed Central

2013-01-01

Background Functional neuromuscular stimulation (FNS) restores walking function after paralysis from spinal cord injury via electrical activation of muscles in a coordinated fashion. Combining FNS with a controllable orthosis to create a hybrid neuroprosthesis (HNP) has the potential to extend walking distance and time by mechanically locking the knee joint during stance to allow knee extensor muscle to rest with stimulation turned off. Recent efforts have focused on creating advanced HNPs which couple joint motion (e.g., hip and knee or knee and ankle) to improve joint coordination during swing phase while maintaining a stiff-leg during stance phase. Methods The goal of this study was to investigate the effects of incorporating stance controlled knee flexion during loading response and pre-swing phases on restored gait. Knee control in the HNP was achieved by a specially designed variable impedance knee mechanism (VIKM). One subject with a T7 level spinal cord injury was enrolled and served as his own control in examining two techniques to restore level over-ground walking: FNS-only (which retained a stiff knee during stance) and VIKM-HNP (which allowed controlled knee motion during stance). The stimulation pattern driving the walking motion remained the same for both techniques; the only difference was that knee extensor stimulation was constant during stance with FNS-only and modulated together with the VIKM to control knee motion during stance with VIKM-HNP. Results Stance phase knee angle was more natural during VIKM-HNP gait while knee hyperextension persisted during stiff-legged FNS-only walking. During loading response phase, vertical ground reaction force was less impulsive and instantaneous gait speed was increased with VIKM-HNP, suggesting that knee flexion assisted in weight transfer to the leading limb. Enhanced knee flexion during pre-swing phase also aided flexion during swing, especially when response to stimulation was compromised. Conclusions These results show the potential advantages of incorporating stance controlled knee flexion into a hybrid neuroprosthesis for walking. The addition of such control to FNS driven walking could also enable non-level walking tasks such as uneven terrain, slope navigation and stair descent where controlled knee flexion during weight bearing is critical. PMID:23826711

Effect of walking velocity on hindlimb kinetics during stance in normal horses.

PubMed

Khumsap, S; Clayton, H M; Lanovaz, J L

2001-04-01

The objectives of this study were to measure the effect of walking velocity on net joint moments and joint powers in the hindlimb during stance and to use the data to predict these variables at different walking velocities. Videographic and force data were collected synchronously from 5 sound horses walking over a force plate at a range of velocities. Force and kinematic data from 56 trials were combined using an inverse dynamic solution to determine net joint moments and joint powers. Analysis by simple regression and correlation (P < 0.05, r2 > or = 0.30, r > 0.50) showed that, in early stance, there were significant velocity-dependent increases in the peak magnitudes of the following variables: extensor moment and positive power at the hip, flexor moment and positive power at the stifle, extensor moment, negative and positive power at the tarsus, and flexor moment and negative power at the fetlock. In late stance, there were significant velocity-dependent increases in the peak magnitudes of the following variables: flexor moment at the hip, negative power at the stifle and flexor moment and positive power at the tarsus. As velocity increased, the hip showed an increase in energy generation, whereas the tarsus showed increases in both energy generation and absorption. It is concluded that an increase in walking velocity is associated with increases in peak magnitudes of the net joint moments and joint powers in the hindlimb; and that energy generation at the hip makes the largest contribution to the increase in velocity.

Hip-Extensor Strength, Trunk Posture, and Use of the Knee-Extensor Muscles During Running.

PubMed

Teng, Hsiang-Ling; Powers, Christopher M

2016-07-01

Diminished hip-muscle performance has been proposed to contribute to various knee injuries. To determine the association between hip-extensor muscle strength and sagittal-plane trunk posture and the relationships among hip-extensor muscle strength and hip- and knee-extensor work during running. Descriptive laboratory study. Musculoskeletal biomechanical laboratory. A total of 40 asymptomatic recreational runners, 20 men (age = 27.1 ± 7.0 years, height = 1.74 ± 0.69 m, mass = 71.1 ± 8.2 kg) and 20 women (age = 26.2 ± 5.8 years, height = 1.65 ± 0.74 m, mass = 60.6 ± 6.6 kg), participated. Maximum isometric strength of the hip extensors was assessed using a dynamometer. Sagittal-plane trunk posture (calculated relative to the global vertical axis) and hip- and knee-extensor work (sum of energy absorption and generation) during the stance phase of running were quantified while participants ran over ground at a controlled speed of 3.4 m/s. We used Pearson product moment correlations to examine the relationships among hip-extensor strength, mean sagittal-plane trunk-flexion angle, hip-extensor work, and knee-extensor work. Hip-extensor strength was correlated positively with trunk-flexion angle (r = 0.55, P < .001) and hip-extensor work (r = 0.46, P = .003). It was correlated inversely with knee-extensor work (r = -0.39, P = .01). All the correlations remained after adjusting for sex. Our findings suggest that runners with hip-extensor weakness used a more upright trunk posture. This strategy led to an overreliance on the knee extensors and may contribute to overuse running injuries at the knee.

Hip-Extensor Strength, Trunk Posture, and Use of the Knee-Extensor Muscles During Running

PubMed Central

Teng, Hsiang-Ling; Powers, Christopher M.

2016-01-01

Context:  Diminished hip-muscle performance has been proposed to contribute to various knee injuries. Objective:  To determine the association between hip-extensor muscle strength and sagittal-plane trunk posture and the relationships among hip-extensor muscle strength and hip- and knee-extensor work during running. Design:  Descriptive laboratory study. Setting:  Musculoskeletal biomechanical laboratory. Patients or Other Participants:  A total of 40 asymptomatic recreational runners, 20 men (age = 27.1 ± 7.0 years, height = 1.74 ± 0.69 m, mass = 71.1 ± 8.2 kg) and 20 women (age = 26.2 ± 5.8 years, height = 1.65 ± 0.74 m, mass = 60.6 ± 6.6 kg), participated. Main Outcome Measure(s):  Maximum isometric strength of the hip extensors was assessed using a dynamometer. Sagittal-plane trunk posture (calculated relative to the global vertical axis) and hip- and knee-extensor work (sum of energy absorption and generation) during the stance phase of running were quantified while participants ran over ground at a controlled speed of 3.4 m/s. We used Pearson product moment correlations to examine the relationships among hip-extensor strength, mean sagittal-plane trunk-flexion angle, hip-extensor work, and knee-extensor work. Results:  Hip-extensor strength was correlated positively with trunk-flexion angle (r = 0.55, P < .001) and hip-extensor work (r = 0.46, P = .003). It was correlated inversely with knee-extensor work (r = −0.39, P = .01). All the correlations remained after adjusting for sex. Conclusions:  Our findings suggest that runners with hip-extensor weakness used a more upright trunk posture. This strategy led to an overreliance on the knee extensors and may contribute to overuse running injuries at the knee. PMID:27513169

Isometric muscle strength and mobility capacity in children with cerebral palsy.

PubMed

Dallmeijer, Annet J; Rameckers, Eugene A; Houdijk, Han; de Groot, Sonja; Scholtes, Vanessa A; Becher, Jules G

2017-01-01

To determine the relationship between isometric leg muscle strength and mobility capacity in children with cerebral palsy (CP) compared to typically developing (TD) peers. Participants were 62 children with CP (6-13 years), able to walk with (n = 10) or without (n = 52) walking aids, and 47 TD children. Isometric muscle strength of five muscle groups of the leg was measured using hand-held dynamometry. Mobility capacity was assessed with the 1-min walk, the 10-m walk, sit-to-stand, lateral-step-up and timed-stair tests. Isometric strength of children with CP was reduced to 36-82% of TD. When adjusted for age and height, the percentage of variance in mobility capacity that was explained by isometric strength of the leg muscles was 21-24% (walking speed), 25% (sit-to-stand), 28% (lateral-step-up) and 35% (timed-stair) in children with CP. Hip abductors and knee flexors had the largest contribution to the explained variance, while knee extensors showed the weakest correlation. Weak or no associations were found between strength and mobility capacity in TD children. Isometric strength, especially hip abductor and knee flexor strength, is moderately related to mobility capacity in children with CP, but not in TD children. To what extent training of these muscle groups will lead to better mobility capacity needs further study. Implications for Rehabilitation Strength training in children with cerebral palsy (CP) may be targeted more specifically at hip abductors and knee flexors. The moderate associations imply that large improvements in mobility capacity may not be expected when strength increases.

Hemodynamic responses to small muscle mass exercise in heart failure patients with reduced ejection fraction

PubMed Central

Barrett-O'Keefe, Zachary; Lee, Joshua F.; Berbert, Amanda; Witman, Melissa A. H.; Nativi-Nicolau, Jose; Stehlik, Josef; Richardson, Russell S.

2014-01-01

To better understand the mechanisms responsible for exercise intolerance in heart failure with reduced ejection fraction (HFrEF), the present study sought to evaluate the hemodynamic responses to small muscle mass exercise in this cohort. In 25 HFrEF patients (64 ± 2 yr) and 17 healthy, age-matched control subjects (64 ± 2 yr), mean arterial pressure (MAP), cardiac output (CO), and limb blood flow were examined during graded static-intermittent handgrip (HG) and dynamic single-leg knee-extensor (KE) exercise. During HG exercise, MAP increased similarly between groups. CO increased significantly (+1.3 ± 0.3 l/min) in the control group, but it remained unchanged across workloads in HFrEF patients. At 15% maximum voluntary contraction (MVC), forearm blood flow was similar between groups, while HFrEF patients exhibited an attenuated increase at the two highest intensities compared with controls, with the greatest difference at the highest workload (352 ± 22 vs. 492 ± 48 ml/min, HFrEF vs. control, 45% MVC). During KE exercise, MAP and CO increased similarly across work rates between groups. However, HFrEF patients exhibited a diminished leg hyperemic response across all work rates, with the most substantial decrement at the highest intensity (1,842 ± 64 vs. 2,675 ± 81 ml/min; HFrEF vs. control, 15 W). Together, these findings indicate a marked attenuation in exercising limb perfusion attributable to impairments in peripheral vasodilatory capacity during both arm and leg exercise in patients with HFrEF, which likely plays a role in limiting exercise capacity in this patient population. PMID:25260608

Do lower-extremity joint dynamics change when stair negotiation is initiated with a self-selected comfortable gait speed?

PubMed

Vallabhajosula, Srikant; Yentes, Jennifer M; Momcilovic, Mira; Blanke, Daniel J; Stergiou, Nicholas

2012-02-01

Previous research on the biomechanics of stair negotiation has ignored the effect of the approaching speed. We examined if initiating stair ascent with a comfortable self-selected speed can affect the lower-extremity joint moments and powers as compared to initiating stair ascent directly in front of the stairs. Healthy young adults ascended a custom-built staircase instrumented with force platforms. Kinematics and kinetics data were collected simultaneously for two conditions: starting from farther away and starting in front of the stairs and analyzed at the first and second ipsilateral steps. Results showed that for the first step, participants produced greater peak knee extensor moment, peak hip extensor and flexor moments and peak hip positive power while starting from farther away. Also, for both the conditions combined, participants generated lesser peak ankle plantiflexor, greater peak knee flexor moment, lesser peak ankle negative power and greater peak hip negative power while encountering the first step. These results identify the importance of the starting position in experiments dealing with biomechanics of stair negotiation. Further, these findings have important implications for studying stair ascent characteristics of other populations such as older adults. Copyright © 2011 Elsevier B.V. All rights reserved.

Electric vehicle system for charging and supplying electrical power

DOEpatents

Su, Gui Jia

2010-06-08

A power system that provides power between an energy storage device, an external charging-source/load, an onboard electrical power generator, and a vehicle drive shaft. The power system has at least one energy storage device electrically connected across a dc bus, at least one filter capacitor leg having at least one filter capacitor electrically connected across the dc bus, at least one power inverter/converter electrically connected across the dc bus, and at least one multiphase motor/generator having stator windings electrically connected at one end to form a neutral point and electrically connected on the other end to one of the power inverter/converters. A charging-sourcing selection socket is electrically connected to the neutral points and the external charging-source/load. At least one electronics controller is electrically connected to the charging-sourcing selection socket and at least one power inverter/converter. The switch legs in each of the inverter/converters selected by the charging-source/load socket collectively function as a single switch leg. The motor/generators function as an inductor.

Kicking Back Cognitive Ageing: Leg Power Predicts Cognitive Ageing after Ten Years in Older Female Twins

PubMed Central

Steves, Claire J.; Mehta, Mitul M.; Jackson, Stephen H.D.; Spector, Tim D.

2016-01-01

Background Many observational studies have shown a protective effect of physical activity on cognitive ageing, but interventional studies have been less convincing. This may be due to short time scales of interventions, suboptimal interventional regimes or lack of lasting effect. Confounding through common genetic and developmental causes is also possible. Objectives We aimed to test whether muscle fitness (measured by leg power) could predict cognitive change in a healthy older population over a 10-year time interval, how this performed alongside other predictors of cognitive ageing, and whether this effect was confounded by factors shared by twins. In addition, we investigated whether differences in leg power were predictive of differences in brain structure and function after 12 years of follow-up in identical twin pairs. Methods A total of 324 healthy female twins (average age at baseline 55, range 43-73) performed the Cambridge Neuropsychological Test Automated Battery (CANTAB) at two time points 10 years apart. Linear regression modelling was used to assess the relationships between baseline leg power, physical activity and subsequent cognitive change, adjusting comprehensively for baseline covariates (including heart disease, diabetes, blood pressure, fasting blood glucose, lipids, diet, body habitus, smoking and alcohol habits, reading IQ, socioeconomic status and birthweight). A discordant twin approach was used to adjust for factors shared by twins. A subset of monozygotic pairs then underwent magnetic resonance imaging. The relationship between muscle fitness and brain structure and function was assessed using linear regression modelling and paired t tests. Results A striking protective relationship was found between muscle fitness (leg power) and both 10-year cognitive change [fully adjusted model standardised β-coefficient (Stdβ) = 0.174, p = 0.002] and subsequent total grey matter (Stdβ = 0.362, p = 0.005). These effects were robust in discordant twin analyses, where within-pair difference in physical fitness was also predictive of within-pair difference in lateral ventricle size. There was a weak independent effect of self-reported physical activity. Conclusion Leg power predicts both cognitive ageing and global brain structure, despite controlling for common genetics and early life environment shared by twins. Interventions targeted to improve leg power in the long term may help reach a universal goal of healthy cognitive ageing. PMID:26551663

Kicking Back Cognitive Ageing: Leg Power Predicts Cognitive Ageing after Ten Years in Older Female Twins.

PubMed

Steves, Claire J; Mehta, Mitul M; Jackson, Stephen H D; Spector, Tim D

2016-01-01

Many observational studies have shown a protective effect of physical activity on cognitive ageing, but interventional studies have been less convincing. This may be due to short time scales of interventions, suboptimal interventional regimes or lack of lasting effect. Confounding through common genetic and developmental causes is also possible. We aimed to test whether muscle fitness (measured by leg power) could predict cognitive change in a healthy older population over a 10-year time interval, how this performed alongside other predictors of cognitive ageing, and whether this effect was confounded by factors shared by twins. In addition, we investigated whether differences in leg power were predictive of differences in brain structure and function after 12 years of follow-up in identical twin pairs. A total of 324 healthy female twins (average age at baseline 55, range 43-73) performed the Cambridge Neuropsychological Test Automated Battery (CANTAB) at two time points 10 years apart. Linear regression modelling was used to assess the relationships between baseline leg power, physical activity and subsequent cognitive change, adjusting comprehensively for baseline covariates (including heart disease, diabetes, blood pressure, fasting blood glucose, lipids, diet, body habitus, smoking and alcohol habits, reading IQ, socioeconomic status and birthweight). A discordant twin approach was used to adjust for factors shared by twins. A subset of monozygotic pairs then underwent magnetic resonance imaging. The relationship between muscle fitness and brain structure and function was assessed using linear regression modelling and paired t tests. A striking protective relationship was found between muscle fitness (leg power) and both 10-year cognitive change [fully adjusted model standardised β-coefficient (Stdβ) = 0.174, p = 0.002] and subsequent total grey matter (Stdβ = 0.362, p = 0.005). These effects were robust in discordant twin analyses, where within-pair difference in physical fitness was also predictive of within-pair difference in lateral ventricle size. There was a weak independent effect of self-reported physical activity. Leg power predicts both cognitive ageing and global brain structure, despite controlling for common genetics and early life environment shared by twins. Interventions targeted to improve leg power in the long term may help reach a universal goal of healthy cognitive ageing. © 2015 The Author(s) Published by S. Karger AG, Basel.

The role of intrinsic muscle mechanics in the neuromuscular control of stable running in the guinea fowl

PubMed Central

Daley, Monica A; Voloshina, Alexandra; Biewener, Andrew A

2009-01-01

Here we investigate the interplay between intrinsic mechanical and neural factors in muscle contractile performance during running, which has been less studied than during walking. We report in vivo recordings of the gastrocnemius muscle of the guinea fowl (Numida meleagris), during the response and recovery from an unexpected drop in terrain. Previous studies on leg and joint mechanics following this perturbation suggested that distal leg extensor muscles play a key role in stabilisation. Here, we test this through direct recordings of gastrocnemius fascicle length (using sonomicrometry), muscle–tendon force (using buckle transducers), and activity (using indwelling EMG). Muscle recordings were analysed from the stride just before to the second stride following the perturbation. The gastrocnemius exhibits altered force and work output in the perturbed and first recovery strides. Muscle work correlates strongly with leg posture at the time of ground contact. When the leg is more extended in the drop step, net gastrocnemius work decreases (−5.2 J kg−1versus control), and when the leg is more flexed in the step back up, it increases (+9.8 J kg−1versus control). The muscle's work output is inherently stabilising because it pushes the body back toward its pre-perturbation (level running) speed and leg posture. Gastrocnemius length and force return to level running means by the second stride following the perturbation. EMG intensity differs significantly from level running only in the first recovery stride following the perturbation, not within the perturbed stride. The findings suggest that intrinsic mechanical factors contribute substantially to the initial changes in muscle force and work. The statistical results suggest that a history-dependent effect, shortening deactivation, may be an important factor in the intrinsic mechanical changes, in addition to instantaneous force–velocity and force–length effects. This finding suggests the potential need to incorporate history-dependent muscle properties into neuromechanical simulations of running, particularly if high muscle strains are involved and stability characteristics are important. Future work should test whether a Hill or modified Hill type model provides adequate prediction in such conditions. Interpreted in light of previous studies on walking, the findings support the concept of speed-dependent roles of reflex feedback. PMID:19359369

A New Training for Older Adults Using Combined Neuromuscular Electrical Stimulation and Volitional Contraction: A Pilot Study.

PubMed

Takano, Yoshio; Matsuse, Hiroo; Tsukada, Yuuya; Omoto, Masayuki; Hashida, Ryuki; Shiba, Naoto

2016-01-01

The hybrid training system (HTS) resists the motion of a volitionally contracting agonist muscle using force generated by its electrically stimulated antagonist. We have developed a new training method using the principle of HTS. This study was designed to evaluate the effect of HTS with electrical stimulation on muscle strength and physical function by comparing it against training without electrical stimulation in older adults. 16 subjects were randomly divided into two groups: the squat and single leg lift training (control, CTR) group, and the CTR with HTS training group. Some electrical stimulation was applied to the quadriceps and hamstring muscles in the HTS group. The subjects performed training for 25 min per session 3 times a week for 12 weeks. At points before and after the research maximal isokinetic torque, knee-flexors (KFT) and knee-extensors (KET), a one-leg standing test (OLT), a functional reach test (FRT), a 10-meter maximal gait time (10MGT) and Timed up & go test (TUG) were conducted. None of the subjects had any injuries during the study period. TUG significantly improved after the training period in both the HTS group (7.15 sec to 6.01 sec P = 0.01) and in the CTR.

What triggers the continuous muscle activity during upright standing?

PubMed

Masani, Kei; Sayenko, Dimitry G; Vette, Albert H

2013-01-01

The ankle extensors play a dominant role in controlling the equilibrium during bipedal quiet standing. Their primary role is to resist the gravity toppling torque that pulls the body forward. The purpose of this study was to investigate whether the continuous muscle activity of the anti-gravity muscles during standing is triggered by the joint torque requirement for opposing the gravity toppling torque, rather than by the vertical load on the lower limbs. Healthy adults subjects stood on a force plate. The ankle torque, ankle angle, and electromyograms from the right lower leg muscles were measured. A ground-fixed support device was used to support the subject at his/her knees, without changing the posture from the free standing one. During the supported condition, which eliminates the ankle torque requirement while maintaining both the vertical load on the lower limbs and the natural upright standing posture, the plantarflexor activity was attenuated to the resting level. Also, this attenuated plantarflexor activity was found only in one side when the ipsilateral leg was supported. Our results suggest that the vertical load on the lower limb is not determinant for inducing the continuous muscle activity in the anti-gravity muscles, but that it depends on the required joint torque to oppose the gravity toppling torque. Copyright © 2012 Elsevier B.V. All rights reserved.

A comparison of free weight squat to Smith machine squat using electromyography.

PubMed

Schwanbeck, Shane; Chilibeck, Philip D; Binsted, Gordon

2009-12-01

The purpose of this experiment was to determine whether free weight or Smith machine squats were optimal for activating the prime movers of the legs and the stabilizers of the legs and the trunk. Six healthy participants performed 1 set of 8 repetitions (using a weight they could lift 8 times, i.e., 8RM, or 8 repetition maximum) for each of the free weight squat and Smith machine squat in a randomized order with a minimum of 3 days between sessions, while electromyographic (EMG) activity of the tibialis anterior, gastrocnemius, vastus medialis, vastus lateralis, biceps femoris, lumbar erector spinae, and rectus abdominus were simultaneously measured. Electromyographic activity was significantly higher by 34, 26, and 49 in the gastrocnemius, biceps femoris, and vastus medialis, respectively, during the free weight squat compared to the Smith machine squat (p < 0.05). There were no significant differences between free weight and Smith machine squat for any of the other muscles; however, the EMG averaged over all muscles during the free weight squat was 43% higher when compared to the Smith machine squat (p < 0.05). The free weight squat may be more beneficial than the Smith machine squat for individuals who are looking to strengthen plantar flexors, knee flexors, and knee extensors.

Muscle activities used by young and old adults when stepping to regain balance during a forward fall.

PubMed

Thelen, D G; Muriuki, M; James, J; Schultz, A B; Ashton-Miller, J A; Alexander, N B

2000-04-01

The current study was undertaken to determine if age-related differences in muscle activities might relate to older adults being significantly less able than young adults to recover balance during a forward fall. Fourteen young and twelve older healthy males were released from forward leans of various magnitudes and asked to regain standing balance by taking a single forward step. Myoelectric signals were recorded from 12 lower extremity muscles and processed to compare the muscle activation patterns of young and older adults. Young adults successfully recovered from significantly larger leans than older adults using a single step (32.2 degrees vs. 23.5 degrees ). Muscular latency times, the time between release and activity onset, ranged from 73 to 114 ms with no significant age-related differences in the shortest muscular latency times. The overall response muscular activation patterns were similar for young and older adults. However older adults were slower to deactivate three stance leg muscles and also demonstrated delays in activating the step leg hip flexors and knee extensors prior to and during the swing phase. In the forward fall paradigm studied, age-differences in balance recovery performance do not seem due to slowness in response onset but may relate to differences in muscle activation timing during the stepping movement.

Lower eccentric hamstring strength and single leg hop for distance predict hamstring injury in PETE students.

PubMed

Goossens, L; Witvrouw, E; Vanden Bossche, L; De Clercq, D

2015-01-01

Hamstring injuries have not been under research in physical education teacher education (PETE) students so far. Within the frame of the development of an injury prevention program, for this study we conducted an analysis of modifiable risk factors for hamstring injuries in PETE students. Hamstring injuries of 102 freshmen bachelor PETE students were registered prospectively during one academic year. Eighty-one students completed maximum muscle strength tests of hip extensors, hamstrings, quadriceps (isometric) and hamstrings (eccentric) at the start of the academic year. Sixty-nine of the latter completed a single leg hop for distance (SLHD). Risk factors for hamstring injuries were statistically detected using logistic regression. Sixteen hamstring injuries (0.16 injuries/student/academic year; 0.46 injuries/1000 h) occurred to 10 participants. Eight cases were included in the risk factor analysis. Lower eccentric hamstring strength (odds ratio (ODD) = 0.977; p = 0.043), higher isometric/eccentric hamstring strength ratio (ODD = 970.500; p = 0.019) and lower score on the SLHD (ODD = 0.884; p = 0.005) were significant risk factors for hamstring injury. A combination of eccentric hamstring strength test and SLHD could give a good risk analysis of hamstring injuries in PETE students. This might offer great perspectives for easily applicable screening in a clinical setting.

Motor neurone responses during a postural reflex in solitarious and gregarious desert locusts.

PubMed

Blackburn, Laura M; Ott, Swidbert R; Matheson, Tom; Burrows, Malcolm; Rogers, Stephen M

2010-08-01

Desert locusts show extreme phenotypic plasticity and can change reversibly between two phases that differ radically in morphology, physiology and behaviour. Solitarious locusts are cryptic in appearance and behaviour, walking slowly with the body held close to the ground. Gregarious locusts are conspicuous in appearance and much more active, walking rapidly with the body held well above the ground. During walking, the excursion of the femoro-tibial (F-T) joint of the hind leg is smaller in solitarious locusts, and the joint is kept more flexed throughout an entire step. Under open loop conditions, the slow extensor tibiae (SETi) motor neurone of solitarious locusts shows strong tonic activity that increases at more extended F-T angles. SETi of gregarious locusts by contrast showed little tonic activity. Simulated flexion of the F-T joint elicits resistance reflexes in SETi in both phases, but regardless of the initial and final position of the leg, the spiking rate of SETi during these reflexes was twice as great in solitarious compared to gregarious locusts. This increased sensory-motor gain in the neuronal networks controlling postural reflexes in solitarious locusts may be linked to the occurrence of pronounced behavioural catalepsy in this phase similar to other cryptic insects such as stick insects. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Squat Jump Performance during Growth in Both Sexes: Comparison with Cycling Power

ERIC Educational Resources Information Center

Dore, Eric; Bedu, Mario; Van Praagh, Emmanuel

2008-01-01

The purpose of this cross-sectional study was to investigate leg muscle power and compare two activities (jumping and cycling) in 383 girls and 407 boys ages 9-19 years. Results in anthropometric characteristics and jumping performance were comparable until midadolescence, and sex differences were observed. Lean leg volume (LLV) was the reason for…

The influence of muscle fiber type composition on the patterns of responses for electromyographic and mechanomyographic amplitude and mean power frequency during a fatiguing submaximal isometric muscle action.

PubMed

Beck, T W; Housh, T J; Fry, A C; Cramer, J T; Weir, J P; Schilling, B K; Falvo, M J; Moore, C A

2007-07-01

The purpose of this investigation was to examine the influence of muscle fiber type composition on the patterns of responses for electromyographic (EMG) and mechanomyographic (MMG) amplitude and mean power frequency (MPF) during a fatiguing submaximal isometric muscle action. Five resistance-trained (mean +/- SD age = 23.2 +/- 3.7 yrs) and five aerobically-trained (mean +/- SD age = 32.6 +/- 5.2 yrs) men volunteered to perform a fatiguing, 30-sec submaximal isometric muscle action of the leg extensors at 50% of the maximum voluntary contraction (MVC). Muscle biopsies from the vastus lateralis revealed that the myosin heavy chain (MHC) composition for the resistance-trained subjects was 59.0 +/- 4.2% Type IIa, 0.1 +/- 0.1% Type IIx, and 40.9 +/- 4.3% Type I. The aerobically-trained subjects had 27.4 +/- 7.8% Type IIa, 0.0 +/- 0.0% Type IIx, and 72.6 +/- 7.8% Type I MHC. The patterns of responses and mean values for absolute and normalized EMG amplitude and MPF during the fatiguing muscle action were similar for the resistance-trained and aerobically-trained subjects. The resistance-trained subjects demonstrated relatively stable levels for absolute and normalized MMG amplitude and MPF across time, but the aerobically-trained subjects showed increases in MMG amplitude and decreases in MMG MPE The absolute MMG amplitude and MPF values for the resistance-trained subjects were also greater than those for the aerobi-cally-trained subjects. These findings suggested that unlike surface EMG, MMG may be a useful noninvasive technique for examining fatigue-related differences in muscle fiber type composition.

Muscle fiber type-specific response of Hsp70 expression in human quadriceps following acute isometric exercise.

PubMed

Tupling, A R; Bombardier, E; Stewart, R D; Vigna, C; Aqui, A E

2007-12-01

To investigate the time course of fiber type-specific heat shock protein 70 (Hsp70) expression in human skeletal muscle after acute exercise, 10 untrained male volunteers performed single-legged isometric knee extensor exercise at 60% of their maximal voluntary contraction (MVC) with a 50% duty cycle (5-s contraction and 5-s relaxation) for 30 min. Muscle biopsies were collected from the vastus lateralis before (Pre) exercise in the rested control leg (C) and immediately after exercise (Post) in the exercised leg (E) only and on recovery days 1 (R1), 2 (R2), 3 (R3), and 6 (R6) from both legs. As demonstrated by Western blot analysis, whole muscle Hsp70 content was unchanged (P > 0.05) immediately after exercise (Pre vs. Post), was increased (P < 0.05) by approximately 43% at R1, and remained elevated throughout the entire recovery period in E only. Hsp70 expression was also assessed in individual muscle fiber types I, IIA, and IIAX/IIX by immunohistochemistry. There were no fiber type differences (P > 0.05) in basal Hsp70 expression. Immediately after exercise, Hsp70 expression was increased (P < 0.05) in type I fibers by approximately 87% but was unchanged (P > 0.05) in type II fibers (Pre vs. Post). At R1 and throughout recovery, Hsp70 content in E was increased above basal levels (P < 0.05) in all fiber types, but Hsp70 expression was always highest (P < 0.05) in type I fibers. Hsp70 content in C was not different from Pre at any time throughout recovery. Glycogen depletion was observed at Post in all type II, but not type I, fibers, suggesting that the fiber type differences in exercise-induced Hsp70 expression were not related to glycogen availability. These results demonstrate that the time course of exercise-induced Hsp70 expression in human skeletal muscle is fiber type specific.

[Perinatal model of human transition from hypogravity to the earth's gravity based on the electromyogram nonlinear characteristics].

PubMed

Meĭgal, A Iu; Voroshilov, A S

2009-01-01

Interferential electromyogram (iEMG) was analyzed in healthy newborn infants (n=29) during the first 24 hours of life as a model of transition from hypogravity (intrauterine immersion) to the Earth's gravity (postnatal period). Nonlinear instruments of iEMG analysis (correlation dimension, entropy and fractal dimension) reflected the complexity, chaotic character and predictability of signals from the leg and arm antagonistic muscles. Except for m. gastrocnemius, in all other musles iEMG fractal dimension was shown to grow as the postnatal period extended. Low fractal and correlation dimensions and entropy marked flexor muscles, particularly against low iEMG amplitude suggesting a better congenital programming for the flexors as compared to the extensors. It is concluded that the early ontogenesis model can be practicable in studying the evolution and states of antigravity functions.

Optimization of Thermoelectric Components for Automobile Waste Heat Recovery Systems

NASA Astrophysics Data System (ADS)

Kumar, Sumeet; Heister, Stephen D.; Xu, Xianfan; Salvador, James R.

2015-10-01

For a typical spark ignition engine approximately 40% of available thermal energy is lost as hot exhaust gas. To improve fuel economy, researchers are currently evaluating technology which exploits exhaust stream thermal power by use of thermoelectric generators (TEGs) that operate on the basis of the Seebeck effect. A 5% improvement in fuel economy, achieved by use of TEG output power, is a stated objective for light-duty trucks and personal automobiles. System modeling of thermoelectric (TE) components requires solution of coupled thermal and electric fluxes through the n and p-type semiconductor legs, given appropriate thermal boundary conditions at the junctions. Such applications have large thermal gradients along the semiconductor legs, and material properties are highly dependent on spatially varying temperature profiles. In this work, one-dimensional heat flux and temperature variations across thermoelectric legs were solved by using an iterative numerical approach to optimize both TE module and TEG designs. Design traits were investigated by assuming use of skutterudite as a thermoelectric material with potential for automotive applications in which exhaust gas and heat exchanger temperatures typically vary from 100°C to over 600°C. Dependence of leg efficiency, thermal fluxes and electric power generation on leg geometry, fill fractions, electric current, thermal boundary conditions, etc., were studied in detail. Optimum leg geometries were computed for a variety of automotive exhaust conditions.

Virtual Constraint Control of a Powered Prosthetic Leg: From Simulation to Experiments with Transfemoral Amputees.

PubMed

Gregg, Robert D; Lenzi, Tommaso; Hargrove, Levi J; Sensinger, Jonathon W

2014-12-01

Recent powered (or robotic) prosthetic legs independently control different joints and time periods of the gait cycle, resulting in control parameters and switching rules that can be difficult to tune by clinicians. This challenge might be addressed by a unifying control model used by recent bipedal robots, in which virtual constraints define joint patterns as functions of a monotonic variable that continuously represents the gait cycle phase. In the first application of virtual constraints to amputee locomotion, this paper derives exact and approximate control laws for a partial feedback linearization to enforce virtual constraints on a prosthetic leg. We then encode a human-inspired invariance property called effective shape into virtual constraints for the stance period. After simulating the robustness of the partial feedback linearization to clinically meaningful conditions, we experimentally implement this control strategy on a powered transfemoral leg. We report the results of three amputee subjects walking overground and at variable cadences on a treadmill, demonstrating the clinical viability of this novel control approach.

Virtual Constraint Control of a Powered Prosthetic Leg: From Simulation to Experiments with Transfemoral Amputees

PubMed Central

Lenzi, Tommaso; Hargrove, Levi J.; Sensinger, Jonathon W.

2014-01-01

Recent powered (or robotic) prosthetic legs independently control different joints and time periods of the gait cycle, resulting in control parameters and switching rules that can be difficult to tune by clinicians. This challenge might be addressed by a unifying control model used by recent bipedal robots, in which virtual constraints define joint patterns as functions of a monotonic variable that continuously represents the gait cycle phase. In the first application of virtual constraints to amputee locomotion, this paper derives exact and approximate control laws for a partial feedback linearization to enforce virtual constraints on a prosthetic leg. We then encode a human-inspired invariance property called effective shape into virtual constraints for the stance period. After simulating the robustness of the partial feedback linearization to clinically meaningful conditions, we experimentally implement this control strategy on a powered transfemoral leg. We report the results of three amputee subjects walking overground and at variable cadences on a treadmill, demonstrating the clinical viability of this novel control approach. PMID:25558185

Electrical system for pulse-width modulated control of a power inverter using phase-shifted carrier signals and related operating methods

DOEpatents

Welchko, Brian A [Torrance, CA

2012-02-14

Systems and methods are provided for pulse-width modulated control of power inverter using phase-shifted carrier signals. An electrical system comprises an energy source and a motor. The motor has a first set of windings and a second set of windings, which are electrically isolated from each other. An inverter module is coupled between the energy source and the motor and comprises a first set of phase legs coupled to the first set of windings and a second set of phase legs coupled to the second set of windings. A controller is coupled to the inverter module and is configured to achieve a desired power flow between the energy source and the motor by modulating the first set of phase legs using a first carrier signal and modulating the second set of phase legs using a second carrier signal. The second carrier signal is phase-shifted relative to the first carrier signal.

Implementation of a long leg X-point target divertor in the ARC fusion pilot plant

NASA Astrophysics Data System (ADS)

Kuang, A. Q.; Cao, N. M.; Creely, A. J.; Dennett, C. A.; Hecla, J.; Hoffman, H.; Major, M.; Ruiz Ruiz, J.; Tinguely, R. A.; Tolman, E. A.; Brunner, D.; Labombard, B.; Sorbom, B. N.; Whyte, D. G.; Grover, P.; Laughman, C.

2017-10-01

A long leg X-point target divertor geometry in a double null geometry has been implemented in the ARC pilot plant design, exploiting ARC's demountable toroidal field (TF) coils and FLiBe immersion blanket, which allow superconducting poloidal field coils to be located inside the TF coils, adequately shielded from neutrons. This new design maintains the original TF coil size, core plasma shape, and attains a tritium breedin ratio 1.08. The long leg divertor geometry provides significant advantages. Neutron transport computations indicate a factor of 10 reduction in divertor material neutron damage rate compared to the first wall, easing requirements for high heat flux components. Simulations have shown that long legged divertors are able to maintain a passively stable detachment front that stays in the divertor leg over a wide power window, in principle, responding immediately to fast changes in power exhaust. The ARC design exploits this new paradigm for divertor heat flux control: fewer concerns about coping with fast transients and a focus on neutron-tolerant diagnostics to measure and adjust detachment front locations in the outer divertor legs over long timescales.

Toward Balance Recovery With Leg Prostheses Using Neuromuscular Model Control

PubMed Central

Geyer, Hartmut

2016-01-01

Objective Lower limb amputees are at high risk of falling as current prosthetic legs provide only limited functionality for recovering balance after unexpected disturbances. For instance, the most established control method used on powered leg prostheses tracks local joint impedance functions without taking the global function of the leg in balance recovery into account. Here we explore an alternative control policy for powered transfemoral prostheses that considers the global leg function and is based on a neuromuscular model of human locomotion. Methods We adapt this model to describe and simulate an amputee walking with a powered prosthesis using the proposed control, and evaluate the gait robustness when confronted with rough ground and swing leg disturbances. We then implement and partially evaluate the resulting controller on a leg prosthesis prototype worn by a non-amputee user. Results In simulation, the proposed prosthesis control leads to gaits that are more robust than those obtained by the impedance control method. The initial hardware experiments with the prosthesis prototype show that the proposed control reproduces normal walking patterns qualitatively and effectively responds to disturbances in early and late swing. However, the response to mid-swing disturbances neither replicates human responses nor averts falls. Conclusions The neuromuscular model control is a promising alternative to existing prosthesis controls, although further research will need to improve on the initial implementation and determine how well these results transfer to amputee gait. Significance This work provides a potential avenue for future development of control policies that help improve amputee balance recovery. PMID:26315935

Focal vibration of quadriceps muscle enhances leg power and decreases knee joint laxity in female volleyball players.

PubMed

Brunetti, O; Botti, F M; Roscini, M; Brunetti, A; Panichi, R; Filippi, G M; Biscarini, A; Pettorossi, V E

2012-12-01

This double-blind randomized controlled study aims at determining the effect of repeated muscle vibration (rMV) on explosive and reactive leg power and on knee laxity of female volleyball players. Eighteen voluntary volleyball athletes, belonging to the same senior regional level team (age=22.7 ± 3 years, height=180.3 ± 5 cm, mass= 64 ± 4 kg) were assigned to three groups (N.=6) for vibration on contracted quadriceps (VC), vibration on relaxed muscle (VR), and sham vibration (NV), respectively. Intervention consisted in 3 rMV sessions performed in 3 consecutive days. In each session, 100 Hz, 300-500 μm amplitude vibratory stimuli were bilaterally delivered to the quadriceps in three consecutive 10-minutes applications. Explosive and reactive leg power and knee joint laxity were evaluated 1 day before, and 1, 30, and 240 days after intervention. In VC group, explosive and reactive leg power increased respectively by ~16% and ~9% at 1 day, by ~19% and ~11% at 30 days and by ~26% and ~13% at 240 days, concomitantly knee laxity decreased by ~6%, ~15% and ~18% at the same times. These changes were significantly larger than in the other groups, in which leg power increment and knee joint laxity reduction remained close to ~3%, ~5% and ~10% at 1, 30 and 240 days, respectively. Combined bilateral voluntary contraction and rMV of the quadriceps muscles is a short-lasting, non-invasive technique that can significantly and persistently improve muscle performance and knee laxity in volleyball women players.

Relationship between mechanical factors and incidence of low back pain.

PubMed

Nourbakhsh, Mohammad Reza; Arab, Amir Massoud

2002-09-01

A multifactorial cross-sectional nonexperimental design. To collectively investigate the association among 17 mechanical factors and occurrence of low back pain (LBP). Several physical characteristics, based on assumptions, clinical findings, and scientific experiments, have been associated with the development of LBP Controversy exists regarding the degree of association between some of these physical characteristics and LBP. Information regarding the degree of association of each factor to LBP is needed for effective prevention and appropriate treatment strategies. A total of 600 subjects participated in this study. Subjects were categorized into 4 groups: asymptomatic men (n = 150, age [mean +/- SD] = 43 +/- 15 years), asymptomatic women (n = 150, age [mean +/- SD] = 43 +/- 13 years), men with LBP (n = 150, age [mean +/- SD] = 43 +/- 14 years), and women with LBP (n = 150, age [mean +/- SD] = 43 +/- 13 years). Seventeen physical characteristics were measured in each group and the relative association of each characteristic with LBP was assessed. Among all the factors tested, endurance of the back extensor muscles had the highest association with LBP Other factors such as the length of the back extensor muscles, and the strength of the hip flexor, hip adductor, and abdominal muscles also had a significant association with LBP. It appears that muscle endurance and weakness are associated with LBP and that structural factors such as the size of the lumbar lordosis, pelvic tilt, leg length discrepancy, and the length of abdominal, hamstring, and iliopsoas muscles are not associated with the occurrence of LBP.

Hip muscle strength is decreased in middle-aged recreational male athletes with midportion Achilles tendinopathy: A cross-sectional study.

PubMed

Habets, B; Smits, H W; Backx, F J G; van Cingel, R E H; Huisstede, B M A

2017-05-01

Investigating differences in hip muscle strength between athletes with Achilles tendinopathy (AT) and asymptomatic controls. Cross-sectional case-control study. Sports medical center. Twelve recreational male athletes with mid-portion AT and twelve matched asymptomatic controls. Isometric strength of the hip abductors, external rotators, and extensors was measured using a handheld dynamometer. Functional hip muscle performance was evaluated with the single-leg squat. The Victorian Institute of Sport Assessment-Achilles (VISA-A) questionnaire was completed to determine clinical severity of symptoms. Compared to controls, participants with AT demonstrated 28.9% less isometric hip abduction strength (p = 0.012), 34.2% less hip external rotation strength (p = 0.010), and 28.3% less hip extension strength (p = 0.034) in the injured limb. Similar differences were found for the non-injured limb (26.7-41.8%; p < 0.03). No significant differences were found in functional hip muscle performance between the injured and non-injured limb or between the groups, and no significant correlation was found between hip muscle strength and VISA-A scores. Recreational male athletes with chronic mid-portion AT demonstrated bilateral weakness of hip abductors, external rotators, and extensors compared to their asymptomatic counterparts. These findings suggest that hip muscle strength may be important in the assessment and rehabilitation of those with AT. Copyright © 2016 Elsevier Ltd. All rights reserved.

Baseline Mechanical and Neuromuscular Profile of Knee Extensor and Flexor Muscles in Professional Soccer Players at the Start of the Pre-Season

PubMed Central

García-García, Oscar; Serrano-Gómez, Virginia; Hernández-Mendo, Antonio; Morales-Sánchez, Verónica

2017-01-01

Abstract The aim of the study was to determine the mechanical and neuromuscular profile of knee extensor and flexor muscles in professional soccer players at the start of the pre-season, and to calculate percentages for symmetry, as well as examine differences according to the player’s positional role. The vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF) and biceps femoris (BF) of 16 professional soccer players were evaluated by means of tensiomyography (TMG) on the first day of the pre-season. A paired-samples t test (p < .05) was used to compare the dominant and non-dominant lower limb. One-way ANOVA was applied, with the positional role as an independent factor. No differences were observed between the dominant and non-dominant leg. The highest degree of symmetry corresponded to the VM (92.5 ± 2.7%), and the lowest to the BF (80.7 ± 10.9%). The positional role was associated with significant differences in some of the variables for the BF, RF and VM, although only the half-relaxation time in the BF and the time to sustain force in the VM differed across all the playing positions considered. TMG was shown to be a useful way of evaluating the neuromuscular characteristics of soccer players at the start of the pre-season, and of establishing baseline values for individual players. PMID:28828075

Effect of resistance exercise training combined with relatively low vascular occlusion.

PubMed

Sumide, Takahiro; Sakuraba, Keishoku; Sawaki, Keisuke; Ohmura, Hirotoshi; Tamura, Yoshifumi

2009-01-01

Previous studies have demonstrated that a low-intensity resistance exercise, combined with vascular occlusion, results in a marked increase in muscular size and strength. We investigated the optimal pressure for reduction of muscle blood flow with resistance exercise to increase the muscular strength and endurance. Twenty-one subjects were randomly divided into four groups by the different application of vascular occlusion pressure at the proximal of thigh: without any pressure (0-pressure group), with a pressure of 50mmHg (50-pressure group), with a pressure of 150mmHg (150-pressure group), and with a pressure of 250mmHg (250-pressure group). The isokinetic muscle strength at angular velocities of 60 and 180 degrees /s, total muscle work, and the cross-sectional knee extensor muscle area were assessed before and after exercise. Exercise was performed three times a week over an 8-week period at an intensity of approximately 20% of one-repetition maximum for straight leg raising and hip joint adduction and maximum force for abduction training. A significant increase in strength at 180 degrees /s was noted after exercise in all subjects who exercised under vascular occlusion. Total muscle work increased significantly in the 50- and 150-pressure groups (P<0.05, P<0.01, respectively). There was no significant increase in cross-sectional knee extensor muscle area in any groups. In conclusion, resistance exercise with relatively low vascular occlusion pressure is potentially useful to increase muscle strength and endurance without discomfort.

Walking and Running Require Greater Effort from the Ankle than the Knee Extensor Muscles.

PubMed

Kulmala, Juha-Pekka; Korhonen, Marko T; Ruggiero, Luca; Kuitunen, Sami; Suominen, Harri; Heinonen, Ari; Mikkola, Aki; Avela, Janne

2016-11-01

The knee and ankle extensors as human primary antigravity muscle groups are of utmost importance in a wide range of locomotor activities. Yet, we know surprisingly little about how these muscle groups work, and specifically, how close to their maximal capacities they function across different modes and intensity of locomotion. Therefore, to advance our understanding of locomotor constraints, we determined and compared relative operating efforts of the knee and ankle extensors during walking, running, and sprinting. Using an inverse dynamics biomechanical analysis, the muscle forces of the knee and ankle extensors during walking (1.6 m·s), running (4.1 m·s), and sprinting (9.3 m·s) were quantified and then related to maximum forces of the same muscle groups obtained from a reference hopping test that permitted natural elastic limb behavior. During walking, the relative effort of the ankle extensors was almost two times greater compared with the knee extensors (35% ± 6% vs 19% ± 5%, P < 0.001). Changing walking to running decreased the difference in the relative effort between the extensor muscle groups, but still, the ankle extensors operated at a 25% greater level than the knee extensors (84% ± 12% vs 63% ± 17%, P < 0.05). At top speed sprinting, the ankle extensors reached their maximum operating level, whereas the knee extensors still worked well below their limits, showing a 25% lower relative effort compared with the ankle extensors (96% ± 11% vs 72% ± 19%, P < 0.01). Regardless of the mode of locomotion, humans operate at a much greater relative effort at the ankle than knee extensor muscles. As a consequence, the great demand on ankle extensors may be a key biomechanical factor limiting our locomotor ability and influencing the way we locomote and adapt to accommodate compromised neuromuscular system function.

Sex difference in the heat shock response to high external load resistance training in older humans.

PubMed

Njemini, Rose; Forti, Louis Nuvagah; Mets, Tony; Van Roie, Evelien; Coudyzer, Walter; Beyer, Ingo; Delecluse, Christophe; Bautmans, Ivan

2017-07-01

Literature reports on the effects of resistance training on heat shock protein70 (Hsp70) adaptation in older subjects are scarce. Moreover, the optimum training load required to obtain a beneficial adaptation profile is lacking. Therefore, the aim of this study was to determine the effects of resistance training at various external loads on extracellular Hsp70 (eHsp70) resting levels in older humans. Fifty-six community-dwelling older (68±5years) volunteers were randomized to 12weeks of resistance training (3×/week) at either high-resistance (HIGH, 8 males, 10 females, 2×10-15 repetitions at 80% 1RM), low resistance (LOW, 9 Males, 10 Females, 1×80-100 repetitions at 20% 1RM), or mixed low resistance (LOW+, 9 Males, 10 Females, 1×60 repetitions at 20% 1RM followed by 1×10-20 repetitions at 40% 1RM). Serum was available from 48 out of the 56 participants at baseline and after 12weeks for determination of eHsp70. Mid-thigh muscle volume (computed tomography), muscle strength (1RM & Biodex dynamometer) and physical functioning (including 6min walk distance [6MWD]) were assessed. There was a sex-related dichotomy in the heat shock response to high external load training. We observed a significant decrease in eHsp70 concentration in the HIGH group for female, but not male, subjects. At baseline, men had a larger muscle volume, leg press and leg extension 1RM compared to women (all p<0.001). Also, the 6MWD was significantly higher in men compared to women at baseline. However, this difference disappeared when correcting for height. Moreover, the overall functional performance and physical activity scores were similar in men and women. None of the participants' characteristics nor any of the outcome variables differed between groups at baseline. There was a significant increase in the strength and physical performance parameters in both men and women post-exercise (all p<0.05). Females in the HIGH group clearly demonstrated a larger gain in leg press 1RM and the isometric knee extensor strength compared to females in the LOW group (p=0.036 and p=0.044, respectively). More so, we found an inverse association between the change in eHsp70 levels and improvement in isometric knee extensor strength and 6MWD (r=-0.443, p=0.002 and r=-0.428, p=0.002; respectively) post exercise. Our results show that resistance training at high external load decreases the resting levels of eHsp70 in older females. Whether this reflects a better health status requires further investigation. Copyright © 2017 Elsevier Inc. All rights reserved.

Transfer of extensor carpi radialis brevis as an extensor to extensor motor transfer (EEMT) in ulnar nerve palsy.

PubMed

Jamali, Allah Rakha; Bhatti, Anisuddin; Mehboob, Ghulam

2006-07-01

To evaluate functional outcome and correction of deformity with extensor carpiradialis brevis motor transfer to replace the intrinsic muscles as an extensor to extensor motor transfer (EEMT). This was a prospective observational study with one group pretest posttest design conducted from 1996 to 2004. Convenience sampling technique was used and the sample size was twenty one. The independent variable was transfer of extensor carpiradialis brevis to replace the intrinsic muscles. The dependent variable was functional outcome and the correction of deformity. The extraneous variables were age, sex interval between injury and transfer as well as local factors related to wound and grafts used. The average follow up was 22.5 months. The mean preoperative unassisted extensor lag was 56.79 +/- 10.39 which improved to 9.6% +/- 5.4 (correction of 83%) at six months after surgery. With open hand assessment 76.19% reported good to excellent results, while 79.89% achieved good to excellent results with closed hand assessment. The mechanism of closing was good to excellent in 89.42% cases, however only 71.42% patients considered their hands good to excellent. Significant problems were seen with use of tendoachilles as a graft. Extensor carpiradialis brevis transfer to replace the intrinsic muscles as an extensor to extensor motor transfer can achieve good functional outcome as well as correction of deformity despite shortcomings in physical rehabilitation.

Measurement and simulation of thermoelectric efficiency for single leg

NASA Astrophysics Data System (ADS)

Hu, Xiaokai; Yamamoto, Atsushi; Ohta, Michihiro; Nishiate, Hirotaka

2015-04-01

Thermoelectric efficiency measurements were carried out on n-type bismuth telluride legs with the hot-side temperature at 100 and 150 °C. The electric power and heat flow were measured individually. Water coolant was utilized to maintain the cold-side temperature and to measure heat flow out of the cold side. Leg length and vacuum pressure were studied in terms of temperature difference across the leg, open-circuit voltage, internal resistance, and heat flow. Finite-element simulation on thermoelectric generation was performed in COMSOL Multiphysics, by inputting two-side temperatures and thermoelectric material properties. The open-circuit voltage and resistance were in good agreement between the measurement and simulation. Much larger heat flows were found in measurements, since they were comprised of conductive, convective, and radiative contributions. Parasitic heat flow was measured in the absence of bismuth telluride leg, and the conductive heat flow was then available. Finally, the maximum thermoelectric efficiency was derived in accordance with the electric power and the conductive heat flow.

Triple voltage dc-to-dc converter and method

DOEpatents

Su, Gui-Jia

2008-08-05

A circuit and method of providing three dc voltage buses and transforming power between a low voltage dc converter and a high voltage dc converter, by coupling a primary dc power circuit and a secondary dc power circuit through an isolation transformer; providing the gating signals to power semiconductor switches in the primary and secondary circuits to control power flow between the primary and secondary circuits and by controlling a phase shift between the primary voltage and the secondary voltage. The primary dc power circuit and the secondary dc power circuit each further comprising at least two tank capacitances arranged in series as a tank leg, at least two resonant switching devices arranged in series with each other and arranged in parallel with the tank leg, and at least one voltage source arranged in parallel with the tank leg and the resonant switching devices, said resonant switching devices including power semiconductor switches that are operated by gating signals. Additional embodiments having a center-tapped battery on the low voltage side and a plurality of modules on both the low voltage side and the high voltage side are also disclosed for the purpose of reducing ripple current and for reducing the size of the components.

Ankle and knee kinetics between strike patterns at common training speeds in competitive male runners.

PubMed

Kuhman, Daniel; Melcher, Daniel; Paquette, Max R

2016-01-01

The purpose of this study was to investigate the interaction of foot strike and common speeds on sagittal plane ankle and knee joint kinetics in competitive rear foot strike (RFS) runners when running with a RFS pattern and an imposed forefoot strike (FFS) pattern. Sixteen competitive habitual male RFS runners ran at two different speeds (i.e. 8 and 6 min mile(-1)) using their habitual RFS and an imposed FFS pattern. A repeated measures analysis of variance was used to assess a potential interaction between strike pattern and speed for selected ground reaction force (GRF) variables and, sagittal plane ankle and knee kinematic and kinetic variables. No foot strike and speed interaction was observed for any of the kinetic variables. Habitual RFS yielded a greater loading rate of the vertical GRF, peak ankle dorsiflexor moment, peak knee extensor moment, peak knee eccentric extensor power, peak dorsiflexion and sagittal plane knee range of motion compared to imposed FFS. Imposed FFS yielded greater maximum vertical GRF, peak ankle plantarflexor moment, peak ankle eccentric plantarflexor power and sagittal plane ankle ROM compared to habitual RFS. Consistent with previous literature, imposed FFS in habitual RFS reduces eccentric knee extensor and ankle dorsiflexor involvement but produce greater eccentric ankle plantarflexor action compared to RFS. These acute differences between strike patterns were independent of running speeds equivalent to typical easy and hard training runs in competitive male runners. Current findings along with previous literature suggest differences in lower extremity kinetics between habitual RFS and imposed FFS running are consistent among a variety of runner populations.

Monocoque structure for the SKITTER three-legged walker

NASA Technical Reports Server (NTRS)

Bansek, Robert N.; Booth, Andrew J.; Daneman, Steven A.; Dresser, James A.; Haney, Todd G.; Johnson, Gregory R.; Lindzen, Eric C.; Montgomery, Robert C.; Warren, Andrew L.

1988-01-01

The SKITTER 2 design is a monocoque version of the proposed lunar three-legged walker. By the definition of monocoque, the body and legs are a shell with no internal ribbing or supports added for absorbing stresses. The purpose of the monocoque is to encase the elements used for power transmission, power supply, and control of the motion. The material for the structure is a vinyl ester resin, Derakane 8084. This material is easily formable and locally obtainable. The body consists of a hexagonally shaped cylinder with truncated hexagonal pyramids on the top and botton. The legs are eight inch diameter cylinders. The legs are comprised of a tibia section and a femur section. The SKITTER 2 is powered by six actuators which provide linear forces that are transformed into rotary torques by a series of chains and sprockets. The joints connect the femur to the body and the tibia to the femur. Surrounding the joints are flexible rubber hoses that fully encase the chains and sprockets. The SKITTER 2 is capable of walking upside down, righting itself after being overturned, and has the ability to perform in many environments. Applications for this walker include lunar transport or drilling, undersea exploration, and operation in severe surroundings such as arctic temperatures or high radiation.

Monocoque structure for the SKITTER three-legged walker

NASA Astrophysics Data System (ADS)

Bansek, Robert N.; Booth, Andrew J.; Daneman, Steven A.; Dresser, James A.; Haney, Todd G.; Johnson, Gregory R.; Lindzen, Eric C.; Montgomery, Robert C.; Warren, Andrew L.

1988-06-01

The SKITTER 2 design is a monocoque version of the proposed lunar three-legged walker. By the definition of monocoque, the body and legs are a shell with no internal ribbing or supports added for absorbing stresses. The purpose of the monocoque is to encase the elements used for power transmission, power supply, and control of the motion. The material for the structure is a vinyl ester resin, Derakane 8084. This material is easily formable and locally obtainable. The body consists of a hexagonally shaped cylinder with truncated hexagonal pyramids on the top and botton. The legs are eight inch diameter cylinders. The legs are comprised of a tibia section and a femur section. The SKITTER 2 is powered by six actuators which provide linear forces that are transformed into rotary torques by a series of chains and sprockets. The joints connect the femur to the body and the tibia to the femur. Surrounding the joints are flexible rubber hoses that fully encase the chains and sprockets. The SKITTER 2 is capable of walking upside down, righting itself after being overturned, and has the ability to perform in many environments. Applications for this walker include lunar transport or drilling, undersea exploration, and operation in severe surroundings such as arctic temperatures or high radiation.

Prosthetic leg powered by MR brake and SMA wires

NASA Astrophysics Data System (ADS)

Nguyen, The; Munguia, Vicente; Calderon, Jose

2014-04-01

Current knee designs for prosthetic legs rely on electric motors for both moving and stationary states. The electric motors draw an especially high level of current to sustain a fixed position. The advantage of using magnetorheological (MR) fluid is that it requires less current and can have a variable braking torque. Besides, the proposed prosthetic leg is actuated by NiTinol wire, a popular shape memory alloy (SMA). The incorporation of NiTinol gives the leg more realistic weight distribution with appropriate arrangement of the batteries and wires. The prosthesis in this research was designed with MR brake as stopping component and SMA wire network as actuating component at the knee. The MR brake was designed with novel non-circular shape for the rotor that improved the braking torque while minimizing the power consumption. The design also helped simplify the control of braking process. The SMA wire network was design so that the knee motion was actively rotated in both directions. The SMA wires were arranged and played very similar role as the leg's muscles. The study started with the overall solid design of the knee including both MR and SMA parts. Theoretical models were derived and programmed in Simulink for both components. The simulation was capable of predicting the power required for moving the leg or hold it in a fixed position for a certain amount of time. Subsequently, the design was prototyped and tested to validate the theoretical prediction. The theoretical models were updated accordingly to correlate with the experimental data.

Lower-extremity biomechanics during forward and lateral stepping activities in older adults

PubMed Central

Wang, Man-Ying; Flanagan, Sean; Song, Joo-Eun; Greendale, Gail A.; Salem, George J.

2012-01-01

Objective To characterize the lower-extremity biomechanics associated with stepping activities in older adults. Design Repeated-measures comparison of kinematics and kinetics associated with forward step-up and lateral step-up activities. Background Biomechanical analysis may be used to assess the effectiveness of various ‘in-home activities’ in targeting appropriate muscle groups and preserving functional strength and power in elders. Methods Data were analyzed from 21 participants (mean 74.7 yr (standard deviation, 4.4 yr)) who performed the forward and lateral step-up activities while instrumented for biomechanical analysis. Motion analysis equipment, inverse dynamics equations, and repeated measures anovas were used to contrast the maximum joint angles, peak net joint moments, angular impulse, work, and power associated with the activities. Results The lateral step-up resulted in greater maximum knee flexion (P < 0.001) and ankle dorsiflexion angles (P < 0.01). Peak joint moments were similar between exercises. The forward step-up generated greater peak hip power (P < 0.05) and total work (P < 0.001); whereas, the lateral step-up generated greater impulse (P < 0.05), work (P < 0.01), and power (P < 0.05) at the knee and ankle. Conclusions In older adults, the forward step-up places greater demand on the hip extensors, while lateral step-up places greater demand on the knee extensors and ankle plantar flexors. PMID:12620784

FD115 (Flight Day 115) SPRINT leg muscle self scan

NASA Image and Video Library

2011-10-03

ISS029-E-025280 (3 Oct. 2011) --- NASA astronaut Mike Fossum, Expedition 29 commander, performs a SPRINT leg muscle self scan in the Columbus laboratory of the International Space Station. Fossum powered on the Ultrasound 2 (USND-2) unit and Video Power Converter (VPC) hardware, and connected the VPC to Human Research Facility 1 (HRF-1) in order to perform this activity.

FD115 (Flight Day 115) SPRINT leg muscle self scan

NASA Image and Video Library

2011-10-03

ISS029-E-025270 (3 Oct. 2011) --- NASA astronaut Mike Fossum, Expedition 29 commander, performs a SPRINT leg muscle self scan in the Columbus laboratory of the International Space Station. Fossum powered on the Ultrasound 2 (USND-2) unit and Video Power Converter (VPC) hardware, and connected the VPC to Human Research Facility 1 (HRF-1) in order to perform this activity.

Contribution of Knee Flexor and Extensor Strength on Sex-Specific Energy Absorption and Torsional Joint Stiffness During Drop Jumping

PubMed Central

Schmitz, Randy J.; Shultz, Sandra J.

2010-01-01

Abstract Context: Lower extremity injury often occurs during abrupt deceleration when attempting to change the body's direction. Although sex-specific biomechanics have been implicated in the greater risk of acute knee injury in women than in men, it is unknown if sex differences in thigh strength affect sex-specific energy absorption and torsional joint stiffness patterns. Objective: To determine sex differences in energy absorption patterns and joint stiffnesses of the lower extremity during a drop jump and to determine if these sex differences were predicted by knee extensor and flexor strength. Design: Cross-sectional study. Setting: Laboratory environment. Patients or Other Participants: Recreationally active, college-aged students (41 women: age  =  22.1 ± 2.9 years, height  =  1.63 ± 0.07 m, mass  =  59.3 ± 8.0 kg; 40 men: age  =  22.4 ± 2.8 years, height  =  1.77 ± 0.1 m, mass  =  80.9 ± 14.1 kg). Intervention(s): Participants performed knee flexor and extensor maximal voluntary isometric contractions followed by double-leg drop-jump landings. Main Outcome Measure(s): Lower extremity joint energetics (J × N−1 × m−1) and torsional joint stiffnesses (Nm × N−1 × m−1 × degrees−1) were calculated for the hip, knee, and ankle during the initial landing phase. Body weight was measured in newtons and height was measured in meters. Sex comparisons were made and sex-specific regressions determined if thigh muscle strength (Nm/kg) predicted sagittal-plane landing energetics and stiffnesses. Results: Women absorbed 69% more knee energy and had 36% less hip torsional stiffness than men. In women, greater knee extensor strength predicted greater knee energy absorption (R2  =  0.11, P  =  .04), and greater knee flexor strength predicted greater hip torsional stiffness (R2  =  0.12, P  =  .03). Conclusions: Sex-specific biomechanics during the deceleration phase of a drop jump revealed that women used a strategy to attempt to decrease system stiffness. Additionally, only female strength values were predictive of landing energetics and stiffnesses. These findings collectively demonstrated that the task may have been more difficult for women, resulting in a different movement strategy among those with different levels of thigh strength to safely complete the task. Future researchers should look at other predictive factors of observed sex differences. PMID:20831388

Tendon length and joint flexibility are related to running economy.

PubMed

Hunter, Gary R; Katsoulis, Konstantina; McCarthy, John P; Ogard, William K; Bamman, Marcas M; Wood, David S; Den Hollander, Jan A; Blaudeau, Tamilane E; Newcomer, Bradley R

2011-08-01

The purpose of study was to determine whether quadriceps/patella and Achilles tendon length and flexibility of the knee extensors and plantar flexors are related to walking and running economy. Twenty-one male distance runners were subjects. Quadriceps/patella and Achilles tendon length were measured by magnetic resonance imaging; body composition was measured DXA; oxygen uptake at rest while seated, walking (3 mph), and running (6 and 7 mph) were measured by indirect calorimetry; knee and ankle joint flexibility were measured by goniometry; and leg lengths were measured by anthropometry while seated. Correlations were used to identify relationships between variables of interest. Net VO2 (exercise VO2 - rest VO2) for walking (NVOWK) and running at 6 and 7 mph (NVO6 and NVO7, respectively) was significantly related to Achilles tendon length (r varying from -0.40 to -0.51, P all < 0.04). Achilles tendon cross section was not related to walking or running economy. Quadriceps/patella tendon length was significantly related to NVO7 (r = -0.43, P = 0.03) and approached significance for NVO6 (r = -0.36, P = 0.06). Flexibility of the plantar flexors was related to NVO7 (+0.38, P = 0.05). Multiple regression showed that Achilles tendon length was independently related to NVO6 and NVO7 (partial r varying from -0.53 to -0.64, all P < 0.02) independent of lower leg length, upper leg length, quadriceps/patella tendon length, knee extension flexibility, or plantarflexion flexibility. These data support the premise that longer lower limb tendons (especially Achilles tendon) and less flexible lower limb joints are associated with improved running economy.

Profiles of muscularity in junior Olympic weight lifters.

PubMed

Kanehisa, H; Funato, K; Abe, T; Fukunaga, T

2005-03-01

This study aimed to investigate the muscularity of strength-trained junior athletes. Muscle thickness (Mt) values at 10 sites (anterior forearm, anterior upper arm, posterior upper arm, chest, abdomen, back, anterior thigh, posterior thigh, anterior lower leg, and posterior lower leg) were determined in junior Olympic weight lifters (OWL, n=7, 15.1+/-0.3 y, mean+/-SD) and non-athletes (CON, n=13, 15.1+/-0.3 y) using a brightness mode ultrasonography. Skeletal age assessed with the Tanner-Whitehouse II method (20 hand-wrist bones) was similar in OWL (16.4+/-0.7 y) and CON (16.3+/-0.6 y). At the 6 sites (anterior forearm, anterior upper arm, posterior upper arm, chest, back and anterior thigh), OWL showed significantly greater Mt values than CON even in terms of Mt relative to body mass(1/3) Mt x BM(-1/3). On the other hand, there were no significant differences between the 2 groups in the Mt ratios of the anterior to posterior site in the upper arm, thigh and lower leg and those of the back to either the chest or abdomen in the trunk. For OWL only, skeletal age was significantly correlated to Mt x BM(-1/3) at the abdomen (r=0.869, p<0.05) and anterior thigh (r=0.883, p<0.05). The findings here indicate that 1) as compared to adolescent non-athletes, junior Olympic weight lifters show a greater muscularity in the upper body and anterior thigh without predominant development in either of anterior and posterior sites within the same body segment, 2) for junior Olympic weight lifters, the muscularity of abdominal and knee extensor muscles is influenced by the biological maturation.

Swing- and support-related muscle actions differentially trigger human walk-run and run-walk transitions.

PubMed

Prilutsky, B I; Gregor, R J

2001-07-01

There has been no consistent explanation as to why humans prefer changing their gait from walking to running and from running to walking at increasing and decreasing speeds, respectively. This study examined muscle activation as a possible determinant of these gait transitions. Seven subjects walked and ran on a motor-driven treadmill for 40s at speeds of 55, 70, 85, 100, 115, 130 and 145% of the preferred transition speed. The movements of subjects were videotaped, and surface electromyographic activity was recorded from seven major leg muscles. Resultant moments at the leg joints during the swing phase were calculated. During the swing phase of locomotion at preferred running speeds (115, 130, 145%), swing-related activation of the ankle, knee and hip flexors and peaks of flexion moments were typically lower (P<0.05) during running than during walking. At preferred walking speeds (55, 70, 85%), support-related activation of the ankle and knee extensors was typically lower during stance of walking than during stance of running (P<0.05). These results support the hypothesis that the preferred walk-run transition might be triggered by the increased sense of effort due to the exaggerated swing-related activation of the tibialis anterior, rectus femoris and hamstrings; this increased activation is necessary to meet the higher joint moment demands to move the swing leg during fast walking. The preferred run-walk transition might be similarly triggered by the sense of effort due to the higher support-related activation of the soleus, gastrocnemius and vastii that must generate higher forces during slow running than during walking at the same speed.

Static stretching vs. dynamic warm-ups: a comparison of their effects on torque and electromyography output of the quadriceps and hamstring muscles.

PubMed

Williams, N; Coburn, J; Gillum, T

2015-11-01

The aim of this paper was to determine if two different warm-up protocols differently affect torque of the quadriceps and hamstrings, and electromyography (EMG) output of the rectus femoris (RF) and vastus lateralis (VL) when completing 30 maximal leg extensions and curls. Twenty-one healthy male (N.=8) and female (N.=13) subjects volunteered to participate in a familiarization session and three testing sessions. The three testing sessions control, dynamic, and static were completed in a counterbalanced order on non-consecutive days. First, subjects warmed-up on a treadmill for five minutes before completing six dynamic movements, six static-stretches, or no stretches. They then rested for five minutes before completing 30 maximal leg extensions and curls at a speed of 60 s-1. A significant decrease in quadriceps torque output over time was determined for the dynamic protocol when compared to the control (P<0.01) and static (P<0.05) protocols. A significant decrease was found in peak quadriceps torque for the dynamic protocol (P<0.01) when compared to the static, and a significant increase was found for the static protocol (P<0.05) when compared to the control. A significant decrease in average quadriceps torque was found for the dynamic protocol when compared to the static (P<0.05) and control (P<0.01) protocols. No difference was found in hamstring torque or EMG output of the RF and VL. Short duration static-stretching has the ability to increase peak and average torque of the leg extensors, while some types of anaerobic exercise involving maximal contractions to fatigue may be hindered by performing dynamic movements as part of the warm-up.

Impaired Skeletal Muscle Vasodilation during Exercise in Heart Failure with Preserved Ejection Fraction

PubMed Central

Lee, Joshua F.; Barrett-O’Keefe, Zachary; Nelson, Ashley D.; Garten, Ryan S.; Ryan, John J.; Nativi-Nicolau, Jose N.; Richardson, Russell S.; Wray, D. Walter

2016-01-01

Background Exercise intolerance is a hallmark symptom of heart failure patients with preserved ejection fraction (HFpEF), which may be related to an impaired ability to appropriately increase blood flow to the exercising muscle. Methods We evaluated leg blood flow (LBF, ultrasound Doppler), heart rate (HR), stroke volume (SV), cardiac output (CO), and mean arterial blood pressure (MAP, photoplethysmography) during dynamic, single leg knee-extensor (KE) exercise in HFpEF patients (n = 21; 68 ± 2 yrs) and healthy controls (n = 20; 71 ± 2 yrs). Results HFpEF patients exhibited a marked attrition during KE exercise, with only 60% able to complete the exercise protocol. In participants who completed all exercise intensities (0-5-10-15W; HFpEF, n = 13; Controls, n = 16), LBF was not different at 0W and 5W, but was 15-25% lower in HFpEF compared to controls at 10W and 15W (P < 0.001). Likewise, leg vascular conductance (LVC), an index of vasodilation, was not different at 0W and 5W, but was 15-20% lower in HFpEF compared to controls at 10W and 15W (P < 0.05). In contrast to these peripheral deficits, exercise-induced changes in central variables (HR, SV, CO), as well as MAP, were similar between groups. Conclusions These data reveal a marked reduction in LBF and LVC in HFpEF patients during exercise that cannot be attributed to a disease-related alteration in central hemodynamics, suggesting that impaired vasodilation in the exercising skeletal muscle vasculature may play a key role in the exercise intolerance associated with this patient population. PMID:26970959

Reliability, Validity, and Minimal Detectable Change of Four-Step Stair Climb Power Test in Community-Dwelling Older Adults.

PubMed

Ni, Meng; Brown, Lorna G; Lawler, Danielle; Bean, Jonathan F

2017-07-01

Stair climb power is an important clinical measure of lower-extremity power. The stair climb power test (SCPT) was validated by requiring individuals to climb a full flight of stairs. A 4-step SCPT (4SCPT) would be more clinically feasible and easier to perform, yet its reliability and validity are unknown. To evaluate reliability, validity, and minimal detectable change of 4SCPT among community-dwelling older adults. This study is a cross-sectional analysis of baseline data from a clinical trial. Fifty older adults ≥65 years of age, at risk for mobility decline, consented to participate in this ancillary study. Test-retest reliability was derived from 2 measurements within each participant measured by a single assessor. Pearson correlation analyses among leg power measures (4SCPT, SCPT, single leg press power at 40% and 70% of the 1-repetition maximum [SLP40, SLP70]) were performed. Separate multivariate linear regressions were conducted evaluating the associations between each leg power measure and 2 mobility outcomes, the Short Physical Performance Battery (SPPB) and habitual gait speed (HGS). Minimal detectable change was based on a 90% confidence interval (MDC 90 ). The 4SCPT had excellent test-retest reliability (ICC(2,1) = 0.951), and strong correlation with SCPT, SLP40, and SLP70 ( r = 0.85-0.96). The 4SCPT explained a greater amount of variance in the SPPB (R 2 = 0.31) than other leg power measurements (R 2 = 0.23-0.25). The 4SCPT (R 2 = 0.41) and SCPT (R 2 = 0.42) described equivalent amounts of variance in HGS, and greater than that with SLP40 (R 2 = 0.28) and SLP70 (R 2 = 0.30). The MDC 90 for 4SCPT was 44.0 watts. This was a cross-sectional analysis within a small, nonrepresentative sample. Interrater reliability was not evaluated. The 4SCPT shows scientific promise as a valid and reliable leg power measurement among community-dwelling older adults. © 2017 American Physical Therapy Association

[Reconstruction of the extensor pollicis longus tendon by transposition of the extensor indicis tendon].

PubMed

Loos, A; Kalb, K; Van Schoonhoven, J; Landsleitner Dagger, B

2003-12-01

Rupture of the extensor pollicis longus-tendon (EPL) is a frequent complication after distal radius fractures. Other traumatic and non-traumatic reasons for this tendon lesion are known, including a theory about a disorder in the blood supply to the tendon itself. We examined 40 patients after reconstruction of the EPL-tendon in a mean follow-up time of 30 months. All patients were clinically examined and a DASH questionnaire was answered by all patients. The method to reconstruct the EPL-tendon was the transposition of the extensor indicis-tendon. After the operations the thumb was put in a splint for four weeks in a "hitch-hiker's-position". 31 ruptures of the tendon (77.5 %) were a result of trauma. In 20 of them (50 %) a distal radius fracture had occurred. Clinical examination included measurements of the movement of the thumb- and index-finger joints, the grip strength and the maximal span of the hand. Significant differences were not found. The isolated extension of the index finger was possible in all patients. But it was reduced in ten cases which represent 25 %. Our results were evaluated by the Geldmacher score to evaluate the reconstruction of the EPL-tendon. 20 % excellent, 65 % good, 12.5 % fair and 2.5 % poor results were reached. The Geldmacher score was used critically. We suggest its modification for the evaluation of thumb abduction. The DASH score reached a functional value of ten points which represents a very good result. In conclusion the extensor indicis-transposition is a safe method to reconstruct the EPL-tendon. Its substantial advantage is taking a healthy muscle as the motor, thereby avoiding the risk of using a degenerated muscle in late tendon reconstruction. A powerful extension of the index finger will be maintained by physical education. Generally, the loss of the extension of the index finger is negligible. It does not disturb the patients. But it has to be discussed with the patient before the operation.

Isokinetic Evaluation of the Hip Flexor and Extensor Muscles: A Systematic Review.

PubMed

Zapparoli, Fabricio Yuri; Riberto, Marcelo

2017-11-01

Isokinetic dynamometry testing is a safe and reliable method accepted as the "gold standard" in the evaluation of muscle strength in the open kinetic chain. Isokinetic hip examinations face problems in the standardization of the position of the equipment axis, in the individual being examined, and in the adjustment of the lever arm and in stabilization strategies for the patients during the tests. Identification of the methodologic procedures with best reproducibility is also needed. To review the literature to evaluate the parameters used for the isokinetic evaluation of the hip flexor and extensor muscles and its reproducibility. This is a systematic literature review of the Cochrane, LILACS, PEDro, PubMed, and SciELO databases. The inclusion criteria were articles on the evaluation of hip flexor and/or extensor muscular strength with an isokinetic dynamometer and articles that analyzed the ICC or Pearson's reproducibility. The information extracted was positioning of the patient; positioning of the dynamometer axis; positioning of the lever arm; angular speed; sample size, pathology; type of contraction; and ICC and Pearson's results. 204 articles were found, from which 14 were selected that evaluated hip flexor and extensor muscles, involving 550 individuals who were submitted to an isokinetic hip evaluation. Five articles obtained the best result in reproducibility and had their methodology analyzed. To obtain better reproducibility of the isokinetic evaluation of the hip flexor and extensor muscles, the following recommendations must be followed: the individual must be positioned in the supine position and the dynamometer axis must be aligned with the greater trochanter of the femur. The positioning of the lever arm must be in the most distal region of the thigh possible. The angular speed used to analyze torque peak and muscle work was 60°/s, and to evaluate the muscle power it was 180°/s, with concentric and eccentric contractions being analyzed.

Crouch gait can be an effective form of forced-use/no constraint exercise for the paretic lower limb in stroke.

PubMed

Tesio, Luigi; Rota, Viviana; Malloggi, Chiara; Brugliera, Luigia; Catino, Luigi

2017-09-01

In hemiplegic gait the paretic lower limb provides less muscle power and shows a briefer stance compared with the unaffected limb. Yet, a longer stance and a higher power can be obtained from the paretic lower limb if gait speed is increased. This supports the existence of a 'learned non-use' phenomenon, similar to that underlying some asymmetric impairments of the motion of the eyes and of the upper limbs. Crouch gait (CG) (bent-hip bent-knee, about 30° minimum knee flexion) might be an effective form of 'forced-use' treatment of the paretic lower limb. It is not known whether it also stimulates a more symmetric muscle power output. Gait analysis on a force treadmill was carried out in 12 healthy adults and seven hemiplegic patients (1-127 months after stroke, median: 1.6). Speed was imposed at 0.3 m/s. Step length and single and double stance times, sagittal joint rotations, peak positive power, and work in extension of the hip, knee, and ankle (plantar flexion), and surface electromyography (sEMG) area from extensor muscles during the generation of power were measured on either side during both erect and crouch walking. Significance was set at P less than 0.05; corrections for multiplicity were applied. Patients, compared with healthy controls, adopted in both gait modalities and on both sides a shorter step length (61-84%) as well as a shorter stance (76-90%) and swing (63-83%) time. As a rule, they also provided a higher muscular work (median: 137%, range: 77-250%) paralleled by a greater sEMG area (median: 174%, range: 75-185%). In erect gait, the generation of peak extensor power across hip, knee, and ankle joints was in general lower (83-90%) from the paretic limb and higher (98-165%) from the unaffected limb compared with control values. In CG, peak power generation across the three lower limb joints was invariably higher in hemiparetic patients: 107-177% from the paretic limb and 114-231% from the unaffected limb. When gait shifted from erect to crouch, only for hemiplegic patients, at the hip, the paretic/unaffected ratio increased significantly. For peak power, work, sEMG area, and joint rotation, the paretic/unaffected ratio increased from 55 to 85%, 56 to 72%, 68 to 91%, and 67 to 93%, respectively. CG appears to be an effective form of forced-use exercise eliciting more power and work from the paretic lower limb muscles sustained by a greater neural drive. It also seems effective in forcing a more symmetric power and work from the hip extensor muscles, but neither from the knee nor the ankle.

Impact of resistance exercise program on functional capacity and muscular strength of knee extensor in pre-frail community-dwelling older women: a randomized crossover trial.

PubMed

Lustosa, Lygia P; Silva, Juscélio P; Coelho, Fernanda M; Pereira, Daniele S; Parentoni, Adriana N; Pereira, Leani S M

2011-01-01

Frailty syndrome in elderly people is characterized by a reduction of energy reserves and also by a decreased of resistance to stressors, resulting in an increase of vulnerability. The aim of this study was to verify the effect of a muscle-strengthening program with load in pre-frail elder women with regards to the functional capacity, knee extensor muscle strength and their correlation. Thrity-two pre-frail community-dwelling women participated in this study. Potential participants with cognitive impairment (MEEM), lower extremities orthopedic surgery, fractures, inability to walk unaided, neurological diseases, acute inflammatory disease, tumor growth, regular physical activity and current use of immunomodulators were excluded. All partcipants were evaluated by a blinded assessor using: Timed up and go (TUG), 10-Meter Walk Test (10MWT) and knee extensor muscle strength (Byodex System 3 Pro® isokinetic dynamometer at angular speeds of 60 and 180(0)/s). The intervention consisted of strengthening exercises of the lower extremities at 70% of 1RM, three times/ week for ten weeks. The statistical analysis was performed using the ANOVA and Spearman tests After the intervention, it was observed statistical significance on the work at 180(0)/s (F=12.71, p=0.02), on the power at 180(0)/s (F=15.40, p=0.02) and on the functional capacity (TUG, F=9.54, p=0.01; TC10, F=3.80, p=0.01). There was a good negative and statistically significant correlation between the TUG and work at 60(0)/s, such as the TUG and work at 180(0)/s (r=-0.65, p=0.01; r=-0.72, p=0.01). The intervention improved the muscular power and the functional capacity. The increase of the power correlated with function, which is an important variable of the quality of life in the pre-frail elders. Article registered in the ISRCT register under number ISRCTN62824599.

Physiological Interpretation of the Slope during an Isokinetic Fatigue Test.

PubMed

Bosquet, L; Gouadec, K; Berryman, N; Duclos, C; Gremeaux, V; Croisier, J-L

2015-07-01

To assess the relationship between selected measures (the slope and average performance) obtained during a high intensity isokinetic fatigue test of the knee (FAT) and relevant measures of anaerobic and aerobic capacities. 20 well-trained cyclists performed 3 randomly ordered sessions involving a FAT consisting in 30 reciprocal maximal concentric contractions of knee flexors and extensors at 180°.s(-1), a maximal continuous graded exercise test (GXT), and a Wingate anaerobic test (WAnT). The slope calculated from peak torque (PT) and total work (TW) of knee extensors was highly associated to maximal PT (r=-0.86) and maximal TW (r=-0.87) measured during FAT, and moderately associated to peak power output measured during the WAnT (r=-0.64 to -0.71). Average PT and average TW were highly associated to maximal PT (r=0.93) and maximal TW (r=0.96), to mean power output measured during WAnT (r=0.83-0.90) and moderately associated to maximal oxygen uptake (0.58-0.67). In conclusion, the slope is mainly determined by maximal anaerobic power, while average performance is a composite measure depending on both aerobic and anaerobic energy systems according to proportions that are determined by the duration of the test. © Georg Thieme Verlag KG Stuttgart · New York.

[Isokinetic profile of knee flexors and extensors in a population of rugby players].

PubMed

Larrat, E; Kemoun, G; Carette, P; Teffaha, D; Dugue, B

2007-06-01

We aimed to assess the isokinetic profile of the flexor and extensor muscles of the knee within a population of rugby players. This was a descriptive study. The rugby players underwent bilateral isokinetic assessment of knee flexion and extension on a CON-TREX MJ isokinetic dynamometer functioning at four angular frequencies - 90, 120, 180 and 240 degrees/s - in a concentric manner. The isokinetic parameters were peak torque, mean power, and mean work in relation to weight and femoral bicep: quadriceps ratio. The population included 16 "Federal 1" (semi-professional) rugby players with mean age 25 years (range 20-33 years). The players were divided into two groups: "forward" players (props, hookers, second line, third line) and "back" players (scrum, inside, center, wing, tail). The values of the isokinetic parameters did not reveal use of a preferred limb. Consequently, peak torque and mean power were higher in forward players than back players, whereas back players showed a higher relative power throughout the isokinetic test. Among rugby players, forward and back players showed differences in several isokinetic parameters. Accurate knowledge of the equilibrium between the knee's effector muscles is important for stability of the joint, to not only minimize articular accidents but also pinpoint force imbalances, thereby preventing muscular lesions during the sports season.

Role of glucocorticoids in the response of rat leg muscles to reduced activity

NASA Technical Reports Server (NTRS)

Jaspers, Stephen R.; Tischler, Marc E.

1986-01-01

Adrenalectomy did not prevent atrophy of rat soleus muscle during 6 days of tail cast suspension. Cortisol treatment enhanced the atrophy and caused atrophy of the weight-bearing soleus and both extensor digitorum longus (EDL) muscles. Unloading led to increased sarcoplasmic protein concentration in the soleus but cortisol administration increased the myhofibrillar (+stromal) protein concentration in both muscles. Suspension of hindlimbs of adrenalectomized animals led to faster protein degradation, slower sarcoplasmic protein degradation, and faster myofibrillar protein synthesis in the isolated soleus, whereas with cortisol-treated animals, the difference in synthesis of myofibrillar proteins was enhanced and that of sarcoplasmic proteins was abolished. Both soleus and EDL of suspended, cortisol-treated animals showed faster protein degradation. It is unlikely that any elevation in circulating glucocorticoids was solely responsible for atrophy of the soleus in this model, but catabolic amounts of glucocorticoids could alter the response of muscle to unloading.

Lichen planus pemphigoides treated with ustekinumab.

PubMed

Knisley, Raymond R; Petropolis, Angelo A; Mackey, Vernon T

2017-12-01

A 71-year-old woman presented with pink to violaceous, flat-topped, polygonal papules on the volar wrists, extensor elbows, and bilateral lower legs of 3 years' duration. She also had erythematous, violaceous, infiltrated plaques with microvesiculation on the bilateral thighs of several months' duration. She reported pruritus, burning, and discomfort. Her medical history included type 2 diabetes mellitus, hypertension, and asthma with no history of skin rashes. Workup revealed lichen planus pemphigoides (LPP), a rare papulosquamous and vesiculobullous dermatosis that shares features of both lichen planus (LP) and bullous pemphigoid (BP). Despite multiple traditional therapies, her disease continued to progress, further developing mucosal disease. After a review of the literature on LP, BP, and LPP, it was noted that tumor necrosis factor α (TNF-α), along with other cytokines, plays a pivotal role in all 3 diseases. After several conventional systemic therapies failed, we treated our patient with ustekinumab with favorable results.

The Fate of the Iliopsoas Muscle in Long-term Follow-up After Open Reduction With a Medial Approach in Developmental Dysplasia of the Hip. Part 2: Isokinetic Muscle Strength Evaluation.

PubMed

Yilmaz, Serdar; Aksahin, Ertugrul; Ersoz, Murat; Bicimoglu, Ali

2017-09-01

The impact on long-term weakness of hip flexion of complete iliopsoas tenotomy during open reduction of developmental hip dysplasia with a medial approach has not yet been fully clarified. The purpose of this study was to investigate the isokinetic muscle strength (IMS) of hip flexor and extensor muscles in these patients and also to analyze the effect of spontaneous reattachment of the iliopsoas muscle on IMS measurements. The study included 20 patients. Earlier magnetic resonance imaging examination of all the patients revealed spontaneous reattachment of the iliopsoas in 18 (90%) patients. IMS measurements were performed at 60 and 150 degrees/s. The peak torque, total work (TW), average power (AP), work fatigue, and agonist to antagonist muscle ratio of the operated and nonoperated hips were recorded separately for flexors and extensors. The effect of iliopsoas reattachment on IMS was also evaluated. The mean follow-up period was 16.65±2.16 (13 to 20) years. Total work (P=0.013) and average power (P=0.009) of the flexor muscles and work fatigue of the extensor muscles (P=0.030) of the operated hip were significantly decreased when compared with the nonoperated hips at 150 degrees/s. There was no significant difference between the flexor muscles of the operated and nonoperated hips (P<0.05) at 60 degrees/s and extensor muscles (P<0.05) at 150 degrees/s. In addition, patients without reattachment had lower IMS in the operated hips. Flexor muscle strength was decreased in the operated hip against low resistance in long-term follow-up after iliopsoas tenotomy. This may reflect that hip muscle strength was decreased after prolonged activities such as sports. However, in forceful activities flexor muscle strength was retained due to iliopsoas reattachment. On the basis of this study we thought that spontaneous reattachment of the iliopsoas tendon substantially preserves muscle strength. Nonetheless possible efforts should be made to surgically reattach the psoas tendon to preserve strength of the muscle. Therapeutic level IV.

The relationship between leg preference and knee mechanics during sidestepping in collegiate female footballers.

PubMed

Brown, Scott R; Wang, Henry; Dickin, D Clark; Weiss, Kaitlyn J

2014-11-01

This study examined the relationship between leg preference and knee mechanics in females during sidestepping. Three-dimensional data were recorded on 16 female collegiate footballers during a planned 45° sidestep manoeuvre with their preferred and non-preferred kicking leg. Knee kinematics and kinetics during initial contact, weight acceptance, peak push-off, and final push-off phases of sidestepping were analysed in both legs. The preferred leg showed trivial to small increases (ES = 0.19-0.36) in knee flexion angle at initial contact, weight acceptance, and peak push-off, and small increases (ES = 0.21-0.34) in peak power production and peak knee extension velocity. The non-preferred leg showed a trivial increase (ES = 0.10) in knee abduction angle during weight acceptance; small to moderate increases (ES = 0.22-0.64) in knee internal rotation angle at weight acceptance, peak push-off, and final push-off; a small increase (ES = 0.22) in knee abductor moment; and trivial increases (ES = 0.09-0.14) in peak power absorption and peak knee flexion velocity. The results of this study show that differences do exist between the preferred and non-preferred leg in females. The findings of this study will increase the knowledge base of anterior cruciate ligament injury in females and can aid in the design of more appropriate neuromuscular, plyometric, and strength training protocols for injury prevention.

Investigation of the Effects of High-Intensity, Intermittent Exercise and Unanticipation on Trunk and Lower Limb Biomechanics During a Side-Cutting Maneuver Using Statistical Parametric Mapping.

PubMed

Whyte, Enda F; Richter, Chris; OʼConnor, Siobhan; Moran, Kieran A

2018-06-01

Whyte, EF, Richter, C, O'Connor, S, and Moran, KA. Investigation of the effects of high-intensity, intermittent exercise and unanticipation on trunk and lower limb biomechanics during a side-cutting maneuver using statistical parametric mapping. J Strength Cond Res 32(6): 1583-1593, 2018-Anterior cruciate ligament (ACL) injuries frequently occur during side-cutting maneuvers when fatigued or reacting to the sporting environment. Trunk and hip biomechanics are proposed to influence ACL loading during these activities. However, the effects of fatigue and unanticipation on the biomechanics of the kinetic chain may be limited by traditional discrete point analysis. We recruited 28 male, varsity, Gaelic footballers (21.7 ± 2.2 years; 178.7 ± 14.6 m; 81.8 ± 11.4 kg) to perform anticipated and unanticipated side-cutting maneuvers before and after a high-intensity, intermittent exercise protocol (HIIP). Statistical parametric mapping (repeated-measures analysis of varience) identified differences in phases of trunk and stance leg biomechanics during weight acceptance. Unanticipation resulted in less trunk flexion (p < 0.001) and greater side flexion away from the direction of cut (p < 0.001). This led to smaller (internal) knee flexor and greater (internal) knee extensor (p = 0.002-0.007), hip adductor (p = 0.005), and hip external rotator (p = 0.007) moments. The HIIP resulted in increased trunk flexion (p < 0.001) and side flexion away from the direction of cut (p = 0.038), resulting in smaller (internal) knee extensor moments (p = 0.006). One interaction effect was noted demonstrating greater hip extensor moments in the unanticipated condition post-HIIP (p = 0.025). Results demonstrate that unanticipation resulted in trunk kinematics considered an ACL injury risk factor. A subsequent increase in frontal and transverse plane hip loading and sagittal plane knee loading was observed, which may increase ACL strain. Conversely, HIIP-induced trunk kinematic alterations resulted in reduced sagittal plane knee and subsequent ACL loading. Therefore, adequate hip and knee control is important during unanticipated side-cutting maneuvers.

Single-leg hop testing following fatiguing exercise: reliability and biomechanical analysis.

PubMed

Augustsson, J; Thomeé, R; Lindén, C; Folkesson, M; Tranberg, R; Karlsson, J

2006-04-01

A fatiguing exercise protocol was combined with single-leg hop testing to improve the possibilities of evaluating the effects of training or rehabilitation interventions. In the first test-retest experiment, 11 healthy male subjects performed two trials of single-leg hops under three different test conditions: non-fatigued and following fatiguing exercise, which consisted of unilateral weight machine knee extensions at 80% and 50%, respectively, of 1 repetition maximum (1 RM) strength. Intraclass correlation coefficients ranged from 0.75 to 0.98 for different hop test conditions, indicating that all tests were reliable. For the second experiment, eight healthy male subjects performed the fatiguing exercise protocol to investigate how fatigue influences lower-extremity joint kinematics and kinetics during single-leg hops. Hip, knee and ankle joint angles, moments and powers, as well as ground-reaction forces were recorded with a six-camera, motion-capture system and a force platform. Recovery of hop performance following the fatiguing exercise was also measured. During the take-off for the single-leg hops, hip and knee flexion angles, generated powers for the knee and ankle joints, and ground-reaction forces decreased for the fatigued hop conditions compared with the non-fatigued condition (P<0.05). Compared with landing during the non-fatigued condition, hip moments and ground-reaction forces were lower for the fatigued hop conditions (P<0.05). The negative joint power was two to three times greater for the knee than for the hip and five to 10 times greater for the knee than for the ankle during landing for all test conditions (P<0.05). Most measured variables had recovered three minutes post-exercise. It is concluded that the fatiguing exercise protocol combined with single-leg hop testing was a reliable method for investigating functional performance under fatigued test conditions. Further, subjects utilized an adapted hop strategy, which employed less hip and knee flexion and generated powers for the knee and ankle joints during take-off, and less hip joint moments during landing under fatigued conditions. The large negative power values observed at the knee joint during the landing phase of the single-leg hop, during which the quadriceps muscle activates eccentrically, indicate that not only hop distance but also the ability to perform successful landings should be investigated when assessing dynamic knee function.

Deconstructing the power resistance relationship for squats: A joint-level analysis.

PubMed

Farris, D J; Lichtwark, G A; Brown, N A T; Cresswell, A G

2016-07-01

Generating high leg power outputs is important for executing rapid movements. Squats are commonly used to increase leg strength and power. Therefore, it is useful to understand factors affecting power output in squatting. We aimed to deconstruct the mechanisms behind why power is maximized at certain resistances in squatting. Ten male rowers (age = 20 ± 2.2 years; height = 1.82 ± 0.03 m; mass = 86 ± 11 kg) performed maximal power squats with resistances ranging from body weight to 80% of their one repetition maximum (1RM). Three-dimensional kinematics was combined with ground reaction force (GRF) data in an inverse dynamics analysis to calculate leg joint moments and powers. System center of mass (COM) velocity and power were computed from GRF data. COM power was maximized across a range of resistances from 40% to 60% 1RM. This range was identified because a trade-off in hip and knee joint powers existed across this range, with maximal knee joint power occurring at 40% 1RM and maximal hip joint power at 60% 1RM. A non-linear system force-velocity relationship was observed that dictated large reductions in COM power below 20% 1RM and above 60% 1RM. These reductions were due to constraints on the control of the movement. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Runners do not push off the ground but fall forwards via a gravitational torque.

PubMed

Romanov, Nicholas; Fletcher, Graham

2007-09-01

The relationship between the affect and timing of the four forces involved in running (gravity, ground reaction force, muscle force, and potential strain energy) is presented. These forces only increase horizontal acceleration of the centre of mass during stance but not flight. The current hierarchical models of running are critiqued because they do not show gravity, a constant force, in affect during stance. A new gravitational model of running is developed, which shows gravity as the motive force. Gravity is shown to cause a torque as the runner's centre of mass moves forward of the support foot. Ground reaction force is not a motive force but operates according to Newton's third law; therefore, the ground can only propel a runner forward in combination with muscle activity. However, leg and hip extensor muscles have consistently proven to be silent during leg extension (mid-terminal stance). Instead, high muscle-tendon forces at terminal stance suggest elastic recoil regains most of the centre of mass's height. Therefore, the only external motive force from mid-terminal stance is gravity via a gravitational torque, which causes a horizontal displacement. The aim of this paper is to establish a definitive biomechanical technique (Pose method) that is easily taught to runners (Romanov, 2002): falling forwards via a gravitational torque while pulling the support foot rapidly from the ground using the hamstring muscles.

Spinal mobility and trunk muscle strength in elite hockey players.

PubMed

Lindgren, S; Twomey, L

1988-01-01

Elite hockey players of both sexes from the Australian Institute of Sport were assessed for lumbar spine mobility, trunk flexion and back extensor muscle strength, hamstring flexibility and postural characteristics over a two year period. All the athletes were more mobile in rotation than the 'normal' West Australian population, and demonstrated flexible hamstrings and powerful back extensor muscles; trunk flexion was less strong initially, but improved after intervention in the form of a specific exercise programme, over the measurement period. A questionnaire disclosed that low back pain is a common complaint of hockey players, but rarely required intensive physical and medical treatment. The term 'hockey player's back' has been coined in recognition of the long flat thoracolumbar spine frequently noted in these subjects. Copyright © 1988 Australian Physiotherapy Association. Published by . All rights reserved.

Effect of elbow and forearm position on contact pressure between the extensor origin and the lateral side of the capitellum.

PubMed

Tanaka, Yoshitaka; Aoki, Mitsuhiro; Izumi, Tomoki; Wada, Takuro; Fujimiya, Mineko; Yamashita, Toshihiko

2011-01-01

Bone-to-tendon contact in the origin of the common extensor tendons is considered to be one of the causes of lateral epicondylitis. Some factors, including elbow and forearm position, varus stress to the elbow, or contraction of the wrist extensor tendons, are considered to affect this bone-to-tendon contact. However, no studies have evaluated the effect of the elbow and forearm position on bone-tendon interface. The purpose of this study is to evaluate the effect of the position of the elbow and forearm on the contact pressure of the tendinous origin of the common wrist and finger extensors. We used 8 fresh cadaveric upper extremities. Contact pressure between the origin of the common extensor tendons and the lateral side of the capitellum was measured with a pressure sensor and was compared among various conditions, including elbow flexion angle (0°, 30°, 60°, and 90°), forearm rotation position (neutral and 81.5° pronation position), and varus stress load of the elbow (none, gravity on the forearm, and gravity on the forearm +1.96 Nm). Contact pressure was also measured during tension force of the extensor carpi radialis longus, extensor carpi radialis brevis, and extensor digitorum communis by 0, 9.8, and 19.6 N. Contact pressure was significantly increased with the elbow extension position, forearm pronation position, and varus stress to the elbow under tension of the extensor carpi radialis longus or extensor carpi radialis brevis. This study provides data about the amount of contact pressure between bone and tendon at the origin of the common extensor tendons in the elbow. This information may lead to a better understanding of, and better treatment for, lateral epicondylitis. Copyright © 2011. Published by Elsevier Inc.

Real-time optimized biofeedback utilizing sport techniques (ROBUST): a study protocol for a randomized controlled trial.

PubMed

Taylor, Jeffrey B; Nguyen, Anh-Dung; Paterno, Mark V; Huang, Bin; Ford, Kevin R

2017-02-07

Anterior cruciate ligament (ACL) injuries in female athletes lead to a variety of short- and long-term physical, financial, and psychosocial ramifications. While dedicated injury prevention training programs have shown promise, ACL injury rates remain high as implementation has not become widespread. Conventional prevention programs use a combination of resistance, plyometric, balance and agility training to improve high-risk biomechanics and reduce the risk of injury. While many of these programs focus on reducing knee abduction load and posture during dynamic activity, targeting hip extensor strength and utilization may be more efficacious, as it is theorized to be an underlying mechanism of injury in adolescent female athletes. Biofeedback training may complement traditional preventive training, but has not been widely studied in connection with ACL injuries. We hypothesize that biofeedback may be needed to maximize the effectiveness of neuromuscular prophylactic interventions, and that hip-focused biofeedback will improve lower extremity biomechanics to a larger extent than knee-focused biofeedback during dynamic sport-specific tasks and long-term movement strategies. This is an assessor-blind, randomized control trial of 150 adolescent competitive female (9-19 years) soccer players. Each participant receives 3x/week neuromuscular preventive training and 1x/week biofeedback, the mode depending on their randomization to one of 3 biofeedback groups (hip-focused, knee-focused, sham). The primary aim is to assess the impact of biofeedback training on knee abduction moments (the primary biomechanical predictor of future ACL injury) during double-leg landings, single-leg landings, and unplanned cutting. Testing will occur immediately before the training intervention, immediately after the training intervention, and 6 months after the training intervention to assess the long-term retention of modified biomechanics. Secondary aims will assess performance changes, including hip and core strength, power, and agility, and the extent to which maturation effects biofeedback efficacy. The results of the Real-time Optimized Biofeedback Utilizing Sport Techniques (ROBUST) trial will help complement current preventive training and may lead to clinician-friendly methods of biofeedback to incorporate into widespread training practices. Date of publication in ClinicalTrials.gov: 20/04/2016. ClinicalTrials.gov Identifier: NCT02754700 .

Lower extremity joint kinetics and lumbar curvature during squat and stoop lifting

PubMed Central

Hwang, Seonhong; Kim, Youngeun; Kim, Youngho

2009-01-01

Background In this study, kinematics and kinetics of the lower extremity joint and the lumbar lordosis during two different symmetrical lifting techniques(squat and stoop) were examined using the three-dimensional motion analysis. Methods Twenty-six young male volunteers were selected for the subjects in this study. While they lifted boxes weighing 5, 10 and 15 kg by both squat and stoop lifting techniques, their motions were captured and analyzed using the 3D motion analysis system which was synchronized with two forceplates and the electromyographic system. Joint kinematics was determined by the forty-three reflective markers which were attached on the anatomical locations based on the VICON Plug-in-Gait marker placement protocol. Joint kinetics was analyzed by using the inverse dynamics. Paired t-test and Kruskal-Wallis test was used to compare the differences of variables between two techniques, and among three different weights. Correlation coefficient was calculated to explain the role of lower limb joint motion in relation to the lumbar lordosis. Results There were not significant differences in maximum lumbar joint moments between two techniques. The hip and ankle contributed the most part of the support moment during squat lifting, and the knee flexion moment played an important role in stoop lifting. The hip, ankle and lumbar joints generated power and only the knee joint absorbed power in the squat lifting. The knee and ankle joints absorbed power, the hip and lumbar joints generated power in the stoop lifting. The bi-articular antagonist muscles' co-contraction around the knee joint during the squat lifting and the eccentric co-contraction of the gastrocnemius and the biceps femoris were found important for maintaining the straight leg during the stoop lifting. At the time of lordotic curvature appearance in the squat lifting, there were significant correlations in all three lower extremity joint moments with the lumbar joint. Differently, only the hip moment had significant correlation with the lumbar joint in the stoop lifting. Conclusion In conclusion, the knee extension which is prominent kinematics during the squat lifting was produced by the contributions of the kinetic factors from the hip and ankle joints(extensor moment and power generation) and the lumbar extension which is prominent kinematics during the stoop lifting could be produced by the contributions of the knee joint kinetic factors(flexor moment, power absorption, bi-articular muscle function). PMID:19183507

Lower extremity joint kinetics and lumbar curvature during squat and stoop lifting.

PubMed

Hwang, Seonhong; Kim, Youngeun; Kim, Youngho

2009-02-02

In this study, kinematics and kinetics of the lower extremity joint and the lumbar lordosis during two different symmetrical lifting techniques(squat and stoop) were examined using the three-dimensional motion analysis. Twenty-six young male volunteers were selected for the subjects in this study. While they lifted boxes weighing 5, 10 and 15 kg by both squat and stoop lifting techniques, their motions were captured and analyzed using the 3D motion analysis system which was synchronized with two forceplates and the electromyographic system. Joint kinematics was determined by the forty-three reflective markers which were attached on the anatomical locations based on the VICON Plug-in-Gait marker placement protocol. Joint kinetics was analyzed by using the inverse dynamics. Paired t-test and Kruskal-Wallis test was used to compare the differences of variables between two techniques, and among three different weights. Correlation coefficient was calculated to explain the role of lower limb joint motion in relation to the lumbar lordosis. There were not significant differences in maximum lumbar joint moments between two techniques. The hip and ankle contributed the most part of the support moment during squat lifting, and the knee flexion moment played an important role in stoop lifting. The hip, ankle and lumbar joints generated power and only the knee joint absorbed power in the squat lifting. The knee and ankle joints absorbed power, the hip and lumbar joints generated power in the stoop lifting. The bi-articular antagonist muscles' co-contraction around the knee joint during the squat lifting and the eccentric co-contraction of the gastrocnemius and the biceps femoris were found important for maintaining the straight leg during the stoop lifting. At the time of lordotic curvature appearance in the squat lifting, there were significant correlations in all three lower extremity joint moments with the lumbar joint. Differently, only the hip moment had significant correlation with the lumbar joint in the stoop lifting. In conclusion, the knee extension which is prominent kinematics during the squat lifting was produced by the contributions of the kinetic factors from the hip and ankle joints(extensor moment and power generation) and the lumbar extension which is prominent kinematics during the stoop lifting could be produced by the contributions of the knee joint kinetic factors(flexor moment, power absorption, bi-articular muscle function).

Hydrotherapy improves pain and function in older women with knee osteoarthritis: a randomized controlled trial.

PubMed

Dias, João Marcos; Cisneros, Lígia; Dias, Rosângela; Fritsch, Carolina; Gomes, Wellington; Pereira, Leani; Santos, Mary Luci; Ferreira, Paulo Henrique

Currently, there is poor evidence of the effect of hydrotherapy alone on patients with hip or knee osteoarthritis. The study aimed to assess the impact of hydrotherapy on pain, function, and muscle function in older women with knee osteoarthritis. A randomized controlled trial was conducted to evaluate the efficacy of hydrotherapy in women with knee osteoarthritis. Seventy-three women aged 65 and older were randomized to hydrotherapy (n=36) or a control group (n=37). The hydrotherapy group received the intervention program in a heated pool (twice per week for six weeks) and an educational protocol while the control group received an educational protocol only. Primary outcomes (before and post-treatment) were pain intensity (0-100) and function (0-100), assessed with the WOMAC questionnaire. Secondary outcomes (before and post-treatment) were knee extensor and knee flexor muscle performance (strength, power, and endurance), assessed by an isokinetic dynamometer. The magnitude of change between the groups for the outcomes was calculated using linear regression models adjusted by baseline outcome values. The hydrotherapy group had better outcomes for pain (adjusted mean difference=11 points, 95% CI: 3-18) and function (adjusted mean difference=12 points, 95% CI: 5-18). Patients receiving hydrotherapy had better performance for knee flexor and extensor strength, knee flexor power, and knee extensor endurance. Older women with knee osteoarthritis are likely to have benefits from a course of hydrotherapy exercises. Registry of clinical trials (Trial number RBR-8F57KR) - http://www.ensaiosclinicos.gov.br/rg/RBR-8f57kr/. Copyright © 2017 Associação Brasileira de Pesquisa e Pós-Graduação em Fisioterapia. Publicado por Elsevier Editora Ltda. All rights reserved.

Relationship between physical function and biomechanical gait patterns in boys with haemophilia.

PubMed

Stephensen, D; Taylor, S; Bladen, M; Drechsler, W I

2016-11-01

The World Federation of Haemophilia recommends joint and muscle health is evaluated using X-ray and magnetic resonance imaging, together with clinical examination scores. To date, inclusion of performance-based functional activities to monitor children with the condition has received little attention. To evaluate test-retest repeatability of physical function tests and quantify relationships between physical function, lower limb muscle strength and gait patterns in young boys with haemophilia. Timed 6-minute walk, timed up and down stairs, timed single leg stance, muscle strength of the knee extensors, ankle dorsi and plantar flexors, together with joint biomechanics during level walking were collected from 21 boys aged 6-12 years with severe haemophilia. Measures of physical function and recording of muscle strength with a hand-held myometer were repeatable (ICC > 0.78). Distances walked in six minutes, time taken to go up and down a flight of stairs and lower limb muscle strength correlated closely with ankle range of motion, together with peak knee flexion and ankle dorsi and plantarflexion moments during walking (P < 0.05). Alterations in gait patterns of boys with haemophilia appear to be associated with changes in performance of physical function and performance seems to depend on their muscle strength. Timed 6-minute walk test, timed up and down steps test and muscle strength of the knee extensors showed the strongest correlation with biomechanical joint function, and hence might serve as a basis for the clinical monitoring of physical function outcomes in children with haemophilia. © 2016 John Wiley & Sons Ltd.

Whole limb kinematics are preferentially conserved over individual joint kinematics after peripheral nerve injury

PubMed Central

Chang, Young-Hui; Auyang, Arick G.; Scholz, John P.; Nichols, T. Richard

2009-01-01

Summary Biomechanics and neurophysiology studies suggest whole limb function to be an important locomotor control parameter. Inverted pendulum and mass-spring models greatly reduce the complexity of the legs and predict the dynamics of locomotion, but do not address how numerous limb elements are coordinated to achieve such simple behavior. As a first step, we hypothesized whole limb kinematics were of primary importance and would be preferentially conserved over individual joint kinematics after neuromuscular injury. We used a well-established peripheral nerve injury model of cat ankle extensor muscles to generate two experimental injury groups with a predictable time course of temporary paralysis followed by complete muscle self-reinnervation. Mean trajectories of individual joint kinematics were altered as a result of deficits after injury. By contrast, mean trajectories of limb orientation and limb length remained largely invariant across all animals, even with paralyzed ankle extensor muscles, suggesting changes in mean joint angles were coordinated as part of a long-term compensation strategy to minimize change in whole limb kinematics. Furthermore, at each measurement stage (pre-injury, paralytic and self-reinnervated) step-by-step variance of individual joint kinematics was always significantly greater than that of limb orientation. Our results suggest joint angle combinations are coordinated and selected to stabilize whole limb kinematics against short-term natural step-by-step deviations as well as long-term, pathological deviations created by injury. This may represent a fundamental compensation principle allowing animals to adapt to changing conditions with minimal effect on overall locomotor function. PMID:19837893

Zapateado technique as an injury risk in Mexican folkloric and Spanish dance: an analysis of execution, ground reaction force, and muscle strength.

PubMed

Echegoyen, Soledad; Aoyama, Takeshi; Rodríguez, Cristina

2013-06-01

Zapateado is a repetitive percussive footwork in dance. This percussive movement, and the differences in technique, may be risk factors for injury. A survey on zapateado dance students found a rate of 1.5 injuries/1,000 exposures. Knee injuries are more frequent than in Spanish dancers than folkloric dancers. The aim of this research was to study the relationship between technique and ground reaction force between zapateado on Spanish and Mexican folkloric dancers. Ten female dance students (age 22.4 ± 4 yrs), six Spanish dancers and four Mexican folkloric dancers, were considered. Each student performed zapateado with a flat foot, wearing high-heeled shoes during 5 seconds on a force platform. Videotapes were taken on a lateral plane, and knee and hip angles in each movement phase were measured with Dartfish software. Additionally, knee and ankle flexor and extensor strength was measured with a dynamometer. Ground reaction forces were lower for Spanish dancers than Mexican folkloric dancers. Spanish dancers had less knee flexion when the foot contacted to the ground than did Mexican folkloric dancers. On Spanish dancers, the working leg had more motion in relation to hip and knee angles than was seen in folkloric dancers. The ankle extensors were stronger on folkloric dancers, and there were no differences for the other muscle groups. Knee flexion at foot contact and muscle strength imbalance could be risk factors for injuries. It is suggested that the technique in Spanish dance in Mexico be reviewed, although more studies are required to define more risk factors.

The synergic effects of mirror therapy and neuromuscular electrical stimulation for hand function in stroke patients.

PubMed

Yun, Gi Jeong; Chun, Min Ho; Park, Ji Young; Kim, Bo Ryun

2011-06-01

To investigate the synergic effects of mirror therapy and neuromuscular electrical stimulation (NMES) for hand function in stroke patients. Sixty patients with hemiparesis after stroke were included (41 males and 19 females, average age 63.3 years). Twenty patients had NMES applied and simultaneously underwent mirror therapy. Twenty patients had NMES applied only, and twenty patients underwent mirror therapy only. Each treatment was done five days per week, 30 minutes per day, for three weeks. NMES was applied on the surface of the extensor digitorum communis and extensor pollicis brevis for open-hand motion. Muscle tone, Fugl-Meyer assessment, and power of wrist and hand were evaluated before and after treatment. There were significant improvements in the Fugl-Meyer assessment score in the wrist, hand and coordination, as well as power of wrist and hand in all groups after treatment. The mirror and NMES group showed significant improvements in the Fugl-Meyer scores of hand, wrist, coordination and power of hand extension compared to the other groups. However, the power of hand flexion, wrist flexion, and wrist extension showed no significant differences among the three groups. Muscle tone also showed no significant differences in the three groups. Our results showed that there is a synergic effect of mirror therapy and NMES on hand function. Therefore, a hand rehabilitation strategy combined with NMES and mirror therapy may be more helpful for improving hand function in stroke patients than NMES or mirror therapy only.

Surgery-Induced Changes and Early Recovery of Hip-Muscle Strength, Leg-Press Power, and Functional Performance after Fast-Track Total Hip Arthroplasty: A Prospective Cohort Study

PubMed Central

Holm, Bente; Thorborg, Kristian; Husted, Henrik; Kehlet, Henrik; Bandholm, Thomas

2013-01-01

Background By measuring very early changes in muscle strength and functional performance after fast-track total hip arthroplasty (THA), post-operative rehabilitation, introduced soon after surgery, can be designed to specifically target identified deficits. Objective(s) Firstly, to quantify changes (compared to pre-operative values) in hip muscle strength, leg-press power, and functional performance in the first week after THA, and secondly, to explore relationships between the muscle strength changes, and changes in hip pain, systemic inflammation, and thigh swelling. Design Prospective, cohort study. Setting Convenience sample of patients receiving a THA at Copenhagen University Hospital, Hvidovre, Denmark, between March and December 2011. Participants Thirty-five patients (65.9±7.2 years) undergoing THA. Main outcome measures Hip muscle strength, leg-press power, performance-based function, and self-reported disability were determined prior to, and 2 and 8 days after, THA (Day 2 and 8, respectively). Hip pain, thigh swelling, and C-Reactive Protein were also determined. Results Five patients were lost to follow-up. Hip muscle strength and leg press power were substantially reduced at Day 2 (range of reductions: 41–58%, P<0.001), but less pronounced at Day 8 (range of reductions: 23–31%, P<0.017). Self-reported symptoms and function (HOOS: Pain, Symptoms, and ADL) improved at Day 8 (P<0.014). Changes in hip pain, C-Reactive Protein, and thigh swelling were not related to the muscle strength and power losses. Conclusion(s) Hip muscle strength and leg-press power decreased substantially in the first week after THA – especially at Day 2 – with some recovery at Day 8. The muscle strength loss and power loss were not related to changes in hip pain, systemic inflammation, or thigh swelling. In contrast, self-reported symptoms and function improved. These data on surgery-induced changes in muscle strength may help design impairment-directed, post-operative rehabilitation to be introduced soon after surgery. Trial Registration ClinicalTrials.gov NCT01246674. PMID:23614020

Customizing Extensor Reconstruction in Vascularized Toe Joint Transfers to Finger Proximal Interphalangeal Joints: A Strategic Approach for Correcting Extensor Lag.

PubMed

Loh, Charles Yuen Yung; Hsu, Chung-Chen; Lin, Cheng-Hung; Chen, Shih-Heng; Lien, Shwu-Huei; Lin, Chih-Hung; Wei, Fu-Chan; Lin, Yu-Te

2017-04-01

Vascularized toe proximal interphalangeal joint transfer allows the restoration of damaged joints. However, extensor lag and poor arc of motion have been reported. The authors present their outcomes of treatment according to a novel reconstructive algorithm that addresses extensor lag and allows for consistent results postoperatively. Vascularized toe joint transfers were performed in a consecutive series of 26 digits in 25 patients. The average age was 30.5 years, with 14 right and 12 left hands. Reconstructed digits included eight index, 10 middle, and eight ring fingers. Simultaneous extensor reconstructions were performed and eight were centralization of lateral bands, five were direct extensor digitorum longus-to-extensor digitorum communis repairs, and 13 were central slip reconstructions. The average length of follow-up was 16.7 months. The average extension lag was 17.9 degrees. The arc of motion was 57.7 degrees (81.7 percent functional use of pretransfer toe proximal interphalangeal joint arc of motion). There was no significant difference in the reconstructed proximal interphalangeal joint arc of motion for the handedness (p = 0.23), recipient digits (p = 0.37), or surgical experience in vascularized toe joint transfer (p = 0.25). The outcomes of different techniques of extensor mechanism reconstruction were similar in terms of extensor lag, arc of motion, and reconstructed finger arc of motion compared with the pretransfer toe proximal interphalangeal joint arc of motion. With this treatment algorithm, consistent outcomes can be produced with minimal extensor lag and maximum use of potential toe proximal interphalangeal joint arc of motion. Therapeutic, IV.

The influence of fat infiltration of back extensor muscles on osteoporotic vertebral fractures.

PubMed

So, Kwang-Young; Kim, Dae-Hee; Choi, Dong-Hyuk; Kim, Choong-Young; Kim, Jeong-Seok; Choi, Yong-Soo

2013-12-01

Retrospective study. To investigate the influence of fat infiltration at low back extensor muscles on osteoporotic vertebral fracture. In persons with stronger back muscles, the risk of osteoporotic vertebral fractures will likely be lower than in those persons with weaker back muscles. However, the degree of influence of fat infiltration of the back extensor muscle on osteoporotic vertebral fracture remains controversial. Two hundred and thirty-seven patients who had undergone lumbar spine magnetic resonance imaging and bone mineral density (BMD) were enrolled in this study. The amount of low back extensor muscle was determined using the pseudocoloring technique on an axial view of the L3 level. The patients were divided into two groups: osteoporotic vertebral fracture group (group A) and non-fracture group (group B). The amount of low back extensor muscle is compared with BMD, degenerative change of disc, osteophyte grade of facet joint and promontory angle to reveal the association between these factors. A negative correlation is found between age and the amount of low back extensor muscle (p=0.001). The amount of low back extensor muscle in group A and group B was 60.3%±14.5% and 64.2%±9.3% respectively, thus showing a significantly smaller amount of low back extensor muscle in the osteoporotic vertebral fracture group (p=0.015). Fat infiltration of low back extensor muscle was increased in osteoporotic vertebral fracture patients. Therefore, fat infiltration of low back extensor muscle in an elderly person may be a risk factor of osteoporotic vertebral fracture.

A robotic exoskeleton to treat crouch gait from cerebral palsy: Initial kinematic and neuromuscular evaluation.

PubMed

Lerner, Zachary F; Damiano, Diane L; Bulea, Thomas C

2016-08-01

A robotic exoskeleton was designed for individuals with crouch gait caused by cerebral palsy with the intent to supplement existing muscle function during walking. The aim of this study was to evaluate how powered knee extension assistance provided during stance and swing phases of the gait cycle affect knee kinematics, and knee flexor and extensor muscle activity. Muscle activity and kinematic data were collected from four individuals with crouch gait from cerebral palsy during their normal walking condition and while walking with the exoskeleton under stance, swing, and stance & swing assistance. The exoskeleton was effective in reducing crouch by an average of 13.8° in three of the four participants when assistance was provided during the stance phase; assistance during the swing phase alone was ineffective. Peak knee extensor activity was maintained for all of the conditions during the stance and swing phases. Integrated (i.e. area under the curve) knee extensor activity decreased in two of the subjects indicating a more well-modulated activation pattern. Modest increases in peak and integrated antagonist knee flexor activity were exhibited in all participants; the subject without kinematic improvement had the greatest increase. While the exoskeleton was well tolerated, additional training with a focus on reducing knee flexor activity may lead to further improvements in crouch gait reduction.

Physical and functional measures related to low back pain in individuals with lower-limb amputation: an exploratory pilot study.

PubMed

Friel, Karen; Domholdt, Elizabeth; Smith, Douglas G

2005-01-01

For this study, we compared the physical impairments and functional deficits of individuals with lower-limb amputation (LLA) for those with and without low back pain (LBP). Nineteen participants with LLA were placed into two groups based on visual analog scores of LBP. We assessed functional limitations, iliopsoas length, hamstring length, abdominal strength, back extensor strength, and back extensor endurance. Data analysis included correlations and t-tests. We found significant correlations between pain score and functional limitations, iliopsoas length, and back extensor endurance. We also detected significant differences in functional limitations, iliopsoas length, back extensor strength, and back extensor endurance between those with and without LBP. We saw significant differences in back extensor strength and back extensor endurance between those with transtibial and transfemoral amputations. Differences exist in physical measures of individuals with LLA with and without LBP. Clinicians should consider these impairments in individuals with amputation who experience LBP. Because of the participants' characteristics, these findings may be applicable to veterans with LLA.

The Trainability of Adolescent Soccer Players to Brief Periodized Complex Training.

PubMed

Chatzinikolaou, Athanasios; Michaloglou, Konstantinos; Avloniti, Alexandra; Leontsini, Diamanda; Deli, Chariklia K; Vlachopoulos, Dimitris; Gracia-Marco, Luis; Arsenis, Sotirios; Athanailidis, Ioannis; Draganidis, Dimitrios; Jamurtas, Athanasios Z; Williams, Craig A; Fatouros, Ioannis G

2018-05-01

To investigate the effect of a complex, short-term strength/power training protocol on performance and body composition of elite early adolescent soccer players. Twenty-two players (14-15 y) were randomly assigned to (1) an experimental group (N = 12; participated in a 5-wk training protocol with traditional multijoint power resistance exercises, Olympic-style lifts, plyometric drills, and speed work; 4 times per week) or (2) a control group (N = 10). Strength and power performance (jumping, speed, change of direction, repeated sprint ability, endurance, isokinetic strength of knee flexors and extensors, maximal strength in various lifts, and speed-endurance) were evaluated pretraining and posttraining. Cessation of training for 5 weeks in the control group induced a marked performance deterioration (∼5%-20%). Training not only prevented strength performance deterioration but also increased it (∼2%-30%). Endurance and repeated sprint ability declined to a smaller extent in experimental group compared with control group (15% vs 7.5%). Isometric strength and body composition remained unaltered in both groups. Results demonstrate that (1) young players exhibit a high level of trainability of their strength/power performance (but not endurance) in response to a short-term complex training protocol during early adolescence, (2) Olympic-style lifts are characterized by increased safety in this age group and appear to be highly effective, (3) lifts incorporating a hip thrust result in increased strength of both knee extensors and flexors, (4) cessation of training for only 5 weeks results in marked deterioration of strength/power and endurance performance, and (5) improvement of strength/power performance may be related to neural-based adaptation as body composition remained unaffected.

Performance of a six-legged planetary rover - Power, positioning, and autonomous walking

NASA Technical Reports Server (NTRS)

Krotkov, Eric; Simmons, Reid

1992-01-01

The authors quantify several performance metrics for the Ambler, a six-legged robot configured for autonomous traversal of Mars-like terrain. They present power consumption measures for walking on sandy terrain and for vertical lifts at different velocities. They document the accuracy of a novel dead reckoning approach, and analyze the accuracy. They describe the results of autonomous walking experiments in terms of terrain traversed, walking speed, number of instructions executed and endurance.

Performance of a six-legged planetary rover - Power, positioning, and autonomous walking

NASA Astrophysics Data System (ADS)

Krotkov, Eric; Simmons, Reid

The authors quantify several performance metrics for the Ambler, a six-legged robot configured for autonomous traversal of Mars-like terrain. They present power consumption measures for walking on sandy terrain and for vertical lifts at different velocities. They document the accuracy of a novel dead reckoning approach, and analyze the accuracy. They describe the results of autonomous walking experiments in terms of terrain traversed, walking speed, number of instructions executed and endurance.

Froghopper-inspired direction-changing concept for miniature jumping robots.

PubMed

Jung, Gwang-Pil; Cho, Kyu-Jin

2016-09-14

To improve the maneuverability and agility of jumping robots, several researchers have studied steerable jumping mechanisms. This steering ability enables robots to reach a particular target by controlling their jumping direction. To this end, we propose a novel direction-changing concept for miniature jumping robots. The proposed concept allows robots to be steerable while exerting minimal effects on jumping performance. The key design principles were adopted from the froghopper's power-producing hind legs and the moment cancellation accomplished by synchronized leg operation. These principles were applied via a pair of symmetrically positioned legs and conventional gears, which were modeled on the froghopper's anatomy. Each leg has its own thrusting energy, which improves jumping performance by allowing the mechanism to thrust itself with both power-producing legs. Conventional gears were utilized to simultaneously operate the legs and cancel out the moments that they induce, which minimizes body spin. A prototype to verify the concept was built and tested by varying the initial jumping posture. Three jumping postures (synchronous, asynchronous, and single-legged) were tested to investigate how synchronization and moment cancelling affect jumping performance. The results show that synchronous jumping allows the mechanism to change direction from -40° to 40°, with an improved take-off speed. The proposed concept can only be steered in a limited range of directions, but it has potential for use in miniature jumping robots that can change jumping direction with a minimal drop in jumping performance.

Are unilateral and bilateral patellar tendinopathy distinguished by differences in anthropometry, body composition, or muscle strength in elite female basketball players?

PubMed Central

Gaida, J; Cook, J; Bass, S; Austen, S; Kiss, Z

2004-01-01

Background: Overuse injury to the patellar tendon (patellar tendinopathy) is a major reason for interrupted training and competition for elite athletes. In both sexes, the prevalence of unilateral and bilateral tendinopathy has been shown to differ. It has been proposed that bilateral pathology may have a different aetiology from unilateral pathology. Investigation of risk factors that may be unique to unilateral and bilateral patellar tendinopathy in female athletes may reveal insights into the aetiology of this condition. Objectives: To examine whether anthropometry, body composition, or muscle strength distinguished elite female basketball players with unilateral or bilateral patellar tendinopathy. Methods: Body composition, anthropometry, and muscle strength were compared in elite female basketball players with unilateral (n = 8), bilateral (n = 7), or no (n = 24) patellar tendinopathy. Body composition was analysed using a dual energy x ray absorptiometer. Anthropometric measures were assessed using standard techniques. Knee extensor strength was measured at 180°/s using an isokinetic dynamometer. z scores were calculated for the unilateral and bilateral groups (using the no tendinopathy group as controls). z scores were tested against zero. Results: The tibia length to stature ratio was approximately 1.3 (1.3) SDs above zero in both the affected and non-affected legs in the unilateral group (p<0.05). The waist to hip ratio was 0.66 (0.78) SD above zero in the unilateral group (p<0.05). In the unilateral group, leg lean to total lean ratio was 0.42 (0.55) SD above zero (p<0.07), the trunk lean to total lean ratio was 0.63 (0.68) SD below zero (p<0.05), and leg fat relative to total fat was 0.47 (0.65) SD below zero (p<0.09). In the unilateral group, the leg with pathology was 0.78 (1.03) SD weaker during eccentric contractions (p<0.07). Conclusions: Unilateral patellar tendinopathy has identifiable risk factors whereas bilateral patellar tendinopathy may not. This suggests that the aetiology of these conditions may be different. However, interpretation must respect the limitation of small subject numbers. PMID:15388543

Leg extension power is a pre-disaster modifiable risk factor for post-traumatic stress disorder among survivors of the Great East Japan Earthquake: a retrospective cohort study.

PubMed

Momma, Haruki; Niu, Kaijun; Kobayashi, Yoritoshi; Huang, Cong; Otomo, Atsushi; Chujo, Masahiko; Tadaura, Hiroko; Nagatomi, Ryoichi

2014-01-01

Post-traumatic stress disorder (PTSD) is a common psychological problem following natural disasters. Although pre-disaster risk factors are important for early detection and proactive support, the examination of such has been limited to sociodemographic factors, which were largely unaffected by the disasters. We examined the association between pre-disaster physical functioning and lifestyle and PTSD symptoms five months after the earthquake in the Great East Japan Earthquake survivors who were participating in a pre-existing cohort study. We designed a retrospective cohort study of a cooperative association in Sendai from August 2010 to August 2011. In 2010, lifestyle, physical condition, and sociodemographic factors were examined by self-reported questionnaires completed by 522 employees of this organization. We also measured the leg extension power of all the participants. PTSD symptoms were evaluated by the Japanese version of the Impact of Event Scale-Revised (IES-R-J) following the earthquake of 2011. In multivariate linear regression analysis, leg extension power (β = -0.128, P = 0.025), daily drinking (β  = 0.203, P = 0.006), and depressive symptoms (β  = 0.139, P = 0.008) were associated with total score of the IES-R-J among men. Moreover, for the IES-R-J subscale, leg extension power was also negatively associated with Intrusion (β = -0.114, P = 0.045) and Hyperarousal (β = -0.163, P = 0.004) after adjusting for all other significant variables. For women, hypertension (β  = 0.226, P = 0.032) and depressive symptoms (β  = 0.205, P = 0.046) were associated with the total score of the IES-R-J. Leg extension power is a potentially modifiable pre-disaster risk factor among men for attenuating the severity of PTSD symptoms associated with great disasters such as the Great East Japan Earthquake among men.

Crouch gait can be an effective form of forced-use/no constraint exercise for the paretic lower limb in stroke

PubMed Central

Rota, Viviana; Malloggi, Chiara; Brugliera, Luigia; Catino, Luigi

2017-01-01

In hemiplegic gait the paretic lower limb provides less muscle power and shows a briefer stance compared with the unaffected limb. Yet, a longer stance and a higher power can be obtained from the paretic lower limb if gait speed is increased. This supports the existence of a ‘learned non-use’ phenomenon, similar to that underlying some asymmetric impairments of the motion of the eyes and of the upper limbs. Crouch gait (CG) (bent-hip bent-knee, about 30° minimum knee flexion) might be an effective form of ‘forced-use’ treatment of the paretic lower limb. It is not known whether it also stimulates a more symmetric muscle power output. Gait analysis on a force treadmill was carried out in 12 healthy adults and seven hemiplegic patients (1–127 months after stroke, median: 1.6). Speed was imposed at 0.3 m/s. Step length and single and double stance times, sagittal joint rotations, peak positive power, and work in extension of the hip, knee, and ankle (plantar flexion), and surface electromyography (sEMG) area from extensor muscles during the generation of power were measured on either side during both erect and crouch walking. Significance was set at P less than 0.05; corrections for multiplicity were applied. Patients, compared with healthy controls, adopted in both gait modalities and on both sides a shorter step length (61–84%) as well as a shorter stance (76–90%) and swing (63–83%) time. As a rule, they also provided a higher muscular work (median: 137%, range: 77–250%) paralleled by a greater sEMG area (median: 174%, range: 75–185%). In erect gait, the generation of peak extensor power across hip, knee, and ankle joints was in general lower (83–90%) from the paretic limb and higher (98–165%) from the unaffected limb compared with control values. In CG, peak power generation across the three lower limb joints was invariably higher in hemiparetic patients: 107–177% from the paretic limb and 114–231% from the unaffected limb. When gait shifted from erect to crouch, only for hemiplegic patients, at the hip, the paretic/unaffected ratio increased significantly. For peak power, work, sEMG area, and joint rotation, the paretic/unaffected ratio increased from 55 to 85%, 56 to 72%, 68 to 91%, and 67 to 93%, respectively. CG appears to be an effective form of forced-use exercise eliciting more power and work from the paretic lower limb muscles sustained by a greater neural drive. It also seems effective in forcing a more symmetric power and work from the hip extensor muscles, but neither from the knee nor the ankle. PMID:28574860

Reference trajectory generation for rehabilitation robots: complementary limb motion estimation.

PubMed

Vallery, Heike; van Asseldonk, Edwin H F; Buss, Martin; van der Kooij, Herman

2009-02-01

For gait rehabilitation robots, an important question is how to ensure stable gait, while avoiding any interaction forces between robot and human in case the patient walks correctly. To achieve this, the definition of "correct" gait needs to adapted both to the individual patient and to the situation. Recently, we proposed a method for online trajectory generation that can be applied for hemiparetic subjects. Desired states for one (disabled) leg are generated online based on the movements of the other (sound) leg. An instantaneous mapping between legs is performed by exploiting physiological interjoint couplings. This way, the patient generates the reference motion for the affected leg autonomously. The approach, called Complementary Limb Motion Estimation (CLME), is implemented on the LOPES gait rehabilitation robot and evaluated with healthy subjects in two different experiments. In a previously described study, subjects walk only with one leg, while the robot's other leg acts as a fake prosthesis, to simulate complete loss of function in one leg. This study showed that CLME ensures stable gait. In a second study, to be presented in this paper, healthy subjects walk with both their own legs to assess the interference with self-determined walking. Evaluation criteria are: Power delivered to the joints by the robot, electromyography (EMG) distortions, and kinematic distortions, all compared to zero torque control, which is the baseline of minimum achievable interference. Results indicate that interference of the robot is lower with CLME than with a fixed reference trajectory, mainly in terms of lowered exchanged power and less alteration of EMG. This implies that subjects can walk more naturally with CLME, and they are assisted less by the robot when it is not needed. Future studies with patients are yet to show whether these properties of CLME transfer to the clinical domain.

Extensor Tendon Injuries and Repairs in the Hand

PubMed Central

Kontor, J. A.

1982-01-01

Due to their superficial course, the extensor tendons are frequently lacerated over the dorsum of the hand and fingers. Excellent functional results are obtained in repairs of simple tendon lacerations. ‘Open’ mallet lacerations over the distal IP joint or involving the central extensor slip over the proximal IP joint require more precise suturing methods. More proximal extensor tendon divisions near the wrist involve dissection of the retracted finger extensors or long thumb extensor in the distal forearm and more formal tendon repairs, including a possible tendon transfer to the thumb. ‘Closed injuries’, with varying degrees of extensor tendon disruption, occur at three main sites. The mallet injury at the DIP joint and the boutonnière deformity over the PIP joint are sometimes recognized late, but respond to conservative splinting for a minimum of four weeks with guarded motion avoiding secondary stiffening of the remaining small joints of the hand. Surgery of closed injuries most frequently involves the intra-articular traction fracture type of mallet deformities in which the DIP joint has taken the brunt of the injury. PMID:21286174

Quadriceps strength, quadriceps power, and gait speed in older U.S. adults with diabetes mellitus: results from the National Health and Nutrition Examination Survey, 1999-2002.

PubMed

Kalyani, Rita Rastogi; Tra, Yolande; Yeh, Hsin-Chieh; Egan, Josephine M; Ferrucci, Luigi; Brancati, Frederick L

2013-05-01

To examine the independent association between diabetes mellitus (and its duration and severity) and quadriceps strength, quadriceps power, and gait speed in a national population of older adults. Cross-sectional nationally representative survey. United States. Two thousand five hundred seventy-three adults aged 50 and older in the National Health and Nutrition Examination Survey 1999-2002 who had assessment of quadriceps strength. Diabetes mellitus was ascertained according to questionnaire. Measurement of isokinetic knee extensor (quadriceps) strength was performed at 60º/s. Gait speed was assessed using a 20-foot walk test. Multiple linear regression analyses were used to assess the association between diabetes mellitus status and outcomes, adjusting for potential confounders or mediators. Older U.S. adults with diabetes mellitus had significantly slower gait speed (0.96 ± 0.02 m/s) than those without (1.08 ± 0.01 m/s; P < .001). After adjusting for demographic characteristics, weight, and height, diabetes mellitus was also associated with significantly lower quadriceps strength (-4.6 ± 1.9 Nm; P = .02) and power (-4.9 ± 2.0 W; P = .02) and slower gait speed (-0.05 ± 0.02 m/s; P = .002). Associations remained significant after adjusting for physical activity and C-reactive protein. After accounting for comorbidities (cardiovascular disease, peripheral neuropathy, amputation, cancer, arthritis, fracture, chronic obstructive pulmonary disease), diabetes mellitus was independently associated only with gait speed (-0.04 ± 0.02 m/s; P = .02). Diabetes mellitus duration in men and women was negatively associated with age-adjusted quadriceps strength (-5.7 and -3.5 Nm/decade of diabetes mellitus, respectively) and power (-6.1 and -3.8 W/decade of diabetes mellitus, respectively) (all P ≤ .001, no significant interactions according to sex). Glycosylated hemoglobin was not associated with outcomes after accounting for body weight. Older U.S. adults with diabetes mellitus have lower quadriceps strength and quadriceps power that is related to the presence of comorbidities and walk slower than those without diabetes mellitus. Future studies should investigate the relationship between hyperglycemia and subsequent declines in leg muscle function. © 2013, Copyright the Authors Journal compilation © 2013, The American Geriatrics Society.

The influence of ACE ID and ACTN3 R577X polymorphisms on lower-extremity function in older women in response to high-speed power training

PubMed Central

2013-01-01

Background We studied the influence of the ACE I/D and ACTN3 R577X polymorphisms (single or combined) on lower-extremity function in older women in response to high-speed power training. Methods One hundred and thirty-nine healthy older Caucasian women participated in this study (age: 65.5 ± 8.2 years, body mass: 67.0 ± 10.0 kg and height: 1.57 ± 0.06 m). Walking speed (S10) performance and functional capacity assessed by the “get-up and go” (GUG) mobility test were measured at baseline (T1) and after a consecutive 12-week period of high-speed power training (40-75% of one repetition maximum in arm and leg extensor exercises; 3 sets 4–12 reps, and two power exercises for upper and lower extremity). Genomic DNA was extracted from blood samples, and genotyping analyses were performed by PCR methods. Genotype distributions between groups were compared by Chi-Square test and the gains in physical performance were analyzed by two-way, repeated-measures ANOVA. Results There were no significant differences between genotype groups in men or women for adjusted baseline phenotypes (P > 0.05). ACE I/D and ACTN3 polymorphisms showed a significant interaction genotype-training only in S10 (P = 0.012 and P = 0.044, respectively) and not in the GUG test (P = 0.311 and P = 0.477, respectively). Analyses of the combined effects between genotypes showed no other significant differences in all phenotypes (P < 0.05) at baseline. However, in response to high-speed power training, a significant interaction on walking speed (P = 0.048) was observed between the “power” (ACTN3 RR + RX & ACE DD) versus “non-power” muscularity-oriented genotypes (ACTN3 XX & ACE II + ID)]. Conclusions Thus, ACE I/D and ACTN3 R577X polymorphisms are likely candidates in the modulation of exercise-related gait speed phenotype in older women but not a significant influence in mobility traits. PMID:24313907

Extensor Mechanism Disruption after Total Knee Arthroplasty: A Case Series and Review of Literature.

PubMed

Vaishya, Raju; Agarwal, Amit Kumar; Vijay, Vipul

2016-02-04

Extensor mechanism disruption following total knee arthroplasty (TKA) is a rare but devastating complication. These patients may require revision of the implants, but even then, it may not be possible to restore the normal function of the knee after the disruption. The patterns of extensor mechanism disruption can broadly be classified into three types: suprapatellar (quadriceps tendon rupture), transpatellar (patellar fracture), or infrapatellar (patellar tendon rupture). Infrapatellar tendon ruptures are the worst injuries, as they carry maximum morbidity and are challenging to manage. The disruption of the extensor mechanism may occur either intra-operatively or in the immediate postoperative period due to an injury. The treatment of extensor mechanism complications after TKA may include either nonsurgical management or surgical intervention in the form of primary repair or reconstruction with autogenous, allogeneic, or synthetic substitutes. We have provided an algorithm for the management of extensor mechanism disruption after TKA.

Maneuverability and mobility in palm-sized legged robots

NASA Astrophysics Data System (ADS)

Kohut, Nicholas J.; Birkmeyer, Paul M.; Peterson, Kevin C.; Fearing, Ronald S.

2012-06-01

Palm sized legged robots show promise for military and civilian applications, including exploration of hazardous or difficult to reach places, search and rescue, espionage, and battlefield reconnaissance. However, they also face many technical obstacles, including- but not limited to- actuator performance, weight constraints, processing power, and power density. This paper presents an overview of several robots from the Biomimetic Millisystems Laboratory at UC Berkeley, including the OctoRoACH, a steerable, running legged robot capable of basic navigation and equipped with a camera and active tail; CLASH, a dynamic climbing robot; and BOLT, a hybrid crawling and flying robot. The paper also discusses, and presents some preliminary solutions to, the technical obstacles listed above plus issues such as robustness to unstructured environments, limited sensing and communication bandwidths, and system integration.

Experiments in balance with a 2D one-legged hopping machine

NASA Astrophysics Data System (ADS)

Raibert, M. H.; Brown, H. B., Jr.

1984-03-01

The ability to balance is important to the mobility obtained by legged creatures found in nature, and may someday lead to versatile legged vehicles. In order to study the role of balance in legged locomotion and to develop appropriate control strategies, a 2D hopping machine was constructed for experimentation. The machine has one leg on which it hops and runs, making balance a prime consideration. Control of the machine's locomotion was decomposed into three separate parts: a vertical height control part, a horizontal velocity part, and an angular attitude control part. Experiments showed that the three part control scheme, while very simple to implement, was powerful enough to permit the machine to hop in place, to run at a desired rate, to translate from place to place, and to leap over obstacles. Results from modeling and computer simulation of a similar one-legged device are described by Raibert (1983).

Relationships and Predictive Capabilities of Jump Assessments to Soccer-Specific Field Test Performance in Division I Collegiate Players.

PubMed

Lockie, Robert G; Stage, Alyssa A; Stokes, John J; Orjalo, Ashley J; Davis, DeShaun L; Giuliano, Dominic V; Moreno, Matthew R; Risso, Fabrice G; Lazar, Adrina; Birmingham-Babauta, Samantha A; Tomita, Tricia M

2016-12-03

Leg power is an important characteristic for soccer, and jump tests can measure this capacity. Limited research has analyzed relationships between jumping and soccer-specific field test performance in collegiate male players. Nineteen Division I players completed tests of: leg power (vertical jump (VJ), standing broad jump (SBJ), left- and right-leg triple hop (TH)); linear (30 m sprint; 0⁻5 m, 5⁻10 m, 0⁻10, 0⁻30 m intervals) and change-of-direction (505) speed; soccer-specific fitness (Yo-Yo Intermittent Recovery Test Level 2); and 7 × 30-m sprints to measure repeated-sprint ability (RSA; total time (TT), performance decrement (PD)). Pearson's correlations ( r ) determined jump and field test relationships; stepwise regression ascertained jump predictors of the tests ( p < 0.05). All jumps correlated with the 0⁻5, 0⁻10, and 0⁻30 m sprint intervals ( r = -0.65⁻-0.90). VJ, SBJ, and left- and right-leg TH correlated with RSA TT ( r = -0.51⁻-0.59). Right-leg TH predicted the 0⁻5 and 0⁻10 m intervals (R² = 0.55⁻0.81); the VJ predicted the 0⁻30 m interval and RSA TT (R² = 0.41⁻0.84). Between-leg TH asymmetry correlated with and predicted left-leg 505 and RSA PD ( r = -0.68⁻0.62; R² = 0.39⁻0.46). Improvements in jumping ability could contribute to faster speed and RSA performance in collegiate soccer players.

Relationships between explosive and maximal triple extensor muscle performance and vertical jump height.

PubMed

Chang, Eunwook; Norcross, Marc F; Johnson, Sam T; Kitagawa, Taichi; Hoffman, Mark

2015-02-01

The purpose of this study was to examine the relationships between maximum vertical jump height and (a) rate of torque development (RTD) calculated during 2 time intervals, 0-50 milliseconds (RTD50) and 0-200 milliseconds (RTD200) after torque onset and (b) peak torque (PT) for each of the triple extensor muscle groups. Thirty recreationally active individuals performed maximal isometric voluntary contractions (MVIC) of the hip, knee and ankle extensors, and a countermovement vertical jump. Rate of torque development was calculated from 0 to 50 (RTD50) and 0 to 200 (RTD200) milliseconds after the onset of joint torque. Peak torque was identified and defined as the maximum torque value during each MVIC trial. Greater vertical jump height was associated with greater knee and ankle extension RTD50, RTD200, and PT (p ≤ 0.05). However, hip extension RTD50, RTD200, and PT were not significantly related to maximal vertical jump height (p > 0.05). The results indicate that 47.6 and 32.5% of the variability in vertical jump height was explained by knee and ankle extensor RTD50, respectively. Knee and ankle extensor RTD50 also seemed to be more closely related to vertical jump performance than RTD200 (knee extensor: 28.1% and ankle extensor: 28.1%) and PT (knee extensor: 31.4% and ankle extensor: 13.7%). Overall, these results suggest that training specifically targeted to improve knee and ankle extension RTD, especially during the early phases of muscle contraction, may be effective for increasing maximal vertical jump performance.

Skeletal muscle work efficiency with age: the role of non-contractile processes.

PubMed

Layec, Gwenael; Hart, Corey R; Trinity, Joel D; Le Fur, Yann; Jeong, Eun-Kee; Richardson, Russell S

2015-02-01

Although skeletal muscle work efficiency probably plays a key role in limiting mobility of the elderly, the physiological mechanisms responsible for this diminished function remain incompletely understood. Thus, in the quadriceps of young (n=9) and old (n=10) subjects, we measured the cost of muscle contraction (ATP cost) with 31P-magnetic resonance spectroscopy (31P-MRS) during (i) maximal intermittent contractions to elicit a metabolic demand from both cross-bridge cycling and ion pumping and (ii) a continuous maximal contraction to predominantly tax cross-bridge cycling. The ATP cost of the intermittent contractions was significantly greater in the old (0.30±0.22 mM·min-1·N·m-1) compared with the young (0.13±0.03 mM·min-1·N·m-1, P<0.05). In contrast, at the end of the continuous contraction protocol, the ATP cost in the old (0.10±0.07 mM·min-1·N·m-1) was not different from the young (0.06±0.02 mM·min-1·N·m-1, P=0.2). In addition, the ATP cost of the intermittent contractions correlated significantly with the single leg peak power of the knee-extensors assessed during incremental dynamic exercise (r=-0.55; P<0.05). Overall, this study reveals an age-related increase in the ATP cost of contraction, probably mediated by an excessive energy demand from ion pumping, which probably contributes to both the decline in muscle efficiency and functional capacity associated with aging.

Strength deficits identified with concentric action of the hip extensors and eccentric action of the hamstrings predispose to hamstring injury in elite sprinters.

PubMed

Sugiura, Yusaku; Saito, Tomoyuki; Sakuraba, Keishoku; Sakuma, Kazuhiko; Suzuki, Eiichi

2008-08-01

Prospective cohort study. In this prospective cohort study of elite sprinters, muscle strength of the hip extensors, as well as of the knee extensors and flexors, was measured to determine a possible relationship between strength deficits and subsequent hamstring injury within 12 months of testing. The method used for testing muscle strength simulated the specific muscle action during late swing and early contact phases when sprinting. There have been no prospective studies in elite sprinters that examine the concentric and eccentric isokinetic strength of the hip extensors and the quadriceps and hamstring muscles in a manner that reflects their actions in late swing or early contact phases of sprinting. Consequently, the causal relationship between hip and thigh muscle strength and hamstring injury in elite sprinters may not be fully understood. Isokinetic testing was performed on 30 male elite sprinters to assess hip extensors, quadriceps, and hamstring muscle strength. The occurrence of hamstring injury among the subjects was determined during the year following the muscle strength measurements. The strength of the hip extensors, quadriceps, and hamstring muscles, as well as the hamstrings-quadriceps and hip extensors- quadriceps ratios were compared. Hamstring injury occurred in 6 subjects during the 1-year period. Isokinetic testing at a speed of 60 degrees /s revealed weakness of the injured limb with eccentric action of the hamstring muscles and during concentric action of the hip extensors. When performing a side-to-side comparison for the injured sprinters, the hamstring injury always occurred on the weaker side. Differences in the hamstrings-quadriceps and hip extensors-quadriceps strength ratios were also evident between uninjured and injured limbs, and this was attributable to deficits in hamstring strength. Hamstring injury in elite sprinters was associated with weakness during eccentric action of the hamstrings and weakness during concentric action of the hip extensors, but only when tested at the slower speed of 60 degrees /s.

Anticipatory Effects on Lower Extremity Neuromechanics During a Cutting Task.

PubMed

Meinerz, Carolyn M; Malloy, Philip; Geiser, Christopher F; Kipp, Kristof

2015-09-01

Continued research into the mechanism of noncontact anterior cruciate ligament injury helps to improve clinical interventions and injury-prevention strategies. A better understanding of the effects of anticipation on landing neuromechanics may benefit training interventions. To determine the effects of anticipation on lower extremity neuromechanics during a single-legged land-and-cut task. Controlled laboratory study. University biomechanics laboratory. Eighteen female National Collegiate Athletic Association Division I collegiate soccer players (age = 19.7 ± 0.8 years, height = 167.3 ± 6.0 cm, mass = 66.1 ± 2.1 kg). Participants performed a single-legged land-and-cut task under anticipated and unanticipated conditions. Three-dimensional initial contact angles, peak joint angles, and peak internal joint moments and peak vertical ground reaction forces and sagittal-plane energy absorption of the 3 lower extremity joints; muscle activation of selected hip- and knee-joint muscles. Unanticipated cuts resulted in less knee flexion at initial contact and greater ankle toe-in displacement. Unanticipated cuts were also characterized by greater internal hip-abductor and external-rotator moments and smaller internal knee-extensor and external-rotator moments. Muscle-activation profiles during unanticipated cuts were associated with greater activation of the gluteus maximus during the precontact and landing phases. Performing a cutting task under unanticipated conditions changed lower extremity neuromechanics compared with anticipated conditions. Most of the observed changes in lower extremity neuromechanics indicated the adoption of a hip-focused strategy during the unanticipated condition.

Erythema ab igne induced by laptop computer: an emerging disease among adolescents?

PubMed

Brazzelli, V; Grassi, S; Barruscotti, S; Croci, G; Borroni, G

2015-09-17

Erythema ab igne (EAI) was a very common disease in the past, when it occurred mainly among people who worked with fire, or in people who had used heat sources in contact with the skin for warming purposes for long time. In the last decades, with the introduction of central heating in the buildings, EAI incidence was remarkably decreased in Western Countries, and it was found almost exclusively among elderly, and in people affected by defects in thermoregulation or alteration of periphery circulation. Recently, a new slight increase of EAI prevalence has been observed, although with some new features. Here, we describe three cases of adolescents who presented with brownish, reticulated patch on the anterior surface of their thighs. An accurate medical questioning revealed that the patients used to place the lower surface of laptop computer on the extensor side of their thighs in a cross-legged position for many hours (about 6-8 hours) every days. In particular, the patients supported the laptop computer always on the same leg. Laptop computer-induced EAI was diagnosed. Only a few cases of laptop computer-induced EAI have been reported in the literature. Although EAI is poorly symptomatic and it generally evolve to complete remission after a early discontinuance of heat source exposure, chronic lesions of EAI have been regarded as precancerous lesions. Therefore, it is important to implement diagnosis and prevention measures of this disease. Dermatologists should consider new causal agents for old diseases.

Knee extension range of motion and self-report physical function in total knee arthroplasty: mediating effects of knee extensor strength

PubMed Central

2013-01-01

Background Knee extensor strength and knee extension range of motion (ROM) are important predictors of physical function in patients with a total knee arthroplasty (TKA). However, the relationship between the two knee measures remains unclear. The purpose of this study was to examine whether changes in knee extensor strength mediate the association between changes in knee extension ROM and self-report physical function. Methods Data from 441 patients with a TKA were collected preoperatively and 6 months postoperatively. Self-report measure of physical function was assessed by the Short Form 36 (SF-36) questionnaire. Knee extensor strength was measured by handheld dynamometry and knee extension ROM by goniometry. A bootstrapped cross product of coefficients approach was used to evaluate mediation effects. Results Mediation analyses, adjusted for clinicodemographic measures, revealed that the association between changes in knee extension ROM and SF-36 physical function was mediated by changes in knee extensor strength. Conclusions In patients with TKA, knee extensor strength mediated the influence of knee extension ROM on physical function. These results suggest that interventions to improve the range of knee extension may be useful in improving knee extensor performance. PMID:23332039

Effects of Postmortem Freezing on Passive Properties of Rabbit Extensor Digtorum Longus Muscle Tendon Complex

DTIC Science & Technology

1993-06-14

AD-A266 429 INSTITUTE REPORT NO. 483 Effects of Postmortem Freezing on Passive Properties of Rabbit Extensor Digtorum Longus Muscle Tendon Complex D...Extensor Digtorum Longus Muscle Tendon Complex -- Paul H. Leitschuh, Tammy J. Doherty, Dean C. Taylor, Daniel E. Brooks, John B. Ryan This document has...ABSTRACT The tensile properties of the extensor digitorum longus muscle tendon unit (EDL MTU) were studied in 16 white male New Zealand rabbits in both

Impact of Fat Infiltration in Cervical Extensor Muscles on Cervical Lordosis and Neck Pain: A Cross-Sectional Study.

PubMed

Kim, Choong-Young; Lee, Sang-Min; Lim, Seong-An; Choi, Yong-Soo

2018-06-01

Weakness of cervical extensor muscles causes loss of cervical lordosis, which could also cause neck pain. The aim of this study was to investigate the impact of fat infiltration in cervical extensor muscles on cervical lordosis and neck pain. Fifty-six patients who suffered from neck pain were included in this study. Fat infiltration in cervical extensor muscles was measured at each level of C2-3 and C6-7 using axial magnetic resonance imaging. The visual analogue scale (VAS), 12-Item Short Form Health Survey (SF-12), and Neck Disability Index (NDI) were used for clinical assessment. The mean fat infiltration was 206.3 mm 2 (20.3%) at C2-3 and 240.6 mm 2 (19.5%) at C6-7. Fat infiltration in cervical extensor muscles was associated with high VAS scores at both levels ( p = 0.047 at C2-3; p = 0.009 at C6-7). At C2-3, there was a negative correlation between fat infiltration of the cervical extensor muscles and cervical lordosis (r = -0.216; p = 0.020). At C6-7, fat infiltration in the cervical extensor muscles was closely related to NDI ( p = 0.003) and SF-12 ( p > 0.05). However, there was no significant correlation between cervical lordosis and clinical outcomes (VAS, p = 0.112; NDI, p = 0.087; and SF-12, p > 0.05). These results suggest that fat infiltration in the upper cervical extensor muscles has relevance to the loss of cervical lordosis, whereas fat infiltration in the lower cervical extensor muscles is associated with cervical functional disability.

Thermal margin protection system for a nuclear reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Musick, C.R.

1974-02-12

A thermal margin protection system for a nuclear reactor is described where the coolant flow flow trip point and the calculated thermal margin trip point are switched simultaneously and the thermal limit locus is made more restrictive as the allowable flow rate is decreased. The invention is characterized by calculation of the thermal limit Locus in response to applied signals which accurately represent reactor cold leg temperature and core power; cold leg temperature being corrected for stratification before being utilized and reactor power signals commensurate with power as a function of measured neutron flux and thermal energy added to themore » coolant being auctioneered to select the more conservative measure of power. The invention further comprises the compensation of the selected core power signal for the effects of core radial peaking factor under maximum coolant flow conditions. (Official Oazette)« less

Gene Expression Profiling in Slow-Type Calf Soleus Muscle of 30 Days Space-Flown Mice.

PubMed

Gambara, Guido; Salanova, Michele; Ciciliot, Stefano; Furlan, Sandra; Gutsmann, Martina; Schiffl, Gudrun; Ungethuem, Ute; Volpe, Pompeo; Gunga, Hanns-Christian; Blottner, Dieter

2017-01-01

Microgravity exposure as well as chronic disuse are two main causes of skeletal muscle atrophy in animals and humans. The antigravity calf soleus is a reference postural muscle to investigate the mechanism of disuse-induced maladaptation and plasticity of human and rodent (rats or mice) skeletal musculature. Here, we report microgravity-induced global gene expression changes in space-flown mouse skeletal muscle and the identification of yet unknown disuse susceptible transcripts found in soleus (a mainly slow phenotype) but not in extensor digitorum longus (a mainly fast phenotype dorsiflexor as functional counterpart to soleus). Adult C57Bl/N6 male mice (n = 5) flew aboard a biosatellite for 30 days on orbit (BION-M1 mission, 2013), a sex and age-matched cohort were housed in standard vivarium cages (n = 5), or in a replicate flight habitat as ground control (n = 5). Next to disuse atrophy signs (reduced size and myofiber phenotype I to II type shift) as much as 680 differentially expressed genes were found in the space-flown soleus, and only 72 in extensor digitorum longus (only 24 genes in common) compared to ground controls. Altered expression of gene transcripts matched key biological processes (contractile machinery, calcium homeostasis, muscle development, cell metabolism, inflammatory and oxidative stress response). Some transcripts (Fzd9, Casq2, Kcnma1, Ppara, Myf6) were further validated by quantitative real-time PCR (qRT-PCR). Besides previous reports on other leg muscle types we put forth for the first time a complete set of microgravity susceptible gene transcripts in soleus of mice as promising new biomarkers or targets for optimization of physical countermeasures and rehabilitation protocols to overcome disuse atrophy conditions in different clinical settings, rehabilitation and spaceflight.

Two-stage knee arthrodesis with a modular intramedullary nail due to septic failure of revision total knee arthroplasty with extensor mechanism deficiency.

PubMed

Friedrich, Max J; Schmolders, Jan; Wimmer, Matthias D; Strauss, Andreas C; Ploeger, Milena M; Wirtz, Dieter C; Gravius, Sascha; Randau, Thomas M

2017-10-01

Periprosthetic joint infection is a serious complication and reconstruction after failed revision total knee arthroplasty with significant bone loss and compromised soft-tissues can be challenging. Objective of this study was to assess clinical and functional results, implant survival and infection recurrence rates in patients treated with two-stage arthrodesis after failed revision TKA with extensor mechanism deficiencies due to PJI, and to identify the factors that affect outcomes after surgery. Thirty seven patients with PJI treated within a two-stage exchange and reimplantation of an arthrodesis nail between 2008 and 2014 were included. Systemic and local risk factors were graded preoperatively according to McPherson et al. All patients were treated according to a structured treatment algorithm. Clinical and functional evaluation was performed using the Oxford Knee Score and the Visual Analogue Scale. Thirty two of 37 patients (86.5%) were graded as free of infection. Five patients (13.5%) had recurrent infection after arthrodesis with the need of revision surgery. Mean leg-length discrepancy was 2.2cm. The mean VAS for pain was three, the mean Oxford Knee Score was 38±9. Total implant survival at a 74month follow-up was 74.3% (95% CI: 45.4 to 91.1%), as determined by Kaplan-Meier survival curves. Local McPherson Score, as well as number of revisions was found to be of significant influence to the survival rate. Septic failure of revision knee arthroplasty can be effectively treated with two-stage arthrodesis using a modular intramedullary nail, providing a stable and painless limb with satisfactory functional results and acceptable infection eradication rates. Copyright © 2017 Elsevier B.V. All rights reserved.

Association between muscle strength and metabolic syndrome in older Korean men and women: the Korean Longitudinal Study on Health and Aging.

PubMed

Yang, Eun Joo; Lim, Soo; Lim, Jae-Young; Kim, Ki Woong; Jang, Hak Chul; Paik, Nam-Jong

2012-03-01

The objective of the study was to investigate the association between metabolic syndrome (MS) and muscle strength in community-dwelling older men and women in Korea. Korean men and women 65 years and older living in a single, typical South Korean city (n = 647) were enrolled in the Korean Longitudinal Study on Health and Aging study. The diagnosis of MS was evaluated according to the definition of the National Cholesterol Education Program Adult Treatment Panel III. Isokinetic muscle strength of the knee extensors, as determined by peak torque per body weight (newton meter per kilogram) and hand-grip strength per body weight (newton per kilogram), was measured. Participants without MS had greater leg muscle strength and grip strength per weight. The effect of MS on muscle strength was more prominent in men than in women in our study population. Only men showed a significant interaction between MS and age for muscle strength (P = .014), and the effect was greater in men aged 65 to 74 years compared with those older than 75 years (119.2 ± 31.2 vs 134.5 ± 24.3 N m/kg). Participants with MS had weaker knee extensor strength after controlling the covariates (β = -90.80, P = .003), and the interaction term (age × MS × male sex) was significant (β = 1.00, P = .017). Metabolic syndrome is associated with muscle weakness, and this relationship is particularly pronounced in men. Age can modify the impact of MS on muscle strength. Men aged 65 to 74 years with MS need a thorough assessment of muscle strength to prevent disability. Copyright © 2012 Elsevier Inc. All rights reserved.

Evaluation of joint findings with gait analysis in children with hemophilia.

PubMed

Cayir, Atilla; Yavuzer, Gunes; Sayli, Revide Tülin; Gurcay, Eda; Culha, Vildan; Bozkurt, Murat

2014-01-01

Hemophilic arthropathy due to recurrent joint bleeding leads to physical, psychological and socioeconomic problems in children with hemophilia and reduces their quality of life. The purpose of this study was to evaluate joint damage through various parameters and to determine functional deterioration in the musculoskeletal system during walking using kinetic and kinematic gait analysis. Physical examination and kinetic and kinematic gait analysis findings of 19 hemophilic patients aged 7-20 years were compared with those of age, sex and leg length matched controls. Stride time was longer in the hemophilia group (p=0.001) compared to the age matched healthy control group, while hip, knee and ankle joint rotation angles were more limited (p=0.001, p=0.035 and p=0.001, respectively). In the hemophilia group, the extensor moment of the knee joint in the stance phase was less than that in the control group (p=0.001). Stride time was longer in the severe hemophilia group compared to the mild-moderate hemophilia and control groups (p=0.011 and p=0.001, respectively). Rotation angle of the ankle was wider in the control group compared to the other two groups (p=0.001 for both). Rotation angle of the ankle joint was narrower in the severe hemophilia group compared to the others (p=0.001 for each). Extensor moment of the knee joint was greater in the control group compared to the other two groups (p=0.003 and p=0.001, respectively). Walking velocity was higher in the control group compared to the severe hemophilia group. Kinetic and kinematic gait analysis has the sensitivity to detect minimal changes in biomechanical parameters. Gait analysis can be used as a reliable method to detect early joint damage.

Creatine supplementation and physical training in patients with COPD: A double blind, placebo-controlled study

PubMed Central

Faager, Gun; Söderlund, Karin; Sköld, Carl Magnus; Rundgren, Siw; Tollbäck, Anna; Jakobsson, Per

2006-01-01

Study objectives Patients with chronic obstructive pulmonary disease (COPD) have low exercise capacity and low content of high energetic phosphates in their skeletal muscles. The aim of the present study was to investigate whether creatine supplementation together with exercise training may increase physical performance compared with exercise training in patients with COPD. Design In a randomized, double-blind, placebo-controlled study, 23 patients with COPD (forced expiratory volume in one second [FEV1] < 70% of predicted) were randomized to oral creatine (n = 13) or placebo (n = 10) supplementation during an 8-week rehabilitation programme including exercise training. Physical performance was assessed by Endurance Shuttle Walking Test (ESWT), dyspnea and leg fatigue with Borg CR-10, quality of life with St George’s Respiratory Questionnaire (SGRQ). In addition, lung function test, artery blood gases, grip strength test, muscle strength and fatigue in knee extensors were measured. Results COPD patients receiving creatine supplementation increased their average walking time by 61% (ESWT) (p < 0.05) after the training period compared with 48% (p = 0.07) in the placebo group. Rated dyspnea directly after the ESWT decreased significantly from 7 to 5 (p < 0.05) in the creatine group. However, the difference between the groups was not statistically significant neither in walking time nor in rated dyspnea. Creatine supplementation did not increase the health related quality of life, lung function, artery blood gases, grip strength and knee extensor strength/fatigue. Conclusions Oral creatine supplementation in combination with exercise training showed no significant improvement in physical performance, measured as ESWT, in patients with COPD compared with exercise training alone. PMID:18044100

Gene Expression Profiling in Slow-Type Calf Soleus Muscle of 30 Days Space-Flown Mice

PubMed Central

Gambara, Guido; Salanova, Michele; Ciciliot, Stefano; Furlan, Sandra; Gutsmann, Martina; Schiffl, Gudrun; Ungethuem, Ute; Volpe, Pompeo; Gunga, Hanns-Christian; Blottner, Dieter

2017-01-01

Microgravity exposure as well as chronic disuse are two main causes of skeletal muscle atrophy in animals and humans. The antigravity calf soleus is a reference postural muscle to investigate the mechanism of disuse-induced maladaptation and plasticity of human and rodent (rats or mice) skeletal musculature. Here, we report microgravity-induced global gene expression changes in space-flown mouse skeletal muscle and the identification of yet unknown disuse susceptible transcripts found in soleus (a mainly slow phenotype) but not in extensor digitorum longus (a mainly fast phenotype dorsiflexor as functional counterpart to soleus). Adult C57Bl/N6 male mice (n = 5) flew aboard a biosatellite for 30 days on orbit (BION-M1 mission, 2013), a sex and age-matched cohort were housed in standard vivarium cages (n = 5), or in a replicate flight habitat as ground control (n = 5). Next to disuse atrophy signs (reduced size and myofiber phenotype I to II type shift) as much as 680 differentially expressed genes were found in the space-flown soleus, and only 72 in extensor digitorum longus (only 24 genes in common) compared to ground controls. Altered expression of gene transcripts matched key biological processes (contractile machinery, calcium homeostasis, muscle development, cell metabolism, inflammatory and oxidative stress response). Some transcripts (Fzd9, Casq2, Kcnma1, Ppara, Myf6) were further validated by quantitative real-time PCR (qRT-PCR). Besides previous reports on other leg muscle types we put forth for the first time a complete set of microgravity susceptible gene transcripts in soleus of mice as promising new biomarkers or targets for optimization of physical countermeasures and rehabilitation protocols to overcome disuse atrophy conditions in different clinical settings, rehabilitation and spaceflight. PMID:28076365

Peroneal perforator-based peroneus longus tendon and sural neurofasciocutaneous composite flap transfer for a large soft-tissue defect of the forearm: A case report.

PubMed

Hayashida, Kenji; Saijo, Hiroto; Fujioka, Masaki

2018-01-01

We describe the use of a composite flap composed of a sural neurofasciocutaneous flap and a vascularized peroneus longus tendon for the reconstruction of severe composite forearm tissue defects in a patient. A 43-year-old man had his left arm caught in a conveyor belt resulting in a large soft-tissue defect of 18 × 11 cm over the dorsum forearm. The extensor carpi radialis, superficial radial nerve, and radial artery were severely damaged. A free neurofasciocutaneous composite flap measuring 16 × 11 cm was outlined on the patient's left lower leg to allow simultaneous skin, tendon, nerve, and artery reconstruction. The flap, which included the peroneus longus tendon, was elevated on the subfascial plane. After the flap was transferred to the recipient site, the peroneal artery was anastomosed to the radial artery in a flow-through manner. The vascularized tendon graft with 15 cm in length was used to reconstruct the extensor carpi radialis longus tendon defect using an interlacing suture technique. As the skin paddle of the sural neurofasciocutaneous flap and the vascularized peroneus longus tendon graft were linked by the perforator and minimal fascial tissue, the skin paddle was able to rotate and slide with comparative ease. The flap survived completely without any complications. The length of follow-up was 12 months and was uneventful. Range of motion of his left wrist joint was slightly limited to 75 degrees. This novel composite flap may be useful for reconstructing long tendon defects associated with extensive forearm soft tissue defects. © 2016 Wiley Periodicals, Inc.

Transcranial direct current stimulation improves isometric time to exhaustion of the knee extensors.

PubMed

Angius, L; Pageaux, B; Hopker, J; Marcora, S M; Mauger, A R

2016-12-17

Transcranial direct current stimulation (tDCS) can increase cortical excitability of a targeted brain area, which may affect endurance exercise performance. However, optimal electrode placement for tDCS remains unclear. We tested the effect of two different tDCS electrode montages for improving exercise performance. Nine subjects underwent a control (CON), placebo (SHAM) and two different tDCS montage sessions in a randomized design. In one tDCS session, the anodal electrode was placed over the left motor cortex and the cathodal on contralateral forehead (HEAD), while for the other montage the anodal electrode was placed over the left motor cortex and cathodal electrode above the shoulder (SHOULDER). tDCS was delivered for 10min at 2.0mA, after which participants performed an isometric time to exhaustion (TTE) test of the right knee extensors. Peripheral and central neuromuscular parameters were assessed at baseline, after tDCS application and after TTE. Heart rate (HR), ratings of perceived exertion (RPE), and leg muscle exercise-induced muscle pain (PAIN) were monitored during the TTE. TTE was longer and RPE lower in the SHOULDER condition (P<0.05). Central and peripheral parameters, and HR and PAIN did not present any differences between conditions after tDCS stimulation (P>0.05). In all conditions maximal voluntary contraction (MVC) significantly decreased after the TTE (P<0.05) while motor-evoked potential area (MEP) increased after TTE (P<0.05). These findings demonstrate that SHOULDER montage is more effective than HEAD montage to improve endurance performance, likely through avoiding the negative effects of the cathode on excitability. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

The Shank-to-Vertical-Angle as a parameter to evaluate tuning of Ankle-Foot Orthoses.

PubMed

Kerkum, Yvette L; Houdijk, Han; Brehm, Merel-Anne; Buizer, Annemieke I; Kessels, Manon L C; Sterk, Arjan; van den Noort, Josien C; Harlaar, Jaap

2015-09-01

The effectiveness of an Ankle-Foot Orthosis footwear combination (AFO-FC) may be partly dependent on the alignment of the ground reaction force with respect to lower limb joint rotation centers, reflected by joint angles and moments. Adjusting (i.e. tuning) the AFO-FC's properties could affect this alignment, which may be guided by monitoring the Shank-to-Vertical-Angle. This study aimed to investigate whether the Shank-to-Vertical-Angle during walking responds to variations in heel height and footplate stiffness, and if this would reflect changes in joint angles and net moments in healthy adults. Ten subjects walked on an instrumented treadmill and performed six trials while walking with bilateral rigid Ankle-Foot Orthoses. The AFO-FC heel height was increased, aiming to impose a Shank-to-Vertical-Angle of 5°, 11° and 20°, and combined with a flexible or stiff footplate. For each trial, the Shank-to-Vertical-Angle, joint flexion-extension angles and net joint moments of the right leg at midstance were averaged over 25 gait cycles. The Shank-to-Vertical-Angle significantly increased with increasing heel height (p<0.001), resulting in an increase in knee flexion angle and internal knee extensor moment (p<0.001). The stiff footplate reduced the effect of heel height on the internal knee extensor moment (p=0.030), while the internal ankle plantar flexion moment increased (p=0.035). Effects of heel height and footplate stiffness on the hip joint were limited. Our results support the potential to use the Shank-to-Vertical-Angle as a parameter to evaluate AFO-FC tuning, as it is responsive to changes in heel height and reflects concomitant changes in the lower limb angles and moments. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of age and muscle action type on acute strength and power recovery following fatigue of the leg flexors.

PubMed

Thompson, Brennan J; Conchola, Eric C; Stock, Matt S

2015-12-01

Short-term strength and power recovery patterns following fatigue have received little research attention, particularly as they pertain to age-specific responses, and the leg flexors (i.e., hamstrings) muscle group. Thus, research is warranted addressing these issues because both age-related alterations in the neuromuscular system and mode of muscle action (e.g., eccentric, concentric, isometric) may differentially influence recovery responses from fatigue. The aim of this study was to investigate the strength and power recovery responses for eccentric, concentric, and isometric muscle actions of the leg flexors in young and older men following an isometric, intermittent fatigue-inducing protocol. Nineteen young (age = 25 ± 3 years) and nineteen older (71 ± 4) men performed maximal voluntary contractions (MVCs) for eccentric, concentric, and isometric muscle actions followed by a fatigue protocol of intermittent (0.6 duty cycle) isometric contractions of the leg flexors at 60% of isometric MVC. MVCs of each muscle action were performed at 0, 7, 15, and 30 min following fatigue. Peak torque (PT) and mean power values were calculated from the MVCs and the eccentric/concentric ratio (ECR) was derived. For PT and mean power, young men showed incomplete recovery at all time phases, whereas the older men had recovered by 7 min. Eccentric and isometric muscle actions showed incomplete recovery at all time phases, but concentric recovered by 7 min, independent of age. The ECR was depressed for up to 30 min following fatigue. More rapid and pronounced recovery in older men and concentric contractions may be related to physiological differences specific to aging and muscle action motor unit patterns. Individuals and clinicians may use these time course responses as a guide for recovery following activity-induced fatigue.

Autosomal dominant distal myopathy due to a novel ACTA1 mutation.

PubMed

Liewluck, Teerin; Sorenson, Eric J; Walkiewicz, Magdalena A; Rumilla, Kandelaria M; Milone, Margherita

2017-08-01

Mutations in skeletal muscle α-actin 1-encoding gene (ACTA1) cause autosomal dominant or recessive myopathies with marked clinical and pathological heterogeneity. Patients typically develop generalized or limb-girdle pattern of weakness, but recently a family with scapuloperoneal myopathy was reported. We describe a father and 2 children with childhood-to-juvenile onset distal myopathy, carrying a novel dominant ACTA1 variant, c.757G>C (p.Gly253Arg). Father had delayed motor development and developed significant proximal weakness later in life; he was initially misdiagnosed as having spinal muscular atrophy based on electromyographic findings. His children had predominant anterior distal leg and finger extensor involvement. Nemaline rods were abundant on the daughter's biopsy, absent on the father's initial biopsy, and extremely rare on the father's subsequent biopsy a decade later. The father's second biopsy also showed myofibrillar pathology and rare fibers with actin filament aggregates. The present family expands the spectrum of actinopathy to include a distal myopathy. Copyright © 2017 Elsevier B.V. All rights reserved.

Relation of nutritional status to physiological outcomes after cardiac surgery in elderly patients with diabetes mellitus: a preliminary study.

PubMed

Izawa, Kazuhiro P; Watanabe, Satoshi

2016-12-01

To determine differences in physiological outcome (PO) based on the Geriatric Nutritional Risk Index (GNRI) and cut-off values for PO according to the GNRI in elderly post-cardiac surgery patients complicated by diabetes mellitus (DM). Thirty-five patients (72.9 years) were enrolled and divided by GNRI. Patient characteristics and PO of handgrip strength (HG), knee extensor muscle strength (KEMS), maximum gait speed (GS), and one-leg standing time (OLST) were compared between the groups, and cut-off values for PO were determined. These POs were significantly lower in the low-GNRI group (<92 points) than in the high-GNRI (≥92 points) group. The cut-off values for PO were HG, 22.7 kgf; KEMS, 41.5 %BW; GS, 1.2 m/sec; and OLST, 6.7 s. Nutritional status might influence PO following cardiac surgery. The cut-off values of PO reported here might be indicative of the need to improve patient nutritional status.

Effects of Tai Chi Training on Antioxidant Capacity in Pre- and Postmenopausal Women

PubMed Central

Palasuwan, Attakorn; Suksom, Daroonwan; Margaritis, Irène; Soogarun, Suphan; Rousseau, Anne-Sophie

2011-01-01

The risk of oxidative stress-related metabolic diseases increases with menopause and physical inactivity. We hypothesized that an 8-week Tai Chi (TC) training program (2 sessions in class; 2 sessions at home; 1-1:15/session) would improve antioxidant capacity and reduce cardiovascular risks in both pre- (n = 8) and postmenopausal (n = 7) sedentary women. Selected measures of physical fitness and blood parameters were analyzed before and after the program. Besides the well-known effects of TC on balance, flexibility, and maximum leg extensor strength, TC (1) increased erythrocyte glutathione peroxidase activity—an aerobic training-responsive antioxidant enzyme—and plasma total antioxidant status and (2) decreased plasma total homocysteine, a cardiovascular risk marker. In addition to being a low-velocity, low-impact, and relatively safe, TC is a suitable physical activity design for pre- and postmenopausal women to increase antioxidant defenses. Investigating breathing effects during TC movements would be an interesting area for further research in diseases prevention. PMID:21584229

Effects of tai chi training on antioxidant capacity in pre- and postmenopausal women.

PubMed

Palasuwan, Attakorn; Suksom, Daroonwan; Margaritis, Irène; Soogarun, Suphan; Rousseau, Anne-Sophie

2011-04-11

The risk of oxidative stress-related metabolic diseases increases with menopause and physical inactivity. We hypothesized that an 8-week Tai Chi (TC) training program (2 sessions in class; 2 sessions at home; 1-1:15/session) would improve antioxidant capacity and reduce cardiovascular risks in both pre- (n = 8) and postmenopausal (n = 7) sedentary women. Selected measures of physical fitness and blood parameters were analyzed before and after the program. Besides the well-known effects of TC on balance, flexibility, and maximum leg extensor strength, TC (1) increased erythrocyte glutathione peroxidase activity-an aerobic training-responsive antioxidant enzyme-and plasma total antioxidant status and (2) decreased plasma total homocysteine, a cardiovascular risk marker. In addition to being a low-velocity, low-impact, and relatively safe, TC is a suitable physical activity design for pre- and postmenopausal women to increase antioxidant defenses. Investigating breathing effects during TC movements would be an interesting area for further research in diseases prevention.

Investigation of the B1 field distribution and RF power deposition in a birdcage coil as functions of the number of coil legs at 4.7 T, 7.0 T, and 11.7 T

NASA Astrophysics Data System (ADS)

Seo, Jeung-Hoon; Han, Sang-Doc; Kim, Kyoung-Nam

2015-06-01

The proper design of birdcage (BC) coils plays a very important role in the acquisition of highresolution magnetic resonance imaging (MRI) of small animals such as rodents. In this context, we investigate multiple-leg (8-, 16-, 32-, 64-, and 128-leg) BC coils operating at ultra-high fields (UHF) of 7.0 T and 11.7 T and a high-field (HF) of 4.7 T for rodent magnetic resonance imaging (MRI). Primarily, Our study comparatively examines the parameters of the radiofrequency (RF) transmission (|B1 +|)-field, the magnetic flux (|B1|)-field, and RF power deposition (RF-PD) as functions of the number of BC-coil legs via finite-difference time-domain (FDTD) calculations under realistic loading conditions with a biological phantom. In particular, the specific ratio |E/B1 +| is defined for predicting RF-PD values in different coil structures. Our results indicate that the optimal number of legs of the BC coil can be chosen for different resonance frequencies of 200 MHz, 300 MHz, and 500 MHz and that this choice can be lead to superior |B1 +|-field intensity and |B1|-field homogeneity and decreased RF-PD. We believe that our approach to determining the optimal number of legs for a BC coil can contribute to rodent MR imaging.

Effect of 7-days dry immersion in combination with mechanical stimulation of foot support zones upon resistance to fatigue of knee extensors and flexors

NASA Astrophysics Data System (ADS)

Netreba, A. I.; Khusnutdiniva, D. R.; Vinogradova, O. L.; Kozlovskaya, I. B.

2005-08-01

The aim of investigation was to reveal the effect of supportlessness in combination with artificial stimulation of foot support zones on fatigue resistance of knee extensors and flexors in static and rhythmic tests. 10 volunteers were exposed to 7 days dry immersion (DI). 4 of them were subjected to mechanical stimulation of foot support zones. 7-day DI did not evoke any changes in fatigue resistance during rhythmic contractions of knee extensors and flexors in both groups. Static test revealed significant decrease of fatigue resistance of both knee flexors and extensors. In the group with stimulation of support zones unfavorable effects of immersion were minimized for knee extensors but not for flexors. Thus support withdrawal is associated with a decrease of fatigue resistance for both knee flexors and extensors only under conditions of static tension. Artificial stimulation of support zones of the foot selectively affects the posture muscles.

The variation of the strength of neck extensor muscles and semispinalis capitis muscle size with head and neck position.

PubMed

Rezasoltani, A; Nasiri, R; Faizei, A M; Zaafari, G; Mirshahvelayati, A S; Bakhshidarabad, L

2013-04-01

Semispinalis capitis muscle (SECM) is a massive and long cervico-thoracic muscle which functions as a main head and neck extensor muscle. The aim of this study was to detect the effect of head and neck positions on the strength of neck extensor muscles and size of SECM in healthy subjects. Thirty healthy women students voluntarily participated in this study. An ultrasonography apparatus (Hitachi EUB 525) and a system of tension-meter were used to scan the right SECM at the level of third cervical spine and to measure the strength of neck extensor muscles at three head and neck positions. Neck extensor muscles were stronger in neutral than flexion or than extension positions while the size of SECM was larger in extension than neutral or than flexion position. The force generation capacity of the main neck extensor muscle was lower at two head and neck flexion and extension positions than neutral position. Copyright © 2012 Elsevier Ltd. All rights reserved.

Correlation of the Y-Balance Test with Lower-limb Strength of Adult Women

PubMed Central

Lee, Dong-Kyu; Kim, Gyoung-Mo; Ha, Sung-Min; Oh, Jae-Seop

2014-01-01

[Purpose] The purpose of this study was to elucidate the relationship between Y-balance test (YBT) distance and the lower-limb strength of adult women. [Subjects] Forty women aged 45 to 80 years volunteered for this study. [Methods] The participants were tested for maximal muscle strength of the lower limbs (hip extensors, hip flexors, hip abductors, knee extensors, knee flexors, and ankle dorsiflexors) and YBT distances in the anterior, posteromedial, and posterolateral directions. Pearson’s correlation coefficient was used to quantify the linear relationships between YBT distances and lower-limb strength. [Results] Hip extensor and knee flexor strength were positively correlated with YBT anterior distance. Hip extensor, hip abductor, and knee flexor strength were positively correlated with the YBT posteromedial distance. Hip extensor and knee flexor strength were positively correlated with YBT posterolateral distance. [Conclusion] There was a weak correlation between lower-limb strength (hip extensors, hip abductors, and knee flexors) and dynamic postural control as measured by the YBT. PMID:24926122

The effects of passive leg press training on jumping performance, speed, and muscle power.

PubMed

Liu, Chiang; Chen, Chuan-Shou; Ho, Wei-Hua; Füle, Róbert János; Chung, Pao-Hung; Shiang, Tzyy-Yuang

2013-06-01

Passive leg press (PLP) training was developed based on the concepts of the stretch-shortening cycle (SSC) and the benefits of high muscle contraction velocity. Passive leg press training enables lower limb muscle groups to apply a maximum downward force against a platform moved up and down at high frequency by an electric motor. Thus, these muscle groups accomplished both concentric and eccentric isokinetic contractions in a passive, rapid, and repetitive manner. This study investigates the effects of 10 weeks of PLP training at high and low movement frequencies have on jumping performance, speed, and muscle power. The authors selected 30 college students who had not performed systematic resistance training in the previous 6 months, including traditional resistance training at a squat frequency of 0.5 Hz, PLP training at a low frequency of 0.5 Hz, and PLP training at a high frequency of 2.5 Hz, and randomly divided them into 3 groups (n = 10). The participants' vertical jump, drop jump, 30-m sprint performance, explosive force, and SSC efficiency were tested under the same experimental procedures at pre- and post-training. Results reveal that high-frequency PLP training significantly increased participants' vertical jump, drop jump, 30-m sprint performance, instantaneous force, peak power, and SSC efficiency (p < 0.05). Additionally, their change rate abilities were substantially superior to those of the traditional resistance training (p < 0.05). The low-frequency PLP training significantly increased participants' vertical jump, 30-m sprint performance, instantaneous force, and peak power (p < 0.05). However, traditional resistance training only increased participants' 30-m sprint performance and peak power (p < 0.05). The findings suggest that jump performance, speed, and muscle power significantly improved after 10 weeks of PLP training at high movement frequency. A PLP training machine powered by an electrical motor enables muscles of the lower extremities to contract faster compared with voluntary contraction. Therefore, muscle training with high contraction velocity is one of the main methods of increasing muscle power. Passive leg press training is a unique method for enhancing jump performance, speed, and muscle power.

Anthropometric and physiological profiles of active blind Malaysian males.

PubMed

Singh, R; Singh, H J

1993-12-01

Cardiopulmonary capacities of twelve adults (aged between 14 to 44 years) with varying degrees of blindness engaged in regular recreational activities were compared with twelve age-matched normal sighted healthy males (control group) who were also involved in regular recreational activities. Maximum oxygen consumption (VO2max) was measured directly during exhaustive exercise test on a cycle ergometer. Forced vital capacity, leg strength and power were determined by spirometry, standing long jump and vertical jump respectively. No significant differences in VO2max, forced vital capacity and leg strength and power were observed between the blind and the control groups. No anthropometric differences were evident between the two groups. The results show therefore that the visually handicapped who are active can have a similar level of physical fitness, lung function and explosive leg strength as those of their active sighted counterparts.

Effects of Heavy Strength Training on Running Performance and Determinants of Running Performance in Female Endurance Athletes

PubMed Central

Vikmoen, Olav; Raastad, Truls; Seynnes, Olivier; Bergstrøm, Kristoffer; Ellefsen, Stian; Rønnestad, Bent R.

2016-01-01

Purpose The purpose of the current study was to investigate the effects of adding strength training to normal endurance training on running performance and running economy in well-trained female athletes. We hypothesized that the added strength training would improve performance and running economy through altered stiffness of the muscle-tendon complex of leg extensors. Methods Nineteen female endurance athletes [maximal oxygen consumption (VO2max): 53±3 ml∙kg-1∙min-1, 5.8 h weekly endurance training] were randomly assigned to either normal endurance training (E, n = 8) or normal endurance training combined with strength training (E+S, n = 11). The strength training consisted of four leg exercises [3 x 4–10 repetition maximum (RM)], twice a week for 11 weeks. Muscle strength, 40 min all-out running distance, running performance determinants and patellar tendon stiffness were measured before and after the intervention. Results E+S increased 1RM in leg exercises (40 ± 15%) and maximal jumping height in counter movement jump (6 ± 6%) and squat jump (9 ± 7%, p < 0.05). This was accompanied by increased muscle fiber cross sectional area of both fiber type I (13 ± 7%) and fiber type II (31 ± 20%) in m. vastus lateralis (p < 0.05), with no change in capillary density in m. vastus lateralis or the stiffness of the patellar tendon. Neither E+S nor E changed running economy, fractional utilization of VO2max or VO2max. There were also no change in running distance during a 40 min all-out running test in neither of the groups. Conclusion Adding heavy strength training to endurance training did not affect 40 min all-out running performance or running economy compared to endurance training only. PMID:26953893

Combined creatine and protein supplementation in conjunction with resistance training promotes muscle GLUT-4 content and glucose tolerance in humans.

PubMed

Derave, Wim; Eijnde, Bert O; Verbessem, Patricia; Ramaekers, Monique; Van Leemputte, Mark; Richter, Erik A; Hespel, Peter

2003-05-01

The present study was undertaken to explore the effects of creatine and creatine plus protein supplementation on GLUT-4 and glycogen content of human skeletal muscle. This was investigated in muscles undergoing a decrease (immobilization) and subsequent increase (resistance training) in activity level, compared with muscles with unaltered activity pattern. A double-blind, placebo-controlled trial was performed by 33 young healthy subjects. The subjects' right legs were immobilized with a cast for 2 wk, followed by a 6-wk resistance training program for the right knee extensor muscles. The participants were supplemented throughout the study with either placebo (Pl group) or creatine (Cr group) or with creatine during immobilization and creatine plus protein during retraining (Cr+P group). Needle biopsies were bilaterally taken from the vastus lateralis. GLUT-4 protein expression was reduced by the immobilization in all groups (P < 0.05). During retraining, GLUT-4 content increased (P < 0.05) in both Cr (+24%) and Cr+P (+33%), which resulted in higher posttraining GLUT-4 expression compared with Pl (P < 0.05). Compared with Pl, muscle glycogen content was higher (P < 0.05) in the trained leg in both Cr and Cr+P. Supplements had no effect on GLUT-4 expression or glycogen content in contralateral control legs. Area under the glucose curve during the oral glucose tolerance test was decreased from 232 +/- 23 mmol. l(-1). min(-1) at baseline to 170 +/- 23 mmol. l(-1). min(-1) at the end of the retraining period in Cr+P (P < 0.05), but it did not change in Cr or Pl. We conclude that creatine intake stimulates GLUT-4 and glycogen content in human muscle only when combined with changes in habitual activity level. Furthermore, combined protein and creatine supplementation improved oral glucose tolerance, which is supposedly unrelated to the changes in muscle GLUT-4 expression.

The dependence of divertor power sharing on magnetic flux balance in near double-null configurations on Alcator C-Mod

NASA Astrophysics Data System (ADS)

Brunner, D.; Kuang, A. Q.; LaBombard, B.; Terry, J. L.

2018-07-01

Management of power exhaust will be a crucial task for tokamak fusion reactors. Reactor concepts are often proposed with double-null divertors, i.e. having two magnetic separatrices in an up-down symmetric configuration. This arrangement is potentially advantageous since the majority of the tokamak exhaust power tends to flow to the outer pair of divertor legs at large major radius, where the geometry is favorable for spreading the heat over a large surface area and there is more room for advanced divertor configurations. Despite the importance, there have been relatively few studies of divertor power sharing in near double null configurations and no studies at the poloidal magnetic fields and scrape-off layer power widths anticipated for a reactor. Motivated by this need we have undertaken a systematic study on Alcator C-Mod, examining the effect of magnetic flux balance on the power sharing among the four divertor legs in near double-null plasmas. Ohmic L-modes at three values of plasma current and ICRF-heated enhanced D-alpha (EDA) H-modes and I-modes at a single value of plasma current are explored, producing poloidal magnetic fields of 0.42, 0.62 and 0.85 Tesla. For Ohmic L-modes and ICRF-heated EDA H-modes, we find that the point of equal power sharing between upper and lower divertors occurs remarkably close to a balanced double null. Power sharing amongst the outer (upper versus lower) and inner (upper versus lower) pairs of divertors can be described in terms of a logistic function of magnetic flux balance, consistent with heat flux mapping along magnetic field lines to the outer midplane. Power sharing between inner and outer legs is found to follow a Gaussian-like function of magnetic flux balance with non-zero power to the inner divertors at double null. The overall behavior of H-modes operated near double null and for I-modes operating to within one heat flux e-folding of double null are found similar to Ohmic L-modes, with a significant reduction of power on the inner divertor legs. The results are encapsulated in terms of empirically-informed analytic functions of magnetic flux balance. When combined with magnetic equilibrium control system specifications, these relationships can be used to specify the power flux handling requirements for each of the four divertor target plates.

Relationships and Predictive Capabilities of Jump Assessments to Soccer-Specific Field Test Performance in Division I Collegiate Players

PubMed Central

Lockie, Robert G.; Stage, Alyssa A.; Stokes, John J.; Orjalo, Ashley J.; Davis, DeShaun L.; Giuliano, Dominic V.; Moreno, Matthew R.; Risso, Fabrice G.; Lazar, Adrina; Birmingham-Babauta, Samantha A.; Tomita, Tricia M.

2016-01-01

Leg power is an important characteristic for soccer, and jump tests can measure this capacity. Limited research has analyzed relationships between jumping and soccer-specific field test performance in collegiate male players. Nineteen Division I players completed tests of: leg power (vertical jump (VJ), standing broad jump (SBJ), left- and right-leg triple hop (TH)); linear (30 m sprint; 0–5 m, 5–10 m, 0–10, 0–30 m intervals) and change-of-direction (505) speed; soccer-specific fitness (Yo-Yo Intermittent Recovery Test Level 2); and 7 × 30-m sprints to measure repeated-sprint ability (RSA; total time (TT), performance decrement (PD)). Pearson’s correlations (r) determined jump and field test relationships; stepwise regression ascertained jump predictors of the tests (p < 0.05). All jumps correlated with the 0–5, 0–10, and 0–30 m sprint intervals (r = −0.65–−0.90). VJ, SBJ, and left- and right-leg TH correlated with RSA TT (r = −0.51–−0.59). Right-leg TH predicted the 0–5 and 0–10 m intervals (R2 = 0.55–0.81); the VJ predicted the 0–30 m interval and RSA TT (R2 = 0.41–0.84). Between-leg TH asymmetry correlated with and predicted left-leg 505 and RSA PD (r = −0.68–0.62; R2 = 0.39–0.46). Improvements in jumping ability could contribute to faster speed and RSA performance in collegiate soccer players. PMID:29910304

Assessment of transfemoral amputees using a passive microprocessor-controlled knee versus an active powered microprocessor-controlled knee for level walking.

PubMed

Creylman, Veerle; Knippels, Ingrid; Janssen, Paul; Biesbrouck, Evelyne; Lechler, Knut; Peeraer, Louis

2016-12-19

In transfemoral (TF) amputees, the forward propulsion of the prosthetic leg in swing has to be mainly carried out by hip muscles. With hip strength being the strongest predictor to ambulation ability, an active powered knee joint could have a positive influence, lowering hip loading and contributing to ambulation mobility. To assess this, gait of four TF amputees was measured for level walking, first while using a passive microprocessor-controlled prosthetic knee (P-MPK), subsequently while using an active powered microprocessor-controlled prosthetic knee (A-MPK). Furthermore, to assess long-term effects of the use of an A-MPK, a 4-weeks follow-up case study was performed. The kinetics and kinematics of the gait of four TF amputees were assessed while walking with subsequently the P-MPK and the A-MPK. For one amputee, a follow-up study was performed: he used the A-MPK for 4 weeks, his gait was measured weekly. The range of motion of the knee was higher on both the prosthetic and the sound leg in the A-MPK compared to the P-MPK. Maximum hip torque (HT) during early stance increased for the prosthetic leg and decreased for the sound leg with the A-MPK compared to the P-MPK. During late stance, the maximum HT decreased for the prosthetic leg. The difference between prosthetic and sound leg for HT disappeared when using the A-MPK. Also, an increase in stance phase duration was observed. The follow-up study showed an increase in confidence with the A-MPK over time. Results suggested that, partially due to an induced knee flexion during stance, HT can be diminished when walking with the A-MPK compared to the P-MPK. The single case follow-up study showed positive trends indicating that an adaptation time is beneficial for the A-MPK.

Function and structure of the deep cervical extensor muscles in patients with neck pain.

PubMed

Schomacher, Jochen; Falla, Deborah

2013-10-01

The deep cervical extensors are anatomically able to control segmental movements of the cervical spine in concert with the deep cervical flexors. Several investigations have confirmed changes in cervical flexor muscle control in patients with neck pain and as a result, effective evidence-based therapeutic exercises have been developed to address such dysfunctions. However, knowledge on how the deep extensor muscles behave in patients with neck pain disorders is scare. Structural changes such as higher concentration of fat within the muscle, variable cross-sectional area and higher proportions of type II fibres have been observed in the deep cervical extensors of patients with neck pain compared to healthy controls. These findings suggest that the behaviour of the deep extensors may be altered in patients with neck pain. Consistent with this hypothesis, a recent series of studies confirm that patients display reduced activation of the deep cervical extensors as well as less defined activation patterns. This article provides an overview of the various different structural and functional changes in the deep neck extensor muscles documented in patients with neck pain. Relevant recommendations for the management of muscle dysfunction in patients with neck pain are presented. Copyright © 2013 Elsevier Ltd. All rights reserved.

Interconnect patterns for printed organic thermoelectric devices with large fill factors

NASA Astrophysics Data System (ADS)

Gordiz, Kiarash; Menon, Akanksha K.; Yee, Shannon K.

2017-09-01

Organic materials can be printed into thermoelectric (TE) devices for low temperature energy harvesting applications. The output voltage of printed devices is often limited by (i) small temperature differences across the active materials attributed to small leg lengths and (ii) the lower Seebeck coefficient of organic materials compared to their inorganic counterparts. To increase the voltage, a large number of p- and n-type leg pairs is required for organic TEs; this, however, results in an increased interconnect resistance, which then limits the device output power. In this work, we discuss practical concepts to address this problem by positioning TE legs in a hexagonal closed-packed layout. This helps achieve higher fill factors (˜91%) than conventional inorganic devices (˜25%), which ultimately results in higher voltages and power densities due to lower interconnect resistances. In addition, wiring the legs following a Hilbert spacing-filling pattern allows for facile load matching to each application. This is made possible by leveraging the fractal nature of the Hilbert interconnect pattern, which results in identical sub-modules. Using the Hilbert design, sub-modules can better accommodate non-uniform temperature distributions because they naturally self-localize. These device design concepts open new avenues for roll-to-roll printing and custom TE module shapes, thereby enabling organic TE modules for self-powered sensors and wearable electronic applications.

Wake characteristics of an eight-leg tower for a MOD-0 type wind turbine

NASA Technical Reports Server (NTRS)

Savino, J. M.; Wagner, L. H.; Sinclair, D.

1977-01-01

Low speed wind tunnel tests were conducted to determine the flow characteristics of the wake downwind of a 1/25th scale, all tubular eight leg tower concept suitable for application to the DOE-NASA MOD-0 wind power turbine. Measurements were made of wind speed profiles, and from these were determined the wake local minimum velocity, average velocity, and width for several wind approach angles. These data are presented herein along with tower shadow photographs and comparisons with data from an earlier lattice type, four leg tower model constructed of tubular members. Values of average wake velocity defect ratio and average ratio of wake width to blade radius for the eight leg model were estimated to be around 0.17 and 0.30, respectively, at the plane of the rotor blade. These characteristics suggest that the tower wake of the eight leg concept is slightly less than that of the four leg design.

A simple rule for quadrupedal gait generation determined by leg loading feedback: a modeling study

PubMed Central

Fukuoka, Yasuhiro; Habu, Yasushi; Fukui, Takahiro

2015-01-01

We discovered a specific rule for generating typical quadrupedal gaits (the order of the movement of four legs) through a simulated quadrupedal locomotion, in which unprogrammed gaits (diagonal/lateral sequence walks, left/right-lead canters, and left/right-lead transverse gallops) spontaneously emerged because of leg loading feedbacks to the CPGs hard-wired to produce a default trot. Additionally, all gaits transitioned according to speed, as seen in animals. We have therefore hypothesized that various gaits derive from a trot because of posture control through leg loading feedback. The body tilt on the two support legs of each diagonal pair during trotting was classified into three types (level, tilted up, or tilted down) according to speed. The load difference between the two legs led to the phase difference between their CPGs via the loading feedbacks, resulting in nine gaits (32: three tilts to the power of two diagonal pairs) including the aforementioned. PMID:25639661

Effects of unilateral and bilateral plyometric training on power and jumping ability in women.

PubMed

Makaruk, Hubert; Winchester, Jason B; Sadowski, Jerzy; Czaplicki, Adam; Sacewicz, Tomasz

2011-12-01

Makaruk, H, Winchester, JB, Sadowski, J, Czaplicki, A, and Sacewicz, T. Effects of unilateral and bilateral plyometric training on power and jumping ability in women. J Strength Cond Res 25(12): 3311-3318, 2011-The purpose of this study was to examine the effects of unilateral and bilateral plyometric exercise on peak power and jumping performance during different stages of a 12-week training and detraining in women. Forty-nine untrained but physically active female college students were randomly assigned to 1 of 3 groups: unilateral plyometric group (n = 16), bilateral plyometric group (BLE; n = 18), and a control group (n = 15). Peak power and jumping ability were assessed by means of the alternate leg tests (10-second Wingate test and 5 alternate leg bounds), bilateral leg test (countermovement jump [CMJ]) and unilateral leg test (unilateral CMJ). Performance indicators were measured pretraining, midtraining, posttraining, and detraining. Differences between dependent variables were assessed with a 3 × 4 (group × time) repeated analysis of variance with Tukey's post hoc test applied where appropriate. Effect size was calculated to determine the magnitude of significant differences between the researched parameters. Only the unilateral plyometric training produced significant (p < 0.05) improvement in all tests from pretraining to midtraining, but there was no significant (p < 0.05) increase in performance indicators from midtraining to posttraining. The BLE group significantly (p < 0.05) improved in all tests from pretraining to posttraining and did not significantly (p > 0.05) decrease power and jumping ability in all tests during detraining. These results suggest that unilateral plyometric exercises produce power and jumping performance during a shorter period when compared to bilateral plyometric exercises but achieved performance gains last longer after bilateral plyometric training. Practitioners should consider the inclusion of both unilateral and bilateral modes of plyometric exercise to elicit rapid improvements and guard against detraining.

Computer simulations of neural mechanisms explaining upper and lower limb excitatory neural coupling

PubMed Central

2010-01-01

Background When humans perform rhythmic upper and lower limb locomotor-like movements, there is an excitatory effect of upper limb exertion on lower limb muscle recruitment. To investigate potential neural mechanisms for this behavioral observation, we developed computer simulations modeling interlimb neural pathways among central pattern generators. We hypothesized that enhancement of muscle recruitment from interlimb spinal mechanisms was not sufficient to explain muscle enhancement levels observed in experimental data. Methods We used Matsuoka oscillators for the central pattern generators (CPG) and determined parameters that enhanced amplitudes of rhythmic steady state bursts. Potential mechanisms for output enhancement were excitatory and inhibitory sensory feedback gains, excitatory and inhibitory interlimb coupling gains, and coupling geometry. We first simulated the simplest case, a single CPG, and then expanded the model to have two CPGs and lastly four CPGs. In the two and four CPG models, the lower limb CPGs did not receive supraspinal input such that the only mechanisms available for enhancing output were interlimb coupling gains and sensory feedback gains. Results In a two-CPG model with inhibitory sensory feedback gains, only excitatory gains of ipsilateral flexor-extensor/extensor-flexor coupling produced reciprocal upper-lower limb bursts and enhanced output up to 26%. In a two-CPG model with excitatory sensory feedback gains, excitatory gains of contralateral flexor-flexor/extensor-extensor coupling produced reciprocal upper-lower limb bursts and enhanced output up to 100%. However, within a given excitatory sensory feedback gain, enhancement due to excitatory interlimb gains could only reach levels up to 20%. Interconnecting four CPGs to have ipsilateral flexor-extensor/extensor-flexor coupling, contralateral flexor-flexor/extensor-extensor coupling, and bilateral flexor-extensor/extensor-flexor coupling could enhance motor output up to 32%. Enhancement observed in experimental data exceeded 32%. Enhancement within this symmetrical four-CPG neural architecture was more sensitive to relatively small interlimb coupling gains. Excitatory sensory feedback gains could produce greater output amplitudes, but larger gains were required for entrainment compared to inhibitory sensory feedback gains. Conclusions Based on these simulations, symmetrical interlimb coupling can account for much, but not all of the excitatory neural coupling between upper and lower limbs during rhythmic locomotor-like movements. PMID:21143960

Validity and test–retest reliability of a novel simple back extensor muscle strength test

PubMed Central

Harding, Amy T; Weeks, Benjamin Kurt; Horan, Sean A; Little, Andrew; Watson, Steven L; Beck, Belinda Ruth

2017-01-01

Objectives: To develop and determine convergent validity and reliability of a simple and inexpensive clinical test to quantify back extensor muscle strength. Methods: Two testing sessions were conducted, 7 days apart. Each session involved three trials of standing maximal isometric back extensor muscle strength using both the novel test and isokinetic dynamometry. Lumbar spine bone mineral density was examined by dual-energy X-ray absorptiometry. Validation was examined with Pearson correlations (r). Test–retest reliability was examined with intraclass correlation coefficients and limits of agreement. Pearson correlations and intraclass correlation coefficients are presented with corresponding 95% confidence intervals. Linear regression was used to examine the ability of peak back extensor muscle strength to predict indices of lumbar spine bone mineral density and strength. Results: A total of 52 healthy adults (26 men, 26 women) aged 46.4 ± 20.4 years were recruited from the community. A strong positive relationship was observed between peak back extensor strength from hand-held and isokinetic dynamometry (r = 0.824, p < 0.001). For the novel back extensor strength test, short- and long-term reliability was excellent (intraclass correlation coefficient = 0.983 (95% confidence interval, 0.971–0.990), p < 0.001 and intraclass correlation coefficient = 0.901 (95% confidence interval, 0.833–0.943), p < 0.001, respectively). Limits of agreement for short-term repeated back extensor strength measures with the novel back extensor strength protocol were −6.63 to 7.70 kg, with a mean bias of +0.71 kg. Back extensor strength predicted 11% of variance in lumbar spine bone mineral density (p < 0.05) and 9% of lumbar spine index of bone structural strength (p < 0.05). Conclusion: Our novel hand-held dynamometer method to determine back extensor muscle strength is quick, relatively inexpensive, and reliable; demonstrates initial convergent validity in a healthy population; and is associated with bone mass at a clinically important site. PMID:28255442

Prosthetic Leg Control in the Nullspace of Human Interaction.

PubMed

Gregg, Robert D; Martin, Anne E

2016-07-01

Recent work has extended the control method of virtual constraints, originally developed for autonomous walking robots, to powered prosthetic legs for lower-limb amputees. Virtual constraints define desired joint patterns as functions of a mechanical phasing variable, which are typically enforced by torque control laws that linearize the output dynamics associated with the virtual constraints. However, the output dynamics of a powered prosthetic leg generally depend on the human interaction forces, which must be measured and canceled by the feedback linearizing control law. This feedback requires expensive multi-axis load cells, and actively canceling the interaction forces may minimize the human's influence over the prosthesis. To address these limitations, this paper proposes a method for projecting virtual constraints into the nullspace of the human interaction terms in the output dynamics. The projected virtual constraints naturally render the output dynamics invariant with respect to the human interaction forces, which instead enter into the internal dynamics of the partially linearized prosthetic system. This method is illustrated with simulations of a transfemoral amputee model walking with a powered knee-ankle prosthesis that is controlled via virtual constraints with and without the proposed projection.

An Ultralightweight and Living Legged Robot.

PubMed

Vo Doan, Tat Thang; Tan, Melvin Y W; Bui, Xuan Hien; Sato, Hirotaka

2018-02-01

In this study, we describe the most ultralightweight living legged robot to date that makes it a strong candidate for a search and rescue mission. The robot is a living beetle with a wireless electronic backpack stimulator mounted on its thorax. Inheriting from the living insect, the robot employs a compliant body made of soft actuators, rigid exoskeletons, and flexure hinges. Such structure would allow the robot to easily adapt to any complex terrain due to the benefit of soft interface, self-balance, and self-adaptation of the insect without any complex controller. The antenna stimulation enables the robot to perform not only left/right turning but also backward walking and even cessation of walking. We were also able to grade the turning and backward walking speeds by changing the stimulation frequency. The power required to drive the robot is low as the power consumption of the antenna stimulation is in the order of hundreds of microwatts. In contrast to the traditional legged robots, this robot is of low cost, easy to construct, simple to control, and has ultralow power consumption.

Differences in physical fitness and throwing velocity among elite and amateur male handball players.

PubMed

Gorostiaga, E M; Granados, C; Ibáñez, J; Izquierdo, M

2005-04-01

This study compared physical characteristics (body height, body mass [BM], body fat [BF], and free fatty mass [FFM]), one repetition maximum bench-press (1RM (BP)), jumping explosive strength (VJ), handball throwing velocity, power-load relationship of the leg and arm extensor muscles, 5- and 15-m sprint running time, and running endurance in two handball male teams: elite team, one of the world's leading teams (EM, n = 15) and amateur team, playing in the Spanish National Second Division (AM, n = 15). EM had similar values in body height, BF, VJ, 5- and 15-m sprint running time and running endurance than AM. However, the EM group gave higher values in BM (95.2 +/- 13 kg vs. 82.4 +/- 10 kg, p < 0.05), FFM (81.7 +/- 9 kg vs. 72.4 +/- 7 kg, p < 0.05), 1RM (BP) (107 +/- 12 kg vs. 83 +/- 10 kg, p < 0.001), muscle power during bench-press (18 - 21 %, p < 0.05) and half squat (13 - 17 %), and throwing velocities at standing (23.8 +/- 1.9 m . s (-1) vs. 21.8 +/- 1.6 m . s (-1), p < 0.05) and 3-step running (25.3 +/- 2.2 m . s (-1) vs. 22.9 +/- 1.4 m . s (-1), p < 0.05) actions than the AM group. Significant correlations (r = 0.67 - 0.71, p < 0.05 - 0.01) were observed in EM and AM between individual values of velocity at 30 % of 1RM (BP) and individual values of ball velocity during a standing throw. Significant correlations were observed in EM, but not in AM, between the individual values of velocity during 3-step running throw and the individual values of velocity at 30 % of 1RM (BP) (r = 0.72, p < 0.05), as well as the individual values of power at 100 % of body mass during half-squat actions (r = 0.62, p < 0.05). The present results suggest that more muscular and powerful players are at an advantage in handball. The differences observed in free fatty mass could partly explain the differences observed between groups in absolute maximal strength and muscle power. In EM, higher efficiency in handball throwing velocity may be associated with both upper and lower extremity power output capabilities, whereas in AM this relationship may be different. Endurance capacity does not seem to represent a limitation for elite performance in handball.

Ultrasound definition of tendon damage in patients with rheumatoid arthritis. Results of a OMERACT consensus-based ultrasound score focussing on the diagnostic reliability.

PubMed

Bruyn, George A W; Hanova, Petra; Iagnocco, Annamaria; d'Agostino, Maria-Antonietta; Möller, Ingrid; Terslev, Lene; Backhaus, Marina; Balint, Peter V; Filippucci, Emilio; Baudoin, Paul; van Vugt, Richard; Pineda, Carlos; Wakefield, Richard; Garrido, Jesus; Pecha, Ondrej; Naredo, Esperanza

2014-11-01

To develop the first ultrasound scoring system of tendon damage in rheumatoid arthritis (RA) and assess its intraobserver and interobserver reliability. We conducted a Delphi study on ultrasound-defined tendon damage and ultrasound scoring system of tendon damage in RA among 35 international rheumatologists with experience in musculoskeletal ultrasound. Twelve patients with RA were included and assessed twice by 12 rheumatologists-sonographers. Ultrasound examination for tendon damage in B mode of five wrist extensor compartments (extensor carpi radialis brevis and longus; extensor pollicis longus; extensor digitorum communis; extensor digiti minimi; extensor carpi ulnaris) and one ankle tendon (tibialis posterior) was performed blindly, independently and bilaterally in each patient. Intraobserver and interobserver reliability were calculated by κ coefficients. A three-grade semiquantitative scoring system was agreed for scoring tendon damage in B mode. The mean intraobserver reliability for tendon damage scoring was excellent (κ value 0.91). The mean interobserver reliability assessment showed good κ values (κ value 0.75). The most reliable were the extensor digiti minimi, the extensor carpi ulnaris, and the tibialis posterior tendons. An ultrasound reference image atlas of tenosynovitis and tendon damage was also developed. Ultrasound is a reproducible tool for evaluating tendon damage in RA. This study strongly supports a new reliable ultrasound scoring system for tendon damage. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Mechanical and energetic consequences of reduced ankle plantar-flexion in human walking

PubMed Central

Huang, Tzu-wei P.; Shorter, Kenneth A.; Adamczyk, Peter G.; Kuo, Arthur D.

2015-01-01

ABSTRACT The human ankle produces a large burst of ‘push-off’ mechanical power late in the stance phase of walking, reduction of which leads to considerably poorer energy economy. It is, however, uncertain whether the energetic penalty results from poorer efficiency when the other leg joints substitute for the ankle's push-off work, or from a higher overall demand for work due to some fundamental feature of push-off. Here, we show that greater metabolic energy expenditure is indeed explained by a greater demand for work. This is predicted by a simple model of walking on pendulum-like legs, because proper push-off reduces collision losses from the leading leg. We tested this by experimentally restricting ankle push-off bilaterally in healthy adults (N=8) walking on a treadmill at 1.4 m s−1, using ankle–foot orthoses with steel cables limiting motion. These produced up to ∼50% reduction in ankle push-off power and work, resulting in up to ∼50% greater net metabolic power expenditure to walk at the same speed. For each 1 J reduction in ankle work, we observed 0.6 J more dissipative collision work by the other leg, 1.3 J more positive work from the leg joints overall, and 3.94 J more metabolic energy expended. Loss of ankle push-off required more positive work elsewhere to maintain walking speed; this additional work was performed by the knee, apparently at reasonably high efficiency. Ankle push-off may contribute to walking economy by reducing dissipative collision losses and thus overall work demand. PMID:26385330

Mechanical and energetic consequences of reduced ankle plantar-flexion in human walking.

PubMed

Huang, Tzu-wei P; Shorter, Kenneth A; Adamczyk, Peter G; Kuo, Arthur D

2015-11-01

The human ankle produces a large burst of 'push-off' mechanical power late in the stance phase of walking, reduction of which leads to considerably poorer energy economy. It is, however, uncertain whether the energetic penalty results from poorer efficiency when the other leg joints substitute for the ankle's push-off work, or from a higher overall demand for work due to some fundamental feature of push-off. Here, we show that greater metabolic energy expenditure is indeed explained by a greater demand for work. This is predicted by a simple model of walking on pendulum-like legs, because proper push-off reduces collision losses from the leading leg. We tested this by experimentally restricting ankle push-off bilaterally in healthy adults (N=8) walking on a treadmill at 1.4 m s(-1), using ankle-foot orthoses with steel cables limiting motion. These produced up to ∼50% reduction in ankle push-off power and work, resulting in up to ∼50% greater net metabolic power expenditure to walk at the same speed. For each 1 J reduction in ankle work, we observed 0.6 J more dissipative collision work by the other leg, 1.3 J more positive work from the leg joints overall, and 3.94 J more metabolic energy expended. Loss of ankle push-off required more positive work elsewhere to maintain walking speed; this additional work was performed by the knee, apparently at reasonably high efficiency. Ankle push-off may contribute to walking economy by reducing dissipative collision losses and thus overall work demand. © 2015. Published by The Company of Biologists Ltd.

The Effect of Increasing Jump Steps on Stance Leg Joint Kinetics in Bounding.

PubMed

Kariyama, Yasushi; Hobara, Hiroaki; Zushi, Koji

2018-06-20

Jump distance per step in bounding exercises from the standing position increases with increasing number of steps. We examined the hypothesis that the joint kinetic variables of the stance leg would also increase accordingly. Eleven male athletes (sprinters and jumpers) performed bounding exercise, starting from the double-leg standing posture, and covered the longest distance possible by performing a series of seven forward alternating single-leg jumps. Kinematic and kinetic data were calculated using the data by a motion capture system and force platforms. Hip extension joint work were decreased at third step (1 st : 1.07±0.22, 3 rd : 0.45±0.15, 5 th : 0.47±0.14 J•kg -1 ; partial η 2 : 0.86), and hip abduction joint power were increased (1 st : 7.53±3.29, 3 rd : 13.50±4.44, 5 th : 21.37±9.93 W•kg -1 ; partial η 2 : 0.58); the knee extension joint power were increased until the third step (1 st : 14.43±4.94, 3 rd : 17.13±3.59, 5 th : 14.28±2.86 W•kg -1 ; partial η 2 : 0.29), and ankle plantar flexion joint power increased (1 st : 34.14±5.33, 3 rd : 37.46±4.45, 5 th : 40.11±5.66 W•kg -1 ; partial η 2 : 0.53). These results contrast with our hypothesis, and indicate that increasing the jump distance during bounding exercises is not necessarily accompanied by increases in joint kinetics of stance leg. Moreover, changes in joint kinetics vary at different joints and anatomical axes. © Georg Thieme Verlag KG Stuttgart · New York.

Biomechanical Characteristics and Determinants of Instep Soccer Kick

PubMed Central

Kellis, Eleftherios; Katis, Athanasios

2007-01-01

Good kicking technique is an important aspect of a soccer player. Therefore, understanding the biomechanics of soccer kicking is particularly important for guiding and monitoring the training process. The purpose of this review was to examine latest research findings on biomechanics of soccer kick performance and identify weaknesses of present research which deserve further attention in the future. Being a multiarticular movement, soccer kick is characterised by a proximal-to-distal motion of the lower limb segments of the kicking leg. Angular velocity is maximized first by the thigh, then by the shank and finally by the foot. This is accomplished by segmental and joint movements in multiple planes. During backswing, the thigh decelerates mainly due to a motion-dependent moment from the shank and, to a lesser extent, by activation of hip muscles. In turn, forward acceleration of the shank is accomplished through knee extensor moment as well as a motion-dependent moment from the thigh. The final speed, path and spin of the ball largely depend on the quality of foot-ball contact. Powerful kicks are achieved through a high foot velocity and coefficient of restitution. Preliminary data indicate that accurate kicks are achieved through slower kicking motion and ball speed values. Key pointsSoccer kick is achieved through segmental and joint rotations in multiple planes and via the proximal-to-distal sequence of segmental angular velocities until ball impact. The quality of ball - foot impact and the mechanical behavior of the foot are also important determinants of the final speed, path and spin of the ball.Ball speed values during the maximum instep kick range from 18 to 35 msec-1 depending on various factors, such as skill level, age, approach angle and limb dominance.The main bulk of biomechanics research examined the biomechanics of powerful kicks, mostly under laboratory conditions. A powerful kick is characterized by the achievement of maximal ball speed. However, maximal ball speed does not guarantee a successful kick: in each case, the ball must reach the target. As already explained, when the player is instructed to hit the ball accurately, joint and segment velocities are lower as opposed to a fast and powerful kick performance. It is therefore apparent that future research should focus on biomechanics of fast but accurate kicking. PMID:24149324

Long-term outcomes following plate stabilization to address spontaneous luxation of the long digital extensor tendon of origin in 2 dogs.

PubMed

Hasiuk, Michelle M M; Drygas, Kevin A; Lewis, Daniel D

2017-11-01

Two dogs with spontaneous luxation of the long digital extensor tendon of origin were managed by performing a sulcoplasty and applying a plate bridging the extensor sulcus. Lameness resolved and neither dog had recurrence of lameness 59 and 15 months following surgery.

Pedicled unipolar latissimus dorsi flap for reconstruction of finger extensor *

PubMed Central

Takahashi, Mitsuhiko; Kasai, Tokio; Hibino, Naohito; Ishii, Seiji; Mitsuhashi, Tadashi

2017-01-01

Abstract We describe the use of a pedicled unipolar latissimus dorsi flap to restore finger extension. The patient had large defects in the radial nerve and extensor musculature. A long-tailed, 50-cm-long flap was prepared, which enabled the end of the flap to be sutured to the extensor digitorum. PMID:28470032

Effects of strength training program on hip extensors and knee extensors strength of lower limb in children with spastic diplegic cerebral palsy.

PubMed

Aye, Thanda; Thein, Soe; Hlaing, Thaingi

2016-01-01

[Purpose] The purpose of this study was to determine whether strength training programs for hip extensors and knee extensors improve gross motor function of children with cerebral palsy in Myanmar. [Subjects and Methods] Forty children (25 boys and 15 girls, mean age: 6.07 ± 2.74 years) from National Rehabilitation Hospital, Yangon, Myanmar, who had been diagnosed with spastic diplegic cerebral palsy, Gross Motor Classification System I and II participated in a 6-week strength training program (45 minutes per day, 3 days per week) on hip and knee extensors. Assessment was made, before and after intervention, of the amount of training weight in pounds, as well as Gross Motor Function Measure (GMFM) dimensions D (standing) and E (walking, running, jumping). [Results] All scores had increased significantly after the strength-training program. [Conclusion] A simple method of strength-training program for hip and knee extensors might lead to improved muscle strength and gross motor function in children with spastic diplegic cerebral palsy.

Effects of strength training program on hip extensors and knee extensors strength of lower limb in children with spastic diplegic cerebral palsy

PubMed Central

Aye, Thanda; Thein, Soe; Hlaing, Thaingi

2016-01-01

[Purpose] The purpose of this study was to determine whether strength training programs for hip extensors and knee extensors improve gross motor function of children with cerebral palsy in Myanmar. [Subjects and Methods] Forty children (25 boys and 15 girls, mean age: 6.07 ± 2.74 years) from National Rehabilitation Hospital, Yangon, Myanmar, who had been diagnosed with spastic diplegic cerebral palsy, Gross Motor Classification System I and II participated in a 6-week strength training program (45 minutes per day, 3 days per week) on hip and knee extensors. Assessment was made, before and after intervention, of the amount of training weight in pounds, as well as Gross Motor Function Measure (GMFM) dimensions D (standing) and E (walking, running, jumping). [Results] All scores had increased significantly after the strength-training program. [Conclusion] A simple method of strength-training program for hip and knee extensors might lead to improved muscle strength and gross motor function in children with spastic diplegic cerebral palsy. PMID:27065561

GABAergic inhibition of leg motoneurons is required for normal walking behavior in freely moving Drosophila

PubMed Central

Gowda, Swetha B. M.; Paranjpe, Pushkar D.; Reddy, O. Venkateswara; Thiagarajan, Devasena; Palliyil, Sudhir; Reichert, Heinrich

2018-01-01

Walking is a complex rhythmic locomotor behavior generated by sequential and periodical contraction of muscles essential for coordinated control of movements of legs and leg joints. Studies of walking in vertebrates and invertebrates have revealed that premotor neural circuitry generates a basic rhythmic pattern that is sculpted by sensory feedback and ultimately controls the amplitude and phase of the motor output to leg muscles. However, the identity and functional roles of the premotor interneurons that directly control leg motoneuron activity are poorly understood. Here we take advantage of the powerful genetic methodology available in Drosophila to investigate the role of premotor inhibition in walking by genetically suppressing inhibitory input to leg motoneurons. For this, we have developed an algorithm for automated analysis of leg motion to characterize the walking parameters of wild-type flies from high-speed video recordings. Further, we use genetic reagents for targeted RNAi knockdown of inhibitory neurotransmitter receptors in leg motoneurons together with quantitative analysis of resulting changes in leg movement parameters in freely walking Drosophila. Our findings indicate that targeted down-regulation of the GABAA receptor Rdl (Resistance to Dieldrin) in leg motoneurons results in a dramatic reduction of walking speed and step length without the loss of general leg coordination during locomotion. Genetically restricting the knockdown to the adult stage and subsets of motoneurons yields qualitatively identical results. Taken together, these findings identify GABAergic premotor inhibition of motoneurons as an important determinant of correctly coordinated leg movements and speed of walking in freely behaving Drosophila. PMID:29440493

GABAergic inhibition of leg motoneurons is required for normal walking behavior in freely moving Drosophila.

PubMed

Gowda, Swetha B M; Paranjpe, Pushkar D; Reddy, O Venkateswara; Thiagarajan, Devasena; Palliyil, Sudhir; Reichert, Heinrich; VijayRaghavan, K

2018-02-27

Walking is a complex rhythmic locomotor behavior generated by sequential and periodical contraction of muscles essential for coordinated control of movements of legs and leg joints. Studies of walking in vertebrates and invertebrates have revealed that premotor neural circuitry generates a basic rhythmic pattern that is sculpted by sensory feedback and ultimately controls the amplitude and phase of the motor output to leg muscles. However, the identity and functional roles of the premotor interneurons that directly control leg motoneuron activity are poorly understood. Here we take advantage of the powerful genetic methodology available in Drosophila to investigate the role of premotor inhibition in walking by genetically suppressing inhibitory input to leg motoneurons. For this, we have developed an algorithm for automated analysis of leg motion to characterize the walking parameters of wild-type flies from high-speed video recordings. Further, we use genetic reagents for targeted RNAi knockdown of inhibitory neurotransmitter receptors in leg motoneurons together with quantitative analysis of resulting changes in leg movement parameters in freely walking Drosophila Our findings indicate that targeted down-regulation of the GABA A receptor Rdl (Resistance to Dieldrin) in leg motoneurons results in a dramatic reduction of walking speed and step length without the loss of general leg coordination during locomotion. Genetically restricting the knockdown to the adult stage and subsets of motoneurons yields qualitatively identical results. Taken together, these findings identify GABAergic premotor inhibition of motoneurons as an important determinant of correctly coordinated leg movements and speed of walking in freely behaving Drosophila . Copyright © 2018 the Author(s). Published by PNAS.

Performance of Four-Leg VSC based DSTATCOM using Single Phase P-Q Theory

NASA Astrophysics Data System (ADS)

Jampana, Bangarraju; Veramalla, Rajagopal; Askani, Jayalaxmi

2017-02-01

This paper presents single-phase P-Q theory for four-leg VSC based distributed static compensator (DSTATCOM) in the distribution system. The proposed DSTATCOM maintains unity power factor at source, zero voltage regulation, eliminates current harmonics, load balancing and neutral current compensation. The advantage of using four-leg VSC based DSTATCOM is to eliminate isolated/non-isolated transformer connection at point of common coupling (PCC) for neutral current compensation. The elimination of transformer connection at PCC with proposed topology will reduce cost of DSTATCOM. The single-phase P-Q theory control algorithm is used to extract fundamental component of active and reactive currents for generation of reference source currents which is based on indirect current control method. The proposed DSTATCOM is modelled and the results are validated with various consumer loads under unity power factor and zero voltage regulation modes in the MATLAB R2013a environment using simpower system toolbox.

Effect of spaceflight on the isotonic contractile properties of single skeletal muscle fibers in the rhesus monkey

NASA Technical Reports Server (NTRS)

Fitts, R. H.; Romatowski, J. G.; Blaser, C.; De La Cruz, L.; Gettelman, G. J.; Widrick, J. J.

2000-01-01

Experiments from both Cosmos and Space Shuttle missions have shown weightlessness to result in a rapid decline in the mass and force of rat hindlimb extensor muscles. Additionally, despite an increased maximal shortening velocity, peak power was reduced in rat soleus muscle post-flight. In humans, declines in voluntary peak isometric ankle extensor torque ranging from 15-40% have been reported following long- and short-term spaceflight and prolonged bed rest. Complete understanding of the cellular events responsible for the fiber atrophy and the decline in force, as well as the development of effective countermeasures, will require detailed knowledge of how the physiological and biochemical processes of muscle function are altered by spaceflight. The specific purpose of this investigation was to determine the extent to which the isotonic contractile properties of the slow- and fast-twitch fiber types of the soleus and gastrocnemius muscles of rhesus monkeys (Macaca mulatta) were altered by a 14-day spaceflight.

Life-long calorie restriction in Fischer 344 rats attenuates age-related loss in skeletal muscle-specific force and reduces extracellular space.

PubMed

Payne, Anthony M; Dodd, Stephen L; Leeuwenburgh, Christiaan

2003-12-01

The decline in muscle function is associated with an age-related decrease in muscle mass and an age-related decline in strength. However, decreased strength is not solely due to decreased muscle mass. The age-related decline in muscle-specific force (force/muscle cross-sectional area), a measure of intrinsic muscle function, also contributes to age-related strength decline, and the mechanisms by which this occurs are only partially known. Moreover, changes in the extracellular space could have a profound effect on skeletal muscle function. Life-long calorie restriction in rodents has shown to be a powerful anti-aging intervention. In this study, we examine whether calorie restriction is able to attenuate the loss of muscle function and elevations in extracellular space associated with aging. We hypothesize that calorie restriction attenuates the age-associated decline in specific force and increases in extracellular space. Measurements of in vitro contractile properties of the extensor digitorum longus (type II) and soleus (type I) muscles from 12-mo and 26- to 28-mo-old ad libitum-fed, as well as 27- to 28-mo-old life-long calorie-restricted male Fischer 344 rats, were performed. We found that calorie restriction attenuated the age-associated decline in muscle mass-to-body mass ratio (mg/g) and strength-to-body mass ratio (N/kg) in the extensor digitorum longus muscle (P < 0.05) but not in the soleus muscle (P > 0.05). Importantly, muscle-specific force (N/cm2) in the extensor digitorum longus, but not in the soleus muscle, of the old calorie-restricted rats was equal to that of the young 12-mo-old animals. Moreover, the age-associated increase in extracellular space was reduced in the fast-twitch extensor digitorum longus muscle (P < 0.05) but not in the soleus muscle with calorie restriction. We also found a significant correlation between the extracellular space and the muscle-specific force in the extensor digitorum longus (r = -0.58; P < 0.05) but not in the soleus muscle (r = -0.38; P > 0.05). Hence, this study shows a loss of muscle function with age and suggests that long-term calorie restriction is an effective intervention against the loss of muscle function with age.

Effect of simultaneous stretching of the wrist and finger extensors for lateral epicondylitis: a gross anatomical study of the tendinous origins of the extensor carpi radialis brevis and extensor digitorum communis.

PubMed

Shirato, Rikiya; Wada, Takuro; Aoki, Mitsuhiro; Iba, Kousuke; Kanaya, Kohei; Fujimiya, Mineko; Yamashita, Toshihiko

2015-11-01

Pulling the wrist into flexion with the elbow in extension and forearm in pronation has been used as the stretching technique of wrist extensors for lateral epicondylitis. Simultaneous stretching of the fingers in addition to the wrist flexion has also been applied. However, the mechanism of this simultaneous stretching has not been clarified. This study is designed to clarify the mechanism underlying this simultaneous stretching technique based on the anatomical features of the origins of the extensor carpi radialis brevis (ECRB) and extensor digitorum communis (EDC). Thirty-nine arms from formalin-embalmed Japanese human specimens were dissected. The features of the origins of the ECRB and EDC were macroscopically observed, and the locations of each origin on the lateral epicondyle were measured. The ECRB had a long and wide, purely tendinous origin which originated from the anterior slope of the lateral epicondyle. The tendinous origin of the index finger of the EDC (EDC-IF) arose from the posterior aspect of the ECRB tendinous origin, with a coexisting muscular portion observed at the level of the proximal forearm. The middle finger of the EDC (EDC-MF) had a short tendinous origin with an associated muscular portion and originated proximo-laterally to the origin of the ECRB on the lateral epicondyle. In addition, the muscular origin of the EDC-MF arose on the superficial and posterior aspect of the ECRB tendinous origin. In contrast, the ring and little fingers of the EDC originated from the tendinous septum of the extensor digiti minimi and extensor carpi ulnaris, and had no connection with the ECRB tendinous origin. On the basis of our anatomical findings, simultaneous stretching of the wrist extensors by wrist, index and middle fingers flexion could provide stretching force to both the tendinous origins of the ECRB and EDC through the EDC-IF and EDC-MF.

Effects of hand configuration on muscle force coordination, co-contraction and concomitant intermuscular coupling during maximal isometric flexion of the fingers.

PubMed

Charissou, Camille; Amarantini, David; Baurès, Robin; Berton, Eric; Vigouroux, Laurent

2017-11-01

The mechanisms governing the control of musculoskeletal redundancy remain to be fully understood. The hand is highly redundant, and shows different functional role of extensors according to its configuration for a same functional task of finger flexion. Through intermuscular coherence analysis combined with hand musculoskeletal modelling during maximal isometric hand contractions, our aim was to better understand the neural mechanisms underlying the control of muscle force coordination and agonist-antagonist co-contraction. Thirteen participants performed maximal isometric flexions of the fingers in two configurations: power grip (Power) and finger-pressing on a surface (Press). Hand kinematics and force/moment measurements were used as inputs in a musculoskeletal model of the hand to determine muscular tensions and co-contraction. EMG-EMG coherence analysis was performed between wrist and finger flexors and extensor muscle pairs in alpha, beta and gamma frequency bands. Concomitantly with tailored muscle force coordination and increased co-contraction between Press and Power (mean difference: 48.08%; p < 0.05), our results showed muscle-pair-specific modulation of intermuscular coupling, characterized by pair-specific modulation of EMG-EMG coherence between Power and Press (p < 0.05), and a negative linear association between co-contraction and intermuscular coupling for the ECR/FCR agonist-antagonist muscle pair (r = - 0.65; p < 0.05). This study brings new evidence that pair-specific modulation of EMG-EMG coherence is related to modulation of muscle force coordination during hand contractions. Our results highlight the functional importance of intermuscular coupling as a mechanism contributing to the control of muscle force synergies and agonist-antagonist co-contraction.

Rate of Torque Development and Feedforward Control of the Hip and Knee Extensors: Gender Differences.

PubMed

Stearns-Reider, Kristen M; Powers, Christopher M

2017-10-06

The purpose of this study was to determine whether women demonstrate decreased rate of torque development (RTD) of the hip and knee extensors and altered onset timing of the vastus lateralis and gluteus maximus during a drop-jump task when compared with men. On average, women demonstrated significantly lower normalized RTD of the hip extensors (women: 11.6 ± 1.3 MVT.s -1 , men: 13.1 ± 0.9 MVT.s -1 ; p ≤ .01); however, there was no significant difference in knee extensor RTD. Women also demonstrated significantly earlier activation of their vastus lateralis (women: 206.0 ± 130.6 ms, men: 80.9 ± 69.6 ms; p ≤ .01) and gluteus maximus (women: 85.7 ± 58.6 ms, men: 54.5 ± 35.4 ms; p = .02). In both men and women, there was a significant negative correlation between the hip extensor RTD and the vastus lateralis electromyographic onset time (men: r = -.386, p = .046; women: r = -.531, p = .008). The study findings suggest that women may utilize a feedforward control strategy in which they activate their knee extensors earlier than men to compensate for deficits in hip extensor RTD. The impaired capacity to rapidly stabilize the hip and knee joints during dynamic maneuvers may contribute to the increased risk of anterior cruciate ligament injury observed in women.

Blood flow restricted resistance training in older adults at risk of mobility limitations.

PubMed

Cook, Summer B; LaRoche, Dain P; Villa, Michelle R; Barile, Hannah; Manini, Todd M

2017-12-01

High-load resistance training (HL) may be contraindicated in older adults due to pre-existing health conditions (e.g. osteoarthritis). Low-load blood flow restricted (BFR) resistance training offers an alternative to HL with potentially similar strength improvement. To compare muscle strength, cross-sectional area (CSA), physical function, and quality of life (QOL) following 12-weeks of HL or BFR training in older adults at risk of mobility limitations. Thirty-six males and females (mean: 75.6years 95% confidence interval: [73.4-78.5], 1.67m [1.64-1.70], 74.3kg [69.8-78.8]) were randomly assigned to HL (70% of one repetition maximum [1-RM]) or low-load BFR (30% 1-RM coupled with a vascular restriction) exercise for the knee extensors and flexors twice per week for 12weeks. A control (CON) group performed light upper body resistance and flexibility training. Muscle strength, CSA of the quadriceps, 400-m walking speed, Short Physical Performance Battery (SPPB), and QOL were assessed before, midway and after training. Within 6-weeks of HL training, increases in all strength measures and CSA were evident and the gains were significantly greater than the CON group (P<0.05). The BFR group had strength increases in leg extension and leg press 1-RM tests, but were significantly lower in leg extension isometric maximum voluntary contraction (MVC) and leg extension 1-RM than the HL group (P<0.01). At 12-weeks HL and BFR training did not differ in MVC (P=0.14). Walking speed increased 4% among all training groups (P<0.01) and no changes were observed for overall SPPB score and QOL (P>0.05). Both training programs resulted in muscle CSA improvements and HL training had more pronounced strength gains than BFR training after 6-weeks and were more similar to BFR after 12-weeks of training. These changes in both groups did not transfer to improvements in QOL, SPPB, and walking speed. Since both programs result in strength and CSA gains, albeit at different rates, future research should consider using a combination of HL and BFR training in older adults with profound muscle weakness and mobility limitations. Copyright © 2017 Elsevier Inc. All rights reserved.

THE INFLUENCE OF HIP STRENGTH ON KNEE KINEMATICS DURING A SINGLE-LEGGED MEDIAL DROP LANDING AMONG COMPETITIVE COLLEGIATE BASKETBALL PLAYERS.

PubMed

Suzuki, Hidetomo; Omori, Go; Uematsu, Daisuke; Nishino, Katsutoshi; Endo, Naoto

2015-10-01

A smaller knee flexion angle and larger knee valgus angle during weight-bearing activities have been identified as risk factors for non-contact anterior cruciate ligament (ACL) injuries. To prevent such injuries, attention has been focused on the role of hip strength in knee motion control. However, gender differences in the relationship between hip strength and knee kinematics during weight-bearing activities in the frontal plane have not been evaluated. The purpose of this study was to determine the influence of hip strength on knee kinematics in both genders during a single-legged landing task in the frontal plane. The hypotheses were that 1) subjects with a greater hip strength would demonstrate larger knee flexion and smaller knee valgus and internal rotation angles and 2) no gender differences would exist during the single-legged landing task. Forty-three Japanese collegiate basketball players (20 males, 23 females) participated in this study. Three-dimensional motion analysis was used to evaluate knee kinematics during a single-legged medial drop landing (SML). A hand-held dynamometer was used to assess hip extensor (HEXT), abductor (HAB), and external rotator (in two positions: seated position [SHER] and prone [PHER]) isometric strength. Spearman rank correlation coefficients (ρ) were determined for correlations between hip strength and knee kinematics at initial contact (IC) and peak (PK) during SML (p < 0.05). Negative correlations were observed between the knee valgus angle at IC and HEXT (ρ = -0.48, p = 0.02), HAB (ρ = -0.46, p = 0.03) and PHER (ρ = -0.44, p = 0.04) strength in females. In addition, a significant positive correlation was observed between the knee flexion angle at PK and HEXT strength (ρ = 0.61, p = 0.004) in males. Significant correlations between hip strength and knee kinematics during SML were observed in both genders. Hip strength may, therefore, play an important role in knee motion control during sports activities, suggesting that increased hip strength may help to prevent non-contact ACL injuries in athletes of both genders. Moreover, gender-specific programs may be needed to control abnormal knee motion, as the influence of hip strength on knee kinematics may differ based on gender. 3.

Extensor Tendon Instability Due to Sagittal Band Injury in a Martial Arts Athlete: A Case Report.

PubMed

Kochevar, Andrew; Rayan, Ghazi

2017-03-01

A Taekwondo participant sustained a hand injury from punching an opponent that resulted in painful instability of the ring finger extensor digitorum communis tendon due to sagittal band damage. His symptoms resolved after reconstructive surgery on the sagittal band (SB) with stabilization of the extensor tendon over the metacarpophalangeal joint.

ACTN3 R577X polymorphism and explosive leg-muscle power in elite basketball players.

PubMed

Garatachea, Nuria; Verde, Zoraida; Santos-Lozano, Alejandro; Yvert, Thomas; Rodriguez-Romo, Gabriel; Sarasa, Francisco J; Hernández-Sánchez, Sonsoles; Santiago, Catalina; Lucia, Alejandro

2014-03-01

To determine the association of the ACTN3 R577X polymorphism with leg-muscle explosive power in Spanish (white) elite basketball players and controls. 100 (60 men) elite basketball players (cases) and 283 nonathletic controls. The authors assessed power performance by means of the vertical-squat and countermovement-jump tests. Genotype distributions did not differ between groups (cases: 37.0% [RR], 42.0% [RX], and 21.0% [XX]; controls: 31.8% [RR], 49.8% [RX], and 18.4% [XX]; P = .353). The authors did not observe any effect of the ACTN3 R577X polymorphism on study phenotypes in either group, including when they performed the analyses separately in men and women. They found no association between the ACTN3 R577X polymorphism and the likelihood of being an elite basketball player using the dominant or the recessive model, and the results remained unaltered when the analyses were adjusted for sex, weight, height, and age or when performed for men and women separately. Although the ACTN3 R577X is associated with explosive muscle performance and this phenotype is important in the sport of basketball (ie, during jumps), the authors found no association with leg explosive power in elite basket players or with the status of being this type of athlete.

Assessing the Relative Contributions of Active Ankle and Knee Assistance to the Walking Mechanics of Transfemoral Amputees Using a Powered Prosthesis

PubMed Central

Simon, Ann M.; Hargrove, Levi J.

2016-01-01

Powered knee-ankle prostheses are capable of providing net-positive mechanical energy to amputees. Yet, there are limitless ways to deliver this energy throughout the gait cycle. It remains largely unknown how different combinations of active knee and ankle assistance affect the walking mechanics of transfemoral amputees. This study assessed the relative contributions of stance phase knee swing initiation, increasing ankle stiffness and powered plantarflexion as three unilateral transfemoral amputees walked overground at their self-selected walking speed. Five combinations of knee and ankle conditions were evaluated regarding the kinematics and kinetics of the amputated and intact legs using repeated measures analyses of variance. We found eliminating active knee swing initiation or powered plantarflexion was linked to increased compensations of the ipsilateral hip joint during the subsequent swing phase. The elimination of knee swing initiation or powered plantarflexion also led to reduced braking ground reaction forces of the amputated and intact legs, and influenced both sagittal and frontal plane loading of the intact knee joint. Gradually increasing prosthetic ankle stiffness influenced the shape of the prosthetic ankle plantarflexion moment, more closely mirroring the intact ankle moment. Increasing ankle stiffness also corresponded to increased prosthetic ankle power generation (despite a similar maximum stiffness value across conditions) and increased braking ground reaction forces of the amputated leg. These findings further our understanding of how to deliver assistance with powered knee-ankle prostheses and the compensations that occur when specific aspects of assistance are added/removed. PMID:26807889

The Interaction of Trunk-Load and Trunk-Position Adaptations on Knee Anterior Shear and Hamstrings Muscle Forces During Landing

PubMed Central

Kulas, Anthony S.; Hortobágyi, Tibor; DeVita, Paul

2010-01-01

Abstract Context: Because anterior cruciate ligament (ACL) injuries can occur during deceleration maneuvers, biomechanics research has been focused on the lower extremity kinetic chain. Trunk mass and changes in trunk position affect lower extremity joint torques and work during gait and landing, but how the trunk affects knee joint and muscle forces is not well understood. Objective: To evaluate the effects of added trunk load and adaptations to trunk position on knee anterior shear and knee muscle forces in landing. Design: Crossover study. Setting: Controlled laboratory environment. Patients or Other Participants: Twenty-one participants (10 men: age  =  20.3 ± 1.15 years, height  =  1.82 ± 0.04 m, mass  =  78.2 ± 7.3 kg; 11 women: age  =  20.0 ± 1.10 years, height  =  1.72 ± 0.06 m, mass  =  62.3 ± 6.4 kg). Intervention(s): Participants performed 2 sets of 8 double-leg landings under 2 conditions: no load and trunk load (10% body mass). Participants were categorized into one of 2 groups based on the kinematic trunk adaptation to the load: trunk flexor or trunk extensor. Main Outcome Measure(s): We estimated peak and average knee anterior shear, quadriceps, hamstrings, and gastrocnemius forces with a biomechanical model. Results: We found condition-by-group interactions showing that adding a trunk load increased peak (17%) and average (35%) knee anterior shear forces in the trunk-extensor group but did not increase them in the trunk-flexor group (peak: F1,19  =  10.56, P  =  .004; average: F1,19  =  9.56, P  =  .006). We also found a main effect for condition for quadriceps and gastrocnemius forces. When trunk load was added, peak (6%; F1,19  =  5.52, P  =  .030) and average (8%; F1,19  =  8.83, P  =  .008) quadriceps forces increased and average (4%; F1,19  =  4.94, P  =  .039) gastrocnemius forces increased, regardless of group. We found a condition-by-group interaction for peak (F1,19  =  5.16, P  =  .035) and average (F1,19  =  12.35, P  =  .002) hamstrings forces. When trunk load was added, average hamstrings forces decreased by 16% in the trunk-extensor group but increased by 13% in the trunk-flexor group. Conclusions: Added trunk loads increased knee anterior shear and knee muscle forces, depending on trunk adaptation strategy. The trunk-extensor adaptation to the load resulted in a quadriceps-dominant strategy that increased knee anterior shear forces. Trunk-flexor adaptations may serve as a protective strategy against the added load. These findings should be interpreted with caution, as only the face validity of the biomechanical model was assessed. PMID:20064042

Transposition of branches of radial nerve innervating supinator to posterior interosseous nerve for functional reconstruction of finger and thumb extension in 4 patients with middle and lower trunk root avulsion injuries of brachial plexus.

PubMed

Wu, Xia; Cong, Xiao-Bing; Huang, Qi-Shun; Ai, Fang-Xin; Liu, Yu-Tian; Lu, Xiao-Cheng; Li, Jin; Weng, Yu-Xiong; Chen, Zhen-Bing

2017-12-01

This study aimed to investigate the reconstruction of the thumb and finger extension function in patients with middle and lower trunk root avulsion injuries of the brachial plexus. From April 2010 to January 2015, we enrolled in this study 4 patients diagnosed with middle and lower trunk root avulsion injuries of the brachial plexus via imaging tests, electrophysiological examinations, and clinical confirmation. Muscular branches of the radial nerve, which innervate the supinator in the forearm, were transposed to the posterior interosseous nerve to reconstruct the thumb and finger extension function. Electrophysiological findings and muscle strength of the extensor pollicis longus and extensor digitorum communis, as well as the distance between the thumb tip and index finger tip, were monitored. All patients were followed up for 24 to 30 months, with an average of 27.5 months. Motor unit potentials (MUP) of the extensor digitorum communis appeared at an average of 3.8 months, while MUP of the extensor pollicis longus appeared at an average of 7 months. Compound muscle action potential (CMAP) appeared at an average of 9 months in the extensor digitorum communis, and 12 months in the extensor pollicis longus. Furthermore, the muscle strength of the extensor pollicis longus and extensor digitorum communis both reached grade III at 21 months. Lastly, the average distance between the thumb tip and index finger tip was 8.8 cm at 21 months. In conclusion, for patients with middle and lower trunk injuries of the brachial plexus, transposition of the muscular branches of the radial nerve innervating the supinator to the posterior interosseous nerve for the reconstruction of thumb and finger extension function is practicable and feasible.

Roll type conducting polymer legs for rigid-flexible thermoelectric generator

NASA Astrophysics Data System (ADS)

Park, Teahoon; Lim, Hanwhuy; Hwang, Jong Un; Na, Jongbeom; Lee, Hyunki; Kim, Eunkyoung

2017-07-01

A roll-type conducting polymer film was explored as a flexible organic p-type thermoelectric leg using poly(3,4-ethylenedioxythiophene) (PEDOT) doped with tosylate. The PEDOT films were prepared through solution casting polymerization and rolled up for a roll-type leg. Due to the high flexibility, the roll-type PEDOT leg enabled easy contact to both top and bottom electrodes. Simulation on the dynamic heat transfer and convective cooling for a vertically roosted rod- and roll-type PEDOT leg showed that the temperature difference (ΔT) between the hot and cold sides of the leg was much higher in the roll than that of the rod. The PEDOT legs were integrated with n-type Bi2Te3 blocks, to give a 36-couple rigid-flexible thermoelectric generator (RF-TEG). The maximum output voltage from the 36-couple RF-TEG under a ΔT of 7.9 K was determined as 36.7 mV along with a high output power of 115 nW. A wearable RF-TEG was prepared upon the combination of the 36-couple RF-TEG with an arm warmer, to afford an output voltage of 10.6 mV, which was generated constantly and steadily from human wrist heat.

Clinical Sign for Missed Decompression of a Separate Extensor Pollicis Brevis Compartment in de Quervain's Disease.

PubMed

Benatar, Niels

2017-08-01

Persistent pain despite previous surgery for de Quervain's disease might be due to an overlooked septum between the abductor pollicis longus tendon slips and the extensor pollicis brevis tendon, or an overlooked completely separate compartment for the extensor pollicis brevis tendon alone. In both of these instances, extension of the MP joint of the thumb against resistance elicits pain at the distal level of the first extensor compartment of the wrist. When this sign is positive, revisional surgery and decompression of the remaining septum or separate compartment is indicated. © Georg Thieme Verlag KG Stuttgart · New York.

Rupture of the extensor hood of the fifth toe: a rare injury.

PubMed

Venturini, Sara; Gaba, Suchi; Mangwani, Jitendra

2017-02-27

Closed injuries of the extensor hood of the lesser toes are rare and seldom reported in the literature. We present the case of a woman aged 25 years who presented to the orthopaedic fracture clinic with a 2-week history of pain in the left fifth toe and inability to extend following a ballet dancing session. Investigations showed no fracture on plain radiographs, but an ultrasound scan demonstrated rupture to the extensor hood of the little toe. Successful surgical repair of the extensor hood was performed, and the patient made a good recovery with return to dancing activities. 2017 BMJ Publishing Group Ltd.

Measurement of fatigue in knee flexor and extensor muscles.

PubMed

Kawabata, Y; Senda, M; Oka, T; Yagata, Y; Takahara, Y; Nagashima, H; Inoue, H

2000-04-01

In order to examine fatigue of the knee flexor and extensor muscles and to investigate the characteristics of muscular fatigue in different sports, a Cybex machine was used to measure muscle fatigue and recovery during isokinetic knee flexion and extension. Eighteen baseball players, 12 soccer players and 13 marathon runners were studied. Each subject was tested in the sitting position and made to perform 50 consecutive right knee bends and stretches at maximum strength. This was done 3 times with an interval of 10 min between each series. The peak torque to body weight ratio and the fatigue rate were determined in each case. In all subjects, the peak torque to body weight ratio was higher for extensors than flexors. Over the 3 trials, the fatigue rate of extensors showed little change, while that of flexors had a tendency to increase. In each subject, knee extensors showed a high fatigue rate but a quick recovery, while knee flexors showed a low fatigue rate but a slow recovery. As the marathon runners had the smallest fatigue rates for both flexors and extensors, we concluded that marathon runners had more stamina than baseball players and soccer players.

The influence of lumbar extensor muscle fatigue on lumbar-pelvic coordination during weightlifting.

PubMed

Hu, Boyi; Ning, Xiaopeng

2015-01-01

Lumbar muscle fatigue is a potential risk factor for the development of low back pain. In this study, we investigated the influence of lumbar extensor muscle fatigue on lumbar-pelvic coordination patterns during weightlifting. Each of the 15 male subjects performed five repetitions of weightlifting tasks both before and after a lumbar extensor muscle fatiguing protocol. Lumbar muscle electromyography was collected to assess fatigue. Trunk kinematics was recorded to calculate lumbar-pelvic continuous relative phase (CRP) and CRP variability. Results showed that fatigue significantly reduced the average lumbar-pelvic CRP value (from 0.33 to 0.29 rad) during weightlifting. The average CRP variability reduced from 0.17 to 0.15 rad, yet this change ws statistically not significant. Further analyses also discovered elevated spinal loading during weightlifting after the development of lumbar extensor muscle fatigue. Our results suggest that frequently experienced lumbar extensor muscle fatigue should be avoided in an occupational environment. Lumbar extensor muscle fatigue generates more in-phase lumbar-pelvic coordination patterns and elevated spinal loading during lifting. Such increase in spinal loading may indicate higher risk of back injury. Our results suggest that frequently experienced lumbar muscle fatigue should be avoided to reduce the risk of LBP.

Multi-slice MRI reveals heterogeneity in disease distribution along the length of muscle in Duchenne muscular dystrophy.

PubMed

Chrzanowski, Stephen M; Baligand, Celine; Willcocks, Rebecca J; Deol, Jasjit; Schmalfuss, Ilona; Lott, Donovan J; Daniels, Michael J; Senesac, Claudia; Walter, Glenn A; Vandenborne, Krista

2017-09-01

Duchenne muscular dystrophy (DMD) causes progressive pathologic changes to muscle secondary to a cascade of inflammation, lipid deposition, and fibrosis. Clinically, this manifests as progressive weakness, functional loss, and premature mortality. Though insult to whole muscle groups is well established, less is known about the relationship between intramuscular pathology and function. Differences of intramuscular heterogeneity across muscle length were assessed using an ordinal MRI grading scale in lower leg muscles of boys with DMD and correlated to patient's functional status. Cross sectional T 1 weighted MRI images with fat suppression were obtained from ambulatory boys with DMD. Six muscles (tibialis anterior, extensor digitorum longus, peroneus, soleus, medial and lateral gastrocnemii) were graded using an ordinal grading scale over 5 slice sections along the lower leg length. The scores from each slice were combined and results were compared to global motor function and age. Statistically greater differences of involvement were observed at the proximal ends of muscle compared to the midbellies. Multi-slice assessment correlated significantly to age and the Vignos functional scale, whereas single-slice assessment correlated to the Vignos functional scale only. Lastly, differential disease involvement of whole muscle groups and intramuscular heterogeneity were observed amongst similar age subjects. A multi-slice ordinal MRI grading scale revealed that muscles are not uniformly affected, with more advanced disease visible near the tendons in a primarily ambulatory population with DMD. A geographically comprehensive evaluation of the heterogeneously affected muscle in boys with DMD may more accurately assess disease involvement.

An anatomic study of local infiltration analgesia in total knee arthroplasty.

PubMed

Quinn, M; Deakin, A H; McDonald, D A; Cunningham, I K T; Payne, A P; Picard, F

2013-10-01

Local infiltration analgesia (LIA) is a relatively novel technique developed for effective pain control following total knee arthroplasty (TKA), reducing requirements for epidural or parenteral postoperative analgesia. This study investigated the anatomical spread of an LIA used in TKA to identify the nerve structures reached by the injected fluid. Six fresh-frozen cadaveric lower limbs were injected according to a standardised LIA technique with a solution of latex and India ink to enable visualisation. Wounds were closed and limbs placed flat in a freezer at -20°C for two weeks. Limbs were then either sliced or dissected to identify solution locations. Solution was found from the proximal thigh to the middle of the lower leg. The main areas of concentration were the popliteal fossa, the anterior aspect of the femur and the subcutaneous tissue of the anterior aspect of the knee. There was less solution in the lower popliteal fossa. The solution was found to reach the majority of nerves, with good infiltration of nerves supplying the knee. These results support the positive clinical outcomes with this LIA technique. However, the lack of infiltration into the lower popliteal fossa suggests more fluid or a different injection point could be used. The solution reaching the extensor muscles of the lower leg is likely to have no beneficial analgesic effect for a TKA patient. The LIA technique is already used in clinical practice following total knee arthroplasty. Results from this study show there may be scope to optimise the injection sites in LIA technique. © 2013.

Changes in passive tension of muscle in humans and animals after eccentric exercise

PubMed Central

Whitehead, N P; Weerakkody, N S; Gregory, J E; Morgan, D L; Proske, U

2001-01-01

This is a report of experiments on ankle extensor muscles of human subjects and a parallel series on the medial gastrocnemius of the anaesthetised cat, investigating the origin of the rise in passive tension after a period of eccentric exercise. Subjects exercised their triceps surae of one leg eccentrically by walking backwards on an inclined, forward-moving treadmill. Concentric exercise required walking forwards on a backwards-moving treadmill. For all subjects the other leg acted as a control. Immediately after both eccentric and concentric exercise there was a significant drop in peak active torque, but only after eccentric exercise was this accompanied by a shift in optimum angle for torque generation and a rise in passive torque. In the eccentrically exercised group some swelling and soreness developed but not until 24 h post-exercise. In the animal experiments the contracting muscle was stretched by 6 mm at 50 mm s−1 over a length range symmetrical about the optimum length for tension generation. Measurements of passive tension were made before and after the eccentric contractions, using small stretches to a range of muscle lengths, or with large stretches covering the full physiological range. After 150 eccentric contractions, passive tension was significantly elevated over most of the range of lengths. Measurements of work absorption during stretch-release cycles showed significant increases after the contractions. It is suggested that the rise in passive tension in both human and animal muscles after eccentric contractions is the result of development of injury contractures in damaged muscle fibres. PMID:11389215

Dynamic Motor Compensations with Permanent, Focal Loss of Forelimb Force after Cervical Spinal Cord Injury

PubMed Central

López-Dolado, Elisa; Lucas-Osma, Ana M.

2013-01-01

Abstract Incomplete cervical lesion is the most common type of human spinal cord injury (SCI) and causes permanent paresis of arm muscles, a phenomenon still incompletely understood in physiopathological and neuroanatomical terms. We performed spinal cord hemisection in adult rats at the caudal part of the segment C6, just rostral to the bulk of triceps brachii motoneurons, and analyzed the forces and kinematics of locomotion up to 4 months postlesion to determine the nature of motor function loss and recovery. A dramatic (50%), immediate and permanent loss of extensor force occurred in the forelimb but not in the hind limb of the injured side, accompanied by elbow and wrist kinematic impairments and early adaptations of whole-body movements that initially compensated the balance but changed continuously over the follow-up period to allow effective locomotion. Overuse of both contralateral legs and ipsilateral hind leg was evidenced since 5 days postlesion. Ipsilateral foreleg deficits resulted mainly from interruption of axons that innervate the spinal cord segments caudal to the lesion, because chronic loss (about 35%) of synapses was detected at C7 while only 14% of triceps braquii motoneurons died, as assessed by synaptophysin immunohistochemistry and retrograde neural tracing, respectively. We also found a large pool of propriospinal neurons projecting from C2–C5 to C7 in normal rats, with topographical features similar to the propriospinal premotoneuronal system of cats and primates. Thus, concurrent axotomy at C6 of brain descending axons and cervical propriospinal axons likely hampered spontaneous recovery of the focal neurological impairments. PMID:23249275

Maintenance of exercise-induced benefits in physical functioning and bone among elderly women.

PubMed

Karinkanta, S; Heinonen, A; Sievänen, H; Uusi-Rasi, K; Fogelholm, M; Kannus, P

2009-04-01

This study showed that about a half of the exercise-induced gain in dynamic balance and bone strength was maintained one year after cessation of the supervised high-intensity training of home-dwelling elderly women. However, to maintain exercise-induced gains in lower limb muscle force and physical functioning, continued training seems necessary. Maintenance of exercise-induced benefits in physical functioning and bone structure was assessed one year after cessation of 12-month randomized controlled exercise intervention. Originally 149 healthy women 70-78 years of age participated in the 12-month exercise RCT and 120 (81%) of them completed the follow-up study. Self-rated physical functioning, dynamic balance, leg extensor force, and bone structure were assessed. During the intervention, exercise increased dynamic balance by 7% in the combination resistance and balance-jumping training group (COMB). At the follow-up, a 4% (95% CI: 1-8%) gain compared with the controls was still seen, while the exercise-induced isometric leg extension force and self-rated physical functioning benefits had disappeared. During the intervention, at least twice a week trained COMB subjects obtained a significant 2% benefit in tibial shaft bone strength index compared to the controls. A half of this benefit seemed to be maintained at the follow-up. Exercise-induced benefits in dynamic balance and rigidity in the tibial shaft may partly be maintained one year after cessation of a supervised 12-month multi-component training in initially healthy elderly women. However, to maintain the achieved gains in muscle force and physical functioning, continued training seems necessary.

Epidermal hydration and skin surface lipids in patients with long-term complications of sulfur mustard poisoning.

PubMed

Layegh, Pouran; Maleki, Masoud; Mousavi, Seyed Reza; Yousefzadeh, Hadis; Momenzadeh, Akram; Golmohammadzadeh, Shiva; Balali-Mood, Mahdi

2015-07-01

Despite almost the three decades passed since the chemical attacks of Iraqi's army against the Iranian troops, some veterans are still suffering from long-term complications of sulfur mustard (SM) poisoning, including certain skin complaints specially dryness, burning, and pruritus. We thus aimed to evaluate the skin's water and lipid content in patients with a disability of >25% due to complications of SM poisoning and compare them with a matched control group. Sixty-nine male participants were included in this study; 43 SM-exposed patients, and 26 normal controls from their close relatives. The water and lipid content was measured in four different locations: Extensor and flexor sides of forearms and lateral and medial sides of legs by the Corneometer CM 820/Sebumeter SM 810. Collected data was analyzed and P ≤ 0.05 was considered as statistically significant. The mean age of the patients and controls was 49.53 ± 11.34 (ranges: 40-71) and 29.08 ± 8.836 (ranges: 15-49 years), respectively. In the veterans group, the main cutaneous complaint was itching and skin dryness. Cherry angioma, dry skin, and pruritus were significantly more common in the SM-exposed cases than in the controls. (P = 0.01, 0.05, and 0.04, respectively). The moisture and lipid content of all areas were lower in the SM-exposed group, but it was only significant in skin sebum of lateral sides of legs (P = 0.02). Exposure to SM could decrease the function of stratum corneum and lipid production as a barrier, even after several years of its exposure.

Incorporating topography in a cellular automata model to simulate residents evacuation in a mountain area in China

NASA Astrophysics Data System (ADS)

Wang, Li; Liu, Mao; Meng, Bo

2013-02-01

In China, both the mountainous areas and the number of people who live in mountain areas occupy a significant proportion. When production accidents or natural disasters happen, the residents in mountain areas should be evacuated and the evacuation is of obvious importance to public safety. But it is a pity that there are few studies on safety evacuation in rough terrain. The particularity of the complex terrain in mountain areas, however, makes it difficult to study pedestrian evacuation. In this paper, a three-dimensional surface cellular automata model is proposed to numerically simulate the real time dynamic evacuation of residents. The model takes into account topographic characteristics (the slope gradient) of the environment and the biomechanics characteristics (weight and leg extensor power) of the residents to calculate the walking speed. This paper only focuses on the influence of topography and the physiological parameters are defined as constants according to a statistical report. Velocity varies with the topography. In order to simulate the behavior of a crowd with varying movement velocities, and a numerical algorithm is used to determine the time step of iteration. By doing so, a numerical simulation can be conducted in a 3D surface CA model. Moreover, considering residents evacuation around a gas well in a mountain area as a case, a visualization system for a three-dimensional simulation of pedestrian evacuation is developed. In the simulation process, population behaviors of congestion, queuing and collision avoidance can be observed. The simulation results are explained reasonably. Therefore, the model presented in this paper can realize a 3D dynamic simulation of pedestrian evacuation vividly in complex terrain and predict the evacuation procedure and evacuation time required, which can supply some valuable information for emergency management.

Reduced Electromyographic Fatigue Threshold after Performing a Cognitive Fatiguing Task.

PubMed

Ferris, Justine R; Tomlinson, Mary A; Ward, Tayler N; Pepin, Marie E; Malek, Moh H

2018-02-22

Cognitive fatigue tasks performed prior to exercise may reduce exercise capacity. The electromyographic fatigue threshold (EMGFT) is the highest exercise intensity that can be maintained without significant increase in the EMG amplitude versus time relationship. To date, no studies have examined the effect of cognitive fatigue on the estimation of the EMGFT. The purpose of this study, therefore, was to determine whether or not cognitive fatigue prior to performing exercise reduces the estimated EMGFT. Eight healthy college-aged men were recruited from a university student population and visited the laboratory on multiple occasions. In a randomized order, subjects performed either the cognitive fatigue task (AX Continuous Performance Test; AX-CPT) for 60 min on one visit (experimental condition) or watched a video on trains for 60 min on the other visit (control condition). After each condition, subjects performed the incremental single-leg knee-extensor ergometry test while the EMG amplitude was recorded from the rectus femoris muscle and heart rate was monitored throughout. Thereafter, the EMGFT was calculated for each participant for each visit and compared using paired samples t-test. For exercise outcomes, there were no significant mean differences for maximal power output between the two conditions (control: 51 ± 5 vs. fatigue: 50 ± 3 W), but a significant decrease in EMGFT between the two conditions (control: 31 ± 3 vs. fatigue: 24 ± 2 W; p = 0.013). Moreover, maximal heart rate was significantly different between the two conditions (control: 151 ± 5 vs. fatigue: 132 ± 6; p = 0.027). These results suggest that performing the cognitive fatiguing task reduces the EMGFT with a corresponding reduction in maximal heart rate response.

On the stiffness analysis of a cable driven leg exoskeleton.

PubMed

Sanjeevi, N S S; Vashista, Vineet

2017-07-01

Robotic systems are being used for gait rehabilitation of patients with neurological disorder. These devices are externally powered to apply external forces on human limbs to assist the leg motion. Patients while walking with these devices adapt their walking pattern in response to the applied forces. The efficacy of a rehabilitation paradigm thus depends on the human-robot interaction. A cable driven leg exoskeleton (CDLE) use actuated cables to apply external joint torques on human leg. Cables are lightweight and flexible but can only be pulled, thus a CDLE requires redundant cables. Redundancy in CDLE can be utilized to appropriately tune a robot's performance. In this work, we present the stiffness analysis of CDLE. Different stiffness performance indices are established to study the role of system parameters in improving the human-robot interaction.

Effects of Lumbar Strengthening Exercise in Lower-Limb Amputees With Chronic Low Back Pain.

PubMed

Shin, Min Kyung; Yang, Hee Seung; Yang, Hea-Eun; Kim, Dae Hyun; Ahn, Bo Ram; Kwon, Hyup; Lee, Ju Hwan; Jung, Suk; Choi, Hyun Chul; Yun, Sun Keaung; Ahn, Dong Young; Sim, Woo Sob

2018-02-01

To analyze the effect of lumbar strengthening exercise in lower-limb amputees with chronic low back pain. We included in this prospective study 19 lower-limb amputees who had experienced low back pain for longer than 6 months. Participants were treated with 30-minute lumbar strengthening exercises, twice weekly, for 8 weeks. We used the visual analog scale (VAS), and Oswestry low back pain disability questionnaire, and measured parameters such as iliopsoas length, abdominal muscle strength, back extensor strength, and back extensor endurance. In addition, we assessed the isometric peak torque and total work of the trunk flexors and extensors using isokinetic dynamometer. The pre- and post-exercise measurements were compared. Compared with the baseline, abdominal muscle strength (from 4.4±0.7 to 4.8±0.6), back extensor strength (from 2.6±0.6 to 3.5±1.2), and back extensor endurance (from 22.3±10.7 to 46.8±35.1) improved significantly after 8 weeks. The VAS decreased significantly from 4.6±2.2 to 2.6±1.6 after treatment. Furthermore, the peak torque and total work of the trunk flexors and extensors increased significantly (p<0.05). Lumbar strengthening exercise in lower-limb amputees with chronic low back pain resulted in decreased pain and increased lumbar extensor strength. The lumbar strengthening exercise program is very effective for lower-limb amputees with chronic low back pain.

Model development to study strategies of younger and older adults getting up from the floor.

PubMed

Schwickert, L; Oberle, C; Becker, C; Lindemann, U; Klenk, J; Schwenk, M; Bourke, A; Zijlstra, W

2016-04-01

Long lies after a fall remain a public health challenge. Many successful fall prevention programmes have been developed but only few of them include recovery strategies after a fall. Once better understood, such movement strategies could be implemented into training interventions. A model of motion sequences describing successful movement strategies for rising from the floor in different age groups was developed. Possible risk factors for poor rising performance such as flexibility and muscle power were evaluated. Fourteen younger subjects between 20 and 50 years of age and 10 healthy older subjects (60+ years) were included. Movement strategies and key components of different rising sequences were determined from video analyses. The temporal parameters of transfers and number of components within the motion sequences were calculated. Possible explanatory variables for differences in rising performance were assessed (leg extension power, flexibility of the knee- and hip joints). Seven different components were identified for the lie-to-stand-walk transfer, labelled as lying, initiation, positioning, supporting, elevation, or stabilisation component followed by standing and/or walking. Median time to rise was significantly longer in older subjects (older 5.7s vs. younger 3.7s; p < 0.001), and leg extension power (left p = 0.002, right p = 0.013) and knee flexibility (left p = 0.019, right p = 0.025) were significantly lower. The number of components for rising was correlated with hip flexibility (r = 0.514) and maximal power (r = 0.582). The time to rise was correlated with minimal goniometric knee angle of the less flexible leg (r = 0.527) and maximal leg extension power (r = 0.725). A motion sequence model containing seven different components identified by individual key-frames could be established. Age-related differences in rising strategies and performance were identified.

Youth Baseball Pitching Stride Length: Normal Values and Correlation With Field Testing

PubMed Central

Fry, Karl E.; Pipkin, Andrew; Wittman, Kelcie; Hetzel, Scott; Sherry, Marc

2016-01-01

Background: Pitching biomechanical analysis has been recommended as an important component of performance, injury prevention, and rehabilitation. Normal values for youth pitching stride length have not been established, leading to application of normative values found among professional pitchers to youth pitchers. Hypotheses: The average youth pitching stride length will be significantly less than that of college and professional pitchers. There will be a positive correlation between stride length, lower extremity power, balance, and pitching experience. Study Design: Prospective cohort study. Level of Evidence: Level 3. Methods: Ninety-two youth baseball pitchers (aged 9-14 years) met the inclusion/exclusion criteria and completed the study. Stride length was recorded using a Dartfish video system over 3 maximal effort pitches. Both intra- and interrater reliability was calculated for the assessment of stride length. Double-leg vertical jump, single-leg stance time, leg length, weight, age, and pitching experience were also recorded. Results: Mean (SD) stride length was 66.0% (7.1%) of height. Stride length was correlated (P < 0.01) with vertical jump (0.38), pitching experience (0.36), and single-leg balance (0.28), with excellent intra- and interrater reliability (0.985 or higher). No significant correlations between stride length and body weight, leg length, or age existed. Conclusions: There was a significant difference between youth pitching stride length and the current published norms for older and more elite throwers. There was a positive correlation between stride length and lower extremity power, pitching experience, and single-leg balance. Clinical Relevance: Two-dimensional analysis of stride length allows for the assessment of pitching biomechanics in a practical manner. These values can be used for return to pitching parameters after an injury and designing injury prevention and performance programs. PMID:27864504

Youth Baseball Pitching Stride Length: Normal Values and Correlation With Field Testing.

PubMed

Fry, Karl E; Pipkin, Andrew; Wittman, Kelcie; Hetzel, Scott; Sherry, Marc

Pitching biomechanical analysis has been recommended as an important component of performance, injury prevention, and rehabilitation. Normal values for youth pitching stride length have not been established, leading to application of normative values found among professional pitchers to youth pitchers. The average youth pitching stride length will be significantly less than that of college and professional pitchers. There will be a positive correlation between stride length, lower extremity power, balance, and pitching experience. Prospective cohort study. Level 3. Ninety-two youth baseball pitchers (aged 9-14 years) met the inclusion/exclusion criteria and completed the study. Stride length was recorded using a Dartfish video system over 3 maximal effort pitches. Both intra- and interrater reliability was calculated for the assessment of stride length. Double-leg vertical jump, single-leg stance time, leg length, weight, age, and pitching experience were also recorded. Mean (SD) stride length was 66.0% (7.1%) of height. Stride length was correlated ( P < 0.01) with vertical jump (0.38), pitching experience (0.36), and single-leg balance (0.28), with excellent intra- and interrater reliability (0.985 or higher). No significant correlations between stride length and body weight, leg length, or age existed. There was a significant difference between youth pitching stride length and the current published norms for older and more elite throwers. There was a positive correlation between stride length and lower extremity power, pitching experience, and single-leg balance. Two-dimensional analysis of stride length allows for the assessment of pitching biomechanics in a practical manner. These values can be used for return to pitching parameters after an injury and designing injury prevention and performance programs.

Physical Characteristics Underpinning Lunging and Change of Direction Speed in Fencing.

PubMed

Turner, Anthony; Bishop, Chris; Chavda, Shyam; Edwards, Mike; Brazier, Jon; Kilduff, Liam P

2016-08-01

Turner, A, Bishop, C, Chavda, S, Edwards, M, Brazier, J, Kilduff, LP. Physical characteristics underpinning lunging and change of direction speed in fencing. J Strength Cond Res 30(8): 2235-2241, 2016-Lunge velocity (LV) and change of direction speed (CODS) are considered fundamental to success during fencing competitions; investigating the physical characteristics that underpin these is the aim of this study. Seventy fencers from the British Fencing National Academy took part and on average (±SD) were 16.83 ± 1.72 years of age, 178.13 ± 8.91 cm tall, 68.20 ± 9.64 kg in mass, and had 6.25 ± 2.23 years fencing experience. The relationship between anthropometric characteristics (height, arm span, and adductor flexibility) and measures of lower-body power (bilateral and unilateral countermovement jump height and reactive strength index) were examined in their ability to influence LV and CODS. In testing the former, fencers lunged (over a self-selected distance) to and from a force plate, where front leg impact and rear leg propulsive force were quantified; the lunging distance was divided by time to establish LV. Change of direction speed was measured over 12 m involving shuttles of between 2 and 4 m. Results revealed that LV and CODS averaged at 3.35 m·s and 5.45 seconds, respectively, and in both cases, standing broad jump was the strongest predictor (r = 0.51 and -0.65, respectively) of performance. Rear leg drive and front leg impact force averaged at 14.61 N·kg and 3 times body weight, respectively, with single leg jumps revealing an asymmetry favoring the front leg of 9 ± 8%. In conclusion, fencers should train lower-body power emphasizing horizontal displacement, noting that this seems to offset any advantage one would expect fencers of a taller stature to have. Also, the commonly reported asymmetry between legs is apparent from adolescence and thus also requires some attention.

Design and development of broadband piezoelectric vibration energy harvester based on compliant orthoplanar spring

NASA Astrophysics Data System (ADS)

Dhote, Sharvari

With advancement in technology, power requirements are reduced drastically for sensor nodes. The piezoelectric vibration energy harvesters generate sufficient power to low-powered sensor nodes. The main requirement of energy harvester is to provide a broad bandwidth. A conventional linear harvester does not satisfy this requirement. Therefore, the research focus is shifted to exploiting nonlinearity to widen the bandwidth of the harvester. Although nonlinear techniques are promising for broadening a bandwidth, reverse sweep shows reduced response as compared to the forward sweep. To overcome this issue, this thesis presents the design and development of a broadband piezoelectric vibration energy harvester based on a nonlinear multi-frequency compliant orthoplanar spring. This thesis is divided into three parts. The first part presents the design and experimental study of a tri-leg compliant orthoplanar spring for a broadband energy harvesting. The harvester performance is enhanced through the use of lightweight masses, which bring nonlinear vibration modes closer. The performance of the harvester is analyzed through development of a mathematical model based on the Duffing oscillator. The experimental and numerical results are in good agreement. The parametric study shows that an optimum performance is achieved by further reducing a gap in between the vibration modes using different weight masses. In the second part of the research, multiple (bi, quad and pent) leg compliant orthoplanar springs are designed to understand their role in expanding the bandwidth and reducing gap between vibration modes. The designed harvesters are compared by calculating the figure of merits. The quad-leg design provides a better performance in terms of power density and bandwidth among all the designs. The reverse sweep response is comparable to the forward sweep in terms of bandwidth. In the final part, a magnetic force is applied to the tri-leg harvester, which enhanced the voltage output and bandwidth. In addition, vibration modes have been brought even closer by reducing the gap between the modes. Overall, the proposed harvester performance is significantly improved using multiple legs attached with piezoelectric plates and masses, bringing the modes closer in the forward and reverse sweeps, making it advantageous to harvest energy from wideband environmental vibrations.

Functional anatomy of the gibbon forelimb: adaptations to a brachiating lifestyle

PubMed Central

Michilsens, Fana; Vereecke, Evie E; D'Août, Kristiaan; Aerts, Peter

2009-01-01

It has been shown that gibbons are able to brachiate with very low mechanical costs. The conversion of muscle activity into smooth, purposeful movement of the limb depends on the morphometry of muscles and their mechanical action on the skeleton. Despite the gibbon's reputation for excellence in brachiation, little information is available regarding either its gross musculoskeletal anatomy or its more detailed muscle–tendon architecture. We provide quantitative anatomical data on the muscle–tendon architecture (muscle mass, physiological cross-sectional area, fascicle length and tendon length) of the forelimb of four gibbon species, collected by detailed dissections of unfixed cadavers. Data are compared between different gibbon species and with similar published data of non-brachiating primates such as macaques, chimpanzees and humans. No quantitative differences are found between the studied gibbon species. Both their forelimb anatomy and muscle dimensions are comparable when normalized to the same body mass. Gibbons have shoulder flexors, extensors, rotator muscles and elbow flexors with a high power or work-generating capacity and their wrist flexors have a high force-generating capacity. Compared with other primates, the elbow flexors of gibbons are particularly powerful, suggesting that these muscles are particularly important for a brachiating lifestyle. Based on this anatomical study, the shoulder flexors, extensors, rotator muscles, elbow flexors and wrist flexors are expected to contribute the most to brachiation. PMID:19519640

Leg strength or velocity of movement: which is more influential on the balance of mobility limited elders?

PubMed

Mayson, Douglas J; Kiely, Dan K; LaRose, Sharon I; Bean, Jonathan F

2008-12-01

To determine which component of leg power (maximal limb strength or limb velocity) is more influential on balance performance in mobility limited elders. In this cross-sectional analysis we evaluated 138 community-dwelling older adults with mobility limitation. Balance was measured using the Unipedal Stance Test, the Berg Balance Test (BERG), the Dynamic Gait Index, and the performance-oriented mobility assessment. We measured one repetition maximum strength and power at 40% one repetition maximum strength, from which velocity was calculated. The associations between maximal estimated leg strength and velocity with balance performance were examined using separate multivariate logistic regression models. Strength was found to be associated [odds ratio of 1.06 (95% confidence interval, 1.01-1.11)] with performance on the Unipedal Stance Test, whereas velocity showed no statistically significant association. In contrast, velocity was consistently associated with performance on all composite measures of balance (BERG 14.23 [1.84-109.72], performance-oriented mobility assessment 33.92 [3.69-312.03], and Dynamic Gait Index 35.80 [4.77-268.71]). Strength was only associated with the BERG 1.08 (1.01-1.14). Higher leg press velocity is associated with better performance on the BERG, performance-oriented mobility assessment, and Dynamic Gait Index, whereas greater leg strength is associated with better performance on the Unipedal Stance Test and the BERG. These findings are likely related to the intrinsic qualities of each test and emphasize the relevance of limb velocity.

Autonomous exoskeleton reduces metabolic cost of human walking during load carriage.

PubMed

Mooney, Luke M; Rouse, Elliott J; Herr, Hugh M

2014-05-09

Many soldiers are expected to carry heavy loads over extended distances, often resulting in physical and mental fatigue. In this study, the design and testing of an autonomous leg exoskeleton is presented. The aim of the device is to reduce the energetic cost of loaded walking. In addition, we present the Augmentation Factor, a general framework of exoskeletal performance that unifies our results with the varying abilities of previously developed exoskeletons. We developed an autonomous battery powered exoskeleton that is capable of providing substantial levels of positive mechanical power to the ankle during the push-off region of stance phase. We measured the metabolic energy consumption of seven subjects walking on a level treadmill at 1.5 m/s, while wearing a 23 kg vest. During the push-off portion of the stance phase, the exoskeleton applied positive mechanical power with an average across the gait cycle equal to 23 ± 2 W (11.5 W per ankle). Use of the autonomous leg exoskeleton significantly reduced the metabolic cost of walking by 36 ± 12 W, which was an improvement of 8 ± 3% (p = 0.025) relative to the control condition of not wearing the exoskeleton. In the design of leg exoskeletons, the results of this study highlight the importance of minimizing exoskeletal power dissipation and added limb mass, while providing substantial positive power during the walking gait cycle.

Engineering platform and experimental protocol for design and evaluation of a neurally-controlled powered transfemoral prosthesis.

PubMed

Zhang, Fan; Liu, Ming; Harper, Stephen; Lee, Michael; Huang, He

2014-07-22

To enable intuitive operation of powered artificial legs, an interface between user and prosthesis that can recognize the user's movement intent is desired. A novel neural-machine interface (NMI) based on neuromuscular-mechanical fusion developed in our previous study has demonstrated a great potential to accurately identify the intended movement of transfemoral amputees. However, this interface has not yet been integrated with a powered prosthetic leg for true neural control. This study aimed to report (1) a flexible platform to implement and optimize neural control of powered lower limb prosthesis and (2) an experimental setup and protocol to evaluate neural prosthesis control on patients with lower limb amputations. First a platform based on a PC and a visual programming environment were developed to implement the prosthesis control algorithms, including NMI training algorithm, NMI online testing algorithm, and intrinsic control algorithm. To demonstrate the function of this platform, in this study the NMI based on neuromuscular-mechanical fusion was hierarchically integrated with intrinsic control of a prototypical transfemoral prosthesis. One patient with a unilateral transfemoral amputation was recruited to evaluate our implemented neural controller when performing activities, such as standing, level-ground walking, ramp ascent, and ramp descent continuously in the laboratory. A novel experimental setup and protocol were developed in order to test the new prosthesis control safely and efficiently. The presented proof-of-concept platform and experimental setup and protocol could aid the future development and application of neurally-controlled powered artificial legs.

Autonomous exoskeleton reduces metabolic cost of human walking during load carriage

PubMed Central

2014-01-01

Background Many soldiers are expected to carry heavy loads over extended distances, often resulting in physical and mental fatigue. In this study, the design and testing of an autonomous leg exoskeleton is presented. The aim of the device is to reduce the energetic cost of loaded walking. In addition, we present the Augmentation Factor, a general framework of exoskeletal performance that unifies our results with the varying abilities of previously developed exoskeletons. Methods We developed an autonomous battery powered exoskeleton that is capable of providing substantial levels of positive mechanical power to the ankle during the push-off region of stance phase. We measured the metabolic energy consumption of seven subjects walking on a level treadmill at 1.5 m/s, while wearing a 23 kg vest. Results During the push-off portion of the stance phase, the exoskeleton applied positive mechanical power with an average across the gait cycle equal to 23 ± 2 W (11.5 W per ankle). Use of the autonomous leg exoskeleton significantly reduced the metabolic cost of walking by 36 ± 12 W, which was an improvement of 8 ± 3% (p = 0.025) relative to the control condition of not wearing the exoskeleton. Conclusions In the design of leg exoskeletons, the results of this study highlight the importance of minimizing exoskeletal power dissipation and added limb mass, while providing substantial positive power during the walking gait cycle. PMID:24885527

Performance Test Results of a Skutterudite-Based Unicouple with a Metallic Coating

NASA Astrophysics Data System (ADS)

Saber, Hamed H.; El-Genk, Mohamed S.; Caillat, Thierry

2005-02-01

A performance test of a Skutterudite-based unicouple (MAY-04) with a metallic coating to suppress the sublimation of antimony from the legs near the hot junction is performed in vacuum (˜ 9 ×10-7 torr) for ˜ 2,000 hours at hot and cold junction temperatures of 892.1 ± 11.9 K and 316.1 ± 5.5 K, respectively. The p-leg is made of CeFe3.5Co0.5Sb12 and the n-leg is made of CoSb3. Presented are the measured voltage-current characteristics, electrical power, open-circuit voltage, and the Seebeck coefficients of the legs as functions of cumulative test time. Also presented is the estimate of the conversion efficiency, ˜ 96 hrs after the start of test. To demonstrate the effectiveness of the metallic coating, the measurements for MAY-04 are compared with those of two uncoated unicouples of the same leg materials (MAR-03 and JUN-03), which had been tested earlier. The cross-sectional areas of the legs in MAY-04 are larger than those in MAR-03 and JUN-03, tested in argon cover gas at ˜ 0.051-0.068 MPa for 450 and 1200 hours, respectively. The open circuit voltage, Voc (204 mV) of MAY-04 at Beginning-Of-Test (BOT) is almost the same as that of MAR-03, but higher than that of JUN-03 (˜180 mV). Although the argon gas effectively decreased antimony loss from legs of MAR-03 and JUN-03, marked degradations in performance occurred with time in these tests. Conversely, the metallic coating in MAY-04 effectively reduced the performance degradation with cumulative test time. The estimated peak efficiency of MAY-04, shortly after BOT (10.65%) is only ˜ 0.37 percentage point lower than the theoretical value, assuming zero side heat losses and zero contact resistance per leg. The peak power of MAY-04 decreased by only ˜12%, from its BOT value of ˜1.6 We to ˜1.4 We after ˜2,000 of cumulative testing.

Design of hair-like appendages and comparative analysis on their coordination toward steady and efficient swimming.

PubMed

Kwak, Bokeon; Bae, Joonbum

2017-05-22

The locomotion of water beetles has been widely studied in biology owing to their remarkable swimming skills. Inspired by the oar-like legs of water beetles, designing a robot that swims under the principle of drag-powered propulsion can lead to highly agile mobility. But its motion can easily be discontinuous and jerky due to backward motions (i.e. retraction) of the legs. Here we proposed novel hair-like appendages and consider their coordination to achieve steady and efficient swimming on the water surface. First of all, we propose several design schemes and fabrication methods of the hair-like appendages, which can passively adjust their projected area while obtaining enough thrust. The coordination between the two pairs of legs, as with water beetles in nature, were also investigated to achieve steady swimming without backward movement by varying the beating frequency and phase of the legs. To verify the functionality of the hair-like appendages and their coordinations, six different types of appendages were fabricated, and two robots (one with a single pair of legs and the other with two pairs of legs) were built. Locomotion of the robots was extensively compared through experiments, and it was found that steady swimming was achieved by properly coordinating the two pairs of legs without sacrificing their speed. Also, owing to the lower velocity fluctuation during swimming, it was shown that using two pairs of legs was more energy efficient than the robot with single pair of legs.

Comparison of Anthropometry and Lower Limb Power Qualities According to Different Levels and Ranking Position of Competitive Surfers.

PubMed

Fernandez-Gamboa, Iosu; Yanci, Javier; Granados, Cristina; Camara, Jesus

2017-08-01

Fernandez-Gamboa, I, Yanci, J, Granados, C, and Camara, J. Comparison of anthropometry and lower limb power qualities according to different levels and ranking position of competitive surfers. J Strength Cond Res 31(8): 2231-2237, 2017-The aim of this study was to compare competitive surfers' lower limb power output depending on their competitive level, and to evaluate the association between competition rankings. Twenty competitive surfers were divided according to the competitive level as follows: international (INT) or national (NAT), and competitive ranking (RANK1-50 or RANK51-100). Vertical jump and maximal peak power of the lower limbs were measured. No differences were found between INT and NAT surfers in the anthropometric variables, in the vertical jump, or in lower extremity power; although the NAT group had higher levels on the elasticity index, squat jumps (SJs), and counter movement jumps (CMJs) compared with the INT group. The RANK1-50 group had a lower biceps skinfold (p < 0.01), lower skinfolds in the legs (Front thigh: p ≤ 0.05; medial calf: p < 0.01), lower sum of skinfolds (p ≤ 0.05), higher SJ (p < 0.01), CMJ (p < 0.01), and 15 seconds vertical CMJ (p ≤ 0.05); also, maximal peak power of the right leg (MPPR) and left leg (MPPL) were higher in the RANK1-50 group. Moderate to large significant correlations were obtained between the surfers' ranking position and some skinfolds, the sum of skinfolds, and vertical jump. Results demonstrate that surfers' physical performance seems to be an accurate indicator of ranking positioning, also revealing that vertical jump capacity and anthropometric variables play an important role in their competitive performance, which may be important when considering their power training.

The first metatarsal web space: its applied anatomy and usage in tracing the first dorsal metatarsal artery in thumb reconstruction.

PubMed

Xu, Yong-Qing; Li, Jun; Zhong, Shi-Zhen; Xu, Da-Chuan; Xu, Xiao-Shan; Guo, Yuan-Fa; Wang, Xin-Min; Li, Zhu-Yi; Zhu, Yue-Liang

2004-12-01

To clarify the anatomical relationship of the structures in the first toe webbing space for better dissection of toes in thumb reconstruction. The first dorsal metatarsal artery, the first deep transverse metatarsal ligament and the extensor expansion were observed on 42 adult cadaveric lower extremities. Clinically the method of tracing the first dorsal metatarsal artery around the space of the extensor expansion was used in 36 cases of thumb reconstruction. The distal segments of the first dorsal metatarsal artery of Gilbert types I and II were located superficially to the extensor expansion. The harvesting time of a toe was shortened from 90 minutes to 50 minutes with 100% survival of reconstructed fingers. The distal segment of the first dorsal metatarsal artery lies constantly at the superficial layer of the extensor expansion. Most of the first metatarsal arteries of Gilbert types I and II can be easily located via the combined sequential and reverse dissection around the space of the extensor expansion.

Intelligent Gate Drive for Fast Switching and Crosstalk Suppression of SiC Devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Zheyu; Dix, Jeffery; Wang, Fei Fred

This study presents an intelligent gate drive for silicon carbide (SiC) devices to fully utilize their potential of high switching-speed capability in a phase-leg configuration. Based on the SiC device's intrinsic properties, a gate assist circuit consisting of two auxiliary transistors with two diodes is introduced to actively control gate voltages and gate loop impedances of both devices in a phase-leg configuration during different switching transients. Compared to conventional gate drives, the proposed circuit has the capability of accelerating the switching speed of the phase-leg power devices and suppressing the crosstalk to below device limits. Based on Wolfspeed 1200-V SiCmore » MOSFETs, the test results demonstrate the effectiveness of this intelligent gate drive under varying operating conditions. More importantly, the proposed intelligent gate assist circuitry is embedded into a gate drive integrated circuit, offering a simple, compact, and reliable solution for end-users to maximize benefits of SiC devices in actual power electronics applications.« less

Intelligent Gate Drive for Fast Switching and Crosstalk Suppression of SiC Devices

DOE PAGES

Zhang, Zheyu; Dix, Jeffery; Wang, Fei Fred; ...

2017-01-19

This study presents an intelligent gate drive for silicon carbide (SiC) devices to fully utilize their potential of high switching-speed capability in a phase-leg configuration. Based on the SiC device's intrinsic properties, a gate assist circuit consisting of two auxiliary transistors with two diodes is introduced to actively control gate voltages and gate loop impedances of both devices in a phase-leg configuration during different switching transients. Compared to conventional gate drives, the proposed circuit has the capability of accelerating the switching speed of the phase-leg power devices and suppressing the crosstalk to below device limits. Based on Wolfspeed 1200-V SiCmore » MOSFETs, the test results demonstrate the effectiveness of this intelligent gate drive under varying operating conditions. More importantly, the proposed intelligent gate assist circuitry is embedded into a gate drive integrated circuit, offering a simple, compact, and reliable solution for end-users to maximize benefits of SiC devices in actual power electronics applications.« less

Modelling and Control of Robotic Leg as Assistive Device

NASA Astrophysics Data System (ADS)

Jingye, Yee; Zain, Badrul Aisham bin Md

2017-10-01

The ageing population (people older than 60 years old) is expected to constitute 21.8% of global population by year 2050. When human ages, bodily function including locomotors will deteriorate. Besides, there are hundreds of thousands of victims who suffer from multiple health conditions worldwide that leads to gait impairment. A promising solution will be the lower limb powered-exoskeleton. This study is to be a start-up platform to design a lower limb powered-exoskeleton for a normal Malaysian male, by designing and simulating the dynamic model of a 2-link robotic leg to observe its behaviour under different input conditions with and without a PID controller. Simulink in MATLAB software is used as the dynamic modelling and simulation software for this study. It is observed that the 2-links robotic leg behaved differently under different input conditions, and perform the best when it is constrained and controlled by PID controller. Simulink model is formed as a foundation for the upcoming researches and can be modified and utilised by the future researchers.

Anatomic factors related to the cause of tennis elbow.

PubMed

Bunata, Robert E; Brown, David S; Capelo, Roderick

2007-09-01

The pathogenesis of lateral epicondylitis remains unclear. Our purpose was to study the anatomy of the lateral aspect of the elbow under static and dynamic conditions in order to identify bone-to-tendon and tendon-to-tendon contact or rubbing that might cause abrasion of the tissues. Eighty-five cadaveric elbows were examined to determine details related to the bone structure and musculotendinous origins. We identified the relative positions of the musculotendinous units and the underlying bone when the elbow was in different degrees of flexion. We also recorded the contact between the extensor carpi radialis brevis and the lateral edge of the capitellum as elbow motion occurred, and we sought to identify the areas of the capitellum and extensor carpi radialis brevis where contact occurs. The average site of origin of the extensor carpi radialis brevis on the humerus lay slightly medial and superior to the outer edge of the capitellum. As the elbow was extended, the undersurface of the extensor carpi radialis brevis rubbed against the lateral edge of the capitellum while the extensor carpi radialis longus compressed the brevis against the underlying bone. The extensor carpi radialis brevis tendon has a unique anatomic location that makes its undersurface vulnerable to contact and abrasion against the lateral edge of the capitellum during elbow motion.

Early reduction in toe flexor strength is associated with physical activity in elderly men.

PubMed

Suwa, Masataka; Imoto, Takayuki; Kida, Akira; Yokochi, Takashi

2016-05-01

[Purpose] To compare the toe flexor, hand grip and knee extensor strengths of young and elderly men, and to examine the association between toe flexor strength and physical activity or inactivity levels. [Subjects and Methods] Young (n=155, 18-23 years) and elderly (n=60, 65-88 years) men participated in this study. Toe flexor, hand grip, and knee extensor strength were measured. Physical activity (time spent standing/walking per day) and inactivity (time spent sitting per day) were assessed using a self-administered questionnaire. [Results] Toe flexor, hand grip, and knee extensor strength of the elderly men were significantly lower than those of the young men. Standing/walking and sitting times of the elderly men were lower than those of the young men. Toe flexor strength correlated with hand grip and knee extensor strength in both groups. In elderly men, toe flexor strength correlated with standing/walking time. In comparison to the young men's mean values, toe flexor strength was significantly lower than knee extensor and hand grip strength in the elderly group. [Conclusion] The results suggest that age-related reduction in toe flexor strength is greater than those of hand grip and knee extensor strengths. An early loss of toe flexor strength is likely associated with reduced physical activity in elderly men.

Is the Sørensen test valid to assess muscle fatigue of the trunk extensor muscles?

PubMed

Demoulin, Christophe; Boyer, Mathieu; Duchateau, Jacques; Grosdent, Stéphanie; Jidovtseff, Boris; Crielaard, Jean-Michel; Vanderthommen, Marc

2016-01-01

Very few studies have quantified the degree of fatigue characterized by the decline in the maximal voluntary contraction (MVC) force of the trunk extensors induced by the widely used Sørensen test. Measure the degree of fatigue of the trunk extensor muscles induced by the Sørensen test. Eighty young healthy subjects were randomly divided into a control group (CG) and an experimental group (EG), each including 50% of the two genders. The EG performed an isometric MVC of the trunk extensors (pre-fatigue test) followed by the Sørensen test, the latter being immediately followed by another MVC (post-fatigue test). The CG performed only the pre- and post-fatigue tests without any exertion in between. The comparison of the pre- and post-fatigue tests revealed a significant (P< 0.05) decrease in MVC force normalized by body mass (-13%) in the EG, whereas a small increase occurred in the CG (+2.7%, P= 0.001). This study shows that the Sørensen test performed until failure in a young healthy population results in a reduced ability of the trunk extensor muscles to generate maximal force, and indicates that this test is valid for the assessment of fatigue in trunk extensor muscles.

A six-legged rover for planetary exploration

NASA Technical Reports Server (NTRS)

Simmons, Reid; Krotkov, Eric; Bares, John

1991-01-01

To survive the rigors and isolation of planetary exploration, an autonomous rover must be competent, reliable, and efficient. This paper presents the Ambler, a six-legged robot featuring orthogonal legs and a novel circulating gait, which has been designed for traversal of rugged, unknown environments. An autonomous software system that integrates perception, planning, and real-time control has been developed to walk the Ambler through obstacle strewn terrain. The paper describes the information and control flow of the walking system, and how the design of the mechanism and software combine to achieve competent walking, reliable behavior in the face of unexpected failures, and efficient utilization of time and power.

Associations of knee extensor strength and standing balance with physical function in knee osteoarthritis.

PubMed

Pua, Yong-Hao; Liang, Zhiqi; Ong, Peck-Hoon; Bryant, Adam L; Lo, Ngai-Nung; Clark, Ross A

2011-12-01

Knee extensor strength is an important correlate of physical function in patients with knee osteoarthritis; however, it remains unclear whether standing balance is also a correlate. The purpose of this study was to evaluate the cross-sectional associations of knee extensor strength, standing balance, and their interaction with physical function. One hundred four older adults with end-stage knee osteoarthritis awaiting a total knee replacement (mean ± SD age 67 ± 8 years) participated. Isometric knee extensor strength was measured using an isokinetic dynamometer. Standing balance performance was measured by the center of pressure displacement during quiet standing on a balance board. Physical function was measured by the self-report Short Form 36 (SF-36) questionnaire and by the 10-meter fast-pace gait speed test. After adjustment for demographic and knee pain variables, we detected significant knee strength by standing balance interaction terms for both SF-36 physical function and fast-pace gait speed. Interrogation of the interaction revealed that standing balance in the anteroposterior plane was positively related to physical function among patients with lower knee extensor strength. Conversely, among patients with higher knee extensor strength, the standing balance-physical function associations were, or tended to be, negative. These findings suggest that although standing balance was related to physical function in patients with knee osteoarthritis, this relationship was complex and dependent on knee extensor strength level. These results are of importance in developing intervention strategies and refining theoretical models, but they call for further study. Copyright © 2011 by the American College of Rheumatology.