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Sample records for muscle strength fatiguability

  1. Soccer-specific fatigue and eccentric hamstrings muscle strength.

    PubMed

    Greig, Matt; Siegler, Jason C

    2009-01-01

    Epidemiologic findings of higher incidences of hamstrings muscle strains during the latter stages of soccer match play have been attributed to fatigue. To investigate the influence of soccer-specific fatigue on the peak eccentric torque of the knee flexor muscles. Descriptive laboratory study. Controlled laboratory environment. Ten male professional soccer players (age = 24.7 +/- 4.4 years, mass = 77.1 +/- 8.3 kg, Vo(2max) = 63.0 +/- 4.8 mL x kg(-1) x min(-1)). Participants completed an intermittent treadmill protocol replicating the activity profile of soccer match play, with a passive halftime interval. Before exercise and at 15-minute intervals, each player completed isokinetic dynamometer trials. Peak eccentric knee flexor torque was quantified at isokinetic speeds of 180 degrees x s(-1), 300 degrees x s(-1), and 60 degrees x s(-1), with 5 repetitions at each speed. Peak eccentric knee flexor torque at the end of the game (T(300eccH105) = 127 +/- 25 Nm) and at the end of the passive halftime interval (T(300eccH60) = 133 +/- 32 Nm) was reduced relative to T(300eccH00) (167 +/- 35 Nm, P < .01) and T(300eccH15) (161 +/- 35 Nm, P = .02). Eccentric hamstrings strength decreased as a function of time and after the halftime interval. This finding indicates a greater risk of injuries at these specific times, especially for explosive movements, in accordance with epidemiologic observations. Incorporating eccentric knee flexor exercises into resistance training sessions that follow soccer-specific conditioning is warranted to try to reduce the incidence or recurrence of hamstrings strains.

  2. Soccer-Specific Fatigue and Eccentric Hamstrings Muscle Strength

    PubMed Central

    Greig, Matt; Siegler, Jason C

    2009-01-01

    Context: Epidemiologic findings of higher incidences of hamstrings muscle strains during the latter stages of soccer match play have been attributed to fatigue. Objective: To investigate the influence of soccer-specific fatigue on the peak eccentric torque of the knee flexor muscles. Design: Descriptive laboratory study. Setting: Controlled laboratory environment. Patients or Other Participants: Ten male professional soccer players (age  =  24.7 ± 4.4 years, mass  =  77.1 ± 8.3 kg, V̇o2max  =  63.0 ± 4.8 mL·kg−1·min−1). Intervention(s): Participants completed an intermittent treadmill protocol replicating the activity profile of soccer match play, with a passive halftime interval. Before exercise and at 15-minute intervals, each player completed isokinetic dynamometer trials. Main Outcome Measure(s): Peak eccentric knee flexor torque was quantified at isokinetic speeds of 180° · s−1, 300° · s−1, and 60° · s−1, with 5 repetitions at each speed. Results: Peak eccentric knee flexor torque at the end of the game (T300eccH105  =  127 ± 25 Nm) and at the end of the passive halftime interval (T300eccH60  =  133 ± 32 Nm) was reduced relative to T300eccH00 (167 ± 35 Nm, P < .01) and T300eccH15 (161 ± 35 Nm, P  =  .02). Conclusions: Eccentric hamstrings strength decreased as a function of time and after the halftime interval. This finding indicates a greater risk of injuries at these specific times, especially for explosive movements, in accordance with epidemiologic observations. Incorporating eccentric knee flexor exercises into resistance training sessions that follow soccer-specific conditioning is warranted to try to reduce the incidence or recurrence of hamstrings strains. PMID:19295963

  3. Indoor mobility-related fatigue and muscle strength in nonagenarians: a prospective longitudinal study

    PubMed Central

    Ekmann, Anette; Thinggaard, Mikael; Christensen, Kaare; Avlund, Kirsten

    2014-01-01

    Background and aims Mobility-related fatigue is an important indicator of functional decline in old age, however, very little is known about fatigue in the oldest old population segment. The aim of this study was to examine the association between indoor mobility-related fatigue and muscle strength decline in nonagenarians. Methods The study is based on a prospective longitudinal study of all Danes born in 1905 and assessed in 1998, 2000 and 2003, and includes 92- to 93-year-old persons who were independent of help in basic indoor mobility at baseline (n = 1,353). Fatigue was assessed at baseline and defined as a subjective feeling of fatigue when transferring or walking indoors. The outcome measure, maximum grip strength, was measured at each measurement point. Results Grip strength declined throughout the study in participants with and without fatigue, but those reporting fatigue had significantly (P < .001) lower muscle strength during the entire study period. Longitudinal analyses indicated slightly slower decline in muscle strength among participants with fatigue compared to those without; however, observed selective dropout of participants with fatigue and poor performance at baseline needs to be considered when interpreting the results. Accordingly, participants without fatigue had significantly higher chances of being alive and having muscle strength above gender-specific median at first (RR 1.32, 95 % CI 1.07–1.58), second (RR 1.51, 1.06–1.96) and third (RR 1.39, 1.01–1.97) measurement points. Conclusions Indoor mobility-related fatigue in advanced later life should not merely be considered as an unpleasant symptom, but rather an indicator of physical impairment, and consequently declined physiological reserve. PMID:24297217

  4. Muscle strength and fatigue during isokinetic exercise in individuals with multiple sclerosis.

    PubMed

    Lambert, C P; Archer, R L; Evans, W J

    2001-10-01

    To compare muscle strength and muscle fatigue of the knee extensors and flexors in individuals with multiple sclerosis (MS) and non-MS control subjects and to evaluate the reliability of muscle strength and muscle fatigue testing in these individuals. Thirty individuals (13 women and 2 men for both MS and control groups), age (mean +/- SD) 38.8 +/- 10 for MS and 33.1 +/- 7.6 yr for controls, participated in this investigation. Peak torque was measured on two occasions separated by approximately 7 d at 30, 60, 90, 120, 180 degrees.s(-1) with 2 min of recovery between each bout. The nondominant leg was tested followed by the dominant leg after 10 min of recovery. Subjects then performed three bouts of 30 flexions and extensions of the dominant leg at 180 degrees.s(-1) with 1 min of recovery between bouts. The reliability of muscle torque was very high for individuals with MS (only 1 of 20 measurements with an ICC below 0.900). Total work was also highly reliable for MS, but the Fatigue Index (work during the last 15 contractions/work during the first 15 contractions) x 100 was not. Peak torque adjusted for age, body mass, and fat free mass (measured by whole body plethysmography; the Bod Pod; Life Measurement Instruments; Concord, CA) was significantly greater for controls than for MS for three of four lower body muscle groups tested. For the muscle fatigue test (3 bouts of 30 knee extensions and flexions at 180 degrees.s(-1)), the Fatigue Index was greater (less fatigue) for the knee extensors for controls than MS for the third bout. For flexion, the Fatigue Index was greater for controls than MS over the three bouts (group effect). Total work was significantly greater for controls than MS for the flexors (group effect) and approached significance for the extensors. Individuals with MS were weaker than controls when data were adjusted for age, body mass, and fat free mass. This latter finding (force relative to age and fat free mass) suggests that there is a reduced

  5. Isotretinoin treatment in patients with acne vulgaris: does it impact muscle strength, fatigue, and endurance?

    PubMed

    Yıldızgören, Mustafa Turgut; Rifaioğlu, Emine Nur; Demirkapı, Musa; Ekiz, Timur; Micooğulları, Ahmet; Şen, Tuğba; Turhanoğlu, Ayşe Dicle

    2015-07-01

    The objective of this study was to evaluate the effects of isotretinoin on muscle strength, fatigue, and endurance in patients with acne vulgaris. The study included 27 patients with acne vulgaris who underwent treatment with isotretinoin as well as 26 control patients for comparison. Participants in the treatment group received oral isotretinoin 0.5 mg/kg once daily for 1 month followed by an increased dose of 1 mg/kg once daily for 2 months. Isokinetic measurements were obtained from the hamstrings and quadriceps on the nondominant side of the body at baseline and 3-month follow-up using an isokinetic dynamometer. Results indicated that systemic isotretinoin did not significantly alter muscle strength, fatigue, and endurance.

  6. Exercise capacity, muscle strength, and fatigue in sarcoidosis: a follow-up study.

    PubMed

    Marcellis, Rik G J; Lenssen, Antoine F; Kleynen, Stephan; De Vries, Jolanda; Drent, Marjolein

    2013-06-01

    The purpose of this study was to examine changes in the prevalence of exercise intolerance, reduced muscle strength, and fatigue and the changes in these parameters in individual patients during a 2-year follow-up study. Ninety sarcoidosis patients (62 males and 28 females; mean age: 46.0 ± 10.2 years) participated in a 2-year follow-up study. At the baseline and follow-up measurements, patients performed a 6-min walk test and elbow flexor muscle strength, quadriceps peak torque, and hamstrings peak torque tests. Maximal inspiratory pressure was recorded. All patients completed the Fatigue Assessment Scale. Both at baseline and follow-up, a substantial proportion of the patients showed a reduced 6-minute walk test (41.6 and 34.8 %, respectively), elbow flexor muscle strength (6.7 and 14.6 %), quadriceps peak torque (21.3 and 18 %), hamstrings peak torque (13.5 and 12.4 %), and maximal inspiratory pressure (45.9 and 48.6 %). The majority of the patients reported fatigue (86 and 77 %). These physical impairments remained stable during the follow-up period. The prevalence of these physical impairments in patients diagnosed with sarcoidosis <2 years before inclusion in this study was similar to that in patients with a longer history of the disease. Exercise intolerance, muscle weakness, and fatigue are frequent problems in symptomatic sarcoidosis patients with a stable and persistent character. This study highlights that beyond medical treatment a rehabilitation program should be considered as adjunct therapy in the multidisciplinary management of sarcoidosis patients even though the achieved benefit needs future studies.

  7. Changes in muscle strength, relaxation rate and fatiguability during the human menstrual cycle.

    PubMed Central

    Sarwar, R; Niclos, B B; Rutherford, O M

    1996-01-01

    1. The effect of the different phases of the menstrual cycle on skeletal muscle strength, contractile properties and fatiguability was investigated in ten young, healthy females. Results were compared with a similar group on the combined (non-phasic) oral contraceptive pill (OC). Cycle phases were divided into the early and mid-follicular, mid-cycle (ovulatory) and mid- and late luteal. Cycle phases were estimated from the first day of the menstrual bleed. 2. Subjects were studied weekly through two complete cycles. Measurements included quadriceps and handgrip maximum voluntary isometric force and the relaxation times, force-frequency relationship and fatigue index of the quadriceps during percutaneous stimulation at a range of frequencies from 1 to 100 Hz. 3. In the women not taking the OC there was a significant increase of about 11% in quadriceps and handgrip strength at mid-cycle compared with both the follicular and luteal phases. Accompanying the increases in strength there was a significant slowing of relaxation and increase in fatiguability at mid-cycle. No changes in any parameter were found in the women taking the OC. 4. The changes in muscle function at mid-cycle may be due to the increase in oestrogen that occurs prior to ovulation. PMID:8735711

  8. Acute effects of Kinesio taping on muscle strength and fatigue in the forearm of tennis players.

    PubMed

    Zhang, Shen; Fu, Weijie; Pan, Jiahao; Wang, Lin; Xia, Rui; Liu, Yu

    2016-06-01

    To explore the immediate effects of Kinesio taping applied over the wrist extensors and flexors on muscle strength and endurance during isometric and isokinetic muscle actions. The study had a single-blinded, placebo control, and randomized design. Fourteen trained male volunteers were required to complete 5s isometric maximal voluntary contractions and 50 consecutive maximal concentric wrist extension and flexion repetitions at each of two angular speeds (60°/s and 210°/s) in three taping conditions: Kinesio taping (KT), placebo taping (PT), and no taping (NT). KT did not improve peak moment, peak power, average power, and total work for wrist extensors and flexors in the isometric and isokinetic contractions. However, KT showed a 13% decrease in work fatigue of the wrist flexors compare to NT (p=0.014) at 60°/s. Furthermore, a 20% decrease was also observed in the rate of decline of moment (k) of the wrist flexors in KT compared to NT (p=0.007), and the k in PT was also significantly lower in magnitude compared to NT (p=0.035). Moreover, there was also a trend in terms of magnitudes for kKTstrength production in healthy athletes immediately, but does have a significant positive effect on reducing muscle fatigue during repeated concentric muscle actions. Additionally, the potential beneficial effects of placebo taping on muscle endurance should not be ignored either. Copyright © 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  9. Muscle Deoxygenation Causes Muscle Fatigue

    NASA Technical Reports Server (NTRS)

    Murthy, G.; Hargens, A. R.; Lehman, S.; Rempel, D.

    1999-01-01

    Muscle fatigue is a common musculoskeletal disorder in the work place, and may be a harbinger for more disabling cumulative trauma disorders. Although the cause of fatigue is multifactorial, reduced blood flow and muscle oxygenation may be the primary factor in causing muscle fatigue during low intensity muscle exertion. Muscle fatigue is defined as a reduction in muscle force production, and also occurs among astronauts who are subjected to postural constraints while performing lengthy, repetitive tasks. The objectives of this research are to: 1) develop an objective tool to study the role of decreased muscle oxygenation on muscle force production, and 2) to evaluate muscle fatigue during prolonged glovebox work.

  10. Low ponderal index is associated with decreased muscle strength and fatigue resistance in college-aged women

    PubMed Central

    Brutsaert, Tom D.; Tamvada, Kelli H.; Kiyamu, Melisa; White, Daniel D.; Gage, Timothy B

    2011-01-01

    Poor fetal growth is associated with decrements in muscle strength likely due to changes during myogenesis. We investigated the association of poor fetal growth with muscle strength, fatigue resistance, and the response to training in the isolated quadriceps femoris. Females (20.6 yrs) born to term but below the 10th percentile of ponderal index (PI)-for-gestational-age (LOWPI, n=14) were compared to controls (HIGHPI, n=14), before and after an 8-week training. Muscle strength was assessed as grip-strength and as the maximal isometric voluntary contraction (MVC) of the quadriceps femoris. Muscle fatigue was assessed during knee extension eercise. Body composition and the maximal oxygen consumption (VO2max) were also measured. Controlling for fat free mass (FFM), LOWPI versus HIGHPI women had ~11% lower grip-strength (P=0.023), 9–24% lower MVC values (P=0.042 pre-trained; P=0.020 post-trained), a higher rate of fatigue (pre- and post-training), and a diminished training response (P=0.016). Statistical control for FFM increased rather than decreased strength differences between PI groups. The PI was not associated with VO2max or measures of body composition. Strength and fatigue decrements strongly suggest that poor fetal growth affects the pathway of muscle force generation. This could be due to neuromotor and/or muscle morphologic changes during development e.g., fiber number, fiber type, etc. Muscle from LOWPI women may also be less responsive to training. Indirectly, results also implicate muscle as a potential mediator between poor fetal growth and adult chronic disease, given muscle’s direct role in determining insulin resistance, type II diabetes, physical activity, and so forth. PMID:21641734

  11. 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.

  12. Muscle Fiber Type Composition and Knee Extension Isometric Strength Fatigue Patterns in Power- and Endurance-Trained Males.

    ERIC Educational Resources Information Center

    Kroll, Walter; And Others

    1980-01-01

    There is a degree of uniqueness in fatigue patterns, particularly between different levels of absolute maximum strength. Caution should be used when analyzing fatigue curves among subjects with unspecified strength levels. (CJ)

  13. Incubating Isolated Mouse EDL Muscles with Creatine Improves Force Production and Twitch Kinetics in Fatigue Due to Reduction in Ionic Strength

    PubMed Central

    Head, Stewart I.; Greenaway, Bronwen; Chan, Stephen

    2011-01-01

    Background Creatine supplementation can improve performance during high intensity exercise in humans and improve muscle strength in certain myopathies. In this present study, we investigated the direct effects of acute creatine incubation on isolated mouse fast-twitch EDL muscles, and examined how these effects change with fatigue. Methods and Results The extensor digitorum longus muscle from mice aged 12–14 weeks was isolated and stimulated with field electrodes to measure force characteristics in 3 different states: (i) before fatigue; (ii) immediately after a fatigue protocol; and (iii) after recovery. These served as the control measurements for the muscle. The muscle was then incubated in a creatine solution and washed. The measurement of force characteristics in the 3 different states was then repeated. In un-fatigued muscle, creatine incubation increased the maximal tetanic force. In fatigued muscle, creatine treatment increased the force produced at all frequencies of stimulation. Incubation also increased the rate of twitch relaxation and twitch contraction in fatigued muscle. During repetitive fatiguing stimulation, creatine-treated muscles took 55.1±9.5% longer than control muscles to lose half of their original force. Measurement of weight changes showed that creatine incubation increased EDL muscle mass by 7%. Conclusion Acute creatine application improves force production in isolated fast-twitch EDL muscle, and these improvements are particularly apparent when the muscle is fatigued. One likely mechanism for this improvement is an increase in Ca2+ sensitivity of contractile proteins as a result of ionic strength decreases following creatine incubation. PMID:21850234

  14. Fatigue and Muscle Strength Involving Walking Speed in Parkinson's Disease: Insights for Developing Rehabilitation Strategy for PD

    PubMed Central

    Chang, Fang-Yu; Liu, Wei-Chia; Chuang, Yu-Fen; Chuang, Li-Ling

    2017-01-01

    Background. Problems with gait in Parkinson's disease (PD) are a challenge in neurorehabilitation, partly because the mechanisms causing the walking disability are unclear. Weakness and fatigue, which may significantly influence gait, are commonly reported by patients with PD. Hence, the aim of this study was to investigate the association between weakness and fatigue and walking ability in patients with PD. Methods. We recruited 25 patients with idiopathic PD and 25 age-matched healthy adults. The maximum voluntary contraction (MVC), twitch force, and voluntary activation levels were measured before and after a knee fatigue exercise. General fatigue, central fatigue, and peripheral fatigue were quantified by exercise-induced changes in MVC, twitch force, and activation level. In addition, subjective fatigue was measured using the Multidimensional Fatigue Inventory (MFI) and Fatigue Severity Scale (FSS). Results. The patients with PD had lower activation levels, more central fatigue, and more subjective fatigue than the healthy controls. There were no significant differences in twitch force or peripheral fatigue index between the two groups. The reduction in walking speed was related to the loss of peripheral strength and PD itself. Conclusion. Fatigue and weakness of central origin were related to PD, while peripheral strength was important for walking ability. The results suggest that rehabilitation programs for PD should focus on improving both central and peripheral components of force. PMID:28321339

  15. Performance of muscle strength and fatigue tolerance in young trained women supplemented with caffeine.

    PubMed

    Fett, Carlos A; Magalhães Aquino, Natalia; Schantz, Jairo; Brandão, Camila F; de Araújo Cavalcanti, Joás D; Rezende Fett, Waleria C

    2017-04-13

    Verify the effect of caffeine supplementation on the muscular strength and fatigue tolerance of young trained women. Eight women of 25±5 years old, who had undergone a minimum of 12 months of continuous resisted training, body mass index 20-23 kg/m2 were submitted to four tests: one repetition maximum (1- RM, kg) to pull down (PD), hack squat (HS), bench press (BP), and; knee extension exhaustion (drop-set, 100/80/60 kg, repetitions) (DS). They perform the tests in four consecutive blocks one-week apart crossover system: basal without caffeine (B); first caffeine (C1); placebo with starch supplementation (P); second caffeine (C2). Caffeine supplementation 6 mg.kg-1 30 min before. The paired t test and repeated ANOVA with Tukey-Kramer were performed. Respectively for B, C1, P and C2 to each test were PD (52, 54, 56, 55, p>0.05); HS (99, 109, 108, 121*; p<0.001); BP (22, 26*, 25*, 27*; p<0.05); DS (28, 35*,**, 30*, 37**; p<0.001). To comparison of B, P and mean caffeine (C1+C2/2) results respectively were: HS (99, 108*, 115***; p<0.05); BP (22, 25*, 26*; p<0.05); DS (28, 30#, 36**; p<0.01 and p<0.001). The delta ((C1+C2/2)- (B+P/2)) were PD=0 (p>0.05), HS=12 (p=0.04), BP = 3 (p=0.007), DS = 7 (p=00.1). Caffeine improved tolerance to exhaustion and has tendency to improve strength in this young women. Probably caffeine supplementation is useful to improve performance in women engaged in sports with these physical valences. An investigation with a major numbers of volunteers could elucidate some controversies observed here.

  16. Deer Antler Extract Improves Fatigue Effect through Altering the Expression of Genes Related to Muscle Strength in Skeletal Muscle of Mice.

    PubMed

    Chen, Jaw-Chyun; Hsiang, Chien-Yun; Lin, Yung-Chang; Ho, Tin-Yun

    2014-01-01

    Deer antler is a well-known traditional Chinese medicine used in Asian countries for the tonic and the improvement of aging symptoms. The present study was designed to investigate the antifatigue effect and mechanism of Formosan sambar deer tip antler extract (FSDTAE). The swimming times to exhaustion of mice administered FSDTAE (8.2 mg/day) for 28 days were apparently longer than those of the vehicle-treated mice in forced swim test. However, the indicators of fatigue, such as the reduction in glucose level and the increases in blood urea nitrogen and lactic acid levels, were not significantly inhibited by FSDTAE. Therefore, microarray analysis was further used to examine the anti-fatigue mechanism of FSDTAE. We selected genes with fold changes >2 or <-2 in skeletal muscle for pathway analysis. FSDTAE-affected genes were involved in 9 different signaling pathways, such as GnRH signaling pathway and insulin signaling pathway. All of the significantly expressed genes were classified into 8 different categories by their functions. The most enriched category was muscular system, and 6 upregulated genes, such as troponin I, troponin T1, cysteine and glycine-rich protein 2, myosin heavy polypeptide 7, tropomyosin 2, and myomesin family member 3, were responsible for the development and contraction of muscle. Real-time PCR analysis indicated that FSDTAE increased troponins mRNA expression in skeletal muscle. In conclusion, our findings suggested that FSDTAE might increase the muscle strength through the upregulation of genes responsible for muscle contraction and consequently exhibited the anti-fatigue effect in mice.

  17. An indentation fatigue strength law

    NASA Astrophysics Data System (ADS)

    Xu, Baoxing; Yonezu, Akio; Chen, Xi

    2010-05-01

    Indentation fatigue, where a cyclic load is applied on the sample via an indenter, emerges as an alternative approach for measuring the fatigue properties of materials. We have carried out indentation fatigue tests on a poly(vinyl chloride) (PVC) bulk material, as well as on TiN and NiP films/coatings deposited on SUS304 steel substrates, and demonstrate that a simple power-law relationship can be established between the indentation load amplitude and number of cycles to failure. Such a law is very similar to the conventional fatigue strength law obtained from uniaxial tests. The agreement between the fatigue stress exponents obtained by uniaxial and indentation fatigue tests suggests the potential applicability of the indentation fatigue technique for extracting the fatigue properties of materials.

  18. Ischemia causes muscle fatigue

    NASA Technical Reports Server (NTRS)

    Murthy, G.; Hargens, A. R.; Lehman, S.; Rempel, D. M.

    2001-01-01

    The purpose of this investigation was to determine whether ischemia, which reduces oxygenation in the extensor carpi radialis (ECR) muscle, causes a reduction in muscle force production. In eight subjects, muscle oxygenation (TO2) of the right ECR was measured noninvasively and continuously using near infrared spectroscopy (NIRS) while muscle twitch force was elicited by transcutaneous electrical stimulation (1 Hz, 0.1 ms). Baseline measurements of blood volume, muscle oxygenation and twitch force were recorded continuously, then a tourniquet on the upper arm was inflated to one of five different pressure levels: 20, 40, 60 mm Hg (randomized order) and diastolic (69 +/- 9.8 mm Hg) and systolic (106 +/- 12.8 mm Hg) blood pressures. Each pressure level was maintained for 3-5 min, and was followed by a recovery period sufficient to allow measurements to return to baseline. For each respective tourniquet pressure level, mean TO2 decreased from resting baseline (100% TO2) to 99 +/- 1.2% (SEM), 96 +/- 1.9%, 93 +/- 2.8%, 90 +/- 2.5%, and 86 +/- 2.7%, and mean twitch force decreased from resting baseline (100% force) to 99 +/- 0.7% (SEM), 96 +/- 2.7%, 93 +/- 3.1%, 88 +/- 3.2%, and 86 +/- 2.6%. Muscle oxygenation and twitch force at 60 mm Hg tourniquet compression and above were significantly lower (P < 0.05) than baseline value. Reduced twitch force was correlated in a dose-dependent manner with reduced muscle oxygenation (r = 0.78, P < 0.001). Although the correlation does not prove causation, the results indicate that ischemia leading to a 7% or greater reduction in muscle oxygenation causes decreased muscle force production in the forearm extensor muscle. Thus, ischemia associated with a modest decline in TO2 causes muscle fatigue.

  19. Ischemia causes muscle fatigue

    NASA Technical Reports Server (NTRS)

    Murthy, G.; Hargens, A. R.; Lehman, S.; Rempel, D. M.

    2001-01-01

    The purpose of this investigation was to determine whether ischemia, which reduces oxygenation in the extensor carpi radialis (ECR) muscle, causes a reduction in muscle force production. In eight subjects, muscle oxygenation (TO2) of the right ECR was measured noninvasively and continuously using near infrared spectroscopy (NIRS) while muscle twitch force was elicited by transcutaneous electrical stimulation (1 Hz, 0.1 ms). Baseline measurements of blood volume, muscle oxygenation and twitch force were recorded continuously, then a tourniquet on the upper arm was inflated to one of five different pressure levels: 20, 40, 60 mm Hg (randomized order) and diastolic (69 +/- 9.8 mm Hg) and systolic (106 +/- 12.8 mm Hg) blood pressures. Each pressure level was maintained for 3-5 min, and was followed by a recovery period sufficient to allow measurements to return to baseline. For each respective tourniquet pressure level, mean TO2 decreased from resting baseline (100% TO2) to 99 +/- 1.2% (SEM), 96 +/- 1.9%, 93 +/- 2.8%, 90 +/- 2.5%, and 86 +/- 2.7%, and mean twitch force decreased from resting baseline (100% force) to 99 +/- 0.7% (SEM), 96 +/- 2.7%, 93 +/- 3.1%, 88 +/- 3.2%, and 86 +/- 2.6%. Muscle oxygenation and twitch force at 60 mm Hg tourniquet compression and above were significantly lower (P < 0.05) than baseline value. Reduced twitch force was correlated in a dose-dependent manner with reduced muscle oxygenation (r = 0.78, P < 0.001). Although the correlation does not prove causation, the results indicate that ischemia leading to a 7% or greater reduction in muscle oxygenation causes decreased muscle force production in the forearm extensor muscle. Thus, ischemia associated with a modest decline in TO2 causes muscle fatigue.

  20. Sites of Failure in Muscle Fatigue

    DTIC Science & Technology

    2001-10-25

    sites associated with muscle fatigue. Keywords - Fatigue, failure, site, muscle. I. INTRODUCTION Neuromuscular fatigue impairs the force...generating capacity of muscles and it is experienced commonly in normal everyday physical exercise and especially in neuromuscular diseases...Despite significant progress in research on muscle fatigue, “remarkably little is known of the mechanisms underlying neuromuscular fatigue during human

  1. Effect of fatigue caused by a simulated handball game on ball throwing velocity, shoulder muscle strength and balance ratio: a prospective study.

    PubMed

    Andrade, Marília Santos; de Carvalho Koffes, Fabiana; Benedito-Silva, Ana Amélia; da Silva, Antonio Carlos; de Lira, Claudio Andre Barbosa

    2016-01-01

    Arm throwing represents a deciding element in handball. Ball velocity, aim accuracy, and dynamic stability of the shoulder are factors that influence throwing effectiveness. The purpose of this study was to examine the influence of muscle fatigue caused by simulated game activities (SGA) on shoulder rotational isokinetic muscle strength, muscle balance and throwing performance, and to examine the relationship between muscle strength and throwing performance. Ten national elite adult handball athletes were evaluated. Isokinetic internal (IR), external (ER) rotators peak torque, and balance ratio were measured before and after SGA. Ball throwing velocity was assessed by radar gun. Both internal (IR) and external (ER) rotators peak torque were significantly lower after SGA (p = 0.0003 and p = 0.02, respectively). However, the deleterious effect was more evident for IR than ER muscles (effect size r = 0.39 and r = 0.18, respectively). Balance ratio before and after SGA did not differ (p = 0.06). Ball throwing velocity was not impaired by SGA. Moreover, isokinetic variables correlated positively with ball velocity (r ≥ 0.67). SGA affected the muscle strength of IR more than ER, predisposing the shoulder joint to muscular imbalance. The muscular impairment after SGA was insufficient to impair ball throwing velocity.

  2. Low dynamic muscle strength and its associations with fatigue, functional performance, and quality of life in premenopausal patients with systemic lupus erythematosus and low disease activity: a case-control study.

    PubMed

    Balsamo, Sandor; da Mota, Licia Maria Henrique; de Carvalho, Jozélio Freire; Nascimento, Dahan da Cunha; Tibana, Ramires Alsamir; de Santana, Frederico Santos; Moreno, Ricardo Lima; Gualano, Bruno; dos Santos-Neto, Leopoldo

    2013-09-08

    The purpose of the present study was to compare dynamic muscle strength, functional performance, fatigue, and quality of life in premenopausal systemic lupus erythematosus (SLE) patients with low disease activity versus matched-healthy controls and to determine the association of dynamic muscle strength with fatigue, functional performance, and quality of life in SLE patients. We evaluated premenopausal (18-45 years) SLE patients with low disease activity (Systemic lupus erythematosus disease activity index [SLEDAI]: mean 1.5 ± 1.2). The control (n = 25) and patient (n = 25) groups were matched by age, physical characteristics, and the level of physical activities in daily life (International Physical Activity Questionnaire IPAQ). Both groups had not participated in regular exercise programs for at least six months prior to the study. Dynamic muscle strength was assessed by one-repetition maximum (1-RM) tests. Functional performance was assessed by the Timed Up and Go (TUG), in 30-s test a chair stand and arm curl using a 2-kg dumbbell and balance test, handgrip strength and a sit-and-reach flexibility test. Quality of life (SF-36) and fatigue were also measured. The SLE patients showed significantly lower dynamic muscle strength in all exercises (leg press 25.63%, leg extension 11.19%, leg curl 15.71%, chest press 18.33%, lat pulldown 13.56%, 1-RM total load 18.12%, P < 0.001-0.02) compared to the controls. The SLE patients also had lower functional performance, greater fatigue and poorer quality of life. In addition, fatigue, SF-36 and functional performance accounted for 52% of the variance in dynamic muscle strength in the SLE patients. Premenopausal SLE patients with low disease activity showed lower dynamic muscle strength, along with increased fatigue, reduced functional performance, and poorer quality of life when compared to matched controls.

  3. Factors which affect fatigue strength of fasteners

    SciTech Connect

    Skochko, G.W.; Herrmann, T.P.

    1992-11-01

    Axial load cycling fatigue tests of threaded fasteners are useful in determining fastener fatigue failure or design properties. By using appropriate design factors between the failure and design fatigue strengths, such tests are used to establish fatigue failure and design parameters of fasteners for axial and bending cyclic load conditions. This paper reviews the factors which influence the fatigue strength of low Alloy steel threaded fasteners, identifies those most significant to fatigue strength, and provides design guidelines based on the direct evaluation of fatigue tests of threaded fasteners. Influences on fatigue strength of thread manufacturing process (machining and rolling of threads), effect of fastener membrane and bending stresses, thread root radii, fastener sizes, fastener tensile strength, stress relaxation, mean stress, and test temperature are discussed.

  4. 14 CFR 23.627 - Fatigue strength.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Fatigue strength. 23.627 Section 23.627... Fatigue strength. The structure must be designed, as far as practicable, to avoid points of stress concentration where variable stresses above the fatigue limit are likely to occur in normal service....

  5. 14 CFR 23.627 - Fatigue strength.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Fatigue strength. 23.627 Section 23.627... Fatigue strength. The structure must be designed, as far as practicable, to avoid points of stress concentration where variable stresses above the fatigue limit are likely to occur in normal service....

  6. 14 CFR 23.627 - Fatigue strength.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Fatigue strength. 23.627 Section 23.627... Fatigue strength. The structure must be designed, as far as practicable, to avoid points of stress concentration where variable stresses above the fatigue limit are likely to occur in normal service....

  7. 14 CFR 23.627 - Fatigue strength.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Fatigue strength. 23.627 Section 23.627... Fatigue strength. The structure must be designed, as far as practicable, to avoid points of stress concentration where variable stresses above the fatigue limit are likely to occur in normal service....

  8. A randomized controlled trial on the effects of combined aerobic-resistance exercise on muscle strength and fatigue, glycemic control and health-related quality of life of type 2 diabetes patients.

    PubMed

    Tomas-Carus, Pablo; Ortega-Alonso, Alfredo; Pietilainen, Kirsi H; Santos, Vitoria; Goncalves, Helena; Ramos, Jorge; Raimundo, Armando

    2016-05-01

    The aim of this paper was to evaluate the effects of a 12-weeks combined aerobic-resistance exercise therapy on fatigue and isokinetic muscle strength, glycemic control and health-related quality of life (HRQoL) in moderately affected type 2 diabetes (T2DM) patients. A randomized controlled trial design was employed. Forty-three T2DM patients were assigned to an exercise group (N.=22), performing 3 weekly sessions of 60 minutes of combined aerobic-resistance exercise for 12-weeks; or a no exercise control group (N.=21). Both groups were evaluated at a baseline and after 12-weeks of exercise therapy for: 1) muscle strength and fatigue by isokinetic dynamometry; 2) plasma glycated hemoglobin A1C (HbA1C); and 3) HRQoL utilizing the SF-36 questionnaire. The exercise therapy led to improvements in muscle fatigue in knee extensors (-55%) and increased muscle strength in knee flexors and extensors (+15 to +30%), while HbA1C decreased (-18%). In addition, the exercising patients showed sizeable improvements in HRQoL: physical function (+53%), vitality (+21%) and mental health (+40%). Twelve-weeks of combined aerobic-resistance exercise was highly effective to improve muscle strength and fatigue, glycemic control and several aspects of HRQoL in T2DM patients. These data encourage the use of aerobic and resistance exercise in the good clinical care of T2DM.

  9. Human quadriceps strength and fatiguability in patients with post viral fatigue.

    PubMed Central

    Rutherford, O M; White, P D

    1991-01-01

    Quadriceps isometric strength, activation and fatiguability were measured in 11 patients with symptoms of fatigue three months after glandular fever or a glandular fever-like illness. Predicted normal and lower limits of normal muscle strength were calculated from height and age. These measures and the fatigue index were compared with a group of healthy students of similar age. Two of the patients were unable to activate fully their muscles. After allowing for this inhibition the group mean (SD) strength was 104 (22%) of predicted. Although there was no significant difference in the fatigue index between the patients and the control group, there was a trend for the patients to show less fatigue than controls. There was no difference in the muscle results for those patients who were found to have Epstein-Barr virus infections and those who did not. The feelings of weakness and fatigue experienced by the patients could not be explained by either physiological muscle fatigue or lack of effort. PMID:1800667

  10. Assessment of muscle fatigue using electromygraphm sensing

    NASA Astrophysics Data System (ADS)

    Helmi, Muhammad Hazimin Bin; Ping, Chew Sue; Ishak, Nur Elliza Binti; Saad, Mohd Alimi Bin Mohd; Mokhtar, Anis Shahida Niza Binti

    2017-08-01

    Muscle fatigue is condition of muscle decline in ability after undergoing any physical activity. Observation of the muscle condition of an athlete during training is crucial to prevent or minimize injury and able to achieve optimum performance in actual competition. The aim of this project is to develop a muscle monitoring system to detect muscle fatigue in swimming athlete. This device is capable to measure muscle stress level of the swimmer and at the same time provide indication of muscle fatigue level to trainer. Electromyography signal was recorded from the muscle movement while practicing the front crawl stroke repetitively. The time domain data was processed to frequency spectra in order to study the effect of muscle fatigue. The results show that the recorded EMG signal is able to sense muscle fatigue.

  11. 14 CFR 23.627 - Fatigue strength.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Fatigue strength. 23.627 Section 23.627 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... Fatigue strength. The structure must be designed, as far as practicable, to avoid points of...

  12. Controlled Frequency Breathing Reduces Inspiratory Muscle Fatigue.

    PubMed

    Burtch, Alex R; Ogle, Ben T; Sims, Patrick A; Harms, Craig A; Symons, T Brock; Folz, Rodney J; Zavorsky, Gerald S

    2017-05-01

    Burtch, AR, Ogle, BT, Sims, PA, Harms, CA, Symons, TB, Folz, RJ, and Zavorsky, GS. Controlled frequency breathing reduces inspiratory muscle fatigue. J Strength Cond Res 31(5): 1273-1281, 2017-Controlled frequency breathing (CFB) is a common swim training modality involving holding one's breath for approximately 7-10 strokes before taking another breath. We sought to examine the effects of CFB training on reducing respiratory muscle fatigue. Competitive college swimmers were randomly divided into either the CFB group that breathed every 7-10 strokes or a control group that breathed every 3-4 strokes. Twenty swimmers completed the study. The training intervention included 5-6 weeks (16 sessions) of 12 × 50-m repetitions with breathing 8-10 breaths per 50-m (control group) or 2-3 breaths per 50-m (CFB group). Inspiratory muscle fatigue was defined as the decrease in maximal inspiratory pressure (MIP) between rest and 46 seconds after a 200-yard freestyle swimming race (115 seconds [SD 7]). Aerobic capacity, pulmonary diffusing capacity, and running economy were also measured pre- and posttraining. Pooled results demonstrated a 12% decrease in MIP at 46 seconds post-race (-15 [SD 14] cm H2O, effect size = -0.48, p < 0.01). After 4 weeks of training, only the CFB group prevented a decline in MIP values before to 46 seconds after race (-2 [13] cm H2O, p > 0.05). However, swimming performance, aerobic capacity, pulmonary diffusing capacity, and running economy did not improve (p > 0.05) posttraining in either group. In conclusion, CFB training appears to prevent inspiratory muscle fatigue; yet, no difference was found in performance outcomes.

  13. Fatigue Strength of Airplane and Engine Materials

    NASA Technical Reports Server (NTRS)

    Matthaes, Kurt

    1934-01-01

    This report was undertaken to give a brief summary of the laws governing the fatigue stresses and of the most important strength coefficients necessary for the correct dimensioning of the structural members.

  14. Effect of formoterol, a long-acting β2-adrenergic agonist, on muscle strength and power output, metabolism, and fatigue during maximal sprinting in men.

    PubMed

    Kalsen, Anders; Hostrup, Morten; Backer, Vibeke; Bangsbo, Jens

    2016-06-01

    The aim was to investigate the effect of the long-acting β2-adrenergic agonist formoterol on muscle strength and power output, muscle metabolism, and phosphorylation of CaMKII Thr(287) and FXYD1 during maximal sprinting. In a double-blind crossover study, 13 males [V̇o2 max: 45.0 ± 0.2 (means ± SE) ml·min(-1)·kg(-1)] performed a 30-s cycle ergometer sprint after inhalation of either 54 μg of formoterol (FOR) or placebo (PLA). Before and after the sprint, muscle biopsies were collected from vastus lateralis and maximal voluntary contraction (MVC), and contractile properties of quadriceps were measured. Oxygen uptake was measured during the sprint. During the sprint, peak power, mean power, and end power were 4.6 ± 0.8, 3.9 ± 1.1, and 9.5 ± 3.2% higher (P < 0.05) in FOR than in PLA, respectively. Net rates of glycogenolysis and glycolysis were 45.7 ± 21.0 and 28.5 ± 13.4% higher (P < 0.05) in FOR than in PLA, respectively, and the decrease in ATP content was lower (P < 0.05) in FOR than in PLA (3.7 ± 1.5 vs. 8.0 ± 1.6 mmol/kg dry weight). There was no difference in breakdown of phosphocreatine and oxygen uptake between treatments. Before and after the sprint, MVC and peak twitch force were higher (P < 0.05) in FOR than in PLA. No differences were observed in phosphorylation of CaMKII Thr(287) and FXYD1 between treatments before the sprint, whereas phosphorylation of CaMKII Thr(287) and FXYD1 was greater (P < 0.05) in FOR than in PLA after the sprint. In conclusion, formoterol-induced enhancement in power output during maximal sprinting is associated with increased rates of glycogenolysis and glycolysis that may counteract development of fatigue.

  15. Strength gradient enhances fatigue resistance of steels

    PubMed Central

    Ma, Zhiwei; Liu, Jiabin; Wang, Gang; Wang, Hongtao; Wei, Yujie; Gao, Huajian

    2016-01-01

    Steels are heavily used in infrastructure and the transportation industry, and enhancing their fatigue resistance is a major challenge in materials engineering. In this study, by introducing a gradient microstructure into 304 austenitic steel, which is one of the most widely used types of stainless steel, we show that a strength gradient substantially enhances the fatigue life of the material. Pre-notched samples with negative strength gradients in front of the notch’s tip endure many more fatigue cycles than do samples with positive strength gradients during the crack initiation stage, and samples with either type of gradient perform better than do gradient-free samples with the same average yield strength. However, as a crack grows, samples with positive strength gradients exhibit better resistance to fatigue crack propagation than do samples with negative gradients or no gradient. This study demonstrates a simple and promising strategy for using gradient structures to enhance the fatigue resistance of materials and complements related studies of strength and ductility. PMID:26907708

  16. Fatiguing exercise enhances hyperalgesia to muscle inflammation.

    PubMed

    Sluka, Kathleen A; Rasmussen, Lynn A

    2010-02-01

    Since many people with chronic fatigue present with pain and many people with chronic pain present with fatigue, we tested if fatigue would enhance the response to pain in male and female mice. We further tested for the activation of brainstem nuclei by the fatigue task using c-fos as a marker. Fatigue was induced by having mice spontaneously run in running wheel for 2h. Carrageenan (0.03%) was injected into the gastrocnemius muscle either 2h before or 2h after the fatigue task. The mechanical sensitivity of the paw (von Frey filaments), muscle (tweezers), grip force and running wheel activity was assessed before and 24h after injection of carrageenan. Both male and female mice that performed the fatigue task, either before or after intramuscular injection of carrageenan, showed an enhanced mechanical sensitivity of the paw, but not the muscle. Ovariectomized mice showed a similar response to male mice. There was a decrease in running wheel activity after carrageenan injection, but no change in grip force suggesting that mice had no deficit in motor performance induced by the carrageenan. C-fos expression was observed in the nucleus raphe pallidus, obscurus, and magnus after the fatigue task suggesting an increased activity in the raphe nuclei in response to the fatigue task. Therefore, widespread hyperalgesia is enhanced by the fatigue response but not hyperalgesia at the site of insult. We suggest that this effect is sex-dependent and involves mechanisms in the brainstem to result in an enhanced hyperalgesia.

  17. Transcranial magnetic stimulation and human muscle fatigue.

    PubMed

    Taylor, J L; Gandevia, S C

    2001-01-01

    During exercise, changes occur at many sites in the motor pathway, including the muscle fiber, motoneuron, motor cortex, and "upstream" of the motor cortex. Some of the changes result in fatigue, which can be defined as a decrease in ability to produce maximal muscle force voluntarily. Transcranial magnetic stimulation (TMS) over the human motor cortex reveals changes in both motor evoked potentials (MEPs) and the silent period during and after fatiguing voluntary contractions in normal subjects. The relationship of these changes to loss of force or fatigue is unclear. However, during a sustained maximal contraction TMS evokes extra force from the muscle and thus demonstrates the development of suboptimal output from the motor cortex, that is, fatigue at a supraspinal level. In some patients with symptoms of fatigue, the response to TMS after exercise is altered, but the changed MEP behavior is not yet linked to particular symptoms or pathology.

  18. Training effects on muscle fatigue in man.

    PubMed

    Duchateau, J; Hainaut, K

    1984-01-01

    Effects of 3 months training, on electrical and mechanical failures during fatigue, were studied in human adductor pollicis muscle. Eight subjects carried out a daily training program of 10 series of 20 fast (0.5 s) voluntary contractions, against a load equivalent to 30-40% of the muscle maximal force. Contractile properties in control and trained muscles are tested by delivering supramaximal electrical pulses (30 Hz) to the motor nerve, thereby triggering series of 60 1-s contractions separated by 1-s intervals. Training produces significant increase in tension development during a 30 Hz isometric tetanus (+ 13%; P less than 0.001). Concimitant rates of tension development and of relaxation are respectively augmented by + 18% (P less than 0.001) and + 12% (P less than 0.001). No significant change of surface muscle action potential (SAP) is observed after training. The considerable loss of force recorded during fatigue in control muscles (-36%) is significantly smaller (P less than 0.001) after training (-17%). Slowing of tension development and of tension relaxation, observed during fatigue in control muscles (respectively -47% and -79%) is smaller after training (respectively -28% and -65%). Analysis of electrical failure indicates that training significantly (P less than 0.01) reduces augmentation of muscle SAP duration and area recorded during fatigue. Comparison of time courses of mechanical and electrical failures in control and trained muscles, supports the idea that intracellular processes play the major role in tension decay associated with fatigue in human adductor pollicis muscle.

  19. Trunk extensor muscle fatigue influences trunk muscle activities.

    PubMed

    Hoseinpoor, Tahere Seyed; Kahrizi, Sedighe; Mobini, Bahram

    2015-01-01

    Trunk muscles fatigue is one of the risk factors in workplaces and daily activities. Loads would be redistributed among active and passive tissues in a non-optimal manner in fatigue conditions. Therefore, a single tissue might be overloaded with minimal loads and as a result the risk of injury would increase. The goal of this paper was to assess the electromyographic response of trunk extensor and abdominal muscles after trunk extensor muscles fatigue induced by cyclic lifting task. This was an experimental study that twenty healthy women participated. For assessing automatic response of trunk extensor and abdominal muscles before and after the fatigue task, electromyographic activities of 6 muscles: thorasic erector spine (TES), lumbar erector spine (LES), lumbar multifidus (LMF), transverse abdominis/ internal oblique (TrA/IO), rectus abdominis (RA) and external oblique (EO) were recorded in standing position with no load and symmetric axial loads equal to 25% of their body weights. Statistical analysis showed that all the abdominal muscles activity decreased with axial loads after performing fatigue task but trunk extensor activity remained constant. Results of the current study indicated that muscle recruitment strategies changed with muscle fatigue and load bearing, therefore risks of tissue injury may increase in fatigue conditions.

  20. Muscle Strength and Poststroke Hemiplegia: A Systematic Review of Muscle Strength Assessment and Muscle Strength Impairment.

    PubMed

    Kristensen, Otto H; Stenager, Egon; Dalgas, Ulrik

    2017-02-01

    To systematically review (1) psychometric properties of criterion isokinetic dynamometry testing of muscle strength in persons with poststroke hemiplegia (PPSH); and (2) literature that compares muscle strength in patients poststroke with that in healthy controls assessed by criterion isokinetic dynamometry. A systematic literature search of 7 databases was performed. Included studies (1) enrolled participants with definite poststroke hemiplegia according to defined criteria; (2) assessed muscle strength or power by criterion isokinetic dynamometry; (3) had undergone peer review; and (4) were available in English or Danish. The psychometric properties of isokinetic dynamometry were reviewed with respect to reliability, validity, and responsiveness. Furthermore, comparisons of strength between paretic, nonparetic, and comparable healthy muscles were reviewed. Twenty studies covering 316 PPSH were included. High intraclass correlation coefficient (ICC) inter- and intrasession reliability was reported for isokinetic dynamometry, which was independent of the tested muscle group, contraction mode, and contraction velocity. Slightly higher ICC values were found for the nonparetic extremity. Standard error of the mean (SEM) values showed that a change of 7% to 20% was required for a real group change to take place for most muscle groups, with the knee extensors showing the smallest SEM% values. The muscle strength of paretic muscles showed deficits when compared with both healthy and nonparetic muscles, independent of muscle group, contraction mode, and contraction velocity. Nonparetic muscles only showed minor strength impairments when compared with healthy muscles. Criterion isokinetic dynamometry is a reliable test in persons with stroke, generally showing marked reductions in muscle strength of paretic and, to a lesser degree, nonparetic muscles when compared with healthy controls, independent of muscle group, contraction mode, and contraction velocity. Copyright

  1. Recovery Effect of the Muscle Fatigue by the Magnetic Stimulation

    NASA Astrophysics Data System (ADS)

    Uchida, Kousuke; Nuruki, Atsuo; Tsujimura, Sei-Ichi; Tamari, Youzou; Yunokuchi, Kazutomo

    The purpose of this study is to investigate the effect of magnetic stimulation for muscle fatigue. The six healthy subjects participated in the experiment with the repetition grasp using a hand dynamometer. The measurement of EMG (electromyography) and MMG (mechanomyography) is performed on the left forearm. All subjects performed MVC (maximum voluntary contraction), and repeated exercise in 80%MVC after the MVC measurement. The repetition task was entered when display muscular strength deteriorated. We used an EMG and MMG for the measurement of the muscle fatigue. Provided EMG and MMG waves were calculated integral calculus value (iEMG, and iMMG). The result of iEMG and iMMG were divided by muscular strength, because we calculate integral calculus value per the unit display muscular strength. The result of our study, we found recovery effect by the magnetic stimulation in voluntarily muscular strength and iEMG. However, we can not found in a figure of iMMG.

  2. 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.

  3. The effect of fatigue on knee position sense is not dependent upon the muscle group fatigued.

    PubMed

    Ribeiro, Fernando; Venâncio, João; Quintas, Pedro; Oliveira, José

    2011-08-01

    Muscle fatigue could have a greater impact on position sense when antagonists of the movement are fatigued. Hence, this study aimed to compare the effects of antagonist and agonist exercise-induced muscle fatigue on knee joint position sense. This within-subjects repeated-measures study included 40 subjects. Knee position sense and muscle strength were measured before and after two exercise protocols consisting of 30 consecutive maximal concentric/eccentric contractions of the knee extensors or flexors on the isokinetic dynamometer at an angular velocity of 180°/s (3.14 rad/s). Both exercise protocols increased the absolute angular error (F(1.78) = 39.89, P < 0.001; knee extensors protocol from 2.0 ± 1.3° to 3.5 ± 2.0°, knee flexors protocol from 2.1 ± 1.2° to 3.7 ± 2.2°), and no differences were detected between protocols (F(1.78) = 0.034, P = 0.855). No changes were observed in the relative angular error. Muscle fatigue affects knee position sense, and the deleterious effect is not different depending upon the muscle group fatigued. Copyright © 2011 Wiley Periodicals, Inc.

  4. High-Strength Bolt Corrosion Fatigue Life Model and Application

    PubMed Central

    Hui-li, Wang; Si-feng, Qin

    2014-01-01

    The corrosion fatigue performance of high-strength bolt was studied. Based on the fracture mechanics theory and the Gerberich-Chen formula, the high-strength bolt corrosion fracture crack model and the fatigue life model were established. The high-strength bolt crack depth and the fatigue life under corrosion environment were quantitatively analyzed. The factors affecting high-strength bolt corrosion fatigue life were discussed. The result showed that the high-strength bolt corrosion fracture biggest crack depth reduces along with the material yield strength and the applied stress increases. The material yield strength was the major factor. And the high-strength bolt corrosion fatigue life reduced along with the increase of material strength, the applied stress or stress amplitude. The stress amplitude influenced the most, and the material yield strength influenced the least. Low bolt strength and a low stress amplitude level could extend high-strength bolt corrosion fatigue life. PMID:25152916

  5. High-strength bolt corrosion fatigue life model and application.

    PubMed

    Hui-li, Wang; Si-feng, Qin

    2014-01-01

    The corrosion fatigue performance of high-strength bolt was studied. Based on the fracture mechanics theory and the Gerberich-Chen formula, the high-strength bolt corrosion fracture crack model and the fatigue life model were established. The high-strength bolt crack depth and the fatigue life under corrosion environment were quantitatively analyzed. The factors affecting high-strength bolt corrosion fatigue life were discussed. The result showed that the high-strength bolt corrosion fracture biggest crack depth reduces along with the material yield strength and the applied stress increases. The material yield strength was the major factor. And the high-strength bolt corrosion fatigue life reduced along with the increase of material strength, the applied stress or stress amplitude. The stress amplitude influenced the most, and the material yield strength influenced the least. Low bolt strength and a low stress amplitude level could extend high-strength bolt corrosion fatigue life.

  6. Biomarkers of peripheral muscle fatigue during exercise

    PubMed Central

    2012-01-01

    Background Biomarkers of peripheral muscle fatigue (BPMFs) are used to offer insights into mechanisms of exhaustion during exercise in order to detect abnormal fatigue or to detect defective metabolic pathways. This review aims at describing recent advances and future perspectives concerning the most important biomarkers of muscle fatigue during exercise. Results BPMFs are classified according to the mechanism of fatigue related to adenosine-triphosphate-metabolism, acidosis, or oxidative-metabolism. Muscle fatigue is also related to an immunological response. impaired calcium handling, disturbances in bioenergetic pathways, and genetic responses. The immunological and genetic response may make the muscle susceptible to fatigue but may not directly cause muscle fatigue. Production of BPMFs is predominantly dependent on the type of exercise. BPMFs need to change as a function of the process being monitored, be stable without appreciable diurnal variations, correlate well with exercise intensity, and be present in detectable amounts in easily accessible biological fluids. The most well-known BPMFs are serum lactate and interleukin-6. The most widely applied clinical application is screening for defective oxidative metabolism in mitochondrial disorders by means of the lactate stress test. The clinical relevance of most other BPMFs, however, is under debate, since they often depend on age, gender, physical fitness, the energy supply during exercise, the type of exercise needed to produce the BPMF, and whether healthy or diseased subjects are investigated. Conclusions Though the role of BPMFs during fatigue is poorly understood, measuring BPMFs under specific, standardised conditions appears to be helpful for assessing biological states or processes during exercise and fatigue. PMID:23136874

  7. Change in manipulation with muscle fatigue.

    PubMed

    Todd, Gabrielle; Gandevia, Simon C; Taylor, Janet L

    2010-11-01

    Muscle fatigue is defined as an exercise-induced reduction in the force-generating capacity of muscle. Here, we investigated the effect of muscle fatigue on hand dexterity. Healthy adults (n = 17) gripped and lifted an object (0.342 kg) five times before and after two interventions. The interventions, performed on separate days, involved 2 min of rest (control) or sustained maximal pinch grip that reduced maximal force by 60% (fatigue). Horizontal grip force (GF), vertical lift force (LF) and first dorsal interosseous electromyographic activity (EMG) were measured. The lift (dynamic) and hold (stationary) phase of the task were analysed. Before the intervention, there was no significant difference between the control and fatigue conditions for the 15 measured parameters. However, post-intervention GF was reduced with fatigue compared with the control condition (hold phase), whereas GF coefficient of variation (hold phase) and root mean square EMG (lift phase) increased with fatigue. Fatigue also disrupted the temporal relationship between GF and LF (assessed by cross-correlation of the derivative of GF and LF). The maximum cross-correlation coefficient was significantly reduced with fatigue compared with the control condition. Grip strategy and the kinetics of the lifting movement (minimum LF, maximum LF, maximum derivative of LF, and maximum acceleration) were unchanged with fatigue. Our results suggest that fatigued subjects generate more EMG to lift and hold an object but produce less force and are less able to match changes in LF with changes in GF. Fatigued subjects also exhibit greater fluctuation in GF while holding objects.

  8. Inspiratory muscle strength in chronic obstructive pulmonary disease.

    PubMed

    Larson, Janet L; Covey, Margaret K; Corbridge, Susan

    2002-05-01

    Chronic obstructive pulmonary disease is associated with a functional weakness of the inspiratory muscles. Multiple factors contribute to the decline in functional strength including hyperinflation of the chest, deterioration in nutritional status, and the indirect effects of an exacerbation. The decreased inspiratory muscle strength contributes to sensations of dyspnea and places individuals at risk for respiratory muscle fatigue. The worsening dyspnea causes individuals to reduce their physical activities and ultimately become physically deconditioned. Maximal inspiratory pressure is commonly used to measure functional strength of the inspiratory muscles, and interventions to minimize the extent of decline include inspiratory muscle training, aerobic exercise training, nutritional supplementation, and methods to prevent exacerbations. In the critical care unit, multiple comorbid conditions contribute to further decline in inspiratory muscle strength, making it important to assess respiratory muscle function regularly.

  9. Factors Influencing the Fatigue Strength of Materials

    NASA Technical Reports Server (NTRS)

    Bollenrath, F

    1941-01-01

    A number of factors are considered which influence the static and fatigue strength of materials under practical operating conditions as contrasted with the relations obtaining under conditions of the usual testing procedure. Such factors are interruptions in operation, periodically fluctuating stress limits and mean stresses with periodic succession of several groups and stress states, statistical changes and succession of stress limits and mean stresses, frictional corrosion at junctures, and notch effects.

  10. Effects of muscle fatigue on multi-muscle synergies.

    PubMed

    Singh, Tarkeshwar; Latash, Mark L

    2011-10-01

    We studied the effects of fatigue of ankle dorsiflexors on multi-muscle synergies defined as co-varied adjustments of elemental variables (M-modes) that stabilize a task-related performance variable (trajectory of the center of pressure, COP). M-modes were defined as muscle groups with parallel changes in activation levels. Healthy participants performed voluntary body sway in the anterior-posterior direction while trying to minimize sway in the medio-lateral direction at 0.25, 0.5, and 0.75 Hz. The trials were repeated before and during fatigue induced with a timed voluntary contraction against a constant load. Factor extraction using the principal component method was used to identify four M-modes within the space of integrated indices of muscle activity. Variance in the M-mode space at different phases across sway cycles was partitioned into two components, one that did not affect the average value of COP shift and the other that did. There were no significant effects of fatigue on variability of performance of the explicit task and on the amplitude of the COP shift. Variance of muscle activation indices and M-mode magnitudes increased during fatigue for muscles (and M-modes) both involved and not involved in the fatiguing exercise. Most of the M-mode variance increase was within the sub-space compatible with the unchanged COP trajectory resulting in an increase of the index of the multi-M-mode synergy. We conclude that one of the adaptive mechanisms to fatigue within a redundant multi-muscle system involves an increase in the variance of activation of non-fatigued muscles with a simultaneous increase in co-variation among muscle activations. The findings can be interpreted within the referent configuration hypothesis on the control of whole-body actions.

  11. Analysis of muscle fatigue in helicopter pilots.

    PubMed

    Balasubramanian, Venkatesh; Dutt, Ashwani; Rai, Shobhit

    2011-11-01

    Helicopter pilots espouse ergonomically unfavourable postures and endure vibration which result in low back pain. The objective of this study was to investigate the effects of a helicopter flight on pilots back and shoulder muscles using surface Electromyography (sEMG) analysis. This study also correlates low back pain symptoms from Rehabilitation Bioengineering Group Pain Scale (RBGPS) questionnaire with muscle fatigue rates obtained. RBGPS was administered on 20 Coast Guard helicopter pilots. sEMG was acquired before and after flight from erector spinae and trapezius muscles in 8 of these 20 pilots. Statistical analysis of time and frequency domain parameters indicated significant fatigue in right trapezius muscle due to flying. Muscle fatigue correlated with average duration of flight (r² = 0.913), total service as pilot (r² = 0.825), pain (r² = 0.463) and total flying hours (r² = 0.507). However, muscle fatigue weakly correlated with Body Mass Index (BMI) (r² = 0.000144) and age (r² = 0.033).

  12. Performance Demands in Softball Pitching: A Comprehensive Muscle Fatigue Study.

    PubMed

    Corben, Jeffrey S; Cerrone, Sara A; Soviero, Julie E; Kwiecien, Susan Y; Nicholas, Stephen J; McHugh, Malachy P

    2015-08-01

    Monitoring pitch count is standard practice in minor league baseball but not in softball because of the perception that fast-pitch softball pitching is a less stressful motion. To examine muscle fatigue after fast-pitch softball performances to provide an assessment of performance demand. Descriptive laboratory study. Bilateral strength measurements (handheld dynamometer) were made on 19 female softball pitchers (mean age [±SD], 15.2 ± 1.2 years) before and after pitching a game (mean number of pitches, 99 ± 21; mean innings pitched, 5 ± 1). A total of 20 tests were performed on the dominant and nondominant sides: forearm (grip, wrist flexion/extension, pronation/supination, elbow flexion/extension), shoulder (flexion, abduction/adduction, external/internal rotation, empty can test), scapula (middle/lower trapezius, rhomboid), and hip (hip flexion/extension, abduction/adduction). Fatigue (percentage strength loss) was categorized based on bilateral versus unilateral presentation using paired t tests: bilateral symmetric (significant on dominant and nondominant and not different between sides), bilateral asymmetric (significant on dominant and nondominant but significantly greater on dominant), unilateral asymmetric (significant on dominant only and significantly greater than nondominant), or unilateral equivocal (significant on dominant only but not different from nondominant). Bilateral symmetric fatigue was evident for all hip (dominant, 19.3%; nondominant, 15.2%) and scapular tests (dominant, 19.2%; nondominant, 19.3%). In general, shoulder tests exhibited bilateral asymmetric fatigue (dominant, 16.9%; nondominant, 11.6%). Forearm tests were more variable, with bilateral symmetric fatigue in the elbow flexors (dominant, 22.5%; nondominant, 19.2%), and wrist flexors (dominant, 21.6%; nondominant, 19.0%), bilateral asymmetric fatigue in the supinators (dominant, 21.8%; nondominant, 15.5%), unilateral asymmetric fatigue in the elbow extensors (dominant, 22

  13. High-intensity resistance training in multiple sclerosis - An exploratory study of effects on immune markers in blood and cerebrospinal fluid, and on mood, fatigue, health-related quality of life, muscle strength, walking and cognition.

    PubMed

    Kierkegaard, Marie; Lundberg, Ingrid E; Olsson, Tomas; Johansson, Sverker; Ygberg, Sofia; Opava, Christina; Holmqvist, Lotta Widén; Piehl, Fredrik

    2016-03-15

    High-intensity resistance training is unexplored in people with multiple sclerosis. To evaluate effects of high-intensity resistance training on immune markers and on measures of mood, fatigue, health-related quality of life, muscle strength, walking and cognition. Further, to describe participants' opinion and perceived changes of the training. Twenty patients with relapsing-remitting multiple sclerosis performed high-intensity resistance training at an intensity of 80% of one-repetition maximum, twice a week for 12 weeks. Blood and optional cerebrospinal fluid samples, and data on secondary outcome measures were collected before and after intervention. A study-specific questionnaire was used for capturing participants' opinion. Seventeen participants completed the study. Plasma cytokine levels of tumor necrosis factor were significantly decreased post-intervention (p=0.001). Exploratory cytokine analyses in cerebrospinal fluid (n=8) did not reveal major changes. Significant and clinically important improvements were found in fatigue (p=0.001) and health-related quality of life (p=0.004). Measures of mood (p=0.002), muscle strength (p ≤ 0.001), walking speed (p=0.013) and cognition (p=0.04) were also improved. A majority of participants evaluated the training as very good and perceived changes to the better. High-intensity resistance training in persons with relapsing remitting multiple sclerosis with low disability had positive effects on peripheral pro-inflammatory cytokine levels, led to clinically relevant improvements in measures of fatigue and health-related quality of life, and was well tolerated. These results provide a basis for a larger randomized trial. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Corrosion fatigue of high strength fastener materials in seawater

    NASA Astrophysics Data System (ADS)

    Tipton, D. G.

    1983-12-01

    Environmental effects which significantly reduce the fatigue life of metals are discussed. Corrosion fatigue is a major concern in the engineering application of high strength fasteners in marine environments. The corrosion fatigue failure of an AISI 41L4O high strength steel blade to hub attachment bolt at the MOD-OA 200 kW wind turbine generator was investigated. The reduction of fatigue strength of AISI 41L4O in marine environments and to obtain similar corrosion fatigue data for candidate replacement materials was studied. The AISI 4140, PH 13-8Mo stainless steel, alloy 718 and alloy MP-35N were tested in axial fatigue at a frequency of 20 Hz in dry air and natural seawater. The fatigue data are fitted by regression equations to allow determination of fatigue strength for a given number of cycles to failure.

  15. Corrosion fatigue of high strength fastener materials in seawater

    NASA Technical Reports Server (NTRS)

    Tipton, D. G.

    1983-01-01

    Environmental effects which significantly reduce the fatigue life of metals are discussed. Corrosion fatigue is a major concern in the engineering application of high strength fasteners in marine environments. The corrosion fatigue failure of an AISI 41L4O high strength steel blade to hub attachment bolt at the MOD-OA 200 kW wind turbine generator was investigated. The reduction of fatigue strength of AISI 41L4O in marine environments and to obtain similar corrosion fatigue data for candidate replacement materials was studied. The AISI 4140, PH 13-8Mo stainless steel, alloy 718 and alloy MP-35N were tested in axial fatigue at a frequency of 20 Hz in dry air and natural seawater. The fatigue data are fitted by regression equations to allow determination of fatigue strength for a given number of cycles to failure.

  16. Neck muscle fatigue alters upper limb proprioception.

    PubMed

    Zabihhosseinian, Mahboobeh; Holmes, Michael W R; Murphy, Bernadette

    2015-05-01

    Limb proprioception is an awareness by the central nervous system (CNS) of the location of a limb in three-dimensional space and is essential for movement and postural control. The CNS uses the position of the head and neck when interpreting the position of the upper limb, and altered input from neck muscles may affect the sensory inputs to the CNS and consequently may impair the awareness of upper limb joint position. The purpose of this study was to determine whether fatigue of the cervical extensors muscles (CEM) using a submaximal fatigue protocol alters the ability to recreate a previously presented elbow angle with the head in a neutral position. Twelve healthy individuals participated. CEM activity was examined bilaterally using surface electromyography, and kinematics of the elbow joint was measured. The fatigue protocol included an isometric neck extension task at 70 % of maximum until failure. Joint position error increased following fatigue, demonstrating a significant main effect of time (F 2, 18 = 19.41, p ≤ 0.0001) for absolute error. No significant differences were found for variable error (F 2, 18 = 0.27, p = 0.76) or constant error (F 2, 18 = 1.16 of time, p ≤ 0.33). This study confirms that fatigue of the CEM can reduce the accuracy of elbow joint position matching. This suggests that altered afferent input from the neck subsequent to fatigue may impair upper limb proprioception.

  17. Strengthened Corticosubcortical Functional Connectivity during Muscle Fatigue

    PubMed Central

    Wang, Xiao-Feng; Yue, Guang H.

    2016-01-01

    The present study examined functional connectivity (FC) between functional MRI (fMRI) signals of the primary motor cortex (M1) and each of the three subcortical neural structures, cerebellum (CB), basal ganglia (BG), and thalamus (TL), during muscle fatigue using the quantile regression technique. Understanding activation relation between the subcortical structures and the M1 during prolonged motor performance should help delineate how central motor control network modulates acute perturbations at peripheral sensorimotor system such as muscle fatigue. Ten healthy subjects participated in the study and completed a 20-minute intermittent handgrip motor task at 50% of their maximal voluntary contraction (MVC) level. Quantile regression analyses were carried out to compare the FC between the contralateral (left) M1 and CB, BG, and TL in the minimal (beginning 100 s) versus significant (ending 100 s) fatigue stages. Widespread, statistically significant increases in FC were found in bilateral BG, CB, and TL with the left M1 during significant versus minimal fatigue stages. Our results imply that these subcortical nuclei are critical components in the motor control network and actively involved in modulating voluntary muscle fatigue, possibly, by working together with the M1 to strengthen the descending central command to prolong the motor performance. PMID:27830093

  18. [Effect of respiratory muscle fatigue on their function during exercise].

    PubMed

    Sliwiński, P; Yan, S; Gauthier, A P; Macklem, P T

    1996-01-01

    We evaluated the effect of global inspiratory muscle fatigue (GF) on respiratory muscle control during exercise at 30%, 60%, and 90% of maximal power output in normal subjects. Fatigue was induced by breathing against a high inspiratory resistance until exhaustion. Respiratory pressures, breathing pattern, and perceived breathlessness were measured. Induction of GF had no effect on the ventilatory parameters during mild and moderate exercise. It altered, however, ventilatory response to heavy exercise by increasing breathing frequency and minute ventilation, with minor changes in tidal volume. This was accompanied by an increase in perceived breathlessness. GF significantly increased both the tonic and phasic activities of abdominal muscles that allowed 1) the diaphragm to maintain its function while developing less pressure, 2) the same tidal volume with lesser shortening of the rib cage inspiratory muscles, and 3) relaxation of the abdominal muscles to contribute to lung inflation. The increased work performed by the abdominal muscles may, however, lead to a reduction in their strength. GF may impair exercise performance in some healthy subjects that is probably not related to excessive breathlessness or other ventilatory factors. The respiratory system is remarkably adaptable in maintaining ventilation during exercise even with impaired inspiratory muscle contractility.

  19. Effects of inspiratory muscle training on resistance to fatigue of respiratory muscles during exhaustive exercise.

    PubMed

    Segizbaeva, M O; Timofeev, N N; Donina, Zh A; Kur'yanovich, E N; Aleksandrova, N P

    2015-01-01

    The aim of this study was to assess the effect of inspiratory muscle training (IMT) on resistance to fatigue of the diaphragm (D), parasternal (PS), sternocleidomastoid (SCM) and scalene (SC) muscles in healthy humans during exhaustive exercise. Daily inspiratory muscle strength training was performed for 3 weeks in 10 male subjects (at a pressure threshold load of 60% of maximal inspiratory pressure (MIP) for the first week, 70% of MIP for the second week, and 80% of MIP for the third week). Before and after training, subjects performed an incremental cycle test to exhaustion. Maximal inspiratory pressure and EMG-analysis served as indices of inspiratory muscle fatigue assessment. The before-to-after exercise decreases in MIP and centroid frequency (fc) of the EMG (D, PS, SCM, and SC) power spectrum (P<0.05) were observed in all subjects before the IMT intervention. Such changes were absent after the IMT. The study found that in healthy subjects, IMT results in significant increase in MIP (+18%), a delay of inspiratory muscle fatigue during exhaustive exercise, and a significant improvement in maximal work performance. We conclude that the IMT elicits resistance to the development of inspiratory muscles fatigue during high-intensity exercise.

  20. Muscle force compensation among synergistic muscles after fatigue of a single muscle.

    PubMed

    Stutzig, Norman; Siebert, Tobias

    2015-08-01

    The aim of this study was to examine control strategies among synergistic muscles after fatigue of a single muscle. It was hypothesized that the compensating mechanism is specific for each fatigued muscle. The soleus (SOL), gastrocnemius lateralis (GL) and medialis (GM) were fatigued in separate sessions on different days. In each experiment, subjects (n = 11) performed maximal voluntary contractions prior to and after fatiguing a single muscle (SOL, GL or GM) while the voluntary muscle activity and torque were measured. Additionally, the maximal single twitch torque of the plantarflexors and the maximal spinal reflex activity (H-reflex) of the SOL, GL and GM were determined. Fatigue was evoked using neuromuscular stimulation. Following fatigue the single twitch torque decreased by -20.1%, -19.5%, and -23.0% when the SOL, GL, or GM, have been fatigued. The maximal voluntary torque did not decrease in any session but the synergistic voluntary muscle activity increased significantly. Moreover, we found no alterations in spinal reflex activity. It is concluded that synergistic muscles compensate each other. Furthermore, it seems that self-compensating mechanism of the fatigued muscles occurred additionally. The force compensation does not depend on the function of the fatigued muscle. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Central fatigue affects plantar flexor strength after prolonged running.

    PubMed

    Saldanha, A; Nordlund Ekblom, M M; Thorstensson, A

    2008-06-01

    The primary aim of this study was to examine central fatigue of the plantar flexor muscle group after prolonged running using the twitch interpolation technique. Eight healthy, habitually active male subjects ran on a motorized treadmill for 2 h at a speed corresponding to 75% of peak oxygen uptake (VO(2peak)). Maximal voluntary isometric contraction (MVC) strength as well as the electrically induced twitch produced during MVC [interpolated twitch (IT)] and at rest [resting twitch (RT)] were measured before and after running. The level of activation (LOA) during each MVC was calculated as LOA (%)=100(1-IT/RT). Both MVC and LOA decreased (17+/-16% and 19+/-15%, respectively, P<0.05) after running, whereas RT did not change. The decrease in MVC was correlated with the decrease in LOA (r=0.87, P<0.05). The results demonstrate that after 2 h of treadmill running at an intensity of 75% of VO(2peak), there was a reduction in maximal voluntary plantar flexor muscle strength that was mainly related to central fatigue.

  2. Neuromuscular fatigue during dynamic maximal strength and hypertrophic resistance loadings.

    PubMed

    Walker, Simon; Davis, Lisa; Avela, Janne; Häkkinen, Keijo

    2012-06-01

    The purpose of this study was to compare the acute neuromuscular fatigue during dynamic maximal strength and hypertrophic loadings, known to cause different adaptations underlying strength gain during training. Thirteen healthy, untrained males performed two leg press loadings, one week apart, consisting of 15 sets of 1 repetition maximum (MAX) and 5 sets of 10 repetition maximums (HYP). Concentric load and muscle activity, electromyography (EMG) amplitude and median frequency, was assessed throughout each set. Additionally, maximal bilateral isometric force and muscle activity was assessed pre-, mid-, and up to 30 min post-loading. Concentric load during MAX was decreased after set 10 (P<0.05), while the load was maintained throughout HYP. Both loadings caused large reductions in maximal isometric force (MAX=-30±6.4% vs. HYP=-48±9.7%, P<0.001). The decreased concentric and isometric strength during MAX loading was accompanied by reduced EMG amplitude (P<0.05). Conversely, hypertrophic loading caused decreased median frequency only during isometric contractions (P<0.01). During concentric contractions, EMG amplitude increased and median frequency decreased in HYP (P<0.01). Our results indicate reduced neural drive during MAX loading and more complex changes in muscle activity during HYP loading. Copyright © 2011 Elsevier Ltd. All rights reserved.

  3. Methods for the assessment of peripheral muscle fatigue and its energy and metabolic determinants in COPD.

    PubMed

    Rondelli, Rafaella Rezende; Dal Corso, Simone; Simões, Alexandre; Malaguti, Carla

    2009-11-01

    It has been well established that, in addition to the pulmonary involvement, COPD has systemic consequences that can lead to peripheral muscle dysfunction, with greater muscle fatigue, lower exercise tolerance and lower survival in these patients. In view of the negative repercussions of early muscle fatigue in COPD, the objective of this review was to discuss the principal findings in the literature on the metabolic and bioenergy determinants of muscle fatigue, its functional repercussions, as well as the methods for its identification and quantification. The anatomical and functional substrate of higher muscle fatigue in COPD appears to include lower levels of high-energy phosphates, lower mitochondrial density, early lactacidemia, higher serum ammonia and reduced muscle perfusion. These alterations can be revealed by contraction failure, decreased firing rates of motor units and increased recruitment of motor units in a given activity, which can be functionally detected by a reduction in muscle strength, power and endurance. This review article also shows that various types of muscle contraction regimens and protocols have been used in order to detect muscle fatigue in this population. With this understanding, rehabilitation strategies can be developed in order to improve the resistance to muscle fatigue in this population.

  4. Shoulder muscle load and muscle fatigue among industrial sewing-machine operators.

    PubMed

    Jensen, B R; Schibye, B; Søgaard, K; Simonsen, E B; Sjøgaard, G

    1993-01-01

    Physiological responses to physical work were assessed for 29 female industrial sewing-machine operators during an 8-h working day under ordinary working conditions. During sewing-machine work, the average (left and right) static load in the trapezius muscle was 9% of the maximal electromyogram (EMG) amplitude (% EMGmax), while the average mean load was 15% EMGmax, and the average peak load was 23% EMGmax. The static load level was unrelated to the muscle strength of the sewing-machine operators, which for the group as a whole was within the normal range. The load levels remained unchanged during the working day, while changes in the EMG mean power frequency and zero crossing frequency rate occurred, both indicating the development of muscle fatigue in left and right trapezius muscle during the working day. In line with this, the rating of perceived exertion in the shoulder and neck region increased during the working day. Dividing the group of sewing-machine operators into two groups, those with the highest frequency and those with the lowest frequency of shoulder/neck troubles showed that the former group had significantly lower muscle strength, despite the fact that no differences in the surface EMG during sewing were found between the two groups. It was concluded that industrial sewing-machine work involves a pattern of shoulder muscle activity which induces fatiguing processes in the shoulder and neck regions. Furthermore, since the static shoulder muscle load was independent of muscle strength, factors other than working posture may be of significance for the static shoulder muscle load.

  5. Proximal and distal muscle fatigue differentially affect movement coordination

    PubMed Central

    Cowley, Jeffrey C.

    2017-01-01

    Muscle fatigue can cause people to change their movement patterns and these changes could contribute to acute or overuse injuries. However, these effects depend on which muscles are fatigued. The purpose of this study was to determine the differential effects of proximal and distal upper extremity muscle fatigue on repetitive movements. Fourteen subjects completed a repetitive ratcheting task before and after a fatigue protocol on separate days. The fatigue protocol either fatigued the proximal (shoulder flexor) or distal (finger flexor) muscles. Pre/Post changes in trunk, shoulder, elbow, and wrist kinematics were compared to determine how proximal and distal fatigue affected multi-joint movement patterns and variability. Proximal fatigue caused a significant increase (7°, p < 0.005) in trunk lean and velocity, reduced humeral elevation (11°, p < 0.005), and increased elbow flexion (4°, p < 0.01). In contrast, distal fatigue caused small but significant changes in trunk angles (2°, p < 0.05), increased velocity of wrench movement relative to the hand (17°/s, p < 0.001), and earlier wrist extension (4%, p < 0.005). Movement variability increased at proximal joints but not distal joints after both fatigue protocols (p < 0.05). Varying movements at proximal joints may help people adapt to fatigue at either proximal or distal joints. The identified differences between proximal and distal muscle fatigue adaptations could facilitate risk assessment of occupational tasks. PMID:28235005

  6. Proximal and distal muscle fatigue differentially affect movement coordination.

    PubMed

    Cowley, Jeffrey C; Gates, Deanna H

    2017-01-01

    Muscle fatigue can cause people to change their movement patterns and these changes could contribute to acute or overuse injuries. However, these effects depend on which muscles are fatigued. The purpose of this study was to determine the differential effects of proximal and distal upper extremity muscle fatigue on repetitive movements. Fourteen subjects completed a repetitive ratcheting task before and after a fatigue protocol on separate days. The fatigue protocol either fatigued the proximal (shoulder flexor) or distal (finger flexor) muscles. Pre/Post changes in trunk, shoulder, elbow, and wrist kinematics were compared to determine how proximal and distal fatigue affected multi-joint movement patterns and variability. Proximal fatigue caused a significant increase (7°, p < 0.005) in trunk lean and velocity, reduced humeral elevation (11°, p < 0.005), and increased elbow flexion (4°, p < 0.01). In contrast, distal fatigue caused small but significant changes in trunk angles (2°, p < 0.05), increased velocity of wrench movement relative to the hand (17°/s, p < 0.001), and earlier wrist extension (4%, p < 0.005). Movement variability increased at proximal joints but not distal joints after both fatigue protocols (p < 0.05). Varying movements at proximal joints may help people adapt to fatigue at either proximal or distal joints. The identified differences between proximal and distal muscle fatigue adaptations could facilitate risk assessment of occupational tasks.

  7. Effects of Local and Widespread Muscle Fatigue on Movement Timing

    PubMed Central

    Cowley, Jeffrey C.; Dingwell, Jonathan B.; Gates, Deanna H.

    2014-01-01

    Repetitive movements can cause muscle fatigue, leading to motor reorganization, performance deficits, and/or possible injury. The effects of fatigue may depend on the type of fatigue task employed, however. The purpose of this study was to determine how local fatigue of a specific muscle group versus widespread fatigue of various muscle groups affected the control of movement timing. Twenty healthy subjects performed an upper-extremity low-load work task similar to sawing for 5 continuous minutes both before and after completing a protocol that either fatigued all the muscles used in the task (widespread fatigue) or a protocol that selectively fatigued the primary muscles used to execute the pushing stroke of the sawing task (localized fatigue). Subjects were instructed to time their movements with a metronome. Timing error, movement distance, and speed were calculated for each movement. Data were then analyzed using a goal-equivalent manifold (GEM) approach to quantify changes in goal-relevant and non-goal-relevant variability. We applied detrended fluctuation analysis to each time series to quantify changes in fluctuation dynamics that reflected changes in the control strategies used. After localized fatigue, subjects made shorter, slower movements and exerted greater control over non-goal-relevant variability. After widespread fatigue, subjects exerted less control over non-goal-relevant variability and did not change movement patterns. Thus, localized and widespread muscle fatigue affected movement differently. Local fatigue may reduce the available motor solutions and therefore cause greater movement reorganization than widespread muscle fatigue. Subjects altered their control strategies but continued to achieve the timing goal after both fatigue tasks. PMID:25183157

  8. Pilates: Build Strength in Your Core Muscles

    MedlinePlus

    ... MB, et al. The Pilates Method increases respiratory muscle strength and performance as well as abdominal muscle thickness. ... 20:258. Kloubec JA. Pilates for improvement of muscle endurance, flexibility, balance, and posture. Journal of Strength and Conditioning Research. 2010;24:661. 2008 Physical ...

  9. Relationship among fatigue strength, mean grain size and compressive strength of a rock

    NASA Astrophysics Data System (ADS)

    Singh, S. K.

    1988-10-01

    Fatigue tests carried on three sets of samples having different mean grain sizes revealed that fatigue strength is a function of mean grain size of the rock. Samples having smaller grain size show higher value of fatigue strength. Graywacke samples from Flagstaff formation having mean grain sizes of 1.79 mm, 1.35 mm and 0.93 mm showed fatigue strengths of 87%, 88.25% and 89.1% respectively. Since the mean uniaxial compressive strength also varied with varying grain size, i. e. higher mean strength value for samples having finer grain size; the fatigue strength of a rock also shows a converse relation with mean uniaxial compressive strength.

  10. Effect of adherend steel strength on static and fatigue strength of adhesive/rivet combined joint

    NASA Astrophysics Data System (ADS)

    Imanaka, Makoto; Haraga, Kosuke; Nishikawa, Tetsuya

    1992-02-01

    Adhesive/rivet combined bonding has attracted special interest recently as a joining technique of high-strength steel because of its high joint efficiency. In this study, the effects of steel strength on the tensile and fatigue strength of adhesive/rivet combined and adhesive joints were investigated. In addition, the stress distributions of these joints were analyzed by finite-element methods, taking into consideration the plastic deformation of adherend steels. With the increase of steel strength, the tensile strength of combined and adhesive joints increased and tensile strength was improved by the combination with the rivet. However, irrespective of the steel strength, the fatigue strength of combined and adhesive joints was constant and the fatigue strength of the combined joint was similar to that of the adhesive joint. These findings could be explained from the difference of stress distribution between static and fatigue load conditions.

  11. Limited oxygen diffusion accelerates fatigue development in mouse skeletal muscle

    PubMed Central

    Zhang, Shi-Jin; Bruton, Joseph D; Katz, Abram; Westerblad, Håkan

    2006-01-01

    Isolated whole skeletal muscles fatigue more rapidly than isolated single muscle fibres. We have now employed this difference to study mechanisms of skeletal muscle fatigue. Isolated whole soleus and extensor digitorum longus (EDL) muscles were fatigued by repeated tetanic stimulation while measuring force production. Neither application of 10 mm lactic acid nor increasing the [K+] of the bath solution from 5 to 10 mm had any significant effect on the rate of force decline during fatigue induced by repeated brief tetani. Soleus muscles fatigued slightly faster during continuous tetanic stimulation in 10 mm[K+]. Inhibition of mitochondrial respiration with cyanide resulted in a faster fatigue development in both soleus and EDL muscles. Single soleus muscle fibres were fatigued by repeated tetani while measuring force and myoplasmic free [Ca2+] ([Ca2+]i). Under control conditions, the single fibres were substantially more fatigue resistant than the whole soleus muscles; tetanic force at the end of a series of 100 tetani was reduced by about 10% and 50%, respectively. However, in the presence of cyanide, fatigue developed at a similar rate in whole muscles and single fibres, and tetanic force at the end of fatiguing stimulation was reduced by ∼80%. The force decrease in the presence of cyanide was associated with a ∼50% decrease in tetanic [Ca2+]i, compared with an increase of ∼20% without cyanide. In conclusion, lactic acid or [K+] has little impact on fatigue induced by repeated tetani, whereas hypoxia speeds up fatigue development and this is mainly due to an impaired Ca2+ release from the sarcoplasmic reticulum. PMID:16455685

  12. The fatigue strength of riveted joints and lugs

    NASA Technical Reports Server (NTRS)

    Schijve, J

    1956-01-01

    This report deals with a number of tests on riveted joints and lugs for the primary purpose of comparing the several types of riveted joints and to study the effect of various factors on the fatigue strength of lugs. A check was made to ascertain whether or not an estimate of the fatigue life at a certain loading could be made from the dimensions of the joint and the fatigue data of the unnotched materials. Recommendations are made on the proportioning of joints to obtain better fatigue behavior.

  13. The effect of random modulation of functional electrical stimulation parameters on muscle fatigue.

    PubMed

    Graham, Geoffrey M; Thrasher, T Adam; Popovic, Milos R

    2006-03-01

    Muscle contractions induced by functional electrical stimulation (FES) tend to result in rapid muscle fatigue, which greatly limits activities such as FES-assisted standing and walking. It was hypothesized that muscle fatigue caused by FES could be reduced by randomly modulating parameters of the electrical stimulus. Seven paraplegic subjects participated in this study. While subjects were seated, FES was applied to quadriceps and tibialis anterior muscles bilaterally using surface electrodes. The isometric force was measured, and the time for the force to drop by 3 dB (fatigue time) and the normalized force-time integral (FTI) were determined. Four different modes of FES were applied in random order: constant stimulation, randomized frequency (mean 40 Hz), randomized current amplitude, and randomized pulsewidth (mean 250 micros). In randomized trials, stimulation parameters were stochastically modulated every 100 ms in a range of +/-15% using a uniform probability distribution. There was no significant difference between the fatigue time measurements for the four modes of stimulation. There was also no significant difference in the FTI measurements. Therefore, our particular method of stochastic modulation of the stimulation parameters, which involved moderate (15%) variations updated every 100 ms and centered around 40 Hz, appeared to have no effect on muscle fatigue. There was a strong correlation between maximum force measurements and stimulation order, which was not apparent in the fatigue time or FTI measurements. It was concluded that a 10-min rest period between stimulation trials was insufficient to allow full recovery of muscle strength.

  14. Inspiratory muscles experience fatigue faster than the calf muscles during treadmill marching.

    PubMed

    Perlovitch, Renana; Gefen, Amit; Elad, David; Ratnovsky, Anat; Kramer, Mordechai R; Halpern, Pinchas

    2007-04-16

    The possibility that respiratory muscles may fatigue during extreme physical activity and thereby become a limiting factor leading to exhaustion is debated in the literature. The aim of this study was to determine whether treadmill marching exercise induces respiratory muscle fatigue, and to compare the extent and rate of respiratory muscle fatigue to those of the calf musculature. To identify muscle fatigue, surface electromyographic (EMG) signals of the inspiratory (sternomastoid, external intercostals), expiratory (rectus abdominis and external oblique) and calf (gastrocnemius lateralis) muscles were measured during a treadmill march of 2 km at a constant velocity of 8 km/h. The extent of fatigue was assessed by determining the increase in root-mean-square (RMS) of EMG over time, and the rate of fatigue was assessed from the slope of the EMG RMS versus time curve. Results indicated that (i) the inspiratory and calf muscles are the ones experiencing the most dominant fatigue during treadmill marching, (ii) the rate of fatigue of each muscle group was monotonic between the initial and terminal phases of exercise, and (iii) the inspiratory muscles fatigue significantly faster than the calf at the terminal phase of exercise, and are likely to fatigue faster during the initial exercise as well. Accordingly, this study supports the hypothesis that fatigue of the inspiratory muscles may be a limiting factor during exercise.

  15. Asymmetry of Muscle Strength in Elite Athletes

    ERIC Educational Resources Information Center

    Drid, Patrik; Drapsin, Miodrag; Trivic, Tatjana; Lukac, Damir; Obadov, Slavko; Milosevic, Zoran

    2009-01-01

    "Study aim": To determine muscle strength variables in elite judoists and wrestlers since thigh muscle strength and bilaterally balanced flexor-to-extensor ratio minimise injury risk and are desirable for achieving sport successes. "Material and methods": Judoists, wrestlers and untrained subjects, 10 each, were subjected to isokinetic strength…

  16. Quadriceps muscle strength in scoliosis.

    PubMed

    Swallow, E B; Barreiro, E; Gosker, H; Sathyapala, S A; Sanchez, F; Hopkinson, N S; Moxham, J; Schols, A; Gea, J; Polkey, M I

    2009-12-01

    Quadriceps muscle weakness is an important component of chronic obstructive pulmonary disease (COPD). We hypothesised that quadriceps weakness would also be a feature of restrictive lung disease due to scoliosis. We studied 10 patients with severe scoliosis (median (interquartile range (IQR)) forced expiratory volume in 1 s (FEV(1))() 35.3 (11)% predicted), 10 patients with severe COPD (FEV(1) 26.5 (9.0)% pred) and 10 healthy age-matched adults. We measured quadriceps strength, exercise capacity and analysed quadriceps muscle biopsies for myosin heavy-chain (MyHC) isoform expression and the presence of oxidative stress. Both groups exhibited quadriceps weakness with median (IQR) maximal voluntary contraction force being 46.0 (17.0) kg, 21.5 (21.0) kg and 31.5 (11.0) kg, respectively (p = 0.02 and 0.04, respectively, for each patient group against controls). Oxidative stress was significantly greater in the quadriceps of both restrictive and COPD patients. The scoliosis patients exhibited a decrease in the proportion of MyHC type I compared with controls; median (IQR) 35.3 (18.5)% compared with 47.7 (9.3)%, p = 0.028. The scoliosis patients also showed an increase in MyHC IIx (26.3 (15.5)% compared with 11.3 (13.0)%, p = 0.01. Quadriceps weakness is a feature of severe scoliosis; the similarities between patients with scoliosis and patients with COPD suggest a common aetiology to quadriceps weakness in both conditions.

  17. a Dynamical Model of Muscle Activation, Fatigue and Recovery

    NASA Astrophysics Data System (ADS)

    Liu, Jing Z.; Yue, Guang H.; Brown, Robert W.

    2001-04-01

    A dynamical model on muscle activation, fatigue, and recovery was developed to provide a theoretical framework for explaining the force produced by muscle(s) during the process of getting activated and fatigued. By simplifying the fatigue effect and the recovery effect as two phenomenological parameters (F, R), we developed a set of dynamical equations to describe the behavior of muscle(s) as a group of motor units under an external drive, e.g., voluntary brain effort. This model provides a macroscopic view for understanding the biophysical mechanisms of voluntary drive, fatigue effect, and recovery in stimulating, limiting and modulating the force output from muscle(s). Agreement between the experimental data and the predicted forces is excellent. This model may also generate new possibilities in clinical and engineering applications. The parameters introduced by this model can serve as good indicators of physical conditions, and may be useful for quantitative diagnosis of certain diseases related to muscles, especially symptoms of fatigue. Inference from the model can clarify a long-debating question regarding the maximal possibility of muscle force production. It can also be used as guideline for simulating real muscle in muscle engineering or design of human-mimic robot.

  18. The L-Z complexity of exercise-induced muscle fatigue based on acoustic myographye

    NASA Astrophysics Data System (ADS)

    Yijian, Min; Xinyuan, Liu; Tingting, Wang

    2014-01-01

    The mechanism of exercise fatigue was investigated during exercise using L-Z complexity of non-linear analysis. Muscle fatigue was induced in the sitting position by lifting the heel under a load. An acoustic myogram of the gastrocnemius was obtained until exhaustion. The different modes of the speed responses were calculated using the L-Z complexity method, which analyzes muscle fibers participation, while the exercise is in progress. The L-Z complexity decreased incrementally with decreases in muscle strength, reaching a minimum value when the muscle was exhausted. Our data indicate that the L-Z complexity method is easy to use and effective at revealing the dynamic characteristics and variations of exercise fatigue. This method could be used to monitor sports training.

  19. Muscle fatigue based evaluation of bicycle design.

    PubMed

    Balasubramanian, V; Jagannath, M; Adalarasu, K

    2014-03-01

    Bicycling posture leads to considerable discomfort and a variety of chronic injuries. This necessitates a proper bicycle design to avoid injuries and thereby enhance rider comfort. The objective of this study was to investigate the muscle activity during cycling on three different bicycle designs, i.e., rigid frame (RF), suspension (SU) and sports (SP) using surface electromyography (sEMG). Twelve male volunteers participated in this study. sEMG signals were acquired bilaterally from extensor carpi radialis (ECR), trapezius medial (TM), latissimus dorsi medial (LDM) and erector spinae (ES), during 30 min of cycling on each bicycle and after cycling. Time domain (RMS) and frequency domain (MPF) parameters were extracted from acquired sEMG signals. From the sEMG study, it was found that the fatigue in right LDM and ES were significantly (p < 0.05) higher in SP bicycle. This was corroborated by a psychophysical assessment based on RBG pain scale. The study also showed that there was a significantly lesser fatigue with the SU bicycle than the RF and SP bicycles.

  20. Muscle training for bone strength.

    PubMed

    Suominen, Harri

    2006-04-01

    The main function of bone is to provide the mechanical integrity for locomotion and protection; accordingly, bone mass and architecture are adjusted to control the strains produced by mechanical load and muscular activity. Age-related patterns involve peak bone mass during growth, a plateau in adulthood, and bone loss during aging. The decline in bone mass and structural integrity results in increased risk of fractures, particularly in post-menopausal women. Athletes competing in strength and power events, such as weight-lifting and jumping, have superior bone mass and structure compared with their untrained counterparts in all age groups. Exercise seems to be most effective during rapid growth, the average gain in bone mineral content (BMC) and density (BMD) in controlled trials being of the order of 2-5% per year. The net gain of BMD after exercise interventions among older people is modest, at a level of 1-3% per year, but it is not clear whether positive effects can be maintained over a longer time. Although aerobic exercise is important in maintaining overall health, the resistance type of muscle training may be more applicable to the basic rules of bone adaptation and site-specific effects of exercise, have more favorable effects in maintaining or improving bone mass and architecture, and be safe and feasible for older people. It has been suggested that there is an opportunity for resistance training, for improved effects on BMD in postmenopausal women in bones which have less daily loading. In addition to BMC and BMD, bone geometry and mass distribution may also change as a result of training and other treatment, such as hormonal replacement therapy, thereby further improving bone strength and reducing fracture risk. Appropriate training regimens may reduce the risk of falls and the severity of fall-related injuries, and also constitute potential therapy to improve functional ability and the quality of life in osteoporotic patients. However, further research

  1. Notch Fatigue Strength of a PM Disk Superalloy

    NASA Technical Reports Server (NTRS)

    Gayda, John; Gabb, Timothy P.; Telesman, Jack

    2007-01-01

    New powder metallurgy (PM) disk superalloys, such as ME3, LSHR, and Alloy 10, have been developed in recent years which enable rim temperatures in turbine disk applications to approach 1300 F. Before these alloys can be utilized at 1300 F their long term durability must be ensured. One of the key requirements for disk rims is notch fatigue strength. This issue is extremely important and is a direct result of the blade attachment geometry employed at the disk rim. Further, the imposition of a dwell at maximum load, associated with take off and landing, can also affect notch fatigue strength. For these reasons a study has been undertaken to assess the notch dwell fatigue strength of a modern PM disk alloy through spin pit evaluation of a prototypical disk. The first element of this program involves screening potential heat treatments with respect to notch fatigue strength at 1300 F utilizing a conventional notch fatigue specimen with a stress concentration factor (K(sub t)) of 2 and a 90 sec dwell at peak load. The results of this effort are reported in this paper including the downselect of an optimal heat treatment, from a notch fatigue standpoint.

  2. Fatigue related changes in electromyographic coherence between synergistic hand muscles.

    PubMed

    Kattla, Shashikala; Lowery, Madeleine M

    2010-04-01

    The aim of this study was to examine coherence between surface electromyographic (EMG) signals from two index finger flexor muscles, the first dorsal interosseous (FDI) and flexor digitorum superficialis (FDS), during and immediately following sustained, fatiguing isometric contraction. Coherence was observed between the FDI and FDS EMG signals in the tremor (8-12 Hz), beta (15-35 Hz) and gamma (35-60 Hz) bands in all subjects. A significant increase in EMG-EMG coherence in the beta and gamma frequency bands was observed immediately following the fatiguing contraction. No significant difference was observed in the tremor band coherence before and after fatigue. Coherence was observed between EMG and force in the tremor band during both the pre- and post-fatigue contractions and a significant increase in the FDI EMG-force coherence post-fatigue was observed. It is suggested that the increase in beta and gamma band coherence with fatigue may be due to increased levels of corticomotoneuronal drive to both muscles. Alternatively, the increased EMG-EMG coherence may reflect an increased contribution of peripheral afferents to coupling across the muscle with fatigue. Although the functional significance is not clear, the increase in coherence may help to overcome reduced motoneuron excitability with fatigue, to bind together different sensorimotor elements or to coordinate force generation across muscles in a more synergistic manner as the force generating capacity of the muscle is decreased.

  3. Fatigue strength of woven kenaf fiber reinforced composites

    NASA Astrophysics Data System (ADS)

    Ismail, A. E.; Aziz, M. A. Che Abdul

    2015-12-01

    Nowadays, green composites provide alternative to synthetic fibers for non-bearing and load-bearing applications. According to literature review, lack of information is available on the fatigue performances especially when the woven fiber is used instead of randomly oriented fibers. In order to overcome this problem, this paper investigates the fatigue strength of different fiber orientations and number of layers of woven kenaf fiber reinforced composites. Four types of fiber orientations are used namely 0°, 15°, 30° and 45°. Additionally, two numbers of layers are also considered. It is revealed that the fatigue life has no strong relationship with the fiber orientations. For identical fiber orientations, the fatigue life can be predicted considerably using the normalized stress. However as expected, the fatigue life enhancement occur when the number of layer is increased.

  4. Dynamic fatigue and strength characterization of three ceramic materials.

    PubMed

    Teixeira, Erica C; Piascik, Jeffrey R; Stoner, Brian R; Thompson, Jeffrey Y

    2007-06-01

    Fracture strength and fatigue parameters of three ceramic materials submitted to dynamic fatigue were evaluated. A machinable leucite-reinforced dental ceramic, aluminum oxide, and yttria-stabilized zirconia (YSZ) were tested. The inert strength of the materials was determined in air (25 degrees C) at stressing rates of 70, 250, 400 MPa/s for Porcelain, Alumina and YSZ respectively. The data was analyzed using a two-parameter Weibull distribution. The Weibull modulus (m) and the characteristic of fracture (sigma0) parameters were determined for each material. Specimens were also tested in 3-point bending at different stressing rates in distilled/deionized water at 37 degrees C (dynamic fatigue) in order to calculate the fatigue parameters n and ln B. The strength for each material was characterized using Strength-Probability-Time (SPT) diagrams for 1 day, 1 year and 10 years. YSZ showed a high-fracture strength sigma0 (1,459 MPa) at a failure probability of 63.2% and high resistance to subcritical crack growth. YSZ and alumina showed better resistance to slow crack growth than porcelain, indicating less susceptibility to strength degradation by stress corrosion. Lifetime predictions after 10 years indicate a reduction of 50%, 36% and 29% in strength for porcelain, alumina and YSZ respectively. YSZ seems to be a very promising material for long-term dental and biomedical applications.

  5. EFFECTS OF AGE AND ACUTE MUSCLE FATIGUE ON REACTIVE POSTURAL CONTROL IN HEALTHY ADULTS

    PubMed Central

    Papa, Evan V.; Foreman, K. Bo; Dibble, Lee E.

    2015-01-01

    BACKGROUND Falls can cause moderate to severe injuries such as hip fractures and head trauma in older adults. While declines in muscle strength and sensory function contribute to increased falls in older adults, skeletal muscle fatigue is often overlooked as an additional contributor to fall risk. The purpose of this investigation was to examine the effects of acute lower extremity muscle fatigue and age on reactive postural control in healthy adults. METHODS A sample of 16 individuals participated in this study (8 healthy older adults and 8 healthy young persons). Whole body kinematic and kinetic data were collected during anterior and posterior reproducible fall tests before (T0) and immediately after (T1) eccentric muscle fatiguing exercise, as well as after 15-minutes (T15) and 30-minutes (T30) of rest. FINDINGS Lower extremity joint kinematics of the stepping limb during the support (landing) phase of the anterior fall were significantly altered by the presence of acute muscle fatigue. Step velocity was significantly decreased during the anterior falls. Statistically significant main effects of age were found for step length in both fall directions. Effect sizes for all outcomes were small. No statistically significant interaction effects were found. INTERPRETATION Muscle fatigue has a measurable effect on lower extremity joint kinematics during simulated falls. These alterations appear to resolve within 15 minutes of recovery. The above deficits, coupled with a reduced step length, may help explain the increased fall risk in older adults. PMID:26351001

  6. Effects of age and acute muscle fatigue on reactive postural control in healthy adults.

    PubMed

    Papa, Evan V; Foreman, K Bo; Dibble, Leland E

    2015-12-01

    Falls can cause moderate to severe injuries such as hip fractures and head trauma in older adults. While declines in muscle strength and sensory function contribute to increased falls in older adults, skeletal muscle fatigue is often overlooked as an additional contributor to fall risk. The purpose of this investigation was to examine the effects of acute lower extremity muscle fatigue and age on reactive postural control in healthy adults. A sample of 16 individuals participated in this study (8 healthy older adults and 8 healthy young persons). Whole body kinematic and kinetic data were collected during anterior and posterior reproducible fall tests before (T0) and immediately after (T1) eccentric muscle fatiguing exercise, as well as after 15-min (T15) and 30-min (T30) of rest. Lower extremity joint kinematics of the stepping limb during the support (landing) phase of the anterior fall were significantly altered by the presence of acute muscle fatigue. Step velocity was significantly decreased during the anterior falls. Statistically significant main effects of age were found for step length in both fall directions. Effect sizes for all outcomes were small. No statistically significant interaction effects were found. Muscle fatigue has a measurable effect on lower extremity joint kinematics during simulated falls. These alterations appear to resolve within 15 min of recovery. The above deficits, coupled with a reduced step length, may help explain the increased fall risk in older adults. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Factors that affect the fatigue strength of power transmission shafting

    NASA Technical Reports Server (NTRS)

    Loewenthal, S. H.

    1984-01-01

    A long standing objective in the design of power transmission shafting is to eliminate excess shaft material without compromising operational reliability. A shaft design method is presented which accounts for variable amplitude loading histories and their influence on limited life designs. The effects of combined bending and torsional loading are considered along with a number of application factors known to influence the fatigue strength of shafting materials. Among the factors examined are surface condition, size, stress concentration, residual stress and corrosion fatigue.

  8. Treadmill walking in water induces greater respiratory muscle fatigue than treadmill walking on land in healthy young men.

    PubMed

    Yamashina, Yoshihiro; Yokoyama, Hisayo; Naghavi, Nooshin; Hirasawa, Yoshikazu; Takeda, Ryosuke; Ota, Akemi; Imai, Daiki; Miyagawa, Toshiaki; Okazaki, Kazunobu

    2016-05-01

    The purpose of the present study was to investigate the effect of walking in water on respiratory muscle fatigue compared with that of walking on land at the same exercise intensity. Ten healthy males participated in 40-min treadmill walking trials on land and in water at an intensity of 60% of peak oxygen consumption. Respiratory function and respiratory muscle strength were evaluated before and after walking trials. Inspiratory muscle strength and forced expiratory volume in 1 s were significantly decreased immediately after walking in water, and expiratory muscle strength was significantly decreased immediately and 5 min after walking in water compared with the baseline. The decreases of inspiratory and expiratory muscle strength were significantly greater compared with that after walking on land. In conclusion, greater inspiratory and expiratory muscle fatigue was induced by walking in water than by walking on land at the same exercise intensity in healthy young men.

  9. Fatigue strengths of particulate filler composites reinforced with fibers.

    PubMed

    Bae, Ji-Myung; Kim, Kyoung-Nam; Hattori, Masayuki; Hasegawa, Koji; Yoshinari, Masao; Kawada, Eiji; Oda, Yutaka

    2004-06-01

    The aim of this study was to evaluate the dynamic fatigue strengths at 10(5) cycles and the strains of particulate filler composite resins with and without reinforcing fibers. An UHMWPE (Ribbond), a polyaromatic polyamide fiber (Fibreflex), and three glass fibers (GlasSpan, FibreKor, Vectris Frame) were used to reinforce the particulate filler composite resins. The fatigue properties were measured in three-point bending mode using a servohydraulic universal testing machine at a frequency of 5 Hz, until failure occurred or 10(5) cycles had been completed. The fatigue strengths at 10(5) cycles were determined by the staircase method. The fractured aspects of specimens were evaluated by an optical and scanning electron microscope. The fatigue strengths of particulate filler composite resins were 49-57 MPa, and those of fiber-reinforced were 90-209 MPa. Unidirectional glass fibers showed higher reinforcing effects on the fatigue strengths of composite resins. The strain of UHMWPE-reinforced composite was largest.

  10. Fatigue strength of tubular structural elements at bending vibrations. Communication 2: TSE fatigue strength at programmed load variation

    NASA Astrophysics Data System (ADS)

    Gerasimchuk, O. N.; Gorodetskij, S. S.; Gryaznov, B. A.; Nalimov, Yu. S.

    1994-04-01

    Programs of a block loading with a prescribed and random alternation of stress amplitudes, simulating service load spectra, are presented. The results of fatigue testing of straight and bent tubular structural elements are given. A conclusion is drawn that low fatigue strength of VNS25 steel bent TSEs is due to an unfavorable technological inheritance of the tube bending and deplanation of the section during the test.

  11. The effect of massage on localized lumbar muscle fatigue

    PubMed Central

    Tanaka, Tim Hideaki; Leisman, Gerry; Mori, Hidetoshi; Nishijo, Kazushi

    2002-01-01

    Background There is not enough evidence to support the efficacy of massage for muscle fatigue despite wide utilization of the modality in various clinical settings. This study investigated the influence of massage application on localized back muscle fatigue. Methods Twenty-nine healthy subjects participated in two experimental sessions (massage and rest conditions). On each test day, subjects were asked to lie in the prone position on a treatment table and perform sustained back extension for 90 seconds. Subjects then either received massage on the lumbar region or rested for a 5 minute duration, then repeated the back extension movement. The median frequency (MDF), mean power frequency (MNF), and root mean square (RMS) amplitude of electromyographic signals during the 90 second sustained lumbar muscle contraction were analyzed. The subjective feeling of fatigue was then evaluated using the Visual Analogue Scale (VAS). Results MDF and MNF significantly declined with time under all conditions. There was no significant difference in MDF, MNF or RMS value change between before and after massage, or between rest and massage conditions. There was a significant increase in fatigue VAS at the end of the 2nd back extension with rest condition. There was a significant difference in fatigue VAS change between massage and rest condition. Conclusions A significant difference was observed between massage and rest condition on VAS for muscle fatigue. On EMG analysis, there were no significant differences to conclude that massage stimulation influenced the myoelectrical muscle fatigue, which is associated with metabolic and electrical changes. PMID:12377105

  12. Gum chewing and jaw muscle fatigue and pains.

    PubMed

    Christensen, L V; Tran, K T; Mohamed, S E

    1996-06-01

    To study possible associations between gum chewing and fatigue and pains in the jaw muscles, eight healthy adults performed prolonged idling, prolonged unilateral chewing of gum, and brief vigorous clenching of the teeth (MVC). Through surface electromyography (EMG), the authors monitored the cumulative (microV.s) as well as the average rates (microV.s-1) of contractile activities in the right and left masseter muscles. During 10 min of idling there was an absence of muscle fatigue and muscle pains when the EMG rates of the right and left masseter muscles were 2% and 3%, respectively, of those required to elicit isometric muscle pains through MVC. During 10 min of right-sided gum chewing at a rate of 1.2 Hz, the majority of subjects (75%) experienced weak jaw muscle fatigue-not jaw muscle pains-when the EMG rates of the right and left masseter muscles were 38% and 19%, respectively, of those required to elicit isometric pains through MVC. In comparison with 10 min of idling, the weak muscle fatigue of 10 min of unilateral gum chewing appeared when the total contractile activities of the right and left masseter muscles were increased by 1664% and 519%, respectively. It seemed as if prolonged unilateral gum chewing and previous pain-releasing MVC caused some sensitization of muscle nociceptors which, in turn, aggravated subsequent isometric jaw muscle pains elicited through MVC. Even though the right masseter muscle was the most frequent site of clinical fatigue and pains, the authors found no evidence supporting the theoretical foundation of the myofascial pain/dysfunction syndrome.

  13. Notch sensitivity jeopardizes titanium locking plate fatigue strength.

    PubMed

    Tseng, Wo-Jan; Chao, Ching-Kong; Wang, Chun-Chin; Lin, Jinn

    2016-12-01

    Notch sensitivity may compromise titanium-alloy plate fatigue strength. However, no studies providing head-to-head comparisons of stainless-steel or titanium-alloy locking plates exist. Custom-designed identically structured locking plates were made from stainless steel (F138 and F1314) or titanium alloy. Three screw-hole designs were compared: threaded screw-holes with angle edges (type I); threaded screw-holes with chamfered edges (type II); and non-threaded screw-holes with chamfered edges (type III). The plates' bending stiffness, bending strength, and fatigue life, were investigated. The stress concentration at the screw threads was assessed using finite element analyses (FEA). The titanium plates had higher bending strength than the F1314 and F138 plates (2.95:1.56:1) in static loading tests. For all metals, the type-III plate fatigue life was highest, followed by type-II and type-I. The type-III titanium plates had longer fatigue lives than their F138 counterparts, but the type-I and type-II titanium plates had significantly shorter fatigue lives. All F1314 plate types had longer fatigue lives than the type-III titanium plates. The FEA showed minimal stress difference (0.4%) between types II and III, but the stress for types II and III was lower (11.9% and 12.4%) than that for type I. The screw threads did not cause stress concentration in the locking plates in FEA, but may have jeopardized the fatigue strength, especially in the notch-sensitive titanium plates. Improvement to the locking plate design is necessary. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Influence of gender on muscle fatigue during dynamic knee contractions

    PubMed Central

    FUJISAWA, Chiharu; TAMAKI, Akira; YAMADA, Eiji; MATSUOKA, Hirofumi

    2017-01-01

    Purpose: The purpose was to compare quadriceps muscle fatigue and change in surface electromyogram (sEMG) spectral power, muscle thickness, and peak torque (normalized by body weight) in men and women during isokinetic knee contractions. Methods: Nineteen healthy volunteers (10 men, 9 women) participated. The volunteers performed 32 consecutive maximal isokinetic knee contractions for peak torque and muscle fatigue index (FI). The sEMG data were analyzed using wavelet analysis for median frequency (MF). Muscle thickness was measured using ultrasonography. Results: Men had a significantly higher FI, peak torque (Nm/kg), muscle thickness than women (p<0.05). A significant linear decreased MF slope in the vastus lateralis was observed (p<0.05) in men than in women. There was no significant difference in MF slope in the vastus medialis between men and women. Conclusion: During muscle fatigue assessment, men had a significantly greater muscle thickness, knee extension peak torque, and a higher decrease of MF slope than women. Our results indicate that specific muscle fatigue observed during repeated muscle knee contractions is significantly influence by gender and affects MF slope, knee extension peak torque, and muscle thickness. PMID:28781931

  15. Muscle injections with lidocaine improve resting fatigue and pain in patients with chronic fatigue syndrome

    PubMed Central

    Staud, Roland; Kizer, Taylor; Robinson, Michael E

    2017-01-01

    Objective Patients with chronic fatigue syndrome (CFS) complain of long-lasting fatigue and pain which are not relieved by rest and worsened by physical exertion. Previous research has implicated metaboreceptors of muscles to play an important role for chronic fatigue and pain. Therefore, we hypothesized that blocking impulse input from deep tissues with intramuscular lidocaine injections would improve not only the pain but also fatigue of CFS patients. Methods In a double-blind, placebo-controlled study, 58 CFS patients received 20 mL of 1% lidocaine (200 mg) or normal saline once into both trapezius and gluteal muscles. Study outcomes included clinical fatigue and pain, depression, and anxiety. In addition, mechanical and heat hyperalgesia were assessed and serum levels of lidocaine were obtained after the injections. Results Fatigue ratings of CFS patients decreased significantly more after lidocaine compared to saline injections (p = 0.03). In contrast, muscle injections reduced pain, depression, and anxiety (p < 0.001), but these changes were not statistically different between lidocaine and saline (p > 0.05). Lidocaine injections increased mechanical pain thresholds of CFS patients (p = 0.04) but did not affect their heat hyperalgesia. Importantly, mood changes or lidocaine serum levels did not significantly predict fatigue reductions. Conclusion These results demonstrate that lidocaine injections reduce clinical fatigue of CFS patients significantly more than placebo, suggesting an important role of peripheral tissues for chronic fatigue. Future investigations will be necessary to evaluate the clinical benefits of such interventions. PMID:28721090

  16. Effect of Preloading on Fatigue Strength in Dynamic Fatigue Testing of Ceramic Materials at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Salem, Jonathan A.

    1995-01-01

    Previously derived solutions of fatigue strength as a function of preloading were verified by applying preloads to elevated temperature dynamic fatigue tests of 96 wt% alumina at 1000 C and NC 132 silicon nitride at 1100 C. The technique was found very useful in identification and control of the governing failure mechanism when multiple failure mechanisms, such as slow crack growth, creep and oxidation occurred simultaneously at elevated temperatures.

  17. Fatigue strength of a single lap joint SPR-bonded

    NASA Astrophysics Data System (ADS)

    Di Franco, G.; Fratini, L.; Pasta, A.

    2011-05-01

    In the last years, hybrid joints, meaning with this the joints which consist in combining a traditional mechanical joint to a layer of adhesive, are gradually attracting the attention of various sectors of the construction of vehicles and transportation industries, for their better performance compared to just mechanical joints (self-piercing riveting SPR, riveting, and so on) or just to bonded joints. The paper investigates the fatigue behavior of a single lap joint self-piercing riveted (SPR) and bonded throughout fatigue tests. The considered geometric configuration allowed the use of two rivets placed longitudinally; an epoxy resin was used as adhesive. In the first part of the work static characterization of the joints was carried out through tensile tests. Then fatigue tests were made with the application of different levels of load. The fatigue curves were also obtained at the varying the distance between the two rivets in order to better assess the joint strength for a given length of overlap.

  18. Surface EMG and muscle fatigue: multi-channel approaches to the study of myoelectric manifestations of muscle fatigue.

    PubMed

    Marco, Gazzoni; Alberto, Botter; Taian, Vieira

    2017-05-01

    In a broad view, fatigue is used to indicate a degree of weariness. On a muscular level, fatigue posits the reduced capacity of muscle fibres to produce force, even in the presence of motor neuron excitation via either spinal mechanisms or electric pulses applied externally. Prior to decreased force, when sustaining physically demanding tasks, alterations in the muscle electrical properties take place. These alterations, termed myoelectric manifestation of fatigue, can be assessed non-invasively with a pair of surface electrodes positioned appropriately on the target muscle; traditional approach. A relatively more recent approach consists of the use of multiple electrodes. This multi-channel approach provides access to a set of physiologically relevant variables on the global muscle level or on the level of single motor units, opening new fronts for the study of muscle fatigue; it allows for: (i) a more precise quantification of the propagation velocity, a physiological variable of marked interest to the study of fatigue; (ii) the assessment of regional, myoelectric manifestations of fatigue; (iii) the analysis of single motor units, with the possibility to obtain information about motor unit control and fibre membrane changes. This review provides a methodological account on the multi-channel approach for the study of myoelectric manifestation of fatigue and on the experimental conditions to which it applies, as well as examples of their current applications.

  19. Fatigue strength testing of LTCC and alumina ceramics bonds

    NASA Astrophysics Data System (ADS)

    Dąbrowski, A.; Matkowski, P.; Golonka, L.

    2012-12-01

    In this paper the results of fatigue strength tests of ceramic joints are presented. These tests have been performed on the samples subjected to thermal and vibration fatigue as well as on the reference samples without any additional loads. The main goal of the investigation was to determine the strength of hybrid ceramics joints using tensile testing machine. The experiment enabled evaluation of fatigue effects in the mentioned joints. Geometry of test samples has been designed according to FEM simulations, performed in ANSYS FEM environment. Thermal stress as well as the stress induced by vibrations have been analyzed in the designed model. In the experiments two types of ceramics have been used — LTCC green tape DP951 (DuPont) and alumina ceramic tape. The samples have been prepared by joining two sintered ceramic beams made of different types of material. The bonds have been realized utilizing low temperature glass or a layer of LTCC green tape.

  20. Long-Term Muscle Fatigue After Standing Work.

    PubMed

    Garcia, Maria-Gabriela; Läubli, Thomas; Martin, Bernard J

    2015-11-01

    The aims of this study were to determine long-term fatigue effects in the lower limbs associated with standing work and to estimate possible age and gender influences. The progressive accumulation of muscle fatigue effects is assumed to lead to musculoskeletal disorders, as fatigue generated by sustained low-level exertions exhibits long-lasting effects. However, these effects have received little attention in the lower limbs. Fourteen men and 12 women from two different age groups simulated standing work for 5 hr including 5-min seated rest breaks and a 30-min lunch. The younger group was also tested in a control day. Muscle fatigue was quantified by electrically induced muscle twitches (muscle twitch force [MTF]), postural stability, and subjective evaluation of discomfort. MTF showed a significant fatigue effect after standing work that persisted beyond 30 min after the end of the workday. MTF was not affected on the control day. The center of pressure displacement speed increased significantly over time after standing work but was also affected on the control day. Subjective evaluations of discomfort indicated a significant increase in perception of fatigue immediately after the end of standing work; however, this perception did not persist 30 min after. Age and gender did not influence fatigue. Objective measures show the long-term effects of muscle fatigue after 5 hr of standing work; however, this fatigue is no longer perceived after 30 min of rest postwork. The present results suggest that occupational activities requiring prolonged standing are likely to contribute to lower-extremity and/or back disorders. © 2015, Human Factors and Ergonomics Society.

  1. Fatigue Strength Prediction of Drilling Materials Based on the Maximum Non-metallic Inclusion Size

    NASA Astrophysics Data System (ADS)

    Zeng, Dezhi; Tian, Gang; Liu, Fei; Shi, Taihe; Zhang, Zhi; Hu, Junying; Liu, Wanying; Ouyang, Zhiying

    2015-12-01

    In this paper, the statistics of the size distribution of non-metallic inclusions in five drilling materials were performed. Based on the maximum non-metallic inclusion size, the fatigue strength of the drilling material was predicted. The sizes of non-metallic inclusions in drilling materials were observed to follow the inclusion size distribution rule. Then the maximum inclusion size in the fatigue specimens was deduced. According to the prediction equation of the maximum inclusion size and fatigue strength proposed by Murakami, fatigue strength of drilling materials was obtained. Moreover, fatigue strength was also measured through rotating bending tests. The predicted fatigue strength was significantly lower than the measured one. Therefore, according to the comparison results, the coefficients in the prediction equation were revised. The revised equation allowed the satisfactory prediction results of fatigue strength of drilling materials at the fatigue life of 107 rotations and could be used in the fast prediction of fatigue strength of drilling materials.

  2. Personality Typology in Relation to Muscle Strength

    PubMed Central

    Terracciano, Antonio; Milaneschi, Yuri; Metter, E. Jeffrey; Ferrucci, Luigi

    2011-01-01

    Background Physical inactivity plays a central role in the age-related decline in muscle strength, an important component in the process leading to disability. Personality, a significant determinant of health behaviors including physical activity, could therefore impact muscle strength throughout adulthood and affect the rate of muscle strength decline with aging. Personality typologies combining “high neuroticism” (N≥55), “low extraversion” (E<45), and “low conscientiousness” (C<45) have been associated with multiple risky health behaviors but have not been investigated with regards to muscle strength. Purpose The purpose of this study is to investigate associations between individual and combined typologies consisting of high N, low E, and low C and muscle strength, and whether physical activity and body mass index act as mediators. Method This cross-sectional study includes 1,220 participants from the Baltimore Longitudinal Study of Aging. Results High N was found among 18%, low E among 31%, and low C among 26% of the sample. High levels of N, particularly when combined with either low E or low C, were associated with lower muscle strength compared with having only one or none of these personality types. Facet analyses suggest an important role for the N components of depression and hostility. Physical activity level appears to partly explain some of these associations. Conclusion Findings provide support for the notion that the typological approach to personality may be useful in identifying specific personality types at risk of low muscle strength and offer the possibility for more targeted prevention and intervention programs. PMID:21614452

  3. Muscle fatigue during high-intensity exercise in children.

    PubMed

    Ratel, Sébastien; Duché, Pascale; Williams, Craig A

    2006-01-01

    Children are able to resist fatigue better than adults during one or several repeated high-intensity exercise bouts. This finding has been reported by measuring mechanical force or power output profiles during sustained isometric maximal contractions or repeated bouts of high-intensity dynamic exercises. The ability of children to better maintain performance during repeated high-intensity exercise bouts could be related to their lower level of fatigue during exercise and/or faster recovery following exercise. This may be explained by muscle characteristics of children, which are quantitatively and qualitatively different to those of adults. Children have less muscle mass than adults and hence, generate lower absolute power during high-intensity exercise. Some researchers also showed that children were equipped better for oxidative than glycolytic pathways during exercise, which would lead to a lower accumulation of muscle by-products. Furthermore, some reports indicated that the lower ability of children to activate their type II muscle fibres would also explain their greater resistance to fatigue during sustained maximal contractions. The lower accumulation of muscle by-products observed in children may be suggestive of a reduced metabolic signal, which induces lower ratings of perceived exertion. Factors such as faster phosphocreatine resynthesis, greater oxidative capacity, better acid-base regulation, faster readjustment of initial cardiorespiratory parameters and higher removal of metabolic by-products in children could also explain their faster recovery following high-intensity exercise.From a clinical point of view, muscle fatigue profiles are different between healthy children and children with muscle and metabolic diseases. Studies of dystrophic muscles in children indicated contradictory findings of changes in contractile properties and the muscle fatigability. Some have found that the muscle of boys with Duchenne muscular dystrophy (DMD) fatigued less

  4. Electromyographic assessment of muscle fatigue during isometric vibration training at varying frequencies.

    PubMed

    Mischi, M; Rabotti, C; Cardinale, M

    2010-01-01

    Resistance exercise is essential to improve or maintain muscle performance. Vibration training has been suggested as an alternative option for muscle conditioning, aiming especially at improving muscle strength and power. Several studies link the effects of vibration training to enhanced neuromuscular stimulation, measured by electromyography (EMG) and typically ascribed to involuntary reflex mechanisms. However, the underlying mechanisms are still unclear, limiting the use of vibration training. This paper proposes additional methods to analyze the mechanisms involved in vibration training. A dedicated measurement setup was realized to relate vibration parameters to muscle fatigue in the biceps brachii. Fatigue is estimated by EMG mean frequency and conduction velocity assessments as well as by maximum voluntary contraction (MVC) force measurements. A modified maximum likelihood algorithm is proposed for the conduction velocity estimation based on high-density EMG recording. Five volunteers performed four isometric contractions of 50 s at 80% MVC with no vibration (control) and with superimposed vibration at 20, 30, and 40 Hz. Fatigue was estimated from the decay of force, EMG mean frequency, and EMG conduction velocity. 30-Hz vibrations represented the most fatiguing stimulus. Our preliminary results also show a better correlation between force and conduction velocity decay than between force and mean frequency decay, indicating the former as a better EMG indicator of fatigue. The proposed methods provide important advancements for the analysis of vibration exercise and guidance towards the definition of optimal training protocols.

  5. Effect of antagonist muscle fatigue on knee extension torque.

    PubMed

    Beltman, J G M; Sargeant, A J; Ball, D; Maganaris, C N; de Haan, A

    2003-09-01

    The effect of hamstring fatigue on knee extension torque was examined at different knee angles for seven male subjects. Before and after a dynamic flexion fatigue protocol (180 degrees s(-1), until dynamic torque had declined by 50%), maximal voluntary contraction extension torque was measured at four knee flexion angles (90 degrees, 70 degrees, 50 degrees and 30 degrees ). Maximal torque generating capacity and voluntary activation of the quadriceps muscle were determined using electrical stimulation. Average rectified EMG of the biceps femoris was determined. Mean dynamic flexion torque declined by 48+/-11%. Extensor maximal voluntary contraction torque, maximal torque generating capacity, voluntary activation and average rectified EMG at the four knee angles were unaffected by the hamstring fatigue protocol. Only at 50 degrees knee angle was voluntary activation significantly lower (15.7%) after fatigue ( P<0.05). In addition, average rectified EMG before fatigue was not significantly influenced by knee angle. It was concluded that a fatigued hamstring muscle did not increase the maximal voluntary contraction extension torque and knee angle did not change coactivation. Three possible mechanisms may explain the results: a potential difference in recruited fibre populations in antagonist activity compared with the fibres which were fatigued in the protocol, a smaller loss in isometric torque generating capacity of the hamstring muscle than was expected from the dynamic measurements and/or a reduction in voluntary activation.

  6. Effects of Core-Musculature Fatigue on Maximal Shoulder Strength.

    PubMed

    Rosemeyer, James R; Hayes, Bradley T; Switzler, Craig L; Hicks-Little, Charlie A

    2015-11-01

    Core stability has been shown to affect lower-extremity motion, but activation of the core has also been observed just before movements of the upper extremity. However, there is limited evidence regarding the effects that core musculature has on upper-extremity strength. To determine the effects of core fatigue on maximal shoulder strength. Crossover study. Sports-medicine research laboratory. 23 participants (15 male and 8 female, age 21.3 ± 2.5 y, height 174.5 ± 10.3 cm, weight 71.3 ± 12.0 kg). All participants performed maximal voluntary isometric contractions in 3 different planes (sagittal, frontal, transverse) of shoulder-joint motion. A core-fatiguing protocol was conducted, and the same 3 shoulder-strength tests were repeated and compared with the initial measurements. Strength measures were recorded in kilograms with a dynamometer. Results showed a significant decrease in strength in the frontal (-0.56 ± 1.06 kg, P = .020) and transverse (-0.89 ± 1.49 kg, P = .012) planes but not in the sagittal plane (-0.20 ± 0.98 kg, P > .05). Furthermore, regardless of the specific strength test measured, results revealed that the 1st (-7.05% ± 11.65%, P = .012) and 2nd (-5.71% ± 12.03%, P = .042) strength-test measurements after the fatiguing protocol were significantly decreased, while the 3rd strength-test measurement (-4.19% ± 12.48%, P = .140) did not show statistical significance. These results indicate that decrease in core stability may have an influence on shoulder strength. The literature suggests that the core is designed for endurance, and this study helps validate its recovery properties. Further research is needed to determine the significance of this effect and how injury rates coincide.

  7. Probabilistic analysis for fatigue strength degradation of materials

    NASA Technical Reports Server (NTRS)

    Royce, Lola

    1989-01-01

    This report presents the results of the first year of a research program conducted for NASA-LeRC by the University of Texas at San Antonio. The research included development of methodology that provides a probabilistic treatment of lifetime prediction of structural components of aerospace propulsion systems subjected to fatigue. Material strength degradation models, based on primitive variables, include both a fatigue strength reduction model and a fatigue crack growth model. Linear elastic fracture mechanics is utilized in the latter model. Probabilistic analysis is based on simulation, and both maximum entropy and maximum penalized likelihood methods are used for the generation of probability density functions. The resulting constitutive relationships are included in several computer programs, RANDOM2, RANDOM3, and RANDOM4. These programs determine the random lifetime of an engine component, in mechanical load cycles, to reach a critical fatigue strength or crack size. The material considered was a cast nickel base superalloy, one typical of those used in the Space Shuttle Main Engine.

  8. Bending Fatigue Strength of Austempered Ductile Iron Spur Gears

    NASA Astrophysics Data System (ADS)

    Yamanaka, Masashi; Tamura, Ryo; Inoue, Katsumi; Narita, Yukihito

    This paper deals with an experimental evaluation of bending fatigue strength for austempered ductile iron (ADI) spur gears. The module is 2.5 and the number of teeth is 26 in the test gears. The material of the test gears corresponds to Japan Industrial Standard (JIS) FCAD1100-15. Some gears are processed by one of two types of fine particle bombarding (FPB). The surface roughness is slightly increased by FPB. The obtained strengths are 623 MPa for the as-austempered gears, and 1011 and 1085 MPa for the gears after FPB. The strength is expressed by the fillet stress level, which is calculated by FEM. The strength of a gear with the same dimensions made of carburized SCr420H alloy steel is 1205 MPa, and the strength of the ADI gear is approximately half that of the carburized steel gear. The FPB process has a significant effect on the ADI gear, improving its strength by 62-74%.

  9. Strength Training Improves Fatigue Resistance and Self-Rated Health in Workers with Chronic Pain: A Randomized Controlled Trial

    PubMed Central

    Jakobsen, Markus Due; Jay, Kenneth

    2016-01-01

    Chronic musculoskeletal pain is widespread in the working population and leads to muscular fatigue, reduced work capacity, and fear of movement. While ergonomic intervention is the traditional approach to the problem, physical exercise may be an alternative strategy. This secondary analysis of a randomized controlled trial investigates the effect of strength training on muscular fatigue resistance and self-rated health among workers with chronic pain. Sixty-six slaughterhouse workers with chronic upper limb pain and work disability were randomly allocated to 10 weeks of strength training or usual care ergonomic training (control). At baseline and follow-up, participants performed a handgrip muscular fatigue test (time above 50% of maximal voluntary contraction force) with simultaneous recording of electromyography. Additionally, participants replied to a questionnaire regarding self-rated health and pain. Time to fatigue, muscle strength, hand/wrist pain, and self-rated health improved significantly more following strength training than usual care (all P < 0.05). Time to fatigue increased by 97% following strength training and this change was correlated to the reduction in fear avoidance (Spearman's rho = −0.40; P = 0.01). In conclusion, specific strength training improves muscular fatigue resistance and self-rated health and reduces pain of the hand/wrist in manual workers with chronic upper limb pain. This trial is registered with ClinicalTrials.gov NCT01671267. PMID:27830144

  10. Strength Training Improves Fatigue Resistance and Self-Rated Health in Workers with Chronic Pain: A Randomized Controlled Trial.

    PubMed

    Sundstrup, Emil; Jakobsen, Markus Due; Brandt, Mikkel; Jay, Kenneth; Aagaard, Per; Andersen, Lars Louis

    2016-01-01

    Chronic musculoskeletal pain is widespread in the working population and leads to muscular fatigue, reduced work capacity, and fear of movement. While ergonomic intervention is the traditional approach to the problem, physical exercise may be an alternative strategy. This secondary analysis of a randomized controlled trial investigates the effect of strength training on muscular fatigue resistance and self-rated health among workers with chronic pain. Sixty-six slaughterhouse workers with chronic upper limb pain and work disability were randomly allocated to 10 weeks of strength training or usual care ergonomic training (control). At baseline and follow-up, participants performed a handgrip muscular fatigue test (time above 50% of maximal voluntary contraction force) with simultaneous recording of electromyography. Additionally, participants replied to a questionnaire regarding self-rated health and pain. Time to fatigue, muscle strength, hand/wrist pain, and self-rated health improved significantly more following strength training than usual care (all P < 0.05). Time to fatigue increased by 97% following strength training and this change was correlated to the reduction in fear avoidance (Spearman's rho = -0.40; P = 0.01). In conclusion, specific strength training improves muscular fatigue resistance and self-rated health and reduces pain of the hand/wrist in manual workers with chronic upper limb pain. This trial is registered with ClinicalTrials.gov NCT01671267.

  11. Sternomastoid muscle fatigue and twitch maximum relaxation rate in patients with steroid dependent asthma.

    PubMed Central

    Mak, V. H.; Bugler, J. R.; Spiro, S. G.

    1993-01-01

    BACKGROUND--Long term oral corticosteroid treatment is a cause of myopathy of the skeletal muscles. The effect of long term treatment with oral corticosteroids on the respiratory muscles is uncertain. Respiratory muscle function and fatigue in sternomastoid muscle were investigated in a group of patients with chronic severe asthma who were taking oral corticosteroids. The results were compared with those from a group of patients with chronic airflow limitation who were not taking oral steroids. METHODS--Twelve patients with chronic severe asthma, taking a mean daily dosage of 8 mg of prednisolone for a mean (SD) of 16.8 (9.1) years, were compared with patients with chronic airflow limitation and individually matched for sex, age, and severity of airflow limitation. Lung function tests, maximal mouth pressures, and quadriceps and sternomastoid muscle strength were measured. The sternomastoid muscle was fatigued by maximal headlift exercise to 70% of initial headlift force and the endurance time noted. Sternomastoid fatigue was assessed by twitch maximum relaxation rate (TMRR) measured in the fresh state and for 30 minutes after exercise. RESULTS--There was no significant difference between the control group and the corticosteroid group for maximal mouth pressures, fresh state TMRR, and quadriceps and sternomastoid strength. The control group had a significantly longer mean (SD) endurance time than the corticosteroid group (121 (47) s v 86 (24) s), and also had significantly less slowing and faster recovery of the TMRR after exercise. The slowing and recovery of the TMRR in the corticosteroid group, however, was similar to that previously reported for normal subjects. CONCLUSION--Respiratory muscle weakness does not occur more often in patients taking oral corticosteroids. The corticosteroid group was more prone to fatigue than the control group, but was similar to normal subjects. This suggests that chronic airflow limitation may produce a training effect on the

  12. Effects of Neuromuscular Fatigue on Quadriceps Strength and Activation and Knee Biomechanics in Individuals post Anterior Cruciate Ligament Reconstruction and Healthy Adults

    PubMed Central

    Thomas, Abbey C.; Lepley, Lindsey K.; Wojtys, Edward M.; McLean, Scott G.; Palmieri-Smith, Riann M.

    2016-01-01

    Study design Laboratory based experiment using a pre/post-test design. Objectives To determine the effects of neuromuscular fatigue on quadriceps strength and activation and sagittal and frontal plane knee biomechanics during dynamic landing following anterior cruciate ligament reconstruction (ACLr). Background Impaired quadriceps central activation occurs post-ACLr, likely altering lower extremity biomechanics. Neuromuscular fatigue similarly reduces volitional muscle activation and impairs neuromuscular control. Upon return to full activity post-ACLr, individuals likely concurrently experience quadriceps central activation deficits and neuromuscular fatigue, though the effects of fatigue on muscle strength and activation and biomechanics post-ACLr are unknown. Methods Seventeen individuals 7–10 months post-ACLr and 16 controls participated. Quadriceps strength and central activation ratio were recorded pre-/post-fatigue, which was induced via sets of double-leg squats. Knee biomechanics were recorded during a dynamic landing activity pre-/post-fatigue. Results Both groups demonstrated smaller knee flexion (initial contact:P=.017; peak:P=.004) and abduction (initial contact:P=.005; peak:P=.009) angles post-fatigue. The ACLr group had smaller peak knee flexion angles (P<.001) pre- and post-fatigue than controls. Knee flexion moment was smaller in ACLr than controls pre- (P<.001), but not post-fatigue (P=.103). Controls had smaller knee flexion moments post-fatigue (P=.001). Knee abduction moment was smaller in both groups post-fatigue (P=.003). All participants demonstrated significantly lower strength (P<.001) and activation (P=.003) post-fatigue. Conclusion Impaired strength, central activation, and biomechanics presented post-fatigue in both groups, confirming that neuromuscular fatigue may increase non-contact ACL injury risk. However, these changes were not exaggerated in ACLr participants, likely because they already demonstrated a stiff-legged landing

  13. Stochastic models for the tensile strength, fatigue

    NASA Technical Reports Server (NTRS)

    Phoenix, S. L.

    1976-01-01

    The time-to-failure of a single fiber is modeled as a functional of the fiber load history and reasonable forms for this functional are proposed. Earlier models by Daniels and Coleman are shown to be special cases of the proposed model and apparent disparities in their behavior are discussed. Techniques are presented for determining analytically the asymptotic distributions of the tensile strength and time-to-failure for bundles of a large number of fibers. For smaller bundles, exact results are far too cumbersome to be of use so that efficient Monte Carlo simulation procedures are proposed.

  14. Stochastic models for the tensile strength, fatigue

    NASA Technical Reports Server (NTRS)

    Phoenix, S. L.

    1976-01-01

    The time-to-failure of a single fiber is modeled as a functional of the fiber load history and reasonable forms for this functional are proposed. Earlier models by Daniels and Coleman are shown to be special cases of the proposed model and apparent disparities in their behavior are discussed. Techniques are presented for determining analytically the asymptotic distributions of the tensile strength and time-to-failure for bundles of a large number of fibers. For smaller bundles, exact results are far too cumbersome to be of use so that efficient Monte Carlo simulation procedures are proposed.

  15. Sarcolipin overexpression improves muscle energetics and reduces fatigue.

    PubMed

    Sopariwala, Danesh H; Pant, Meghna; Shaikh, Sana A; Goonasekera, Sanjeewa A; Molkentin, Jeffery D; Weisleder, Noah; Ma, Jianjie; Pan, Zui; Periasamy, Muthu

    2015-04-15

    Sarcolipin (SLN) is a regulator of sarcoendoplasmic reticulum calcium ATPase in skeletal muscle. Recent studies using SLN-null mice have identified SLN as a key player in muscle thermogenesis and metabolism. In this study, we exploited a SLN overexpression (Sln(OE)) mouse model to determine whether increased SLN level affected muscle contractile properties, exercise capacity/fatigue, and metabolic rate in whole animals and isolated muscle. We found that Sln(OE) mice are more resistant to fatigue and can run significantly longer distances than wild-type (WT). Studies with isolated extensor digitorum longus (EDL) muscles showed that Sln(OE) EDL produced higher twitch force than WT. The force-frequency curves were not different between WT and Sln(OE) EDLs, but at lower frequencies the pyruvate-induced potentiation of force was significantly higher in Sln(OE) EDL. SLN overexpression did not alter the twitch and force-frequency curve in isolated soleus muscle. However, during a 10-min fatigue protocol, both EDL and soleus from Sln(OE) mice fatigued significantly less than WT muscles. Interestingly, Sln(OE) muscles showed higher carnitine palmitoyl transferase-1 protein expression, which could enhance fatty acid metabolism. In addition, lactate dehydrogenase expression was higher in Sln(OE) EDL, suggesting increased glycolytic capacity. We also found an increase in store-operated calcium entry (SOCE) in isolated flexor digitorum brevis fibers of Sln(OE) compared with WT mice. These data allow us to conclude that increased SLN expression improves skeletal muscle performance during prolonged muscle activity by increasing SOCE and muscle energetics.

  16. Sarcolipin overexpression improves muscle energetics and reduces fatigue

    PubMed Central

    Sopariwala, Danesh H.; Pant, Meghna; Shaikh, Sana A.; Goonasekera, Sanjeewa A.; Molkentin, Jeffery D.; Weisleder, Noah; Ma, Jianjie; Pan, Zui

    2015-01-01

    Sarcolipin (SLN) is a regulator of sarcoendoplasmic reticulum calcium ATPase in skeletal muscle. Recent studies using SLN-null mice have identified SLN as a key player in muscle thermogenesis and metabolism. In this study, we exploited a SLN overexpression (SlnOE) mouse model to determine whether increased SLN level affected muscle contractile properties, exercise capacity/fatigue, and metabolic rate in whole animals and isolated muscle. We found that SlnOE mice are more resistant to fatigue and can run significantly longer distances than wild-type (WT). Studies with isolated extensor digitorum longus (EDL) muscles showed that SlnOE EDL produced higher twitch force than WT. The force-frequency curves were not different between WT and SlnOE EDLs, but at lower frequencies the pyruvate-induced potentiation of force was significantly higher in SlnOE EDL. SLN overexpression did not alter the twitch and force-frequency curve in isolated soleus muscle. However, during a 10-min fatigue protocol, both EDL and soleus from SlnOE mice fatigued significantly less than WT muscles. Interestingly, SlnOE muscles showed higher carnitine palmitoyl transferase-1 protein expression, which could enhance fatty acid metabolism. In addition, lactate dehydrogenase expression was higher in SlnOE EDL, suggesting increased glycolytic capacity. We also found an increase in store-operated calcium entry (SOCE) in isolated flexor digitorum brevis fibers of SlnOE compared with WT mice. These data allow us to conclude that increased SLN expression improves skeletal muscle performance during prolonged muscle activity by increasing SOCE and muscle energetics. PMID:25701006

  17. Effects of unilateral leg muscle fatigue on balance control in perturbed and unperturbed gait in healthy elderly.

    PubMed

    Toebes, Marcel J P; Hoozemans, Marco J M; Dekker, Joost; van Dieën, Jaap H

    2014-01-01

    This study assessed effects of unilateral leg muscle fatigue (ULMF) on balance control in gait during the stance and swing phases of the fatigued leg in healthy elderly, to test the assumption that leg muscle strength limits balance control during the stance-phase. Ten subjects (aged 63.4, SD 5.5 years) walked on a treadmill in 4 conditions: unperturbed unfatigued, unperturbed fatigued, perturbed unfatigued, and perturbed fatigued. The perturbations were lateral trunk pulls just before contralateral heel contact. ULMF was evoked by unilateral squat exercise until task failure. Isometric knee extension strength was measured to verify the presence of muscle fatigue. Between-stride standard deviations and Lyapunov exponents of trunk kinematics were used as indicators of balance control. Required perturbation force and the deviation of trunk kinematics from unperturbed gait were used to assess perturbation responses. Knee extension strength decreased considerably (17.3% SD 8.6%) as a result ULMF. ULMF did not affect steady-state gait balance. Less force was required to perturb subjects when the fatigued leg was in the stance-phase compared to the swing-phase. Subjects showed a faster return to the unperturbed gait pattern in the fatigued than in the unfatigued condition, after perturbations in swing and stance of the fatigued leg. The results of this study are not in line with the hypothesized effects of leg muscle fatigue on balance in gait. The healthy elderly subjects were able to cope with substantial ULMF during steady-state gait and demonstrated faster balance recovery after laterally directed mechanical perturbations in the fatigued than in the unfatigued condition. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Abdominal muscle fatigue following exercise in chronic obstructive pulmonary disease

    PubMed Central

    2010-01-01

    Background In patients with chronic obstructive pulmonary disease, a restriction on maximum ventilatory capacity contributes to exercise limitation. It has been demonstrated that the diaphragm in COPD is relatively protected from fatigue during exercise. Because of expiratory flow limitation the abdominal muscles are activated early during exercise in COPD. This adds significantly to the work of breathing and may therefore contribute to exercise limitation. In healthy subjects, prior expiratory muscle fatigue has been shown itself to contribute to the development of quadriceps fatigue. It is not known whether fatigue of the abdominal muscles occurs during exercise in COPD. Methods Twitch gastric pressure (TwT10Pga), elicited by magnetic stimulation over the 10th thoracic vertebra and twitch transdiaphragmatic pressure (TwPdi), elicited by bilateral anterolateral magnetic phrenic nerve stimulation were measured before and after symptom-limited, incremental cycle ergometry in patients with COPD. Results Twenty-three COPD patients, with a mean (SD) FEV1 40.8(23.1)% predicted, achieved a mean peak workload of 53.5(15.9) W. Following exercise, TwT10Pga fell from 51.3(27.1) cmH2O to 47.4(25.2) cmH2O (p = 0.011). TwPdi did not change significantly; pre 17.0(6.4) cmH2O post 17.5(5.9) cmH2O (p = 0.7). Fatiguers, defined as having a fall TwT10Pga ≥ 10% had significantly worse lung gas transfer, but did not differ in other exercise parameters. Conclusions In patients with COPD, abdominal muscle but not diaphragm fatigue develops following symptom limited incremental cycle ergometry. Further work is needed to establish whether abdominal muscle fatigue is relevant to exercise limitation in COPD, perhaps indirectly through an effect on quadriceps fatigability. PMID:20132549

  19. A review of concepts regarding the origin of respiratory muscle fatigue

    NASA Astrophysics Data System (ADS)

    Kuraszkiewicz, Bożena; Piotrkiewicz, Maria

    2011-01-01

    In this review, the classification of respiratory muscle fatigue from the perspective of its origin is presented. The fatigue is classified as central or peripheral, and the latter further subdivided into high- and low-frequency fatigue. However, muscle fatigue is a complex process and all three types of fatigue probably occur simultaneously in the overloaded respiratory muscles. The relative importance of each type depends on the duration of respiratory loading and other physiological variables. However, central and high-frequency fatigue resolve rapidly once muscle overload is removed, whereas low-frequency fatigue persists over long time.

  20. Muscle strength in patients with acromegaly at diagnosis and during long-term follow-up.

    PubMed

    Füchtbauer, Laila; Olsson, Daniel S; Bengtsson, Bengt-Åke; Norrman, Lise-Lott; Sunnerhagen, Katharina S; Johannsson, Gudmundur

    2017-08-01

    Patients with acromegaly have decreased body fat (BF) and increased extracellular water (ECW) and muscle mass. Although there is a lack of systematic studies on muscle function, it is believed that patients with acromegaly may suffer from proximal muscle weakness despite their increased muscle mass. We studied body composition and muscle function in untreated acromegaly and after biochemical remission. Prospective observational study. Patients with acromegaly underwent measurements of muscle strength (dynamometers) and body composition (four-compartment model) at diagnosis (n = 48), 1 year after surgery (n = 29) and after long-term follow-up (median 11 years) (n = 24). Results were compared to healthy subjects. Untreated patients had increased body cell mass (113 ± 9% of predicted) and ECW (110 ± 20%) and decreased BF (67 ± 7.6%). At one-year follow-up, serum concentration of IGF-I was reduced and body composition had normalized. At baseline, isometric muscle strength in knee flexors and extensors was normal and concentric strength was modestly increased whereas grip strength and endurance was reduced. After one year, muscle strength was normal in both patients with still active disease and patients in remission. At long-term follow-up, all patients were in remission. Most muscle function tests remained normal, but isometric flexion and the fatigue index were increased to 153 ± 42% and 139 ± 28% of predicted values, respectively. Patients with untreated acromegaly had increased body cell mass and normal or modestly increased proximal muscle strength, whereas their grip strength was reduced. After biochemical improvement and remission, body composition was normalized, hand grip strength was increased, whereas proximal muscle fatigue increased. © 2017 European Society of Endocrinology.

  1. Effect of diazepam on calcium translocation during physiological muscle fatigue.

    PubMed

    Bianchi, C P; Narayan, S R

    1984-10-01

    Stimulation of frog sartorius muscle at 1 Hz leads to an initial positive staircase during the first 120 twitches and is followed by a negative staircase. There is a net calcium influx into two distinct compartments within the muscle during the positive staircase. The two compartments are separated by measuring the calcium extracted from muscles soaked in strontium-Ringer for 15 min and the calcium remaining in the muscle. A net gain of extractable Ca++ (0.32 mumol/g wet wt.) and residual Ca++ (0.18 mumol/g) is observed during positive staircase. A loss in residual Ca++, a gain in extractable Ca++ and a net loss of Ca++ (0.09 mumol/g) to the bathing medium occur during the period preceding physiological muscle fatigue (60 to 120 twitches). Diazepam (EC50, 5.6 X 10(-6) M) causes a marked reduction in the latent period and increases the rate constant 2.6 times the control value for physiological muscle fatigue. A net loss of 0.31 mumol/g of Ca++ to the bathing medium occurs during the interval between 60 and 120 twitches. Diazepam increases net Ca++ efflux 3.5-fold during this interval when compared to control muscles. Diazepam does not affect the Ca++ gained during the positive staircase but accelerates the loss of calcium from the residual and the extractable compartments during the initial phase of physiological muscle fatigue. Physiological muscle fatigue is attributed to an accumulation of calcium in the transverse tubular network and an uncoupling of the muscle action potential from contraction.

  2. Muscle strength in breast cancer patients receiving different treatment regimes

    PubMed Central

    Klassen, Oliver; Schmidt, Martina E.; Ulrich, Cornelia M.; Schneeweiss, Andreas; Potthoff, Karin; Steindorf, Karen

    2016-01-01

    Abstract Background Muscle dysfunction and sarcopenia have been associated with poor performance status, an increased mortality risk, and greater side effects in oncologic patients. However, little is known about how performance is affected by cancer therapy. We investigated muscle strength in breast cancer patients in different adjuvant treatment settings and also compared it with data from healthy individuals. Methods Breast cancer patients (N = 255) from two randomized controlled exercise trials, staged 0–III and aged 54.4 ± 9.4 years, were categorized into four groups according to their treatment status. In a cross‐sectional design, muscle function was assessed bilaterally by isokinetic dynamometry (0°, 60°, 180°/s) as maximal voluntary isometric contraction (MVIC) and maximal isokinetic peak torque (MIPT) in shoulder rotators and knee flexors and extensors. Additionally, muscular fatigue index (FI%) and shoulder flexibility were evaluated. Healthy women (N = 26), aged 53.3 ± 9.8 years, were tested using the same method. Analysis of covariance was used to estimate the impact of different cancer treatments on skeletal muscle function with adjustment for various clinical and socio‐demographic factors. Results Consistently, lower muscle strength was measured in shoulder and knee strength in patients after chemotherapy. On average, patients had up to 25% lower strength in lower extremities and 12–16% in upper extremities in MVIC and MIPT during cancer treatment compared with healthy women. No substantial difference between patient groups in shoulder strength, but significantly lower shoulder flexibility in patients with radical mastectomy was measured. Chemotherapy‐treated patients had consistently higher FI%. No serious adverse events were reported. Conclusions Breast cancer patients showed markedly impaired muscle strength and joint dysfunctions before and after anticancer treatment. The significant differences between patients

  3. Review on fatigue behavior of high-strength concrete after high temperature

    NASA Astrophysics Data System (ADS)

    Zhao, Dongfu; Jia, Penghe; Gao, Haijing

    2017-06-01

    The fatigue of high-strength concrete after high temperature has begun to attract attention. But so far the researches work about the fatigue of high-strength concrete after high temperature have not been reported. This article based on a large number of literature. The research work about the fatigue of high-strength concrete after high temperature are reviewed, analysed and expected, which can provide some reference for the experimental study of fatigue damage analysis.

  4. Effects of high-intensity blood flow restriction exercise on muscle fatigue.

    PubMed

    Neto, Gabriel R; Santos, Heleodório H; Sousa, Juliana B C; Júnior, Adenilson T A; Araújo, Joamira P; Aniceto, Rodrigo R; Sousa, Maria S C

    2014-06-28

    Strength training combined with blood flow restriction (BFR) have been used to improve the levels of muscle adaptation. The aim of this paper was to investigate the acute effect of high intensity squats with and without blood flow restriction on muscular fatigue levels. Twelve athletes (aged 25.95 ± 0.84 years) were randomized into two groups: without Blood Flow Restriction (NFR, n = 6) and With Blood Flow Restriction (WFR, n = 6) that performed a series of free weight squats with 80% 1-RM until concentric failure. The strength of the quadriceps extensors was assessed in a maximum voluntary isometric contraction integrated to signals from the surface electromyogram. The average frequency showed significant reductions in the WFR group for the vastus lateralis and vastus medialis muscles, and intergroup only for the vastus medialis. In conclusion, a set of squats at high intensity with BFR could compromise muscle strength immediately after exercise, however, differences were not significant between groups.

  5. Diaphragmatic fatigue during inspiratory muscle loading in normoxia and hypoxia.

    PubMed

    Walker, David Johannes; Farquharson, Franziska; Klenze, Hannes; Walterspacher, Stephan; Storz, Lucia; Duerschmied, Daniel; Roecker, Kai; Kabitz, Hans-Joachim

    2016-06-15

    Diaphragmatic fatigue (DF) occurs during strenuous loading of respiratory muscles (e.g., heavy-intensity whole-body exercise, normocapnic hyperpnea, inspiratory resistive breathing). DF develops early on during normoxia, without further decline toward task failure; however, its progression during inspiratory muscle loading in during hypoxia remains unclear. Therefore, the present study used volume-corrected transdiaphragmatic pressures during supramaximal magnetic phrenic nerve stimulation (Pdi,twc) to investigate the effect of hypoxia on the progression of diaphragmatic fatigue during inspiratory muscle loading. Seventeen subjects completed two standardized rounds of inspiratory muscle loading (blinded, randomized) under the following conditions: (i) normoxia, and (ii) normobaric hypoxia (SpO2 80%), with Pdi,twc assessment every 45 s. In fatiguers (i.e., Pdi,twc reduction >10%, n=10), biometric approximation during normoxia is best represented by Pdi,twc=4.06+0.83 exp(-0.19 × x), in contrast to Pdi,twc=4.38-(0.05 × x) during hypoxia. Progression of diaphragmatic fatigue during inspiratory muscle loading assessed by Pdi,tw differs between normoxia and normobaric hypoxia: in the former, Pdi,tw follows an exponential decay, whereas during hypoxia, Pdi,tw follows a linear decline. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Evaluation of muscle fatigue during 100-m front crawl.

    PubMed

    Stirn, Igor; Jarm, Tomaz; Kapus, Venceslav; Strojnik, Vojko

    2011-01-01

    The aim of this study was to evaluate muscle fatigue in upper body muscles during 100-m all-out front crawl. Surface electromyogram (EMG) was collected from the pectoralis major, latissimus dorsi and triceps brachii muscles of 11 experienced swimmers. Blood lactate concentration level increased to 14.1 ± 2.9 mmol l(-1) 5 min after the swim. The velocity, stroke length and stroke rate calculated based on video analysis decreased by 15.0, 5.8 and 7.4%, respectively, during the swim. EMG amplitude of the triceps and the lower part of the latissimus muscles increased, whilst the mean power frequency (MNF) of all muscles significantly decreased by 20-25%. No significant differences in the relative MNF decrease were observed amongst the muscles; however, the differences in the rate of the MNF decrease between the lower part of the latissimus and the triceps brachii muscles were found (P < 0.05). The time of rest between the muscle activation of the two consecutive arm strokes at the end of swimming was extended (P < 0.05). It was concluded that 100-m all-out crawl induced significant fatigue with no evident differences amongst the analysed muscles.

  7. Role of excitation-contraction coupling in muscle fatigue.

    PubMed

    Allen, D G; Westerblad, H; Lee, J A; Lännergren, J

    1992-02-01

    The force produced by muscles declines during prolonged activity and this decline arises largely from processes within the muscle. At a cellular level the reduced force could be caused by: (a) reduced intracellular calcium release during activity; (b) reduced sensitivity of the myofilaments to calcium; or (c) reduced maximal force development. Experiments involving intracellular calcium measurements in isolated single fibres show that all 3 of the above contribute to the decline of force during fatigue. Metabolic changes associated with fatigue are probably involved in each of the 3 factors. Thus the accumulation of phosphate and protons which occur during fatigue cause a reduction in calcium sensitivity and a decline in maximal force. The cause of the reduced intracellular calcium during contractions in fatigue is less clear. During prolonged tetani the conduction of the action potential in the T-tubules appears to fail leading to reduced intracellular calcium in the central part of the muscle fibre. However, during repeated tetani there is a uniform decline of intracellular calcium across the fibre and this remains one of the least understood processes which contribute to fatigue.

  8. The effects of muscle fatigue on shoulder joint position sense.

    PubMed

    Carpenter, J E; Blasier, R B; Pellizzon, G G

    1998-01-01

    Proprioception, or joint position sense, probably plays an important role in shoulder joint function. In this study, we assessed the effect of muscle fatigue on shoulder proprioception in 20 volunteers with no shoulder abnormalities. Shoulder proprioception was measured as the threshold to first detection of humeral rotation with the joint at 90 degrees of abduction and 90 degrees of external rotation. Subjects were tested while rested, exercised on a isokinetic testing machine until fatigued, and then retested in an identical fashion. Both shoulders were tested, and the order of dominant and nondominant shoulder was randomized. Shoulder proprioception was analyzed for its dependence on arm dominance, direction of rotation, and muscle fatigue. Subjects detected external rotation after significantly less movement than they did internal rotation. Overall, before exercise, motion was detected after a mean of 0.92 degrees of rotation. After exercise, this threshold to detection of movement increased to 1.59 degrees, an increase of 73%. This significant increase occurred with both internal and external rotation. The decrease in proprioceptive sense with muscle fatigue may play a role in decreasing athletic performance and in fatigue-related shoulder dysfunction. It remains to be determined if training can lessen this loss in position sense.

  9. Therapeutic effects of massage and electrotherapy on muscle tone, stiffness and muscle contraction following gastrocnemius muscle fatigue

    PubMed Central

    Wang, Joong-San

    2017-01-01

    [Purpose] This study aimed to examine the effects of a combined intervention consisting of massage therapy and transcutaneous electrical nerve stimulation on gastrocnemius muscle fatigue, assessing whether the intervention improved muscle tone, stiffness, and muscle contraction. [Subjects and Methods] The subjects were 20 healthy males in their 20s who were equally divided into a transcutaneous electrical nerve stimulation group and a combined therapy group that received a combination of massage therapy and transcutaneous electrical nerve stimulation. Muscle fatigue was triggered on the gastrocnemius muscle, and the effects of intervention method on muscle tone, stiffness, and muscle contraction were examined over time. [Results] Lateral and medial gastrocnemius muscle tone and stiffness significantly increased and gastrocnemius muscle contraction significantly decreased in each group immediately after fatigue was triggered on the gastrocnemius muscle. There was no difference in the effects of the two intervention methods over time. [Conclusion] This study verified that a combined therapy of massage therapy and transcutaneous electrical nerve stimulation was able to be used effectively in improving muscle tone, stiffness, muscle contraction, thereby reducing gastrocnemius muscle fatigue. PMID:28210061

  10. Human jaw muscle strength and size in relation to limb muscle strength and size.

    PubMed

    Raadsheer, M C; Van Eijden, T M G J; Van Ginkel, F C; Prahl-Andersen, B

    2004-10-01

    The aim of the present study was to investigate to what extent general factors (e.g. genotype, hormones) and factors at the craniofacial level (e.g. craniofacial size, jaw muscle architecture) contribute to the size and strength of the jaw muscles. A strong relationship of jaw muscle size and strength with that of other muscles would argue for general influences, whereas a weak relationship would argue for craniofacial influences. In 121 adult individuals, moments of maximal bite force, arm flexion force and leg extension force were measured. In addition, thicknesses of jaw muscles, arm flexor muscles and leg extensor muscles were measured using ultrasound. Relationships were assessed by using a principal component analysis. In females, one component was found in which all force moments were represented. Bite force moment, however, loaded very low. In males, two components were found. One component loaded for arm flexion and leg extension moments, the other loaded for bite force moments. In both females and males, only one component was found for the muscle thicknesses in which all muscle groups loaded similarly. It was concluded that the size of the jaw muscles was significantly related to the size of the limb muscles, suggesting that they were both subject to the same general influences. Maximal voluntary bite force moments were not significantly related to the moments of the arm flexion and leg extension forces, suggesting that besides the general influence on the muscle size, variation in bite force moment was also influenced by local variables, such as craniofacial morphology.

  11. Fatigue strength of a single lap joint SPR-bonded

    SciTech Connect

    Di Franco, G.; Fratini, L.; Pasta, A.

    2011-05-04

    In the last years, hybrid joints, meaning with this the joints which consist in combining a traditional mechanical joint to a layer of adhesive, are gradually attracting the attention of various sectors of the construction of vehicles and transportation industries, for their better performance compared to just mechanical joints (self-piercing riveting SPR, riveting, and so on) or just to bonded joints.The paper investigates the fatigue behavior of a single lap joint self-piercing riveted (SPR) and bonded throughout fatigue tests. The considered geometric configuration allowed the use of two rivets placed longitudinally; an epoxy resin was used as adhesive. In the first part of the work static characterization of the joints was carried out through tensile tests. Then fatigue tests were made with the application of different levels of load. The fatigue curves were also obtained at the varying the distance between the two rivets in order to better assess the joint strength for a given length of overlap.

  12. Anomolous Fatigue Crack Growth Phenomena in High-Strength Steel

    NASA Technical Reports Server (NTRS)

    Forth, Scott C.; James, Mark A.; Johnston, William M., Jr.; Newman, James C., Jr.

    2004-01-01

    The growth of a fatigue crack through a material is the result of a complex interaction between the applied loading, component geometry, three-dimensional constraint, load history, environment, material microstructure and several other factors. Previous studies have developed experimental and computational methods to relate the fatigue crack growth rate to many of the above conditions, with the intent of discovering some fundamental material response, i.e. crack growth rate as a function of something. Currently, the technical community uses the stress intensity factor solution as a simplistic means to relate fatigue crack growth rate to loading, geometry and all other variables. The stress intensity factor solution is a very simple linear-elastic representation of the continuum mechanics portion of crack growth. In this paper, the authors present fatigue crack growth rate data for two different high strength steel alloys generated using standard methods. The steels exhibit behaviour that appears unexplainable, compared to an aluminium alloy presented as a baseline for comparison, using the stress intensity factor solution.

  13. Effects of aerobic and strength exercise on motor fatigue in men and women with multiple sclerosis: a randomized controlled trial.

    PubMed

    Surakka, Jukka; Romberg, Anders; Ruutiainen, Juhani; Aunola, Sirkka; Virtanen, Arja; Karppi, Sirkka-Liisa; Mäentaka, Kari

    2004-11-01

    To investigate the effects of aerobic and strength exercise on motor fatigue of knee flexor and extensor muscles in subjects with multiple sclerosis (MS). A randomized controlled trial. At Masku Neurological Rehabilitation Centre, Masku, and the Social Insurance Institution, Research Department, Turku, Finland. Ninety-five MS patients with mild to moderate disability were randomized into exercise group (n =47) and a control group (n =48). Participants in the exercise group attended in a supervised exercise period of three weeks, which was followed by a home exercise programme lasting for 23 weeks. Patients in the control group continued with their normal living. Motor fatigue of knee flexor and extensor muscles was measured during a static 30-s maximal sustained muscle contraction. The decline in force (Nm) during the 30 s was recorded, and a fatigue index (FI) was calculated. Subjective fatigue was measured by using the Fatigue Severity Scale (FSS). The Ambulatory Fatigue Index (AFI) was calculated on the basis of a 500-m walking test. Assessment took place at baseline, at the third week (not for the control group) and at the 26th week. All outcome variables were analysed, men and women together, and some interesting contrasts were analysed by gender. Associations were observed with changes in extension FI and Expanded Disability Status Scale (EDSS) score and mean extension torque (Nm), but not with changes in FI and aerobic or strength exercise activity, mean AFI, mean FSS or in mean knee flexion torque. AFI was decreased in all subject groups (p =0.007). Motor fatigue was reduced in knee flexion (p=0.0014) and extension (ns) among female but not in male exercisers after six months of exercise. The exercise activity of women was 25% higher than that of the men. Six months of exercise reduced motor fatigue in women, but not in men.

  14. Strength training induces muscle hypertrophy and functional gains in black prostate cancer patients despite androgen deprivation therapy.

    PubMed

    Hanson, Erik D; Sheaff, Andrew K; Sood, Suchi; Ma, Lei; Francis, Jack D; Goldberg, Andrew P; Hurley, Ben F

    2013-04-01

    Androgen deprivation therapy (ADT) for prostate cancer (PCa) is associated with weakness, fatigue, sarcopenia, and reduced quality of life (QoL). Black men have a higher incidence and mortality from PCa than Caucasians. We hypothesized that despite ADT, strength training (ST) would increase muscle power and size, thereby improving body composition, physical function, fatigue levels, and QoL in older black men with PCa. Muscle mass, power, strength, endurance, physical function, fatigue perception, and QoL were measured in 17 black men with PCa on ADT before and after 12 weeks of ST. Within-group differences were determined using t tests and regression models. ST significantly increased total body muscle mass (2.7%), thigh muscle volume (6.4%), power (17%), and strength (28%). There were significant increases in functional performance (20%), muscle endurance (110%), and QoL scores (7%) and decreases in fatigue perception (38%). Improved muscle function was associated with higher functional performance (R (2) = 0.54) and lower fatigue perception (R (2) = 0.37), and both were associated with improved QoL (R (2) = 0.45), whereas fatigue perception tended to be associated with muscle endurance (R (2) = 0.37). ST elicits muscle hypertrophy even in the absence of testosterone and is effective in counteracting the adverse functional consequences of ADT in older black men with PCa. These improvements are associated with reduced fatigue perception, enhanced physical performance, and improved QoL. Thus, ST may be a safe and well-tolerated therapy to prevent the loss of muscle mass, strength, and power commonly observed during ADT.

  15. Corrosion fatigue of high strength fastener materials in seawater. Final report

    SciTech Connect

    Tipton, D.G.

    1983-12-01

    Environmental effects can significantly reduce the fatigue life of metals. As such, corrosion fatigue is a major concern in the engineering application of high strength fasteners in marine environments. The corrosion fatigue failure of an AISI 41L40 high strength steel blade-to-hub attachment bolt at the MOD-0A 200 kW wind turbine generator in Oahu, Hawaii prompted the current test program. Tests were undertaken to confirm the dramatic reduction of fatigue strength of AISI 41L40 in marine environments and to obtain similar corrosion fatigue data for candidate replacement materials. AISI 41L40, AISI 4140, PH 13-8Mo stainless steel, alloy 718 and alloy MP-35N were tested in axial fatigue at a frequency of 20 Hz in dry air and natural seawater. The fatigue data were fitted by regression equations to allow determination of fatigue strength for a given number of cycles to failure.

  16. Interpolated twitches in fatiguing single mouse muscle fibres: implications for the assessment of central fatigue.

    PubMed

    Place, Nicolas; Yamada, Takashi; Bruton, Joseph D; Westerblad, Håkan

    2008-06-01

    An electrically evoked twitch during a maximal voluntary contraction (twitch interpolation) is frequently used to assess central fatigue. In this study we used intact single muscle fibres to determine if intramuscular mechanisms could affect the force increase with the twitch interpolation technique. Intact single fibres from flexor digitorum brevis of NMRI mice were dissected and mounted in a chamber equipped with a force transducer. Free myoplasmic [Ca2+] ([Ca2+](i)) was measured with the fluorescent Ca2+ indicator indo-1. Seven fibres were fatigued with repeated 70 Hz tetani until 40% initial force with an interpolated pulse evoked every fifth tetanus. Results showed that the force generated by the interpolated twitch increased throughout fatigue, being 9 +/- 1% of tetanic force at the start and 19 +/- 1% at the end (P < 0.001). This was not due to a larger increase in [Ca2+](i) induced by the interpolated twitch during fatigue but rather to the fact that the force-[Ca2+](i) relationship is sigmoidal and fibres entered a steeper part of the relationship during fatigue. In another set of experiments, we observed that repeated tetani evoked at 150 Hz resulted in more rapid fatigue development than at 70 Hz and there was a decrease in force ('sag') during contractions, which was not observed at 70 Hz. In conclusion, the extent of central fatigue is difficult to assess and it may be overestimated when using the twitch interpolation technique.

  17. A dynamical model of muscle activation, fatigue, and recovery.

    PubMed Central

    Liu, Jing Z; Brown, Robert W; Yue, Guang H

    2002-01-01

    A dynamical model is presented as a framework for muscle activation, fatigue, and recovery. By describing the effects of muscle fatigue and recovery in terms of two phenomenological parameters (F, R), we develop a set of dynamical equations to describe the behavior of muscles as a group of motor units activated by voluntary effort. This model provides a macroscopic view for understanding biophysical mechanisms of voluntary drive, fatigue effect, and recovery in stimulating, limiting, and modulating the force output from muscles. The model is investigated under the condition in which brain effort is assumed to be constant. Experimental validation of the model is performed by fitting force data measured from healthy human subjects during a 3-min sustained maximal voluntary handgrip contraction. The experimental results confirm a theoretical inference from the model regarding the possibility of maximal muscle force production, and suggest that only 97% of the true maximal force can be reached under maximal voluntary effort, assuming that all motor units can be recruited voluntarily. The effects of different motor unit types, time-dependent brain effort, sources of artifacts, and other factors that could affect the model are discussed. The applications of the model are also discussed. PMID:11964225

  18. Changes in motor cortical excitability during human muscle fatigue.

    PubMed Central

    Taylor, J L; Butler, J E; Allen, G M; Gandevia, S C

    1996-01-01

    1. The excitability of the motor cortex was investigated during fatiguing con of the elbow flexors in human subjects. During sustained contractions at 30 and 1 voluntary force (MVC), the short-latency electromyographic responses (EMG) evoke brachii and brachioradialis by transcranial magnetic stimulation increased in si EMG in the elbow flexors following the evoked muscle potential (silent period), duration during a sustained MVC but not during 30% MVCs nor during a sustained M muscle (adductor pollicis). 2. When the blood supply to brachioradialis was blocked with sphygmomanometer cuff sustained MVC, the changes in EMG responses to transcranial stimulation rapidly control values, This suggests that changes in these responses during fatigue wer small-diameter muscle afferents. 3. Tendon vibration during sustained MVCs indicated that the changes in the resp cortial stimulation were not mediated by reduced muscle spindle inputs. 4. Muscle action potentials evoked in brachioradialis by electrical stimulation cervicomedullary junction did not increase in size during sustained MVCs. Thus, cortically evoked responses during sustained MVCs reflects a change in cortical Although the silent period following cervicomedullary stimulation lengthened, it substantially shorter than the cortically evoked silent period. 5. The altered EMG responses to transcranial stimulation during fatigue suggest exitation and increased inhibition in the motor cortex. As these changes were un manipulation of afferent input they presumably result from intrinsic cortical pr altered voluntary drive to the motor cortex. Images Figure 1 PMID:8821148

  19. Effects of Acute Fatigue of the Hip Flexor Muscles on Hamstring Muscle Extensibility

    PubMed Central

    Arrabal-Campos, Francisco M.

    2016-01-01

    Abstract The purpose of the present study was to evaluate the influence of acute fatigue of the hip flexor muscles on scores attained in tests frequently used in literature to measure hamstring muscle extensibility, namely the passive straight leg raise (PSLR), active straight leg raise (ASLR), passive knee extension (PKE), active knee extension (AKE), sit-and-reach (SR) and toe-touch (TT) tests. A total of seventy-five healthy and recreationally active adults voluntarily participated in this study. To reach fatigue, the participants actively lifted their legs alternately as many times as possible. In the passive tests, the results were 7.10 ± 5.21° and 5.68 ± 4.54° higher (p < 0.01) for PSLR and PKE tests, respectively, after acute fatigue. However, in the ASLR test, the results were lower post-fatigue than pre-fatigue (mean difference = -5.30° ± 9.51°; p < 0.01). The AKE, SR and TT tests did not show significant differences between pre- and post-fatigue (p > 0.05). Moderate (r = 0.40) to high (r = 0.97) correlation coefficients were found, which were statistically significant among all the measured flexibility tests both pre- and post-fatigue. In conclusion, the active implication of the hip flexor muscles until reaching fatigue had acute influences on the results of the PSLR, PKE and ASLR tests, but not on the results of the AKE, SR and TT tests. It is recommended to use the AKE test to assess hamstring muscle extensibility in situations where athletes show fatigue in their hip flexor muscles. PMID:28149407

  20. Assessment of Musculoskeletal Strength and Levels of Fatigue during Different Phases of Menstrual Cycle in Young Adults.

    PubMed

    Pallavi, L C; D Souza, Urban John; Shivaprakash, G

    2017-02-01

    Some of the physiological factors and athletic performance might show variation along the phases of menstrual cycle. The alterations seen in these physiological parameters of various systems relating to oscillations in hormonal levels do affect the autonomic nervous system and metabolic functions. Former studies heave inconclusively about the influence of hormones on exercise performance, predominantly muscle strength and rate of fatigue during different phases of the menstrual cycle. Studies regarding influence of these variations during bleeding phase were not done. To evaluate the muscle strength variations and also the rate of fatigue during various phases of the menstrual cycle in young adults. This was a prospective study conducted among 100 healthy adult female volunteers aged 18-24 years, with normal regular menstrual cycles persistent between 26- 32 days (average of 28 days), for a minimum of last 6 months. Muscle strength was assessed by calculating the work done and fatigue rate using Mosso's ergograph and by handgrip dynamometer strength. Each subject was evaluated consecutively for two menstrual cycles in all three phases which were classified as Phase 1- Menstrual phase, Phase 2- Follicular phase and Phase 3- Luteal phase. The data obtained was analysed by statistical tool One-way ANOVA followed by a post-hoc Tukeys test. A p-value of ≤ 0.05 was considered significant. The amount of work done and handgrip strength was significantly higher in phase 2 (p<0.001) and relatively reduced in phase 1 and 3 (p<0.001) of menstrual cycle. In terms of fatigue rate percentage, phase 2 showed significantly lesser values (p<0.001) as compared to phase 1 and 3 of menstrual cycle. We conclude that the cyclical variation in endogenous reproductive hormones increases the muscle strength in follicular phase of the menstrual cycle. Thus provide support for the influence of these hormones in regulation of these parameters in the premenopausal age group.

  1. Assessment of Musculoskeletal Strength and Levels of Fatigue during Different Phases of Menstrual Cycle in Young Adults

    PubMed Central

    D Souza, Urban John; Shivaprakash, G

    2017-01-01

    Introduction Some of the physiological factors and athletic performance might show variation along the phases of menstrual cycle. The alterations seen in these physiological parameters of various systems relating to oscillations in hormonal levels do affect the autonomic nervous system and metabolic functions. Former studies heave inconclusively about the influence of hormones on exercise performance, predominantly muscle strength and rate of fatigue during different phases of the menstrual cycle. Studies regarding influence of these variations during bleeding phase were not done. Aim To evaluate the muscle strength variations and also the rate of fatigue during various phases of the menstrual cycle in young adults. Materials and Methods This was a prospective study conducted among 100 healthy adult female volunteers aged 18-24 years, with normal regular menstrual cycles persistent between 26- 32 days (average of 28 days), for a minimum of last 6 months. Muscle strength was assessed by calculating the work done and fatigue rate using Mosso’s ergograph and by handgrip dynamometer strength. Each subject was evaluated consecutively for two menstrual cycles in all three phases which were classified as Phase 1- Menstrual phase, Phase 2- Follicular phase and Phase 3- Luteal phase. The data obtained was analysed by statistical tool One-way ANOVA followed by a post-hoc Tukeys test. A p-value of ≤ 0.05 was considered significant. Results The amount of work done and handgrip strength was significantly higher in phase 2 (p<0.001) and relatively reduced in phase 1 and 3 (p<0.001) of menstrual cycle. In terms of fatigue rate percentage, phase 2 showed significantly lesser values (p<0.001) as compared to phase 1 and 3 of menstrual cycle. Conclusion We conclude that the cyclical variation in endogenous reproductive hormones increases the muscle strength in follicular phase of the menstrual cycle. Thus provide support for the influence of these hormones in regulation of these

  2. An EVA Suit Fatigue, Strength, and Reach Model

    NASA Technical Reports Server (NTRS)

    Maida, James C.

    1999-01-01

    The number of Extra-Vehicular Activities (EVAs) performed will increase dramatically with the upcoming Space Station assembly missions. It is estimated that up to 900 EVA hours may be required to assemble the Space Station with an additional 200 hours per year for maintenance requirements. Efficient modeling tools will be essential to assist in planning these EVAS. Important components include strength and fatigue parameters, multi-body dynamics and kinematics. This project is focused on building a model of the EVA crew member encompassing all these capabilities. Phase 1, which is currently underway, involves collecting EMU suited and unsuited fatigue, strength and range of motion data, for all major joints of the body. Phase 2 involves processing the data for model input, formulating comparisons between the EMU suits and deriving generalized relationships between suited and unsuited data. Phase 3 will be formulation of a multi-body dynamics model of the EMU capable of predicting mass handling properties and integration of empirical data into the model. Phase 4 will be validation of the model with collected EMU data from the Neutral Buoyancy Laboratory at NASA/JSC. Engineers and designers will use tie EVA suit database to better understand the capabilities of the suited individuals. This knowledge will lead to better design of tools and planned operations. Mission planners can use the modeling system and view the animations and the visualizations of the various parameters, such as overall fatigue, motion, timelines, reach, and strength to streamline the timing, duration, task arrangement, personnel and overall efficiency of the EVA tasks. Suit designers can use quantifiable data at common biomechanical structure points to better analyze and compare suit performance.

  3. Effects of Physical Activity and Inactivity on Muscle Fatigue

    PubMed Central

    Bogdanis, Gregory C.

    2012-01-01

    The aim of this review was to examine the mechanisms by which physical activity and inactivity modify muscle fatigue. It is well known that acute or chronic increases in physical activity result in structural, metabolic, hormonal, neural, and molecular adaptations that increase the level of force or power that can be sustained by a muscle. These adaptations depend on the type, intensity, and volume of the exercise stimulus, but recent studies have highlighted the role of high intensity, short-duration exercise as a time-efficient method to achieve both anaerobic and aerobic/endurance type adaptations. The factors that determine the fatigue profile of a muscle during intense exercise include muscle fiber composition, neuromuscular characteristics, high energy metabolite stores, buffering capacity, ionic regulation, capillarization, and mitochondrial density. Muscle fiber-type transformation during exercise training is usually toward the intermediate type IIA at the expense of both type I and IIx myosin heavy-chain isoforms. High-intensity training results in increases of both glycolytic and oxidative enzymes, muscle capillarization, improved phosphocreatine resynthesis and regulation of K+, H+, and lactate ions. Decreases of the habitual activity level due to injury or sedentary lifestyle result in partial or even compete reversal of the adaptations due to previous training, manifested by reductions in fiber cross-sectional area, decreased oxidative capacity, and capillarization. Complete immobilization due to injury results in markedly decreased force output and fatigue resistance. Muscle unloading reduces electromyographic activity and causes muscle atrophy and significant decreases in capillarization and oxidative enzymes activity. The last part of the review discusses the beneficial effects of intermittent high-intensity exercise training in patients with different health conditions to demonstrate the powerful effect of exercise on health and well being. PMID

  4. The multiple roles of phosphate in muscle fatigue

    PubMed Central

    Allen, David G.; Trajanovska, Sofie

    2012-01-01

    Muscle fatigue is the decline in performance of muscles observed during periods of intense activity. ATP consumption exceeds production during intense activity and there are multiple changes in intracellular metabolites which may contribute to the changes in crossbridge activity. It is also well-established that a reduction in activation, either through action potential changes or reduction in Ca2+ release from the sarcoplasmic reticulum (SR), makes an additional contribution to fatigue. In this review we focus on the role of intracellular inorganic phosphate (Pi) whose concentration can increase rapidly from around 5–30 mM during intense fatigue. Studies from skinned muscle fibers show that these changes substantially impair myofibrillar performance although the effects are strongly temperature dependent. Increased Pi can also cause reduced Ca2+ release from the SR and may therefore contribute to the reduced activation. In a recent study, we have measured both Pi and Ca2+ release in a blood-perfused mammalian preparation and the results from this preparation allows us to test the extent to which the combined effects of Pi and Ca2+ changes may contribute to fatigue. PMID:23248600

  5. Importance and challenges of measuring intrinsic foot muscle strength

    PubMed Central

    2012-01-01

    Background Intrinsic foot muscle weakness has been implicated in a range of foot deformities and disorders. However, to establish a relationship between intrinsic muscle weakness and foot pathology, an objective measure of intrinsic muscle strength is needed. The aim of this review was to provide an overview of the anatomy and role of intrinsic foot muscles, implications of intrinsic weakness and evaluate the different methods used to measure intrinsic foot muscle strength. Method Literature was sourced from database searches of MEDLINE, PubMed, SCOPUS, Cochrane Library, PEDro and CINAHL up to June 2012. Results There is no widely accepted method of measuring intrinsic foot muscle strength. Methods to estimate toe flexor muscle strength include the paper grip test, plantar pressure, toe dynamometry, and the intrinsic positive test. Hand-held dynamometry has excellent interrater and intrarater reliability and limits toe curling, which is an action hypothesised to activate extrinsic toe flexor muscles. However, it is unclear whether any method can actually isolate intrinsic muscle strength. Also most methods measure only toe flexor strength and other actions such as toe extension and abduction have not been adequately assessed. Indirect methods to investigate intrinsic muscle structure and performance include CT, ultrasonography, MRI, EMG, and muscle biopsy. Indirect methods often discriminate between intrinsic and extrinsic muscles, but lack the ability to measure muscle force. Conclusions There are many challenges to accurately measure intrinsic muscle strength in isolation. Most studies have measured toe flexor strength as a surrogate measure of intrinsic muscle strength. Hand-held dynamometry appears to be a promising method of estimating intrinsic muscle strength. However, the contribution of extrinsic muscles cannot be excluded from toe flexor strength measurement. Future research should clarify the relative contribution of intrinsic and extrinsic muscles

  6. Acute fatigue impairs neuromuscular activity of anterior cruciate ligament-agonist muscles in female team handball players.

    PubMed

    Zebis, M K; Bencke, J; Andersen, L L; Alkjaer, T; Suetta, C; Mortensen, P; Kjaer, M; Aagaard, P

    2011-12-01

    In sports, like team handball, fatigue has been associated with an increased risk of anterior cruciate ligament (ACL) injury. While effects of fatigue on muscle function are commonly assessed during maximal isometric voluntary contraction (MVC), such measurements may not relate to the muscle function during match play. The purpose of this study was to investigate the effect of muscle fatigue induced by a simulated handball match on neuromuscular strategy during a functional sidecutting movement, associated with the incidence of ACL injury. Fourteen female team handball players were tested for neuromuscular activity [electromyography (EMG)] during a sidecutting maneuver on a force plate, pre and post a simulated handball match. MVC was obtained during maximal isometric quadriceps and hamstring contraction. The simulated handball match consisted of exercises mimicking handball match activity. Whereas the simulated handball match induced a decrease in MVC strength for both the quadriceps and hamstring muscles (P<0.05), a selective decrease in hamstring neuromuscular activity was seen during sidecutting (P<0.05). This study shows impaired ACL-agonist muscle (i.e. hamstring) activity during sidecutting in response to acute fatigue induced by handball match play. Thus, screening procedures should involve functional movements to reveal specific fatigue-induced deficits in ACL-agonist muscle activation during high-risk phases of match play.

  7. 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.

  8. Is activation of the back muscles impaired by creep or muscle fatigue?

    PubMed

    Sánchez-Zuriaga, Daniel; Adams, Michael A; Dolan, Patricia

    2010-03-01

    Intervention study on healthy human subjects. To determine whether reflex activation of the back muscles is influenced by muscle fatigue or soft tissue creep in the spine. Reflex contraction of the back muscles normally acts to limit spinal flexion, and hence protect the underlying spine from injury. However, repeated flexion allows bending moments on the spine to increase. Impaired reflexes as a result of fatigue or soft tissue creep may be contributing factors. A total of 15 healthy volunteers (8 females/7 males aged 23-55 years) underwent 2 interventions, on separate days: (a) sitting flexed for 1 hour to induce creep and (b) performing the Biering-Sorensen test to induce back muscle fatigue. Before and after each intervention, reflex activation of the erector spinae in response to sudden trunk flexion (initiated by a Kin-Com dynamometer) was monitored bilaterally at T10 and L3 using surface electromyography (EMG) electrodes. These recordings indicated the onset latency of reflex activation, the peak EMG, and time to peak, at each site. Measurements before and after each intervention and between muscle sites were compared using a 2-way repeated measures Analysis of Variance. Spinal creep was confirmed by an increase in maximum flexion of 2.3 degrees +/- 2.5 degrees (P = 0.003), and fatigue by a significant fall in median frequency at one or more sites. Following creep, onset latency increased from 60 +/- 12 milliseconds to 96 +/- 26 milliseconds (P < 0.001) but there was no change in peak EMG or time to peak EMG. Differences between sites (P = 0.004) indicated greater latencies in lumbar compared to thoracic regions, especially after creep. Muscle fatigue had no significant effects on any of the measured parameters. Prolonged spinal flexion can impair sensorimotor control mechanisms and reduce back muscle protection of the underlying spine. The effect is due to time-dependent "creep" in soft tissues rather than muscle fatigue.

  9. NDE detectability of fatigue type cracks in high strength alloys

    NASA Technical Reports Server (NTRS)

    Christner, B. K.; Rummel, W. D.

    1983-01-01

    Specimens suitable for investigating the reliability of production nondestructive evaluation (NDE) to detect tightly closed fatigue cracks in high strength alloys representative of those materials used in spacecraft engine/booster construction were produced. Inconel 718 was selected as representative of nickel base alloys and Haynes 188 was selected as representative of cobalt base alloys used in this application. Cleaning procedures were developed to insure the reusability of the test specimens and a flaw detection reliability assessment of the fluorescent penetrant inspection method was performed using the test specimens produced to characterize their use for future reliability assessments and to provide additional NDE flaw detection reliability data for high strength alloys. The statistical analysis of the fluorescent penetrant inspection data was performed to determine the detection reliabilities for each inspection at a 90% probability/95% confidence level.

  10. The effect of yield strength and ductility to fatigue damage

    NASA Technical Reports Server (NTRS)

    Yeh, H. Y.

    1973-01-01

    The cumulative damage of aluminium alloys with different yield strength and various ductility due to seismic loads was studied. The responses of an idealized beam with a centered mass at one end and fixed at the other end to El Centro's and Taft's earthquakes are computed by assuming that the alloys are perfectly elastoplastic materials and by using numerical technique. Consequently, the corresponding residual plastic strain can be obtained from the stress-strain relationship. The revised Palmgren-Miner cumulative damage theorem is utilized to calculate the fatigue damage. The numerical results show that in certain cases, the high ductility materials are more resistant to seismic loads than the high yield strength materials. The results also show that if a structure collapse during the earthquake, the collapse always occurs in the very early stage.

  11. Muscle fatigue in the temporal and masseter muscles in patients with temporomandibular dysfunction.

    PubMed

    Woźniak, Krzysztof; Lipski, Mariusz; Lichota, Damian; Szyszka-Sommerfeld, Liliana

    2015-01-01

    The aim of this study is to evaluate muscle fatigue in the temporal and masseter muscles in patients with temporomandibular dysfunction (TMD). Two hundred volunteers aged 19.3 to 27.8 years (mean 21.50, SD 0.97) participated in this study. Electromyographical (EMG) recordings were performed using a DAB-Bluetooth Instrument (Zebris Medical GmbH, Germany). Muscle fatigue was evaluated on the basis of a maximum effort test. The test was performed during a 10-second maximum isometric contraction (MVC) of the jaws. An analysis of changes in the mean power frequency of the two pairs of temporal and masseter muscles (MPF%) revealed significant differences in the groups of patients with varying degrees of temporomandibular disorders according to Di (P < 0.0000). The study showed an increase in the muscle fatigue of the temporal and masseter muscles correlated with the intensity of temporomandibular dysfunction symptoms in patients. The use of surface electromyography in assessing muscle fatigue is an excellent diagnostic tool for identifying patients with temporomandibular dysfunction.

  12. Muscle Fatigue in the Temporal and Masseter Muscles in Patients with Temporomandibular Dysfunction

    PubMed Central

    Woźniak, Krzysztof; Lipski, Mariusz; Lichota, Damian

    2015-01-01

    The aim of this study is to evaluate muscle fatigue in the temporal and masseter muscles in patients with temporomandibular dysfunction (TMD). Two hundred volunteers aged 19.3 to 27.8 years (mean 21.50, SD 0.97) participated in this study. Electromyographical (EMG) recordings were performed using a DAB-Bluetooth Instrument (Zebris Medical GmbH, Germany). Muscle fatigue was evaluated on the basis of a maximum effort test. The test was performed during a 10-second maximum isometric contraction (MVC) of the jaws. An analysis of changes in the mean power frequency of the two pairs of temporal and masseter muscles (MPF%) revealed significant differences in the groups of patients with varying degrees of temporomandibular disorders according to Di (P < 0.0000). The study showed an increase in the muscle fatigue of the temporal and masseter muscles correlated with the intensity of temporomandibular dysfunction symptoms in patients. The use of surface electromyography in assessing muscle fatigue is an excellent diagnostic tool for identifying patients with temporomandibular dysfunction. PMID:25883949

  13. ZERODUR®: new stress corrosion data improve strength fatigue prediction

    NASA Astrophysics Data System (ADS)

    Hartmann, Peter; Kleer, Günter; Rist, Tobias

    2015-09-01

    The extremely low thermal expansion glass ceramic ZERODUR® finds more and more applications as sophisticated light weight structures with thin ribs or as thin shells. Quite often they will be subject to higher mechanical loads such as rocket launches or modulating wobbling vibrations. Designing such structures requires calculation methods and data taking into account their long term fatigue. With brittle materials fatigue is not only given by the material itself but to a high extent also by its surface condition and the environmental media especially humidity. This work extends the latest data and information gathered on the bending strength of ZERODUR® with new results concerning its long term behavior under tensile stress. The parameter needed for prediction calculations which combines the influences of time and environmental media is the stress corrosion constant n. Results of the past differ significantly from each other. In order to obtain consistent data the stress corrosion constant has been measured with the method comparing the breakage statistical distributions at different stress increase rates. For better significance the stress increase rate was varied over four orders of magnitude from 0.004 MPa/s to 40 MPa/s. Experiments were performed under normal humidity for long term earth bound applications and under nitrogen atmosphere as equivalent to dry environment occurring for example with telescopes in deserts and also equivalent to vacuum for space applications. As shown earlier the bending strength of diamond ground surfaces of ZERODUR® can be represented with a three parameter Weibull distribution. Predictions on the long term strength change of ZERODUR® structures under tensile stress are possible with reduced uncertainty if Weibull threshold strength values are considered and more reliable stress corrosion constant data are applied.

  14. Muscle Activity Adaptations to Spinal Tissue Creep in the Presence of Muscle Fatigue

    PubMed Central

    Nougarou, François

    2016-01-01

    Aim The aim of this study was to identify adaptations in muscle activity distribution to spinal tissue creep in presence of muscle fatigue. Methods Twenty-three healthy participants performed a fatigue task before and after 30 minutes of passive spinal tissue deformation in flexion. Right and left erector spinae activity was recorded using large-arrays surface electromyography (EMG). To characterize muscle activity distribution, dispersion was used. During the fatigue task, EMG amplitude root mean square (RMS), median frequency and dispersion in x- and y-axis were compared before and after spinal creep. Results Important fatigue-related changes in EMG median frequency were observed during muscle fatigue. Median frequency values showed a significant main creep effect, with lower median frequency values on the left side under the creep condition (p≤0.0001). A significant main creep effect on RMS values was also observed as RMS values were higher after creep deformation on the right side (p = 0.014); a similar tendency, although not significant, was observed on the left side (p = 0.06). A significant creep effects for x-axis dispersion values was observed, with higher dispersion values following the deformation protocol on the left side (p≤0.001). Regarding y-axis dispersion values, a significant creep x fatigue interaction effect was observed on the left side (p = 0.016); a similar tendency, although not significant, was observed on the right side (p = 0.08). Conclusion Combined muscle fatigue and creep deformation of spinal tissues led to changes in muscle activity amplitude, frequency domain and distribution. PMID:26866911

  15. Muscle Activity Adaptations to Spinal Tissue Creep in the Presence of Muscle Fatigue.

    PubMed

    Abboud, Jacques; Nougarou, François; Descarreaux, Martin

    2016-01-01

    The aim of this study was to identify adaptations in muscle activity distribution to spinal tissue creep in presence of muscle fatigue. Twenty-three healthy participants performed a fatigue task before and after 30 minutes of passive spinal tissue deformation in flexion. Right and left erector spinae activity was recorded using large-arrays surface electromyography (EMG). To characterize muscle activity distribution, dispersion was used. During the fatigue task, EMG amplitude root mean square (RMS), median frequency and dispersion in x- and y-axis were compared before and after spinal creep. Important fatigue-related changes in EMG median frequency were observed during muscle fatigue. Median frequency values showed a significant main creep effect, with lower median frequency values on the left side under the creep condition (p≤0.0001). A significant main creep effect on RMS values was also observed as RMS values were higher after creep deformation on the right side (p = 0.014); a similar tendency, although not significant, was observed on the left side (p = 0.06). A significant creep effects for x-axis dispersion values was observed, with higher dispersion values following the deformation protocol on the left side (p≤0.001). Regarding y-axis dispersion values, a significant creep x fatigue interaction effect was observed on the left side (p = 0.016); a similar tendency, although not significant, was observed on the right side (p = 0.08). Combined muscle fatigue and creep deformation of spinal tissues led to changes in muscle activity amplitude, frequency domain and distribution.

  16. Estimation of muscle fatigue by ratio of mean frequency to average rectified value from surface electromyography.

    PubMed

    Fernando, Jeffry Bonar; Yoshioka, Mototaka; Ozawa, Jun

    2016-08-01

    A new method to estimate muscle fatigue quantitatively from surface electromyography (EMG) is proposed. The ratio of mean frequency (MNF) to average rectified value (ARV) is used as the index of muscle fatigue, and muscle fatigue is detected when MNF/ARV falls below a pre-determined or pre-calculated baseline. MNF/ARV gives larger distinction between fatigued muscle and non-fatigued muscle. Experiment results show the effectiveness of our method in estimating muscle fatigue more correctly compared to conventional methods. An early evaluation based on the initial value of MNF/ARV and the subjective time when the subjects start feeling the fatigue also indicates the possibility of calculating baseline from the initial value of MNF/ARV.

  17. Muscle fatigue in frog semitendinosus: alterations in contractile function

    NASA Technical Reports Server (NTRS)

    Thompson, L. V.; Balog, E. M.; Riley, D. A.; Fitts, R. H.

    1992-01-01

    The purpose of this study was to characterize the contractile properties of the frog semitendinosus (ST) muscle before and during recovery from fatigue, to relate the observed functional changes to alterations in specific steps in the crossbridge model of muscle contraction, and to determine how fatigue affects the force-frequency relationship. The frog ST (22 degrees C) was fatigued by direct electrical stimulation with 100-ms 150-Hz trains at 1/s for 5 min. The fatigue protocol reduced peak twitch (Pt) and tetanic (Po) force to 32 and 8.5% of initial force, respectively. The decline in Pt was less than Po, in part due to a prolongation in the isometric contraction time (CT), which increased to 300% of the initial value. The isometric twitch duration was greatly prolonged as reflected by the lengthened CT and the 800% increase in the one-half relaxation time (1/2RT). Both Pt and Po showed a biphasic recovery, a rapid initial phase (2 min) followed by a slower (40 min) return to the prefatigue force. CT and 1/2RT also recovered in two phases, returning to 160 and 265% of control in the first 5 min. CT returned to the prefatigue value between 35 and 40 min, whereas even at 60 min 1/2RT was 133% of control. The maximal velocity of shortening, determined by the slack test, was significantly reduced [from 6.7 +/- 0.5 to 2.5 +/- 0.4 optimal muscle length/s] at fatigue. The force-frequency relationship was shifted to the left, so that optimal frequency for generating Po was reduced.(ABSTRACT TRUNCATED AT 250 WORDS).

  18. Correlation among proprioception, muscle strength, and balance.

    PubMed

    Wang, Huihui; Ji, Zhongqiu; Jiang, Guiping; Liu, Weitong; Jiao, Xibian

    2016-12-01

    [Purpose] To study the correlation among proprioception, muscle strength, and balance. [Subjects and Methods] A balance testing system (Biodex Balance System, BBS) and an isokinetic testing system (Biodex System 4, BS4) were used to test related indexes in 24 healthy young females. [Results] With the knee joint at 15 degree flexion, proprioception was significantly correlated with Limits of Stability-Time values, and was highly significantly correlated with Limits of Stability-Overall and Athlete Single Leg Medial/Lateral values. The sense of force was significantly correlated with Limits of Stability-Overall and Athlete Single Leg-Overall values. Quadriceps strength was significantly associated with Limits of Stability-Overall, Athlete Single Leg Medial/Lateral, and Athlete Double Leg-Overall values. The ratio of Quadriceps to Hamstring strength was significantly correlated with Athlete Single Leg Medial/Lateral, and Athlete Single Leg-Overall values. With the knee joint at 45°, proprioception was highly significantly correlated with dynamic balance, and was significantly correlated with double foot support under static balance; force sense had a high correlation with Limits of Stability-Overall, but no correlation with other indexes. Quadriceps strength had a significant correlation with dynamic and static balance; the ratio of Quadriceps/Hamstring had a highly significant correlation with Limits of Stability-Overall, Athlete Single Leg-Anterior/Posterior and Athlete Single Leg-Overall. [Conclusion] At different knee angles, the correlation differs among proprioception, force sense, quadriceps strength, the Quadriceps/Hamstring ratio, and balance.

  19. Probabilistic Material Strength Degradation Model for Inconel 718 Components Subjected to High Temperature, Mechanical Fatigue, Creep and Thermal Fatigue Effects

    NASA Technical Reports Server (NTRS)

    Bast, Callie Corinne Scheidt

    1994-01-01

    This thesis presents the on-going development of methodology for a probabilistic material strength degradation model. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes four effects that typically reduce lifetime strength: high temperature, mechanical fatigue, creep, and thermal fatigue. Statistical analysis was conducted on experimental Inconel 718 data obtained from the open literature. This analysis provided regression parameters for use as the model's empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for four variables, namely, high temperature, mechanical fatigue, creep, and thermal fatigue. Methodology to estimate standard deviations of these material constants for input into the probabilistic material strength model was developed. Using the current version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of mechanical fatigue, creep, and thermal fatigue was performed. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing a combination of mechanical fatigue and high temperature effects by model to the combination by experiment were conducted. Thus, for Inconel 718, the basic model assumption of independence between effects was evaluated. Results from this limited verification study strongly supported this assumption.

  20. The effects of unilateral muscle fatigue on bilateral physiological tremor.

    PubMed

    Morrison, S; Kavanagh, J; Obst, S J; Irwin, J; Haseler, L J

    2005-12-01

    The aim of this study was to examine the post-exercise effects of fatiguing the wrist extensor muscles of a single arm on postural tremor and muscle activity in both arms. Previous research has shown that, for neurologically normal subjects, the tremor seen within a single limb segment is uncorrelated to that seen contralaterally. However it has been speculated that some bilateral relation does exist, and that the nature of the relation may only become evident under conditions where the neuromuscular system is perturbed. To further investigate this potential bilateral relation, seven healthy subjects were required to adopt a bilateral postural pointing position after exercise-induced fatigue of the wrist extensor muscles of a single arm. Tremor from the forearm, hand and finger segments of each arm, surface EMG activity from extensor digitorum (ED) of each arm, and blood lactate data were collected prior to and after the exercise intervention. The main result was that fatiguing the distal muscles of one arm resulted in a bilateral increase in both the physiological tremor and ED activity. The change in tremor was confined to the index finger with no change in the tremor for the hand or forearm segments of either arm. While three peaks were seen in the frequency profile of the finger tremor, the effects of fatigue were confined to an increase in the peak power of the neurally generated 8-12 Hz tremor component. The contralateral increase in muscle activity was also reflected by a change in the frequency profile of the EMG output, with an increase in the peak power of both muscles following exercise of the wrist extensors of a single arm. The bilateral increases in physiological tremor and EMG activity of ED were only observed during the bilateral pointing task, with no changes in tremor or EMG activity seen for the non-exercised limb during the unilateral exercise protocol. The specificity of the resultant increases in the neurally generated 8-12 Hz component of

  1. Strength and physiological response to exercise in patients with chronic fatigue syndrome

    PubMed Central

    Fulcher, K.; White, P.

    2000-01-01

    OBJECTIVE—To measure strength, aerobic exercise capacity and efficiency, and functional incapacity in patients with chronic fatigue syndrome (CFS) who do not have a current psychiatric disorder.
METHODS—Sixty six patients with CFS without a current psychiatric disorder, 30 healthy but sedentary controls, and 15 patients with a current major depressive disorder were recruited into the study. Exercise capacity and efficiency were assessed by monitoring peak and submaximal oxygen uptake, heart rate, blood lactate, duration of exercise, and perceived exertion during a treadmill walking test. Strength was measured using twitch interpolated voluntary isometric quadriceps contractions. Symptomatic measures included physical and mental fatigue, mood, sleep, somatic amplification, and functional incapacity.
RESULTS—Compared with sedentary controls, patients with CFS were physically weaker, had a significantly reduced exercise capacity, and perceived greater effort during exercise, but were equally unfit. Compared with depressed controls, patients with CFS had significantly higher submaximal oxygen uptakes during exercise, were weaker, and perceived greater physical fatigue and incapacity. Multiple regression models suggested that exercise incapacity in CFS was related to quadriceps muscle weakness, increased cardiovascular response to exercise, and body mass index. The best model of the increased exercise capacity found after graded exercise therapy consisted of a reduction in submaximal heart rate response to exercise.
CONCLUSIONS—Patients with CFS were weaker than sedentary and depressed controls and as unfit as sedentary controls. Low exercise capacity in patients with CFS was related to quadriceps muscle weakness, low physical fitness, and a high body mass ratio. Improved physical fitness after treatment was associated with increased exercise capacity. These data imply that physical deconditioning helps to maintain physical disability in CFS and that a

  2. Effects of Quadriceps Muscle Fatigue on Stiff-Knee Gait in Patients with Hemiparesis

    PubMed Central

    Boudarham, Julien; Roche, Nicolas; Pradon, Didier; Delouf, Eric; Bensmail, Djamel; Zory, Raphael

    2014-01-01

    The relationship between neuromuscular fatigue and locomotion has never been investigated in hemiparetic patients despite the fact that, in the clinical context, patients report to be more spastic or stiffer after walking a long distance or after a rehabilitation session. The aim of this study was to evaluate the effects of quadriceps muscle fatigue on the biomechanical gait parameters of patients with a stiff-knee gait (SKG). Thirteen patients and eleven healthy controls performed one gait analysis before a protocol of isokinetic quadriceps fatigue and two after (immediately after and after 10 minutes of rest). Spatiotemporal parameters, sagittal knee and hip kinematics, rectus femoris (RF) and vastus lateralis (VL) kinematics and electromyographic (EMG) activity were analyzed. The results showed that quadriceps muscle weakness, produced by repetitive concentric contractions of the knee extensors, induced an improvement of spatiotemporal parameters for patients and healthy subjects. For the patient group, the increase in gait velocity and step length was associated with i) an increase of sagittal hip and knee flexion during the swing phase, ii) an increase of the maximal normalized length of the RF and VL and of the maximal VL lengthening velocity during the pre-swing and swing phases, and iii) a decrease in EMG activity of the RF muscle during the initial pre-swing phase and during the latter 2/3 of the initial swing phase. These results suggest that quadriceps fatigue did not alter the gait of patients with hemiparesis walking with a SKG and that neuromuscular fatigue may play the same functional role as an anti-spastic treatment such as botulinum toxin-A injection. Strength training of knee extensors, although commonly performed in rehabilitation, does not seem to be a priority to improve gait of these patients. PMID:24718087

  3. Muscle Coactivation Before and After the Impact Phase of Running Following Isokinetic Fatigue

    PubMed Central

    Kellis, Eleftherios; Zafeiridis, Andreas; Amiridis, Ioannis G.

    2011-01-01

    Abstract Context: The effects of fatigue on impact loading during running are unclear, with some authors reporting increased impact forces and others reporting decreased forces. Objective: To examine the effects of isokinetic fatigue on muscle cocontraction ratios about the knee and ankle during running. Design: Cross-sectional study. Setting: Neuromechanics laboratory. Patients or Other Participants: Female middle-distance runners (age  =  21.3 ± 1.93 years) with at least 5 years of training experience. Intervention(s): Participants ran on the treadmill at 3.61 m/s before and immediately after the fatigue protocol, which consisted of consecutive, concentric knee extension-flexion at 120°/s until they could no longer produce 30% of the maximum knee-extension moment achieved in the familiarization session for 3 consecutive repetitions. Main Outcome Measure(s): Electromyographic (EMG) amplitude of the vastus medialis (VM), biceps femoris (BF), gastrocnemius (GAS), and tibialis anterior (TA) was recorded using surface electrodes. Agonist∶antagonist EMG ratios for the knee (VM∶BF) and ankle (GAS∶TA) were calculated for the preactivation (PR), initial loading response (LR1), and late loading response (LR2) phases of running. Hip-, knee-, and ankle-joint angular displacements at initial foot contact were obtained from 3-dimensional kinematic tracings. Results: Fatigue did not alter the VM∶BF EMG ratio during the PR phase (P > .05), but it increased the ratio during the LR1 phase (P < .05). The GAS∶TA EMG ratio increased during the LR1 phase after fatigue (P < .05) but remained unchanged during the PR and LR2 phrases (P > .05). Conclusions: The increased agonist EMG activation, coupled with reduced antagonist EMG activation after impact, indicates that the acute decrease in muscle strength capacity of the knee extensors and flexors results in altered muscle-activation patterns about the knee and ankle before and after foot impact. PMID:21214346

  4. Effect of test frequency on fatigue strength of AZ31 alloy

    NASA Astrophysics Data System (ADS)

    Lu, G. J.; Koyanagi, Y.; Tsushida, M.; Kitahara, H.; Ando, S.

    2017-05-01

    Investigation of fatigue strength of extruded AZ31 magnesium alloy was performed by ultrasonic fatigue tests (test frequency about 19500Hz) and taken to compare with conventional tension-compression fatigue tests (20Hz). The fatigue life under ultrasonic loading exhibits longer than the conventional one. Effects of ultrasonic frequency on the S-N curve, crack initiation and growth behaviour of AZ31 alloy is discussed. This work would be useful for improving the ultrasonic fatigue test method to observe the fatigue behaviour in very high cycle regime.

  5. Lung Function, Respiratory Muscle Strength, and Thoracoabdominal Mobility in Women With Fibromyalgia Syndrome.

    PubMed

    Forti, Meire; Zamunér, Antonio R; Andrade, Carolina P; Silva, Ester

    2016-10-01

    Fibromyalgia syndrome (FMS) is associated with a variety of symptoms, such as fatigue and dyspnea, which may be related to changes in the respiratory system. The objective of this work was to evaluate pulmonary function, respiratory muscle strength, and thoracoabdominal mobility in women with FMS and its association with clinical manifestations. The study included 23 women with FMS and 23 healthy women (control group). Pulmonary function, respiratory muscle strength, and thoracoabdominal mobility were assessed in all participants. Clinical manifestations such as number of active tender points, pain, fatigue, well-being, and general pressure pain threshold and pressure pain threshold in regions involved in respiratory function were also assessed. For data analysis, the Mann-Whitney test and Spearman correlation coefficient were used. The FMS group showed lower values of maximum voluntary ventilation (P = .030), maximal inspiratory pressure (P = .003), and cirtometry at the axillary and xiphoid levels (P < .001 and P < .001, respectively) as well as higher cirtometry at the abdominal level (P = .005) compared with the control group. However, there was no significant difference between groups for maximum expiratory pressure. In predicted percentage, maximal inspiratory pressure showed significant positive correlation with axillary cirtometry (r = 0.41, P = .049) and negative correlation with the number of active tender points (r = -0.44, P = .031) and fatigue (r = -0.41, P = .049). Subjects with FMS had lower respiratory muscle endurance, inspiratory muscle strength, and thoracic mobility than healthy subjects. In addition, inspiratory muscle strength was associated with the number of active tender points, fatigue, and axillary mobility. Copyright © 2016 by Daedalus Enterprises.

  6. Retention force and fatigue strength of overdenture attachment systems.

    PubMed

    Botega, D M; Mesquita, M F; Henriques, G E P; Vaz, L G

    2004-09-01

    This study evaluated retention force and fatigue resistance of two overdenture attachment systems. Twenty samples (O-ring and Bar-Clip) from two manufacturers (Conexão Sistemas de Prótese and Lifecore Biomedical) were prepared and divided into four groups: (i) Conexão/O-ring; (ii) Conexão/Bar-Clip; (iii) Lifecore/O-ring and (iv) Lifecore/Bar-Clip, with five samples in each group. They were submitted to mechanical fatigue test using a servohydraulic machine performing 5500 cycles of insertion and removal (f=0.8 Hz), immersed in artificial saliva. Retention force values were obtained three times (0, 3000 and after 5500 cycles) simulating the clinical service, using a tensile strength at 1 mm min(-1) and load cell of 1 kN. Data were analysed with analysis of variance and Tukey's test at 5% level. Results showed that Conexão/Bar-Clip specimens had significantly higher retention values than Lifecore/Bar-Clip (44.61 and 18.44 N, respectively), Conexão/O-ring specimens had significantly lower values than Lifecore/O-ring (13.91 and 19.75 N, respectively). Conexão/Bar-Clip values were always significantly higher than those of Conexão/O-ring group (44.61 and 13.91 N, respectively). Lifecore (O-ring and Bar-Clip) presented similar values (19.75 and 18.44 N, respectively). The systems evaluated showed satisfactory retention force values, before and after fatigue testing. Conexão/Bar-Clip specimens presented the highest values. A 5-year simulation of insertion and removal did not decrease retention values or fracture components.

  7. The effect of inspiratory muscle fatigue on breathing pattern and ventilatory response to CO2.

    PubMed Central

    Mador, M J; Tobin, M J

    1992-01-01

    1. The effects of inducing inspiratory muscle fatigue on the subsequent breathing pattern were examined during resting unstimulated breathing and during CO2 rebreathing. In addition, we examined whether induction of inspiratory muscle fatigue alters CO2 responsiveness. 2. Global inspiratory muscle fatigue and diaphragmatic fatigue were achieved by having subjects breathe against an inspiratory resistive load while generating a predetermined fraction of either their maximal mouth pressure or maximal transdiaphragmatic pressure until they were unable to generate the target pressure. 3. Induction of inspiratory muscle fatigue had no effect on the subsequent breathing pattern during either unstimulated breathing or during CO2 rebreathing. 4. Following induction of inspiratory muscle fatigue, the slope of the ventilatory response to CO2 was significantly decreased from 18.8 +/- 3.3 during control to 13.8 +/- 2.1 l min-1 (% end-tidal CO2 concentration)-1 with fatigue (P < 0.02). PMID:1484352

  8. Decrease of muscle fiber conduction velocity correlates with strength loss after an endurance run.

    PubMed

    Boccia, Gennaro; Dardanello, Davide; Tarperi, Cantor; Rosso, Valeria; Festa, Luca; La Torre, Antonio; Pellegrini, Barbara; Schena, Federico; Rainoldi, Alberto

    2017-02-01

    Monitoring surface electromyographic (EMG) signals can provide useful insights for characterizing muscle fatigue, which is defined as an exercise-induced strength loss. This experiment investigated the muscle fiber conduction velocity (CV) changes induced by an endurance run. The day before and immediately after a half-marathon run (21.097 km) 11 amateur runners performed maximum voluntary contractions (MVCs) of knee extensor muscles. During the MVC, multichannel EMG was recorded from the vastus lateralis and EMG amplitude and CV were calculated. After the run, knee extensors showed a decreased strength (-13  ±  9%, p  =  0.001) together with a reduction in EMG amplitude (-13  ±  10%, p  =  0.003) and in CV (-6  ±  8%, p  =  0.032). Knee extensor strength loss positively correlated with vastus lateralis CV differences (r  =  0.76, p  =  0.006). Thus, the exercises-induced muscle fatigue was associated not only with a decrease in EMG amplitude, but also with a reduction in CV. This finding suggests that muscle fibers with higher CV (i.e. those with greater fiber size) were the most impaired during strength production after an endurance run.

  9. New Powder Metallurgical Approach to Achieve High Fatigue Strength in Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Cao, Fei; Ravi Chandran, K. S.; Kumar, Pankaj; Sun, Pei; Zak Fang, Z.; Koopman, Mark

    2016-05-01

    Recently, manufacturing of titanium by sintering and dehydrogenation of hydride powders has generated a great deal of interest. An overarching concern regarding powder metallurgy (PM) titanium is that critical mechanical properties, especially the high-cycle fatigue strength, are lower than those of wrought titanium alloys. It is demonstrated here that PM Ti-6Al-4V alloy with mechanical properties comparable (in fatigue strength) and exceeding (in tensile properties) those of wrought Ti-6Al-4V can be produced from titanium hydride powder, through the hydrogen sintering and phase transformation process. Tensile and fatigue behavior, as well as fatigue fracture mechanisms, have been investigated under three processing conditions. It is shown that a reduction in the size of extreme-sized pores by changing the hydride particle size distribution can lead to improved fatigue strength. Further densification by pneumatic isostatic forging leads to a fatigue strength of ~550 MPa, comparable to the best of PM Ti-6Al-4V alloys prepared by other methods and approaching the fatigue strengths of wrought Ti-6Al-4V alloys. The microstructural factors that limit fatigue strength in PM titanium have been investigated, and pathways to achieve greater fatigue strengths in PM Ti-6Al-4V alloys have been identified.

  10. Fracture strength of all-ceramic restorations after fatigue loading

    NASA Astrophysics Data System (ADS)

    Baladhandayutham, Balasudha

    Fracture strength of monolithic and bilayered LAVA and e. max lower molar crowns after load cycling was measured and compared. The study included three groups (n = 8) from LAVA zirconia and three groups from e. max lithium disilicate to compare influences of different layers, thicknesses and manufacturing techniques. Prefabricated anatomically designed crowns were cemented to dies made from Z 100 composite resin using Rely X Luting Plus resin modified glass ionomer cement. Cemented crowns were stored at 37° C for 24 hours then cyclic loaded to test fatigue properties. The crowns were loaded to 200,000 cycles at 25N at a rate of 40 cycles / minute to simulate oral function. Subsequently, fracture properties for each group were measured using an Instron Universal Testing machine. Microscopic evaluation of the surface of fatigued samples did not reveal micro-cracks at the end of 50,000 cycles but minor wear facets were observed at the site of contact from the steatite ball antagonist. Crowns from LAVA bilayered groups showed step by step fractures while crowns from all other groups fractured as a single event as observed by the high speed camera. Zirconia bilayered crowns showed the highest loads to fracture while lithium disilicate monolithic crowns showed the lowest, within the limitations of the study. The study also showed that monolithic zirconia crowns of 0.6mm thickness resulted in relatively high magnitude for forces at fracture.

  11. Mechanisms behind Estrogens’ Beneficial Effect on Muscle Strength in Females

    PubMed Central

    Lowe, Dawn A.; Baltgalvis, Kristen A.; Greising, Sarah M.

    2010-01-01

    Muscle weakness ensues when serum testosterone declines with age in men. Testosterone’s female counterpart, estrogen, has also been implicated in age-related strength loss but these results are less conclusive. Our working hypothesis is that estrogens do benefit muscle strength, and that the underlying mechanism involves estrogen receptors to improve muscle quality more so than quantity. PMID:20335737

  12. The effect of kinesiotape on dynamic balance following muscle fatigue in individuals with chronic ankle instability.

    PubMed

    Kodesh, Einat; Dar, Gali

    2015-01-01

    This study aimed to evaluate the effect of kinesiotape (KT) on dynamic stability following ankle muscle fatigue among individuals with chronic ankle instability (CAI). Twenty participants with CAI participated in the study. Participants were tested under three conditions: KT, non-elastic tape, and no tape pre- and post-fatigue of the ankle muscles. Ankle muscles fatigue was induced using an isokinetic apparatus, activity of the fibularis muscle was recorded using one-channel vibromyography (VMG), and dynamic balance and neuromuscular control were assessed using the Y-Balance Test. Following fatigue exercises, the VMG signal significantly decreased in all groups (p < 0.01), without differences between groups. No significant difference in dynamic balance test scores was found between the pre- and post-fatigue condition for each group and between groups. Our results demonstrate that KT had no significant effects on dynamic balance and muscle activity following ankle muscle fatigue among individuals with CAI.

  13. The effect of muscle fatigue on in vivo tibial strains.

    PubMed

    Milgrom, Charles; Radeva-Petrova, Denitsa R; Finestone, Aharon; Nyska, Meir; Mendelson, Stephen; Benjuya, Nisim; Simkin, Ariel; Burr, David

    2007-01-01

    Stress fracture is a common musculoskeletal problem affecting athletes and soldiers. Repetitive high bone strains and strain rates are considered to be its etiology. The strain level necessary to cause fatigue failure of bone ex vivo is higher than the strains recorded in humans during vigorous physical activity. We hypothesized that during fatiguing exercises, bone strains may increase and reach levels exceeding those measured in the non-fatigued state. To test this hypothesis, we measured in vivo tibial strains, the maximum gastrocnemius isokinetic torque and ground reaction forces in four subjects before and after two fatiguing levels of exercise: a 2km run and a 30km desert march. Strains were measured using strain-gauged staples inserted percutaneously in the medial aspect of their mid-tibial diaphysis. There was a decrease in the peak gastrocnemius isokinetic torque of all four subjects' post-march as compared to pre-run (p=0.0001), indicating the presence of gastrocnemius muscle fatigue. Tension strains increased 26% post-run (p=0.002, 95 % confidence interval (CI) and 29% post-march (p=0.0002, 95% CI) as compared to the pre-run phase. Tension strain rates increased 13% post-run (p=0.001, 95% CI) and 11% post-march (p=0.009, 95% CI) and the compression strain rates increased 9% post-run (p=0.0004, 95% CI) and 17% post-march (p=0.0001, 95% CI). The fatigue state increases bone strains well above those recorded in rested individuals and may be a major factor in the stress fracture etiology.

  14. Conducting High Cycle Fatigue Strength Step Tests on Gamma TiAl

    NASA Technical Reports Server (NTRS)

    Lerch, Brad; Draper, Sue; Pereira, J. Mike

    2002-01-01

    High cycle fatigue strength testing of gamma TiAl by the step test method is investigated. A design of experiments was implemented to determine if the coaxing effect occurred during testing. Since coaxing was not observed, step testing was deemed a suitable method to define the fatigue strength at 106 cycles.

  15. Correlation among proprioception, muscle strength, and balance

    PubMed Central

    Wang, Huihui; Ji, Zhongqiu; Jiang, Guiping; Liu, Weitong; Jiao, Xibian

    2016-01-01

    [Purpose] To study the correlation among proprioception, muscle strength, and balance. [Subjects and Methods] A balance testing system (Biodex Balance System, BBS) and an isokinetic testing system (Biodex System 4, BS4) were used to test related indexes in 24 healthy young females. [Results] With the knee joint at 15 degree flexion, proprioception was significantly correlated with Limits of Stability-Time values, and was highly significantly correlated with Limits of Stability-Overall and Athlete Single Leg Medial/Lateral values. The sense of force was significantly correlated with Limits of Stability-Overall and Athlete Single Leg-Overall values. Quadriceps strength was significantly associated with Limits of Stability-Overall, Athlete Single Leg Medial/Lateral, and Athlete Double Leg-Overall values. The ratio of Quadriceps to Hamstring strength was significantly correlated with Athlete Single Leg Medial/Lateral, and Athlete Single Leg-Overall values. With the knee joint at 45°, proprioception was highly significantly correlated with dynamic balance, and was significantly correlated with double foot support under static balance; force sense had a high correlation with Limits of Stability-Overall, but no correlation with other indexes. Quadriceps strength had a significant correlation with dynamic and static balance; the ratio of Quadriceps/Hamstring had a highly significant correlation with Limits of Stability-Overall, Athlete Single Leg-Anterior/Posterior and Athlete Single Leg-Overall. [Conclusion] At different knee angles, the correlation differs among proprioception, force sense, quadriceps strength, the Quadriceps/Hamstring ratio, and balance. PMID:28174475

  16. Autism Severity and Muscle Strength: A Correlation Analysis

    ERIC Educational Resources Information Center

    Kern, Janet K.; Geier, David A.; Adams, James B.; Troutman, Melissa R.; Davis, Georgia; King, Paul G.; Young, John L.; Geier, Mark R.

    2011-01-01

    The current study examined the relationship between muscle strength, as measured by hand grip strength, and autism severity, as measured by the Childhood Autism Rating Scale (CARS). Thirty-seven (37) children with a diagnosis of autism spectrum disorder (ASD) were evaluated using the CARS and then tested for hand muscle strength using a hand grip…

  17. Autism Severity and Muscle Strength: A Correlation Analysis

    ERIC Educational Resources Information Center

    Kern, Janet K.; Geier, David A.; Adams, James B.; Troutman, Melissa R.; Davis, Georgia; King, Paul G.; Young, John L.; Geier, Mark R.

    2011-01-01

    The current study examined the relationship between muscle strength, as measured by hand grip strength, and autism severity, as measured by the Childhood Autism Rating Scale (CARS). Thirty-seven (37) children with a diagnosis of autism spectrum disorder (ASD) were evaluated using the CARS and then tested for hand muscle strength using a hand grip…

  18. Fatigue in the masseter and temporalis muscles at constant load.

    PubMed

    Sforza, Chiarella; Zanotti, Gianfranco; Mantovani, Enrica; Ferrario, Virgilio F

    2007-01-01

    Fatigue is usually defined as the point at which a particular level of force can be no longer maintained. In the present study, surface EMG of the masseter and temporalis anterior muscles was measured in ten healthy young adults performing a unilateral molar (right side) clench. The subjects clenched on a bite force transducer at a fixed force level of 13 kg (127 N) as long as they could (endurance). The test ended when the subjects could no longer produce the required bite force. From the EMG recordings, the median power frequency was calculated at the beginning of the task (T0), after one minute of clenching (T1), and at the end of the task (T2, endurance time). For each subject and muscle, percentage decrements in the median power frequency were also computed at T1 and T2. Endurance time ranged between 79 and 470 s. Significant modifications in the median power frequency in both masseter muscles (right side, p=0.003; left side, p=0.02, analysis of variance) were found, with a significant difference for the median frequency at T2 (p<0.02 at post hoc test). The modifications in the temporalis muscles were not significant (p>0.05). Additionally, at T1, significant percentage decrements in the median power frequency were found for both right side muscles (p<0.05, paired Student's ). The left side muscles modifications (p>0.05) were not significant. A significant effect of side was found (p=0.007, analysis of variance), without effects of muscle and no muscle x side interaction. At T2, both masseter muscles and the right side temporalis had a significant modification in their median power frequency. Overall, the modifications were larger in the masseter than in the temporalis muscles (p=0.022, analysis of variance), without effects of side and no muscle x side interaction. In conclusion, a fixed submaximal muscular contraction provoked fatigue modifications in the EMG power spectra that were well comparable to those obtained in previous investigations using forces

  19. Fnip1 regulates skeletal muscle fiber type specification, fatigue resistance, and susceptibility to muscular dystrophy.

    PubMed

    Reyes, Nicholas L; Banks, Glen B; Tsang, Mark; Margineantu, Daciana; Gu, Haiwei; Djukovic, Danijel; Chan, Jacky; Torres, Michelle; Liggitt, H Denny; Hirenallur-S, Dinesh K; Hockenbery, David M; Raftery, Daniel; Iritani, Brian M

    2015-01-13

    Mammalian skeletal muscle is broadly characterized by the presence of two distinct categories of muscle fibers called type I "red" slow twitch and type II "white" fast twitch, which display marked differences in contraction strength, metabolic strategies, and susceptibility to fatigue. The relative representation of each fiber type can have major influences on susceptibility to obesity, diabetes, and muscular dystrophies. However, the molecular factors controlling fiber type specification remain incompletely defined. In this study, we describe the control of fiber type specification and susceptibility to metabolic disease by folliculin interacting protein-1 (Fnip1). Using Fnip1 null mice, we found that loss of Fnip1 increased the representation of type I fibers characterized by increased myoglobin, slow twitch markers [myosin heavy chain 7 (MyH7), succinate dehydrogenase, troponin I 1, troponin C1, troponin T1], capillary density, and mitochondria number. Cultured Fnip1-null muscle fibers had higher oxidative capacity, and isolated Fnip1-null skeletal muscles were more resistant to postcontraction fatigue relative to WT skeletal muscles. Biochemical analyses revealed increased activation of the metabolic sensor AMP kinase (AMPK), and increased expression of the AMPK-target and transcriptional coactivator PGC1α in Fnip1 null skeletal muscle. Genetic disruption of PGC1α rescued normal levels of type I fiber markers MyH7 and myoglobin in Fnip1-null mice. Remarkably, loss of Fnip1 profoundly mitigated muscle damage in a murine model of Duchenne muscular dystrophy. These results indicate that Fnip1 controls skeletal muscle fiber type specification and warrant further study to determine whether inhibition of Fnip1 has therapeutic potential in muscular dystrophy diseases.

  20. Fatigue Performance of Powder Metallurgy (PM) Ti-6Al-4V Alloy: A Critical Analysis of Current Fatigue Data and Metallurgical Approaches for Improving Fatigue Strength

    NASA Astrophysics Data System (ADS)

    Cao, Fei; Ravi Chandran, K. S.

    2016-03-01

    A comprehensive assessment of fatigue performance of powder metallurgy (PM) Ti-6Al-4V alloy, manufactured using various powder-based processing approaches to-date, is performed in this work. The focus is on PM processes that use either blended element (BE) or pre-alloyed (PA) powder as feedstock. Porosity and the microstructure condition have been found to be the two most dominant material variables that control the fatigue strength. The evaluation reveals that the fatigue performance of PM Ti-6Al-4V, in the as-sintered state, is far lower than that in the wrought condition. This is largely caused by residual porosity, even if it is present in small amounts, or, by the coarse lamellar colony microstructure. The fatigue strength is significantly improved by the closure of pores, and it approaches the levels of wrought Ti-6Al-4V alloys, after hot-isostatic-pressing (HIPing). Further thermo-mechanical and heat treatments lead to additional increases in fatigue strength-in one case, a high fatigue strength level, exceeding that of the mill-annealed condition, was achieved. The work identifies the powder, process and microstructure improvements that are necessary for achieving high fatigue strength in powder metallurgical Ti-6Al-4V alloys in order for them to effectively compete with wrought forms. The present findings, gathered from the traditional titanium powder metallurgy, are also directly applicable to additively manufactured titanium, because of the similarities in pores, defects, and microstructures between the two manufacturing processes.

  1. Muscle fatigue evaluation of astronaut upper limb based on sEMG and subjective assessment

    NASA Astrophysics Data System (ADS)

    Zu, Xiaoqi; Zhou, Qianxiang; Li, Yun

    2012-07-01

    All movements are driven by muscle contraction, and it is easy to cause muscle fatigue. Evaluation of muscle fatigue is a hot topic in the area of astronaut life support training and rehabilitation. If muscle gets into fatigue condition, it may reduce work efficiency and has an impact on psychological performance. Therefore it is necessary to develop an accurate and usable method on muscle fatigue evaluation of astronaut upper limb. In this study, we developed a method based on surface electromyography (sEMG) and subjective assessment (Borg scale) to evaluate local muscle fatigue. Fifteen healthy young male subjects participated in the experiment. They performed isometric muscle contractions of the upper limb. sEMG of the biceps brachii were recorded during the entire process of isotonic muscle contraction and Borg scales of muscle fatigue were collected in certain times. sEMG were divided into several parts, and then mean energy of each parts were calculated by the one-twelfth band octave method. Equations were derived based on the relationship between the mean energy of sEMG and Borg scale. The results showed that cubic curve could describe the degree of local muscle fatigue, and could be used to evaluate and monitor local muscle fatigue during the entire process.

  2. Fractal Dimension in Eeg Signals during Muscle Fatigue

    NASA Astrophysics Data System (ADS)

    Huang, Haibin; Yao, Bin; Yue, Guang; Brown, Robert; Jing, Liu

    2003-10-01

    Fractal dimension (FD) has been successfully used to characterize signals in the format of time series. In this study, we calculated FD of EEG signals recorded during human muscle fatigue as a measure of changes in the EEG signal complexity along fatigue. Subjects performed 200 intermittent handgrip contractions at 100contraction level. Each contraction lasted 2 s, followed by a 5-s rest. EEG data were recorded from the scalp along with handgrip force and muscle EMG signals. The FD computation was based on measurements of the length (Lk) of the signal at 6 different temporal resolutions (k = 1, 2, ¡­, 6). FD was determined from the relationship between Lk and k using the least square fit. The results showed that: (1) EEG fractal dimension associated with the motor performance was significantly higher than that during the rest period; (2) changes in the fractal dimension along the process of fatigue showed a significant correlation with the decline in force and EMG signals.

  3. Training effect and fatigue in polypyrrole-based artificial muscles.

    PubMed

    Kaneto, Keiichi; Suematsu, Hirotaka; Yamato, Kentaro

    2008-09-01

    Artificial muscles based on an electrochemomechanical strain (ECMS) in conducting polymers, namely polypyrrole (PPy) film, have been studied from viewpoints of training, fatigue and aging by repeat cycles under tensile loads. ECMS was approximately 2% in a saline solution, resulting from both insertion and exclusion of Na(+) with solvated water molecules as well in the film. Transient responses of ECMS and current induced by voltage stimuli were measured under tensile stresses up to 5 MPa to see the training effect, fatigue and aging of the film. At higher stresses the film showed larger creeping, which resulted from realignment or conformation change, slipping and breaking of polymer chains. After the experience of large stresses, the training effect in ECMS was appreciably observed as an increase of the strain. Without stress the conductivity of the film was stable (no fatigue) upon an electrochemical cycle; however, under high tensile stresses the conductivity decreased remarkably (fatigue and aging). It is to be noted that straightened polymer chains can be easily oxidized and degraded due to lower pi-electron energy. The conversion efficiency from electrical to mechanical energy in this system was found to be less than 0.03%.

  4. (-)-Epicatechin enhances fatigue resistance and oxidative capacity in mouse muscle.

    PubMed

    Nogueira, Leonardo; Ramirez-Sanchez, Israel; Perkins, Guy A; Murphy, Anne; Taub, Pam R; Ceballos, Guillermo; Villarreal, Francisco J; Hogan, Michael C; Malek, Moh H

    2011-09-15

    The flavanol (-)-epicatechin, a component of cacao (cocoa), has been shown to have multiple health benefits in humans. Using 1-year-old male mice, we examined the effects of 15 days of (-)-epicatechin treatment and regular exercise on: (1) exercise performance, (2) muscle fatigue, (3) capillarity, and (4) mitochondrial biogenesis in mouse hindlimb and heart muscles. Twenty-five male mice (C57BL/6N) were randomized into four groups: (1) water, (2) water-exercise (W-Ex), (3) (-)-epicatechin ((-)-Epi), and (4) (-)-epicatechin-exercise ((-)-Epi-Ex). Animals received 1 mg kg(-1) of (-)-epicatechin or water (vehicle) via oral gavage (twice daily). Exercise groups underwent 15 days of treadmill exercise. Significant increases in treadmill performance (∼50%) and enhanced in situ muscle fatigue resistance (∼30%) were observed with (-)-epicatechin. Components of oxidative phosphorylation complexes, mitofilin, porin, nNOS, p-nNOS, and Tfam as well as mitochondrial volume and cristae abundance were significantly higher with (-)-epicatechin treatment for hindlimb and cardiac muscles than exercise alone. In addition, there were significant increases in skeletal muscle capillarity. The combination of (-)-epicatechin and exercise resulted in further increases in oxidative phosphorylation-complex proteins, mitofilin, porin and capillarity than (-)-epicatechin alone. These findings indicate that (-)-epicatechin alone or in combination with exercise induces an integrated response that includes structural and metabolic changes in skeletal and cardiac muscles resulting in greater endurance capacity. These results, therefore, warrant the further evaluation of the underlying mechanism of action of (-)-epicatechin and its potential clinical application as an exercise mimetic.

  5. A Laboratory Experiment on Muscular Metabolism and Fatigue Using the Isolated Frog Muscle Preparation.

    ERIC Educational Resources Information Center

    Ianuzzo, C. David; And Others

    1987-01-01

    Describes an experiment which demonstrates the association of particular metabolic biochemical changes and muscular fatigue. Highlights applications related to cellular energy metabolism, metabolic regulation, and muscle energetics. (ML)

  6. Neck strength and myoelectric fatigue in fighter and helicopter pilots with a history of neck pain.

    PubMed

    Ang, Björn; Linder, Jan; Harms-Ringdahl, Karin

    2005-04-01

    Flight-induced neck pain at high Gz loads or during sustained rotary-wing missions may be caused by limitations in neck muscle function. A better understanding of the contributing factors of excessive external load and internal neck-stabilizing mechanisms would improve the ability to prevent and treat such pain. The aim of this single-blinded cross-sectional study was to evaluate neck neuromuscular function in fighter and helicopter pilots who suffered from frequent neck pain. Subjects with pain were 16 fighter pilots (FP-P) and 15 helicopter pilots (HP-P) with frequent neck pain episodes who were compared with pain-free controls (FP-C and HP-C). In all groups, neck extensor and flexor muscles were studied by measuring 1) the strength of maximum voluntary contraction (MVC), and 2) fatigue due to a submaximal isometric contraction. The decline (slope) of the electromyogram (EMG) median frequency power spectra was used as an index of fatigue, while initial median frequency (fi) was taken from the intercept of the regression line. Two-way analysis of variance (ANOVA) revealed interaction effects for extensor MVC. Post hoc testing showed that FP-P had significantly lower extensor MVC (p = 0.03) than FP-C, while there was no such difference for the HP-P vs. HP-C or between the two control groups. There were no significant effects for MVC-balance (flexors/extensors); nor were there any fi or extensor EMG-slope effects. However, there were interaction effects for flexor EMG-slopes: HP-P showed lower slopes than did HP-C (p = 0.02). To protect and stabilize the head and neck in high Gz environments, higher neck muscle strength is needed; less muscle strength in FP-P may cause further pain and perhaps reduced mission effectiveness. Less localized steep slopes for HP-P might reflect impaired muscle functioning. Specific preventive and clinical attention may be warranted for different types of pilot.

  7. Muscle fatigue examined at different temperatures in experiments on intact mammalian (rat) muscle fibers

    PubMed Central

    Roots, H.; Ball, G.; Talbot-Ponsonby, J.; King, M.; McBeath, K.; Ranatunga, K. W.

    2009-01-01

    In experiments on small bundles of intact fibers from a rat fast muscle, in vitro, we examined the decline in force in repeated tetanic contractions; the aim was to characterize the effect of shortening and of temperature on the initial phase of muscle fatigue. Short tetanic contractions were elicited at a control repetition rate of 1/60 s, and fatigue was induced by raising the rate to 1/5 s for 2–3 min, both in isometric mode (no shortening) and in shortening mode, in which each tetanic contraction included a ramp shortening at a standard velocity. In experiments at 20°C (n = 12), the force decline during a fatigue run was 25% in the isometric mode but was significantly higher (35%) in the shortening mode. In experiments at different temperatures (10–30°C, n = 11), the tetanic frequency and duration were adjusted as appropriate, and for shortening mode, the velocity was adjusted for maximum power output. In isometric mode, fatigue of force was significantly less at 30°C (∼20%) than at 10°C (∼30%); the power output (force × velocity) was >10× higher at 30°C than at 10°C, and power decline during a fatigue run was less at 30°C (∼20–30%) than at 10°C (∼50%). The finding that the extent of fatigue is increased with shortening contractions and is lower at higher temperatures is consistent with the view that force depression by inorganic phosphate, which accumulates within fibers during activity, may be a primary cause of initial muscle fatigue. PMID:19057001

  8. Prediction of Muscle Fatigue during Minimally Invasive Surgery Using Recurrence Quantification Analysis

    PubMed Central

    Keshavarz Panahi, Ali; Cho, Sohyung

    2016-01-01

    Due to its inherent complexity such as limited work volume and degree of freedom, minimally invasive surgery (MIS) is ergonomically challenging to surgeons compared to traditional open surgery. Specifically, MIS can expose performing surgeons to excessive ergonomic risks including muscle fatigue that may lead to critical errors in surgical procedures. Therefore, detecting the vulnerable muscles and time-to-fatigue during MIS is of great importance in order to prevent these errors. The main goal of this study is to propose and test a novel measure that can be efficiently used to detect muscle fatigue. In this study, surface electromyography was used to record muscle activations of five subjects while they performed fifteen various laparoscopic operations. The muscle activation data was then reconstructed using recurrence quantification analysis (RQA) to detect possible signs of muscle fatigue on eight muscle groups (bicep, triceps, deltoid, and trapezius). The results showed that RQA detects the fatigue sign on bilateral trapezius at 47.5 minutes (average) and bilateral deltoid at 57.5 minutes after the start of operations. No sign of fatigue was detected for bicep and triceps muscles of any subject. According to the results, the proposed novel measure can be efficiently used to detect muscle fatigue and eventually improve the quality of MIS procedures with reducing errors that may result from overlooked muscle fatigue. PMID:27313884

  9. Time and temperature dependence on the flexural fatigue strength in the transverse direction of unidirectional CFRP

    NASA Astrophysics Data System (ADS)

    Nakada, Masakazu; Maeda, M.; Hirohata, T.; Morita, M.; Miyano, Y.

    1997-03-01

    A prediction method of fatigue strength of polymer composites for an arbitrary frequency, stress ratio and temperature was proposed. The method is based upon the four hypotheses, (A) same failure mechanism for static, creep and fatigue failure, (b) same time-temperature superposition principle for all failure strengths, (C) linear cumulative damage law for monotone loading and (D) linear dependence of fatigue strength upon stress ratio. Flexural static, creep and fatigue tests at various temperatures were conducted in the transverse direction of two kinds of unidirectional CFRP laminates, which are T300/2500 and T300/PEEK. The validity of the prediction method and the applicability of the hypotheses for the flexural fatigue strength in the transverse direction of unidirectional CFRP laminates were discussed.

  10. Hydrogen-enabled microstructure and fatigue strength engineering of titanium alloys

    DOE PAGES

    Paramore, James D.; Fang, Zhigang Zak; Dunstan, Matthew; ...

    2017-02-01

    Traditionally, titanium alloys with satisfactory mechanical properties can only be produced via energy-intensive and costly wrought processes, while titanium alloys produced using low-cost powder metallurgy methods consistently result in inferior mechanical properties, especially low fatigue strength. Herein, we demonstrate a new microstructural engineering approach for producing low-cost titanium alloys with exceptional fatigue strength via the hydrogen sintering and phase transformation (HSPT) process. The high fatigue strength presented in this work is achieved by creating wroughtlike microstructures without resorting to wrought processing. This is accomplished by generating an ultrafine-grained as-sintered microstructure through hydrogen-enabled phase transformations, facilitating the subsequent creation of fatigue-resistantmore » microstructures via simple heat treatments. Finally, the exceptional strength, ductility, and fatigue performance reported in this paper are a breakthrough in the field of low-cost titanium processing.« less

  11. Hydrogen-enabled microstructure and fatigue strength engineering of titanium alloys

    NASA Astrophysics Data System (ADS)

    Paramore, James D.; Fang, Zhigang Zak; Dunstan, Matthew; Sun, Pei; Butler, Brady G.

    2017-02-01

    Traditionally, titanium alloys with satisfactory mechanical properties can only be produced via energy-intensive and costly wrought processes, while titanium alloys produced using low-cost powder metallurgy methods consistently result in inferior mechanical properties, especially low fatigue strength. Herein, we demonstrate a new microstructural engineering approach for producing low-cost titanium alloys with exceptional fatigue strength via the hydrogen sintering and phase transformation (HSPT) process. The high fatigue strength presented in this work is achieved by creating wrought-like microstructures without resorting to wrought processing. This is accomplished by generating an ultrafine-grained as-sintered microstructure through hydrogen-enabled phase transformations, facilitating the subsequent creation of fatigue-resistant microstructures via simple heat treatments. The exceptional strength, ductility, and fatigue performance reported in this paper are a breakthrough in the field of low-cost titanium processing.

  12. Hydrogen-enabled microstructure and fatigue strength engineering of titanium alloys.

    PubMed

    Paramore, James D; Fang, Zhigang Zak; Dunstan, Matthew; Sun, Pei; Butler, Brady G

    2017-02-01

    Traditionally, titanium alloys with satisfactory mechanical properties can only be produced via energy-intensive and costly wrought processes, while titanium alloys produced using low-cost powder metallurgy methods consistently result in inferior mechanical properties, especially low fatigue strength. Herein, we demonstrate a new microstructural engineering approach for producing low-cost titanium alloys with exceptional fatigue strength via the hydrogen sintering and phase transformation (HSPT) process. The high fatigue strength presented in this work is achieved by creating wrought-like microstructures without resorting to wrought processing. This is accomplished by generating an ultrafine-grained as-sintered microstructure through hydrogen-enabled phase transformations, facilitating the subsequent creation of fatigue-resistant microstructures via simple heat treatments. The exceptional strength, ductility, and fatigue performance reported in this paper are a breakthrough in the field of low-cost titanium processing.

  13. Hydrogen-enabled microstructure and fatigue strength engineering of titanium alloys

    PubMed Central

    Paramore, James D.; Fang, Zhigang Zak; Dunstan, Matthew; Sun, Pei; Butler, Brady G.

    2017-01-01

    Traditionally, titanium alloys with satisfactory mechanical properties can only be produced via energy-intensive and costly wrought processes, while titanium alloys produced using low-cost powder metallurgy methods consistently result in inferior mechanical properties, especially low fatigue strength. Herein, we demonstrate a new microstructural engineering approach for producing low-cost titanium alloys with exceptional fatigue strength via the hydrogen sintering and phase transformation (HSPT) process. The high fatigue strength presented in this work is achieved by creating wrought-like microstructures without resorting to wrought processing. This is accomplished by generating an ultrafine-grained as-sintered microstructure through hydrogen-enabled phase transformations, facilitating the subsequent creation of fatigue-resistant microstructures via simple heat treatments. The exceptional strength, ductility, and fatigue performance reported in this paper are a breakthrough in the field of low-cost titanium processing. PMID:28145527

  14. Effects of muscle extension strength exercise on trunk muscle strength and stability of patients with lumbar herniated nucleus pulposus

    PubMed Central

    Jeon, Kyoungkyu; Kim, Taeyoung; Lee, Sang-Ho

    2016-01-01

    [Purpose] The purpose of this study was to provide the data for constructing an integrated exercise program to help restore muscle strength and stability through extension strength exercise in adult females with lumbar disc herniation. [Subjects and Methods] An 8-week exercise program for lumbar muscle extension strength and stabilization was performed by 26 females older than 20 with lumbar disc herniation findings. [Results] Significant differences were found in lumbar extension muscle strength at every angle of lumbar flexion after participation in the 8-week stabilization exercise program; but there was no significant difference in the weight distribution index. [Conclusion] An integrated exercise program aiming to strengthen lumbar spine muscles, reduce pain and stabilize the trunk can help to maintain muscle strength and balance. In addition, improvement in extension strength is expected to be helpful in daily life by securing the range of joint motion and improving the strength and stability. PMID:27313342

  15. Quantifying the history dependency of muscle recovery from a fatiguing intermittent task.

    PubMed

    Rashedi, Ehsan; Nussbaum, Maury A

    2017-01-25

    Muscle fatigue and recovery are complex processes influencing muscle force generation capacity. While fatigue reduces this capacity, recovery acts to restore the unfatigued muscle state. Many factors can potentially affect muscle recovery, and among these may be a task dependency of recovery following an exercise. However, little has been reported regarding the history dependency of recovery after fatiguing contractions. We examined the dependency of muscle recovery subsequent to four different histories of fatiguing muscle contractions, imposed using two cycle times (30 and 60s) during low to moderate levels (15% and 25% of maximum voluntary contraction (MVC)) of intermittent static exertions involving index finger abduction. MVC and low-frequency electrical stimulation (LFES) measures (i.e., magnitude, rise and relaxation rates) of muscle capacity were used, all of which indicated a dependency of muscle recovery on the muscle capacity state existing immediately after fatiguing exercise. This dependency did not appear to be modified by either the cycle time or exertion level leading to that state. These results imply that the post-exercise rate of recovery is primarily influenced by the immediate post-exercise muscle contractile status (estimated by MVC and LFES measures). Such results may help improve existing models of muscle recovery, facilitating more accurate predictions of localized muscle fatigue development and thereby helping to enhance muscle performance and reduce the risk of injury.

  16. Sensible manual muscle strength testing to evaluate and monitor strength of the intrinsic muscles of the hand: a commentary.

    PubMed

    Brandsma, J W; Schreuders, T A

    2001-01-01

    Hand therapists often assess, evaluate, and monitor the status of, and changes in the strength of, the intrinsic muscles of the hand. Some common indications are peripheral and central neuropathies and nerve lacerations and repairs. The therapist will often use a muscle chart that lists all the muscles innervated by the ulnar and median nerves, and all muscles will be tested. Not all muscles in the hand can be sufficiently isolated to grade their strength, nor is it always necessary to test all muscles innervated by a particular nerve to evaluate the presence or extent of motor function impairment or monitor changes. This paper discusses the tests by which changes in strength of the ulnar and median innervated intrinsic muscles can be assessed and the reasons that certain muscles cannot or need not be tested. Information about the reliability of muscle testing is also given.

  17. Skeletal muscle: energy metabolism, fiber types, fatigue and adaptability.

    PubMed

    Westerblad, Håkan; Bruton, Joseph D; Katz, Abram

    2010-11-01

    Skeletal muscles cope with a large range of activities, from being able to support the body weight during long periods of upright standing to perform explosive movements in response to an unexpected threat. This requires systems for energy metabolism that can provide energy during long periods of moderately increased energy consumption as well as being able to rapidly increasing the rate of energy production more than 100-fold in response to explosive contractions. In this short review we discuss how muscles can deal with these divergent demands. We first outline the major energy metabolism pathways in skeletal muscle. Next we describe metabolic differences between different muscle fiber types. Contractile performance declines during intense activation, i.e. fatigue develops, and we discuss likely underlying mechanisms. Finally, we discuss the ability of muscle fibers to adapt to altered demands, and mechanisms behind these adaptations. The accumulated experimental evidence forces us to conclude that most aspects of energy metabolism involve multiple and overlapping signaling pathways, which indicates that the control of energy metabolism is too important to depend on one single molecule or mechanism. Copyright © 2010 Elsevier Inc. All rights reserved.

  18. Fatigue resistance of the knee extensor muscles is not reduced in post-polio syndrome.

    PubMed

    Voorn, Eric L; Beelen, Anita; Gerrits, Karin H L; Nollet, Frans; de Haan, Arnold

    2013-11-01

    The present study investigated whether intrinsic fatigability of the muscle fibers is reduced in patients with post-polio syndrome (PPS). This may contribute to the muscle fatigue complaints reported by patients with PPS. For this purpose, we assessed contractile properties and fatigue resistance of the knee extensor muscles using repeated isometric electrically evoked contractions in 38 patients with PPS and 19 age-matched healthy subjects. To determine whether any difference in fatigue resistance between both groups could be attributed to differences in aerobic capacity of the muscle fibers, 9 patients with PPS and 11 healthy subjects performed the same protocol under arterial occlusion. Results showed that fatigue resistance of patients with PPS was comparable to that in controls, both in the situation with intact circulation and with occluded blood flow. Together, our findings suggest that there are no differences in contractile properties and aerobic muscle capacity that may account for the increased muscle fatigue perceived in PPS.

  19. Muscle strength testing: use of normalisation for body size.

    PubMed

    Jaric, Slobodan

    2002-01-01

    Assessment of muscle strength tests has been a popular form of testing muscle function in sports and exercises, as well as in other movement-related sciences for several decades. Although the relationship between muscle strength and body size has attracted considerable attention from researchers, this relationship has been often either neglected or incorrectly taken into account when presenting the results from muscle strength tests. Two specific problems have been identified. First, most of the studies have presented strength data either non-normalised for body size, or normalised using inappropriate methods, or even several different normalisations have been applied on the same sets of data. Second, the role of body size in various movement performances has been neglected when functional movement performance was assessed by muscle strength. As a consequence, muscle function, athletic profiles, or functional movement performance assessed by tested muscle strength have been often confounded by the effect of body size. Differences in the normalisation methods applied also do not allow for comparison of the data obtained in different studies. Using the following allometric formula for obtaining index of muscle strength, S, independent of body size (assessed by body mass, m) should be recommended in routine strength testing procedures: The allometric parameter should be either b = 0.67 for muscle force (recorded by a dynamometer), or b = 1 for muscle torque (recorded by an isokinetic apparatus). We also recommend using body-size-independent indices of both muscle strength and movement performance when assessing functional performance from recorded muscle strength or vice versa.

  20. Potassium and caffeine contractures of mouse muscles before and after fatiguing stimulation.

    PubMed

    Pagala, M; Ravindran, K; Amaladevi, B; Namba, T; Grob, D

    1994-08-01

    To assess the impairment of muscle membrane excitation, excitation-contraction (E-C) coupling, and contractility during muscle fatigue, we monitored the contracture responses of resting and fatigued muscles on exposure to high potassium and caffeine. On exposure to 140 mmol/L potassium, mouse extensor digitorum longus (EDL) developed a contracture which was 15.7% of tetanic tension before fatigue and 31.7% after fatigue, while soleus developed 59.4% contracture before and 68.8% after fatigue. Potassium causes contractures by depolarizing the muscle fiber membrane. Hence, membrane excitation is reduced in fatigued EDL and soleus. On exposure to 32 mmol/L caffeine, the contracture was 7.1% in resting EDL, 8.5% in fatigued EDL, 50.1% in resting soleus, and 43.7% in fatigued soleus. On exposure to 1 mmol/L caffeine followed by rapid cooling, the contracture was 3.0% in resting EDL, 3.2% in fatigued EDL, 21.5% in resting soleus, and 10.3% in fatigued soleus. Caffeine causes contracture by releasing Ca++ from the sarcoplasmic reticulum. Our results indicate reduced E-C coupling attributable to reduced membrane excitation in fatigued EDL, and reduced contractility in fatigued soleus.

  1. Acute Effects of Static vs. Ballistic Stretching on Strength and Muscular Fatigue Between Ballet Dancers and Resistance-Trained Women.

    PubMed

    Lima, Camila D; Brown, Lee E; Wong, Megan A; Leyva, Whitney D; Pinto, Ronei S; Cadore, Eduardo L; Ruas, Cassio V

    2016-11-01

    Lima, CD, Brown, LE, Wong, MA, Leyva, WD, Pinto, RS, Cadore, EL, and Ruas, CV. Acute effects of static vs. ballistic stretching on strength and muscular fatigue between ballet dancers and resistance-trained women. J Strength Cond Res 30(11): 3220-3227, 2016-Stretching is used to increase joint range of motion, but the acute effects can decrease muscle strength. However, this may depend on the population or mode of stretching. The purpose of this study was to compare the acute effects of static vs. ballistic stretching on strength and muscular fatigue between ballet dancers and resistance-trained women. Fifteen resistance-trained women (age 23.8 ± 1.80 years, mass 67.47 ± 7.77 kg, height 168.30 ± 5.53 cm) and 12 ballet dancers (age 22.8 ± 3.04 years, mass 58.67 ± 5.65 kg, height 168.00 ± 7.69 cm) performed 5 days of testing. The first day was control (no stretching), whereas the other 4 days were static or ballistic stretching in a counterbalanced order. Range of motion, strength, and fatigue tests were also performed. Both groups demonstrated a significant decrease in hamstrings strength after static (102.71 ± 2.67 N·m) and ballistic stretching (99.49 ± 2.61 N·m) compared with control (113.059 ± 3.25 N·m), with no changes in quadriceps strength. For fatigue, only ballet dancers demonstrated a decrease from control (71.79 ± 4.88%) to ballistic (65.65 ± 8.19%), but no difference with static (65.01 ± 12.29%). These findings suggest that stretching decreases hamstrings strength similarly in ballet dancers and resistance-trained women, with no differences between modes of stretching. However, ballistic stretching only decreased muscular fatigue in ballet dancers, but not in resistance-trained women. Therefore, no stretching should be performed before strength performance. However, ballistic stretching may decrease acute muscular fatigue in ballet dancers.

  2. Fatigue Strength Estimation Based on Local Mechanical Properties for Aluminum Alloy FSW Joints

    PubMed Central

    Sillapasa, Kittima; Mutoh, Yoshiharu; Miyashita, Yukio; Seo, Nobushiro

    2017-01-01

    Overall fatigue strengths and hardness distributions of the aluminum alloy similar and dissimilar friction stir welding (FSW) joints were determined. The local fatigue strengths as well as local tensile strengths were also obtained by using small round bar specimens extracted from specific locations, such as the stir zone, heat affected zone, and base metal. It was found from the results that fatigue fracture of the FSW joint plate specimen occurred at the location of the lowest local fatigue strength as well as the lowest hardness, regardless of microstructural evolution. To estimate the fatigue strengths of aluminum alloy FSW joints from the hardness measurements, the relationship between fatigue strength and hardness for aluminum alloys was investigated based on the present experimental results and the available wide range of data from the references. It was found as: σa (R = −1) = 1.68 HV (σa is in MPa and HV has no unit). It was also confirmed that the estimated fatigue strengths were in good agreement with the experimental results for aluminum alloy FSW joints. PMID:28772543

  3. Fatigue Strength Estimation Based on Local Mechanical Properties for Aluminum Alloy FSW Joints.

    PubMed

    Sillapasa, Kittima; Mutoh, Yoshiharu; Miyashita, Yukio; Seo, Nobushiro

    2017-02-15

    Overall fatigue strengths and hardness distributions of the aluminum alloy similar and dissimilar friction stir welding (FSW) joints were determined. The local fatigue strengths as well as local tensile strengths were also obtained by using small round bar specimens extracted from specific locations, such as the stir zone, heat affected zone, and base metal. It was found from the results that fatigue fracture of the FSW joint plate specimen occurred at the location of the lowest local fatigue strength as well as the lowest hardness, regardless of microstructural evolution. To estimate the fatigue strengths of aluminum alloy FSW joints from the hardness measurements, the relationship between fatigue strength and hardness for aluminum alloys was investigated based on the present experimental results and the available wide range of data from the references. It was found as: σa (R = -1) = 1.68 HV (σa is in MPa and HV has no unit). It was also confirmed that the estimated fatigue strengths were in good agreement with the experimental results for aluminum alloy FSW joints.

  4. A New Perspective on Fatigue Performance of Advanced High- Strength Steels (AHSS) GMAW Joints

    SciTech Connect

    Feng, Zhili; Chiang, Dr. John; Kuo, Dr. Min; Jiang, Cindy; Sang, Yan

    2008-01-01

    Weld fatigue performance is a critical aspect for application of advanced high-strength steels (AHSS) in automotive body structures. A comparative study has been conducted to evaluate the fatigue life of AHSS welds. The material studied included seven AHSS of various strength levels - DP 600, DP 780, DP 980, M130, M220, solution annealed boron and fully hardened boron steels. Two conventional steels, HSLA 590 and DR 210, were also included for baseline comparison. Lap fillet welds were made on 2-mm nominal thick sheets by the gas metal arc welding process (GMAW). Fatigue test was conducted under a number of stress levels to obtain the S/N curves of the weld joints. It was found that, unlike in the static and impact loading conditions, the fatigue performance of AHSS is not influenced by the HAZ softening in AHSS. There are appreciable differences in the fatigue lives among different AHSS. Changes in weld parameters can influence the fatigue life of the weld joints, particularly of these of higher strength AHSS. A model is developed to predict the fatigue performance of AHSS welds. The validity of the model is benchmarked with the experimental results. This model is capable to capture the effects of weld geometry and weld microstructure and strength on the fatigue performance experimentally observed. The theoretical basis and application of the newly developed fatigue modeling methodology will be discussed.

  5. Effects of kinesiology taping on repositioning error of the knee joint after quadriceps muscle fatigue.

    PubMed

    Han, Jin Tae; Lee, Jung-Hoon

    2014-06-01

    [Purpose] The purpose of this study was to identify the effects of kinesiology taping on repositioning error of the knee joint after quadriceps muscle fatigue. [Subjects] Thirty healthy adults with no orthopaedic or neurological problems participated in this study. [Methods] The repositioning error of the knee joint was measured using a digital goniometer when the subjects extended their dominant-side knee to a random target angle (30°, 45°, or 60°) with their eyes closed, before and after a quadriceps muscle fatigue protocol, and after application of kinesiology tape. [Results] We found that repositioning errors of the dominant-side knee joint increased after quadriceps fatigue compared with no-fatigue conditions. However, kinesiology taping of the quadriceps muscle and patella after quadriceps fatigue significantly decreased repositioning errors of the knee joint. [Conclusion] These results suggest that quadriceps fatigue increases the repositioning error of the knee joint, whereas application of kinesiology tape decreases fatigue-induced joint repositioning error.

  6. The influence of hole size in static strength and fatigue for CFRP composite materials

    SciTech Connect

    Yip, M.C.; Perng, T.B.

    1993-12-31

    The influence of hole size in static strength and fatigue property will be investigated. Carbon/Epoxy laminate is selected as testing materials which are widely used in aircraft industry. The arrangement of fiber orientation is [0{sup 0}/+45{sup 0}/{minus}45{sup 0}/90{sup 0}]{sub 2s}. The basic mechanical properties of smooth and notched specimens were detected. The strength of notched specimens are applied to compare with Whitney-Nuismer stress criterion. For average stress criteria, the theoretical value is in good agreement with experimental data for the parameter a{sub 0} is chosen 1.5 mm. For point stress criteria, the best choice of parameter do is 2.4 mm, but the agreement of experimental data is poorer than the average stress one. The characteristic curve of tension-tension fatigue for smooth and notched laminate were investigated. The notched specimens has a 1 mm diameter circular hole at the center, the stress ratio of fatigue test is 0.1. It is obvious that the data distribution of smooth specimens is more scatter than notched specimens. On the other hand, the reduction of modulus during fatigue process was inspected. After fatigue damage, the influence of hole size on residual strength for a quasi-isotropic laminate was investigated. It is found that residual strength of damaged specimens are higher than undamaged one in some fatigue damage range. When the maximum applied load of fatigue test is chosen 90 percent of static strength, it is seen that the influence is obviously in residual strength. The increment of strength decreases with hole size increasing. When the maximum applied load of fatigue test is chosen 80 percent of static strength, the influence is less than the previous case. The Whitney-Nuismer Average Stress Criteria is extended to predict the residual strength after fatigue. A good prediction can be shown by using the extended criteria.

  7. Cation pumps in skeletal muscle: potential role in muscle fatigue.

    PubMed

    Green, H J

    1998-03-01

    Two membrane bound pumps in skeletal muscle, the sarcolemma Na+-K+ adenosine triphosphatase (ATPase) and the sarcoplasmic reticulum Ca2+-ATPase, provide for the maintenance of transmembrane ionic gradients necessary for excitation and activation of the myofibrillar apparatus. The rate at which the pumps are capable of establishing ionic homeostasis depends on the maximal activity of the enzyme and the potential of the metabolic pathways for supplying adenosine triphosphate (ATP). The activity of the Ca2+-ATPase appears to be expressed in a fibre type specific manner with both the amount of the enzyme and the isoform type related to the speed of contraction. In contrast, only minimal differences exist between slow-twitch and fast-twitch fibres in Na+-K+ ATPase activity. Evidence is accumulating that both active transport of Na+ and K+ across the sarcolemma and Ca2+-uptake by the sarcoplasmic reticulum may be impaired in vivo in a task specific manner resulting in loss of contractile function. In contrast to the Ca2+-ATPase, the Na+-K+ ATPase can be rapidly upregulated soon after the onset of a sustained pattern of activity. Similar programmes of activity result in a downregulation of Ca2+-ATPase but at a much later time point. The manner in which the metabolic pathways reorganize following chronic activity to meet the changes in ATP demand by the cation pumps and the degree to which these adaptations are compartmentalized is uncertain.

  8. Skeletal muscle properties and fatigue resistance in relation to smoking history.

    PubMed

    Wüst, Rob C I; Morse, Christopher I; de Haan, Arnold; Rittweger, Jörn; Jones, David A; Degens, Hans

    2008-09-01

    Although smoking-related diseases, such as chronic obstructive pulmonary disease (COPD), are often accompanied by increased peripheral muscle fatigability, the extent to which this is a feature of the disease or a direct effect of smoking per se is not known. Skeletal muscle function was investigated in terms of maximal voluntary isometric torque, activation, contractile properties and fatigability, using electrically evoked contractions of the quadriceps muscle of 40 smokers [19 men and 21 women; mean (SD) cigarette pack years: 9.9 (10.7)] and age- and physical activity level matched non-smokers (22 men and 23 women). Maximal strength and isometric contractile speed did not differ significantly between smokers and non-smokers. Muscle fatigue (measured as torque decline during a series of repetitive contractions) was greater in smokers (P = 0.014), but did not correlate with cigarette pack years (r = 0.094, P = 0.615), cigarettes smoked per day (r = 10.092, P = 0.628), respiratory function (%FEV(1pred)) (r = -0.187, P = 0.416), or physical activity level (r = -0.029, P = 0.877). While muscle mass and contractile properties are similar in smokers and non-smokers, smokers do suffer from greater peripheral muscle fatigue. The observation that the cigarette smoking history did not correlate with fatigability suggests that the effect is either acute and/or reaches a ceiling, rather than being cumulative. An acute and reversible effect of smoking could be caused by carbon monoxide and/or other substances in smoke hampering oxygen delivery and mitochondrial function.

  9. Tribute to Dr Jacques Rogge: muscle activity and fatigue during hiking in Olympic dinghy sailing.

    PubMed

    Bourgois, Jan G; Dumortier, Jasmien; Callewaert, Margot; Celie, Bert; Capelli, Carlo; Sjøgaard, Gisela; De Clercq, Dirk; Boone, Jan

    2017-03-19

    'A tribute to Dr J. Rogge' aims to systematically review muscle activity and muscle fatigue during sustained submaximal quasi-isometric knee extension exercise (hiking) related to Olympic dinghy sailing as a tribute to Dr Rogge's merits in the world of sports. Dr Jacques Rogge is not only the former President of the International Olympic Committee, he was also an orthopaedic surgeon and a keen sailor, competing at three Olympic Games. In 1972, in fulfilment of the requirements for the degree of Master in Sports Medicine, he was the first who studied a sailors' muscle activity by means of invasive needle electromyography (EMG) during a specific sailing technique (hiking) on a self-constructed sailing ergometer. Hiking is a bilateral and multi-joint submaximal quasi-isometric movement which dinghy sailors use to optimize boat speed and to prevent the boat from capsizing. Large stresses are generated in the anterior muscles that cross the knee and hip joint, mainly employing the quadriceps at an intensity of 30-40% maximal voluntary contraction (MVC), sometimes exceeding 100% MVC. Better sailing level is partially determined by a lower rate of neuromuscular fatigue during hiking and for ≈60% predicted by a higher maximal isometric quadriceps strength. Although useful in exercise testing, prediction of hiking endurance capacity based on the changes in surface EMG in thigh and trunk muscles during a hiking maintenance task is not reliable. This could probably be explained by the varying exercise intensity and joint angles, and the great number of muscles and joints involved in hiking.

  10. Upper limb muscle strength & endurance in chronic obstructive pulmonary disease.

    PubMed

    Shah, Swati; Nahar, Pradeep; Vaidya, Savita; Salvi, Sundeep

    2013-10-01

    There are very few studies that have investigated the muscle strength and endurance of upper limbs (UL) in chronic obstructive pulmonary disease (COPD). We undertook this study to measure and compare the skeletal muscle strength and endurance of UL in COPD patients and age matched healthy controls and to study the association between lung function parameters and UL muscle strength and endurance. Forty one COPD patients and 45 height and weight matched healthy subjects of the same age group were studied. UL skeletal muscle strength and endurance were measured using the hand grip dynamometer test. Forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV₁), forced expiratory flow during 25-75% FVC (FEF (25-75%)) and peak expiratory flow rate (PEFR) were measured. The handgrip muscle strength and endurance between the two groups were compared and correlations between FVC and FEV 1 with muscle strength and endurance were analyzed. The mean handgrip strength and mean muscle endurance in COPD patients were significantly lesser than the normal subjects in both males and females (P<0.001). There was significant positive correlation between muscle strength and FVC in males (r² =0.32, P<0.05); and between muscle strength and FEV₁ in females (r² =0.20, P<0.05). The study showed that the handgrip muscle strength decreases as the FVC and FEV₁ decrease in patients with COPD. Identifying those patients who have reduced strength and endurance will allow early interventions targeted at improving the quality of life of the patient.

  11. Structural strength analysis and fatigue life prediction of traction converter box in high-speed EMU

    NASA Astrophysics Data System (ADS)

    Tan, Qin; Li, Qiang

    2017-01-01

    The method of building the FEA model of traction converter box in high-speed EMU and analyzing the static strength and fatigue strength of traction converter box based on IEC 61373-2010 and EN 12663 standards is presented in this paper. The load-stress correlation coefficients of weak points is obtained by FEA model, applied to transfer the load history of traction converter box to stress history of each point. The fatigue damage is calculated based on Miner's rule and the fatigue life of traction converter box is predicted. According to study, the structural strength of traction converter box meets design requirements.

  12. Knee joint angle and vasti muscle electromyograms during fatiguing contractions.

    PubMed

    Ando, Ryosuke; Tomita, Aya; Watanabe, Kohei; Akima, Hiroshi

    2016-05-19

    We compared vasti muscle electromyograms for two knee joint angles during fatiguing tetanic contractions. Tetanic contraction of the knee extensors was evoked for 70 s by electrical stimulation of the femoral nerve at knee joint angles of 60° (extended, with 0° indicating full extension) and 110° (flexed) in eight healthy men. Surface electromyography was recorded from the vastus intermedius (VI), vastus lateralis (VL) and vastus medialis (VM) muscles. Knee extension force and M-wave amplitudes and durations were calculated every 7 s, which were normalized by the initial value. Normalized knee extension force was decreased at the flexed knee joint angle compared with that of the extended knee joint angle (P<0·05). Decreased normalized M-wave amplitude and increased normalized M-wave duration of the VI were greater at the flexed knee joint angle than the extended knee joint angle (P<0·05), whereas those for the VL and VM were similar (P>0·05). These results suggest that peripheral fatigue profiles of the VI might be greater at the flexed than the extended knee joint angles, but that of VL and VM might be similar in the tested range of knee joint angles (i.e. 60°-110°) during continuous tetanic contraction induced by electrical stimulation. Therefore, greater reduction of knee extension force at the flexed knee joint angle than the extended knee joint angle may reflect fatigue development of the VI more than other quadriceps femoris components. © 2016 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

  13. Exceptional high fatigue strength in Cu-15at.%Al alloy with moderate grain size

    PubMed Central

    Liu, Rui; Tian, Yanzhong; Zhang, Zhenjun; An, Xianghai; Zhang, Peng; Zhang, Zhefeng

    2016-01-01

    It is commonly proposed that the fatigue strength can be enhanced by increasing the tensile strength, but this conclusion needs to be reconsidered according to our study. Here a recrystallized α-Cu-15at.%Al alloy with moderate grain size of 0.62 μm was fabricated by cold rolling and annealing, and this alloy achieved exceptional high fatigue strength of 280 MPa at 107 cycles. This value is much higher than the fatigue strength of 200 MPa for the nano-crystalline counterpart (0.04 μm in grain size) despite its higher tensile strength. The remarkable improvement of fatigue strength should be mainly attributed to the microstructure optimization, which helps achieve the reduction of initial damage and the dispersion of accumulated damage. A new strategy of “damage reduction” was then proposed for fatigue strength improvement, to supplement the former strengthening principle. The methods and strategies summarized in this work offer a general pathway for further improvement of fatigue strength, in order to ensure the long-term safety of structural materials. PMID:27264347

  14. Exceptional high fatigue strength in Cu-15at.%Al alloy with moderate grain size

    NASA Astrophysics Data System (ADS)

    Liu, Rui; Tian, Yanzhong; Zhang, Zhenjun; An, Xianghai; Zhang, Peng; Zhang, Zhefeng

    2016-06-01

    It is commonly proposed that the fatigue strength can be enhanced by increasing the tensile strength, but this conclusion needs to be reconsidered according to our study. Here a recrystallized α-Cu-15at.%Al alloy with moderate grain size of 0.62 μm was fabricated by cold rolling and annealing, and this alloy achieved exceptional high fatigue strength of 280 MPa at 107 cycles. This value is much higher than the fatigue strength of 200 MPa for the nano-crystalline counterpart (0.04 μm in grain size) despite its higher tensile strength. The remarkable improvement of fatigue strength should be mainly attributed to the microstructure optimization, which helps achieve the reduction of initial damage and the dispersion of accumulated damage. A new strategy of “damage reduction” was then proposed for fatigue strength improvement, to supplement the former strengthening principle. The methods and strategies summarized in this work offer a general pathway for further improvement of fatigue strength, in order to ensure the long-term safety of structural materials.

  15. It wears me out just imagining it! Mental imagery leads to muscle fatigue and diminished performance of isometric exercise.

    PubMed

    Graham, Jeffrey D; Sonne, Michael W L; Bray, Steven R

    2014-12-01

    The purpose of this study was to investigate the aftereffects of self-generated mental imagery of an effortful task on physical self-control endurance and muscle fatigue. Participants performed two isometric handgrip endurance trials (50% of maximum contraction) separated by either an imagery manipulation or a quiet rest period. The imagery group showed greater negative changes in endurance performance from trial 1 to trial 2 (p=.003, d=0.87) and increased muscle activation at baseline (p=.01, d=0.73) and at 25% (p=.03, d=0.61) of the second endurance trial compared to controls. We conclude that imagined performance of an effortful task depletes self-control strength and contributes to muscle fatigue.

  16. Muscle Fatigue Affects the Interpolated Twitch Technique When Assessed Using Electrically-Induced Contractions in Human and Rat Muscles

    PubMed Central

    Neyroud, Daria; Cheng, Arthur J.; Bourdillon, Nicolas; Kayser, Bengt; Place, Nicolas; Westerblad, Håkan

    2016-01-01

    The interpolated twitch technique (ITT) is the gold standard to assess voluntary activation and central fatigue. Yet, its validity has been questioned. Here we studied how peripheral fatigue can affect the ITT. Repeated contractions at submaximal frequencies were produced by supramaximal electrical stimulations of the human adductor pollicis muscle in vivo and of isolated rat soleus fiber bundles; an extra stimulation pulse was given during contractions to induce a superimposed twitch. Human muscles fatigued by repeated 30-Hz stimulation trains (3 s on–1 s off) showed an ~80% reduction in the superimposed twitch force accompanied by a severely reduced EMG response (M-wave amplitude), which implies action potential failure. Subsequent experiments combined a less intense stimulation protocol (1.5 s on–3 s off) with ischemia to cause muscle fatigue, but which preserved M-wave amplitude. However, the superimposed twitch force still decreased markedly more than the potentiated twitch force; with ITT this would reflect increased “voluntary activation.” In contrast, the superimposed twitch force was relatively spared when a similar protocol was performed in rat soleus bundles. Force relaxation was slowed by >150% in fatigued human muscles, whereas it was unchanged in rat soleus bundles. Accordingly, results similar to those in the human muscle were obtained when relaxation was slowed by cooling the rat soleus muscles. In conclusion, our data demonstrate that muscle fatigue can confound the quantification of central fatigue using the ITT. PMID:27445844

  17. Muscle Fatigue Affects the Interpolated Twitch Technique When Assessed Using Electrically-Induced Contractions in Human and Rat Muscles.

    PubMed

    Neyroud, Daria; Cheng, Arthur J; Bourdillon, Nicolas; Kayser, Bengt; Place, Nicolas; Westerblad, Håkan

    2016-01-01

    The interpolated twitch technique (ITT) is the gold standard to assess voluntary activation and central fatigue. Yet, its validity has been questioned. Here we studied how peripheral fatigue can affect the ITT. Repeated contractions at submaximal frequencies were produced by supramaximal electrical stimulations of the human adductor pollicis muscle in vivo and of isolated rat soleus fiber bundles; an extra stimulation pulse was given during contractions to induce a superimposed twitch. Human muscles fatigued by repeated 30-Hz stimulation trains (3 s on-1 s off) showed an ~80% reduction in the superimposed twitch force accompanied by a severely reduced EMG response (M-wave amplitude), which implies action potential failure. Subsequent experiments combined a less intense stimulation protocol (1.5 s on-3 s off) with ischemia to cause muscle fatigue, but which preserved M-wave amplitude. However, the superimposed twitch force still decreased markedly more than the potentiated twitch force; with ITT this would reflect increased "voluntary activation." In contrast, the superimposed twitch force was relatively spared when a similar protocol was performed in rat soleus bundles. Force relaxation was slowed by >150% in fatigued human muscles, whereas it was unchanged in rat soleus bundles. Accordingly, results similar to those in the human muscle were obtained when relaxation was slowed by cooling the rat soleus muscles. In conclusion, our data demonstrate that muscle fatigue can confound the quantification of central fatigue using the ITT.

  18. Fatigue mechanisms in patients with cancer: effects of tumor necrosis factor and exercise on skeletal muscle

    NASA Technical Reports Server (NTRS)

    St Pierre, B. A.; Kasper, C. E.; Lindsey, A. M.

    1992-01-01

    Fatigue is a common adverse effect of cancer and its therapy. However, the specific mechanisms underlying cancer fatigue are unclear. One physiologic mechanism may involve changes in skeletal muscle protein stores or metabolite concentration. A reduction in skeletal muscle protein stores may result from endogenous tumor necrosis factor (TNF) or from TNF administered as antineoplastic therapy. This muscle wasting would require patients to exert an unusually high amount of effort to generate adequate contractile force during exercise performance or during extended periods of sitting or standing. This additional effort could result in the onset of fatigue. Additionally, cancer fatigue may develop or become exacerbated during exercise as a consequence of changes in the concentration of skeletal muscle metabolites. These biochemical alterations may interfere with force that is produced by the muscle contractile proteins. These physiologic changes may play a role in the decision to include exercise in the rehabilitation plans of patients with cancer. They also may affect ideas about fatigue.

  19. Analysis of Muscle Fatigue Progression using Cyclostationary Property of Surface Electromyography Signals.

    PubMed

    Karthick, P A; Venugopal, G; Ramakrishnan, S

    2016-01-01

    Analysis of neuromuscular fatigue finds various applications ranging from clinical studies to biomechanics. Surface electromyography (sEMG) signals are widely used for these studies due to its non-invasiveness. During cyclic dynamic contractions, these signals are nonstationary and cyclostationary. In recent years, several nonstationary methods have been employed for the muscle fatigue analysis. However, cyclostationary based approach is not well established for the assessment of muscle fatigue. In this work, cyclostationarity associated with the biceps brachii muscle fatigue progression is analyzed using sEMG signals and Spectral Correlation Density (SCD) functions. Signals are recorded from fifty healthy adult volunteers during dynamic contractions under a prescribed protocol. These signals are preprocessed and are divided into three segments, namely, non-fatigue, first muscle discomfort and fatigue zones. Then SCD is estimated using fast Fourier transform accumulation method. Further, Cyclic Frequency Spectral Density (CFSD) is calculated from the SCD spectrum. Two features, namely, cyclic frequency spectral area (CFSA) and cyclic frequency spectral entropy (CFSE) are proposed to study the progression of muscle fatigue. Additionally, degree of cyclostationarity (DCS) is computed to quantify the amount of cyclostationarity present in the signals. Results show that there is a progressive increase in cyclostationary during the progression of muscle fatigue. CFSA shows an increasing trend in muscle fatiguing contraction. However, CFSE shows a decreasing trend. It is observed that when the muscle progresses from non-fatigue to fatigue condition, the mean DCS of fifty subjects increases from 0.016 to 0.99. All the extracted features found to be distinct and statistically significant in the three zones of muscle contraction (p < 0.05). It appears that these SCD features could be useful in the automated analysis of sEMG signals for different neuromuscular conditions.

  20. Respiratory Muscle Strength Predicts Decline in Mobility in Older Persons

    PubMed Central

    Buchman, A.S.; Boyle, P.A.; Wilson, R.S.; Leurgans, S.; Shah, R.C.; Bennett, D.A.

    2008-01-01

    Objectives To test the hypothesis that respiratory muscle strength is associated with the rate of change in mobility even after controlling for leg strength and physical activity. Methods Prospective study of 890 ambulatory older persons without dementia who underwent annual clinical evaluations to examine change in the rate of mobility over time. Results In a linear mixed-effect model adjusted for age, sex, and education, mobility declined about 0.12 unit/year, and higher levels of respiratory muscle strength were associated with a slower rate of mobility decline (estimate 0.043, SE 0.012, p < 0.001). Respiratory muscle strength remained associated with the rate of change in mobility even after controlling for lower extremity strength (estimate 0.036, SE 0.012, p = 0.004). In a model that included terms for respiratory muscle strength, lower extremity strength and physical activity together, all three were independent predictors of mobility decline in older persons. These associations remained significant even after controlling for body composition, global cognition, the development of dementia, parkinsonian signs, possible pulmonary disease, smoking, joint pain and chronic diseases. Conclusion Respiratory muscle strength is associated with mobility decline in older persons independent of lower extremity strength and physical activity. Clinical interventions to improve respiratory muscle strength may decrease the burden of mobility impairment in the elderly. PMID:18784416

  1. Spatially distributed sequential stimulation reduces muscle fatigue during neuromuscular electrical stimulation.

    PubMed

    Sayenko, Dimitry G; Popovic, Milos R; Masani, Kei

    2013-01-01

    A critical limitation with neuromuscular electrical stimulation (NMES) approach is the rapid onset of muscle fatigue during repeated contractions, which results in the muscle force decay and slowing of muscle contractile properties. In our previous study, we demonstrated that spatially distributed sequential stimulation (SDSS) show a drastically greater fatigue-reducing ability compared to a conventional, single active electrode stimulation (SES) with an individual with spinal cord injury when applied for plantar flexors. The purpose of the present study is to explore the fatigue-reducing ability of SDSS for major lower limb muscle groups in the able-bodied population as well as individuals with spinal cord injury (SCI). SDSS was delivered through four active electrodes applied to the muscle of interest, sending a stimulation pulse to each electrode one after another with 90° phase shift between successive electrodes. For comparison, SES was delivered through one active electrode. For both modes of stimulation, the resultant frequency to the muscle as a whole was 40 Hz. Using corresponding protocols for the fatiguing stimulation, we demonstrated the fatigue-reducing ability of SDSS by higher fatigue indices as compared with single active electrode setup for major leg muscles in both subject groups. The present work verifies and extends reported findings on the effectiveness of using spatially distributed sequential stimulation in the leg muscles to reduce muscle fatigue. Application of this technique can improve the usefulness of NMES during functional movements in the clinical setup.

  2. The influence of inspiratory muscle work history and specific inspiratory muscle training upon human limb muscle fatigue.

    PubMed

    McConnell, Alison K; Lomax, Michelle

    2006-11-15

    The purpose of this study was to assess the influence of the work history of the inspiratory muscles upon the fatigue characteristics of the plantar flexors (PF). We hypothesized that under conditions where the inspiratory muscle metaboreflex has been elicited, PF fatigue would be hastened due to peripheral vasoconstriction. Eight volunteers undertook seven test conditions, two of which followed 4 week of inspiratory muscle training (IMT). The inspiratory metaboreflex was induced by inspiring against a calibrated flow resistor. We measured torque and EMG during isometric PF exercise at 85% of maximal voluntary contraction (MVC) torque. Supramaximal twitches were superimposed upon MVC efforts at 1 min intervals (MVC(TI)); twitch interpolation assessed the level of central activation. PF was terminated (T(lim)) when MVC(TI) was <50% of baseline MVC. PF T(lim) was significantly shorter than control (9.93 +/- 1.95 min) in the presence of a leg cuff inflated to 140 mmHg (4.89 +/- 1.78 min; P = 0.006), as well as when PF was preceded immediately by fatiguing inspiratory muscle work (6.28 +/- 2.24 min; P = 0.009). Resting the inspiratory muscles for 30 min restored the PF T(lim) to control. After 4 weeks, IMT, inspiratory muscle work at the same absolute intensity did not influence PF T(lim), but T(lim) was significantly shorter at the same relative intensity. The data are the first to provide evidence that the inspiratory muscle metaboreflex accelerates the rate of calf fatigue during PF, and that IMT attenuates this effect.

  3. Muscle fatigue induced by a soccer match-play simulation in amateur Black South African players.

    PubMed

    Jones, Robert I; Ryan, Bennett; Todd, Andrew I

    2015-01-01

    The purpose of the current study was to investigate the effects of a soccer-specific fatigue protocol on the temporal changes in torque producing abilities of the thigh within African soccer players. Twenty amateur Black South African soccer players performed the SAFT(90) soccer match-play simulation protocol, while isokinetic measurements were obtained pre-exercise (T0), after the 1st half (T45), after half time (T60) and after the 2nd half (T105). During SAFT(90) performance, significant overall concentric quadriceps peak torque changes were observed (1.05 rad · s(-1) = 16.6%, 3.14 rad · s(-1) = 9.5%). Eccentric hamstring peak torque also decreased significantly over time (1.05 rad · s(-1) = 17.4%, 3.14 rad · s(-1) = 18.5%), with significant reductions occurring during both halves. The functional strength ratio (eccH:conQ) at 3.14 rad · s(-1) was observed to significantly decrease by 10.1% overall. The indicated time-dependent changes in Black South African players have implications for competitive performance and increased predisposition to hamstring muscle injuries. Because of muscle fatigue, the hamstrings may have insufficient eccentric strength during the late swing phase when sprinting, resulting in eccentric overload and damage to the muscle. The changes in strength found in the current study help explain the increased predisposition to hamstring strains during the latter stages of both halves of match-play as reported by epidemiological studies.

  4. Objective Evaluation of Muscle Strength in Infants with Hypotonia and Muscle Weakness

    ERIC Educational Resources Information Center

    Reus, Linda; van Vlimmeren, Leo A.; Staal, J. Bart; Janssen, Anjo J. W. M.; Otten, Barto J.; Pelzer, Ben J.; Nijhuis-van der Sanden, Maria W. G.

    2013-01-01

    The clinical evaluation of an infant with motor delay, muscle weakness, and/or hypotonia would improve considerably if muscle strength could be measured objectively and normal reference values were available. The authors developed a method to measure muscle strength in infants and tested 81 typically developing infants, 6-36 months of age, and 17…

  5. Objective Evaluation of Muscle Strength in Infants with Hypotonia and Muscle Weakness

    ERIC Educational Resources Information Center

    Reus, Linda; van Vlimmeren, Leo A.; Staal, J. Bart; Janssen, Anjo J. W. M.; Otten, Barto J.; Pelzer, Ben J.; Nijhuis-van der Sanden, Maria W. G.

    2013-01-01

    The clinical evaluation of an infant with motor delay, muscle weakness, and/or hypotonia would improve considerably if muscle strength could be measured objectively and normal reference values were available. The authors developed a method to measure muscle strength in infants and tested 81 typically developing infants, 6-36 months of age, and 17…

  6. Generalization of Muscle Strength Capacities as Assessed From Different Variables, Tests, and Muscle Groups.

    PubMed

    Cuk, Ivan; Prebeg, Goran; Sreckovic, Sreten; Mirkov, Dragan M; Jaric, Slobodan

    2017-02-01

    Cuk, I, Prebeg, G, Sreckovic, S, Mirkov, DM, and Jaric, S. Generalization of muscle strength capacities as assessed from different variables, tests, and muscle groups. J Strength Cond Res 31(2): 305-312, 2017-The muscle strength capacities to exert force under various movement conditions have been indiscriminately assessed from various strength tests and variables applied on different muscles. We tested the hypotheses that the distinctive strength capacities would be revealed (H1) through different strength tests, and (H2) through different strength variables. Alternatively, (H3) all strength variables independent of the selected test could depict the same strength capacity of the tested muscle. Sixty subjects performed both the standard strength test and the test of alternating contractions of 6 pairs of antagonistic muscles acting in different leg and arm joints. The dependent variables obtained from each test and muscle were the maximum isometric force and the rate of force development. A confirmatory principle component analysis set to 2 factors explained 31.9% of the total variance. The factor loadings discerned between the tested arm and leg muscles, but not between the strength tests and variables. An exploratory analysis applied on the same data revealed 6 factors that explained 60.1% of the total variance. Again, the individual factors were mainly loaded by different tests and variables obtained from the same pair of antagonistic muscles. Therefore, a comprehensive assessment of the muscle strength capacity of the tested individual should be based on a single strength test and variable obtained from a number of different muscles, than on a single muscle tested through different tests and variables. The selected muscles should act in different limbs and joints, while the maximum isometric force should be the variable of choice.

  7. Muscle power predicts bone strength in Division II athletes.

    PubMed

    Yingling, Vanessa R; Webb, Shannon; Inouye, Cathy; O, Jenny; Sherwood, Jennifer J

    2017-08-29

    The relationship between muscle fitness measures and tibial bone strength in collegiate level athletes was investigated. Eighty-six Division II collegiate athletes (age: (18-29 years), height: 1.71 m (.09): mass: 66.7 kg (10.5) 56 female: 30 male) participated in this cross-sectional study. Maximum grip strength (GS), 1 repetition maximum leg press (1RM) and vertical jump peak power (PP) tests were measured. Cortical area (Ct.Ar), cortical bone mineral density (cBMD), moment of inertia (J) and bone strength (polar strength-strain index, SSIp) were measured using peripheral quantitative computed tomography (pQCT) at 50% tibia length. For each bone strength parameter, a hierarchical multiple regression (HMR) analysis was performed to examine the contribution of sex and the 3 muscle fitness parameters (muscle power, relative 1 repetition leg extensor strength and relative grip strength) to bone parameters. Vertical jump peak power explained 54-59% of the variance in bone strength parameters, and relative leg extensor and grip strength were not predictive of bone strength parameters. Muscle power correlated with bone mass and architecture variables but not cBMD values. Cortical bone mineral density (cBMD) was also not predicted by relative leg extensor strength or relative grip strength. Muscular fitness assessment, specifically peak power calculated from vertical jump height assessments provides a simple, objective, valid and reliable measure to identify and monitor bone strength in collegiate athletes.

  8. On cyclic yield strength in definition of limits for characterisation of fatigue and creep behaviour

    NASA Astrophysics Data System (ADS)

    Gorash, Yevgen; MacKenzie, Donald

    2017-06-01

    This study proposes cyclic yield strength as a potential characteristic of safe design for structures operating under fatigue and creep conditions. Cyclic yield strength is defined on a cyclic stress-strain curve, while monotonic yield strength is defined on a monotonic curve. Both values of strengths are identified using a two-step procedure of the experimental stress-strain curves fitting with application of Ramberg-Osgood and Chaboche material models. A typical S-N curve in stress-life approach for fatigue analysis has a distinctive minimum stress lower bound, the fatigue endurance limit. Comparison of cyclic strength and fatigue limit reveals that they are approximately equal. Thus, safe fatigue design is guaranteed in the purely elastic domain defined by the cyclic yielding. A typical long-term strength curve in time-to-failure approach for creep analysis has two inflections corresponding to the cyclic and monotonic strengths. These inflections separate three domains on the long-term strength curve, which are characterised by different creep fracture modes and creep deformation mechanisms. Therefore, safe creep design is guaranteed in the linear creep domain with brittle failure mode defined by the cyclic yielding. These assumptions are confirmed using three structural steels for normal and high-temperature applications. The advantage of using cyclic yield strength for characterisation of fatigue and creep strength is a relatively quick experimental identification. The total duration of cyclic tests for a cyclic stress-strain curve identification is much less than the typical durations of fatigue and creep rupture tests at the stress levels around the cyclic yield strength.

  9. Pulmonary Function, Muscle Strength, and Incident Mobility Disability in Elders

    PubMed Central

    Buchman, Aron S.; Boyle, Patricia A.; Leurgans, Sue E.; Evans, Denis A.; Bennett, David A.

    2009-01-01

    Muscle strength, including leg strength and respiratory muscle strength, are relatively independently associated with mobility disability in elders. However, the factors linking muscle strength with mobility disability are unknown. To test the hypothesis that pulmonary function mediates the association of muscle strength with the development of mobility disability in elders, we used data from a longitudinal cohort study of 844 ambulatory elders without dementia participating in the Rush Memory and Aging Project with a mean follow-up of 4.0 years (SD = 1.39). A composite measure of pulmonary function was based on spirometric measures of forced vital capacity, forced expiratory volume, and peak expiratory flow. Respiratory muscle strength was based on maximal inspiratory pressure and expiratory pressure and leg strength based on hand-held dynamometry. Mobility disability was defined as a gait speed less than or equal to 0.55 m/s based on annual assessment of timed walk. Secondary analyses considered time to loss of the ability to ambulate. In separate proportional hazards models which controlled for age, sex, and education, composite measures of pulmonary function, respiratory muscle strength, and leg strength were each associated with incident mobility disability (all P values < 0.001). Further, all three were related to the development of incident mobility disability when considered together in a single model (pulmonary function: hazard ratio [HR], 0.721; 95% confidence interval [CI], 0.577, 0.902; respiratory muscle strength: HR, 0.732; 95% CI, 0.593, 0.905; leg strength: HR, 0.791; 95% CI, 0.640, 0.976). Secondary analyses examining incident loss of the ability to ambulate revealed similar findings. Overall, these findings suggest that lower levels of pulmonary function and muscle strength are relatively independently associated with the development of mobility disability in the elderly. PMID:19934353

  10. Matching initial torque with different stimulation parameters influences skeletal muscle fatigue.

    PubMed

    Bickel, C Scott; Gregory, Chris M; Azuero, Andres

    2012-01-01

    A fundamental barrier to using electrical stimulation in the clinical setting is an inability to maintain torque production secondary to muscle fatigue. Electrical stimulation parameters are manipulated to influence muscle torque production, and they may also influence fatigability during repetitive stimulation. Our purpose was to determine the response of the quadriceps femoris to three different fatigue protocols using the same initial torque obtained by altering stimulator parameter settings. Participants underwent fatigue protocols in which either pulse frequency (lowHz), pulse duration (lowPD), or voltage (lowV) was manipulated to obtain an initial torque that equaled 25% of maximum voluntary isometric contraction. Muscle soreness was reported on a visual analog scale 48 h after each fatigue test. The lowHz protocol resulted in the least fatigue (25% +/- 14%); the lowPD (50% +/- 13%) and lowV (48% +/- 14%) protocols had similar levels of fatigue. The lowHz protocol resulted in significantly less muscle soreness than the higher frequency protocols. Stimulation protocols that use a lower frequency coupled with long pulse durations and high voltages result in lesser amounts of muscle fatigue and perceived soreness. The identification of optimal stimulation patterns to maximize muscle performance will reduce the effect of muscle fatigue and potentially improve clinical efficacy.

  11. 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.

  12. Effect of triceps surae and quadriceps muscle fatigue on the mechanics of landing in stepping down in ongoing gait.

    PubMed

    Barbieri, F A; Gobbi, L T B; Lee, Y J; Pijnappels, M; van Dieën, J H

    2014-01-01

    The aim of this study was to evaluate the effects of muscle fatigue of triceps surae and quadriceps muscles in stepping down in ongoing gait. We expected that the subjects would compensate for muscle fatigue to prevent potential loss of balance in stepping down. A total of 10 young participants walked over a walkway at a self-selected velocity to step down a height difference of 10-cm halfway. Five trials were performed before and after a muscle fatigue protocol. Participants performed two fatigue protocols: one for ankle muscle fatigue and another for knee muscle fatigue. Kinematics of and ground reaction forces on the leading leg were recorded. Fatigue did not cause a change in the frequency of heel or toe landing. Our results indicate that in stepping down fatigue effects are compensated by redistributing work to unfatigued muscle groups and by gait changes aimed at enhancing balance control, which was however only partially successful.

  13. Effectiveness of the Wavelet Transform on the Surface EMG to Understand the Muscle Fatigue During Walk

    NASA Astrophysics Data System (ADS)

    Hussain, M. S.; Mamun, Md.

    2012-01-01

    Muscle fatigue is the decline in ability of a muscle to create force. Electromyography (EMG) is a medical technique for measuring muscle response to nervous stimulation. During a sustained muscle contraction, the power spectrum of the EMG shifts towards lower frequencies. These effects are due to muscle fatigue. Muscle fatigue is often a result of unhealthy work practice. In this research, the effectiveness of the wavelet transform applied to the surface EMG (SEMG) signal as a means of understanding muscle fatigue during walk is presented. Power spectrum and bispectrum analysis on the EMG signal getting from right rectus femoris muscle is executed utilizing various wavelet functions (WFs). It is possible to recognize muscle fatigue appreciably with the proper choice of the WF. The outcome proves that the most momentous changes in the EMG power spectrum are symbolized by WF Daubechies45. Moreover, this research has compared bispectrum properties to the other WFs. To determine muscle fatigue during gait, Daubechies45 is used in this research to analyze the SEMG signal.

  14. Method to Reduce Muscle Fatigue During Transcutaneous Neuromuscular Electrical Stimulation in Major Knee and Ankle Muscle Groups.

    PubMed

    Sayenko, Dimitry G; Nguyen, Robert; Hirabayashi, Tomoyo; Popovic, Milos R; Masani, Kei

    2015-09-01

    A critical limitation with transcutaneous neuromuscular electrical stimulation as a rehabilitative approach is the rapid onset of muscle fatigue during repeated contractions. We have developed a method called spatially distributed sequential stimulation (SDSS) to reduce muscle fatigue by distributing the center of electrical field over a wide area within a single stimulation site, using an array of surface electrodes. To extend the previous findings and to prove feasibility of the method by exploring the fatigue-reducing ability of SDSS for lower limb muscle groups in the able-bodied population, as well as in individuals with spinal cord injury (SCI). SDSS was delivered through 4 active electrodes applied to the knee extensors and flexors, plantarflexors, and dorsiflexors, sending a stimulation pulse to each electrode one after another with 90° phase shift between successive electrodes. Isometric ankle torque was measured during fatiguing stimulations using SDSS and conventional single active electrode stimulation lasting 2 minutes. We demonstrated greater fatigue-reducing ability of SDSS compared with the conventional protocol, as revealed by larger values of fatigue index and/or torque peak mean in all muscles except knee flexors of able-bodied individuals, and in all muscles tested in individuals with SCI. Our study has revealed improvements in fatigue tolerance during transcutaneous neuromuscular electrical stimulation using SDSS, a stimulation strategy that alternates activation of subcompartments of muscles. The SDSS protocol can provide greater stimulation times with less decrement in mechanical output compared with the conventional protocol. © The Author(s) 2014.

  15. Trunk muscles strength and endurance in chronic low back pain patients with and without clinical instability.

    PubMed

    Davarian, Sanaz; Maroufi, Nader; Ebrahimi, Ismaeil; Farahmand, Farzam; Parnianpour, Mohammad

    2012-01-01

    Previous research has shown inconsistent findings regarding muscle endurance in chronic low back pain (CLBP). Questions also remain about muscle endurance in patients with clinical instability. The aim of this study was to investigate trunk muscles strength and endurance in CLBP patients with and without clinical instability. 32 CLBP patients (15 with and 17 without clinical instability) and 39 matched healthy subjects participated in this study. The standing extension test was performed to assess the strength and endurance of the lumbar extensors while recording their electromyographic activity. The patients' disability was evaluated using the Oswestry and Roland-Morris Disability Questionnaires. Patients with clinical instability showed lower maximal voluntary exertion (MVE) and higher time to fatigue (TTF) compared to healthy subjects (P=0.000 and P=0.008, respectively) and patients without instability (P=0.002 and P=0.02, respectively). There was no difference in these variables between patients without instability and healthy controls. A negative relationship between MVE and TTF and a positive correlation between disability and pain intensity were seen. Strength training of trunk extensor muscles can be considered as part of the treatment protocol for CLBP patients with clinical instability. Although patients without instability suffered from pain or disability, they showed more similarity to healthy subjects in terms of trunk muscles strength and endurance.

  16. Muscle Strength and Muscle Mass in Older Patients during Hospitalization: The EMPOWER Study.

    PubMed

    Van Ancum, Jeanine M; Scheerman, Kira; Pierik, Vincent D; Numans, Siger T; Verlaan, Sjors; Smeenk, Hanne E; Slee-Valentijn, Monique; Kruizinga, Roeliene C; Meskers, Carel G M; Maier, Andrea B

    2017-08-18

    Low muscle strength and muscle mass are associated with an increased length of hospital stay and higher mortality rate in inpatients. To what extent hospitalization affects muscle strength and muscle mass is unclear. We aimed to assess muscle strength and muscle mass at admission and during hospitalization in older patients and its relation with being at risk of geriatric conditions. The EMPOWER study included patients aged 70 years and older, admitted to 4 wards of the VU University Medical Center in the Netherlands between April and December 2015. At admission, patients were screened for being at risk of 4 geriatric conditions: delirium, falls, malnutrition, and functional disability. At admission and at discharge, muscle strength and muscle mass were assessed. A total of 373 patients (mean age, standard deviation [SD]: 79.6, 6.38 years) were included at admission, and 224 patients (mean age, SD: 80.1, 6.32 years) at discharge. At admission, lower muscle strength in both female and male patients and low muscle mass in male patients were associated with being at risk of a higher cumulative number of geriatric conditions. Muscle strength increased during hospitalization, but no change in muscle mass was observed. Changes in muscle measures were not associated with being at risk of geriatric conditions. Older patients with lower muscle strength and muscle mass at admission were at risk of a higher cumulative number of geriatric conditions. However, being at risk of geriatric conditions did not forecast further decrease in muscle strength and muscle mass during hospitalization. © 2017 The Author(s) Published by S. Karger AG, Basel.

  17. The relationship between exercise-induced muscle fatigue, arterial blood flow and muscle perfusion after 56 days local muscle unloading.

    PubMed

    Weber, Tobias; Ducos, Michel; Mulder, Edwin; Beijer, Åsa; Herrera, Frankyn; Zange, Jochen; Degens, Hans; Bloch, Wilhelm; Rittweger, Jörn

    2014-05-01

    In the light of the dynamic nature of habitual plantar flexor activity, we utilized an incremental isokinetic exercise test (IIET) to assess the work-related power deficit (WoRPD) as a measure for exercise-induced muscle fatigue before and after prolonged calf muscle unloading and in relation to arterial blood flow and muscle perfusion. Eleven male subjects (31 ± 6 years) wore the HEPHAISTOS unloading orthosis unilaterally for 56 days. It allows habitual ambulation while greatly reducing plantar flexor activity and torque production. Endpoint measurements encompassed arterial blood flow, measured in the femoral artery using Doppler ultrasound, oxygenation of the soleus muscle assessed by near-infrared spectroscopy, lactate concentrations determined in capillary blood and muscle activity using soleus muscle surface electromyography. Furthermore, soleus muscle biopsies were taken to investigate morphological muscle changes. After the intervention, maximal isokinetic torque was reduced by 23·4 ± 8·2% (P<0·001) and soleus fibre size was reduced by 8·5 ± 13% (P = 0·016). However, WoRPD remained unaffected as indicated by an unchanged loss of relative plantar flexor power between pre- and postexperiments (P = 0·88). Blood flow, tissue oxygenation, lactate concentrations and EMG median frequency kinematics during the exercise test were comparable before and after the intervention, whereas the increase of RMS in response to IIET was less following the intervention (P = 0·03). In conclusion, following submaximal isokinetic muscle work exercise-induced muscle fatigue is unaffected after prolonged local muscle unloading. The observation that arterial blood flow was maintained may underlie the unchanged fatigability.

  18. Cervical flexion-relaxation response to neck muscle fatigue in males and females.

    PubMed

    Nimbarte, Ashish D; Zreiqat, Majed M; Chowdhury, Suman Kanti

    2014-12-01

    In this study the effect of muscle fatigue on the cervical spine flexion-relaxation response was studied. Twenty healthy participants (10 males and 10 females) were recruited for data collection. The Sorenson protocol was utilized to induce neck muscle fatigue. Surface electromyography and optical motion capture systems were used to measure neck muscle activation and head-neck posture, respectively. A post-fatigue reduction in the Flexion-Relaxation Ratio (FRR) and higher FRR for females compared to males were observed. A post-fatigue decrease was also observed in the onset and offset angles resulting in an expansion of the myoelectric silence period. Gender had no effect on the onset and offset angles of the silence period. Post-fatigue shift in the onset and offset angles and the expansion of the silence period indicate an increased contribution by the passive viscoelastic tissues in stabilizing the cervical spine under fatigued condition.

  19. Effect of muscle acidity on muscle metabolism and fatigue during intense exercise in man.

    PubMed

    Bangsbo, J; Madsen, K; Kiens, B; Richter, E A

    1996-09-01

    1. The aim of this study was to examine the effect of muscle pH on muscle metabolism and development of fatigue during intense exercise. 2. Seven subjects performed intense exhaustive leg exercise on two occasions: with and without preceding intense intermittent arm exercise leading to high or moderate (control) blood lactate concentrations (HL and C, respectively). Prior to and immediately after each exercise bout, a muscle biopsy was taken from m. vastus lateralis of the active leg. Leg blood flow was measured and femoral arterial and venous blood samples were collected before and frequently during the exhaustive exercises. 3. The duration of the exercise was shorter in HL than in C (3.46 +/- 0.28 vs. 4.67 +/- 0.55 min; means +/- S.E.M.; P < 0.05). Before exercise muscle pH was the same in C and HL (7.17 vs. 7.10), but at the end of exercise muscle pH was lower in HL than in C (6.82 vs. 6.65; P < 0.05). The release of potassium during exercise was higher (P < 0.05) in HL compared with C, but the arterial and femoral venous plasma potassium concentrations were the same at exhaustion in HL and C. 4. Muscle lactate concentration was higher in HL compared with C (3.7 +/- 0.4 vs. 1.6 +/- 0.2 mmol (kg wet weight)-1; P < 0.05), but the same at exhaustion (26.5 +/- 2.7 vs. 25.4 +/- 2.4 mmol (kg wet weight)-1). Total release of lactate in HL was lower than in C (18.7 +/- 4.5 vs. 50.4 +/- 11.0 mmol; P < 0.05), but rate of lactate production was not different (9.0 +/- 1.0 vs. 10.2 +/- 1.3 mmol (kg wet weight)-1 min-1). The rate of muscle glycogen breakdown was the same in C and HL (8.1 +/- 1.2 vs. 8.2 +/- 1.0 mmol (kg wet weight)-1 min-1). 5. The present data suggest that elevated muscle acidity does not reduce muscle glycogenolysis/glycolysis and is not the only cause of fatigue during intense exercise in man. Instead, accumulation of potassium in muscle interstitium may be an important factor in the development of fatigue.

  20. Repeated-Sprint Cycling Does Not Induce Respiratory Muscle Fatigue in Active Adults: Measurements from The Powerbreathe® Inspiratory Muscle Trainer

    PubMed Central

    Minahan, Clare; Sheehan, Beth; Doutreband, Rachel; Kirkwood, Tom; Reeves, Daniel; Cross, Troy

    2015-01-01

    This study examined respiratory muscle strength using the POWERbreathe® inspiratory muscle trainer (i.e., ‘S-Index’) before and after repeated-sprint cycling for comparison with maximal inspiratory pressure (MIP) values obtained during a Mueller maneuver. The S-Index was measured during six trials across two sessions using the POWERbreathe® and MIP was measured during three trials in a single session using a custom-made manometer in seven recreationally active adults. Global respiratory muscle strength was measured using both devices before and after the performance of sixteen, 6-s sprints on a cycle ergometer. Intraclass correlation coefficients for the POWERbreathe® S-index indicated excellent (p < 0.05) trial-to-trial (r = 0.87) and day-to-day (r = 0.90) reliability yet there was no significant correlation (r = -0.35, p = 0.43) between the S-Index measured using the POWERbreathe® and MIP measured during a Mueller maneuver. Repeated-sprint cycling had no effect on respiratory muscle strength as measured by the POWERbreathe® (p > 0.99) and during the Mueller maneuver (p > 0.99). The POWERbreathe® S-Index is a moderately reliable, but not equivalent, measure of MIP determined during a Mueller maneuver. Furthermore, repeated-sprint cycling does not induce globalized respiratory muscle fatigue in recreationally-active adults. Key points The S-Index as measured by the POWERbreathe® is a reliable measure of respiratory muscle strength The S-Index does not accurately reflect maximal inspiratory pressure obtained from a Mueller maneuver Repeated-sprint cycling does not induce respiratory muscle fatigue as measured by the POWERbreathe® and the Manometer PMID:25729312

  1. Repeated-sprint cycling does not induce respiratory muscle fatigue in active adults: measurements from the powerbreathe® inspiratory muscle trainer.

    PubMed

    Minahan, Clare; Sheehan, Beth; Doutreband, Rachel; Kirkwood, Tom; Reeves, Daniel; Cross, Troy

    2015-03-01

    This study examined respiratory muscle strength using the POWERbreathe® inspiratory muscle trainer (i.e., 'S-Index') before and after repeated-sprint cycling for comparison with maximal inspiratory pressure (MIP) values obtained during a Mueller maneuver. The S-Index was measured during six trials across two sessions using the POWERbreathe® and MIP was measured during three trials in a single session using a custom-made manometer in seven recreationally active adults. Global respiratory muscle strength was measured using both devices before and after the performance of sixteen, 6-s sprints on a cycle ergometer. Intraclass correlation coefficients for the POWERbreathe® S-index indicated excellent (p < 0.05) trial-to-trial (r = 0.87) and day-to-day (r = 0.90) reliability yet there was no significant correlation (r = -0.35, p = 0.43) between the S-Index measured using the POWERbreathe® and MIP measured during a Mueller maneuver. Repeated-sprint cycling had no effect on respiratory muscle strength as measured by the POWERbreathe® (p > 0.99) and during the Mueller maneuver (p > 0.99). The POWERbreathe® S-Index is a moderately reliable, but not equivalent, measure of MIP determined during a Mueller maneuver. Furthermore, repeated-sprint cycling does not induce globalized respiratory muscle fatigue in recreationally-active adults. Key pointsThe S-Index as measured by the POWERbreathe® is a reliable measure of respiratory muscle strengthThe S-Index does not accurately reflect maximal inspiratory pressure obtained from a Mueller maneuverRepeated-sprint cycling does not induce respiratory muscle fatigue as measured by the POWERbreathe® and the Manometer.

  2. [Peripheral muscle strength in stable COPD patients: correlation with respiratory function variables and quality of life].

    PubMed

    Toral Marín, J; Ortega, F; Cejudo, P; Elías, T; Sánchez, H; Montemayor, T

    1999-03-01

    The aim of this study was to assess peripheral muscle strength in patients with chronic obstructive pulmonary disease (COPD) using a simple test and to look for correlation with function variables, physiological strength variables and quality of life parameters. Twenty-three COPD patients with moderate to severe air-flow limitation (FEV1 = 39 +/- 12%) in stable phase but displaying inability to carry out daily tasks were enrolled. Peripheral muscle strength was assessed in all patients by measuring the maximum load in a single repetition of five simple upper and lower extremity exercises performed at a multi-gymnastics station. Results were compared to respiratory function variables (FVC, FEV1, FEV1/FVC and gasometry), to results of an exercise test on a cycle ergometer with monitoring of respiratory gases (VEmax, VO2max and Wmax), to endurance (minutes) to dyspnea (Mahler's scale) and to quality of life (Chronic Respiratory Disease Questionnaire-CRDQ). No relation between functional parameters and endurance in minutes was found. Minute ventilation (VE) proved to be significantly related to oxygen intake (VO) and maximum work in the stress test. Dyspnea on Mahler's scale was unrelated, but fatigue variables and emotional function variables on the CRDQ were related. We conclude that peripheral muscle strength is unrelated to level of flow limitation or exercise tolerance in COPD patients. Peripheral muscle strength is related, however, to maximum work load and some aspects of quality of life.

  3. The Effectiveness of FES-Evoked EMG Potentials to Assess Muscle Force and Fatigue in Individuals with Spinal Cord Injury

    PubMed Central

    Ibitoye, Morufu Olusola; Estigoni, Eduardo H.; Hamzaid, Nur Azah; Wahab, Ahmad Khairi Abdul; Davis, Glen M.

    2014-01-01

    The evoked electromyographic signal (eEMG) potential is the standard index used to monitor both electrical changes within the motor unit during muscular activity and the electrical patterns during evoked contraction. However, technical and physiological limitations often preclude the acquisition and analysis of the signal especially during functional electrical stimulation (FES)-evoked contractions. Hence, an accurate quantification of the relationship between the eEMG potential and FES-evoked muscle response remains elusive and continues to attract the attention of researchers due to its potential application in the fields of biomechanics, muscle physiology, and rehabilitation science. We conducted a systematic review to examine the effectiveness of eEMG potentials to assess muscle force and fatigue, particularly as a biofeedback descriptor of FES-evoked contractions in individuals with spinal cord injury. At the outset, 2867 citations were identified and, finally, fifty-nine trials met the inclusion criteria. Four hypotheses were proposed and evaluated to inform this review. The results showed that eEMG is effective at quantifying muscle force and fatigue during isometric contraction, but may not be effective during dynamic contractions including cycling and stepping. Positive correlation of up to r = 0.90 (p < 0.05) between the decline in the peak-to-peak amplitude of the eEMG and the decline in the force output during fatiguing isometric contractions has been reported. In the available prediction models, the performance index of the eEMG signal to estimate the generated muscle force ranged from 3.8% to 34% for 18 s to 70 s ahead of the actual muscle force generation. The strength and inherent limitations of the eEMG signal to assess muscle force and fatigue were evident from our findings with implications in clinical management of spinal cord injury (SCI) population. PMID:25025551

  4. Influence of different breathing frequencies on the severity of inspiratory muscle fatigue induced by high-intensity front crawl swimming.

    PubMed

    Jakovljevic, Djordje G; McConnell, Alison K

    2009-07-01

    The aim of the present study was to assess the influence of 2 different breathing frequencies on the magnitude of inspiratory muscle fatigue after high-intensity front crawl swimming. The influence of different breathing frequencies on postexercise blood lactate ([La]) and heart rate (HR) was also examined. Ten collegiate swimmers performed 2 x 200-m front crawl swims at 90% of race pace with the following breathing frequencies: 1) 1 breath every second stroke (B2), and 2) 1 breath every fourth stroke (B4). Maximal inspiratory pressure (PImax) was measured at the mouth from residual volume before (baseline) and after swimming, in a standing position. The HR and [La] were assessed at rest and immediately at the cessation of swimming. The PImax decreased by 21% after B4 and by 11% after B2 compared with baseline (p < 0.05). The [La] was lower by 15% after B4 than after B2 (p < 0.05). The HR was not significantly different between B2 and B4. These data suggest that there is significant global inspiratory muscle fatigue after high-intensity swimming. Inspiratory muscle fatigue is, however, greater when breathing frequency is reduced during high-intensity front crawl swimming. Respiratory muscle training should be used to improve respiratory muscle strength and endurance in swimmers.

  5. Progressive resistance muscle strength training of hospitalized frail elderly.

    PubMed

    Sullivan, D H; Wall, P T; Bariola, J R; Bopp, M M; Frost, Y M

    2001-07-01

    To determine whether frail elderly patients recuperating from acute illnesses could safely participate in and gain appreciable improvement in muscle strength from progressive resistance muscle strength training. Muscle strength (one repetition maximum), functional abilities (sit-to-stand maneuver and 20-sec maximal safe gait speed), and body composition were measured before and at the conclusion of a 10-wk program of lower limb progressive resistance muscle strength training. The nonrandomized study was conducted in a 30-bed geriatric rehabilitation unit of a university-affiliated Veterans Affairs hospital and a 28-bed transitional care unit of a community nursing home. Participants included 19 recuperating elderly subjects (14 male, 5 female; 13 ambulatory, 6 nonambulatory) >64 yr (mean age, 82.8+/-7.9 yr). The one repetition maximum increased an average of 74%+/-49% (median, 70%; interquartile range, 38%-95%, and an average of 20+/-13 kg (P = 0.0001). Sit-to-stand maneuver times improved in 15 of 19 cases (79%). Maximum safe gait speeds improved in 10 of 19 cases (53%). Four of the six nonambulatory subjects progressed to ambulatory status. No subject experienced a complication. A carefully monitored program of progressive resistance muscle strength training to regain muscle strength is a safe and possibly effective method for frail elderly recuperating from acute illnesses. A randomized control study is needed to examine the degree to which progressive resistance muscle strength training offers advantages, if any, over routine posthospital care that includes traditional low-intensity physical therapy.

  6. Effects of Respiratory Muscle Strength Training in Classically Trained Singers.

    PubMed

    Ray, Christin; Trudeau, Michael D; McCoy, Scott

    2017-09-25

    Many voice pedagogy practices revolve around the notion of controlling airflow and lung volumes and focus heavily on the concepts of breath support and breath control. Despite this emphasis, the effects of increased respiratory muscle strength on airflow and phonation patterns in trained singers remain unknown. This study addressed whether singers could increase respiratory muscle strength with progressive threshold training and whether respiratory muscle strength increases had measurable effect on voice outcomes. A single-subject design was used to answer the research questions. Improved breath support was hypothesized to manifest in differences in airflow and phonetogram characteristics. Six graduate-level singing students were recruited to complete the protocol, which consisted of a baseline phase followed by either inspiratory muscle strength training followed by expiratory muscle strength training or vice versa. Results showed that these singers had increased respiratory muscle strength after completing the training program. Consistent changes in measures of aerodynamics and voice were not present among subjects, although some individual changes were noted. Future research may focus on the effects of respiratory muscle strength training in less advanced singers. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  7. Assessment of Fatigue and Recovery in Male and Female Athletes After 6 Days of Intensified Strength Training.

    PubMed

    Raeder, Christian; Wiewelhove, Thimo; Simola, Rauno Álvaro De Paula; Kellmann, Michael; Meyer, Tim; Pfeiffer, Mark; Ferrauti, Alexander

    2016-12-01

    Raeder, C, Wiewelhove, T, Simola, RÁDP, Kellmann, M, Meyer, T, Pfeiffer, M, and Ferrauti, A. Assessment of fatigue and recovery in male and female athletes after 6 days of intensified strength training. J Strength Cond Res 30(12): 3412-3427, 2016-This study aimed to analyze changes of neuromuscular, physiological, and perceptual markers for routine assessment of fatigue and recovery in high-resistance strength training. Fourteen male and 9 female athletes participated in a 6-day intensified strength training microcycle (STM) designed to purposefully overreach. Maximal dynamic strength (estimated 1 repetition maximum [1RMest]; criterion measure of fatigue and recovery); maximal voluntary isometric strength (MVIC); countermovement jump (CMJ) height; multiple rebound jump (MRJ) height; jump efficiency (reactive strength index, RSI); muscle contractile properties using tensiomyography including muscle displacement (Dm), delay time (Td), contraction time (Tc), and contraction velocity (V90); serum concentration of creatine kinase (CK); perceived muscle soreness (delayed-onset muscle soreness, DOMS) and perceived recovery (physical performance capability, PPC); and stress (MS) were measured before and after the STM and after 3 days of recovery. After completing the STM, there were significant (p ≤ 0.05) performance decreases in 1RMest (%[INCREMENT] ± 90% confidence limits, ES = effect size; -7.5 ± 3.5, ES = -0.21), MVIC (-8.2 ± 4.9, ES = -0.24), CMJ (-6.4 ± 2.1, ES = -0.34), MRJ (-10.5 ± 3.3, ES = -0.66), and RSI (-11.2 ± 3.8, ES = -0.73), as well as significantly reduced muscle contractile properties (Dm, -14.5 ± 5.3, ES = -0.60; V90, -15.5 ± 4.9, ES = -0.62). After days of recovery, a significant return to baseline values could be observed in 1RMest (4.3 ± 2.8, ES = 0.12), CMJ (5.2 ± 2.2, ES = 0.28), and MRJ (4.9 ± 3.8, ES = 0.32), whereas RSI (-7.9 ± 4.5, ES = -0.50), Dm (-14.7 ± 4.8, ES = -0.61), and V90 (-15.3 ± 4.7, ES = -0.66) remained

  8. Investigation of fatigue strength of multilayer advanced fiber composites

    NASA Technical Reports Server (NTRS)

    Thornton, H. R.; Kozik, T. J.

    1974-01-01

    The analytical characterization of a multilayer fiber composite plate (without hole) was accomplished for both static and dynamic loading conditions using the finite difference technique. Thornel 300/5208 composites with and without holes were subjected to static and tensile fatigue testing. Five (5) fiber orientations were submitted to test. Tensile fatigue testing also included three (3) loading conditions and two (2) frequencies. The low-cycle test specimens demonstrated a shorter tensile fatigue life than the high-cycle test specimens. Failure surfaces demonstrated effect of testing conditions. Secondary failure mechanisms, such as: delamination, fiber breakage, and edge fiber delamination were present. Longitudinal delamination between plies also occurred in these specimens.

  9. Effectiveness of sulfur-containing antioxidants in delaying skeletal muscle fatigue.

    PubMed

    Ferreira, Leonardo F; Campbell, Kenneth S; Reid, Michael B

    2011-06-01

    Reactions involving thiol biochemistry seem to play a crucial role in skeletal muscle fatigue. N-acetylcysteine amide (NACA) and L-ergothioneine (ERGO) are thiol-based antioxidants available for human use that have not been evaluated for effects on muscle fatigue. To test the hypothesis that NACA and ERGO delay skeletal muscle fatigue. We exposed mouse diaphragm fiber bundles to buffer (CTRL), NACA, ERGO, or N-acetylcysteine (NAC; positive control). Treatments were performed in vitro using 10 mM for 60 min at 37 °C. After treatment, we determined the muscle force-frequency and fatigue characteristics. The force-frequency relationship was shifted to the left by ERGO and to the right by NACA compared with CTRL and NAC. Maximal tetanic force was similar among groups. The total force-time integral (FTI; N · s · cm) during the fatigue trial was decreased by NACA (420 ± 35, P < 0.05), unaffected by ERGO (657 ± 53), and increased by NAC (P < 0.05) compared with CTRL (581 ± 54). The rate of contraction (dF/dtMAX) during the fatigue trial was not affected by any of the treatments tested. NAC, but not NACA or ERGO, delayed the slowing of muscle relaxation (dF/dtMIN) during fatigue. In summary, NACA and ERGO did not delay skeletal muscle fatigue in vitro. We conclude that these antioxidants are unlikely to improve human exercise performance.

  10. Effects of lower extremity muscle fatigue on the outcomes of slip-induced falls

    PubMed Central

    Parijat, Prakriti; Lockhart, Thurmon E.

    2010-01-01

    Slip-induced fall accidents continue to be a significant cause of fatal injuries and economic losses. Identifying the risk factors causing slip-induced falls is key to developing better preventive measures to reduce fall accidents. Although epidemiological studies suggest localised muscle fatigue may be one of the risk factors for slip-induced falls, there has been no documented biomechanical study examining the relationship between fatigue and fall accidents. As such, the overall objective of the current study was to investigate the effects of localised muscle fatigue of the quadriceps on the slip initiation and slip recovery phases of slip-induced falls. Sixteen healthy, young participants were recruited to walk across a vinyl floor surface in two different sessions (fatigue and no fatigue). Kinematic and kinetic data were collected using a 3-D motion analysis system and force plates during both sessions. Results suggest that localised muscle fatigue of the quadriceps affected various kinematic and kinetic gait variables that are linked with a higher risk of slip-induced falls. Additionally, the results indicated that localised muscle fatigue of the knee extensor muscle caused a delayed response in producing an effective joint moment and base of support using the trailing limb to recover from a fall. The findings from this study indicate that localised muscle fatigue is a potential risk factor causing slip-induced falls. PMID:19034783

  11. Effects of lower extremity muscle fatigue on the outcomes of slip-induced falls.

    PubMed

    Parijat, Prakriti; Lockhart, Thurmon E

    2008-12-01

    Slip-induced fall accidents continue to be a significant cause of fatal injuries and economic losses. Identifying the risk factors causing slip-induced falls is key to developing better preventive measures to reduce fall accidents. Although epidemiological studies suggest localised muscle fatigue may be one of the risk factors for slip-induced falls, there has been no documented biomechanical study examining the relationship between fatigue and fall accidents. As such, the overall objective of the current study was to investigate the effects of localised muscle fatigue of the quadriceps on the slip initiation and slip recovery phases of slip-induced falls. Sixteen healthy, young participants were recruited to walk across a vinyl floor surface in two different sessions (fatigue and no fatigue). Kinematic and kinetic data were collected using a 3-D motion analysis system and force plates during both sessions. Results suggest that localised muscle fatigue of the quadriceps affected various kinematic and kinetic gait variables that are linked with a higher risk of slip-induced falls. Additionally, the results indicated that localised muscle fatigue of the knee extensor muscle caused a delayed response in producing an effective joint moment and base of support using the trailing limb to recover from a fall. The findings from this study indicate that localised muscle fatigue is a potential risk factor causing slip-induced falls.

  12. Relation between hand grip strength, respiratory muscle strength and spirometric measures in male nursing home residents.

    PubMed

    Bahat, Gulistan; Tufan, Asli; Ozkaya, Hilal; Tufan, Fatih; Akpinar, Timur Selçuk; Akin, Sibel; Bahat, Zumrut; Kaya, Zuleyha; Kiyan, Esen; Erten, Nilgün; Karan, Mehmet Akif

    2014-09-01

    Adverse-outcomes related to sarcopenia are mostly mentioned as physical disability. As the other skeletal muscles, respiratory muscles may also be affected by sarcopenia. Respiratory muscle strength is known to affect pulmonary functions. Therefore, we aimed to investigate the relations between extremity muscle strength, respiratory muscle strengths and spirometric measures in a group of male nursing home residents. Among a total of 104 male residents, residents with obstructive measures were excluded and final study population was composed of 62 residents. Mean age was 70.5 ± 6.7 years, body mass index: 27.7 ± 5.3 kg/m2 and dominant hand grip strength: 29.7 ± 6.5 kg. Hand grip strength was positively correlated with maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) (r = 0.35, p < 0.01 and r = 0.26, p < 0.05, respectively). In regression analysis, the only factor related to MIP was hand grip strength; among spirometric measures only parameter significantly related to grip strength was peak cough flow (PCF). The association of PCF with grip strength disappeared when MIP alone or "MIP and MEP" were included in the regression analysis. In the latter case, PCF was significantly associated only with MIP. We found peripheric muscle strength be associated with MIP and PCF but not with MEP or any other spirometric parameters. The relation between peripheral muscle strength and PCF was mediated by MIP. Our findings suggest that sarcopenia may affect inspiratory muscle strength earlier or more than the expiratory muscle strength. Sarcopenia may cause decrease in PCF in the elderly, which may stand for some common adverse respiratory complications.

  13. Fatigue of Austempered Ductile Iron with Two Strength Grades in Very High Cycle Regime

    NASA Astrophysics Data System (ADS)

    Zhang, Jiwang; Li, Wei; Song, Qingpeng; Zhang, Ning; Lu, Liantao

    2016-03-01

    In this study, Austempered ductile irons (ADIs) with two different strength grades were produced and the fatigue properties were measured at 109 cycles. The results show that the S-N curves give a typical step-wise shape and there is no fatigue limit in the very high cycle fatigue regime. The two grades ADI have the similar fracture behaviors and fatigue failure can initiate from defects at specimen surface and subsurface zone. On the fracture surfaces of some specimens, the `granular-bright-facet' area with rich carbon distribution is observed in the vicinity of the defect. The microstructure affects the crack behaviors at the early propagation stage. The ADI with upper and lower bainite shows higher fatigue strength compared with the ADI with coarse upper bainite.

  14. C60 fullerene as promising therapeutic agent for correcting and preventing skeletal muscle fatigue.

    PubMed

    Prylutskyy, Yurij I; Vereshchaka, Inna V; Maznychenko, Andriy V; Bulgakova, Nataliya V; Gonchar, Olga O; Kyzyma, Olena A; Ritter, Uwe; Scharff, Peter; Tomiak, Tomasz; Nozdrenko, Dmytro M; Mishchenko, Iryna V; Kostyukov, Alexander I

    2017-01-13

    Bioactive soluble carbon nanostructures, such as the C60 fullerene can bond with up to six electrons, thus serving by a powerful scavenger of reactive oxygen species similarly to many natural antioxidants, widely used to decrease the muscle fatigue effects. The aim of the study is to define action of the pristine C60 fullerene aqueous colloid solution (C60FAS), on the post-fatigue recovering of m. triceps surae in anaesthetized rats. During fatigue development, we observed decrease in the muscle effort level before C60FAS administration. After the application of C60FAS, a slower effort decrease, followed by the prolonged retention of a certain level, was recorded. An analysis of the metabolic process changes accompanying muscle fatigue showed an increase in the oxidative stress markers H 2 O 2 (hydrogen peroxide) and TBARS (thiobarbituric acid reactive substances) in relation to the intact muscles. After C60FAS administration, the TBARS content and H 2 O 2 level were decreased. The endogenous antioxidant system demonstrated a similar effect because the GSH (reduced glutathione) in the muscles and the CAT (catalase) enzyme activity were increased during fatigue. C60FAS leads to reduction in the recovery time of the muscle contraction force and to increase in the time of active muscle functioning before appearance of steady fatigue effects. Therefore, it is possible that C60FAS affects the prooxidant-antioxidant muscle tissue homeostasis, subsequently increasing muscle endurance.

  15. Effect of stress concentration on the fatigue strength of A7N01S-T5 welded joints

    NASA Astrophysics Data System (ADS)

    Zhang, Mingyue; Gou, Guoqing; Hang, Zongqiu; Chen, Hui

    2017-07-01

    Stress concentration is a key factor that affects the fatigue strength of welded joints. In this study, the fatigue strengths of butt joints with and without the weld reinforcement were tested to quantify the effect of stress concentration. The fatigue strength of the welded joints was measured with a high-frequency fatigue machine. The P-S-N curves were drawn under different confidence levels and failure probabilities. The results show that butt joints with the weld reinforcement have much lower fatigue strength than joints without the weld reinforcement. Therefore, stress concentration introduced by the weld reinforcement should be controlled.

  16. Influence of Lumbar Muscle Fatigue on Trunk Adaptations during Sudden External Perturbations

    PubMed Central

    Abboud, Jacques; Nougarou, François; Lardon, Arnaud; Dugas, Claude; Descarreaux, Martin

    2016-01-01

    Introduction: When the spine is subjected to perturbations, neuromuscular responses such as reflex muscle contractions contribute to the overall balance control and spinal stabilization mechanisms. These responses are influenced by muscle fatigue, which has been shown to trigger changes in muscle recruitment patterns. Neuromuscular adaptations, e.g., attenuation of reflex activation and/or postural oscillations following repeated unexpected external perturbations, have also been described. However, the characterization of these adaptations still remains unclear. Using high-density electromyography (EMG) may help understand how the nervous system chooses to deal with an unknown perturbation in different physiological and/or mechanical perturbation environments. Aim: To characterize trunk neuromuscular adaptations following repeated sudden external perturbations after a back muscle fatigue task using high-density EMG. Methods: Twenty-five healthy participants experienced a series of 15 sudden external perturbations before and after back muscle fatigue. Erector spinae muscle activity was recorded using high-density EMG. Trunk kinematics during perturbation trials were collected using a 3-D motion analysis system. A two-way repeated measure ANOVA was conducted to assess: (1) the adaptation effect across trials; (2) the fatigue effect; and (3) the interaction effect (fatigue × adaptation) for the baseline activity, the reflex latency, the reflex peak and trunk kinematic variables (flexion angle, velocity and time to peak velocity). Muscle activity spatial distribution before and following the fatigue task was also compared using t-tests for dependent samples. Results: An attenuation of muscle reflex peak was observed across perturbation trials before the fatigue task, but not after. The spatial distribution of muscle activity was significantly higher before the fatigue task compared to post-fatigue trials. Baseline activity showed a trend to higher values after muscle

  17. Influence of Lumbar Muscle Fatigue on Trunk Adaptations during Sudden External Perturbations.

    PubMed

    Abboud, Jacques; Nougarou, François; Lardon, Arnaud; Dugas, Claude; Descarreaux, Martin

    2016-01-01

    Introduction: When the spine is subjected to perturbations, neuromuscular responses such as reflex muscle contractions contribute to the overall balance control and spinal stabilization mechanisms. These responses are influenced by muscle fatigue, which has been shown to trigger changes in muscle recruitment patterns. Neuromuscular adaptations, e.g., attenuation of reflex activation and/or postural oscillations following repeated unexpected external perturbations, have also been described. However, the characterization of these adaptations still remains unclear. Using high-density electromyography (EMG) may help understand how the nervous system chooses to deal with an unknown perturbation in different physiological and/or mechanical perturbation environments. Aim: To characterize trunk neuromuscular adaptations following repeated sudden external perturbations after a back muscle fatigue task using high-density EMG. Methods: Twenty-five healthy participants experienced a series of 15 sudden external perturbations before and after back muscle fatigue. Erector spinae muscle activity was recorded using high-density EMG. Trunk kinematics during perturbation trials were collected using a 3-D motion analysis system. A two-way repeated measure ANOVA was conducted to assess: (1) the adaptation effect across trials; (2) the fatigue effect; and (3) the interaction effect (fatigue × adaptation) for the baseline activity, the reflex latency, the reflex peak and trunk kinematic variables (flexion angle, velocity and time to peak velocity). Muscle activity spatial distribution before and following the fatigue task was also compared using t-tests for dependent samples. Results: An attenuation of muscle reflex peak was observed across perturbation trials before the fatigue task, but not after. The spatial distribution of muscle activity was significantly higher before the fatigue task compared to post-fatigue trials. Baseline activity showed a trend to higher values after muscle

  18. Notch fatigue behavior: Metallic glass versus ultra-high strength steel.

    PubMed

    Wang, X D; Qu, R T; Wu, S J; Duan, Q Q; Liu, Z Q; Zhu, Z W; Zhang, H F; Zhang, Z F

    2016-10-18

    Studying the effect of notch on the fatigue behavior of structural materials is of significance for the reliability and safety designing of engineering structural components. In this work, we conducted notch fatigue experiments of two high-strength materials, i.e. a Ti32.8Zr30.2Ni5.3Cu9Be22.7 metallic glass (MG) and a 00Ni18Co15Mo8Ti ultra-high strength steel (CM400 UHSS), and compared their notch fatigue behavior. Experimental results showed that although both the strength and plasticity of the MG were much lower than those of the UHSS, the fatigue endurance limit of the notched MG approached to that of the notched UHSS, and the fatigue ratio of the notched MG was even higher. This interesting finding can be attributed to the unique shear banding mechanism of MG. It was found that during fatigue process abundant shear bands formed ahead of the notch root and in the vicinity of the crack in the notched MG, while limited plastic deformation was observed in the notched UHSS. The present results may improve the understanding on the fatigue mechanisms of high-strength materials and offer new strategies for structural design and engineering application of MG components with geometrical discontinuities.

  19. Notch fatigue behavior: Metallic glass versus ultra-high strength steel

    PubMed Central

    Wang, X. D.; Qu, R. T.; Wu, S. J.; Duan, Q. Q.; Liu, Z. Q.; Zhu, Z. W.; Zhang, H. F.; Zhang, Z. F.

    2016-01-01

    Studying the effect of notch on the fatigue behavior of structural materials is of significance for the reliability and safety designing of engineering structural components. In this work, we conducted notch fatigue experiments of two high-strength materials, i.e. a Ti32.8Zr30.2Ni5.3Cu9Be22.7 metallic glass (MG) and a 00Ni18Co15Mo8Ti ultra-high strength steel (CM400 UHSS), and compared their notch fatigue behavior. Experimental results showed that although both the strength and plasticity of the MG were much lower than those of the UHSS, the fatigue endurance limit of the notched MG approached to that of the notched UHSS, and the fatigue ratio of the notched MG was even higher. This interesting finding can be attributed to the unique shear banding mechanism of MG. It was found that during fatigue process abundant shear bands formed ahead of the notch root and in the vicinity of the crack in the notched MG, while limited plastic deformation was observed in the notched UHSS. The present results may improve the understanding on the fatigue mechanisms of high-strength materials and offer new strategies for structural design and engineering application of MG components with geometrical discontinuities. PMID:27752136

  20. Notch fatigue behavior: Metallic glass versus ultra-high strength steel

    NASA Astrophysics Data System (ADS)

    Wang, X. D.; Qu, R. T.; Wu, S. J.; Duan, Q. Q.; Liu, Z. Q.; Zhu, Z. W.; Zhang, H. F.; Zhang, Z. F.

    2016-10-01

    Studying the effect of notch on the fatigue behavior of structural materials is of significance for the reliability and safety designing of engineering structural components. In this work, we conducted notch fatigue experiments of two high-strength materials, i.e. a Ti32.8Zr30.2Ni5.3Cu9Be22.7 metallic glass (MG) and a 00Ni18Co15Mo8Ti ultra-high strength steel (CM400 UHSS), and compared their notch fatigue behavior. Experimental results showed that although both the strength and plasticity of the MG were much lower than those of the UHSS, the fatigue endurance limit of the notched MG approached to that of the notched UHSS, and the fatigue ratio of the notched MG was even higher. This interesting finding can be attributed to the unique shear banding mechanism of MG. It was found that during fatigue process abundant shear bands formed ahead of the notch root and in the vicinity of the crack in the notched MG, while limited plastic deformation was observed in the notched UHSS. The present results may improve the understanding on the fatigue mechanisms of high-strength materials and offer new strategies for structural design and engineering application of MG components with geometrical discontinuities.

  1. [Progress on cervical muscle strength and soft tissue stiffness testing].

    PubMed

    Ma, Ming; Zhang, Shi-min

    2015-08-01

    Biomechanical evaluation of neck muscles has important significance in the diagnosis and treatment for cervical spondylosis, the neck muscle strength and soft tissue stiffness test is two aspects of biomechanical testing. Isometric muscle testing operation is relatively simple, the cost is lower, which can evaluate the muscle force below grade 3. However, isokinetic muscle strength testing can assess the muscle strength of joint motion in any position. It is hard to distinguish stiffness difference in different soft tissues when the load-displacement curve is used to evaluate the local soft tissue stiffness. Elasticity imaging technique can not only show the elastic differences of different tissues by images, but also quantify the elastic modulus of subcutaneous tissues and muscles respectively. Nevertheless, it is difficult to observe the flexibility of the cervical spine by means of the analysis of the whole neck stiffness. In a word, a variety of test method will conduce not only the biomechanical evaluation of neck muscles, but also making an effective biomechanics mathematical model of neck muscles. Besides, isokinetic muscle testing and the elasticity imaging technology still need further validation and optimization before they are better applied to neck muscles biomechanical testing.

  2. Evaluation of rotator cuff muscle strength in healthy individuals

    PubMed Central

    Cortez, Paulo José Oliveira; Tomazini, José Elias

    2015-01-01

    OBJECTIVE: To compare the strength generated by the rotator muscles of the shoulder joint between the right upper limb and left upper limb among healthy individuals. METHODS: To evaluate the muscle strength of upper limbs from isometric contractions in the horizontal direction (rotation) an isometric dynamometer was used, equipped with transducers, signal conditioning, a data acquisition board, and finally, a computer. Study participants were 22 male military subjects, aged between 18 and 19 years old, body mass between 57.7 and 93.0 kg (71.8 ± 9.45 kg) and height between 1.67 and 1.90 m (1.75 ± 0.06 m), healthy and without clinical diseases or any type of orthopedic injury in the muscle skeletal system. RESULTS: The internal rotation in the right upper limb (RUL) was higher than the average strength of internal rotation in the left upper limb (LUL) (p = 0.723). The external rotation strength in RUL was lower than the average strength of external rotation in the LUL (p=0.788). No statistical difference was observed by comparing the strength values of all isometric strength tests. CONCLUSION: For the sample and methodology used to assess muscle strength, there was no statistical difference between the strength generated by the muscles of the rotator cuff of the right and left upper limbs. Experimental Study. PMID:26207091

  3. The effect of isokinetic exercise on the relationship between blood lactate and muscle fatigue.

    PubMed

    Douris, P C

    1993-01-01

    Exercise velocity may be an important variable in determining the amount of blood lactate accumulation during isokinetic exercise. The purpose of this study was to measure the effects of velocity-specific isokinetic exercise on blood lactate, muscle fatigue index, and rating of perceived exertion and to examine the relationship between blood lactate and muscle fatigue index. Ten experienced recreational weight trainers, aged 20-40 years, took part in a repeated measures design consisting of three separate treatments (constant angular velocity at 30, 120, and 300 degrees/sec performed at maximal effort for 1 minute by the right knee flexors and extensors). Rating of perceived exertion, blood lactate, and muscle fatigue index were measured in response to each treatment. Rating of perceived exertion was equal across all three speeds. Muscle fatigue and blood lactate increased significantly as the velocity of exercise increased. There was also a positive correlation coefficient (r = .82, < or = 0.01) between muscle fatigue index and blood lactate. The data suggested that the magnitude of muscle fatigue index and blood lactate responses are strongly dependent on the velocity of movement utilized during maximal isokinetic exercise, and there is a relationship between muscle fatigue index and blood lactate.

  4. A comparison of inspiratory muscle fatigue following maximal exercise in moderately trained males and females.

    PubMed

    Ozkaplan, Atila; Rhodes, Edward C; Sheel, A William; Taunton, Jack E

    2005-09-01

    Exercise-induced inspiratory muscle fatigue (IMF) has been reported in males but there are few reports of IMF in females. It is not known if a gender difference exists for inspiratory muscle strength following heavy exercise, as is reported in locomotor muscles. Therefore, the relationship between fatigue and subsequent recovery of maximal inspiratory pressure (MIP) following exercise to maximal oxygen consumption (VO2max) was examined in a group of moderately trained males and females. Eighteen males (23+/-3 years; mean +/- SD) and 16 females (23+/-2 years) completed ten MIP and ten maximal handgrip (HG) strength maneuvers to establish baseline. Post-exercise MIP and HG were assessed successively immediately following a progressive intensity VO2max test on a cycle ergometer and at 1, 2, 3, 4, 5, 10, and 15 min. VO2max, relative to fat-free mass was not statistically different between males (62+/-7 ml kg(-1) min(-1)) and females (60+/-8 ml kg(-1) min(-1)). Males had higher absolute MIP values than females at all time intervals (P<0.05). Immediately following exercise, MIP was significantly reduced in both genders (M=83+/-16%; F=78+/-15% of baseline) but HG values were not different than resting values. MIP values remained depressed for both males and females throughout the 15 min (P<0.05). Differences for MIP between males and females were not statistically significant at any measurement time (P>0.05). The findings in this study conclude that IMF, observed immediately following maximal exercise, demonstrated the same pattern of recovery for both genders.

  5. Muscle strength, muscle mass, and physical disability in women with systemic lupus erythematosus.

    PubMed

    Andrews, James S; Trupin, Laura; Schmajuk, Gabriela; Barton, Jennifer; Margaretten, Mary; Yazdany, Jinoos; Yelin, Edward H; Katz, Patricia P

    2015-01-01

    Data describing relationships between muscle strength, muscle mass, and physical disability among individuals with systemic lupus erythematosus (SLE) are limited. The present study examines the relationship of muscle strength and muscle mass with physical disability among adult women with SLE. A total of 146 women from a longitudinal SLE cohort participated in the study. All measures were collected during an in-person research visit. Lower extremity muscle strength was assessed by peak knee torque of extension and flexion and by chair-stand time. Total lean body mass, appendicular lean mass, and fat mass (kg/m(2) ) were measured by whole-body dual x-ray absorptiometry. Self-reported physical disability was assessed using the Short Form 36 health survey (SF-36) physical functioning subscale, and the Valued Life Activities (VLA) disability scale. Spearman's rank correlation coefficients tested the correlations between muscle strength, muscle mass, and disability scores. Regression analyses modeled the effect of lower extremity muscle strength and mass on SF-36 and VLA disability scores controlling for age, SLE duration, SLE disease activity measured with the Systemic Lupus Activity Questionnaire, physical activity level, prednisone use, body composition, and depression. On all measures, reduced lower extremity muscle strength was associated with poorer SF-36 and VLA disability scores. Trends persisted after adjustment for covariates. Muscle mass was moderately correlated with muscle strength, but did not contribute significantly to adjusted regression models. Lower extremity muscle strength, but not muscle mass, was strongly associated with physical disability scores. While further studies are needed, these findings suggest that improving muscle strength may reduce physical disability among women with SLE. Copyright © 2015 by the American College of Rheumatology.

  6. Muscle Strength, Muscle Mass, and Physical Disability in Women with Systemic Lupus Erythematosus

    PubMed Central

    Andrews, James S.; Trupin, Laura; Schmajuk, Gabriela; Barton, Jennifer; Margaretten, Mary; Yazdany, Jinoos; Yelin, Edward H.; Katz, Patricia P.

    2014-01-01

    Objective Limited data exist describing relationships between muscle strength, muscle mass, and physical disability among individuals with systemic lupus erythematosus (SLE). The present study examines the relationship of muscle strength and muscle mass with physical disability among adult women with SLE. Methods One hundred forty-six women from a longitudinal SLE cohort participated in the study. All measures were collected during an in-person research visit. Lower extremity muscle strength was assessed by peak knee torque of extension and flexion and by chair-stand time. Total lean body mass, appendicular lean mass, and fat mass (kg/m2) were measured by whole-body dual energy absorptiometry. Self-reported physical disability was assessed using the SF-36 Physical Functioning subscale and Valued Life Activities (VLA) Disability scale. Spearman’s rank correlation coefficients tested the correlations between muscle strength, muscle mass, and disability scores. Regression analyses modeled the effect of lower extremity muscle strength and mass on SF-36 and VLA disability scores controlling for age, SLE duration, SLE disease activity measured with the Systemic Lupus Activity Questionnaire (SLAQ), physical activity level, prednisone use, body composition, and depression. Results On all measures, reduced lower extremity muscle strength was associated with poorer SF-36 and VLA disability scores. Trends persisted after adjustment for covariates. Muscle mass was moderately correlated with muscle strength, but did not contribute significantly to adjusted regression models. Conclusions Lower extremity muscle strength, but not muscle mass, was strongly associated with physical disability scores. While further studies are needed, these findings suggest that improving muscle strength may reduce physical disability among women with SLE. PMID:25049114

  7. Potassium, Na+,K+-pumps and fatigue in rat muscle.

    PubMed

    Clausen, Torben; Nielsen, Ole Baekgaard

    2007-10-01

    During contractile activity, skeletal muscles undergo a net loss of cytoplasmic K(+) to the interstitial space. During intense exercise, plasma K(+) in human arterial blood may reach 8 mm, and interstitial K(+) 10-12 mm. This leads to depolarization, loss of excitability and contractile force. However, little is known about the effects of these physiological increases in extracellular K(+) ([K(+)](o)) on contractile endurance. Soleus muscles from 4-week-old rats were mounted on transducers for isometric contractions in Krebs-Ringer bicarbonate buffer containing 4-10 mm K(+), and endurance assessed by recording the rate of force decline during continuous stimulation at 60 Hz. Increasing [K(+)](o) from 4 to 8 or 10 mm and equilibrating the muscles for 40 or 20 min augmented the rate of force decline 2.4-fold and 7.2-fold, respectively (P < 0.001). The marked loss of endurance elicited by exposure to 8 or 10 mm K(+) was alleviated or significantly reduced by stimulating the Na(+),K(+)-pumps by intracellular Na(+) loading, the beta(2)-agonist salbutamol, adrenaline, calcitonin gene related peptide, insulin or repeated excitation. In conclusion, excitation-induced increase in [K(+)](o) is an important cause of high-frequency fatigue, and the Na(+),K(+)-pumps are essential for the maintenance of contractile force in the physiological range of [K(+)](o). Recordings of contractile force during continuous stimulation at 8-10 mm K(+) may be used to analyse the effects of agents or conditions influencing the excitability of working isolated muscles.

  8. Effects of age and regular exercise on muscle strength and endurance.

    PubMed

    Laforest, S; St-Pierre, D M; Cyr, J; Gayton, D

    1990-01-01

    Twenty male and 20 female non-professional tennis players were classified into two different age groups (n = 10 per group): young active men (30.4 +/- 3.3 years), young active women (27.5 +/- 4.3 years), elderly active men (64.4 +/- 3.7 years), and elderly active women (65.3 +/- 4.5 years). These individuals were matched (n = 10 per group) according to sex, age, height and mass to sedentary individuals of the same socio-economical background: young sedentary men (29.2 +/- 3.4 years), young sedentary women (25.6 +/- 4.4 years), elderly sedentary men (65.2 +/- 3.2 years) and elderly sedentary women (65.6 +/- 4.4 years). An isokinetic dynamometer was used to measure the strength of the knee extensors and flexors (two separate occasions) and the endurance of the extensors. Vastus lateralis electromyogram (EMG) was measured concomitantly. Significant sex, age and exercise effects (P less than 0.001) were observed for peak torque of both muscle groups. The effect of age on extensor strength was more pronounced at high speeds where men were also able to generate larger relative torques than women. No age or sex effects were noted for muscle endurance. However, muscles of active individuals demonstrated a greater resistance to fatigue than those of sedentary individuals. In conclusion, men were found to be stronger than women, age was associated with a decrease in muscle strength, but not of muscle endurance, and tennis players were stronger and had muscles that were more resistant to fatigue than their sedentary pairs in both age groups.(ABSTRACT TRUNCATED AT 250 WORDS)

  9. Effect of alloy composition on high-temperature bending fatigue strength of ferritic stainless steels

    NASA Astrophysics Data System (ADS)

    Ahn, Yong-Sik; Song, Jeon-Young

    2011-12-01

    Exhaust manifolds are subjected to an environment in which heating and cooling cycles occur due to the running pattern of automotive engines. This temperature profile results in the repeated bending stress of exhaust pipes. Therefore, among high-temperature characteristics, the bending fatigue strength is an important factor that affects the lifespan of exhaust manifolds. Here, we report on the effect of the alloy composition, namely the weight fraction of the elements Cr, Mo, Nb, and Ti, on the high-temperature bending fatigue strength of the ferritic stainless steel used in exhaust manifolds. Little difference in the tensile strength and bending fatigue strength of the different composition steels was observed below 600 °C, with the exception of the low-Cr steel. However, steels with high Cr, Mo, or Nb fractions showed considerably larger bending fatigue strength at temperatures of 800 °C. After heating, the precipitates from the specimens were extracted electrolytically and analyzed using scanning electron microscopy energy dispersive spectrometry and transmission electron microscopy. Alloying with Cr and Mo was found to increase the bending fatigue strength due to the substitutional solid solution effect, while alloying with Nb enhanced the strength by forming fine intermetallic compounds, including NbC and Fe2Nb.

  10. Skeletal muscle power and fatigue at the tolerable limit of ramp-incremental exercise in COPD.

    PubMed

    Cannon, Daniel T; Coelho, Ana Claudia; Cao, Robert; Cheng, Andrew; Porszasz, Janos; Casaburi, Richard; Rossiter, Harry B

    2016-12-01

    Muscle fatigue (a reduced power for a given activation) is common following exercise in chronic obstructive pulmonary disease (COPD). Whether muscle fatigue, and reduced maximal voluntary locomotor power, are sufficient to limit whole body exercise in COPD is unknown. We hypothesized in COPD: 1) exercise is terminated with a locomotor muscle power reserve; 2) reduction in maximal locomotor power is related to ventilatory limitation; and 3) muscle fatigue at intolerance is less than age-matched controls. We used a rapid switch from hyperbolic to isokinetic cycling to measure the decline in peak isokinetic power at the limit of incremental exercise ("performance fatigue") in 13 COPD patients (FEV1 49 ± 17%pred) and 12 controls. By establishing the baseline relationship between muscle activity and isokinetic power, we apportioned performance fatigue into the reduction in muscle activation and muscle fatigue. Peak isokinetic power at intolerance was ~130% of peak incremental power in controls (274 ± 73 vs. 212 ± 84 W, P < 0.05), but ~260% in COPD patients (187 ± 141 vs. 72 ± 34 W, P < 0.05), greater than controls (P < 0.05). Muscle fatigue as a fraction of baseline peak isokinetic power was not different in COPD patients vs. controls (0.11 ± 0.20 vs. 0.19 ± 0.11). Baseline to intolerance, the median frequency of maximal isokinetic muscle activity, was unchanged in COPD patients but reduced in controls (+4.3 ± 11.6 vs. -5.5 ± 7.6%, P < 0.05). Performance fatigue as a fraction of peak incremental power was greater in COPD vs. controls and related to resting (FEV1/FVC) and peak exercise (V̇E/maximal voluntary ventilation) pulmonary function (r(2) = 0.47 and 0.55, P < 0.05). COPD patients are more fatigable than controls, but this fatigue is insufficient to constrain locomotor power and define exercise intolerance. Copyright © 2016 the American Physiological Society.

  11. Effect of polymer coatings on fatigue strength of aluminum alloy 2024 box beams

    NASA Technical Reports Server (NTRS)

    Nordmark, G. E.; Kelsey, R. A.

    1972-01-01

    Previous investigators have shown that polymer coatings raise the fatigue strength of metals tested in air to about the same level as that of uncoated specimens tested in vacuum. The results are given of tests to determine if a polymer coating would improve the fatigue strength of built-up aluminum alloy members simulating aircraft construction. Aluminum alloy 2024-T4 riveted box beams were subjected to constant amplitude fatigue tests in air as well as in salt water fog. The coating did not improve the fatigue strength of beams tested in either environment. This is believed to result from the fact that most failures originated at rivet holes, which were isolated from both the coating and the environment.

  12. Tai Chi, arterial compliance, and muscle strength in older adults.

    PubMed

    Lu, Xi; Hui-Chan, Christina W Y; Tsang, William W N

    2013-08-01

    Aerobic exercise can alleviate the declines in arterial compliance common in older adults. However, when combined with strength training, aerobic exercise may not reduce arterial compliance. Tai Chi practice has been found to improve muscle strength and cardiopulmonary function in older subjects, but whether or not it improves arterial compliance is not known. The primary aim of this study was to investigate whether Tai Chi practitioners have better arterial compliance and muscle strength. Twenty-nine older Tai Chi practitioners (73.7 ± 4.5 years) and 36 healthy control subjects (71.4 ± 6.6 years) participated in this cross-sectional study. The participants were independent in their daily living activities. They were screened for apparent cardiovascular disease and underwent arterial compliance testing and isokinetic knee muscle strength testing at 30°/s. Tai Chi practitioners showed significantly better haemodynamic parameters than the controls as indexed by larger and small artery compliance. They also demonstrated greater eccentric muscle strength in both knee extensors and flexors. The findings of better muscle strength without jeopardizing arterial compliance suggests that Tai Chi could be a suitable exercise for older persons to improve both cardiovascular function and muscle strength.

  13. Fatigue-induced changes in synergistic muscle force do not match tendon elongation.

    PubMed

    Mitsukawa, Naotoshi; Sugisaki, Norihide; Miyamoto, Naokazu; Yanai, Toshimasa; Kanehisa, Hiroaki; Fukunaga, Tetsuo; Kawakami, Yasuo

    2010-05-28

    This study aimed to investigate whether fatigue-induced changes in synergistic muscle forces match their tendon elongation. The medial gastrocnemius muscle (MG) was fatigued by repeated electrical stimulation (1 min x 5 times: interval 30 s, intensity: 20-30% of maximal voluntary plantar flexion torque) applied at the muscle belly under a partial occlusion of blood vessels. Before and after the MG fatigue task, ramp isometric contractions were performed voluntarily, during which tendon elongations were determined by ultrasonography, along with recordings of the surface EMG activities of MG, the soleus (SOL) and the lateral gastrocnemius (LG) muscles. The tendon elongation of MG and SOL in post-fatigue ramp was similar, although evoked MG forces dropped nearly to zero. In addition, for a given torque output, the tendon elongation of SOL significantly decreased while that of LG did not, although the activation levels of both muscles had increased. Results suggest that the fatigue-induced changes in force of the triceps surae muscles do not match their tendon elongation. These results imply that the tendons of the triceps surae muscles are mechanically coupled even after selective fatigue of a single muscle.

  14. [Development of Muscle Strength Evaluating System Based on Mobile Platform].

    PubMed

    Xu, Xiulin; Yao, Xiaoming; Xu, Xijiao; Hu, Xiaohui

    2015-08-01

    The development of muscle strength evaluating system based on Android system was developed in this research. The system consists of a lower unit and an intelligent mobile terminal. The pressure sensor of the lower unit was used to collect muscle strength parameters. And the parameters were sent to the Android device through the wireless Bluetooth serial port. Then the Android device would send the parameters to the doctor monitored platform through the Internet. The system realized analyzing the muscle strength parameters and real-time displaying them. After it ran on the Android mobile phones, it showed an effective result which proved that the system combined with mobile platform could make more convenient for the patients to assess their own muscle strength. It also provided reliable data references for doctors to know the patients' rehabilitation condition and to make the next rehabilitation plan.

  15. Neck Muscle Endurance and Fatigue as a Function of Helmet Loading: The Definitive Mathematical Model

    DTIC Science & Technology

    1984-09-01

    time (to fatigue) was recorded, the EMG over the right sternocleidomastoid muscle, over the po-:terior trapezius/splenius muscles, and the systolic and...and * sternocleidomastoid necP muscle). The contraction mode selected, would then be repeated at 3 minute intervals until 3 such contractions were

  16. Flavonoid galangin prevents smooth muscle fatigue of pig urinary bladder.

    PubMed

    Dambros, Miriam; de Jongh, Rik; van Koeveringe, Gommert A; Bast, Aalt; Heijnen, C G M; van Kerrebroeck, Philip E V

    2005-05-01

    There is increasing evidence that the generation of free radicals plays a role in the development of bladder dysfunction. Flavonoids are a group of polyphenolic compounds with broad pharmacological activity. In the present study, the protective effects of the flavonoid galangin on the progressive decrease of bladder smooth muscle contractile responses during repetitive field stimulation (RFS; a model for muscular fatigue) were demonstrated. Pig detrusor strips were mounted for tension recording in organ baths aand were subjected to RFS for 90 min at 32 Hz for 15 s every 5 min. The strips were then washed four times with fresh buffer and allowed a period of recovery for 90 min. The 90 min of RFS caused a progressive decrease in maximal contractile response to electrical field stimulation and to muscarinic agonist-induced contractions (34% and 46% decrease, respectively). Galangin (10(-7) M) prevented the decrease in contractile smooth muscle response of strips to electrical field stimulation during RFS compared with untreated tissues. The antioxidant activity of galangin was assessed by measuring its ability to inhibit the lipid peroxidation induced by iron and ascorbate in rat liver microsomes (IC50 1.7+0.12x10(-6) M). If the data are confirmed in-vivo, exogenously administered galangin may be a new approach in the prevention and/or treatment of bladder dysfunction.

  17. Residual strength of five boron/aluminum laminates with crack-like notches after fatigue loading

    NASA Technical Reports Server (NTRS)

    Simonds, R. A.

    1986-01-01

    Boron/aluminum specimens were made with crack-like slits in the center and with various proportions of 0 and + or - 45 deg plies. They were fatigue loaded and then fractured to determine their residual strengths. The fatigue loads were generally in the range of 60 to 80 percent of the static tensile strength of the specimen as determined from a previous study, and the stress ratio was .05. For virtually all of the specimens the fatigue loading was continued for 100,000 cycles. The specimens were radiographed after the fatigue loading to determine the nature of the fatigue damage. A few specimens were sectioned and examined in a scanning electron microscope after being radiographed in order to verify the interpretation of the radiographs and also to get a better insight into the nature of the fatigue damage. The results indicate that the fatiguing does not significantly affect the strength of the specimens tested. The results of the radiography and of the scanning electron microscopy indicate that the 45 deg plies suffer extensive damage in the form of split and broken fibers and matrix cracking in the vicinity of the ends of the split. By contrast, the only significant damage to the 0 deg plies was a single 0 deg matric crack growing from the ends of the slit and between the 0 deg fibers.

  18. Residual strength of five boron/aluminum laminates with crack-like notches after fatigue loading

    NASA Technical Reports Server (NTRS)

    Simonds, R. A.

    1984-01-01

    Boron/aluminum specimens were made with crack-like slits in the center and with various proportions of 0 and + or - 45 deg plies. They were fatigue loaded and then fractured to determine their residual strengths. The fatigue loads were generally in the range of 60 to 80 percent of the static tensile strength of the specimen as determined from a previous study, and the stress ratio was .05. For virtually all of the specimens the fatigue loading was continued for 100,000 cycles. The specimens were radiographed after the fatigue loading to determine the nature of the fatigue damage. A few specimens were sectioned and examined in a scanning electron microscope after being radiographed in order to verify the interpretation of the radiographs and also to get a better insight into the nature of the fatigue damage. The results indicate that the fatiguing does not significantly affect the strength of the specimens tested. The results of the radiography and of the scanning electron microscopy indicate that the 45 deg plies suffer extensive damage in the form of split and broken fibers and matrix cracking in the vicinity of the ends of the split. By contrast, the only significant damage to the 0 deg plies was a single 0 deg matric crack growing from the ends of the slit and between the 0 deg fibers.

  19. Degradation in the Fatigue Strength of Dentin by Cutting, Etching and Adhesive Bonding

    PubMed Central

    Lee, H.-H.; Majd, H.; Orrego, S.; Majd, B.; Romberg, E.; Mutluay, M.M.; Arola, D.

    2014-01-01

    The processes involved in placing resin composite restorations may degrade the fatigue strength of dentin and increase the likelihood of fractures in restored teeth. Objective The objective of this study was to evaluate the relative changes in strength and fatigue behavior of dentin caused by bur preparation, etching and resin bonding procedures using a 3-step system. Methods Specimens of dentin were prepared from the crowns of unrestored 3rd molars and subjected to either quasi-static or cyclic flexural loading to failure. Four treated groups were prepared including dentin beams subjected to a burr treatment only with a conventional straight-sided bur, or etching treatment only. An additional treated group received both bur and etching treatments, and the last was treated by bur treatment and etching, followed by application of a commercial resin adhesive. The control group consisted of “as sectioned” dentin specimens. Results Under quasi-static loading to failure there was no significant difference between the strength of the control group and treated groups. Dentin beams receiving only etching or bur cutting treatments exhibited fatigue strengths that were significantly lower (p≤0.0001) than the control; there was no significant difference in the fatigue resistance of these two groups. Similarly, the dentin receiving bur and etching treatments exhibited significantly lower (p≤0.0001) fatigue strength than that of the control, regardless of whether an adhesive was applied. Significance The individual steps involved in the placement of bonded resin composite restorations significantly decrease the fatigue strength of dentin, and application of a bonding agent does not increase the fatigue strength of dentin. PMID:24985539

  20. Residual strength of a thermomechanically fatigued TIMETAL 21S/SCS-6 composite

    SciTech Connect

    Schmidt, C.G.; Kanazawa, C.H.; Shockey, D.A.

    1995-10-01

    The factors contributing to the residual strength of a thermomechanically-fatigued SiC fiber-reinforced metal matrix composite were assessed based on fracture surface features. The estimated residual strength was found to be in reasonable agreement with the measured value.

  1. Comparative Associations of Muscle Mass and Muscle Strength with Mortality in Dialysis Patients

    PubMed Central

    Isoyama, Naohito; Qureshi, Abdul Rashid; Avesani, Carla Maria; Lindholm, Bengt; Bàràny, Peter; Heimbürger, Olof; Cederholm, Tommy; Stenvinkel, Peter

    2014-01-01

    Background and objectives Reduced muscle mass and strength are prevalent conditions in dialysis patients. However, muscle strength and muscle mass are not congruent; muscle strength can diminish even though muscle mass is maintained or increased. This study addresses phenotype and mortality associations of these muscle dysfunction entities alone or in combination (i.e., concurrent loss of muscle mass and strength/mobility, here defined as sarcopenia). Design, setting, participants, & measurements This study included 330 incident dialysis patients (203 men, mean age 53±13 years, and mean GFR 7±2 ml/min per 1.73 m2) recruited between 1994 and 2010 and followed prospectively for up to 5 years. Low muscle mass (by dual-energy x-ray absorptiometry appendicular mass index) and low muscle strength (by handgrip) were defined against young reference populations according to the European Working Group on Sarcopenia in Older People. Results Whereas 20% of patients had sarcopenia, low muscle mass and low muscle strength alone were observed in a further 24% and 15% of patients, respectively. Old age, comorbidities, protein-energy wasting, physical inactivity, low albumin, and inflammation associated with low muscle strength, but not with low muscle mass (multivariate ANOVA interactions). During follow-up, 95 patients (29%) died and both conditions associated with mortality as separate entities. When combined, individuals with low muscle mass alone were not at increased risk of mortality (adjusted hazard ratio [HR], 1.23; 95% confidence interval [95% CI], 0.56 to 2.67). Individuals with low muscle strength were at increased risk, irrespective of their muscle stores being appropriate (HR, 1.98; 95% CI, 1.01 to 3.87) or low (HR, 1.93; 95% CI, 1.01 to 3.71). Conclusions Low muscle strength was more strongly associated with aging, protein-energy wasting, physical inactivity, inflammation, and mortality than low muscle mass. Assessment of muscle functionality may provide additional

  2. Fatigue and tensile strength of dental gallium alloys after artificial saliva immersion.

    PubMed

    Meiana, S; Takahashi, H

    1998-12-01

    Fatigue strength using the stair-case method and tensile strength of dental gallium alloys after artificial saliva immersion were measured for evaluating the effects of corrosive environment storage on the mechanical properties of the gallium alloys. The fatigue and the tensile strengths of both gallium alloys stored in artificial saliva were significantly decreased after 12-month storage, while those stored in air increased with storage period. The fracture surfaces of the specimens in artificial saliva showed not only metallic luster but also dark areas. In the dark area, the matrix might have dissolved during immersion. These results suggested that the concern over corrosion resistance of gallium alloys still remained.

  3. Respiratory muscle dysfunction in animal models of hypoxic disease: antioxidant therapy goes from strength to strength.

    PubMed

    O'Halloran, Ken D; Lewis, Philip

    2017-01-01

    The striated muscles of breathing play a critical role in respiratory homeostasis governing blood oxygenation and pH regulation. Upper airway dilator and thoracic pump muscles retain a remarkable capacity for plasticity throughout life, both in health and disease states. Hypoxia, whatever the cause, is a potent driver of respiratory muscle remodeling with evidence of adaptive and maladaptive outcomes for system performance. The pattern, duration, and intensity of hypoxia are key determinants of respiratory muscle structural-, metabolic-, and functional responses and adaptation. Age and sex also influence respiratory muscle tolerance of hypoxia. Redox stress emerges as the principal protagonist driving respiratory muscle malady in rodent models of hypoxic disease. There is a growing body of evidence demonstrating that antioxidant intervention alleviates hypoxia-induced respiratory muscle dysfunction, and that N-acetyl cysteine, approved for use in humans, is highly effective in preventing hypoxia-induced respiratory muscle weakness and fatigue. We posit that oxygen homeostasis is a key driver of respiratory muscle form and function. Hypoxic stress is likely a major contributor to respiratory muscle malaise in diseases of the lungs and respiratory control network. Animal studies provide an evidence base in strong support of the need to explore adjunctive antioxidant therapies for muscle dysfunction in human respiratory disease.

  4. A study of stiffness, residual strength and fatigue life relationships for composite laminates

    NASA Technical Reports Server (NTRS)

    Ryder, J. T.; Crossman, F. W.

    1983-01-01

    Qualitative and quantitative exploration of the relationship between stiffness, strength, fatigue life, residual strength, and damage of unnotched, graphite/epoxy laminates subjected to tension loading. Clarification of the mechanics of the tension loading is intended to explain previous contradictory observations and hypotheses; to develop a simple procedure to anticipate strength, fatigue life, and stiffness changes; and to provide reasons for the study of more complex cases of compression, notches, and spectrum fatigue loading. Mathematical models are developed based upon analysis of the damage states. Mathematical models were based on laminate analysis, free body type modeling or a strain energy release rate. Enough understanding of the tension loaded case is developed to allow development of a proposed, simple procedure for calculating strain to failure, stiffness, strength, data scatter, and shape of the stress-life curve for unnotched laminates subjected to tension load.

  5. Transverse strength and fatigue of denture acrylic-glass fiber composite.

    PubMed

    Vallittu, P K; Lassila, V P; Lappalainen, R

    1994-03-01

    The aims of this experiment were: 1) to test the effect of a high concentration of continuous glass fibers on the transverse strength of test specimens made of heat-cured acrylic resin; and 2) to determine the fatigue weakening of both unreinforced and continuous glass fiber-reinforced specimens of heat-cured acrylic resin shaped into upper complete dentures. A three-point loading test was used to determine the transverse strength of test specimens (n = 30 per group). The fatigue test was the constant deflection test (n = 10 per group). The results revealed that, compared to unreinforced specimens, continuous glass fibers at a concentration of 58 wt% enhanced the transverse strength of the test specimens up to 146% (p < 0.001) and increased the fatigue resistance (p < 0.001) during 5 x 10(5) loading cycles. This study suggests that by incorporating glass fibers into PMMA denture bases, the strength of the denture can be increased.

  6. Interactions of age and leg muscle fatigue on unobstructed walking and obstacle crossing.

    PubMed

    Barbieri, Fabio Augusto; dos Santos, Paulo Cezar Rocha; Simieli, Lucas; Orcioli-Silva, Diego; van Dieën, Jaap H; Gobbi, Lilian Teresa Bucken

    2014-03-01

    Older adults commonly report muscle fatigue, which may be associated with reduced walking ability. Elderly may have insufficient awareness of the balance threat caused by muscle fatigue. The aim of this study was to analyze the interaction effects of aging and leg muscle fatigue on gait parameters in walking and obstacle crossing. One hundred and twenty men, who were divided in six groups according to their age (20-29 years, 30-39 years, 40-49 years, 50-59 years, 60-69 years, above 70 years), participated in this study. Participants performed three trials of unobstructed level ground walking and obstacle crossing during walking before and after quadriceps muscle fatigue. To induce fatigue, participants performed a repeated sit-to-stand task from a chair with arms across the chest to a pre-determined cadence (30 cycles/min) using a metronome. Spatial-temporal gait parameters (stride length, duration, and speed, step width, and trailing and leading heel-clearance) were analyzed, and compared by two-way ANOVA (group and fatigue). The results confirmed our hypothesis, showing age-related effects of leg muscles fatigue in both gait conditions. From 40 years old, participants modulated spatial-temporal and vertical impulses in both tasks more in response to fatigue than younger participants, apparently to improve balance and safety. Leg muscle fatigue caused age-dependent changes in both unobstructed level ground walking and obstacle crossing during walking, which appeared to reflect an attempt to maintain balance and safety, probably to counteract adverse fatigue effects.

  7. Immediate effect of manual therapy on respiratory functions and inspiratory muscle strength in patients with COPD

    PubMed Central

    Yilmaz Yelvar, Gul Deniz; Çirak, Yasemin; Demir, Yasemin Parlak; Dalkilinç, Murat; Bozkurt, Bülent

    2016-01-01

    Objective The objective of this study was to investigate the immediate effect of manual therapy (MT) on respiratory functions and inspiratory muscle strength in patients with COPD. Participants and methods Thirty patients with severe COPD (eight females and 22 males; mean age 62.4±6.8 years) referred to pulmonary physiotherapy were included in this study. The patients participated in a single session of MT to measure the short-term effects. The lung function was measured using a portable spirometer. An electronic pressure transducer was used to measure respiratory muscle strength. Heart rate, breathing frequency, and oxygen saturation were measured with a pulse oximeter. For fatigue and dyspnea perception, the modified Borg rating of perceived exertion scale was used. All measurements were taken before and immediately after the first MT session. The ease-of-breathing visual analog scale was used for rating patients’ symptoms subjectively during the MT session. Results There was a significant improvement in the forced expiratory volume in the first second, forced vital capacity, and vital capacity values (P<0.05). The maximal inspiratory pressure and maximal expiratory pressure values increased significantly after MT, compared to the pre-MT session (P<0.05). There was a significant decrease in heart rate, respiratory rate (P<0.05), and dyspnea and fatigue perception (P<0.05). Conclusion A single MT session immediately improved pulmonary function, inspiratory muscle strength, and oxygen saturation and reduced dyspnea, fatigue, and heart and respiratory rates in patients with severe COPD. MT should be added to pulmonary rehabilitation treatment as a new alternative that is fast acting and motivating in patients with COPD. PMID:27382271

  8. Effectiveness of a tailored neck training program on neck strength, movement, and fatigue in under-19 male rugby players: a randomized controlled pilot study.

    PubMed

    Barrett, Matthew D; McLoughlin, Terence F; Gallagher, Kieran R; Gatherer, Don; Parratt, Michael Tr; Perera, Jonathan R; Briggs, Tim Wr

    2015-01-01

    To investigate the effect of a tailored neck muscle conditioning program on neck muscle strength, neck muscle fatigue, and range of neck movement in 16-18-year-old male rugby players. Thirty-four male rugby players were divided into forward and back playing positions and randomized within these groups. Seventeen players were randomly assigned to each group. The test group was given a tailored 6-week exercise regime based on their baseline measurements to be performed three times a week in addition to their normal training and playing. The control group trained and played as normal. The outcome measures used were cervical spine range of movement, neck strength, and neck muscle fatigability. There were no clinically relevant statistically significant differences between the two groups. Trends identified between the two groups suggest that a tailored neck exercise program increases neck strength, particularly neck extension, and increases resistance to fatigue, as well as influencing right- and left-sided neck muscle balance. A reduction in range of movement was also demonstrated in the test group. There was a great deal of variability in range of movement and strength within this age group. No previously undiagnosed neck conditions were detected, and there were no adverse events reported. This study has shown that neck strength, range of movement, and susceptibility of the neck muscles to fatigue can be influenced using a focused neck training regime. It forms an important basis for a larger, multicenter study to ensure the neck is given due attention in rugby training and receives the same focus of conditioning as other parts of the body.

  9. Effectiveness of a tailored neck training program on neck strength, movement, and fatigue in under-19 male rugby players: a randomized controlled pilot study

    PubMed Central

    Barrett, Matthew D; McLoughlin, Terence F; Gallagher, Kieran R; Gatherer, Don; Parratt, Michael TR; Perera, Jonathan R; Briggs, Tim WR

    2015-01-01

    Purpose To investigate the effect of a tailored neck muscle conditioning program on neck muscle strength, neck muscle fatigue, and range of neck movement in 16–18-year-old male rugby players. Materials and methods Thirty-four male rugby players were divided into forward and back playing positions and randomized within these groups. Seventeen players were randomly assigned to each group. The test group was given a tailored 6-week exercise regime based on their baseline measurements to be performed three times a week in addition to their normal training and playing. The control group trained and played as normal. The outcome measures used were cervical spine range of movement, neck strength, and neck muscle fatigability. Results There were no clinically relevant statistically significant differences between the two groups. Trends identified between the two groups suggest that a tailored neck exercise program increases neck strength, particularly neck extension, and increases resistance to fatigue, as well as influencing right- and left-sided neck muscle balance. A reduction in range of movement was also demonstrated in the test group. There was a great deal of variability in range of movement and strength within this age group. No previously undiagnosed neck conditions were detected, and there were no adverse events reported. Conclusion This study has shown that neck strength, range of movement, and susceptibility of the neck muscles to fatigue can be influenced using a focused neck training regime. It forms an important basis for a larger, multicenter study to ensure the neck is given due attention in rugby training and receives the same focus of conditioning as other parts of the body. PMID:25999771

  10. Muscle Power Predicts Adolescent Bone Strength: Iowa Bone Development Study.

    PubMed

    Janz, Kathleen F; Letuchy, Elena M; Burns, Trudy L; Francis, Shelby L; Levy, Steven M

    2015-10-01

    To assess association between lower body muscle power and bone strength as well as the mediating effect of muscle cross-sectional area (MCSA) on that association. Participants (141 males and 162 females) were approximately 17 yr. Muscle power was predicted using vertical jump and the Sayers equation. Using peripheral quantitative computed tomography (pQCT), bone strength indices were obtained at two locations of the tibia, corresponding to primary stressors acting upon each site: bone strength index for compression (BSI) at the distal 4% site; density-weighted polar section modulus strength-strain index (SSIp) and cortical bone area (CoA) at the 66% midshaft site for torsion. Muscle cross-sectional area was measured at the 66% site. Pearson bivariate and partial correlation coefficients were estimated to quantify the strength of the associations among variables. Direct and indirect mediation model effects were estimated, and 95% bootstrap confidence intervals were constructed to test the causal hypothesis. Height and maturity were examined as covariates. Pearson correlation coefficients among muscle power, MCSA, and bone strength were statistically significant (P < 0.01) and ranged from r = 0.54 to r = 0.78. After adjustment for covariates, associations were reduced (r = 0.37 to 0.69) (P < 0.01). Mediation models for males for BSI, SSIp, and CoA accounted for 38%, 66%, and 54% of the variance in bone strength, respectively. Models for females for BSI, SSIp, and CoA accounted for 46%, 77%, and 66% of the variance, respectively. We found strong and consistent associations as well as direct and indirect pathways, among muscle power, MCSA, and tibia strength. These results support the use of muscle power as a component of health-related fitness in bone health interventions for older adolescents.

  11. Muscle Power Predicts Adolescent Bone Strength: Iowa Bone Development Study

    PubMed Central

    Janz, Kathleen F.; Letuchy, Elena M.; Burns, Trudy L.; Francis, Shelby L.; Levy, Steven M.

    2015-01-01

    Purpose To assess association between lower body muscle power and bone strength, as well as the mediating effect of muscle cross-sectional area (MCSA) on that association. Methods Participants (N=141 males; 162 females) were approximately 17 years. Muscle power was predicted using vertical jump and the Sayers equation. Using peripheral quantitative computed tomography (pQCT), bone strength indices were obtained at two locations of the tibia, corresponding to primary stressors acting upon each site: bone strength index for compression (BSI) at the distal 4% site; density-weighted polar section modulus strength-strain index [SSIp] and cortical bone area (CoA) at the 66% mid-shaft site for torsion. Muscle cross-sectional area (MCSA) was measured at the 66% site. Pearson bivariate and partial correlation coefficients were estimated to quantify the strength of the associations among variables. Direct and indirect mediation model effects were estimated and 95% bootstrap confidence intervals were constructed to test the causal hypothesis. Height and maturity were examined as covariates. Results Pearson correlation coefficients among muscle power, MCSA, and bone strength were statistically significant (p<0.01) and ranged from r=0.54 to 0.78. After adjustment for covariates, associations were reduced (r=0.37 to 0.69) (p<0.01). Mediation models for males for BSI, SSIp, and CoA accounted for 38%, 66%, and 54% of the variance in bone strength, respectively. Models for females for BSI, SSIp, and CoA accounted for 46%, 77%, and 66% of the variance, respectively. Conclusions We found strong and consistent associations, as well as direct and indirect pathways, among muscle power, MCSA, and tibia strength. These results support the use of muscle power as a component of health-related fitness in bone health interventions for older adolescents. PMID:25751769

  12. Classifying lower extremity muscle fatigue during walking using machine learning and inertial sensors.

    PubMed

    Zhang, Jian; Lockhart, Thurmon E; Soangra, Rahul

    2014-03-01

    Fatigue in lower extremity musculature is associated with decline in postural stability, motor performance and alters normal walking patterns in human subjects. Automated recognition of lower extremity muscle fatigue condition may be advantageous in early detection of fall and injury risks. Supervised machine learning methods such as support vector machines (SVMs) have been previously used for classifying healthy and pathological gait patterns and also for separating old and young gait patterns. In this study we explore the classification potential of SVM in recognition of gait patterns utilizing an inertial measurement unit associated with lower extremity muscular fatigue. Both kinematic and kinetic gait patterns of 17 participants (29 ± 11 years) were recorded and analyzed in normal and fatigued state of walking. Lower extremities were fatigued by performance of a squatting exercise until the participants reached 60% of their baseline maximal voluntary exertion level. Feature selection methods were used to classify fatigue and no-fatigue conditions based on temporal and frequency information of the signals. Additionally, influences of three different kernel schemes (i.e., linear, polynomial, and radial basis function) were investigated for SVM classification. The results indicated that lower extremity muscle fatigue condition influenced gait and loading responses. In terms of the SVM classification results, an accuracy of 96% was reached in distinguishing the two gait patterns (fatigue and no-fatigue) within the same subject using the kinematic, time and frequency domain features. It is also found that linear kernel and RBF kernel were equally good to identify intra-individual fatigue characteristics. These results suggest that intra-subject fatigue classification using gait patterns from an inertial sensor holds considerable potential in identifying "at-risk" gait due to muscle fatigue.

  13. Knee joint neuromuscular activation performance during muscle damage and superimposed fatigue.

    PubMed

    Minshull, Claire; Eston, Roger; Rees, David; Gleeson, Nigel

    2012-01-01

    This study examined the concurrent effects of exercise-induced muscle damage and superimposed acute fatigue on the neuromuscular activation performance of the knee flexors of nine males (age: 26.7 ± 6.1 years; height 1.81 ± 0.05 m; body mass 81.2 ± 11.7 kg [mean±s]). Measures were obtained during three experimental conditions: (i) 'fatigue-muscle damage', involving acute fatiguing exercise performed on each assessment occasion plus a single episode of eccentric exercise performed on the first occasion and after the fatigue trial; (ii) 'fatigue', involving the fatiguing exercise only; and (iii) 'control' consisting of no exercise. Assessments were performed prior to (pre) and at 1 h, 24 h, 48 h, 72 h, and 168 h relative to the muscle damaging eccentric exercise. Repeated-measures analyses of variance (ANOVAs) showed that muscle damage elicited reductions of up to 38%, 24% and 65% in volitional peak force, electromechanical delay and rate of force development compared to baseline and controls, respectively (F ([10, 80]) = 2.3 to 4.6; P < 0.05) with further impairments (6.2% to 30.7%) following acute fatigue (F ([2, 16]) = 4.3 to 9.1; P < 0.05). By contrast, magnetically-evoked electromechanical delay was not influenced by muscle damage and was improved during the superimposed acute fatigue (∼14%; F ([2, 16]) = 3.9; P < 0.05). The safeguarding of evoked muscle activation capability despite compromised volitional performance might reveal aspects of capabilities for emergency and protective responses during episodes of fatigue and antecedent muscle damaging exercise.

  14. Locomotor Muscle Fatigue Does Not Alter Oxygen Uptake Kinetics during High-Intensity Exercise

    PubMed Central

    Hopker, James G.; Caporaso, Giuseppe; Azzalin, Andrea; Carpenter, Roger; Marcora, Samuele M.

    2016-01-01

    The V˙O2 slow component (V˙O2sc) that develops during high-intensity aerobic exercise is thought to be strongly associated with locomotor muscle fatigue. We sought to experimentally test this hypothesis by pre-fatiguing the locomotor muscles used during subsequent high-intensity cycling exercise. Over two separate visits, eight healthy male participants were asked to either perform a non-metabolically stressful 100 intermittent drop-jumps protocol (pre-fatigue condition) or rest for 33 min (control condition) according to a random and counterbalanced order. Locomotor muscle fatigue was quantified with 6-s maximal sprints at a fixed pedaling cadence of 90 rev·min−1. Oxygen kinetics and other responses (heart rate, capillary blood lactate concentration and rating of perceived exertion, RPE) were measured during two subsequent bouts of 6 min cycling exercise at 50% of the delta between the lactate threshold and V˙O2max determined during a preliminary incremental exercise test. All tests were performed on the same cycle ergometer. Despite significant locomotor muscle fatigue (P = 0.03), the V˙O2sc was not significantly different between the pre-fatigue (464 ± 301 mL·min−1) and the control (556 ± 223 mL·min−1) condition (P = 0.50). Blood lactate response was not significantly different between conditions (P = 0.48) but RPE was significantly higher following the pre-fatiguing exercise protocol compared with the control condition (P < 0.01) suggesting higher muscle recruitment. These results demonstrate experimentally that locomotor muscle fatigue does not significantly alter the V˙O2 kinetic response to high intensity aerobic exercise, and challenge the hypothesis that the V˙O2sc is strongly associated with locomotor muscle fatigue. PMID:27790156

  15. Examination of Strength Training and Detraining Effects in Expiratory Muscles

    ERIC Educational Resources Information Center

    Baker, Susan; Davenport, Paul; Sapienza, Christine

    2005-01-01

    Purpose: The purpose of this study was to determine strength gains following expiratory muscle strength training (EMST) and to determine detraining effects when the training stimulus is removed. Method: Thirty-two healthy participants were enrolled in an EMST program. Sixteen participants trained for 4 weeks (Group 1) and 16 participants trained…

  16. Examination of Strength Training and Detraining Effects in Expiratory Muscles

    ERIC Educational Resources Information Center

    Baker, Susan; Davenport, Paul; Sapienza, Christine

    2005-01-01

    Purpose: The purpose of this study was to determine strength gains following expiratory muscle strength training (EMST) and to determine detraining effects when the training stimulus is removed. Method: Thirty-two healthy participants were enrolled in an EMST program. Sixteen participants trained for 4 weeks (Group 1) and 16 participants trained…

  17. Effect of diaphragmatic fatigue on control of the respiratory muscles during CO sub 2 rebreathing

    SciTech Connect

    Yan, S.; Lichros, I.; Macklem, P.T. Montreal Chest Hospital, Quebec )

    1991-03-11

    The authors measured respiratory muscle recruitment and ventilation ({dot V}{sub E}) during CO{sub 2} rebreathing before and after diaphragmatic fatigue in normal subjects. Muscle activity was assessed by measuring pleural, abdominal, and transdiaphragmatic pressures (Ppl, Pab, and Pdi, resp). The results showed that (1) there was a progressive increase in Pdi with increasing end-tidal PCO{sub 2} (P{sub ET}CO{sub 2}); the rate of increase was usually greater before than after fatigue, however, in some it was less because of longer operating length and/or passive stretching of the diaphragm due to strong rib cage muscle (RCM) activity induced by fatigue; (2) Pdi increased mainly due to greater fall in Ppl; {Delta}Pab increased little during CO{sub 2} rebreathing or even decreased with P{sub ET}CO{sub 2} over 50-55 mmHg; this pattern was exaggerated by fatigue; (3) at the end of each trial, the ratio {minus}{Delta}Ppl/{Delta}Pab increased by {approximately}140% before and {approximately}850% after fatigue; (4) CO{sub 2} induced expiratory abdominal muscle activity; and (5) as a group, {dot V}{sub E} and its pattern did not change appreciably with fatigue. The authors conclude that RCM are recruited proportionately more than the diaphragm by CO{sub 2} and that diaphragmatic fatigue shifts the central drive from the fatigued diaphragm to TCM to preserve ventilation.

  18. Electromyographic analysis of fatigue in temporalis and masseter muscles during continuous chewing.

    PubMed

    Buzinelli, R V; Berzin, F

    2001-12-01

    The aim of this study was to evaluate the electromyographic changes in the anterior temporalis and masseter muscles after fatigue induced by continuous chewing. Surface electrodes were placed bilaterally over the anterior temporalis and masseter muscles of 31 subjects with normal dentition. Recordings were taken every minute from the beginning of chewing to the exact moment the volunteer reported subjective sensation of fatigue in the jaw muscles. The length of endurance period (fatigue threshold) was measured to each subject, as well as the average amplitude and duration of activation phase and duration of relaxation phase through electromyographic recording of each muscle. The average endurance period was about 500 s. No significant change occurred on the average amplitude of activation phase meanwhile the duration of both the activation and relaxation phase diminished after fatigue.

  19. Porous Ti6Al4V alloys with enhanced normalized fatigue strength for biomedical applications.

    PubMed

    Li, Fuping; Li, Jinshan; Kou, Hongchao; Zhou, Lian

    2016-03-01

    In this paper, porous Ti6Al4V alloys for biomedical applications were fabricated by diffusion bonding of alloy meshes. The compression-compression fatigue behavior was studied. It results that porous Ti6Al4V alloys show enhanced normalized fatigue strength which is in the range of 0.5-0.55 at 10(6)cycles. The porosity has some effect on the absolute S-N curves but minor effect on the normalized S-N curves. The relationship between strain per cycle and number of cycles shows three distinct stages and the value of strain per cycle is constant in stage II. The reasons for the higher normalized fatigue strength of porous Ti6Al4V alloys are discussed based on the fatigue crack initiation and propagation.

  20. The effect of Nordic hamstring strength training on muscle architecture, stiffness, and strength.

    PubMed

    Seymore, Kayla D; Domire, Zachary J; DeVita, Paul; Rider, Patrick M; Kulas, Anthony S

    2017-05-01

    Hamstring strain injury is a frequent and serious injury in competitive and recreational sports. While Nordic hamstring (NH) eccentric strength training is an effective hamstring injury-prevention method, the protective mechanism of this exercise is not understood. Strength training increases muscle strength, but also alters muscle architecture and stiffness; all three factors may be associated with reducing muscle injuries. The purpose of this study was to examine the effects of NH eccentric strength training on hamstring muscle architecture, stiffness, and strength. Twenty healthy participants were randomly assigned to an eccentric training group or control group. Control participants performed static stretching, while experimental participants performed static stretching and NH training for 6 weeks. Pre- and post-intervention measurements included: hamstring muscle architecture and stiffness using ultrasound imaging and elastography, and maximal hamstring strength measured on a dynamometer. The experimental group, but not the control group, increased volume (131.5 vs. 145.2 cm(3), p < 0.001) and physiological cross-sectional area (16.1 vs. 18.1 cm(2), p = 0.032). There were no significant changes to muscle fascicle length, stiffness, or eccentric hamstring strength. The NH intervention was an effective training method for muscle hypertrophy, but, contrary to common literature findings for other modes of eccentric training, did not increase fascicle length. The data suggest that the mechanism behind NH eccentric strength training mitigating hamstring injury risk could be increasing volume rather than increasing muscle length. Future research is, therefore, warranted to determine if muscle hypertrophy induced by NH training lowers future hamstring strain injury risk.

  1. Some remarks on static, creep and fatigue flexural strength of satin woven CFRP laminates

    SciTech Connect

    Miyano, Y.; McMurry, M.K.; Muki, R.

    1995-12-31

    This paper deals with the time-temperature dependent flexural strength of a satin-woven CFRP laminate having a matrix resin with a high glass transition temperature of T{sub g} = 236/C under static, creep and fatigue loading by 3-point bending tests. Static tests were conducted at various points in a wide range of deflection rates and temperatures. The creep and fatigue tests were carried out at various constant temperatures; the fatigue test was conducted at two frequencies. The results of the experimental study are as follows. The flexural strength of the CFRP laminates for all three loading types is time-temperature dependent even near room temperature well below T{sub g}. The time and temperature superposition principle for the matrix resin also holds for the flexural strength of the CFRP laminates. The fracture modes are almost the same for the three loading types under all conditions tested. Finally, we propose a method for predicting the flexural fatigue strength for a given number of cycles to failure at an arbitrary temperature, frequency and stress ratio based on the current experimental findings and considering the relationships among the static, creep and fatigue flexural strengths.

  2. The effect of upper extremity fatigue on grip strength and passing accuracy in junior basketball players.

    PubMed

    Ahmed, Taghread

    2013-01-01

    Fatigue is an unavoidable part of a basketball game, which may affect an athlete's performance. The aim of this study was to investigate the effect of upper extremity fatigue on grip strength and passing accuracy in basketball, and ascertain if the effects of different fatigue protocols on grip strength and passing accuracy are the same. Twenty-four juniors under 18 years old (age: 16.75 ± 0.62 years; body height: 184.5 ± 3.31 cm; body mass: 77.25 ± 3.22 kg) volunteered to participate in the study, and were divided into two groups. After a warm-up, both groups performed the basketball passing test and grip strength was recorded for each group under three different testing conditions: rest, 70% and 90% exercise intensity. The protocol used for the first group was the chest press, and for the second group the wrist curls. Results show that after the upper extremity fatigue protocol all parameters of the study (grip strength and passing accuracy) showed a significant decrease, and there was no significant difference between both groups regarding grip strength and passing accuracy. The study suggested that in order to avoid upper extremity fatigue, basketball trainers and coaches need to include upper extremity conditioning exercises into their training sessions.

  3. Effects of EVA gloves on grip strength and fatigue under low temperature and low pressure.

    PubMed

    Tian, Yinsheng; Ding, Li; Liu, Heqing; Li, Yan; Li, Deyu; Wang, Li

    2016-03-01

    To study the effects of wearing extravehicular activity (EVA) gloves on grip strength and fatigue in low temperature, low pressure and mixing of two factors (low temperature and low pressure). The maximum grip strength and fatigue tests were performed with 10 healthy male subjects wearing gloves in a variety of simulated environments. The data was analysed using the normalization method. The results showed that wearing gloves significantly affected the maximum grip strength and fatigue. Pressure (29.6, 39.2 kPa) had more influence on the maximum grip compared with control group while low temperatures (-50, -90, -110 °C) had no influence on grip but affected fatigue dramatically. The results also showed that the maximum grip strength and fatigue were influenced significantly in a compound environment. Space environment remarkably reduced strength and endurance of the astronauts. However, the effects brought by the compound environment cannot be understood as the superimposition of low temperature and pressure effects. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

  4. Muscle Strength And Golf Performance: A Critical Review

    PubMed Central

    Torres-Ronda, Lorena; Sánchez-Medina, Luis; González-Badillo, Juan J.

    2011-01-01

    Golf has become an increasingly popular sport and a growing body of research trying to identify its main physical requirements is being published. The aim of this review was twofold: first, to examine the existing scientific literature regarding strength training and golf in healthy, non-injured, subjects; and second, to reach conclusions that could provide information on how to design more effective strength training programs to improve golf performance as well as directions for future research. Studies which analyzed the relationship between muscle strength, swing performance variables (club head speed, driving distance, ball speed) and skill (handicap, score) were reviewed. Changes in swing performance following different strength training programs were also investigated. Finally, a critical analysis about the methodologies used was carried out. The results of the reviewed studies seem to indicate that: 1) a positive relationship exists between handicap and swing performance (even though few studies have investigated this issue); 2) there is a positive correlation between skill (handicap and/or score) and muscle strength; and 3) there is a relationship between driving distance, swing speed, ball speed and muscle strength. Results suggest that training leg-hip and trunk power as well as grip strength is especially relevant for golf performance improvement. Studies that analyzed variations in swing performance following resistance-only training programs are scarce, thus it is difficult to prove whether the observed improvements are attributable to changes in strength levels. Many of the studies reviewed presented some methodological errors in their design and not all strength assessment protocols seemed appropriate. Further studies should determine muscle strength needs in relation to final swing performance, using well designed experiments and strict isoinertial assessment protocols which adequately relate to specific golf motion, age and skill level. More

  5. Determine the effect of neck muscle fatigue on dynamic visual acuity in healthy young adults

    PubMed Central

    Al Saif, Amer A.; Al Senany, Samira

    2015-01-01

    [Purpose] The aim of this study was to determine whether neck muscle fatigue affects dynamic visual acuity in healthy young participants. [Subjects and Methods] This study was a double-blinded, prospective, randomized, controlled trial. Thirty healthy young subjects (ages 21 to 30 years) participated in the study. Participants were randomly divided into an experimental group (n=15) and a control group (n=15). The experimental group performed an exercise designed to induce neck muscle fatigue and the control group preformed non-fatiguing sham exercises. [Results] There were significant differences in mean dynamic visual acuity between the two groups (0.26±0.11 LogMar versus 0.003±0.02 LogMar). Subjects in the experimental group showed a significant decline in their dynamic visual acuity compared with the control group. Dynamic visual acuity strongly correlated with neck muscle fatigue (r = 0.79). No significant differences in joint position error were observed between the two groups and no significant correlations between joint position error and neck muscle fatigue were observed (r = 0.23). [Conclusion] The results of this study suggest that neck muscle fatigue negatively impacts dynamic visual acuity. Although not statistically significant, cervical spine proprioception as measured by the joint position error in the experimental group was diminished after fatigue. PMID:25642087

  6. Determine the effect of neck muscle fatigue on dynamic visual acuity in healthy young adults.

    PubMed

    Al Saif, Amer A; Al Senany, Samira

    2015-01-01

    [Purpose] The aim of this study was to determine whether neck muscle fatigue affects dynamic visual acuity in healthy young participants. [Subjects and Methods] This study was a double-blinded, prospective, randomized, controlled trial. Thirty healthy young subjects (ages 21 to 30 years) participated in the study. Participants were randomly divided into an experimental group (n=15) and a control group (n=15). The experimental group performed an exercise designed to induce neck muscle fatigue and the control group preformed non-fatiguing sham exercises. [Results] There were significant differences in mean dynamic visual acuity between the two groups (0.26±0.11 LogMar versus 0.003±0.02 LogMar). Subjects in the experimental group showed a significant decline in their dynamic visual acuity compared with the control group. Dynamic visual acuity strongly correlated with neck muscle fatigue (r = 0.79). No significant differences in joint position error were observed between the two groups and no significant correlations between joint position error and neck muscle fatigue were observed (r = 0.23). [Conclusion] The results of this study suggest that neck muscle fatigue negatively impacts dynamic visual acuity. Although not statistically significant, cervical spine proprioception as measured by the joint position error in the experimental group was diminished after fatigue.

  7. A Review of Non-Invasive Techniques to Detect and Predict Localised Muscle Fatigue

    PubMed Central

    Al-Mulla, Mohamed R.; Sepulveda, Francisco; Colley, Martin

    2011-01-01

    Muscle fatigue is an established area of research and various types of muscle fatigue have been investigated in order to fully understand the condition. This paper gives an overview of the various non-invasive techniques available for use in automated fatigue detection, such as mechanomyography, electromyography, near-infrared spectroscopy and ultrasound for both isometric and non-isometric contractions. Various signal analysis methods are compared by illustrating their applicability in real-time settings. This paper will be of interest to researchers who wish to select the most appropriate methodology for research on muscle fatigue detection or prediction, or for the development of devices that can be used in, e.g., sports scenarios to improve performance or prevent injury. To date, research on localised muscle fatigue focuses mainly on the clinical side. There is very little research carried out on the implementation of detecting/predicting fatigue using an autonomous system, although recent research on automating the process of localised muscle fatigue detection/prediction shows promising results. PMID:22163810

  8. Effect of inspiratory muscle fatigue on exercise performance taking into account the fatigue-induced excess respiratory drive.

    PubMed

    Wüthrich, Thomas U; Notter, Dominic A; Spengler, Christina M

    2013-12-01

    Inspiratory muscle fatigue (IMF) is suggested to compromise exercise performance, possibly via a respiratory muscle metaboreflex that impairs blood flow to working muscles, thereby accelerating the development of fatigue in these muscles. Cycling with IMF has also been associated with an excess ventilatory response, which could per se impair performance. Therefore, the present study investigated whether prior-induced IMF would affect subsequent cycling performance via increased quadriceps muscle fatigue alone and whether fatigue-induced excess ventilation would contribute to this impairment. Fourteen healthy male subjects (peak oxygen uptake, 57.0 ± 5.5 ml min(-1) kg(-1)) cycled to exhaustion at 85% of their maximal work output with prior-induced IMF (PF-EX) and without prior-induced IMF (C-EX). Subjects then cycled twice for the duration of PF-EX but without prior IMF, once with spontaneous breathing (C-ISO) and once with breathing coached to match PF-EX ventilation (MATCH-ISO). Inspiratory muscle (P(tw)) and quadriceps muscle contractility (Q(tw)) was assessed via magnetic nerve stimulation before and after exercise. The time to exhaustion in the PF-EX conditions was significantly reduced by 14% compared with C-EX. The reduction in P(tw) and Q(tw) was greater after PF-EX (P(tw), 17.3 ± 9.7%; Q(tw), 32.0 ± 10.8%) than after MATCH-ISO (P(tw), 10.8 ± 10.3%; Q(tw), 23.3 ± 15.2%; P < 0.05), which may explain the increased perception of exertion and earlier task failure with prior-induced IMF. The augmented ventilatory drive had no effect on reductions in P(tw) and Q(tw) after MATCH-ISO compared with C-ISO. Thus, prior-induced IMF reduces exercise performance, probably as a result of the increased quadriceps muscle fatigue and thus greater perception of exertion independent of the excess respiratory drive when cycling with fatigued inspiratory muscles.

  9. Fatigue is more damaging than creep in ligament revealed by modulus reduction and residual strength.

    PubMed

    Thornton, Gail M; Schwab, Timothy D; Oxland, Thomas R

    2007-10-01

    Following injury of a complementary joint restraint, ligaments can be subjected to higher than normal stresses. Normal ligaments are exposed to static (creep) and cyclic (fatigue) loading from which damage can accumulate at these higher than normal stresses. This study tracked damage accumulation during creep and fatigue loading of normal rabbit medial collateral ligaments (MCLs) over a range of stresses, using modulus reduction as a marker of damage. Creep tests were interrupted occasionally with unloading/reloading cycles to measure modulus. Test stresses were normalized to ultimate tensile strength (UTS): 60%, 30%, and 15% UTS. Not all creep and fatigues tests progressed until rupture but were stopped and followed by an assessment of the residual strength of that partially damaged ligament using a monotonic failure test. Fatigue loading caused earlier modulus reduction than creep. Modulus reduction occurred at lower increases in strain (strain relative to initial strain) for fatigue than creep. In other words, at the same time or increase in strain, fatigue is more damaging than creep because the modulus ratio reduction is greater. These findings suggest that creep and fatigue have different strain and damage mechanisms. Ligaments exposed to creep or fatigue loading which produced a modulus reduction had decreased residual strength and increased toe-region strain in a subsequent monotonic failure test. This finding confirmed that modulus reduction during creep and fatigue is a suitable marker of partial damage in ligament. Cyclic loading caused damage earlier than static loading, likely an important consideration when ligaments are loaded to higher than normal magnitudes following injury of a complementary joint restraint.

  10. Functional electrical stimulation to the abdominal wall muscles synchronized with the expiratory flow does not induce muscle fatigue.

    PubMed

    Okuno, Yukako; Takahashi, Ryoichi; Sewa, Yoko; Ohse, Hirotaka; Imura, Shigeyuki; Tomita, Kazuhide

    2017-03-01

    [Purpose] Continuous electrical stimulation of abdominal wall muscles is known to induce mild muscle fatigue. However, it is not clear whether this is also true for functional electrical stimulation delivered only during the expiratory phase of breathing. This study aimed to examine whether or not intermittent electrical stimulation delivered to abdominal wall muscles induces muscle fatigue. [Subjects and Methods] The subjects were nine healthy adults. Abdominal electrical stimulation was applied for 1.5 seconds from the start of expiration and then turned off during inspiration. The electrodes were attached to both sides of the abdomen at the lower margin of the 12th rib. Abdominal electrical stimulation was delivered for 15 minutes with the subject in a seated position. Expiratory flow was measured during stimulus. Trunk flexor torque and electromyography activity were measured to evaluate abdominal muscle fatigue. [Results] The mean stimulation on/off ratio was 1:2.3. The declining rate of abdominal muscle torque was 61.1 ± 19.1% before stimulus and 56.5 ± 20.9% after stimulus, not significantly different. The declining rate of mean power frequency was 47.8 ± 11.7% before stimulus and 47.9 ± 10.2% after stimulus, not significantly different. [Conclusion] It was found that intermittent electrical stimulation to abdominal muscles synchronized with the expiratory would not induce muscle fatigue.

  11. Functional electrical stimulation to the abdominal wall muscles synchronized with the expiratory flow does not induce muscle fatigue

    PubMed Central

    Okuno, Yukako; Takahashi, Ryoichi; Sewa, Yoko; Ohse, Hirotaka; Imura, Shigeyuki; Tomita, Kazuhide

    2017-01-01

    [Purpose] Continuous electrical stimulation of abdominal wall muscles is known to induce mild muscle fatigue. However, it is not clear whether this is also true for functional electrical stimulation delivered only during the expiratory phase of breathing. This study aimed to examine whether or not intermittent electrical stimulation delivered to abdominal wall muscles induces muscle fatigue. [Subjects and Methods] The subjects were nine healthy adults. Abdominal electrical stimulation was applied for 1.5 seconds from the start of expiration and then turned off during inspiration. The electrodes were attached to both sides of the abdomen at the lower margin of the 12th rib. Abdominal electrical stimulation was delivered for 15 minutes with the subject in a seated position. Expiratory flow was measured during stimulus. Trunk flexor torque and electromyography activity were measured to evaluate abdominal muscle fatigue. [Results] The mean stimulation on/off ratio was 1:2.3. The declining rate of abdominal muscle torque was 61.1 ± 19.1% before stimulus and 56.5 ± 20.9% after stimulus, not significantly different. The declining rate of mean power frequency was 47.8 ± 11.7% before stimulus and 47.9 ± 10.2% after stimulus, not significantly different. [Conclusion] It was found that intermittent electrical stimulation to abdominal muscles synchronized with the expiratory would not induce muscle fatigue. PMID:28356636

  12. Plantar flexor muscle weakness and fatigue in spastic cerebral palsy patients.

    PubMed

    Neyroud, Daria; Armand, Stéphane; De Coulon, Geraldo; Sarah R Dias Da Silva; Maffiuletti, Nicola A; Kayser, Bengt; Place, Nicolas

    2017-02-01

    Patients with cerebral palsy develop an important muscle weakness which might affect the aetiology and extent of exercise-induced neuromuscular fatigue. This study evaluated the aetiology and extent of plantar flexor neuromuscular fatigue in patients with cerebral palsy. Ten patients with cerebral palsy and 10 age- and sex-matched healthy individuals (∼20 years old, 6 females) performed four 30-s maximal isometric plantar flexions interspaced by a resting period of 2-3s to elicit a resting twitch. Maximal voluntary contraction force, voluntary activation level and peak twitch were quantified before and immediately after the fatiguing task. Before fatigue, patients with cerebral palsy were weaker than healthy individuals (341±134N vs. 858±151N, p<0.05) and presented lower voluntary activation (73±19% vs. 90±9%, p<0.05) and peak twitch (100±28N vs. 199±33N, p<0.05). Maximal voluntary contraction force was not significantly reduced in patients with cerebral palsy following the fatiguing task (-10±23%, p>0.05), whereas it decreased by 30±12% (p<0.05) in healthy individuals. Plantar flexor muscles of patients with cerebral palsy were weaker than their healthy peers but showed greater fatigue resistance. Cerebral palsy is a widely defined pathology that is known to result in muscle weakness. The extent and origin of muscle weakness were the topic of several previous investigations; however some discrepant results were reported in the literature regarding how it might affect the development of exercise-induced neuromuscular fatigue. Importantly, most of the studies interested in the assessment of fatigue in patients with cerebral palsy did so with general questionnaires and reported increased levels of fatigue. Yet, exercise-induced neuromuscular fatigue was quantified in just a few studies and it was found that young patients with cerebral palsy might be more fatigue resistant that their peers. Thus, it appears that (i) conflicting results exist regarding

  13. Muscle mechanical properties of strength and endurance athletes and changes after one week of intensive training.

    PubMed

    de Paula Simola, Rauno Álvaro; Raeder, Christian; Wiewelhove, Thimo; Kellmann, Michael; Meyer, Tim; Pfeiffer, Mark; Ferrauti, Alexander

    2016-10-01

    The study investigates whether tensiomyography (TMG) is sensitive to differentiate between strength and endurance athletes, and to monitor fatigue after either one week of intensive strength (ST) or endurance (END) training. Fourteen strength (24.1±2.0years) and eleven endurance athletes (25.5±4.8years) performed an intensive training period of 6days of ST or END, respectively. ST and END groups completed specific performance tests as well as TMG measurements of maximal radial deformation of the muscle belly (Dm), deformation time between 10% and 90% Dm (Tc), rate of deformation development until 10% Dm (V10) and 90% Dm (V90) before (baseline), after training period (post1), and after 72h of recovery (post2). Specific performance of both groups decreased from baseline to post1 (P<0.05) and returned to baseline values at post2 (P<0.05). The ST group showed higher countermovement jump (P<0.05) and shorter Tc (P<0.05) at baseline. After training, Dm, V10, and V90 were reduced in the ST (P<0.05) while TMG changes were less pronounced in the END. TMG could be a useful tool to differentiate between strength and endurance athletes, and to monitor fatigue and recovery especially in strength training. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Fatigue resistance of rat extraocular muscles does not depend on creatine kinase activity.

    PubMed

    McMullen, Colleen A; Hayess, Katrin; Andrade, Francisco H

    2005-08-17

    Creatine kinase (CK) links phosphocreatine, an energy storage system, to cellular ATPases. CK activity serves as a temporal and spatial buffer for ATP content, particularly in fast-twitch skeletal muscles. The extraocular muscles are notoriously fast and active, suggesting the need for efficient ATP buffering. This study tested the hypotheses that (1) CK isoform expression and activity in rat extraocular muscles would be higher, and (2) the resistance of these muscles to fatigue would depend on CK activity. We found that mRNA and protein levels for cytosolic and mitochondrial CK isoforms were lower in the extraocular muscles than in extensor digitorum longus (EDL). Total CK activity was correspondingly decreased in the extraocular muscles. Moreover, cytoskeletal components of the sarcomeric M line, where a fraction of CK activity is found, were downregulated in the extraocular muscles as was shown by immunocytochemistry and western blotting. CK inhibition significantly accelerated the development of fatigue in EDL muscle bundles, but had no major effect on the extraocular muscles. Searching for alternative ATP buffers that could compensate for the relative lack of CK in extraocular muscles, we determined that mRNAs for two adenylate kinase (AK) isoforms were expressed at higher levels in these muscles. Total AK activity was similar in EDL and extraocular muscles. These data indicate that the characteristic fatigue resistance of the extraocular muscles does not depend on CK activity.

  15. Preliminary Study on Fatigue Strengths of Fretted Ti-48Al-2Cr-2Nb

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.

    2002-01-01

    The fatigue behavior (stress-life curve) of gamma titanium aluminide (Ti-48Al-2Cr-2Nb, atomic percent) was examined by conducting two tests: first, a fretting wear test with a fatigue specimen in contact with a typical nickel-based superalloy contact pad in air at temperatures of 296 and 823 K and second, a high-cycle fatigue test of the prefretted Ti-48Al-2Cr-2Nb fatigue specimen at 923 K. Reference high-cycle fatigue tests were also conducted with unfretted Ti-48Al-2Cr-2Nb specimens at 923 K. All Ti-48Al-2Cr-2Nb fatigue specimens were machined from cast slabs. The results indicate that the stress-life results for the fretted Ti-48Al-2Cr-2Nb specimens exhibited a behavior similar to those of the unfretted Ti-48Al-2Cr-2Nb specimens. The values of maximum stress and life for the fretted specimens were almost the same as those for the unfretted specimens. The resultant stress-life curve for the unfretted fatigue specimens was very flat. The flat appearance in the stress-life curve of the unfretted specimens is attributed to the presence of a high density of casting pores. The fatigue strengths of both the fretted and unfretted specimens can be significantly affected by the presence of this porosity, which can decrease the fatigue life of Ti-48Al-2Cr-2Nb. The presence of the porosity made discerning the effect of fretting damage on fatigue strength and life of the specimens difficult.

  16. Muscle fatigue, nNOS and muscle fiber atrophy in limb girdle muscular dystrophy.

    PubMed

    Angelini, Corrado; Tasca, Elisabetta; Nascimbeni, Anna Chiara; Fanin, Marina

    2014-12-01

    Muscle fatigability and atrophy are frequent clinical signs in limb girdle muscular dystrophy (LGMD), but their pathogenetic mechanisms are still poorly understood. We review a series of different factors that may be connected in causing fatigue and atrophy, particularly considering the role of neuronal nitric oxide synthase (nNOS) and additional factors such as gender in different forms of LGMD (both recessive and dominant) underlying different pathogenetic mechanisms. In sarcoglycanopathies, the sarcolemmal nNOS reactivity varied from absent to reduced, depending on the residual level of sarcoglycan complex: in cases with complete sarcoglycan complex deficiency (mostly in beta-sarcoglycanopathy), the sarcolemmal nNOS reaction was absent and it was always associated with early severe clinical phenotype and cardiomyopathy. Calpainopathy, dysferlinopathy, and caveolinopathy present gradual onset of fatigability and had normal sarcolemmal nNOS reactivity. Notably, as compared with caveolinopathy and sarcoglycanopathies, calpainopathy and dysferlinopathy showed a higher degree of muscle fiber atrophy. Males with calpainopathy and dysferlinopathy showed significantly higher fiber atrophy than control males, whereas female patients have similar values than female controls, suggesting a gender difference in muscle fiber atrophy with a relative protection in females. In female patients, the smaller initial muscle fiber size associated to endocrine factors and less physical effort might attenuate gender-specific muscle loss and atrophy.

  17. Relationship between weight loss and parameters of skeletal muscle function in patients with advanced cancer and fatigue.

    PubMed

    Morgado, P Cresta; Giorlando, A; Castro, M; Navigante, A

    2016-09-01

    This study aims to determine the influence of significant weight loss on parameters of skeletal muscle function in a population of advanced cancer patients with fatigue. A cross-sectional and comparative study was designed between two arms of advanced cancer patients with fatigue (fatigue numeral scale (FNS) ≥4). A arm (n = 27) with ≥5 % weight loss in the last 6 months, and B arm (n = 22) without weight loss. Muscle strength was examined by hand grip technique and measurements of body composition by bioimpedance analysis (BIA), values of hemoglobin, albumin, lactic dehydrogenase (LDH), c-reactive protein (CRP), urine creatinine, and FNS. These variables were compared between both groups and correlated within each group. here were no differences concerning parameters of muscle strength between both arms. A arm had values of CRP ≥10 ug/dl in 77 % compared with 38.5 % of B arm (p = 0.004). A arm showed a higher percentage of body cell mass (%BCM) than B arm (p = 0.005). The A arm also showed a lower percentage of fat mass (%FM) (p = 0.014) when compared to the B arm. FNS was higher in A arm (median 7 vs 5; p = 0.047). All the variables of muscle strength had a significant positive correlation. In A arm, BCM had a negative significant correlation with CRP (p = 0.021). In this study, significant weight loss and high CRP did not have influence on parameters of skeletal muscular function. We consider that further studies should be necessary, preferably with longitudinal designs to evaluate these findings.

  18. Factors that affect the fatigue strength of power transmission shafting and their impact on design

    NASA Technical Reports Server (NTRS)

    Leowenthal, S. H.

    1986-01-01

    A long standing objective in the design of power transmission shafting is to eliminate excess shaft material without compromising operational reliability. A shaft design method is presented which accounts for variable amplitude loading histories and their influence on limited life designs. The effects of combined bending and torsional loading are considered along with a number of application factors known to influence the fatigue strength of shafting materials. Among the factors examined are surface condition, size, stress concentration, residual stress and corrosion fatigue.

  19. Age-Related Differences in Muscle Fatigue Vary by Contraction Type: A Meta-analysis

    PubMed Central

    Avin, Keith G.

    2011-01-01

    Background During senescence, despite the loss of strength (force-generating capability) associated with sarcopenia, muscle endurance may improve for isometric contractions. Purpose The purpose of this study was to perform a systematic meta-analysis of young versus older adults, considering likely moderators (ie, contraction type, joint, sex, activity level, and task intensity). Data Sources A 2-stage systematic review identified potential studies from PubMed, CINAHL, PEDro, EBSCOhost: ERIC, EBSCOhost: Sportdiscus, and The Cochrane Library. Study Selection Studies reporting fatigue tasks (voluntary activation) performed at a relative intensity in both young (18–45 years of age) and old (≥55 years of age) adults who were healthy were considered. Data Extraction Sample size, mean and variance outcome data (ie, fatigue index or endurance time), joint, contraction type, task intensity (percentage of maximum), sex, and activity levels were extracted. Data Synthesis Effect sizes were (1) computed for all data points; (2) subgrouped by contraction type, sex, joint or muscle group, intensity, or activity level; and (3) further subgrouped between contraction type and the remaining moderators. Out of 3,457 potential studies, 46 publications (with 78 distinct effect size data points) met all inclusion criteria. Limitations A lack of available data limited subgroup analyses (ie, sex, intensity, joint), as did a disproportionate spread of data (most intensities ≥50% of maximum voluntary contraction). Conclusions Overall, older adults were able to sustain relative-intensity tasks significantly longer or with less force decay than younger adults (effect size=0.49). However, this age-related difference was present only for sustained and intermittent isometric contractions, whereas this age-related advantage was lost for dynamic tasks. When controlling for contraction type, the additional modifiers played minor roles. Identifying muscle endurance capabilities in the older

  20. Age-related differences in muscle fatigue vary by contraction type: a meta-analysis.

    PubMed

    Avin, Keith G; Law, Laura A Frey

    2011-08-01

    During senescence, despite the loss of strength (force-generating capability) associated with sarcopenia, muscle endurance may improve for isometric contractions. The purpose of this study was to perform a systematic meta-analysis of young versus older adults, considering likely moderators (ie, contraction type, joint, sex, activity level, and task intensity). A 2-stage systematic review identified potential studies from PubMed, CINAHL, PEDro, EBSCOhost: ERIC, EBSCOhost: Sportdiscus, and The Cochrane Library. Studies reporting fatigue tasks (voluntary activation) performed at a relative intensity in both young (18-45 years of age) and old (≥ 55 years of age) adults who were healthy were considered. Sample size, mean and variance outcome data (ie, fatigue index or endurance time), joint, contraction type, task intensity (percentage of maximum), sex, and activity levels were extracted. Effect sizes were (1) computed for all data points; (2) subgrouped by contraction type, sex, joint or muscle group, intensity, or activity level; and (3) further subgrouped between contraction type and the remaining moderators. Out of 3,457 potential studies, 46 publications (with 78 distinct effect size data points) met all inclusion criteria. A lack of available data limited subgroup analyses (ie, sex, intensity, joint), as did a disproportionate spread of data (most intensities ≥ 50% of maximum voluntary contraction). Overall, older adults were able to sustain relative-intensity tasks significantly longer or with less force decay than younger adults (effect size=0.49). However, this age-related difference was present only for sustained and intermittent isometric contractions, whereas this age-related advantage was lost for dynamic tasks. When controlling for contraction type, the additional modifiers played minor roles. Identifying muscle endurance capabilities in the older adult may provide an avenue to improve functional capabilities, despite a clearly established decrement in

  1. Fatigue strength of a Ti-6Al-4V alloy produced by selective laser melting

    NASA Astrophysics Data System (ADS)

    Gerov, M. V.; Vladislavskaya, E. Yu.; Terent'ev, V. F.; Prosvirnin, D. V.; Kolmakov, A. G.; Antonova, O. S.

    2016-10-01

    The fatigue properties and the fracture mechanisms of the Ti-6Al-4V alloy produced by selective laser melting (SLM) from a powder of an CL41TiELI titanium alloy have been studied. Cylindrical blanks were grown at angles of 90° and 45° to a platform. The best fatigue strength is observed in the samples the blanks of which were grown at an angle of 45°. It is found that the structure of the SLM material can contain portions with unmelted powder particles, which are the places of initiation of fatigue cracks.

  2. Fatigue Performance of Advanced High-Strength Steels (AHSS) GMAW Joints

    SciTech Connect

    Feng, Zhili; Sang, Yan; Jiang, Cindy; Chiang, Dr. John; Kuo, Dr. Min

    2009-01-01

    The fatigue performance of gas metal arc welding (GMAW) joints of advanced high strength steels (AHSS) are compared and analyzed. The steel studied included a number of different grades of AHSS and baseline mild steels: DP600, DP780, DP980, M130, M220, solution annealed boron steel, fully hardened boron steels, HSLA690 and DR210 (a mild steel). Fatigue testing was conducted under a number of nominal stress ranges to obtain the S/N curves of the weld joints. A two-phase analytical model is developed to predict the fatigue performance of AHSS welds. It was found that there are appreciable differences in the fatigue S/N curves among different AHSS joints made using the same welding practices, suggesting that the local microstructure in the weld toe and root region plays non-negligible role in the fatigue performance of AHSS welds. Changes in weld parameters can influence the joint characteristics which in turn influence fatigue life of the weld joints, particularly of those of higher strength AHSS. The analytical model is capable of reasonably predicting the fatigue performance of welds made with various steel grades in this study.

  3. Initial and fatigue bond strengths of chromatic and light-cured adhesives.

    PubMed

    Lee, June M L; Georgiou, George; Jones, Steven P

    2010-11-01

    To compare the initial and fatigue shear bond strengths of a chromatic adhesive with a light-cured adhesive in an ex vivo laboratory study. Hydroxyapatite discs were used as the bonding substrate. They were produced by cold uni-axial compression at 20 tons, sintered at 1300 degrees C and embedded in epoxy resin before grinding and polishing. One hundred and fifty upper left central incisor brackets were bonded to the discs with Transbond PLUS Color Change (3M Unitek, Monrovia, CA, USA) while another 150 similar brackets were bonded with Transbond XT (3M Unitek, Monrovia, CA, USA). Seventy-five brackets from each group were subjected to cyclic loading (5000 cycles at 2 Hz) at 50 per cent of the mean bond strength in a Dartec Series HC 10 Testing Machine. Initial (unfatigued) and fatigued bond strengths were determined by applying a shear force at the bracket-substrate interface using a custom-made metal jig in an Instron Universal Testing Machine. One-way ANOVA with Bonferroni post-hoc correction and two-way ANOVA were used to analyse the differences between the initial and fatigue mean shear bond strengths of the adhesives. The survival and bond reliability of both adhesives were evaluated with the Kaplan-Meier and Cox regression analyses. The initial mean shear bond strength for Transbond PLUS Color Change (16.72 MPa) was higher than Transbond XT (15.11 MPa), but this was not statistically significant (p = 0.109). The fatigue mean shear bond strength for Transbond XT (15.87 MPa) was similar to that of Transbond PLUS Color Change (15.33 MPa), and the difference was not statistically significant (p > 0.999). There were no significant differences when the effects of the material (p = 0.264) or fatiguing (p = 0.512) were considered separately, but in combination, the effect on bond strength was statistically significant (p = 0.026). The survival analysis showed that both adhesives demonstrated similar survival patterns in the unfatigued and fatigued states. Analysis

  4. Fatigue strength of common tibial intramedullary nail distal locking screws

    PubMed Central

    Griffin, Lanny V; Harris, Robert M; Zubak, Joseph J

    2009-01-01

    Background Premature failure of either the nail and/or locking screws with unstable fracture patterns may lead to angulation, shortening, malunion, and IM nail migration. Up to thirty percent of all unreamed nail locking screws can break after initial weight bearing is allowed at 8–10 weeks if union has not occurred. The primary problem this presents is hardware removal during revision surgery. The purposes of our study was to evaluate the relative fatigue resistance of distal locking screws and bolts from representative manufacturers of tibial IM nail systems, and develop a relative risk assessment of screws and materials used. Evaluations included quantitative and qualitative measures of the relative performance of these screws. Methods Fatigue tests were conducted to simulate a comminuted fracture that was treated by IM nailing assuming that all load was carried by the screws. Each screw type was tested ten times in a single screw configuration. One screw type was tested an additional ten times in a two-screw parallel configuration. Fatigue tests were performed using a servohydraulic materials testing system and custom fixturing that simulated screws placed in the distal region of an appropriately sized tibial IM nail. Fatigue loads were estimated based on a seventy-five kilogram individual at full weight bearing. The test duration was one million cycles (roughly one year), or screw fracture, whichever occurred first. Failure analysis of a representative sample of titanium alloy and stainless steel screws included scanning electron microscopy (SEM) and quantitative metallography. Results The average fatigue life of a single screw with a diameter of 4.0 mm was 1200 cycles, which would correspond roughly to half a day of full weight bearing. Single screws with a diameter of 4.5 mm or larger have approximately a 50 percent probability of withstanding a week of weight bearing, whereas a single 5.0 mm diameter screw has greater than 90 percent probability of

  5. Fatigue strength of common tibial intramedullary nail distal locking screws.

    PubMed

    Griffin, Lanny V; Harris, Robert M; Zubak, Joseph J

    2009-04-16

    Premature failure of either the nail and/or locking screws with unstable fracture patterns may lead to angulation, shortening, malunion, and IM nail migration. Up to thirty percent of all unreamed nail locking screws can break after initial weight bearing is allowed at 8-10 weeks if union has not occurred. The primary problem this presents is hardware removal during revision surgery. The purposes of our study was to evaluate the relative fatigue resistance of distal locking screws and bolts from representative manufacturers of tibial IM nail systems, and develop a relative risk assessment of screws and materials used. Evaluations included quantitative and qualitative measures of the relative performance of these screws. Fatigue tests were conducted to simulate a comminuted fracture that was treated by IM nailing assuming that all load was carried by the screws. Each screw type was tested ten times in a single screw configuration. One screw type was tested an additional ten times in a two-screw parallel configuration. Fatigue tests were performed using a servohydraulic materials testing system and custom fixturing that simulated screws placed in the distal region of an appropriately sized tibial IM nail. Fatigue loads were estimated based on a seventy-five kilogram individual at full weight bearing. The test duration was one million cycles (roughly one year), or screw fracture, whichever occurred first. Failure analysis of a representative sample of titanium alloy and stainless steel screws included scanning electron microscopy (SEM) and quantitative metallography. The average fatigue life of a single screw with a diameter of 4.0 mm was 1200 cycles, which would correspond roughly to half a day of full weight bearing. Single screws with a diameter of 4.5 mm or larger have approximately a 50 percent probability of withstanding a week of weight bearing, whereas a single 5.0 mm diameter screw has greater than 90 percent probability of withstanding more than a week of

  6. Abdominal muscle and quadriceps strength in chronic obstructive pulmonary disease

    PubMed Central

    Man, W; Hopkinson, N; Harraf, F; Nikoletou, D; Polkey, M; Moxham, J

    2005-01-01

    Background: Quadriceps muscle weakness is common in chronic obstructive pulmonary disease (COPD) but is not observed in a small hand muscle (adductor pollicis). Although this could be explained by reduced activity in the quadriceps, the observation could also be explained by anatomical location of the muscle or fibre type composition. However, the abdominal muscles are of a similar anatomical and fibre type distribution to the quadriceps, although they remain active in COPD. Cough gastric pressure is a recently described technique that assesses abdominal muscle (and hence expiratory muscle) strength more accurately than traditional techniques. A study was undertaken to test the hypothesis that more severe weakness exists in the quadriceps than in the abdominal muscles of patients with COPD compared with healthy elderly controls. Methods: Maximum cough gastric pressure and quadriceps isometric strength were measured in 43 patients with stable COPD and 25 healthy elderly volunteers matched for anthropometric variables. Results: Despite a significant reduction in mean quadriceps strength (29.9 kg v 41.2 kg; 95% CI –17.9 to –4.6; p = 0.001), cough gastric pressure was preserved in patients with COPD (227.3 cm H2O v 204.8 cm H2O; 95% CI –5.4 to 50.6; p = 0.11). Conclusions: Abdominal muscle strength is preserved in stable COPD outpatients in the presence of quadriceps weakness. This suggests that anatomical location and fibre type cannot explain quadriceps weakness in COPD. By inference, we conclude that disuse and consequent deconditioning are important factors in the development of quadriceps muscle weakness in COPD patients, or that activity protects the abdominal muscles from possible systemic myopathic processes. PMID:15923239

  7. Effects of successive judo matches on fatigue and muscle damage markers.

    PubMed

    Detanico, Daniele; Dal Pupo, Juliano; Franchini, Emerson; Dos Santos, Saray G

    2015-04-01

    This study aimed to investigate the acute effects of simulated judo matches on fatigue and muscle damage markers. Twenty male judo athletes participated in this study. The athletes performed three 5-minute judo matches separated by 15 minutes of passive rest between each match. The following measurements were performed before and after each match: shoulder external/internal rotation isokinetic torque and countermovement jump (CMJ). Blood samples were taken before the first match and after the third match for serum creatine kinase (CK) and lactate dehydrogenase (LDH) analysis. T-tests for dependent samples and analysis of variance for repeated measures were used to compare the variables over the time; the level of significance was set at 0.05. An overall effect of the successive matches on shoulder internal (PTIN) and external (PTEX) rotation peak torque and CMJ performance was observed. PTIN and PTEX showed significant decreases in postmatch 2 and postmatch 3 when compared with the baseline (p < 0.01). Also, CMJ height declined in postmatch 2 and postmatch 3 (p < 0.01) when compared with the baseline. Serum CK and LDH activity increased significantly after the third match (p < 0.01). It was concluded that 3 successive judo matches induced a decline of peak torque and muscle power in the upper and lower limbs, respectively, and also provoked an increase of muscle damage markers. These findings may provide important knowledge for coaches and physical trainers to improve judo-specific strength training in both the upper and lower limbs.

  8. The association between hip muscle cross-sectional area, muscle strength, and bone mineral density.

    PubMed

    Ahedi, Harbeer; Aitken, Dawn; Scott, David; Blizzard, Leigh; Cicuttini, Flavia; Jones, Graeme

    2014-07-01

    Studies examining the association between muscle size, muscle strength, and bone mineral density (BMD) are limited. Thus, this study aimed to describe the association between hip muscles cross-sectional area (CSA), muscle strength, and BMD of the hip and spine. A total of 321 subjects from the Tasmanian Older Adult Cohort study with a right hip MRI scan conducted between 2004 and 2006 were included. Hip muscles were measured on MR images by OsiriX (Geneva) software measuring maximum muscle CSA (cm(2)) of gluteus maximus, obturator externus, gemelli, quadratus femoris, piriformis, pectineus, sartorius, and iliopsoas. Dual-energy X-ray absorptiometry measured total hip, femoral neck, and spine BMD, and lower limb muscle strength was assessed by dynamometer. Muscle CSA of the hip flexors (pectineus, sartorius, and iliopsoas) and the hip rotators, obturator externus, and quadratus femoris were associated with both total hip and femoral neck BMD (all p < 0.05). The associations between CSA of pectineus and sartorius and BMD were stronger in women (p = 0.01-0.001) compared to men (p = 0.12-0.54). Additionally, only gemelli CSA was associated with BMD of the spine (p = 0.002). Gluteus maximus and piriformis showed no relationship with BMD. CSA of most hip muscles (except gluteus maximus and gemelli) were positively associated with leg strength (p = 0.02 to <0.001). Lastly, leg strength was weakly associated with BMD (p = 0.11-0.007). Hip muscle CSA, and to a lesser extent muscle strength, were positively associated with hip BMD. These data suggest that both higher muscle mass and strength may contribute to the maintenance of bone mass and prevention of disease progression in older adults.

  9. Muscle strength: A better index of low physical performance than muscle mass in older adults.

    PubMed

    Kim, Yeo Hyung; Kim, Kwang-Il; Paik, Nam-Jong; Kim, Ki-Woong; Jang, Hak Chul; Lim, Jae-Young

    2016-05-01

    The most appropriate muscle index for the definition of sarcopenia has not been agreed on. We aimed to investigate the associations of muscle mass and strength with 5-year mortality and low physical performance. We included 560 participants aged 65 years or older in the analysis. Muscle and fat mass were assessed by dual-energy X-ray absorptiometry. Leg muscle and grip strength were measured using dynamometers. The clinical outcomes were 5-year mortality and low physical performance (Short Physical Performance Battery score < 9) in 5 years. Associations between muscle indices and clinical outcomes were analyzed. A Cox proportional hazard model for mortality and a logistic regression model for physical performance were used. Decreases in leg muscle and grip strength were significantly associated with 5-year mortality and low physical performance in both sexes. Total muscle mass in men and appendicular skeletal mass in both sexes were associated with mortality, but not with low physical performance. Lower leg muscle strength (OR 0.107; P = 0.020) was an independent predictor of low physical performance in women after adjusting for age, fat, cognition, and depression. Lower leg muscle (OR 0.123; P = 0.031) and lower grip strength (OR 0.950; P = 0.012) were independent predictors of low physical performance in men. Muscle strength is a better indicator of 5-year adverse clinical outcomes of mortality and low physical performance than muscle mass. Muscle strength was an independent predictor of low physical performance in 5 years. Geriatr Gerontol Int 2016; 16: 577-585. © 2015 Japan Geriatrics Society.

  10. Fatigue and Impact Strength of Diffusion Bonded Titanium Alloy Joints

    DTIC Science & Technology

    1989-02-01

    specimen was machined to give either a Rolls-Royce rotating bend fatigue test piece or a Hounsfield impact test piece with the bond- line at the middle...specimens were machined to give Hounsfield impact test pieces. One of the metallographic specimens was also used for microhardness and electron probe...8217high’ void level condition was 3..:i lower than that of the controls. The Hounsfield impact values obtained for the 12.7 mm dia specimens (Fig 4

  11. Residual strength of composite laminates subjected to tensile-compressive fatigue loading

    NASA Technical Reports Server (NTRS)

    Rotem, Assa; Nelson, H. G.

    1990-01-01

    Results are presented on the measurements of the residual strengths of T300/934 graphite epoxy laminates, in tension and in compression, after the samples were exposed to tension-compression fatigue loading (R = -1). Four laminate ocnfigurations were tested: unidirectional, cross-ply, angle-ply, and quasi-isotropic. It was found that the fatigue behavior of laminates was dependent on the quasi-static strengths and the specific structure of the laminate. No direct correlation was found between remaining residual strengths and the percentage of average fatigue life. However, a correlation scheme was developed for the individual specimen under test, based on a cumulative damage model and a stiffness change of the material.

  12. Comparison of Bending Fatigue Strength among Spur Gears Manufactured by Various Methods

    NASA Astrophysics Data System (ADS)

    Yamanaka, Masashi; Matsushima, Yu; Miwa, Shinji; Narita, Yukihito; Inoue, Katsumi; Kawasaki, Yoshiki

    This paper deals with an experimental evaluation of bending fatigue strengths for hobbed, forged, sintered and austempered ductile iron (ADI) spur gears. The module is 2.5 and the number of teeth is 26 in the test gears. The materials of the test gears are SCr420H for hobbed and forged gears, prealloyed powder metal with 1.5 wt.% Mo for sintered gears, and FCAD 1100-15 for ADI gears. All gears except ADI gears were carburized. The pulsator bending fatigue tests were carried out for the test gears. Then the relationship between the strength and the manufacturing cost is obtained. The forged gear has the high strength of 3% and low cost compared with the hobbed gear. It is the best among the four gears. The sintered and ADI gears have approximately half the strength and cost of the hobbed gear. These gears are effective when cost is a high priority. In the progress of the fatigue tests, comparisons of strength among gears having different tooth-root forms were needed. The nominal stress obtained from actual measured profile data using a noncontact-type measuring machine is suitable for comparing the fatigue strength in gears having different root forms.

  13. Postural strategy changes with fatigue of the lumbar extensor muscles.

    PubMed

    Wilson, Erin L; Madigan, Michael L; Davidson, Bradley S; Nussbaum, Maury A

    2006-04-01

    The purpose of this study was to investigate the effect of lumbar extensor fatigue on postural strategy in response to a balance perturbation. Anteriorly-directed force perturbations were applied to the upper back with a padded pendulum and attempted to challenge the postural control system without eliciting a stepping response. In three separate sessions, subjects were perturbed both before and after a fatiguing protocol that induced lumbar extensor fatigue to one of three different fatigue levels. Postural strategy was quantified using center of pressure position along with joint angles and joint torques for the ankle, knee, hip, and "low back" joints. Results showed both proactive and reactive changes in postural strategy. Proactive changes involved a slight anterior lean prior to the perturbation, and reactive changes were consistent with a shift toward more of a hip strategy with fatigue. In addition, results suggested that subjects classified as moving mostly at the hip prior to fatigue were more affected by fatigue compared to subjects classified as moving roughly equal amounts at the ankle and hip prior to fatigue. Increasing fatigue level exaggerated some, but not all, of the changes in postural strategy with fatigue. These findings illustrate that neuromuscular fatigue can influence postural strategy in response to a balance perturbation.

  14. FATIGUE AND RECOVERY FROM DYNAMIC CONTRACTIONS IN MEN AND WOMEN DIFFER FOR ARM AND LEG MUSCLES

    PubMed Central

    SENEFELD, JONATHON; YOON, TEJIN; BEMENT, MARIE HOEGER; HUNTER, SANDRA K.

    2014-01-01

    Introduction Whether there is a gender difference in fatigue and recovery from maximal velocity fatiguing contractions and across muscles is not understood. Methods 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). Results 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. Conclusions The gender difference in muscle fatigue often observed during isometric tasks was diminished during fast dynamic contractions for upper and lower limb muscles. PMID:23494882

  15. Respiratory muscle training increases respiratory muscle strength and reduces respiratory complications after stroke: a systematic review.

    PubMed

    Menezes, Kênia Kp; Nascimento, Lucas R; Ada, Louise; Polese, Janaine C; Avelino, Patrick R; Teixeira-Salmela, Luci F

    2016-07-01

    After stroke, does respiratory muscle training increase respiratory muscle strength and/or endurance? Are any benefits carried over to activity and/or participation? Does it reduce respiratory complications? Systematic review of randomised or quasi-randomised trials. Adults with respiratory muscle weakness following stroke. Respiratory muscle training aimed at increasing inspiratory and/or expiratory muscle strength. Five outcomes were of interest: respiratory muscle strength, respiratory muscle endurance, activity, participation and respiratory complications. Five trials involving 263 participants were included. The mean PEDro score was 6.4 (range 3 to 8), showing moderate methodological quality. Random-effects meta-analyses showed that respiratory muscle training increased maximal inspiratory pressure by 7 cmH2O (95% CI 1 to 14) and maximal expiratory pressure by 13 cmH2O (95% CI 1 to 25); it also decreased the risk of respiratory complications (RR 0.38, 95% CI 0.15 to 0.96) compared with no/sham respiratory intervention. Whether these effects carry over to activity and participation remains uncertain. This systematic review provided evidence that respiratory muscle training is effective after stroke. Meta-analyses based on five trials indicated that 30minutes of respiratory muscle training, five times per week, for 5 weeks can be expected to increase respiratory muscle strength in very weak individuals after stroke. In addition, respiratory muscle training is expected to reduce the risk of respiratory complications after stroke. Further studies are warranted to investigate whether the benefits are carried over to activity and participation. PROSPERO (CRD42015020683). [Menezes KKP, Nascimento LR, Ada L, Polese JC, Avelino PR, Teixeira-Salmela LF (2016) Respiratory muscle training increases respiratory muscle strength and reduces respiratory complications after stroke: a systematic review.Journal of Physiotherapy62: 138-144]. Copyright © 2016 Australian

  16. Kinesiology Tape or Compression Sleeve Applied to the Thigh Does Not Improve Balance or Muscle Activation Before or Following Fatigue.

    PubMed

    Cavanaugh, M Tyler; Quigley, Patrick J; Hodgson, Daniel D; Reid, Jonathan C; Behm, David G

    2016-07-01

    Cavanaugh, MT, Quigley, PJ, Hodgson, DD, Reid, JC, and Behm, DG. Kinesiology tape or compression sleeve applied to the thigh does not improve balance or muscle activation before or following fatigue. J Strength Cond Res 30(7): 1992-2000, 2016-Compression sleeves (CS) and kinesiology tape (KT) are purported to enhance proprioception, however, there is substantial conflict in the literature. Because the beneficial effects of CS and KT are more evident in the literature with recovery, the objective of this study was to examine the effects of CS and KT on balance under acute nonfatigued and postfatigued conditions. Using a within-subject, repeated-measures design, 12 university participants (5 females and 7 males) performed in a random order CS, KT, and Control conditions. Two trials of each test were conducted before the application of CS or KT (pretest 1), immediately after the application (pretest 2), with posttests at 1 and 10 minutes after 4 sets of unilateral Bulgarian squats to failure (1 minute rest between sets). Tests included a Y balance test (measures: distance reached by nondominant foot in anterior, posterior lateral, and posterior medial directions) and drop jump landing balance test from a 50-cm platform (measures: ground reaction force, electromyography, and center of pressure). The fatigue protocol induced 25.3% decrease in unilateral squat repetitions from set 1 to set 4. There were no significant condition main effects or interactions for any balance measure or EMG before or after fatigue. In conclusion, independent of fatigue, there was no significant effect of CS or KT on balance outcomes immediately and up to 10 minutes following the fatiguing intervention. Thus, nonfatigued or muscles weakened by fatigue did not benefit from CS and KT application.

  17. The effect of exercise training with an additional inspiratory load on inspiratory muscle fatigue and time-trial performance.

    PubMed

    McEntire, Serina J; Smith, Joshua R; Ferguson, Christine S; Brown, Kelly R; Kurti, Stephanie P; Harms, Craig A

    2016-08-01

    The purpose was to determine the effect of moderate-intensity exercise training (ET) on inspiratory muscle fatigue (IMF) and if an additional inspiratory load during ET (ET+IL) would further improve inspiratory muscle strength, IMF, and time-trial performance. 15 subjects were randomly divided to ET (n=8) and ET+IL groups (n=7). All subjects completed six weeks of exercise training three days/week at ∼70%V̇O2peak for 30min. The ET+IL group breathed through an inspiratory muscle trainer (15% PImax) during exercise. 5-mile, and 30-min time-trials were performed pre-training, weeks three and six. Inspiratory muscle strength increased (p<0.05) for both groups to a similar (p>0.05) extent. ET and ET+IL groups improved (p<0.05) 5-mile time-trial performance (∼10% and ∼18%) and the ET+IL group was significantly faster than ET at week 6. ET and ET+IL groups experienced less (p<0.05) IMF compared to pre-training following the 5-mile time-trial. In conclusion, these data suggest ET leads to less IMF, ET+IL improves inspiratory muscle strength and IMF, but not different than ET alone.

  18. Effect of tooth whitening strips on fatigue resistance and flexural strength of bovine dentin in vitro

    PubMed Central

    Kim, Namhee; De Souza, Grace M.

    2017-01-01

    Objective To determine the effects of whitening strips on bovine dentin fatigue resistance and flexural strength in vitro. Materials and methods A total of eighty bovine dentin specimens (2x2x17mm) were treated with either: control glycerine gel on plastic film wrap or whitening strips containing 9.5% hydrogen peroxide. Treatment was applied for 30 minutes, twice a day, for 1- or 4-weeks. After the last treatment, ten specimens per group were randomly selected to undergo fatigue testing (106 cycles, 3Hz, 20N) while the other ten were subjected to flexural strength testing after ten days of storage in artificial saliva. Kaplan-Meier method with a log rank test, Wilcoxon test and Cox regression were used to assess fatigue test results (p<0.05). One-way ANOVA and Tukey’s tests were used to compare the flexural strength results (p<0.05). Results There were significant differences in survival during the fatigue test among the groups (p<0.001). Treatment (control or bleach) was a significant factor for specimen survival (p<0.001, Exp(B) = 33.45). There were significant differences in mean flexural strength (p<0.001). No significant difference was found between “1-wk control” and “4-wk control”. The mean flexural strength and fatigue resistance of the “4-wk bleach” were significantly lower than all the other groups. Conclusions The use of whitening strips reduced the fatigue resistance and flexural strength of bovine dentin in vitro. Until the effect of whitening strips on mechanical properties of human dentin is fully elucidated, it remains prudent to advise patients to avoid excessive direct use of whitening strips on dentin. PMID:28278191

  19. Effect of tooth whitening strips on fatigue resistance and flexural strength of bovine dentin in vitro.

    PubMed

    Tam, Laura E; Kim, Namhee; De Souza, Grace M

    2017-01-01

    To determine the effects of whitening strips on bovine dentin fatigue resistance and flexural strength in vitro. A total of eighty bovine dentin specimens (2x2x17mm) were treated with either: control glycerine gel on plastic film wrap or whitening strips containing 9.5% hydrogen peroxide. Treatment was applied for 30 minutes, twice a day, for 1- or 4-weeks. After the last treatment, ten specimens per group were randomly selected to undergo fatigue testing (106 cycles, 3Hz, 20N) while the other ten were subjected to flexural strength testing after ten days of storage in artificial saliva. Kaplan-Meier method with a log rank test, Wilcoxon test and Cox regression were used to assess fatigue test results (p<0.05). One-way ANOVA and Tukey's tests were used to compare the flexural strength results (p<0.05). There were significant differences in survival during the fatigue test among the groups (p<0.001). Treatment (control or bleach) was a significant factor for specimen survival (p<0.001, Exp(B) = 33.45). There were significant differences in mean flexural strength (p<0.001). No significant difference was found between "1-wk control" and "4-wk control". The mean flexural strength and fatigue resistance of the "4-wk bleach" were significantly lower than all the other groups. The use of whitening strips reduced the fatigue resistance and flexural strength of bovine dentin in vitro. Until the effect of whitening strips on mechanical properties of human dentin is fully elucidated, it remains prudent to advise patients to avoid excessive direct use of whitening strips on dentin.

  20. [Analysis of surface electromyography on repetitive lifting task-induced fatigue of back muscles].

    PubMed

    Chen, Jing; Ding, Jia-Shun; Wang, Zheng-Lun; Yang, Lei

    2004-12-01

    Using surface electromyography (SEMG) technique to evaluate repetitive lifting task-induced fatigue of back muscles. Thirteen volunteers lifted and lowered an 8 kg weight from floor to waist level for 100 times. Fatigue in the erector spinae muscles was quantified by comparing the frequency content of the EMG signal during static contractions performed before, and immediately after the 100 lifts. EMG average amplitude rose gradually during 100 lifts, the difference was significant at T10 right (P < 0.05) and L3 left (P < 0.01), the difference was not significant at T10 left and L3 right (P > 0.05). The median frequency intercept at T10 right, T10 left, L3 right, L3 left erector spinae muscles decreased by 2.0% (P > 0.05) 10.9% and 29.9% (P < 0.05), 27.9% (P < 0.01), respectively. The mean power frequency intercept decreased by 9% at L3 left erector spinae muscle (P < 0.05), the decrease was not statistically significant at other sites (P > 0.05). Repetitive lifting may induce measurable fatigue in the erector spinae muscles. Erector spinae muscle at L3 is more easily fatigued than at T10. Using the median frequency intercept to assess muscle fatigue is more sensitive than using mean power frequency intercept.

  1. Relation between upper-limb muscle strength with exercise capacity, quality of life and dyspnea in patients with severe chronic obstructive pulmonary disease.

    PubMed

    Kaymaz, Dicle; Candemir, İpek Çaylı; Ergün, Pınar; Demir, Neşe; Taşdemir, Filiz; Demir, Pervin

    2017-06-15

    In chronic obstructive pulmonary disease (COPD), skeletal muscle weakness is characterized by reduced muscle strength, reduced muscle endurance and the presence of muscle fatigue especially in lower limbs. There has been little research into the upper limb skeletal muscles. In this study, we aimed to investigate the relation of upper limb muscle strength with pulmonary function, exercise capacity, quality of life (QoL) and dyspnea sensation. Eigthy-eight patients (89.8% male; age: 64.2 ± 8.7 years) with COPD (FEV1 = 34.2% ± 15.2%) were evaluated. Tests included hand grip strength and actual 1-repetition maximum (1RM) test for upper limb strength. Dyspnea sensation was assessed with medical research council (MRC) scale. St. George Respiratory Questionary (SGRQ) was used to evaluate patients health related QoL. Exercise capacity was evaluated with incremental shuttle walk test and endurance shuttle walk test. Upper limb muscle strength correlated with exercise capacity but no correlations were found with pulmonary functions.There were negative correlations with all the domains of SGRQ both actual 1RM and handgrip strength. MRC scores revealed a negative correlation with upper limb muscle strength. In our study, we showed that upper limb muscle strength correlated with exercise capacity, QoL, dyspnea sensation. Identifying patients who have greater reductions in strength will allow early interventions with a multidisciplinary manner. © 2017 John Wiley & Sons Ltd.

  2. Fatigue strength reduction model: RANDOM3 and RANDOM4 user manual. Appendix 2: Development of advanced methodologies for probabilistic constitutive relationships of material strength models

    NASA Technical Reports Server (NTRS)

    Boyce, Lola; Lovelace, Thomas B.

    1989-01-01

    FORTRAN programs RANDOM3 and RANDOM4 are documented in the form of a user's manual. Both programs are based on fatigue strength reduction, using a probabilistic constitutive model. The programs predict the random lifetime of an engine component to reach a given fatigue strength. The theoretical backgrounds, input data instructions, and sample problems illustrating the use of the programs are included.

  3. Cancer cachexia decreases specific force and accelerates fatigue in limb muscle

    SciTech Connect

    Roberts, B.M.; Frye, G.S.; Ahn, B.; Ferreira, L.F.; Judge, A.R.

    2013-06-07

    Highlights: •C-26 cancer cachexia causes a significant decrease in limb muscle absolute force. •C-26 cancer cachexia causes a significant decrease in limb muscle specific force. •C-26 cancer cachexia decreases fatigue resistance in the soleus muscle. •C-26 cancer cachexia prolongs time to peak twitch tension in limb muscle. •C-26 cancer cachexia prolongs one half twitch relaxation time in limb muscle. -- Abstract: Cancer cachexia is a complex metabolic syndrome that is characterized by the loss of skeletal muscle mass and weakness, which compromises physical function, reduces quality of life, and ultimately can lead to mortality. Experimental models of cancer cachexia have recapitulated this skeletal muscle atrophy and consequent decline in muscle force generating capacity. However, more recently, we provided evidence that during severe cancer cachexia muscle weakness in the diaphragm muscle cannot be entirely accounted for by the muscle atrophy. This indicates that muscle weakness is not just a consequence of muscle atrophy but that there is also significant contractile dysfunction. The current study aimed to determine whether contractile dysfunction is also present in limb muscles during severe Colon-26 (C26) carcinoma cachexia by studying the glycolytic extensor digitorum longus (EDL) muscle and the oxidative soleus muscle, which has an activity pattern that more closely resembles the diaphragm. Severe C-26 cancer cachexia caused significant muscle fiber atrophy and a reduction in maximum absolute force in both the EDL and soleus muscles. However, normalization to muscle cross sectional area further demonstrated a 13% decrease in maximum isometric specific force in the EDL and an even greater decrease (17%) in maximum isometric specific force in the soleus. Time to peak tension and half relaxation time were also significantly slowed in both the EDL and the solei from C-26 mice compared to controls. Since, in addition to postural control, the oxidative

  4. Effect of fatigue on torque output and electromyographic measures of trunk muscles during isometric axial rotation.

    PubMed

    Ng, Joseph K-F; Parnianpour, Mohamad; Richardson, Carolyn A; Kippers, Vaughan

    2003-03-01

    To examine the changes in torque output resulting from fatigue, as well as changes in electromyographic measures of trunk muscles during isometric axial rotation and to compare these changes between directions of axial rotation. Subjects performed fatiguing right and left isometric axial rotation of the trunk at 80% of maximum voluntary contraction while standing upright. A rehabilitation center. Twenty-three men with no history of back pain. Not applicable. Surface electromyographic signals were recorded from 6 trunk muscles bilaterally. The primary torque in the transverse plane and the coupling torques in sagittal and coronal planes were also measured. During the fatiguing axial rotation contraction, coupling torques of both sagittal and coronal planes were slightly decreased and no difference was found between directions of axial rotation. Decreasing median frequency and an increase in electromyographic amplitude were also found in trunk muscles with different degrees of changes in individual muscles. There were significant differences (P<.05) between right and left axial rotation exertions in median frequency slope of external oblique, internal oblique, latissimus dorsi, and iliocostalis lumborum muscles, but no such difference was found in median frequency slope of rectus abdominis and multifidus muscles. This could be attributed to different functional roles among the muscles. Similar differences (P<.05) between right and left axial rotation in median frequency slope were also detected in the electromyographic amplitude slope of the trunk muscles. Coefficient of variation of the torque output and electromyographic activation in most of the trunk muscles increased during the fatigue process. The changing coupling torque, different fatigue rate, and activation changes of trunk muscles, as well as the increase in variability during fatiguing axial rotation exertion, could affect the internal loading and stability of the spine; this needs to be further

  5. Errors in force generation and changes in controlling patterns following agonist muscle fatigue.

    PubMed

    Huang, Yi-Ming; Chang, Ya-Ju; Hsu, Miao-Ju; Chen, Chia-Ling; Fang, Chia-Ying; Wong, Alice May-Kuen

    2009-11-01

    The purpose of this study was to evaluate whether agonist muscle fatigue changed the coactivation time and the co-contraction magnitude of the agonist and antagonist muscle, and if the agonist muscle fatigue produced bias (constant error: CE) and inconsistency (variable error: VE) of the force. Subjects are 10 healthy people and one person with impaired proprioception. EMG and force for fast (0.19 +/- 0.06 s) and slow (1.20 +/- 0.44 s) targeted isometric dorsiflexions were recorded before and after fatigue of the dorsiflexors. The results revealed that the coactivation time increased after fatigue only in the slow contractions but the co-contraction magnitude did not change. The postfatigue increment of the CE was greater in the fast contractions than in the slow ones. We conclude that the postfatigue compensatory strategy can reduce the fatigue-induced bias. The change of muscles activation level after fatigue might be under the influence of the common drive. Impaired proprioception is a possible cause of the fatigue-related increase in bias and inconsistency.

  6. Discrete wavelet transform analysis of surface electromyography for the fatigue assessment of neck and shoulder muscles.

    PubMed

    Chowdhury, Suman Kanti; Nimbarte, Ashish D; Jaridi, Majid; Creese, Robert C

    2013-10-01

    Assessment of neuromuscular fatigue is essential for early detection and prevention of risks associated with work-related musculoskeletal disorders. In recent years, discrete wavelet transform (DWT) of surface electromyography (SEMG) has been used to evaluate muscle fatigue, especially during dynamic contractions when the SEMG signal is non-stationary. However, its application to the assessment of work-related neck and shoulder muscle fatigue is not well established. Therefore, the purpose of this study was to establish DWT analysis as a suitable method to conduct quantitative assessment of neck and shoulder muscle fatigue under dynamic repetitive conditions. Ten human participants performed 40min of fatiguing repetitive arm and neck exertions while SEMG data from the upper trapezius and sternocleidomastoid muscles were recorded. The ten of the most commonly used wavelet functions were used to conduct the DWT analysis. Spectral changes estimated using power of wavelet coefficients in the 12-23Hz frequency band showed the highest sensitivity to fatigue induced by the dynamic repetitive exertions. Although most of the wavelet functions tested in this study reasonably demonstrated the expected power trend with fatigue development and recovery, the overall performance of the "Rbio3.1" wavelet in terms of power estimation and statistical significance was better than the remaining nine wavelets.

  7. Spatially distributed sequential stimulation reduces fatigue in paralyzed triceps surae muscles: a case study.

    PubMed

    Nguyen, Robert; Masani, Kei; Micera, Silvestro; Morari, Manfred; Popovic, Milos R

    2011-12-01

    Functional electrical stimulation (FES) is limited by the rapid onset of muscle fatigue caused by localized nerve excitation repeatedly activating only a subset of motor units. The purpose of this study was to investigate reducing fatigue by sequentially changing, pulse by pulse, the area of stimulation using multiple surface electrodes that cover the same area as one electrode during conventional stimulation. Paralyzed triceps surae muscles of an individual with complete spinal cord injury were stimulated, via the tibial nerve, through four active electrodes using spatially distributed sequential stimulation (SDSS) that was delivered by sending a stimulation pulse to each electrode one after another with 90° phase shift between successive electrodes. For comparison, single electrode stimulation was delivered through one active electrode. For both modes of stimulation, the resultant frequency to the muscle as a whole was 40 Hz. Isometric ankle torque was measured during fatiguing stimulations lasting 2 min. Each mode of stimulation was delivered a total of six times over 12 separate days. Three fatigue measures were used for comparison: fatigue index (final torque normalized to maximum torque), fatigue time (time for torque to drop by 3 dB), and torque-time integral (over the entire trial). The measures were all higher during SDSS (P < 0.001), by 234, 280, and 171%, respectively. The results are an encouraging first step toward addressing muscle fatigue, which is one of the greatest problems for FES.

  8. Dominant component in muscle fatigue induced hand tremor during laparoscopic surgical manipulation.

    PubMed

    Chandra, Sourav; Hayashibe, Mitsuhiro; Thondiyath, Asokan

    2014-01-01

    Accuracy of laparoscopic surgery gets affected by the hand tremor of the surgeons. Though cognitive load is inevitable in such activity which promotes tremor, muscle fatigue induced tremor is significant among the most important sources of tremor. Characteristic of fatigue induced hand tremor and its dominant directional properties are reported in this work. For a fixed laparoscopic tool grip with temporally synchronized predefined task protocols, characteristics of fatigue induced tremors have been studied. Dominant component of tremor was found to be in the sagittal plane in case of both static and dynamic tasks. In order to relate it with the muscle fatigue level, spectral properties of surface electromyography (SEMG) were also investigated simultaneously. A study of transient effect on tool positioning was also included, which conjointly advocates the other experimental results on fatigue induced hand tremor as well.

  9. Variation of neck muscle strength along the human cervical spine.

    PubMed

    Oi, Nelson; Pandy, Marcus G; Myers, Barry S; Nightingale, Roger W; Chancey, Valeta Carol

    2004-11-01

    The aim of this study was to describe and explain the variation of neck muscle strength along the cervical spine. A three-dimensional model of the head-neck complex was developed to test the hypothesis that the moment-generating capacity of the neck musculature is lower in the upper cervical spine than in the lower cervical spine. The model calculations suggest that the neck muscles can protect the lower cervical spine from injury during extension and lateral bending. The maximum flexor moment developed in the lower cervical spine was 2 times higher than that developed in the upper spine. The model also predicted that the neck musculature is 30% stronger in the lower cervical spine during lateral bending. Peak compressive forces (up to 3 times body weight) were higher in the lower cervical spine. These results are consistent with the clinical finding that extension loading of the neck often leads to injuries in the upper cervical spine. Analysis of the model results showed that neck flexor strength was greater in the lower cervical spine because of the relatively large size of the sternocleidomastoid muscle. The hyoid muscles developed significant flexor moments about the joints of the upper cervical spine, as these muscles had relatively large flexor moment arms; however, this effect was offset by the action of the sternocleidomastoid, which exerted a large extensor moment in the upper spine. Lateral bending strength of the neck muscles was governed by geometry (i.e., moment arms) rather than by muscle size.

  10. Dynamic versus isometric electromechanical delay in non-fatigued and fatigued muscle: A combined electromyographic, mechanomyographic, and force approach.

    PubMed

    Smith, Cory M; Housh, Terry J; Hill, Ethan C; Johnson, Glen O; Schmidt, Richard J

    2017-04-01

    This study used a combined electromyographic, mechanomyographic, and force approach to identify electromechanical delay (EMD) from the onsets of the electromyographic to force signals (EMDE-F), onsets of the electromyographic to mechanomyogrpahic signals (EMDE-M), and onsets of mechanomyographic to force signals (EMDM-F). The purposes of the current study were to examine: (1) the differences in EMDE-F, EMDE-M, and EMDM-F from the vastus lateralis during maximal, voluntary dynamic (1 repetition maximum [1-RM]) and isometric (maximal voluntary isometric contraction [MVIC]) muscle actions; and (2) the effects of fatigue on EMDE-F, EMDM-F, and EMDE-M. Ten men performed pretest and posttest 1-RM and MVIC leg extension muscle actions. The fatiguing workbout consisted of 70% 1-RM dynamic constant external resistance leg extension muscle actions to failure. The results indicated that there were no significant differences between 1-RM and MVIC EMDE-F, EMDE-M, or EMDM-F. There were, however, significant fatigue-induced increases in EMDE-F (94% and 63%), EMDE-M (107%), and EMDM-F (63%) for both the 1-RM and MVIC measurements. Therefore, these findings demonstrated the effects of fatigue on EMD measures and supported comparisons among studies which examined dynamic or isometric EMD measures from the vastus lateralis using a combined electromyographic, mechanomyographic, and force approach. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Intercostal and forearm muscle deoxygenation during respiratory fatigue in patients with heart failure: potential role of a respiratory muscle metaboreflex.

    PubMed

    Moreno, A M; Castro, R R T; Silva, B M; Villacorta, H; Sant'Anna Junior, M; Nóbrega, A C L

    2014-11-01

    The purpose of this study was to determine the effect of respiratory muscle fatigue on intercostal and forearm muscle perfusion and oxygenation in patients with heart failure. Five clinically stable heart failure patients with respiratory muscle weakness (age, 66 ± 12 years; left ventricle ejection fraction, 34 ± 3%) and nine matched healthy controls underwent a respiratory muscle fatigue protocol, breathing against a fixed resistance at 60% of their maximal inspiratory pressure for as long as they could sustain the predetermined inspiratory pressure. Intercostal and forearm muscle blood volume and oxygenation were continuously monitored by near-infrared spectroscopy with transducers placed on the seventh left intercostal space and the left forearm. Data were compared by two-way ANOVA and Bonferroni correction. Respiratory fatigue occurred at 5.1 ± 1.3 min in heart failure patients and at 9.3 ± 1.4 min in controls (P<0.05), but perceived effort, changes in heart rate, and in systolic blood pressure were similar between groups (P>0.05). Respiratory fatigue in heart failure reduced intercostal and forearm muscle blood volume (P<0.05) along with decreased tissue oxygenation both in intercostal (heart failure, -2.6 ± 1.6%; controls, +1.6 ± 0.5%; P<0.05) and in forearm muscles (heart failure, -4.5 ± 0.5%; controls, +0.5 ± 0.8%; P<0.05). These results suggest that respiratory fatigue in patients with heart failure causes an oxygen demand/delivery mismatch in respiratory muscles, probably leading to a reflex reduction in peripheral limb muscle perfusion, featuring a respiratory metaboreflex.

  12. Effects of Neuromuscular Fatigue on Quadriceps Strength and Activation and Knee Biomechanics in Individuals Post-Anterior Cruciate Ligament Reconstruction and Healthy Adults.

    PubMed

    Thomas, Abbey C; Lepley, Lindsey K; Wojtys, Edward M; McLean, Scott G; Palmieri-Smith, Riann M

    2015-12-01

    Laboratory-based experiment using a pretest/posttest design. To determine the effects of neuromuscular fatigue on quadriceps strength and activation and sagittal and frontal plane knee biomechanics during dynamic landing following anterior cruciate ligament reconstruction (ACLR). Impaired quadriceps central activation occurs post-ACLR, likely altering lower extremity biomechanics. Neuromuscular fatigue similarly reduces volitional muscle activation and impairs neuromuscular control. Upon return to full activity post-ACLR, individuals likely concurrently experience quadriceps central activation deficits and neuromuscular fatigue, though the effects of fatigue on muscle strength and activation and biomechanics post-ACLR are unknown. Seventeen individuals 7 to 10 months post-ACLR and 16 controls participated. Quadriceps strength and central activation ratio were recorded prefatigue and postfatigue, which was induced via sets of double-leg squats. Knee biomechanics were recorded during a dynamic landing activity prefatigue and postfatigue. Both groups demonstrated smaller knee flexion (initial contact, P = .017; peak, P = .004) and abduction (initial contact, P = .005; peak, P = .009) angles postfatigue. The ACLR group had smaller peak knee flexion angles (P<.001) prefatigue and postfatigue than controls. Knee flexion moment was smaller in those post-ACLR than controls prefatigue (P<.001), but not postfatigue (P = .103). Controls had smaller knee flexion moments postfatigue (P = .001). Knee abduction moment was smaller in both groups postfatigue (P = .003). All participants demonstrated significantly lower strength (P<.001) and activation (P = .003) postfatigue. Impaired strength, central activation, and biomechanics were present postfatigue in both groups, suggesting that neuromuscular fatigue may increase noncontact ACL injury risk. However, these changes were not exaggerated in those post-ACLR, likely because they already demonstrated a stiff-legged landing strategy

  13. Effects of alpha-cyano-4-hydroxycinnamic acid on fatigue and recovery of isolated mouse muscle.

    PubMed

    Clarke, P D; Clift, D L; Dooldeniya, M; Burnett, C A; Curtin, N A

    1995-12-01

    Fatigue and recovery of mouse soleus and extensor digitorum longus muscles were investigated in standard saline and in saline containing the lactate + hydrogen ion transport blocker, alpha-cyano-4-hydroxycinnamic acid (cinnamate). The fatigue protocol was a series of brief isometric tetani which reduced isometric force by about 25%. Recovery was monitored by test tetani during recovery. Both muscles recovered completely in standard saline. Soleus muscle also recovered completely in the presence of cinnamate, whereas extensor digitorum longus hardly recovered at all. Force during fatigue and recovery can be described in a mathematical simulation in which force depends on intracellular inorganic phosphate and pH, and the only effect of cinnamate is to block lactate + hydrogen ion transport. The results of the simulation suggest that during the fatiguing series of tetani pH changes are small and have a negligible effect on force, but pH is a major determinant of the timecourse of recovery in extensor digitorum longus.

  14. Assessment of Muscle Fatigue Associated with Prolonged Standing in the Workplace

    PubMed Central

    Omar, Abdul Rahman; Saman, Alias Mohd; Othman, Ibrahim

    2012-01-01

    Objectives The objectives of this study were to determine the psychological fatigue and analyze muscle activity of production workers who are performing processes jobs while standing for prolonged time periods. Methods The psychological fatigue experienced by the workers was obtained through questionnaire surveys. Meanwhile, muscle activity has been analyzed using surface electromyography (sEMG) measurement. Lower extremities muscles include: erector spinae, tibialis anterior, and gastrocnemius were concurrently measured for more than five hours of standing. Twenty male production workers in a metal stamping company participated as subjects in this study. The subjects were required to undergo questionnaire surveys and sEMG measurement. Results Results of the questionnaire surveys found that all subjects experienced psychological fatigue due to prolonged standing jobs. Similarly, muscle fatigue has been identified through sEMG measurement. Based on the non-parametric statistical test using the Spearman's rank order correlation, the left erector spinae obtained a moderate positive correlation and statistically significant (rs = 0.552, p < 0.05) between the results of questionnaire surveys and sEMG measurement. Conclusion Based on this study, the authors concluded that prolonged standing was contributed to psychological fatigue and to muscle fatigue among the production workers. PMID:22953228

  15. Effects of fatigue on lower limb, pelvis and trunk kinematics and muscle activation: Gender differences.

    PubMed

    Lessi, Giovanna Camparis; Dos Santos, Ana Flávia; Batista, Luis Fylipe; de Oliveira, Gabriela Clemente; Serrão, Fábio Viadanna

    2017-02-01

    Muscle fatigue is associated with biomechanical changes that may lead to anterior cruciate ligament (ACL) injuries. Alterations in trunk and pelvis kinematics may also be involved in ACL injury. Although some studies have compared the effects of muscle fatigue on lower limb kinematics between men and women, little is known about its effects on pelvis and trunk kinematics. The aim of the study was to compare the effects of fatigue on lower limb, pelvis and trunk kinematics and muscle activation between men and women during landing. The participants included forty healthy subjects. We performed kinematic analysis of the trunk, pelvis, hip and knee and muscle activation analysis of the gluteal muscles, vastus lateralis and biceps femoris, during a single-leg landing before and after fatigue. Men had greater trunk flexion than women after fatigue. After fatigue, a decrease in peak knee flexion and an increase in Gmax and BF activation were observed. The increase in the trunk flexion can decrease the anterior tibiofemoral shear force resulted from the lower knee flexion angle, thereby decreasing the stress on the ACL. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Muscle strength and knee range of motion after femoral lengthening

    PubMed Central

    Bhave, Anil; Shabtai, Lior; Woelber, Erik; Apelyan, Arman; Paley, Dror; Herzenberg, John E

    2017-01-01

    Background and purpose Femoral lengthening may result in decrease in knee range of motion (ROM) and quadriceps and hamstring muscle weakness. We evaluated preoperative and postoperative knee ROM, hamstring muscle strength, and quadriceps muscle strength in a diverse group of patients undergoing femoral lengthening. We hypothesized that lengthening would not result in a significant change in knee ROM or muscle strength. Patients and methods This prospective study of 48 patients (mean age 27 (9–60) years) compared ROM and muscle strength before and after femoral lengthening. Patient age, amount of lengthening, percent lengthening, level of osteotomy, fixation time, and method of lengthening were also evaluated regarding knee ROM and strength. The average length of follow-up was 2.9 (2.0–4.7) years. Results Mean amount of lengthening was 5.2 (2.4–11.0) cm. The difference between preoperative and final knee flexion ROM was 2° for the overall group. Congenital shortening cases lost an average of 5% or 6° of terminal knee flexion, developmental cases lost an average of 3% or 4°, and posttraumatic cases regained all motion. The difference in quadriceps strength at 45° preoperatively and after lengthening was not statistically or clinically significant (2.7 Nm; p = 0.06). Age, amount of lengthening, percent lengthening, osteotomy level, fixation time, and lengthening method had no statistically significant influence on knee ROM or quadriceps strength at final follow-up. Interpretation Most variables had no effect on ROM or strength, and higher age did not appear to be a limiting factor for femoral lengthening. Patients with congenital causes were most affected in terms of knee flexion. PMID:27892743

  17. Damage formation, fatigue behavior and strength properties of ZrO2-based ceramics

    NASA Astrophysics Data System (ADS)

    Kozulin, A. A.; Narikovich, A. S.; Kulkov, S. N.; Leitsin, V. N.; Kulkov, S. S.

    2016-08-01

    It is suggested that a non-destructive testing technique using a three-dimensional X-ray tomography be applied to detecting internal structural defects and monitoring damage formation in a ceramic composite structure subjected to a bending load. Three-point bending tests are used to investigate the fatigue behavior and mechanical and physical properties of medical-grade ZrO2-based ceramics. The bending strength and flexural modulus are derived under static conditions at a loading rate of 2 mm/min. The fatigue strength and fatigue limit under dynamic loading are investigated at a frequency of 10 Hz in three stress ranges: 0.91-0.98, 0.8-0.83, and 0.73-0.77 MPa of the static bending strength. The average values of the bending strength and flexural modulus of sintered specimens are 43 MPa and 22 GPa, respectively. The mechanical properties of the ceramics are found to be similar to those of bone tissues. The testing results lead us to conclude that the fatigue limit obtained from 105 stress cycles is in the range 33-34 MPa, i.e. it accounts for about 75% of the static bending strength for the test material.

  18. Damage formation, fatigue behavior and strength properties of ZrO{sub 2}-based ceramics

    SciTech Connect

    Kozulin, A. A. Kulkov, S. S.; Narikovich, A. S.; Leitsin, V. N.; Kulkov, S. N.

    2016-08-02

    It is suggested that a non-destructive testing technique using a three-dimensional X-ray tomography be applied to detecting internal structural defects and monitoring damage formation in a ceramic composite structure subjected to a bending load. Three-point bending tests are used to investigate the fatigue behavior and mechanical and physical properties of medical-grade ZrO{sub 2}-based ceramics. The bending strength and flexural modulus are derived under static conditions at a loading rate of 2 mm/min. The fatigue strength and fatigue limit under dynamic loading are investigated at a frequency of 10 Hz in three stress ranges: 0.91–0.98, 0.8–0.83, and 0.73–0.77 MPa of the static bending strength. The average values of the bending strength and flexural modulus of sintered specimens are 43 MPa and 22 GPa, respectively. The mechanical properties of the ceramics are found to be similar to those of bone tissues. The testing results lead us to conclude that the fatigue limit obtained from 10{sup 5} stress cycles is in the range 33–34 MPa, i.e. it accounts for about 75% of the static bending strength for the test material.

  19. Nicorandil improves post-fatigue tension in slow skeletal muscle fibers by modulating glutathione redox state.

    PubMed

    Sánchez-Duarte, E; Trujillo, X; Cortés-Rojo, C; Saavedra-Molina, A; Camargo, G; Hernández, L; Huerta, M; Montoya-Pérez, R

    2017-04-01

    Fatigue is a phenomenon in which force reduction has been linked to impairment of several biochemical processes. In skeletal muscle, the ATP-sensitive potassium channels (KATP) are actively involved in myoprotection against metabolic stress. They are present in sarcolemma and mitochondria (mitoKATP channels). K(+) channel openers like nicorandil has been recognized for their ability to protect skeletal muscle from ischemia-reperfusion injury, however, the effects of nicorandil on fatigue in slow skeletal muscle fibers has not been explored, being the aim of this study. Nicorandil (10 μM), improved the muscle function reversing fatigue as increased post-fatigue tension in the peak and total tension significantly with respect to the fatigued condition. However, this beneficial effect was prevented by the mitoKATP channel blocker 5-hydroxydecanoate (5-HD, 500 μM) and by the free radical scavenger N-2-mercaptopropionyl glycine (MPG, 1 mM), but not by the nitric oxide (NO) synthase inhibitor Nω-nitro-L-arginine methyl ester (L-NAME, 100 μM). Nicorandil also decreased lipid peroxidation and maintained both reduced glutathione (GSH) levels and an elevated GSH/GSSG ratio, whereas total glutathione (TGSH) remained unaltered during post-fatigue tension. In addition, NO production, measured through nitrite concentrations was significantly increased with nicorandil during post-fatigue tension; this increase remained unaltered in the presence of nicorandil plus L-NAME, nonetheless, this effect was reversed with nicorandil plus MPG. Hence, these results suggest that nicorandil improves the muscle function reversing fatigue in slow skeletal muscle fibers of chicken through its effects not only as a mitoKATP channel opener but also as NO donor and as an antioxidant.

  20. Influence of knee flexion angle and age on triceps surae muscle fatigue during heel raises.

    PubMed

    Hébert-Losier, Kim; Schneiders, Anthony G; García, José A; Sullivan, S John; Simoneau, Guy G

    2012-11-01

    The triceps surae (TS) muscle-tendon unit is 1 of the most commonly injured in elite and recreational athletes, with a high prevalence in middle-aged adults. The performance of maximal numbers of unilateral heel raises is used to assess, train, and rehabilitate TS endurance and conventionally prescribed in 0° knee flexion (KF) for the gastrocnemius and 45° for the soleus (SOL). However, the extent of muscle selectivity conferred through the change in the knee angle is lacking for heel raises performed to volitional fatigue. This study investigated the influence of knee angle on TS muscle fatigue during heel raises and determined whether fatigue differed between middle-aged and younger-aged adults. Forty-eight healthy individuals aged 18-25 and 35-45 years performed maximal numbers of unilateral heel raises in 0° and 45° KF. Median frequencies and linear regression slopes were calculated from the SOL, gastrocnemius medialis (GM), and gastrocnemius lateralis (GL) surface electromyographic signals. Stepwise mixed-effect regressions were used for analysis. The subjects completed an average of 45 and 48 heel raises in 0° and 45° KF, respectively. The results indicated that the 3 muscles fatigued during testing as all median frequencies decreased, and regression slopes were negative. Consistent with muscle physiology and fiber typing, fatigue was greater in the GM and GL than in the SOL (p < 0.001). However, knee angle did not influence TS muscle fatigue parameters (p = 0.814), with similar SOL, GM, and GL fatigue in 0° and 45° KF. These findings are in contrast with the traditionally described clinical use of heel raises in select knee angles for the gastrocnemius and the SOL. Furthermore, no difference in TS fatigue between the 2 age groups was able to be determined, despite the reported higher prevalence of injury in middle-aged individuals.

  1. Evaluation of Respiratory Muscle Strength in Mouth Breathers: Clinical Evidences

    PubMed Central

    Andrade da Cunha, Renata; Andrade da Cunha, Daniele; Assis, Roberta Borba; Bezerra, Luciana Ângelo; Justino da Silva, Hilton

    2013-01-01

    Introduction The child who chronically breathes through the mouth may develop a weakness of the respiratory muscles. Researchers and clinical are seeking for methods of instrumental evaluation to gather complementary data to clinical evaluations. With this in mind, it is important to evaluate breathing muscles in the child with Mouth Breathing. Objective To develop a review to investigate studies that used evaluation methods of respiratory muscle strength in mouth breathers. Data Synthesis  The authors were unanimous in relation to manovacuometry method as a way to evaluate respiratory pressures in Mouth Breathing children. Two of them performed with an analog manovacuometer and the other one, digital. The studies were not evaluated with regard to the method efficacy neither the used instruments. Conclusion There are few studies evaluating respiratory muscle strength in Mouth Breathing people through manovacuometry and the low methodological rigor of the analyzed studies hindered a reliable result to support or refuse the use of this technique. PMID:25992108

  2. Apple Pomace Extract Improves Endurance in Exercise Performance by Increasing Strength and Weight of Skeletal Muscle.

    PubMed

    Jeong, Ji-Woong; Shim, Jae-Jung; Choi, Il-Dong; Kim, Sung-Hwan; Ra, Jehyeon; Ku, Hyung Keun; Lee, Dong Eun; Kim, Tae-Youl; Jeung, Woonhee; Lee, Jung-Hee; Lee, Ki Won; Huh, Chul-Sung; Sim, Jae-Hun; Ahn, Young-Tae

    2015-12-01

    Ursolic acid is a lipophilic pentacyclic triterpenoid found in many fruits and herbs and is used in several herbal folk medicines for diabetes. In this study, we evaluated the effects of apple pomace extract (APE; ursolic acid content, 183 mg/g) on skeletal muscle atrophy. To examine APE therapeutic potential in muscle atrophy, we investigated APE effects on the expression of biomarkers associated with muscle atrophy and hypertrophy. We found that APE inhibited atrophy, while inducing hypertrophy in C2C12 myotubes by decreasing the expression of atrophy-related genes and increasing the expression of hypertrophy-associated genes. The in vivo experiments using mice fed a diet with or without APE showed that APE intake increased skeletal muscle mass, as well as grip strength and exercise capacity. In addition, APE significantly improved endurance in the mice, as evidenced by increased exhaustive running time and muscle weight, and reduced the expression of the genes involved in the development of muscle atrophy. APE also decreased the concentration of serum lactate and lactate dehydrogenase, inorganic phosphate, and creatinine, the indicators of accumulated fatigue and exercise-induced stress. These results suggest that APE may be useful as an ergogenic functional food or dietary supplement.

  3. Thigh muscle strength in senior athletes and healthy controls.

    PubMed

    McCrory, Jean L; Salacinski, Amanda J; Hunt, Sarah E; Greenspan, Susan L

    2009-12-01

    Exercise is commonly recommended to counteract aging-related muscle weakness. While numerous exercise intervention studies on the elderly have been performed, few have included elite senior athletes, such as those who participate in the National Senior Games. The extent to which participation in highly competitive exercise affects muscle strength is unknown, as well as the extent to which such participation mitigates any aging-related strength losses. The purpose of this study was to examine isometric thigh muscle strength in selected athletes of the National Senior Games and healthy noncompetitive controls of similar age, as well as to investigate strength changes with aging in both groups. In all, 95 athletes of the Games and 72 healthy controls participated. Of the senior athletes, 43 were runners, 12 cyclists, and 40 swimmers. Three trials of isometric knee flexion and extension strength were collected using a load cell affixed to a custom-designed chair. Strength data were normalized to dual-energy x-ray absorptiometry-obtained lean mass of the leg. A 3-factor multivariate analysis of variance (group x gender x age group) was performed, which included both the extension and flexion variables (alpha = 0.05). Athletes exhibited 38% more extension strength and 66% more flexion strength than the controls (p < 0.001). Strength did not decrease with advancing age in either the athletes or the controls (p = 0.345). In conclusion, senior athletes who participate in highly competitive exercise have greater strength than healthy aged-matched individuals who do not. Neither group displayed the expected strength losses with aging. Our subject cohorts, however, were not typical of those over age 65 years because individuals with existing health conditions were excluded from the study.

  4. Measurement of facial muscle strength in normal subjects.

    PubMed

    Neely, J Gail; Pomerantz, Rebecca G

    2002-09-01

    Muscle strength is a fundamental measure of function for neuromuscular systems; however, mimetic facial muscle strength has never been recorded. The objective of the present feasibility project was to measure facial muscle strength. The study design was a prospective experimental trial in 10 normal subjects. Descriptive statistics, tests, and analysis of variance were used to summarize and compare data. Subjects were selected by convenience following submission and approval of a prospectively designed protocol and consent form to the Human Studies Committee. Application of a force transducer to the central eyebrow and commissure during eyebrow raising, eyelid closing, smiling, and puckering was performed by two methods: surface adhesion method (n = 5) and direct probe application method (n = 5). Data were recorded in pounds. Three repetitions of each movement were made. Rank order of muscle strengths (in pounds) by the surface adhesion technique was as follows: brow, 0.758; eye, 0.549; pucker, 0.387; and smile, 0.307. By direct probe application the rank order of muscle strengths was as follows: eye, 0.880; brow, 0.773; and smile, 0.730. Objective measures of facial motion are crucial for quantitative investigations of preventative, therapeutic, reconstructive, and rehabilitative interventions for facial nerve and muscle lesions. Until the present, objective measures required cross-correlations with current standards that were subjective. This is the first time an actual physical measure of facial muscle function has been performed. The purpose of presenting this preliminary work is to stimulate advancement along this line of research.

  5. Anxiety's Effect on Muscle Activation and Fatigue in Trumpet Players: A Pilot Study.

    PubMed

    Rumsey, Hannah E; Aggarwal, Sahil; Hobson, Erin M; Park, Jeeyn; Pidcoe, Peter

    2015-12-01

    Due to the high percentage of musicians who suffer from musculoskeletal disorders, there is a need for more research in the field of music and medicine. The purpose of this study was to analyze the possible relationship between anxiety, muscle activation, and muscle fatigue in undergraduate trumpet players. Assessment tools included surface electromyography (sEMG) data, State Trait Anxiety Inventory (STAI), and Visual Analogue Scales (VAS) of perceived anxiety. Data were collected from 27 undergraduate music students across five universities (22 males, 5 females) aged 18 to 24 years. The three muscles targeted by the sEMG were the upper trapezius, sternocleidomastoid, and masseter muscles. Participants were randomly divided into two single-blinded groups: (1) anxiety-induction and (2) control. The anxiety-induction group was instructed to play as accurately as possible and informed that mistakes were being counted and evaluated, while the control group was instructed to play without any concern for possible mistakes. The anxiety-induction group was shown to have more masseter muscle activation than the control; the anxiety-induction group also displayed a higher fatigue rate in all three muscles versus the controls. Subjects with high perceived-anxiety (as measured by VAS) displayed higher masseter activation and higher fatigue rates in the upper trapezius and sternocleidomastoid than non-anxious participants. Despite these notable trends, there was no statistical significance for any of the muscle groups for muscle activation or fatigue.

  6. Resistance Training for Muscle Weakness in Multiple Sclerosis: Direct Versus Contralateral Approach in Individuals With Ankle Dorsiflexors' Disparity in Strength.

    PubMed

    Manca, Andrea; Cabboi, Maria Paola; Dragone, Daniele; Ginatempo, Francesca; Ortu, Enzo; De Natale, Edoardo Rosario; Mercante, Beniamina; Mureddu, Giovanni; Bua, Guido; Deriu, Franca

    2017-07-01

    To compare effects of contralateral strength training (CST) and direct strength training of the more affected ankle dorsiflexors on muscle performance and clinical functional outcomes in people with multiple sclerosis (MS) exhibiting interlimb strength asymmetry. Randomized controlled trial. University hospital. Individuals with relapsing-remitting MS (N=30) and mild-to-moderate disability (Expanded Disability Status Scale score ≤6) presenting with ankle dorsiflexors' strength disparity. Participants were randomly assigned to a CST (n=15) or direct strength training (n=15) group performing 6 weeks of maximal intensity strength training of the less or more affected dorsiflexors, respectively. Maximal strength, endurance to fatigue, and mobility outcomes were assessed before, at the intervention end, and at 12-week follow-up. Strength and fatigue parameters were measured after 3 weeks of training (midintervention). In the more affected limb of both groups, pre- to postintervention significant increases in maximal strength (P≤.006) and fatigue endurance (P≤.04) were detected along with consistent retention of these improvements at follow-up (P≤.04). At midintervention, the direct strength training group showed significant improvements (P≤.002), with no further increase at postintervention, despite training continuation. Conversely, the CST group showed nonsignificant strength gains, increasing to significance at postintervention (P≤.003). In both groups, significant pre- to postintervention improvements in mobility outcomes (P≤.03), not retained at follow-up, were observed. After 6 weeks of training, CST proved as effective as direct strength training in enhancing performance of the more affected limb with a different time course, which may have practical implications in management of severely weakened limbs where direct strength training is not initially possible. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc

  7. [Effects of ginsenoside Rb1 on the oxidative stress in the skeletal muscles of rats with postoperative fatigue syndrome].

    PubMed

    Tan, Shan-Jun; Yu, Zhen; Dong, Qian-Tong

    2012-11-01

    To observe the effects of ginsenoside Rb1 (GRb1) on the oxidative stress in the skeletal muscles of rats with postoperative fatigue syndrome (POFS) and to study its anti-fatigue mechanisms. The POFS model was established using resection of 70% of mid-small intestine. Ninety-six Sprague-Dawley (SD) rats were screened using grasping test. The rats were randomly divided into the control group, the model group, and the GRb1 treated group (at 10 mg/kg) by the body weight. The maximum grip strength of rats was detected on the 1st, 3rd, 7th, and 10th day after operation, respectively. The contents of malondialdehyde (MDA), the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX) were detected. Compared with the model group, the maximum grip strength was obviously enhanced on the postoperative day 7 and 10 (P < 0. 05), the MDA content obviously decreased on the postoperative day 3 and 7 (P < 0.05), the SOD activity obviously increased in the GRb1 treated group (P < 0.05). There was no obvious change in the activities of CAT and GSH-PX among the three groups at each time point (P > 0.05). GRb1 could reduce the oxidative stress injury in the skeletal muscles, improve the activities of antioxidant enzymes, and enhance the functions of the skeletal muscles in POFS rats, which may be important reasons for fighting against POFS.

  8. Postpoliomyelitis muscle weakness: a prospective study of quadriceps strength.

    PubMed

    Munin, M C; Jaweed, M M; Staas, W E; Satinsky, A R; Gutierez, G; Herbison, G J

    1991-09-01

    The objective of this study was to evaluate the presence of progressive postpoliomyelitis muscle weakness (PPMW) in affected individuals 20 to 40 years after the initial polio infection. Over a three-year period, the isometric and isokinetic strength of the quadriceps femoris muscle was studied in seven symptomatic patients with previous poliomyelitis (mean = 38.3 years from infection) to determine if quadriceps strength decreased during the three years. Each patient had a quadriceps affected by polio on one side and a clinically nonaffected quadriceps on the contralateral limb. The maximal isometric force and the peak isokinetic force of the affected quadriceps (AQ) and nonaffected quadriceps (NQ) muscles were tested on a computerized isokinetic dynamometer machine at six-month intervals. Isometric force increased significantly, by 29% per year (p less than .02) in the AQ and by 14% per year (p less than .05) in the NQ. Paired analysis to determine the change in strength between the affected and nonaffected muscles for the isometric data showed a mean nonsignificant increase in the AQ of 14% per year (p = .01). The change in peak isokinetic force demonstrated a significant increase in the AQ of 35% per year (p less than .05); whereas, the NQ peak isokinetic force increased 15% per year which was not statistically significant. Paired analysis to determine the change in strength between the affected and nonaffected muscles for the isokinetic data showed a nonsignificant relative increase in the AQ of 20% per year (p less than .06).(ABSTRACT TRUNCATED AT 250 WORDS)

  9. Multiple causes of fatigue during shortening contractions in rat slow twitch skeletal muscle.

    PubMed

    Hortemo, Kristin Halvorsen; Munkvik, Morten; Lunde, Per Kristian; Sejersted, Ole M

    2013-01-01

    Fatigue in muscles that shorten might have other causes than fatigue during isometric contractions, since both cross-bridge cycling and energy demand are different in the two exercise modes. While isometric contractions are extensively studied, the causes of fatigue in shortening contractions are poorly mapped. Here, we investigate fatigue mechanisms during shortening contractions in slow twitch skeletal muscle in near physiological conditions. Fatigue was induced in rat soleus muscles with maintained blood supply by in situ shortening contractions at 37°C. Muscles were stimulated repeatedly (1 s on/off at 30 Hz) for 15 min against a constant load, allowing the muscle to shorten and perform work. Fatigue and subsequent recovery was examined at 20 s, 100 s and 15 min exercise. The effects of prior exercise were investigated in a second exercise bout. Fatigue developed in three distinct phases. During the first 20 s the regulatory protein Myosin Light Chain-2 (slow isoform, MLC-2s) was rapidly dephosphorylated in parallel with reduced rate of force development and reduced shortening. In the second phase there was degradation of high-energy phosphates and accumulation of lactate, and these changes were related to slowing of muscle relengthening and relaxation, culminating at 100 s exercise. Slowing of relaxation was also associated with increased leak of calcium from the SR. During the third phase of exercise there was restoration of high-energy phosphates and elimination of lactate, and the slowing of relaxation disappeared, whereas dephosphorylation of MLC-2s and reduced shortening prevailed. Prior exercise improved relaxation parameters in a subsequent exercise bout, and we propose that this effect is a result of less accumulation of lactate due to more rapid onset of oxidative metabolism. The correlation between dephosphorylation of MLC-2s and reduced shortening was confirmed in various experimental settings, and we suggest MLC-2s as an important regulator of

  10. Impaired hip muscle strength in patients with femoroacetabular impingement syndrome.

    PubMed

    Kierkegaard, Signe; Mechlenburg, Inger; Lund, Bent; Søballe, Kjeld; Dalgas, Ulrik

    2017-05-25

    Patients with femoroacetabular impingement (FAI) experience hip pain as well as decreased function and lowered quality of life. The aim was to compare maximal isometric and isokinetic muscle strength (MVC) during hip flexion and extension and rate of force development (RFD) during extension between patients with FAI and a matched reference group. Secondary, the aim was to compare patient hips and subgroups defined by gender and age as well as to investigate associations between hip muscle strength and self-reported outcomes. Design Cross-sectional, comparative study Methods Sixty patients (36±9 years, 63% females) and 30 age and gender matched reference persons underwent MVC tests in an isokinetic dynamometer. During hip flexion and extension, patients' affected hip showed a strength deficit of 15-21% (p<0.001) and 10-25% (p<0.03) compared with reference MVC, respectively. The affected hip of the patients was significantly weaker than their contralateral hip. RFD was significantly decreased for both patient hips compared to the reference group (p<0.05). While age had less effect on MVC, female patients were more affected than male patients. Self-reported measures were associated with isometric hip muscle strength. Patients with FAI demonstrate decreased hip flexion and extension strength when compared to (1) reference persons and (2) their contralateral hip. There seems to be a gender specific affection which should be investigated further and addressed when planning training protocols. Furthermore, self-reported measures were associated with isometric muscle strength, which underlines the clinical importance of the reduced muscle strength. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  11. Hypoxia and fatigue-induced modification of function and proteins in intact and skinned murine diaphragm muscle.

    PubMed

    Brotto, M A; Andreatta-van Leyen, S; Nosek, C M; Brotto, L S; Nosek, T M

    2000-09-01

    Fatigue studies of isolated, intact muscles typically utilize solutions saturated with O2. However, under in vivo fatiguing conditions, less oxygen is delivered to the muscles and they actually experience hypoxia. No studies to date have correlated the effects of acute hypoxia on the isometric contractile properties of intact muscles, skinned fibers isolated from the same muscles, and the cellular content of specific muscle proteins. Therefore, we have studied the effects of in vitro acute hypoxia on the fatigability of intact diaphragm muscle strips and on the isometric contractile properties of single Triton-skinned fibers isolated from control and hypoxic diaphragm muscles. We found that hypoxia and fatiguing stimulation per se affect the tetanic force of intact muscle strips without exhibiting any significant deleterious effects on the calcium-activated force of skinned muscle fibers dissected from the intact muscles. In contrast, fatiguing stimulation under hypoxic conditions decreased both the tetanic force of muscle strips and the calcium-activated force of skinned muscle fibers. Gel electrophoresis of muscles subjected to hypoxia and hypoxic-fatigue revealed that there is a significant reduction in three protein bands when compared to control muscles. Protein modification may be the underlying mechanism of muscle fatigue under physiologic conditions.

  12. Associations between force and fatigue in fast-twitch motor units of a cat hindlimb muscle.

    PubMed

    Laouris, Y; Bevan, L; Reinking, R M; Stuart, D G

    2004-01-01

    Associations were quantified between the control force and fatigue-induced force decline in 22 single fast-twitch-fatigable motor units of 5 deeply anesthetized adult cats. The units were subjected to intermittent stimulation at 1 train/s for 360 s. Two stimulation patterns were delivered in a pseudo-random manner. The first was a 500-ms train with constant interpulse intervals. The second pattern had the same number of stimuli, mean stimulus rate, and stimulus duration, but the stimulus pulses were rearranged to increase the force produced by the units in the control (prefatigue) state. The associations among the control peak tetanic force of these units, 3 indices of fatigue, and total cumulative force during fatiguing contractions were dependent, in part, on the stimulation pattern used to produce fatigue. The associations were also dependent, albeit to a lesser extent, on the force measure (peak vs. integrated) and the fatigue index used to quantify fatigue. It is proposed that during high-force fatiguing contractions, neural mechanisms are potentially available to delay and reduce the fatigue of fast-twitch-fatigable units for brief, but functionally relevant, periods. In contrast, the fatigue of slow-twitch fatigue-resistant units seems more likely to be controlled largely, if not exclusively, by metabolic processes within their muscle cells.

  13. Fatigue-related firing of distal muscle nociceptors reduces voluntary activation of proximal muscles of the same limb.

    PubMed

    Kennedy, David S; McNeil, Chris J; Gandevia, Simon C; Taylor, Janet L

    2014-02-15

    With fatiguing exercise, firing of group III/IV muscle afferents reduces voluntary activation and force of the exercised muscles. These afferents can also act across agonist/antagonist pairs, reducing voluntary activation and force in nonfatigued muscles. We hypothesized that maintained firing of group III/IV muscle afferents after a fatiguing adductor pollicis (AP) contraction would decrease voluntary activation and force of AP and ipsilateral elbow flexors. In two experiments (n = 10) we examined voluntary activation of AP and elbow flexors by measuring changes in superimposed twitches evoked by ulnar nerve stimulation and transcranial magnetic stimulation of the motor cortex, respectively. Inflation of a sphygmomanometer cuff after a 2-min AP maximal voluntary contraction (MVC) blocked circulation of the hand for 2 min and maintained firing of group III/IV muscle afferents. After a 2-min AP MVC, maximal AP voluntary activation was lower with than without ischemia (56.2 ± 17.7% vs. 76.3 ± 14.6%; mean ± SD; P < 0.05) as was force (40.3 ± 12.8% vs. 57.1 ± 13.8% peak MVC; P < 0.05). Likewise, after a 2-min AP MVC, elbow flexion voluntary activation was lower with than without ischemia (88.3 ± 7.5% vs. 93.6 ± 3.9%; P < 0.05) as was torque (80.2 ± 4.6% vs. 86.6 ± 1.0% peak MVC; P < 0.05). Pain during ischemia was reported as Moderate to Very Strong. Postfatigue firing of group III/IV muscle afferents from the hand decreased voluntary drive and force of AP. Moreover, this effect decreased voluntary drive and torque of proximal unfatigued muscles, the elbow flexors. Fatigue-sensitive group III/IV muscle nociceptors act to limit voluntary drive not only to fatigued muscles but also to unfatigued muscles within the same limb.

  14. Effects of caffeine on mouse skeletal muscle power output during recovery from fatigue.

    PubMed

    James, Rob S; Wilson, Robbie S; Askew, Graham N

    2004-02-01

    The effects of 10 mM (high) and 70 microM (physiologically relevant) caffeine on force, work output, and power output of isolated mouse extensor digitorum longus (EDL) and soleus muscles were investigated in vitro during recovery from fatigue at 35 degrees C. To monitor muscle performance during recovery from fatigue, we regularly subjected the muscle to a series of cyclical work loops. Force, work, and power output during shortening were significantly higher after treatment with 10 mM caffeine, probably as a result of increased Ca2+ release from the sarcoplasmic reticulum. However, the work required to relengthen the muscle also increased in the presence of 10 mM caffeine. This was due to a slowing of relaxation and an increase in muscle stiffness. The combination of increased work output during shortening and increased work input during lengthening had different effects on the two muscles. Net power output of mouse soleus muscle decreased as a result of 10 mM caffeine exposure, whereas net power output of the EDL muscle showed a transient, significant increase. Treatment with 70 microM caffeine had no significant effect on force, work, or power output of EDL or soleus muscles, suggesting that the plasma concentrations found when caffeine is used to enhance performance in human athletes might not directly affect the contractile performance of fatigued skeletal muscle.

  15. Fatigue and contraction of slow and fast muscles in hypokinetic/hypodynamic rats

    NASA Technical Reports Server (NTRS)

    Fell, R. D.; Gladden, L. B.; Steffen, J. M.; Musacchia, X. J.

    1985-01-01

    The effects of hypokinesia/hypodynamia (H/H) on the fatigability and contractile properties of the rat soleus (S) and gastrocnemius (G) muscles have been investigated experimentally. Whole body suspension for one week was used to induce H/H, and fatigue was brought on by train stimulation for periods of 45 and 16 minutes. Following stimulation, rapid rates of fatigue were observed in the G-muscles of the suspended rats, while minimal fatigue was observed in the S-muscles. The twitch and tetanic contractile properties of the muscles were measured before and after train stimulation. It is found that H/H suspension increased twitch tension in the G-muscles, but did not change any contractile properties in the S-muscles. The peak twitch, train, tetanic tensions and time to peak were unchanged in the S-muscles of the suspended rats. On the basis of the experimental results, it is concluded that 1 wk of muscle atropy induced by H/H significantly increases fatigability in G-muscles, but does not affect the contractile properties of fast-twitch and slow-twitch muscles.

  16. Analysis of Fretting Fatigue Strength of Integral Shroud Blade for Steam Turbine

    NASA Astrophysics Data System (ADS)

    Kaneko, Yasutomo; Tomii, Masayuki; Ohyama, Hiroharu; Kurimura, Takayuki

    To improve the reliability and the thermal efficiency of LP (Low Pressure) end blades of steam turbine, new standard series of LP end blades have been developed. The new LP end blades are characterized by the ISB (Integral Shroud Blade) structure. In the ISB structure, blades are continuously coupled by blade untwist due to centrifugal force when the blades rotate at high speed. One of the probable failure modes of the ISB structure seems to be fretting fatigue, because the ISB utilizes friction damping between adjacent shrouds and stubs. Therefore, in order to design a blade with high reliability, the design procedure for evaluating the fretting fatigue strength was established by the model test and the nonlinear contact analysis. This paper presents the practical design method for predicting the fretting fatigue strength of the ISB structure, and the some applications are explained.

  17. Effect of preload on the fatigue and static strength of composite laminates with defects

    NASA Technical Reports Server (NTRS)

    Porter, T. R.; Smith, G. T.

    1977-01-01

    The effect of a preload cycle on the structural performance of three graphite/epoxy composite laminates was studied. The layups studied were a laminate typical of general purpose structures (L1), a laminate representative of a filament wound tank (L2), and a laminate representative of turboengine fan blades. The effects of three sizes of simulated initial defects were studied. The tests developed static strength data, fatigue to failure data, and residual static data after application of a predetermined number of fatigue cycles. For L1 specimens, there was a slight trend for the static strength to be greater for preloaded specimens. After application of cyclic loading, however, the influence of preloading was insignificant. In L2 and L3 specimens there was no consistent difference in the static or fatigue results between preloaded and nonpreloaded specimens.

  18. Effects of wear-resistant coatings on the fatigue strength of 4340 steel

    SciTech Connect

    Duffy, E.R.

    1998-12-31

    For applications using 4340 steel where hardened surfaces are required in a marine environment, surface coatings are necessary. Coatings that resist corrosion and provide wear resistance generally degrade the fatigue performance of the substrate metal. Shot peening before plating was ineffective in preventing a loss of fatigue life of plated steel bars compared to bare steel test bars which were not shot peened. The maximum residual compressive strength produced by shot peening was measured and was less than the maximum applied tensile stress in fatigue. As-plated electroless nickel has poor sliding wear resistance compared to either electroplated nickel or chromium in sliding wear at a contact stress of 37 Mpa. The tensile strength decreased in proportion to the volume fraction of coating applied to the steel substrate.

  19. Muscle strength and endurance following lowerlimb suspension in man

    NASA Technical Reports Server (NTRS)

    Tesch, Per A.; Berg, Hans E.; Haggmark, Tom; Ohlsen, Hans; Dudley, Gary A.

    1991-01-01

    The effect of lower-limb suspension on the muscle strength and muscle endurance was investigated in six men subjected to four weeks of unilateral unloading of a lower limb (using of a harness attached to a modified shoe), followed by seven weeks of weight-bearing recovery. Results showed a decrease in the cross-sectional area (CSA) of the thigh muscle and in the average peak torque (APT) during three bouts of 30 concentric knee extensions. While the the thigh muscle CSA returned to normal after seven weeks of recovery, the APT recovery was still reduced by 11 percent, suggesting that muscle metabolic function was severely affected by unloading and was not restored by ambulation.

  20. Muscle strength and endurance following lowerlimb suspension in man

    NASA Technical Reports Server (NTRS)

    Tesch, Per A.; Berg, Hans E.; Haggmark, Tom; Ohlsen, Hans; Dudley, Gary A.

    1991-01-01

    The effect of lower-limb suspension on the muscle strength and muscle endurance was investigated in six men subjected to four weeks of unilateral unloading of a lower limb (using of a harness attached to a modified shoe), followed by seven weeks of weight-bearing recovery. Results showed a decrease in the cross-sectional area (CSA) of the thigh muscle and in the average peak torque (APT) during three bouts of 30 concentric knee extensions. While the the thigh muscle CSA returned to normal after seven weeks of recovery, the APT recovery was still reduced by 11 percent, suggesting that muscle metabolic function was severely affected by unloading and was not restored by ambulation.

  1. Effects of Kinesiology Taping on Repositioning Error of the Knee Joint after Quadriceps Muscle Fatigue

    PubMed Central

    Han, Jin Tae; Lee, Jung-hoon

    2014-01-01

    [Purpose] The purpose of this study was to identify the effects of kinesiology taping on repositioning error of the knee joint after quadriceps muscle fatigue. [Subjects] Thirty healthy adults with no orthopaedic or neurological problems participated in this study. [Methods] The repositioning error of the knee joint was measured using a digital goniometer when the subjects extended their dominant-side knee to a random target angle (30°, 45°, or 60°) with their eyes closed, before and after a quadriceps muscle fatigue protocol, and after application of kinesiology tape. [Results] We found that repositioning errors of the dominant-side knee joint increased after quadriceps fatigue compared with no-fatigue conditions. However, kinesiology taping of the quadriceps muscle and patella after quadriceps fatigue significantly decreased repositioning errors of the knee joint. [Conclusion] These results suggest that quadriceps fatigue increases the repositioning error of the knee joint, whereas application of kinesiology tape decreases fatigue-induced joint repositioning error. PMID:25013297

  2. Specific oxidative alterations in vastus lateralis muscle of patients with the diagnosis of chronic fatigue syndrome.

    PubMed

    Fulle, S; Mecocci, P; Fanó, G; Vecchiet, I; Vecchini, A; Racciotti, D; Cherubini, A; Pizzigallo, E; Vecchiet, L; Senin, U; Beal, M F

    2000-12-15

    Chronic fatigue syndrome (CFS) is a poorly understood disease characterized by mental and physical fatigue, most often observed in young white females. Muscle pain at rest, exacerbated by exercise, is a common symptom. Although a specific defect in muscle metabolism has not been clearly defined, yet several studies report altered oxidative metabolism. In this study, we detected oxidative damage to DNA and lipids in muscle specimens of CFS patients as compared to age-matched controls, as well as increased activity of the antioxidant enzymes catalase, glutathione peroxidase, and transferase, and increases in total glutathione plasma levels. From these results we hypothesize that in CFS there is oxidative stress in muscle, which results in an increase in antioxidant defenses. Furthermore, in muscle membranes, fluidity and fatty acid composition are significantly different in specimens from CFS patients as compared to controls and to patients suffering from fibromyalgia. These data support an organic origin of CFS, in which muscle suffers oxidative damage.

  3. Electromyographic fatigue of orbicular oris muscles during exercises in mouth and nasal breathing children.

    PubMed

    Busanello-Stella, Angela Ruviaro; Blanco-Dutra, Ana Paula; Corrêa, Eliane Castilhos Rodrigues; Silva, Ana Maria Toniolo da

    2015-01-01

    To investigate the process of fatigue in orbicularis oris muscles by analyzing the median frequency of electromyographic signal and the referred fatigue time, according to the breathing mode and the facial pattern. The participants were 70 children, aged 6 to 12 years, who matched the established criteria. To be classified as 36 nasal-breathing and 34 mouth-breathing children, they underwent speech-language, otorhinolaryngologic, and cephalometric evaluation. For the electromyographic assessment, the children had to sustain lip dumbbells weighing 40, 60, and 100 g and a lip exerciser, until the feeling of fatigue. Median frequency was analyzed in 5, 10, 15, and 20 seconds of activity. The referred time of the feeling of fatigue was also recorded. Data were analyzed through the analysis of variance--repeated measures (post hoc Tukey's test), Kruskal-Wallis test, and Mann-Whitney U-test. A significant decrease in the median frequency from 5 seconds of activity was observed, independently from the comparison between the groups. On comparison, the muscles did not show significant decrease. The reported time for the feeling of fatigue was shorter for mouth-breathing individuals. This feeling occurred after the significant decrease in the median frequency. There were signals that indicated myoelectric fatigue for the orbicularis oris muscles, in both groups analyzed, from the first 5 seconds of activity. Myoelectric fatigue in the orbicularis oris muscles preceded the reported feeling of fatigue in all groups. The account for fatigue time was influenced by only the breathing pattern, occurring more precociously in mouth-breathing children.

  4. The compensatory interaction between motor unit firing behavior and muscle force during fatigue.

    PubMed

    Contessa, Paola; De Luca, Carlo J; Kline, Joshua C

    2016-10-01

    Throughout the literature, different observations of motor unit firing behavior during muscle fatigue have been reported and explained with varieties of conjectures. The disagreement amongst previous studies has resulted, in part, from the limited number of available motor units and from the misleading practice of grouping motor unit data across different subjects, contractions, and force levels. To establish a more clear understanding of motor unit control during fatigue, we investigated the firing behavior of motor units from the vastus lateralis muscle of individual subjects during a fatigue protocol of repeated voluntary constant force isometric contractions. Surface electromyographic decomposition technology provided the firings of 1,890 motor unit firing trains. These data revealed that to sustain the contraction force as the muscle fatigued, the following occurred: 1) motor unit firing rates increased; 2) new motor units were recruited; and 3) motor unit recruitment thresholds decreased. Although the degree of these adaptations was subject specific, the behavior was consistent in all subjects. When we compared our empirical observations with those obtained from simulation, we found that the fatigue-induced changes in motor unit firing behavior can be explained by increasing excitation to the motoneuron pool that compensates for the fatigue-induced decrease in muscle force twitch reported in empirical studies. Yet, the fundamental motor unit control scheme remains invariant throughout the development of fatigue. These findings indicate that the central nervous system regulates motor unit firing behavior by adjusting the operating point of the excitation to the motoneuron pool to sustain the contraction force as the muscle fatigues. Copyright © 2016 the American Physiological Society.

  5. Age at spinal cord injury determines muscle strength

    PubMed Central

    Thomas, Christine K.; Grumbles, Robert M.

    2014-01-01

    As individuals with spinal cord injury (SCI) age they report noticeable deficits in muscle strength, endurance and functional capacity when performing everyday tasks. These changes begin at ~45 years. Here we present a cross-sectional analysis of paralyzed thenar muscle and motor unit contractile properties in two datasets obtained from different subjects who sustained a cervical SCI at different ages (≤46 years) in relation to data from uninjured age-matched individuals. First, completely paralyzed thenar muscles were weaker when C6 SCI occurred at an older age. Muscles were also significantly weaker if the injury was closer to the thenar motor pools (C6 vs. C4). More muscles were strong (>50% uninjured) in those injured at a younger (≤25 years) vs. young age (>25 years), irrespective of SCI level. There was a reduction in motor unit numbers in all muscles tested. In each C6 SCI, only ~30 units survived vs. 144 units in uninjured subjects. Since intact axons only sprout 4–6 fold, the limits for muscle reinnervation have largely been met in these young individuals. Thus, any further reduction in motor unit numbers with time after these injuries will likely result in chronic denervation, and may explain the late-onset muscle weakness routinely described by people with SCI. In a second dataset, paralyzed thenar motor units were more fatigable than uninjured units. This gap widened with age and will reduce functional reserve. Force declines were not due to electromyographic decrements in either group so the site of failure was beyond excitation of the muscle membrane. Together, these results suggest that age at SCI is an important determinant of long-term muscle strength, and fatigability, both of which influence functional capacity. PMID:24478643

  6. Fatigue strength of yttria-stabilized zirconia polycrystals: Effects of grinding, polishing, glazing, and heat treatment.

    PubMed

    Zucuni, Camila Pauleski; Guilardi, Luís Felipe; Rippe, Marilia Pivetta; Pereira, Gabriel Kalil Rocha; Valandro, Luiz Felipe

    2017-11-01

    This study aimed to evaluate and compare the effect of different surface post-processing treatments (polishing, heat treatment, glazing, polishing + heat treatment and polishing + glazing) on the superficial characteristics (micromorphology and roughness), phase transformation and fatigue strength of a Y-TZP ceramic ground with diamond bur. Discs of Y-TZP ceramic were manufactured (ISO:6872-2015; final dimensions of 15mm in diameter and 1.2 ± 0.2mm in thickness) and randomly allocated according to the surface condition: Ctrl - as-sintered; Gr - ground with coarse diamond bur; Gr+HT - ground and subjected to the heat treatment; Gr+Pol - ground and polished; Gr+Pol+HT - ground, polished and heat treated; Gr+Gl - ground and glazed; Gr+Pol+Gl - ground, polished and glazed. The following analyses were performed: roughness (n = 25), surface topography (n = 2), phase transformation (n = 2) and fatigue strength by staircase method (n = 20). All treatments influenced to some extent the surface characteristics of Y-TZP, being that polishing reduced the surface roughness, the m-phase content and improved the fatigue strength; glazing led to the lowest roughness values (Ra and Rz), although it showed the worst fatigue strength; heat treatment showed limited effect on surface roughness, led to complete reversion of the existing m-phase content to t-phase, without enhancing fatigue performance. Thus, a polishing protocol after clinic adjustment (grinding) of monolithic restorations based on polycrystalline zirconia material is mandatory for surface characteristics and fatigue performance improvements. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Fatigue strength of Co-Cr-Mo alloy clasps prepared by selective laser melting.

    PubMed

    Kajima, Yuka; Takaichi, Atsushi; Nakamoto, Takayuki; Kimura, Takahiro; Yogo, Yoshiaki; Ashida, Maki; Doi, Hisashi; Nomura, Naoyuki; Takahashi, Hidekazu; Hanawa, Takao; Wakabayashi, Noriyuki

    2016-06-01

    We aimed to investigate the fatigue strength of Co-Cr-Mo clasps for removable partial dentures prepared by selective laser melting (SLM). The Co-Cr-Mo alloy specimens for tensile tests (dumbbell specimens) and fatigue tests (clasp specimens) were prepared by SLM with varying angles between the building and longitudinal directions (i.e., 0° (TL0, FL0), 45° (TL45, FL45), and 90° (TL90, FL90)). The clasp specimens were subjected to cyclic deformations of 0.25mm and 0.50mm for 10(6) cycles. The SLM specimens showed no obvious mechanical anisotropy in tensile tests and exhibited significantly higher yield strength and ultimate tensile strength than the cast specimens under all conditions. In contrast, a high degree of anisotropy in fatigue performance associated with the build orientation was found. For specimens under the 0.50mm deflection, FL90 exhibited significantly longer fatigue life (205,418 cycles) than the cast specimens (112,770 cycles). In contrast, the fatigue lives of FL0 (28,484 cycles) and FL45 (43,465 cycles) were significantly shorter. The surface roughnesses of FL0 and FL45 were considerably higher than those of the cast specimens, whereas there were no significant differences between FL90 and the cast specimens. Electron backscatter diffraction (EBSD) analysis indicated the grains of FL0 showed preferential close to <001> orientation of the γ phase along the normal direction to the fracture surface. In contrast, the FL45 and FL90 grains showed no significant preferential orientation. Fatigue strength may therefore be affected by a number of factors, including surface roughness and crystal orientation. The SLM process is a promising candidate for preparing tough removable partial denture frameworks, as long as the appropriate build direction is adopted.

  8. Adiposity, muscle mass, and muscle strength in relation to functional decline in older persons.

    PubMed

    Schaap, Laura A; Koster, Annemarie; Visser, Marjolein

    2013-01-01

    Aging is associated with changes in body composition and muscle strength. This review aimed to determine the relation between different body composition measures and muscle strength measures and functional decline in older men and women. By use of relevant databases (PubMed, Embase, and CINAHL) and keywords in a search from 1976 to April 2012, 50 articles were reviewed that met the inclusion criteria (written in English, a prospective, longitudinal design, involving older persons aged 65 years or more, and at least one of the measures that follow: body mass index (BMI), waist circumference, waist/hip ratio, midarm circumference, fat mass, muscle fat infiltration, muscle mass, or strength as independent variables and a measure of functional decline as outcome measure). Meta-analyses were performed and revealed that BMI ≥30 and low muscle strength were associated with functional decline (pooled odds ratio (OR) = 1.60, 95% confidence interval (CI): 1.43, 1.80, for BMI ≥30 and OR = 1.86, 95% CI: 1.32, 2.64, for muscle strength). Low muscle mass was not significantly associated with functional decline (pooled OR = 1.19, 95% CI: 0.98, 1.45). Future intervention research should focus on positive changes in body composition to prevent onset or worsening of functional decline in old age.

  9. Inverse associations between muscle mass, strength, and the metabolic syndrome.

    PubMed

    Atlantis, Evan; Martin, Sean A; Haren, Matthew T; Taylor, Anne W; Wittert, Gary A

    2009-07-01

    The metabolic syndrome (MetS) is a clustering of individual cardiovascular disease risk factors, which doubles the risk of early mortality. The authors' aimed to determine the prevalence and population attributable risk (PAR%) of the MetS among men according to demographic, physical, and lifestyle risk factors. A cross-sectional study was conducted in 1195 men in the Florey Adelaide Male Ageing Study, a regionally representative cohort of Australian men aged 35 to 81 years conducted in 2002-2005 (response rate, 45.1%). Prevalent MetS was determined according to the Adult Treatment Panel III (ATPIII) and International Diabetes Federation (IDF) classifications; and an extensive list of demographic, physical (including muscle strength, body composition by dual-energy x-ray absorptiometry, sex hormones), and lifestyle factors was accounted for. Prevalence estimates were 37.7% and 41.8% for ATPIII and IDF classifications. Odds ratios for present MetS were determined using multiple-adjusted logistic regression. Odds for present ATPIII MetS decreased (in order of importance) for lower insulin and increased for lower muscle mass, lower strength, and 3+ medical conditions. Odds for present IDF MetS decreased for lower insulin and increased for lower muscle mass, strength, and sex hormone-binding globulin levels; older age; and being married. Significant PAR% due to lowest insulin, muscle mass, and strength quarters were -44%, 27%, and 17% for the ATPIII Met, and -48%, 31%, and 20% for the IDF MetS. A substantial proportion of MetS cases would have been theoretically prevented if prior exposure to low muscle mass and strength were eradicated (PAR% ranged from 14% to 24%). Findings indicate that insulin resistance is a central abnormality in the MetS and that muscle mass and strength are strong protective factors independent of insulin resistance and abdominal fat accumulation. If confirmed prospectively, increases in muscle mass and strength needed to prevent a substantial

  10. Preventive effects of stretching and stabilization exercises on muscle fatigue in mobile phone users

    PubMed Central

    Kim, Hye-Young; Yeun, Young-Ran; Kim, Sung-Joong

    2016-01-01

    [Purpose] The purpose of this study was to investigate the preventive effects of stretching and stabilization exercises on muscle fatigue of the neck erector spine and upper trapezius muscles. [Subjects and Methods] The subjects of this study were 26 healthy university students (14 males and 12 females). Each subject was assigned randomly to each of three study groups in order to prevent order effect. The three groups included in this study were the no-exercise, stretching exercise, and neck stabilization exercise groups. The median electromyographic frequency was used as a gauge of muscle fatigue. [Results] Decreased muscle fatigue was demonstrated by an increase in the median electromyographic frequency values in all the four muscle groups in the comparison between conditions 1 and 3. In particular, statistically significant differences were found between the two conditions in the right upper trapezius muscle group. [Conclusion] These findings suggest that the effect of stretching and stabilization exercises can reduce muscle fatigue in mobile phone users. PMID:27799686

  11. Impact of machining on the flexural fatigue strength of glass and polycrystalline CAD/CAM ceramics.

    PubMed

    Fraga, Sara; Amaral, Marina; Bottino, Marco Antônio; Valandro, Luiz Felipe; Kleverlaan, Cornelis Johannes; May, Liliana Gressler

    2017-08-14

    To assess the effect of machining on the flexural fatigue strength and on the surface roughness of different computer-aided design, computer-aided manufacturing (CAD/CAM) ceramics by comparing machined and polished after machining specimens. Disc-shaped specimens of yttria-stabilized polycrystalline tetragonal zirconia (Y-TZP), leucite-, and lithium disilicate-based glass ceramics were prepared by CAD/CAM machining, and divided into two groups: machining (M) and machining followed by polishing (MP). The surface roughness was measured and the flexural fatigue strength was evaluated by the step-test method (n=20). The initial load and the load increment for each ceramic material were based on a monotonic test (n=5). A maximum of 10,000 cycles was applied in each load step, at 1.4Hz. Weibull probability statistics was used for the analysis of the flexural fatigue strength, and Mann-Whitney test (α=5%) to compare roughness between the M and MP conditions. Machining resulted in lower values of characteristic flexural fatigue strength than machining followed by polishing. The greatest reduction in flexural fatigue strength from MP to M was observed for Y-TZP (40%; M=536.48MPa; MP=894.50MPa), followed by lithium disilicate (33%; M=187.71MPa; MP=278.93MPa) and leucite (29%; M=72.61MPa; MP=102.55MPa). Significantly higher values of roughness (Ra) were observed for M compared to MP (leucite: M=1.59μm and MP=0.08μm; lithium disilicate: M=1.84μm and MP=0.13μm; Y-TZP: M=1.79μm and MP=0.18μm). Machining negatively affected the flexural fatigue strength of CAD/CAM ceramics, indicating that machining of partially or fully sintered ceramics is deleterious to fatigue strength. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  12. 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.

  13. Probabilistic Material Strength Degradation Model for Inconel 718 Components Subjected to High Temperature, High-Cycle and Low-Cycle Mechanical Fatigue, Creep and Thermal Fatigue Effects

    NASA Technical Reports Server (NTRS)

    Bast, Callie C.; Boyce, Lola

    1995-01-01

    The development of methodology for a probabilistic material strength degradation is described. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing predictions of high-cycle mechanical fatigue and high temperature effects with experiments are presented. Results from this limited verification study strongly supported that material degradation can be represented by randomized multifactor interaction models.

  14. Neural Mechanism of Chronic Fatigue Syndrome

    DTIC Science & Technology

    2004-04-01

    Chronic fatigue syndrome, Gulf War Syndrome, functional MRI, 44 electroencephalogram(EEG) Electromyogram( EMG ), brain motor activity, 16. PRICE CODE...analysis. We have developed two software packages for the analysis of electroencephalogram (EEG) and electromyogram ( EMG ) data. We used these software...electromyography ( EMG ); voluntary muscle contraction; muscle fatigue; muscle strength. Siernionow et a]. Page 2 Motor-Related Cortical Potential in Chronic Fatigue

  15. Upper limb muscle fatigue during prolonged Boccia games with underarm throwing technique.

    PubMed

    Fong, Daniel Tik-Pui; Yam, Kit-Yee; Chu, Vikki Wing-Shan; Cheung, Roy Tsz-Hei; Chan, Kai-Ming

    2012-11-01

    This study investigated the acute fatigue pattern in neuromuscular activity after a simulated Boccia game and the effect of fatigue pattern on sport performance. Nine elite Boccia athletes were tested before, during, and after a simulated game. Maximum ball speed was captured with video, and the target hitting rate and rating of perceived exertion (RPE) score were collected and analyzed. Electromyography signals from the upper trapezius, anterior deltoid, posterior deltoid, biceps brachii, triceps brachii, and wrist extensor muscles were collected by surface electrode and were evaluated with mean power frequency (MPF). Only the upper trapezius muscle showed fatigue as demonstrated by a reduction of MPF of 8% (p = 0.027) when comparing the first and last throws in a simulated game. Subjective RPE score increased during the game (118%, p = 0.004), and sports performance in terms of maximum ball speed (-12%, p = 0.004) and target hitting rate (-25%, p = 0.004) also deteriorated. In conclusion, fatigue on the upper trapezius muscle was demonstrated in elite Boccia athletes following a prolonged Boccia game and may have affected Boccia performance. Preventative measures against upper trapezius muscle fatigue and endurance training for synergists of the upper trapezius muscle may be considered in future studies.

  16. Alternating activation is related to fatigue in lumbar muscles during sustained sitting.

    PubMed

    Ringheim, Inge; Indahl, Aage; Roeleveld, Karin

    2014-06-01

    The aim of this study was to investigate the relation between variability in muscle activity and fatigue during a sustained low level contraction in the lumbar muscles. Twenty-five healthy participants (13 men 12 women) performed a 30min sitting task with 5 degrees inclination of the trunk. Surface electromyographic (EMG) signals were recorded bilaterally from the lumbar muscles with 2 high density surface EMG grids of 9×14 electrodes. Median frequency (MDF) decrease, amplitude (RMS) increase and the rating of perceived exertion (RPE) were used as fatigue indices. Alternating activation and spatial and temporal variability were computed and relations with the fatigue indices were explored. During sitting, the mono- and bipolar RMS slightly increased while the MDF remained unchanged indicating no systematic muscle fatigue, although the average RPE increased from 6 to 13 on a scale ranging between 6 and 20. Higher frequency of alternating activation between the left and right side was associated with increased RPE (p=0.03) and decreased MDF (p=0.05). A tendency in the same direction was seen between increased spatial and temporal variation within the grids and increased RPE and decreased MDF. Present findings provide evidence for a relationship between variability in muscle activity and fatigue. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. A Real-Time Fatigue Monitoring and Analysis System for Lower Extremity Muscles with Cycling Movement

    PubMed Central

    Chen, Szi-Wen; Liaw, Jiunn-Woei; Chan, Hsiao-Lung; Chang, Ya-Ju; Ku, Chia-Hao

    2014-01-01

    A real-time muscle fatigue monitoring system was developed to quantitatively detect the muscle fatigue of subjects during cycling movement, where a fatigue progression measure (FPM) was built-in. During the cycling movement, the electromyogram (EMG) signals of the vastus lateralis and gastrocnemius muscles in one leg as well as cycling speed are synchronously measured in a real-time fashion. In addition, the heart rate (HR) and the Borg rating of perceived exertion scale value are recorded per minute. Using the EMG signals, the electrical activity and median frequency (MF) are calculated per cycle. Moreover, the updated FPM, based on the percentage of reduced MF counts during cycling movement, is calculated to measure the onset time and the progressive process of muscle fatigue. To demonstrate the performance of our system, five young healthy subjects were recruited. Each subject was asked to maintain a fixed speed of 60 RPM, as best he/she could, under a constant load during the pedaling. When the speed reached 20 RPM or the HR reached the maximal training HR, the experiment was then terminated immediately. The experimental results show that the proposed system may provide an on-line fatigue monitoring and analysis for the lower extremity muscles during cycling movement. PMID:25014101

  18. Evaluation of localized muscle fatigue using power spectral density analysis of the electromyogram

    NASA Technical Reports Server (NTRS)

    Lafevers, E. V.

    1974-01-01

    Surface electromyograms (EMGs) taken from three upper torso muscles during a push-pull task were analyzed by a power spectral density technique to determine the operational feasibility of the technique for identifying changes in the EMGs resulting from muscular fatigue. The EMGs were taken from four subjects under two conditions (1) in shirtsleeves and (2) in a pressurized space suit. This study confirmed that frequency analysis of dynamic muscle activity is capable of providing reliable data for many industrial applications where fatigue may be of practical interest. The results showed significant effects of the pressurized space suit on the pattern of shirtsleeve fatigue responses of the muscles. The data also revealed (1) reliable differences between muscles in fatigue-induced responses to various locations in the reach envelope at which the subjects were required to perform the push-pull exercise and (2) the differential sensitivity of muscles to the various reach positions in terms of fatigue-related shifts in EMG power.

  19. Muscle fatigue experienced during maximal eccentric exercise is predictive of the plasma creatine kinase (CK) response.

    PubMed

    Hody, S; Rogister, B; Leprince, P; Wang, F; Croisier, J-L

    2013-08-01

    Unaccustomed eccentric exercise may cause skeletal muscle damage with an increase in plasma creatine kinase (CK) activity. Although the wide variability among individuals in CK response to standardized lengthening contractions has been well described, the reasons underlying this phenomenon have not yet been understood. Therefore, this study investigated a possible correlation of the changes in muscle damage indirect markers after an eccentric exercise with the decline in muscle performance during the exercise. Twenty-seven healthy untrained male subjects performed three sets of 30 maximal isokinetic eccentric contractions of the knee extensors. The muscular work was recorded using an isokinetic dynamometer to assess muscle fatigue by means of various fatigue indices. Plasma CK activity, muscle soreness, and stiffness were measured before (pre) and one day after (post) exercise. The eccentric exercise bout induced significant changes of the three muscle damage indirect markers. Large inter-subject variability was observed for all criteria measured. More interestingly, the log (CK(post) /CK(pre)) and muscle stiffness appeared to be closely correlated with the relative work decrease (r = 0.84, r(2)  = 0.70 and r = 0.75, r(2)  = 0.56, respectively). This is the first study to propose that the muscle fatigue profile during maximal eccentric protocol could predict the magnitude of the symptoms associated with muscle damage in humans. © 2011 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  20. Effect of selective fatiguing of the shank muscles on single-leg-standing sway.

    PubMed

    Suponitsky, Y; Verbitsky, O; Peled, E; Mizrahi, J

    2008-08-01

    Control of standing requires the continuous activity of the leg muscles. In single leg standing the system is less redundant and muscular activity is more intensive. The objective of this study was to examine the effect of force imbalance of the shank muscles, evoked by their selective fatiguing, on postural control in single-leg standing. Five healthy subjects performed two single-leg standing trials, lasting as long as the subject could maintain steady balance, and separated by a 240s quasi-isotonic sustained effort to induce fatigue of the Tibialis Anterior and Peroneus muscles. The following were on-line monitored: sway-related parameters, e.g., ground reaction force and center of pressure in the standing trials; and electromyogram of the Tibialis Anterior, Peroneus and Gastrocnemius muscles in all experiments. Simple and multiple linear regressions served to study the fatigue effects on the relationship between muscle activity and postural sway. The results indicate that the evoked muscle imbalance leads to (a) increased postural sway; (b) increased correlation between muscle activity, and sway-related parameters. Thus, with the reduction of the level of redundancy the system becomes more synchronized. These results have potential relevance for cases of muscle impairment, in which electrical stimulation is required to augment muscle activity.

  1. Acute effects of blood flow restriction on muscle activity and endurance during fatiguing dynamic knee extensions at low load.

    PubMed

    Wernbom, Mathias; Järrebring, Rickard; Andreasson, Mikael A; Augustsson, Jesper

    2009-11-01

    The purpose of this study was to investigate muscle activity and endurance during fatiguing low-intensity dynamic knee extension exercise with and without blood flow restriction. Eleven healthy subjects with strength training experience performed 3 sets of unilateral knee extensions with no relaxation between repetitions to concentric torque failure at 30% of the 1 repetition maximum. One leg was randomized to exercise with cuff occlusion and the other leg to exercise without occlusion. The muscle activity in the quadriceps was recorded with electromyography (EMG). Ratings of perceived exertion (RPE) and acute pain were collected immediately, and delayed onset muscle soreness (DOMS) was rated before and at 24, 48, and 72 hours after exercise. The results demonstrated high EMG levels in both experimental conditions, but there were no significant differences regarding maximal muscle activity, except for a higher EMG in the eccentric phase in set 3 for the nonoccluded condition (p = 0.005). Significantly more repetitions were performed with the nonoccluded leg in every set (p < 0.05). The RPE and acute pain ratings were similar, but DOMS was higher in the nonoccluded leg (p < 0.05). We conclude that blood flow restriction during low-intensity dynamic knee extension decreases the endurance but does not increase the maximum muscle activity compared with training without restriction when both regimes are performed to failure. The high levels of muscle activity suggest that performing low-load dynamic knee extensions in a no-relaxation manner may be a useful method in knee rehabilitation settings when large forces are contraindicated. However, similarly to fatiguing blood flow restricted exercise, this method is associated with ischemic muscle pain, and thus its applications may be limited to highly motivated individuals.

  2. Diagnostic methods to assess inspiratory and expiratory muscle strength*

    PubMed Central

    Caruso, Pedro; de Albuquerque, André Luis Pereira; Santana, Pauliane Vieira; Cardenas, Leticia Zumpano; Ferreira, Jeferson George; Prina, Elena; Trevizan, Patrícia Fernandes; Pereira, Mayra Caleffi; Iamonti, Vinicius; Pletsch, Renata; Macchione, Marcelo Ceneviva; Carvalho, Carlos Roberto Ribeiro

    2015-01-01

    Impairment of (inspiratory and expiratory) respiratory muscles is a common clinical finding, not only in patients with neuromuscular disease but also in patients with primary disease of the lung parenchyma or airways. Although such impairment is common, its recognition is usually delayed because its signs and symptoms are nonspecific and late. This delayed recognition, or even the lack thereof, occurs because the diagnostic tests used in the assessment of respiratory muscle strength are not widely known and available. There are various methods of assessing respiratory muscle strength during the inspiratory and expiratory phases. These methods are divided into two categories: volitional tests (which require patient understanding and cooperation); and non-volitional tests. Volitional tests, such as those that measure maximal inspiratory and expiratory pressures, are the most commonly used because they are readily available. Non-volitional tests depend on magnetic stimulation of the phrenic nerve accompanied by the measurement of inspiratory mouth pressure, inspiratory esophageal pressure, or inspiratory transdiaphragmatic pressure. Another method that has come to be widely used is ultrasound imaging of the diaphragm. We believe that pulmonologists involved in the care of patients with respiratory diseases should be familiar with the tests used in order to assess respiratory muscle function.Therefore, the aim of the present article is to describe the advantages, disadvantages, procedures, and clinical applicability of the main tests used in the assessment of respiratory muscle strength. PMID:25972965

  3. Diagnostic methods to assess inspiratory and expiratory muscle strength.

    PubMed

    Caruso, Pedro; Albuquerque, André Luis Pereira de; Santana, Pauliane Vieira; Cardenas, Leticia Zumpano; Ferreira, Jeferson George; Prina, Elena; Trevizan, Patrícia Fernandes; Pereira, Mayra Caleffi; Iamonti, Vinicius; Pletsch, Renata; Macchione, Marcelo Ceneviva; Carvalho, Carlos Roberto Ribeiro

    2015-01-01

    Impairment of (inspiratory and expiratory) respiratory muscles is a common clinical finding, not only in patients with neuromuscular disease but also in patients with primary disease of the lung parenchyma or airways. Although such impairment is common, its recognition is usually delayed because its signs and symptoms are nonspecific and late. This delayed recognition, or even the lack thereof, occurs because the diagnostic tests used in the assessment of respiratory muscle strength are not widely known and available. There are various methods of assessing respiratory muscle strength during the inspiratory and expiratory phases. These methods are divided into two categories: volitional tests (which require patient understanding and cooperation); and non-volitional tests. Volitional tests, such as those that measure maximal inspiratory and expiratory pressures, are the most commonly used because they are readily available. Non-volitional tests depend on magnetic stimulation of the phrenic nerve accompanied by the measurement of inspiratory mouth pressure, inspiratory esophageal pressure, or inspiratory transdiaphragmatic pressure. Another method that has come to be widely used is ultrasound imaging of the diaphragm. We believe that pulmonologists involved in the care of patients with respiratory diseases should be familiar with the tests used in order to assess respiratory muscle function.Therefore, the aim of the present article is to describe the advantages, disadvantages, procedures, and clinical applicability of the main tests used in the assessment of respiratory muscle strength.

  4. Assessement of quadriceps strength, endurance and fatigue in FSHD and CMT: benefits and limits of femoral nerve magnetic stimulation.

    PubMed

    Bachasson, D; Temesi, J; Bankole, C; Lagrange, E; Boutte, C; Millet, G Y; Verges, S; Levy, P; Feasson, L; Wuyam, B

    2014-02-01

    To (i) evaluate the feasibility and the reliability of a test assessing quadriceps strength, endurance and fatigue in patients with fascioscapulohumeral dystrophy (FSHD) and Charcot-Marie-Tooth disease (CMT), (ii) compare quadriceps function between patients and healthy controls. Controls performed the test once and patients twice on two separate visits. It involved progressive sets of 10 isometric contractions each followed by neuromuscular assessments with FNMS. Volitional assessment of muscle strength, endurance and fatigue appeared to be reliable in FSHD and CMT patients. Supramaximal FNMS was achieved in ∼70% of FSHD patients and in no CMT patients. In FSHD patients, Femoral nerve magnetic stimulation (FNMS) provided reliable assessment of central (typical error as a coefficient of variation (CVTE)<8% for voluntary activation) and peripheral (CVTE<10% and intraclass coefficient correlation >0.85 for evoked responses) function. Patients and controls had similar reductions in evoked quadriceps responses, voluntary activation and similar endurance. This test provides reliable evaluation but FNMS exhibits limitations due to insufficient stimulation intensity particularly in neurogenic conditions. It showed similar central and peripheral quadriceps fatigability in patients and controls. This test may be a valuable tool for patient follow-up although further development of magnetic stimulation devices is needed to extend its applicability. Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  5. Fatigue

    MedlinePlus

    ... to help you find out what's causing your fatigue and recommend ways to relieve it. Fatigue itself is not a disease. Medical problems, treatments, and personal habits can add to fatigue. These include Taking certain medicines, such as antidepressants, ...

  6. Increasing the fatigue limit of a high-strength bearing steel by a deep cryogenic treatment

    NASA Astrophysics Data System (ADS)

    Kerscher, E.; Lang, K.-H.

    2010-07-01

    High-strength steels typically fail from inclusions. Therefore, to increase the fatigue limit of high-strength steels it is necessary to modify the inclusions and/or the surrounding matrix. The goal must be a higher threshold for crack initiation and/or crack propagation. One possibility to reach this goal seems to be a deep cryogenic treatment which is reported to completely transform the retained austenite as well as to facilitate the formation of fine carbides. Therefore, specimens were annealed before or after deep cryogenic treatment, which was carried out with different cooling and heating rates as well as different soaking times at -196° C. Hardness and retained austenite measurements and fatigue experiments were used to evaluate the different sequences of treatments mentioned above. The fatigue limit increases only after some of the sequences. The results show that the soaking times are not relevant for the fatigue limit but it is very important to temper the specimens before the deep cryogenic treatment. Also, repeated deep cryogenic treatments had a positive influence on the fatigue limit.

  7. Selective effects of arm proximal and distal muscles fatigue on force coordination in manipulation tasks.

    PubMed

    Emge, Nicholas; Uygur, Mehmet; Radivoj, Mandic; Kaminski, Thomas W; Royer, Todd; Jaric, Slobodan

    2014-01-01

    Effects of muscle fatigue on force coordination and task performance of various manipulation tasks are explored. Grip force (GF; normal force component acting at the digits-object contact area) and load force (LF; tangential component that lifts and holds objects) were recorded prior to and after fatiguing the distal (DAM; i.e., GF producing) and proximal arm muscles (PAM; LF producing). Results reveal a deterioration of GF scaling (i.e., averaged GF-LF ratio), GF-LF coupling (their correlation), and task performance (ability to exert a prescribed LF pattern) associated with DAM, but not PAM fatigue. Deteriorated force coordination clearly increases the likelihood of dropping an object; however, the observed selective effects of DAM and PAM fatigue represent a novel finding deserving of further research.

  8. Prior Heat Stress Effects Fatigue Recovery of the Elbow Flexor Muscles

    PubMed Central

    Iguchi, Masaki; Shields, Richard K.

    2011-01-01

    Introduction Long-lasting alterations in hormones, neurotransmitters and stress proteins after hyperthermia may be responsible for the impairment in motor performance during muscle fatigue. Methods Subjects (n = 25) performed a maximal intermittent fatigue task of elbow flexion after sitting in either 73 or 26 deg C to examine the effects of prior heat stress on fatigue mechanisms. Results The heat stress increased the tympanic and rectal temperatures by 2.3 and 0.82 deg C, respectively, but there was full recovery prior to the fatigue task. While prior heat stress had no effects on fatigue-related changes in volitional torque, EMG activity, torque relaxation rate, MEP size and SP duration, prior heat stress acutely increased the pre-fatigue relaxation rate and chronically prevented long-duration fatigue (p < 0.05). Discussion These findings indicate that prior passive heat stress alone does not alter voluntary activation during fatigue, but prior heat stress and exercise produce longer-term protection against long-duration fatigue. PMID:21674526

  9. Prior heat stress effects fatigue recovery of the elbow flexor muscles.

    PubMed

    Iguchi, Masaki; Shields, Richard K

    2011-07-01

    Long-lasting alterations in hormones, neurotransmitters, and stress proteins after hyperthermia may be responsible for the impairment in motor performance during muscle fatigue. Subjects (n = 25) performed a maximal intermittent fatigue task of elbow flexion after sitting in either 73° or 26°C to examine the effects of prior heat stress on fatigue mechanisms. The heat stress increased the tympanic and rectal temperatures by 2.3° and 0.82°C, respectively, but there was full recovery prior to the fatigue task. Although prior heat stress had no effects on fatigue-related changes in volitional torque, electromyographic (EMG) activity, torque relaxation rate, motor evoked potential (MEP) size, and silent period (SP) duration, prior heat stress acutely increased the pre-fatigue relaxation rate and chronically prevented long-duration fatigue (P < 0.05). These findings indicate that prior passive heat stress alone does not alter voluntary activation during fatigue, but prior heat stress and exercise produce longer-term protection against long-duration fatigue. Copyright © 2011 Wiley Periodicals, Inc.

  10. Myotonometry as a Surrogate Measure of Muscle Strength

    NASA Technical Reports Server (NTRS)

    Ang, B. S.; Feeback, D. L.; Leonard, C. T.; Sykes, J.; Kruger, E.; Clarke, M. S. F.

    2007-01-01

    Space flight-induced muscle atrophy/neuromuscular degradation and the consequent decrements in crew-member performance are of increasing concern as mission duration lengthens, and planetary exploration after extended space flight is planned. Pre- to post-flight strength measures have demonstrated that specific countermeasures, such as resistive exercise, are effective at countering microgravity-induced muscle atrophy and preventing decrements in muscle strength. However, in-flight assessment/monitoring of exercise countermeasure effectiveness will be essential during exploration class missions due to their duration. The ability to modify an exercise countermeasure prescription based on such real-time information will allow each individual crew member to perform the optimal amount and type of exercise countermeasure to maintain performance. In addition, such measures can be used to determine if a crew member is physically capable of performing a particular mission-related task during exploration class missions. The challenges faced in acquiring such data are those common to all space operations, namely the requirement for light-weight, low power, mechanically reliable technologies that make valid measurements in microgravity, in this case of muscle strength/neuromuscular function. Here we describe a simple, light-weight, low power, non-invasive device, known as the Myotonometer, that measures tissue stiffness as an indirect measure of muscle contractile state and muscle force production. Repeat myotonometer measurements made at the same location on the surface of the rectis femoris muscle (as determined using a 3D locator device, SEM plus or minus 0.34 mm) were shown to be reproducible over time at both maximal voluntary contraction (MVC) and at rest in a total of 17 sedentary subjects assessed three times over a period of seven days. In addition, graded voluntary isometric force production (i.e. 20%, 40%, 60%, 80% & 100% of MVC) during knee extension was shown to

  11. Myotonometry as a Surrogate Measure of Muscle Strength

    NASA Technical Reports Server (NTRS)

    Ang, B. S.; Feeback, D. L.; Leonard, C. T.; Sykes, J.; Kruger, E.; Clarke, M. S. F.

    2007-01-01

    Space flight-induced muscle atrophy/neuromuscular degradation and the consequent decrements in crew-member performance are of increasing concern as mission duration lengthens, and planetary exploration after extended space flight is planned. Pre- to post-flight strength measures have demonstrated that specific countermeasures, such as resistive exercise, are effective at countering microgravity-induced muscle atrophy and preventing decrements in muscle strength. However, in-flight assessment/monitoring of exercise countermeasure effectiveness will be essential during exploration class missions due to their duration. The ability to modify an exercise countermeasure prescription based on such real-time information will allow each individual crew member to perform the optimal amount and type of exercise countermeasure to maintain performance. In addition, such measures can be used to determine if a crew member is physically capable of performing a particular mission-related task during exploration class missions. The challenges faced in acquiring such data are those common to all space operations, namely the requirement for light-weight, low power, mechanically reliable technologies that make valid measurements in microgravity, in this case of muscle strength/neuromuscular function. Here we describe a simple, light-weight, low power, non-invasive device, known as the Myotonometer, that measures tissue stiffness as an indirect measure of muscle contractile state and muscle force production. Repeat myotonometer measurements made at the same location on the surface of the rectis femoris muscle (as determined using a 3D locator device, SEM plus or minus 0.34 mm) were shown to be reproducible over time at both maximal voluntary contraction (MVC) and at rest in a total of 17 sedentary subjects assessed three times over a period of seven days. In addition, graded voluntary isometric force production (i.e. 20%, 40%, 60%, 80% & 100% of MVC) during knee extension was shown to

  12. Endurance and fatigue characteristics in the neck muscles during sub-maximal isometric test in patients with cervical radiculopathy.

    PubMed

    Halvorsen, Marie; Abbott, Allan; Peolsson, Anneli; Dedering, Åsa

    2014-03-01

    The aim of the study was to compare myoelectric manifestation in neck muscle endurance and fatigue characteristics during sub-maximal isometric endurance test in patients with cervical radiculopathy and asymptomatic subjects. An additional aim was to explore associations between primary neck muscle endurance, myoelectric fatigability, and self-rated levels of fatigue, pain and subjective health measurements in patients with cervical radiculopathy. Muscle fatigue in the ventral and dorsal neck muscles was assessed in patients with cervical radiculopathy and in an asymptomatic group during an isometric neck muscle endurance test in prone and supine. 46 patients and 34 asymptomatic subjects participated. Surface electromyography signals were recorded from the sternocleidomastoid, cervical paraspinal muscles and upper and middle trapezius bilaterally during the endurance test. Subjective health measurements were assessed with questionnaires. The results showed altered neck muscle endurance in several of the muscles investigated with greater negative median frequency slope, greater variability, side imbalance, lower endurance time and higher experience of fatigue among the cervical radiculopathy patients compared with healthy subjects. Endurance times were significantly lower in both prone and in supine positions between the patients compared to asymptomatic subjects. During the neck muscle endurance test, fatigues in the upper trapezius muscles during the prone test and in the sternocleidomastoid muscles during the supine test were of more importance than self-perceived pain, fatigue, disability and kinesiophobia in predicting neck muscle endurance (NME). NME testing in the primary neck muscles seems to be an important factor to take into consideration in rehabilitation.

  13. Hamstring Fatigue and Muscle Activation Changes During Six Sets of Nordic Hamstring Exercise in Amateur Soccer Players.

    PubMed

    Marshall, Paul W M; Lovell, Ric; Knox, Michael F; Brennan, Scott L; Siegler, Jason C

    2015-11-01

    The Nordic hamstring exercise (NHE) is a bodyweight movement commonly prescribed to increase eccentric hamstring strength and reduce the incidence of strain injury in sport. This study examined hamstring fatigue and muscle activation responses throughout 6 sets of 5 repetitions of the NHE. Ten amateur-level soccer players performed a single session of 6 sets of 5 repetitions of NHE. Maximal eccentric and concentric torque output (in newton meters) was measured after every set. Hamstrings electromyograms (EMG) were measured during all maximal contractions and exercise repetitions. Hamstring maximal eccentric torque was reduced throughout the range of motion after only a single set of NHE between 7.9 and 17.1% (p ≤ 0.05), with further reductions in subsequent sets. Similarly, maximal concentric torque reductions between 7.8 and 17.2% were observed throughout the range of motion after 1 set of NHE (p ≤ 0.05). During the descent phase of the NHE repetitions, hamstring muscle activity progressively increased as the number of sets performed increased. These increases were observed in the first half of the range of motion. During the ascent phase, biceps femoris muscle activity but not medial hamstrings was reduced from the start of exercise during latter sets of repetitions. These data provide unique insight into the extent of fatigue induced from a bodyweight only exercise after a single set of 5 repetitions. Strength and conditioning coaches need to be aware of the speed and extent of fatigue induced from NHE, particularly in practical settings in which this exercise is now prescribed before sport-specific training sessions (i.e., the FIFA-11 before soccer training).

  14. Levator plate upward lift and levator muscle strength

    PubMed Central

    Rostaminia, Ghazaleh; Peck, Jennifer; Quiroz, Lieschen; Shobeiri, S. Abbas

    2016-01-01

    Objective The aim of study was to compare digital palpation with the levator plate lift measured by endovaginal and transperineal dynamic ultrasound. Methods Dynamic transperineal and endovaginal ultrasound were performed as part of multicompartmental pelvic floor functional assessment. Patients were instructed to perform Kegels while a probe captured the video clip of the levator plate movement at rest and during contraction in 2D mid-sagittal posterior view. We measured the distance between the levator plate and the probe on endovaginal ultrasound as well as the distance between the levator plate and the gothic arch of the pubis in transperineal ultrasound. The change in diameter (lift) and a levator plate lift ratio (lift / rest) x 100) were calculated. Pelvic floor muscle strength was assessed by digital palpation and divided into functional and non-functional groups using the Modified Oxford Scale (MOS). Mean differences in levator plate upward lifts were compared by MOS score using student t-tests and analysis of variance (ANOVA). Results 74 women were available for analysis. The mean age was 55 (SD±11.9). When measured by vaginal dynamic ultrasound, mean values of the lift and lift/rest ratio increased with increasing MOS score (ANOVA p=0.09 and p=0.04, respectively). When MOS scores were categorized to represent non-functional (MOS 0-1) and functional (MOS 2-5) muscle strength groups, the mean values of the lift (3.2 mm vs. 4.6 mm, p=0.03) and lift/rest ratio (13% vs 20%, p=0.01) were significantly higher in women with functional muscle strength. All patients with ≥ 30% lift detected by vaginal ultrasound had functional muscle strength. Conclusions Greater levator plate lift ratio detected by dynamic endovaginal ultrasound was associated with higher muscle strength as determined by MOS. This novel measurement can be incorporated into ultrasound evaluation of the levator ani function. PMID:26333568

  15. The effect of fatigued internal rotator and external rotator muscles of the shoulder on the shoulder position sense.

    PubMed

    Iida, Naoya; Kaneko, Fuminari; Aoki, Nobuhiro; Shibata, Eriko

    2014-02-01

    The purpose of this study was to investigate which muscle group, the agonist or antagonist, contributes most to the shoulder position sense (SPS). The SPS was tested under 2 conditions: fatigued shoulder internal rotator (IR) muscles (pectoralis major and latissimus dorsi) and fatigued external rotator (ER) muscles (infraspinatus). In each condition, the SPS was measured before and after a fatiguing task involving the IR or ER muscles by repeating shoulder joint rotation. SPS was measured using a method in which subjects reproduced a memorized shoulder joint rotation angle. The position error values in all conditions (fatigued IR and ER muscles) and measurement periods (before- and after-fatigue task) were compared using 2-way analysis of variance with repeated measures (IR/ER×before/after). Position error increased significantly after both fatigue tasks (before- vs. after-fatigue: IR muscle, 2.68° vs. 4.19°; ER muscle, 2.32° vs. 4.05°). In other words, SPS accuracy decreased when either the agonist or antagonist muscle was fatigued. This finding indicated that SPS may be affected by an integrated information of the afferent signals in the agonist and antagonist muscles.

  16. Modeling the Tensile Strength of Carbon Fiber - Reinforced Ceramic - Matrix Composites Under Multiple Fatigue Loading

    NASA Astrophysics Data System (ADS)

    Li, Longbiao

    2016-06-01

    An analytical method has been developed to investigate the effect of interface wear on the tensile strength of carbon fiber - reinforced ceramic - matrix composites (CMCs) under multiple fatigue loading. The Budiansky - Hutchinson - Evans shear - lag model was used to describe the micro stress field of the damaged composite considering fibers failure and the difference existed in the new and original interface debonded region. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. The interface shear stress degradation model and fibers strength degradation model have been adopted to analyze the interface wear effect on the tensile strength of the composite subjected to multiple fatigue loading. Under tensile loading, the fibers failure probabilities were determined by combining the interface wear model and fibers failure model based on the assumption that the fiber strength is subjected to two - parameter Weibull distribution and the loads carried by broken and intact fibers satisfy the Global Load Sharing criterion. The composite can no longer support the applied load when the total loads supported by broken and intact fibers approach its maximum value. The conditions of a single matrix crack and matrix multicrackings for tensile strength corresponding to multiple fatigue peak stress levels and different cycle number have been analyzed.

  17. DEGRADATION IN THE FATIGUE STRENGTH OF DENTIN BY DIAMOND BUR PREPARATIONS: IMPORTANCE OF CUTTING DIRECTION

    PubMed Central

    Majd, B.; Majd, H.; Porter, J.A.; Romberg, E.; Arola, D.

    2014-01-01

    The objectives of this investigation were to evaluate the degradation in fatigue strength of dentin by diamond bur preparations and to identify the importance of cutting direction. Three groups of coronal dentin specimens were prepared from unrestored 3rd molars, including a flaw free “control”, and two groups that received a diamond bur cutting treatment performed parallel or perpendicular to the specimen length. The specimens were subjected to static or cyclic flexural loading to failure and the results were compared with data for carbide bur cutting. Under static loading diamond bur cutting resulted in significantly flexure lower strength (p≤0.05) than the control for both cutting directions (from 154 MPa to approx. 124 MPa). However, there was no significant difference in the strength between the control and carbide bur treated specimens. Similarly, the fatigue strength of the diamond bur treated specimens was significantly lower (p≤0.0001) than that of the control for both cutting directions. Cutting in the perpendicular direction resulted in nearly 60% reduction to the endurance limit (from 44 MPa to 19 MPa). Based on the results, diamond bur cutting of cavity preparations causes a reduction in the fatigue strength of dentin, regardless of the cutting direction. To maintain the durability of dentin, cavity preparations introduced using diamond burs must be performed with appropriate cutting direction and followed by a finishing pass. PMID:25611951

  18. Degradation in the fatigue strength of dentin by diamond bur preparations: Importance of cutting direction.

    PubMed

    Majd, B; Majd, H; Porter, J A; Romberg, E; Arola, D

    2016-01-01

    The objectives of this investigation were to evaluate the degradation in fatigue strength of dentin by diamond bur preparations and to identify the importance of cutting direction. Three groups of coronal dentin specimens were prepared from unrestored third molars, including a flaw free "control," and two groups that received a diamond bur cutting treatment performed parallel or perpendicular to the specimen length. The specimens were subjected to static or cyclic flexural loading to failure and the results were compared with data for carbide bur cutting. Under static loading diamond bur cutting resulted in significantly lower flexure strength (p ≤ 0.05) than the control for both cutting directions (from 154 to ∼124 MPa). However, there was no significant difference in the strength between the control and carbide bur treated specimens. Similarly, the fatigue strength of the diamond bur treated specimens was significantly lower (p ≤ 0.0001) than that of the control for both cutting directions. Cutting in the perpendicular direction resulted in nearly 60% reduction to the endurance limit (from 44 to 19 MPa). Based on the results, diamond bur cutting of cavity preparations causes a reduction in the fatigue strength of dentin, regardless of the cutting direction. To maintain the durability of dentin, cavity preparations introduced using diamond burs must be performed with appropriate cutting direction and followed by a finishing pass.

  19. Effect of notch location on fatigue crack growth behavior of strength-mismatched high-strength low-alloy steel weldments

    NASA Astrophysics Data System (ADS)

    Ravi, S.; Balasubramanian, V.; Nasser, S. Nemat

    2004-12-01

    Welding of high-strength low-alloy (HSLA) steels involves the use of low-strength, equal-strength, and high-strength filler materials (electrodes) compared with the parent material, depending on the application of the welded structures and the availability of filler material. In the present investigation, the fatigue crack growth behavior of weld metal (WM) and the heat-affected zone (HAZ) of undermatched (UM), equally matched (EM), and overmatched (OM) joints has been studied. The base material used in this investigation is HSLA-80 steel of weldable grade. Shielded metal arc welding (SMAW) has been used to fabricate the butt joints. A center-cracked tension (CCT) specimen has been used to evaluate the fatigue crack growth behavior of welded joints, utilizing a servo-hydraulic-controlled fatigue-testing machine at constant amplitude loading (R=0). The effect of notch location on the fatigue crack growth behavior of strength mismatched HSLA steel weldments also has been analyzed.

  20. Central fatigue contributes to the greater reductions in explosive than maximal strength with high-intensity fatigue.

    PubMed

    Buckthorpe, Matthew; Pain, Matthew T G; Folland, Jonathan P

    2014-07-01

    The study aimed to assess the influence of fatigue induced by repeated high-force explosive contractions on explosive and maximal isometric strength of the human knee extensors and to examine the neural and contractile mechanisms for the expected decrement. Eleven healthy untrained males completed 10 sets of voluntary maximal explosive contractions (five times 3 s, interspersed with 2 s rest). Sets were separated by 5 s, during which supramaximal twitch and octet contractions [eight pulses at 300 Hz that elicit the contractile peak rate of force development (pRFD)] were evoked. Explosive force, at specific time points, and pRFD were assessed for voluntary and evoked efforts, expressed in absolute terms and normalized to maximal/peak force. Maximal voluntary contraction force (MVCF) and peak evoked forces were also determined. Surface EMG amplitude was measured from three superficial agonists and normalized to maximal compound action potential area. By set 10, explosive force (47-52%, P < 0.001) and MVCF (42%, P < 0.001) had declined markedly. Explosive force declined more rapidly than MVCF, with lower normalized explosive force at 50 ms (29%, P = 0.038) that resulted in reduced normalized explosive force from 0 to 150 ms (11-29%, P ≤ 0.038). Neural efficacy declined by 34%, whilst there was a 15-28% reduction in quadriceps EMG amplitude during voluntary efforts (all P ≤ 0.03). There was demonstrable contractile fatigue (pRFD: octet, 27%; twitch, 66%; both P < 0.001). Fatigue reduced normalized pRFD for the twitch (21%, P = 0.001) but not the octet (P = 0.803). Fatigue exerted a more rapid and pronounced effect on explosive force than on MVCF, particularly during the initial 50 ms of contraction, which may explain the greater incidence of injuries associated with fatigue. Both neural and contractile fatigue mechanisms appeared to contribute to impaired explosive voluntary performance.

  1. Strength, Fracture Toughness, Fatigue, and Standardization Issues of Free-standing Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Zhu, Dong-Ming; Miller, Robert A.

    2003-01-01

    Strength, fracture toughness and fatigue behavior of free-standing thick thermal barrier coatings of plasma-sprayed ZrO2-8wt % Y2O3 were determined at ambient and elevated temperatures in an attempt to establish a database for design. Strength, in conjunction with deformation (stress-strain behavior), was evaluated in tension (uniaxial and trans-thickness), compression, and uniaxial and biaxial flexure; fracture toughness was determined in various load conditions including mode I, mode II, and mixed modes I and II; fatigue or slow crack growth behavior was estimated in cyclic tension and dynamic flexure loading. Effect of sintering was quantified through approaches using strength, fracture toughness, and modulus (constitutive relations) measurements. Standardization issues on test methodology also was presented with a special regard to material's unique constitutive relations.

  2. High-frequency fatigue of skeletal muscle: role of extracellular Ca2+

    PubMed Central

    Germinario, Elena; Esposito, Alessandra; Midrio, Menotti; Peron, Samantha; Palade, Philip T.; Betto, Romeo

    2010-01-01

    The present study evaluated whether Ca2+ entry operates during fatigue of skeletal muscle. The involvement of different skeletal muscle membrane calcium channels and of the Na+/Ca2+ exchanger (NCX) has been examined. The decline of force was analysed in vitro in mouse soleus and EDL muscles submitted to 60 and 110 Hz continuous stimulation, respectively. Stimulation with this high-frequency fatigue (HFF) protocol, in Ca2+-free conditions, caused in soleus muscle a dramatic increase of fatigue, while in the presence of high Ca2+ fatigue was reduced. In EDL muscle, HFF was not affected by external Ca2+ levels either way, suggesting that external Ca2+ plays a general protective role only in soleus. Calciseptine, a specific antagonist of the cardiac isoform (α1C) of the dihydropyridine receptor, gadolinium, a blocker of both stretch-activated and store-operated Ca2+ channels, as well as inhibitors of P2X receptors did not affect the development of HFF. Conversely, the Ca2+ ionophore A23187 increased the protective action of extracellular Ca2+. KB-R7943, a selective inhibitor of the reverse mode of NCX, produced an effect similar to that of Ca2+-free solution. These results indicate that a transmembrane Ca2+ influx, mainly through NCX, may play a protective role during HFF development in soleus muscle. PMID:18560877

  3. Computational simulation of probabilistic lifetime strength for aerospace materials subjected to high temperature, mechanical fatigue, creep, and thermal fatigue

    NASA Technical Reports Server (NTRS)

    Boyce, Lola; Bast, Callie C.; Trimble, Greg A.

    1992-01-01

    The results of a fourth year effort of a research program conducted for NASA-LeRC by The University of Texas at San Antonio (UTSA) are presented. The research included on-going development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subjected to a number of effects or primitive variables. These primitive variables may include high temperature, fatigue, or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation was randomized and is included in the computer program, PROMISC. Also included in the research is the development of methodology to calibrate the above-described constitutive equation using actual experimental materials data together with regression analysis of that data, thereby predicting values for the empirical material constants for each effect or primitive variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from industry and the open literature for materials typically for applications in aerospace propulsion system components. Material data for Inconel 718 was analyzed using the developed methodology.

  4. Computational simulation of probabilistic lifetime strength for aerospace materials subjected to high temperature, mechanical fatigue, creep and thermal fatigue

    NASA Technical Reports Server (NTRS)

    Boyce, Lola; Bast, Callie C.; Trimble, Greg A.

    1992-01-01

    This report presents the results of a fourth year effort of a research program, conducted for NASA-LeRC by the University of Texas at San Antonio (UTSA). The research included on-going development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subject to a number of effects or primitive variables. These primitive variables may include high temperature, fatigue or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation has been randomized and is included in the computer program, PROMISS. Also included in the research is the development of methodology to calibrate the above-described constitutive equation using actual experimental materials data together with regression analysis of that data, thereby predicting values for the empirical material constants for each effect or primitive variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from industry and the open literature for materials typically for applications in aerospace propulsion system components. Material data for Inconel 718 has been analyzed using the developed methodology.

  5. Changes in force and intracellular metabolites during fatigue of human skeletal muscle.

    PubMed Central

    Cady, E B; Jones, D A; Lynn, J; Newham, D J

    1989-01-01

    1. The relationship between intracellular metabolites and the generation of force during fatigue has been examined in the first dorsal interosseous muscle of the hand. With the arm made ischaemic, the muscle was fatigued by three bouts of maximal voluntary contraction, leaving approximately three minutes ischaemic rest between contractions. During one series of experiments intracellular phosphorus metabolites were measured by nuclear magnetic resonance during the intervals between the fatiguing contractions: in the second series contractile properties were tested with brief electrical stimulation during the rest intervals. 2. The relationships between loss of force and change in metabolite concentrations obtained with four normal subjects were compared with those from one subject with myophosphorylase deficiency (MPD) who could not utilize muscle glycogen and therefore produced no hydrogen ion from glycolysis during exercise. 3. For both the MPD and normal subjects the relationship between relative force loss and inorganic phosphate (Pi) concentration was curvilinear, force changing little in the early stages of the contraction when the intracellular Pi was accumulating rapidly but falling faster when the Pi was above 25 mM and increasing relatively slowly. 4. In the normal subjects intracellular pH fell from a mean of 7.03 +/- 0.01 (mean +/- S.E. of mean, n = 19) in the fresh muscle to 6.51 +/- 0.02 at the end of the fatiguing exercise