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Sample records for muscle strength fatiguability

  1. Muscle strength, endurance and recovery in the post-infection fatigue syndrome.

    PubMed Central

    Lloyd, A R; Hales, J P; Gandevia, S C

    1988-01-01

    A test of muscle strength and "fatiguability" was administered to 20 normal subjects and 20 patients suffering from post-infection fatigue syndrome. Maximal isometric torque for the elbow flexors was measured before, during and after an endurance sequence of 18 maximal static contractions (10 s duration, 10 s rest interval). The maximal isometric strength was not significantly different between the patient and control groups. The relative torque produced at the end of the series of 18 static contractions did not differ significantly between patients and normal subjects. In the patients with post-infection fatigue syndrome there was impairment of the recovery of peak torque at 10 minutes after the endurance sequence (p less than 0.02). The prominent subjective complaint of muscle fatigue in patients with post-infection fatigue syndrome contrasts with the relatively normal behaviour of their muscles during a controlled test of fatigue. The syndrome may include a disordered perception of achieved force and exertion. PMID:2852211

  2. 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

  3. 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.

  4. 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

  5. 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)

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

    PubMed Central

    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. PMID:24701242

  7. Ischemia causes muscle fatigue.

    PubMed

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

    2001-05-01

    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. PMID:11398857

  8. 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.

  9. Muscle fatigue (image)

    MedlinePlus

    ... above your shoulders until they drop is one exercise that may be performed during the Tensilon test. In this test, the drug Tensilon is administered, and the response in the muscles are evaluated to help diagnose myasthenia gravis or ...

  10. 14 CFR 23.627 - Fatigue strength.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 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....

  11. 14 CFR 23.627 - Fatigue strength.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 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....

  12. 14 CFR 23.627 - Fatigue strength.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 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....

  13. 14 CFR 23.627 - Fatigue strength.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 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....

  14. 14 CFR 23.627 - Fatigue strength.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 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....

  15. A comparison of muscle strength and endurance, exercise capacity, fatigue perception and quality of life in patients with chronic obstructive pulmonary disease and healthy subjects: a cross-sectional study

    PubMed Central

    2014-01-01

    Background Chronic obstructive pulmonary disease (COPD) has significant systemic effects that substantially impact quality of life and survival. The purpose of this study was to assess and compare peripheral muscle strength and endurance, exercise capacity, fatigue perception and quality of life between patients with COPD and healthy subjects. Methods Twenty COPD patients (mean FEV1 49.3 ± 19.2%) and 20 healthy subjects were included in the study. Pulmonary function testing and six-minute walk test (6MWT) were performed. Peripheral muscle strength was measured with a hand-held dynamometer, peripheral muscle endurance was evaluated with sit-ups, squats and modified push-ups tests. Fatigue perception was assessed using the Fatigue Impact Scale (FIS) and Fatigue Severity Scale (FSS). General quality of life was determined with the Nottingham Health Profile (NHP), and cough-specific quality of life was evaluated with the Leicester Cough Questionnaire (LCQ). Results Pulmonary functions, strength of shoulder abductor and flexor muscles, numbers of sit-ups and squats, 6MWT distance and 6MWT% were significantly lower in COPD patients than in healthy subjects (p < 0.05). FIS psychosocial sub-dimension and total scores, NHP scores for all sub-dimensions except pain sub-dimension of the COPD group were significantly higher than those of healthy subjects (p < 0.05). The LCQ physical, psychological and social sub-dimensions and total scores were significantly lower in COPD patients than in healthy subjects (p < 0.05). Conclusions Pulmonary functions, peripheral muscle strength and endurance, exercise capacity and quality of life were adversely affected in patients with COPD. There are greater effect of fatigue on psychosocial functioning and general daily life activities and effect of cough on the quality of life in patients with COPD. This study supports the idea that COPD patients must be evaluated in a comprehensive manner for planning pulmonary

  16. 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

  17. 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. PMID:27147617

  18. 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.

  19. Optical Fiber Strength/Fatigue Experiments

    NASA Astrophysics Data System (ADS)

    Quan, F.; Helfinstine, J. D.

    1982-01-01

    Optical communication via hair-thin silica waveguides has revolutionized the telecommunications industry. Because its uses are spreading beyond telephony, with its relatively benign environments, to more exotic undersea and space applications, a new emphasis is now placed on optical fiber strength and fatigue characteristics. This paper will trace the historical development of optical waveguides strength/fatigue experiments and a recent attempt to determine the material fatigue constant "n" of modern silica waveguides. Stressing practical application, detailed derivations have been purposely left out for the sake of brevity.

  20. 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.

  1. Strength gradient enhances fatigue resistance of steels.

    PubMed

    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

  2. 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

  3. Strength gradient enhances fatigue resistance of steels

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  4. Understanding Muscle Dysfunction in Chronic Fatigue Syndrome

    PubMed Central

    Rutherford, Gina; Manning, Philip; Newton, Julia L.

    2016-01-01

    Introduction. Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is a debilitating disorder of unknown aetiology, characterised by severe disabling fatigue in the absence of alternative diagnosis. Historically, there has been a tendency to draw psychological explanations for the origin of fatigue; however, this model is at odds with findings that fatigue and accompanying symptoms may be explained by central and peripheral pathophysiological mechanisms, including effects of the immune, oxidative, mitochondrial, and neuronal pathways. For example, patient descriptions of their fatigue regularly cite difficulty in maintaining muscle activity due to perceived lack of energy. This narrative review examined the literature for evidence of biochemical dysfunction in CFS/ME at the skeletal muscle level. Methods. Literature was examined following searches of PUB MED, MEDLINE, and Google Scholar, using key words such as CFS/ME, immune, autoimmune, mitochondria, muscle, and acidosis. Results. Studies show evidence for skeletal muscle biochemical abnormality in CFS/ME patients, particularly in relation to bioenergetic dysfunction. Discussion. Bioenergetic muscle dysfunction is evident in CFS/ME, with a tendency towards an overutilisation of the lactate dehydrogenase pathway following low-level exercise, in addition to slowed acid clearance after exercise. Potentially, these abnormalities may lead to the perception of severe fatigue in CFS/ME. PMID:26998359

  5. Understanding Muscle Dysfunction in Chronic Fatigue Syndrome.

    PubMed

    Rutherford, Gina; Manning, Philip; Newton, Julia L

    2016-01-01

    Introduction. Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is a debilitating disorder of unknown aetiology, characterised by severe disabling fatigue in the absence of alternative diagnosis. Historically, there has been a tendency to draw psychological explanations for the origin of fatigue; however, this model is at odds with findings that fatigue and accompanying symptoms may be explained by central and peripheral pathophysiological mechanisms, including effects of the immune, oxidative, mitochondrial, and neuronal pathways. For example, patient descriptions of their fatigue regularly cite difficulty in maintaining muscle activity due to perceived lack of energy. This narrative review examined the literature for evidence of biochemical dysfunction in CFS/ME at the skeletal muscle level. Methods. Literature was examined following searches of PUB MED, MEDLINE, and Google Scholar, using key words such as CFS/ME, immune, autoimmune, mitochondria, muscle, and acidosis. Results. Studies show evidence for skeletal muscle biochemical abnormality in CFS/ME patients, particularly in relation to bioenergetic dysfunction. Discussion. Bioenergetic muscle dysfunction is evident in CFS/ME, with a tendency towards an overutilisation of the lactate dehydrogenase pathway following low-level exercise, in addition to slowed acid clearance after exercise. Potentially, these abnormalities may lead to the perception of severe fatigue in CFS/ME. PMID:26998359

  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. 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). PMID:21411058

  8. Rate of Force Development in the Handgripping Muscles by Females as a Function of Fatigue Level.

    ERIC Educational Resources Information Center

    Ewing, John L., Jr.; Stull, G. Alan

    1984-01-01

    This study determined the effects on the rate at which the handgripping muscles in college-age females develop force when they are fatigued to 80, 60, and 40 percent of their original maximal strength level. (JMK)

  9. Improving fatigue strength of welded joints

    NASA Astrophysics Data System (ADS)

    Takamori, Hiroyuki

    One series of fatigue tests was carried out on coverplated bridge girders with small fatigue cracks that had been treated in 1976. The treatment and preconditions were reported in NCHRP Report 206. The Category E' coverplated. beams that were removed from the Yellow Mill Pond Bridge in 1997 had been retrofitted in 1976 by either air hammer peening or GTA remelting the weld toe. Most of the details had small fatigue cracks at the time the retrofit was carried out. No detectable fatigue cracking was observed at the treated coverplate ends after 20 years of service on I-95 and an estimated 56 million truck passages. All beams were tested at a stress range of 69 MPa (10 ksi). Cracks eventually developed from the root of the transverse end welds and propagated through the weld throat and from there into the beam flange via the longitudinal welds. The fatigue resistance of the treated weld toe details was improved to Category C. The one GTA remelted detail that recracked at the weld toe exceeded Category D. The second series of tests was carried out on large scale HPS-485W steel plate girders with as-welded and ultrasonic impact treated (UIT) details. The UIT treatment was applied to the weld toe of transverse stiffeners welded to the web and flanges (Category C details) and to coverplated ends (Category E' details). The as-welded details cracked as expected at their corresponding fatigue resistance. All UIT treated details were improved. The treated transverse stiffeners achieved Category B fatigue resistance. The treated coverplated details achieved Category C. The third series of tests was conducted on large scale HPS-485W steel plate girders with undermatched groove welded details at flange transition. The objectives of using undermatched weld materials compared to the base material is to reduce the potentiality of hydrogen cracking at flange groove welds and to improve the fatigue strength of the welded joints. Fatigue strength of undermatched welded joints was

  10. 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. PMID:25248344

  11. 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.

  12. Consequences of lower extremity and trunk muscle fatigue on balance and functional tasks in older people: A systematic literature review

    PubMed Central

    2010-01-01

    Background Muscle fatigue reduces muscle strength and balance control in young people. It is not clear whether fatigue resistance seen in older persons leads to different effects. In order to understand whether muscle fatigue may increase fall risk in older persons, a systematic literature review aimed to summarize knowledge on the effects of lower extremity and trunk muscle fatigue on balance and functional tasks in older people was performed. Methods Studies were identified with searches of the PUBMED and SCOPUS data bases. Papers describing effects of lower extremity or trunk muscle fatigue protocols on balance or functional tasks in older people were included. Studies were compared with regards to study population characteristics, fatigue protocol, and balance and functional task outcomes. Results Seven out of 266 studies met the inclusion criteria. Primary findings were: fatigue via resistance exercises to lower limb and trunk muscles induces postural instability during quiet standing; induced hip, knee and ankle muscle fatigue impairs functional reach, reduces the speed and power of sit-to-stand repetitions, and produces less stable and more variable walking patterns; effects of age on degree of fatigue and rate of recovery from fatigue are inconsistent across studies, with these disparities likely due to differences in the fatigue protocols, study populations and outcome measures. Conclusion Taken together, the findings suggest that balance and functional task performance are impaired with fatigue. Future studies should assess whether fatigue is related to increased risk of falling and whether exercise interventions may decrease fatigue effects. PMID:20716373

  13. A description of spinal fatigue strength.

    PubMed

    Huber, Gerd; Nagel, Katrin; Skrzypiec, Daniel M; Klein, Anke; Püschel, Klaus; Morlock, Michael M

    2016-04-11

    Understanding fatigue failure of the spine is important to establish dynamic loading limits for occupational health and safety. In this study experimental data were combined with published data to develop a description of the predictive parameters for spinal fatigue failure. 41 lumbar functional spinal units (FSUs) from cadaveric spines (age 49.0±11.9yr) where cyclically loaded. Three different levels of sinusoidal axial compression (0-3kN, 0-2kN or 1-3kN) were applied for 300,000 cycles. Further, published data consisted of 70 thoracic and lumbar FSUs loaded in axial compression for 5000 cycles. Cyclic forces ranged from lower peaks (Fmin) of 0.7-1kN to upper peaks (Fmax) of 1.2-7.1kN. Based on Wöhler analysis, a fatigue model was developed accounting for three parameters: I) specimen-specific scaling based on the endplate area, II) specimen-specific strength dependency on age or bone mineral density, III) load-specific correction factors based on Fmax and Fmin. The most predictive model was achieved for a combination of Fmax, endplate area and bone mineral density; this model explained 61% of variation (p<0.001). A model including Fmax, endplate area and age explained only 28% of variation (p<0.001). Inclusion of a load-specific correction factor did not significantly improve model prediction of fatigue failure. This analysis presents the basis for the prediction of specimen-specific fatigue failure of the lumbar spine, provided the endplate area and bone mineral density can be derived. PMID:26948575

  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. [On fatigue bending strength of PMMA-specimen (author's transl)].

    PubMed

    Rojczyk, M; Rojczyk-Pflüger, J

    1980-01-01

    The fatigue response of PMMA-specimen was tested under cyclic bending of 1.5 Hz in a particularly designed testing device. Specimen were tested that a "Wöhler" curve and the corresponding fatigue strength could be evaluated. The fatigue strength was reached after a comparatively short time and ranged in the order of 33 per cent of static breaking strength. PMID:7447658

  17. 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

  18. Fatigue strength of adhesive bonded section beams under torsion

    SciTech Connect

    Tomioka, Noboru; Kakiage, Masashi; Niisawa, Junetsu; Kitagawa, Hideo

    1995-11-01

    Fatigue strength of adhesive bonded box beams was investigated. From results of the fatigue tests, it was seen that the fatigue strength of bonded beams was higher than that of spot welded beams. Fatigue strength of bonded beams was independent of plate thickness and partition. The flexural rigidity of the box beams in the plane of partition can increase without decrease of torsional rigidity and torsional fatigue strength, if the partition is jointed by adhesive bonding instead of spot welding. Since the fatigue strength and rigidity of adhesive bonded joints can be higher than the spot welded joints in the weight saving structures, it is expected that the structural adhesive joints will be employed more in the automobile body structure. For assuring the introduction of this joint more into the automobile body structures, it is necessary that the fatigue tests on the model members of the actual members used in the automobile body structure are conducted, in addition to those of the simple joints such as tension shear and T-type tension, and the property of the fatigue strength on the adhesive bonded members is known. But, the authors now have little data on fatigue tests of the adhesive bonded members. In the present research to be reported, the fatigue tests on adhesive bonded box beams under torsion, which are typical members in automobile body structure, were carried out and the effects of the presence of longitudinal partition and plate thickness on fatigue strength were investigated. Comparing the results of fatigue tests on adhesive bonded box beams with those on spot welded box beams, the property of fatigue strength on these adhesive bonded box beams was cleared.

  19. Concentric Internal and Eccentric External Fatigue Resistanc of the Shoulder Rotator Muscles in Female Tennis Players

    PubMed Central

    Niederbracht, Yvonne

    2008-01-01

    Background Shoulder muscle imbalance is a potential shoulder injury risk factor in athletes performing overhead sports. While normative functional peak strength of concentric external to concentric internal shoulder muscle fatigue data is available, comparisons of functional eccentric external to concentric internal shoulder rotator muscle fatigue resistance, which impacts muscle imbalance throughout the duration of play, have not been studied in this population. Objectives To assess fatigue resistance of the internal and external shoulder rotator muscles in female tennis players. Methods Fifteen female collegiate tennis players were tested bilaterally for shoulder concentric internal and eccentric external peak torque production throughout 20 maximal repetitions on a Kin-Com isokinetic dynamometer. Twelve t - tests were conducted to evaluate for differences in peak torque, relative fatigue ratios, and functional peak torque ratios between extremities and mode of activation during the first, as well as, last five repetitions that were conducted. Results Non-dominant concentric internal and eccentric external peak torque production significantly decreased throughout the twenty repetitions. Neither dominant concentric internal peak torque decrements and eccentric peak torque decrements were not significantly different across the twenty contractions. These changes in peak torque upon subsequent repetitions resulted in relative fatigue ratios of dominant eccentric external rotation that were significantly greater than non-dominant eccentric external rotation. Relative fatigue ratios of dominant concentric internal rotation did not differ from non-dominant concentric internal rotation. Conclusions The data suggest that eccentrically activated external shoulder rotator muscles could possibly adapt to overhead activities by becoming more fatigue resistant. PMID:21509131

  20. The effects of strength training and disuse on the mechanisms of fatigue.

    PubMed

    Behm, D G; St-Pierre, D M

    1998-03-01

    Increases in force, electromyography, reflex potentiation, muscle action potential amplitude and protein synthesis occur with strength training. Training-induced increases in the efficiency of the neuromuscular system and capacity of the muscle to generate force result in an improved ability to cope with a submaximal load. There is also some evidence of improved fatigue resistance with maximal contractions which could be attributed to a prolongation of membrane excitation or decreased antagonist activity with training. On the other hand, although a variety of factors including strength are diminished with disuse, a number of studies have demonstrated no significant difference in the rate of fatigue with maximal contractions (fatigue index) between trained, untrained and disused muscle. Equivalent control and disuse fatigue indexes in some studies might be attributed to decreased muscle activation resulting in a comparison of maximal (control) and submaximal (disuse) efforts. Furthermore, increases in the duration of muscle membrane electrical propagation with disuse may increase the quantity of Ca++ released, augmenting force production. In addition, the smaller volume of disused muscle may allow a more efficient diffusion of oxygen and energy substrates in comparison with a hypertrophied muscle. PMID:9554028

  1. 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…

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. N-acetylcysteine inhibits muscle fatigue in humans.

    PubMed Central

    Reid, M B; Stokić, D S; Koch, S M; Khawli, F A; Leis, A A

    1994-01-01

    N-acetylcysteine (NAC) is a nonspecific antioxidant that selectively inhibits acute fatigue of rodent skeletal muscle stimulated at low (but not high) tetanic frequencies and that decreases contractile function of unfatigued muscle in a dose-dependent manner. The present experiments test the hypothesis that NAC pretreatment can inhibit acute muscular fatigue in humans. Healthy volunteers were studied on two occasions each. Subjects were pretreated with NAC 150 mg/kg or 5% dextrose in water by intravenous infusion. The subject then sat in a chair with surface electrodes positioned over the motor point of tibialis anterior, an ankle dorsiflexor of mixed-fiber composition. The muscle was stimulated to contract electrically (40-55 mA, 0.2-ms pulses) and force production was measured. Function of the unfatigued muscle was assessed by measuring the forces produced during maximal voluntary contractions (MVC) of ankle dorsiflexor muscle groups and during electrical stimulation of tibialis anterior at 1, 10, 20, 40, 80, and 120 Hz (protocol 1). Fatigue was produced using repetitive tetanic stimulations at 10 Hz (protocol 1) or 40 Hz (protocol 2); intermittent stimulations subsequently were used to monitor recovery from fatigue. The contralateral leg then was studied using the same protocol. Pretreatment with NAC did not alter the function of unfatigued muscle; MVC performance and the force-frequency relationship of tibialis anterior were unchanged. During fatiguing contractions stimulated at 10 Hz, NAC increased force output by approximately 15% (P < 0.0001), an effect that was evident after 3 min of repetitive contraction (P < 0.0125) and persisted throughout the 30-min protocol. NAC had no effect on fatigue induced using 40 Hz stimuli or on recovery from fatigue. N-acetylcysteine pretreatment can improve performance of human limb muscle during fatiguing exercise, suggesting that oxidative stress plays a causal role in the fatigue process and identifying antioxidant

  7. Effect of acetazolamide on respiratory muscle fatigue in humans.

    PubMed

    Gonzales, Joaquin U; Scheuermann, Barry W

    2013-01-15

    Previous studies have demonstrated that carbonic anhydrase inhibition with acetazolamide reduces exercise capacity. The mechanism responsible for this early fatigue is unclear, but may be partly mediated by impaired respiratory muscle function. Inspiratory muscle strength and endurance were assessed in seven healthy men (age 28 ± 5 yrs, ±SD) by measuring maximal inspiratory pressure (MIP) and time to task failure during a constant-load breathing test (CLBT), respectively, under control (CON) and acetazolamide (ACZ; 500 mg/8 h po for 3 days) conditions that were separated by two weeks and randomized between subjects. In addition, MIP was measured before and after moderate-intensity cycling exercise to fatigue while pulmonary gas exchange, plasma pH, and ventilation were measured during exercise. ACZ did not alter pulmonary function (FVC, FEV1, MVV) or MIP measured at rest (CON, -157 ± 47 vs. ACZ, -154 ± 45 cmH(2)O, p>0.05), but decreased time to task failure during the CLBT (CON, 1340 ± 820 vs. ACZ, 698 ± 434 s; p=0.01). Exercise duration during cycling exercise was reduced (p=0.003) with ACZ (1090 ± 254 s) compared to CON (1944 ± 532 s) in the presence of a significantly lower plasma pH and higher ventilation compared to control (p<0.05). Compared to resting values, MIP was reduced (p=0.03) in ACZ but not CON at exhaustion. In conclusion, carbonic anhydrase inhibition with ACZ is associated with impaired respiratory muscle function at rest and following constant load cycling which may contribute to reduced exercise tolerance with carbonic anhydrase inhibition. PMID:23017330

  8. The Relationship Between Muscle Fatigue and Balance in the Elderly

    PubMed Central

    Nam, Hee Seung; Park, Dong Sik; Kim, Dong Hyun; Kang, Hyun Jung; Lee, Dong Hun; Lee, Sang Hun; Her, Jin Gang; Woo, Ji Hea

    2013-01-01

    Objective To investigate the effect of gastrocnemius muscle fatigue on postural control ability in elderly people. Methods Twenty-four healthy elderly people participated in this study. The postural control ability of single leg standing was evaluated with Health Improvement & Management System (HIMS) posturography before and after fatiguing exercises. After evaluating initial postural control ability, the maximal voluntary contraction (MVC) of ankle plantarflexion was assessed using a surface electromyogram from the medial belly of the gastrocnemius muscle. After a 5-minute resting period, subjects began submaximal isometric ankle plantarflexion (40% MVC) until 40% of MVC was dropped below 95% for 5 seconds, or subject couldn't continue working out due to muscle fatigue. And postural control ability was assessed after fatiguing exercise. The mean deviation of center of pressure (COP), length of COP movement, occupied area of COP were measured, and analyzed by paired t-test. Results Mediolateral deviation, length of COP movement, and area of COP occupied were increased after fatiguing exercise of the gastrocnemius muscle. Anteroposterior deviation and length of COP movement were also increased, but had low statistical significance. Conclusion These findings suggest that the gastrocnemius muscle fatigue affects mediolateral stability and accuracy during single leg standing in elderly people. Therefore muscle endurance training is necessary to prevent falls in elderly people. PMID:23869337

  9. Extrapulmonary features of bronchiectasis: muscle function, exercise capacity, fatigue, and health status

    PubMed Central

    2012-01-01

    Background There are limited number of studies investigating extrapulmonary manifestations of bronchiectasis. The purpose of this study was to compare peripheral muscle function, exercise capacity, fatigue, and health status between patients with bronchiectasis and healthy subjects in order to provide documented differences in these characteristics for individuals with and without bronchiectasis. Methods Twenty patients with bronchiectasis (43.5 ± 14.1 years) and 20 healthy subjects (43.0 ± 10.9 years) participated in the study. Pulmonary function, respiratory muscle strength (maximal expiratory pressure – MIP - and maximal expiratory pressure - MEP), and dyspnea perception using the Modified Medical Research Council Dyspnea Scale (MMRC) were determined. A six-minute walk test (6MWT) was performed. Quadriceps muscle, shoulder abductor, and hand grip strength (QMS, SAS, and HGS, respectively) using a hand held dynamometer and peripheral muscle endurance by a squat test were measured. Fatigue perception and health status were determined using the Fatigue Severity Scale (FSS) and the Leicester Cough Questionnaire (LCQ), respectively. Results Number of squats, 6MWT distance, and LCQ scores as well as lung function testing values and respiratory muscle strength were significantly lower and MMRC and FSS scores were significantly higher in patients with bronchiectasis than those of healthy subjects (p < 0.05). In bronchiectasis patients, QMS was significantly associated with HGS, MIP and MEP (p < 0.05). The 6MWT distance was significantly correlated to LCQ psychological score (p < 0.05). The FSS score was significantly associated with LCQ physical and total and MMRC scores (p < 0.05). The LCQ psychological score was significantly associated with MEP and 6MWT distance (p < 0.05). Conclusions Peripheral muscle endurance, exercise capacity, fatigue and health status were adversely affected by the presence of bronchiectasis. Fatigue was associated

  10. Fatigue Properties of Automobile High-Strength Bolts

    NASA Astrophysics Data System (ADS)

    Zhou, Congling; Nishida, Shin-Ichi; Hattori, Nobusuke

    This study is focused on the fatigue properties of automobile high-strength bolts, including the effect of mean stress level, pre-processing schedule and the residual stresses. And the mean stress levels are 0.3, 0.5 and 0.7 times to the tensile strength (σB) of the material respectively. The main results obtained are as follows: 1) the fatigue strength increases under the mean stress loading, but the differences between the loading levels are not so evident; 2) most of the cases in this study are broken from the bottom of the screw thread, and the crack initiated from the impurities.

  11. 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.

  12. 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.

  13. 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. PMID:17277977

  14. 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.

  15. Carbohydrate Mouth Rinse Counters Fatigue Related Strength Reduction.

    PubMed

    Jensen, Matt; Stellingwerff, Trent; Klimstra, Marc

    2015-06-01

    The purpose was to determine the effect of carbohydrate (CHO) mouth rinse on maximal voluntary contraction (MVC) and neuromuscular output in a fatigued state. It was hypothesized that CHO mouth rinse would potentiate torque output in a fatigued state. In a double-blind, cross-over design, 12 competitive male athletes (9 rowers, 1 cyclist, 1 runner and 1 volleyball player) initially performed 3 × 5 s MVC isometric knee extensions followed by a 50% MVC contraction until volitional exhaustion, with quadriceps muscle activity measured via electromyography (EMG). Immediately after, either an 8% CHO maltodextrin (WASH), or noncaloric artificial sweetener (PLA) was mouth rinsed for 10sec, before 3 × 5 s final MVCs. Fatigue caused a significant decline in post fatigue MVC trial 1 for 3 s average torque (p = .03) and peak torque (p = .02) for PLA. This fatigue related decline in torque was not noticed for WASH, with a 2.5% and 3.5% less attenuation in peak and average torque, respectively in post fatigue MVC1 compared with PLA. The effect size for MVC trial 1 between WASH/PLA was seen to be small positive (ES = 0.22; 55% likelihood of positive). Overall for EMG RMS, there were no significant differences between PLA and WASH among all muscles. EMG median frequency showed comparable results between conditions with significant reductions due to fatigue. Taken together, this evidence suggests that the attenuation of torque post fatigue was less for CHO mouth rinse than a placebo. Even though the gains were marginal, these discoveries may play an important role in sport performance, as small performance effects can have significant outcomes in real-world competitions. PMID:25203506

  16. Assessment of respiratory muscle function and strength.

    PubMed Central

    Syabbalo, N.

    1998-01-01

    Measurement of respiratory muscle strength is useful in order to detect respiratory muscle weakness and to quantify its severity. In patients with severe respiratory muscle weakness, vital capacity is reduced but is a non-specific and relatively insensitive measure. Conventionally, inspiratory and expiratory muscle strength has been assessed by maximal inspiratory and expiratory mouth pressures sustained for 1 s (PImax and PEmax) during maximal static manoeuvre against a closed shutter. However, PImax and PEmax are volitional tests, and are poorly reproducible with an average coefficient of variation of 25%. The sniff manoeuvre is natural and probably easier to perform. Sniff pressure, and sniff transdiaphragmatic pressure are more reproducible and useful measure of diaphragmatic strength. Nevertheless, the sniff manoeuvre is also volition-dependent, and submaximal efforts are most likely to occur in patients who are ill or breathless. Non-volitional tests include measurements of twitch oesophageal, gastric and transdiaphragmatic pressure during bilateral electrical and magnetic phrenic nerve stimulation. Electrical phrenic nerve stimulation is technically difficult and is also uncomfortable and painful. Magnetic phrenic nerve stimulation is less painful and transdiaphragmatic pressure is reproducible in normal subjects. It is a relatively easy test that has the potential to become a widely adopted method for the assessment of diaphragm strength. The development of a technique to measure diaphragmatic sound (phonomyogram) during magnetic phrenic nerve stimulation opens the way for noninvasive assessment of diaphragmatic function. PMID:9683973

  17. 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. PMID:25701006

  18. Measurement of voluntary activation of fresh and fatigued human muscles using transcranial magnetic stimulation

    PubMed Central

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

    2003-01-01

    Recently, transcranial magnetic stimulation of the motor cortex (TMS) revealed impaired voluntary activation of muscles during maximal efforts. Hence, we evaluated its use as a measure of voluntary activation over a range of contraction strengths in both fresh and fatigued muscles, and compared it with standard twitch interpolation using nerve stimulation. Subjects contracted the elbow flexors isometrically while force and EMG from biceps and triceps were recorded. In one study, eight subjects made submaximal and maximal test contractions with rests to minimise fatigue. In the second study, eight subjects made sustained maximal contractions to reduce force to 60 % of the initial value, followed by brief test contractions. Force responses were recorded following TMS or electrical stimulation of the biceps motor nerve. In other contractions, EMG responses to TMS (motor evoked potentials, MEPs) or to stimulation at the brachial plexus (maximal M waves, Mmax) were recorded. During contractions of 50 % maximum, TMS elicited large MEPs in biceps (> 90 % Mmax) which decreased in size (to ≈70 % Mmax) with maximal efforts. This suggests that faster firing rates made some motor units effectively refractory. With fatigue, MEPs were also smaller but remained > 70 % Mmax for contractions of 50–100 % maximum. For fresh and fatigued muscle, the superimposed twitch evoked by motor nerve and motor cortex stimulation decreased with increasing contraction strength. For nerve stimulation the relation was curvilinear, and for TMS it was linear for contractions of 50–100 % maximum (r2 = 1.00). Voluntary activation was derived using the expression: (1 – superimposed twitch/resting twitch) × 100. The resting twitch was measured directly for nerve stimulation and for TMS, it was estimated by extrapolation of the linear regression between the twitch and voluntary force. For cortical stimulation, this resulted in a highly linear relation between voluntary activation and force

  19. Source Localization of Eeg Signals during Muscle Fatigue

    NASA Astrophysics Data System (ADS)

    Liu, Jing Z.; Yao, Bing; Lewandowski, Beth E.; Karakasis, Chris; Brown, Robert W.; Yue, Guang H.

    2003-10-01

    In this study we determined sources of EEG signals during a fatigue process involving intermittent maximal voluntary contractions (MVCs). In the fatigue motor task, subjects consecutively performed 200 trials of handgrip MVCs, each lasted 2 s, followed by a 5-s rest. In the control task, subjects performed the same task but the rest time was 28 s, and there was also a 5-min rest after each 40 trials so that fatigue effect was minimized. EEG signals were recorded along with handgrip force and EMG data. Current dipole model was applied to determine the signal sources in a three-sphere homogeneous head frame. Effects of fatigue on the signal source were determined. The results showed no significant changes in dipole strength and orientation but significant larger movement ranges in the dipole location during the fatigue process than during the control, indicating fatigue-related rotation of the center of cortical activation.

  20. Exogenously Applied Muscle Metabolites Synergistically Evoke Sensations of Muscle Fatigue and Pain in Human Subjects

    PubMed Central

    Pollak, Kelly A.; Swenson, Jeffrey D.; Vanhaitsma, Timothy A.; Hughen, Ronald W.; Jo, Daehyun; Light, Kathleen C.; Schweinhardt, Petra; Amann, Markus; Light, Alan R.

    2013-01-01

    The perception of fatigue is common in many disease states, however, the mechanisms of sensory muscle fatigue are not understood. In mice, rats and cats, muscle afferents signal metabolite production in skeletal muscle using a complex of ASIC, P2X and TRPV1 receptors. Endogenous muscle agonists for these receptors are combinations of protons, lactate, and ATP. Here we applied physiological concentrations of these agonists to muscle interstitium in human subjects to determine if this combination could activate sensations, and if so determined how these subjects described these sensations. Ten volunteers received infusions (0.2 ml over 30-s) containing protons, lactate and ATP under the fascia of a thumb muscle, abductor pollicis brevis (APB). Infusion of individual metabolites at maximum amounts evoked no fatigue or pain. Metabolite combinations found in resting muscles (pH 7.4+300nM ATP+1mM lactate) also evoked no sensation. The infusion of a metabolite-combination found in muscle during moderate endurance-exercise (pH 7.3+400nM ATP+5 mM lactate) produced significant fatigue sensations. Infusion of a metabolite-combination associated with vigorous exercise (pH 7.2+500nM ATP+10mM lactate) produced stronger sensations of fatigue and some ache. Higher levels of metabolites (as found with ischemic exercise) caused more ache but no additional fatigue-sensation. Thus, in a dose-dependent manner, intramuscular infusion of combinations of protons, lactate, and ATP leads to fatigue-sensation and eventually pain, probably through activation of ASIC, P2X, and TRPV1 receptors. This is the first demonstration in humans that metabolites normally produced by exercise act in combination to activate sensory neurons that signal sensations of fatigue and muscle pain. PMID:24142455

  1. 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.

  2. Changes in interhemispheric motor connectivity after muscle fatigue

    NASA Astrophysics Data System (ADS)

    Peltier, Scott; LaConte, Stephen M.; Niyazov, Dmitriy; Liu, Jing; Sahgal, Vinod; Yue, Guang; Hu, Xiaoping

    2005-04-01

    Synchronized oscillations in resting state timecourses have been detected in recent fMRI studies. These oscillations are low frequency in nature (< 0.08 Hz), and seem to be a property of symmetric cortices. These fluctuations are important as a potential signal of interest, which could indicate connectivity between functionally related areas of the brain. It has also been shown that the synchronized oscillations decrease in some spontaneous pathological states. Thus, detection of these functional connectivity patterns may help to serve as a gauge of normal brain activity. The cognitive effects of muscle fatigue are not well characterized. Sustained fatigue has the potential to dynamically alter activity in brain networks. In this work, we examined the interhemispheric correlations in the left and right primary motor cortices and how they change with muscle fatigue. Resting-state functional MRI imaging was done before and after a repetitive unilateral fatigue task. We find that the number of significant correlations in the bilateral motor network decreases with fatigue. These results suggest that resting-state interhemispheric motor cortex functional connectivity is affected by muscle fatigue.

  3. 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.

  4. Relationship Between Intensity of Quadriceps Muscle Neuromuscular Electrical Stimulation and Strength Recovery After Total Knee Arthroplasty

    PubMed Central

    Balter, Jaclyn E.; Wolfe, Pamela; Eckhoff, Donald G.; Schwartz, Robert S.; Schenkman, Margaret; Kohrt, Wendy M.

    2012-01-01

    Background Neuromuscular electrical stimulation (NMES) can facilitate the recovery of quadriceps muscle strength after total knee arthroplasty (TKA), yet the optimal intensity (dosage) of NMES and its effect on strength after TKA have yet to be determined. Objective The primary objective of this study was to determine whether the intensity of NMES application was related to the recovery of quadriceps muscle strength early after TKA. A secondary objective was to quantify quadriceps muscle fatigue and activation immediately after NMES to guide decisions about the timing of NMES during rehabilitation sessions. Design This study was an observational experimental investigation. Methods Data were collected from 30 people who were 50 to 85 years of age and who received NMES after TKA. These people participated in a randomized controlled trial in which they received either standard rehabilitation or standard rehabilitation plus NMES to the quadriceps muscle to mitigate strength loss. For the NMES intervention group, NMES was applied 2 times per day at the maximal tolerable intensity for 15 contractions beginning 48 hours after surgery over the first 6 weeks after TKA. Neuromuscular electrical stimulation training intensity and quadriceps muscle strength and activation were assessed before surgery and 3.5 and 6.5 weeks after TKA. Results At 3.5 weeks, there was a significant association between NMES training intensity and a change in quadriceps muscle strength (R2=.68) and activation (R2=.22). At 6.5 weeks, NMES training intensity was related to a change in strength (R2=.25) but not to a change in activation (R2=.00). Furthermore, quadriceps muscle fatigue occurred during NMES sessions at 3.5 and 6.5 weeks, whereas quadriceps muscle activation did not change. Limitations Some participants reached the maximal stimulator output during at least 1 treatment session and might have tolerated more stimulation. Conclusions Higher NMES training intensities were associated with

  5. 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. PMID:20824283

  6. 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

  7. Strength Training Induces Muscle Hypertrophy and Functional Gains in Black Prostate Cancer Patients Despite Androgen Deprivation Therapy

    PubMed Central

    Hurley, Ben F.

    2013-01-01

    Background. 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. Methods. 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. Results. 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). Conclusions. 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. PMID:23089339

  8. 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.

  9. 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%.

  10. 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.

  11. 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

  12. 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

  13. Effect of Microstructure on Fatigue Strength of Bovine Compact Bones

    NASA Astrophysics Data System (ADS)

    Kim, Jong Heon; Niinomi, Mitsuo; Akahori, Toshikazu; Takeda, Junji; Toda, Hiroyuki

    Despite its clinical importance in developing artificial bone, limited information is available regarding the microstructure with respect to the fatigue characteristics of bones. In this study, the fatigue characteristics of the bovine humerus and femur were investigated with respect to microstructures. Fatigue tests were conducted on the bovine humerus and femur at a stress ratio of 0.1 and a frequency of 10Hz. The fatigue strength of the plexiform bone is slightly greater than that of the haversian bone. This is because the volume fraction of voids in the haversian bone, which is the site of stress concentration, is higher than that of voids in the plexiform bone. Several microcracks are observed on the fatigue fracture surface of the haversian bone. The microcracks are short and their propagation directions are random. However, the number of the microcracks in the plexiform bone is very small. The microcracks are relatively long and their propagation directions are parallel to the longitudinal direction of the lamellar bone. Therefore, the crack requires relatively more energy to propagate across the lamella in the plexiform bone.

  14. 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

  15. 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

  16. Unsupported standing with minimized ankle muscle fatigue.

    PubMed

    Mihelj, Matjaz; Munih, Marko

    2004-08-01

    In the past, limited unsupported standing has been restored in patients with thoracic spinal cord injury through open-loop functional electrical stimulation of paralyzed knee extensor muscles and the support of intact arm musculature. Here an optimal control system for paralyzed ankle muscles was designed that enables the subject to stand without hand support in a sagittal plane. The paraplegic subject was conceptualized as an underactuated double inverted pendulum structure with an active degree of freedom in the upper trunk and a passive degree of freedom in the paralyzed ankle joints. Control system design is based on the minimization of a cost function that estimates the effort of ankle joint muscles via observation of the ground reaction force position, relative to ankle joint axis. Furthermore, such a control system integrates voluntary upper trunk activity and artificial control of ankle joint muscles, resulting in a robust standing posture. Figures are shown for the initial simulation study, followed by disturbance tests on an intact volunteer and several laboratory trials with a paraplegic person. Benefits of the presented methodology are prolonged standing sessions and in the fact that the subject is able to maintain voluntary control over upper body orientation in space, enabling simple functional standing. PMID:15311817

  17. Effect of inspiratory muscle work on peripheral fatigue of locomotor muscles in healthy humans

    PubMed Central

    Romer, Lee M; Lovering, Andrew T; Haverkamp, Hans C; Pegelow, David F; Dempsey, Jerome A

    2006-01-01

    The work of breathing required during maximal exercise compromises blood flow to limb locomotor muscles and reduces exercise performance. We asked if force output of the inspiratory muscles affected exercise-induced peripheral fatigue of locomotor muscles. Eight male cyclists exercised at ≥ 90% peak O2 uptake to exhaustion (CTRL). On a separate occasion, subjects exercised for the same duration and power output as CTRL (13.2 ± 0.9 min, 292 W), but force output of the inspiratory muscles was reduced (−56% versus CTRL) using a proportional assist ventilator (PAV). Subjects also exercised to exhaustion (7.9 ± 0.6 min, 292 W) while force output of the inspiratory muscles was increased (+80% versus CTRL) via inspiratory resistive loads (IRLs), and again for the same duration and power output with breathing unimpeded (IRL-CTRL). Quadriceps twitch force (Qtw), in response to supramaximal paired magnetic stimuli of the femoral nerve (1–100 Hz), was assessed pre- and at 2.5 through to 70 min postexercise. Immediately after CTRL exercise, Qtw was reduced −28 ± 5% below pre-exercise baseline and this reduction was attenuated following PAV exercise (−20 ± 5%; P < 0.05). Conversely, increasing the force output of the inspiratory muscles (IRL) exacerbated exercise-induced quadriceps muscle fatigue (Qtw=−12 ± 8% IRL-CTRL versus −20 ± 7% IRL; P < 0.05). Repeat studies between days showed that the effects of exercise per se, and of superimposed inspiratory muscle loading on quadriceps fatigue were highly reproducible. In conclusion, peripheral fatigue of locomotor muscles resulting from high-intensity sustained exercise is, in part, due to the accompanying high levels of respiratory muscle work. PMID:16373384

  18. Effects of plantar flexor muscle fatigue induced by electromyostimulation on postural coordination.

    PubMed

    Ponce, Antoine; Fouque, Florent; Cahouët, Violaine; Martin, Alain

    2007-02-27

    The aim of the present study was to investigate the influence of a modification of an intrinsic capacity (plantar flexor strength) on the implementation of in-phase and anti-phase mode of coordination. Analysis of hip and ankle relative phases during fore-aft tracking task was done before and after an electromyostimulation fatigue protocol on the soleus muscles. Results showed participants used exclusively in-phase and anti-phase modes of coordination, with a sudden switch from one to the other with target frequency increase. Regarding tracking tasks, fatigue induces a decrease of performance for lower frequencies, and a significant decrease of switch frequency (-0.08 Hz) for each subject. In conclusion, changes in mode of coordination implementation suggest that the in-phase mode implementation is highly linked to the strength production capacity at the ankle joint. PMID:17280784

  19. 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.

  20. 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.

  1. The Development of Confidence Limits for Fatigue Strength Data

    SciTech Connect

    SUTHERLAND,HERBERT J.; VEERS,PAUL S.

    1999-11-09

    Over the past several years, extensive databases have been developed for the S-N behavior of various materials used in wind turbine blades, primarily fiberglass composites. These data are typically presented both in their raw form and curve fit to define their average properties. For design, confidence limits must be placed on these descriptions. In particular, most designs call for the 95/95 design values; namely, with a 95% level of confidence, the designer is assured that 95% of the material will meet or exceed the design value. For such material properties as the ultimate strength, the procedures for estimating its value at a particular confidence level is well defined if the measured values follow a normal or a log-normal distribution. Namely, based upon the number of sample points and their standard deviation, a commonly-found table may be used to determine the survival percentage at a particular confidence level with respect to its mean value. The same is true for fatigue data at a constant stress level (the number of cycles to failure N at stress level S{sub 1}). However, when the stress level is allowed to vary, as with a typical S-N fatigue curve, the procedures for determining confidence limits are not as well defined. This paper outlines techniques for determining confidence limits of fatigue data. Different approaches to estimating the 95/95 level are compared. Data from the MSU/DOE and the FACT fatigue databases are used to illustrate typical results.

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

    PubMed

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

    1992-06-01

    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) PMID:1535482

  3. 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).

  4. 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…

  5. 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

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

    PubMed Central

    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.

    2015-01-01

    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. PMID:25548157

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

    PubMed

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

    2016-05-01

    [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

  8. 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

  9. 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.

  10. 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.

  11. 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)

  12. 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.

  13. 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.

  14. 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.

  15. Fatigue behavior of high-strength concrete under marine conditions

    SciTech Connect

    Mor, A.

    1987-01-01

    In this study, 24 high-strength reinforced concrete beams were tested in fatigue under simulated marine conditions. Low-cycle, high-magnitude loading was imposed on beams, some of which were exposed to air, and others which were submerged in water. The beams were cycled at 1 Hz, to 80% of their yield capacity in negative and positive flexure. Four concrete mixes were compared. Half of the specimens were made with lightweight aggregate (LWA), and half were made with river gravel (NWA). Half of each group contained silica-fume as partial replacement of cement (13%). By manipulating the water/cement ratio, the 28-day compressive strength of all concretes was 9500 {plus minus} 300 psi. The previously reported phenomenon of water pumping through the cracks was observed, but did not appear to be directly related to the subsequent failure. When silica fume is added to the concrete mix, the adhesion is greatly improved. LWA concrete utilizes this additional adhesion effectively. NWA concrete with silica-fume, on the other hand, is not able to utilize the increased adhesion due to microcracking. Main findings of both the fatigue and pull-out bond tests are listed.

  16. 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

  17. Respiratory muscle strength in asthmatic children

    PubMed Central

    Marcelino, Alessandra Maria Farias Cavalcante; da Cunha, Daniele Andrade; da Cunha, Renata Andrade; da Silva, Hilton Justino

    2012-01-01

    Summary Introduction: Changes in the respiratory system of asthmatics are also due to the mechanical disadvantage caused by the increased airway resistance. Objective: The study aims to evaluate the respiratory muscle strength and nutritional status of asthmatic children. Method: This is a prospective descriptive and transversal study with 50 children aged 7 to 12 years, who were placed into 2 groups, asthmatic and non-asthmatic. Respiratory muscle strength was evaluated on the basis of maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP). The nutritional status was evaluated by measuring the anthropometric data, including height, weight, and body mass index (BMI). The findings were subjected to analysis of variance, chi-square, and Student's t test, and p-values < 0.05 was considered statistically significant. Results: In our comparisons, we observed statistically significantly lower values for age, weight, and height in asthmatic patients: 8.52 ± 1.49 years, 30.62 ± 7.66 kg, and 129.85 ± 10.24 cm, respectively, vs. non-asthmatic children(9.79 ± 1.51 years, 39.92 ± 16.57 kg, and 139.04 ± 11.62 cm, respectively). There was no significant increase in MIP and MEP between the groups: MIP was -84.96 ± 27.52 cmH2O for the asthmatic group and -88.56 ± 26.50 cmH2O for the non-asthmatic group, and MEP was 64.48 ± 19.23 cmH2O for asthmatic children and +66.72 ± 16.56 cmH2O for non-asthmatics. Conclusion: There was no statistically significant difference between groups, but we observed that MIP and MEP were slightly higher in the non-asthmatic group than in the asthmatic group. PMID:25991978

  18. 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…

  19. Fatigue alters in vivo function within and between limb muscles during locomotion.

    PubMed

    Higham, Timothy E; Biewener, Andrew A

    2009-03-22

    Muscle fatigue, a reduction in force as a consequence of exercise, is an important factor for any animal that moves, and can result from both peripheral and/or central mechanisms. Although much is known about whole-limb force generation and activation patterns in fatigued muscles under sustained isometric contractions, little is known about the in vivo dynamics of limb muscle function in relation to whole-body fatigue. Here we show that limb kinematics and contractile function in the lateral (LG) and medial (MG) gastrocnemius of helmeted guineafowl (Numida meleagris) are significantly altered following fatiguing exercise at 2ms-1 on an inclined treadmill. The two most significant findings were that the variation in muscle force generation, measured directly from the muscles' tendons, increased significantly with fatigue, and fascicle shortening in the proximal MG, but not the distal MG, decreased significantly with fatigue. We suggest that the former is a potential mechanism for decreased stability associated with fatigue. The region-specific alteration of fascicle behaviour within the MG as a result of fatigue suggests a complex response to fatigue that probably depends on muscle-aponeurosis and tendon architecture not previously explored. These findings highlight the importance of studying the integrative in vivo dynamics of muscle function in response to fatigue. PMID:19129096

  20. Isometric quadriceps strength determines sailing performance and neuromuscular fatigue during an upwind sailing emulation.

    PubMed

    Bourgois, Jan G; Callewaert, Margot; Celie, Bert; De Clercq, Dirk; Boone, Jan

    2016-01-01

    This study investigates the physiological responses to upwind sailing on a laser emulation ergometer and analyses the components of the physical profile that determine the physiological responses related to sailing level. Ten male high-level laser sailors performed an upwind sailing test, incremental cycling test and quadriceps strength test. During the upwind sailing test, heart rate (HR), oxygen uptake, ventilation, respiratory exchange ratio, rating of perceived exertion (RPE) and lactate concentration were measured, combined with near-infrared spectroscopy (NIRS) and electromyography (EMG) registration of the M. Vastus lateralis. Repeated measures ANOVA showed for the cardio-respiratory, metabolic and muscles responses (mean power frequency [MPF], root mean square [RMS], deoxy[Hb+Mb]) during the upwind sailing test an initial significant increase followed by a stabilisation, despite a constant increase in RPE. Stepwise regression analysis showed that better sailing level was for 46.5% predicted by lower MPF decrease. Lower MPF decrease was for 57.8% predicted by a higher maximal isometric quadriceps strength. In conclusion, this study indicates that higher sailing level was mainly determined by a lower rate of neuromuscular fatigue during the upwind sailing test (as indicated by MPF decrease). Additionally, the level of neuromuscular fatigue was mainly determined by higher maximal isometric quadriceps strength stressing the importance of resistance training in the planning of training. PMID:26323461

  1. 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.

  2. Comparative study of a muscle stiffness sensor and electromyography and mechanomyography under fatigue conditions.

    PubMed

    Han, Hyonyoung; Jo, Sungho; Kim, Jung

    2015-07-01

    This paper proposes the feasibility of a stiffness measurement for muscle contraction force estimation under muscle fatigue conditions. Bioelectric signals have been widely studied for the estimation of the contraction force for physical human-robot interactions, but the correlation between the biosignal and actual motion is decreased under fatigue conditions. Muscle stiffness could be a useful contraction force estimator under fatigue conditions because it measures the same physical quantity as the muscle contraction that generates the force. Electromyography (EMG), mechanomyography (MMG), and a piezoelectric resonance-based active muscle stiffness sensor were used to analyze the biceps brachii under isometric muscle fatigue conditions with reference force sensors at the end of the joint. Compared to EMG and MMG, the change in the stiffness signal was smaller (p < 0.05) in the invariable contraction force generation test until failure. In addition, in the various contraction level force generation tests, the stiffness signal under the fatigue condition changed <10% (p < 0.05) compared with the signal under non-fatigue conditions. This result indicates that the muscle stiffness signal is less sensitive to muscle fatigue than other biosignals. This investigation provides insights into methods of monitoring and compensating for muscle fatigue. PMID:25752771

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

    PubMed Central

    McConnell, Alison K; Lomax, Michelle

    2006-01-01

    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 (MVCTI); twitch interpolation assessed the level of central activation. PF was terminated (Tlim) when MVCTI was <50% of baseline MVC. PF Tlim 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 Tlim to control. After 4 weeks, IMT, inspiratory muscle work at the same absolute intensity did not influence PF Tlim, but Tlim 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. PMID:16973699

  4. Fatigue alters in vivo function within and between limb muscles during locomotion

    PubMed Central

    Higham, Timothy E.; Biewener, Andrew A.

    2008-01-01

    Muscle fatigue, a reduction in force as a consequence of exercise, is an important factor for any animal that moves, and can result from both peripheral and/or central mechanisms. Although much is known about whole-limb force generation and activation patterns in fatigued muscles under sustained isometric contractions, little is known about the in vivo dynamics of limb muscle function in relation to whole-body fatigue. Here we show that limb kinematics and contractile function in the lateral (LG) and medial (MG) gastrocnemius of helmeted guineafowl (Numida meleagris) are significantly altered following fatiguing exercise at 2 m s−1 on an inclined treadmill. The two most significant findings were that the variation in muscle force generation, measured directly from the muscles' tendons, increased significantly with fatigue, and fascicle shortening in the proximal MG, but not the distal MG, decreased significantly with fatigue. We suggest that the former is a potential mechanism for decreased stability associated with fatigue. The region-specific alteration of fascicle behaviour within the MG as a result of fatigue suggests a complex response to fatigue that probably depends on muscle–aponeurosis and tendon architecture not previously explored. These findings highlight the importance of studying the integrative in vivo dynamics of muscle function in response to fatigue. PMID:19129096

  5. 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. PMID:18560879

  6. Fatigue strength reduction factors for welds based on nondestructive examination

    SciTech Connect

    Hechmer, J.L.; Kuhn, E.J. III

    1999-02-01

    Based on the author`s hypothesis that nondestructive examination (NDE) has a major role in predicting the fatigue life of pressure vessels, a project was initiated to develop a defined relationship between NDE and fatigue strength reduction factors (FSRF). Even though a relationship should apply to both base metal and weld metal, the project was limited to weld metal because NDE for base metal is reasonably well established, whereas NDE for weld metal is more variable, depending on application. A matrix of FSRF was developed based on weld type (full penetration, partial penetration, and fillet weld) versus the NDE that is applied. The NDE methods that are included are radiographic testing (RT), ultrasonic testing (UT), magnetic particle testing (MT), dye penetrant testing (PT), and visual testing (VT). The first two methods (RT and UT) are volumetric examinations, and the remaining three are surface examinations. Seven combinations of volumetric and surface examinations were defined; thus, seven levels of FSRF are defined. Following the initial development of the project, a PVRC (Pressure Vessel Research Council) grant was obtained for the purpose of having a broad review. The report (Hechmer, 1998) has been accepted by PVRC. This paper presents the final matrix, the basis for the FSRF, and key definitions for accurate application of the FSRF matrix. A substantial amount of additional information is presented in the PVRC report (Hechmer, 1998).

  7. 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.

  8. 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.

  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. 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. PMID:25525208

  11. Fatigue and non-fatigue mathematical muscle models during functional electrical stimulation of paralyzed muscle

    PubMed Central

    Cai, Zhijun; Bai, Er-wei; Shields, Richard K.

    2013-01-01

    Electrical muscle stimulation demonstrates potential for preventing muscle atrophy and for restoring functional movement after spinal cord injury (SCI). Control systems used to optimize delivery of electrical stimulation protocols depend upon the algorithms generated using computational models of paralyzed muscle force output. The Hill-Huxley-type model, while being highly accurate, is also very complex, making it difficult for real-time implementation. In this paper, we propose a Wiener-Hammerstein system to model the paralyzed skeletal muscle under electrical stimulus conditions. The proposed model has substantial advantages in identification algorithm analysis and implementation including computational complexity and convergence, which enable it to be used in real-time model implementation. Experimental data sets from the soleus muscles of fourteen subjects with SCI were collected and tested. The simulation results show that the proposed model outperforms the Hill-Huxley-type model not only in peak force prediction, but also in fitting performance for force output of each individual stimulation train. PMID:23667385

  12. Knee muscle strength in multiple sclerosis: relationship with gait characteristics

    PubMed Central

    Güner, Senem; Hagharı, Sema; Inanıcı, Fatma; Alsancak, Serap; Aytekın, Gokhan

    2015-01-01

    [Purpose] To investigate the relationship between isokinetic knee muscle strength and kinematic, kinetic and spatiotemporal gait parameters of patients with multiple sclerosis (MS). [Subjects and Methods] Twenty-nine MS patients (mean age 31.5±6.5) were investigated in this study. The isokinetic knee muscle strength and gait parameters of MS patients with moderate and severe disability, as determined by the expanded disability status scale (EDSS): EDSS=1–4.5 (n=22, moderate disability) and EDSS>4.5 (n=7, severe disability) were measured. [Results] Isokinetic knee muscle strength, kinematic, kinetic and spatiotemporal gait parameters differed between moderate (EDSS=1–4.5, n=22) and severe disability (EDSS>4.5, n=7). The correlation between each of gait speed, stride length, total range of knee joint movement and the four strength parameters (minimum and maximum quadriceps and hamstring muscle strengths) were significant for the MS group as a whole. Within subgroups, the correlation between minimum hamstring strength and total range of knee movement was significant only in group EDSS>4.5; minimum hamstring correlated with peak knee extensor moment in group EDSS=1–4.5, but at a reduced level of significance. [Conclusion] The present study revealed significant correlations between gait characteristics and isokinetic strength parameters of the quadriceps and hamstring muscles. Our study suggests that rehabilitation protocols for MS patients should include a critical strength training programme particularly for the hamstring and quadriceps muscles. PMID:25931736

  13. 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.

  14. Effects of stimulation frequency versus pulse duration modulation on muscle fatigue

    PubMed Central

    Kesar, Trisha; Chou, Li-Wei; Binder-Macleod, Stuart A.

    2008-01-01

    During functional electrical stimulation (FES), both the frequency and intensity can be increased to increase muscle force output and counteract the effects of muscle fatigue. Most current FES systems, however, deliver a constant frequency and only vary the stimulation intensity to control muscle force. This study compared muscle performance and fatigue produced during repetitive electrical stimulation using three different strategies: (1) constant pulse-duration and stepwise increases in frequency (frequency-modulation); (2) constant frequency and stepwise increases in pulse-duration (pulse-duration-modulation); and (3) constant frequency and pulse-duration (no-modulation). Surface electrical stimulation was delivered to the quadriceps femoris muscles of 12 healthy individuals and isometric forces were recorded. Muscle performance was assessed by measuring the percent changes in the peak forces and force–time integrals between the first and the last fatiguing trains. Muscle fatigue was assessed by measuring percent declines in peak force between the 60 Hz pre- and post-fatigue testing trains. The results showed that frequency-modulation showed better performance for both peak forces and force–time integrals in response to the fatiguing trains than pulse-duration-modulation, while producing similar levels of muscle fatigue. Although frequency-modulation is not commonly used during FES, clinicians should consider this strategy to improve muscle performance. PMID:17317219

  15. 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.

  16. 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

  17. Quadriceps and Respiratory Muscle Fatigue Following High-Intensity Cycling in COPD Patients

    PubMed Central

    Bachasson, Damien; Wuyam, Bernard; Pepin, Jean-Louis; Tamisier, Renaud; Levy, Patrick; Verges, Samuel

    2013-01-01

    Exercise intolerance in COPD seems to combine abnormal ventilatory mechanics, impaired O2 transport and skeletal muscle dysfunction. However their relatie contribution and their influence on symptoms reported by patients remain to be clarified. In order to clarify the complex interaction between ventilatory and neuromuscular exercise limiting factors and symptoms, we evaluated respiratory muscles and quadriceps contractile fatigue, dynamic hyperinflation and symptoms induced by exhaustive high-intensity cycling in COPD patients. Fifteen gold II-III COPD patients (age = 67±6 yr; BMI = 26.6±4.2 kg.m-2) performed constant-load cycling test at 80% of their peak workload until exhaustion (9.3±2.4 min). Before exercise and at exhaustion, potentiated twitch quadriceps strength (Qtw), transdiaphragmatic (Pdi,tw) and gastric (Pga,tw) pressures were evoked by femoral nerve, cervical and thoracic magnetic stimulation, respectively. Changes in operational lung volumes during exercise were assessed via repetitive inspiratory capacity (IC) measurements. Dyspnoea and leg discomfort were measured on visual analog scale. At exhaustion, Qtw (-33±15%, >15% reduction observed in all patients but two) and Pdi,tw (-20±15%, >15% reduction in 6 patients) were significantly reduced (P<0.05) but not Pga,tw (-6±10%, >15% reduction in 3 patients). Percentage reduction in Qtw correlated with the percentage reduction in Pdi,tw (r=0.66; P<0.05). Percentage reductions in Pdi,tw and Pga,tw negatively correlated with the reduction in IC at exhaustion (r=-0.56 and r=-0.62, respectively; P<0.05). Neither dyspnea nor leg discomfort correlated with the amount of muscle fatigue. In conclusion, high-intensity exercise induces quadriceps, diaphragm and less frequently abdominal contractile fatigue in this group of COPD patients. In addition, the rise in end-expiratory lung volume and diaphragm flattening associated with dynamic hyperinflation in COPD might limit the development of abdominal and

  18. Quadriceps and respiratory muscle fatigue following high-intensity cycling in COPD patients.

    PubMed

    Bachasson, Damien; Wuyam, Bernard; Pepin, Jean-Louis; Tamisier, Renaud; Levy, Patrick; Verges, Samuel

    2013-01-01

    Exercise intolerance in COPD seems to combine abnormal ventilatory mechanics, impaired O2 transport and skeletal muscle dysfunction. However their relative contribution and their influence on symptoms reported by patients remain to be clarified. In order to clarify the complex interaction between ventilatory and neuromuscular exercise limiting factors and symptoms, we evaluated respiratory muscles and quadriceps contractile fatigue, dynamic hyperinflation and symptoms induced by exhaustive high-intensity cycling in COPD patients. Fifteen gold II-III COPD patients (age = 67 ± 6 yr; BMI = 26.6 ± 4.2 kg.m(-2)) performed constant-load cycling test at 80% of their peak workload until exhaustion (9.3 ± 2.4 min). Before exercise and at exhaustion, potentiated twitch quadriceps strength (Q(tw)), transdiaphragmatic (P(di,tw)) and gastric (P(ga,tw)) pressures were evoked by femoral nerve, cervical and thoracic magnetic stimulation, respectively. Changes in operational lung volumes during exercise were assessed via repetitive inspiratory capacity (IC) measurements. Dyspnoea and leg discomfort were measured on visual analog scale. At exhaustion, Q(tw) (-33 ± 15%, >15% reduction observed in all patients but two) and Pdi,tw (-20 ± 15%, >15% reduction in 6 patients) were significantly reduced (P<0.05) but not Pga,tw (-6 ± 10%, >15% reduction in 3 patients). Percentage reduction in Q(tw) correlated with the percentage reduction in P(di,tw) (r = 0.66; P<0.05). Percentage reductions in P(di,tw) and P(ga,tw) negatively correlated with the reduction in IC at exhaustion (r = -0.56 and r = -0.62, respectively; P<0.05). Neither dyspnea nor leg discomfort correlated with the amount of muscle fatigue. In conclusion, high-intensity exercise induces quadriceps, diaphragm and less frequently abdominal contractile fatigue in this group of COPD patients. In addition, the rise in end-expiratory lung volume and diaphragm flattening associated with dynamic hyperinflation in COPD might limit

  19. 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. PMID:25764064

  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. 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.

  2. Arginylation of myosin heavy chain regulates skeletal muscle strength

    PubMed Central

    Cornachione, Anabelle S.; Leite, Felipe S.; Wang, Junling; Leu, Nicolae A.; Kalganov, Albert; Volgin, Denys; Han, Xuemei; Xu, Tao; Cheng, Yu-Shu; Yates, John R. R.; Rassier, Dilson E.; Kashina, Anna

    2014-01-01

    Protein arginylation is a post-translational modification with an emerging global role in the regulation of actin cytoskeleton. To test the role of arginylation in the skeletal muscle, we generated a mouse model with Ate1 knockout driven by skeletal muscle-specific creatine kinase (Ckmm) promoter. Such Ckmm-Ate1 mice were viable and outwardly normal, however their skeletal muscle strength was significantly reduced compared to the control. Mass spectrometry of the isolated skeletal myofibrils showed a limited set of proteins arginylated on specific sites, including myosin heavy chain. Atomic force microscopy measurements of the contractile strength in individual myofibrils and isolated myosin filaments from these mice showed a significant reduction of contractile forces, which, in the case of the myosin filaments could be fully rescued by re-arginylation with purified Ate1. Our results demonstrate that arginylation regulates force production in the muscle and exerts a direct effect on muscle strength through arginylation of myosin. PMID:25017061

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

    PubMed

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

    2016-06-01

    The objective of this study was to supplement continuous wavelet transforms with muscle synergies in a fatigue analysis to better describe the combination of decreased firing frequency and altered activation profiles during dynamic muscle contractions. Nine healthy young individuals completed the dynamic tasks before and after they squatted with a standard Olympic bar until complete exhaustion. Electromyography (EMG) profiles were analyzed with a novel concatenated non-negative matrix factorization method that decomposed EMG signals into muscle synergies. Muscle synergy analysis provides the activation pattern of the muscles while continuous wavelet transforms output the temporal frequency content of the EMG signals. Synergy analysis revealed subtle changes in two-legged squatting after fatigue while differences in one-legged squatting were more pronounced and included the shift from a general co-activation of muscles in the pre-fatigue state to a knee extensor dominant weighting post-fatigue. Continuous wavelet transforms showed major frequency content decreases in two-legged squatting after fatigue while very few frequency changes occurred in one-legged squatting. It was observed that the combination of methods is an effective way of describing muscle fatigue and that muscle activation patterns play a very important role in maintaining the overall joint kinetics after fatigue. PMID:27156237

  4. Relaxation rate in the assessment of masseter muscle fatigue.

    PubMed

    Lyons, M F; Aggarwal, A

    2001-02-01

    The aim of this study was to assess a simple method of measuring relaxation rate in the jaw-closing system for the purpose of quantifying jaw muscle fatigue. A summary of the various different methods of measuring relaxation rate is also provided. The rates of twitch contraction and relaxation were measured in 30 symptom-free subjects following bilateral direct electrical stimulation of the masseter muscles. The resulting twitch force was recorded via a force transducer placed between the anterior teeth. The transducer was held between the teeth with as little force as possible while four single stimuli were delivered at 5-s intervals. The stimulating electrodes were then removed and replaced and the experiment was repeated. The force records of the resulting twitches were averaged and the half-contraction time, twitch amplitude and half-relaxation time were measured. There was a significant difference in half-relaxation time between males and females, being faster in females (P=0.0045, independent t-test). No significant difference was found in twitch amplitude and half-contraction time between males and females. Half-relaxation time and half-contraction time were independent of twitch amplitude. This method of measuring the relaxation rate of the masseter muscles was found to be practical and the results were reproducible between sessions. PMID:11298267

  5. [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. PMID:26710452

  6. Assessment of Bending Fatigue Strength of Crankshaft Sections with Consideration of Quenching Residual Stress

    NASA Astrophysics Data System (ADS)

    Qin, W. J.; Dong, C.; Li, X.

    2016-03-01

    High-cycle bending fatigue is the primary failure mode of crankshafts in engines. Compressive residual stresses are often introduced by induction quenching to improve the fatigue strength of crankshafts. The residual stresses, which are commonly obtained by numerical methods, such as the finite element method (FEM), should be included in fatigue failure analysis to predict the fatigue strength of crankshafts accurately. In this study, the simulation method and theory of quenching process are presented and applied to investigate the residual stresses of a diesel engine crankshaft. The coupling calculation of temperature, microstructure, and stress fields of the crankshaft section is conducted by FEM. Then, the fatigue strength of the crankshaft section is analytically assessed by Susmel and Lazzarin's criterion based on the critical plane approach that superimposes the residual stresses onto the bending stresses. The resonant bending fatigue tests of the crankshaft sections are conducted, and the tests and analytical assessments yield consistent results.

  7. Hormone Therapy and Skeletal Muscle Strength: A Meta-Analysis

    PubMed Central

    Greising, Sarah M.; Baltgalvis, Kristen A.; Warren, Gordon L.

    2009-01-01

    Background Our objective was to perform a systematic review and meta-analysis of the research literature that compared muscle strength in postmenopausal women who were and were not on estrogen-based hormone therapy (HT). Methods Twenty-three relevant studies were found. Effect sizes (ESs) were calculated as the standardized mean difference, and meta-analyses were completed using a random effects model. Results HT was found to result in a small beneficial effect on muscle strength in postmenopausal women (overall ES = 0.23; p = .003) that equated to an ∼5% greater strength for women on HT. Among the 23 studies, various muscle groups were assessed for strength, and those that benefitted the most were the thumb adductors (ES = 1.14; p < .001). Ten studies that compared muscle strength in rodents that were and were not estradiol deficient were also analyzed. The ES for absolute strength was moderate but not statistically significant (ES = 0.44; p = .12), whereas estradiol had a large effect on strength normalized to muscle size (ES = 0.66; p = .03). Conclusion Overall, estrogen-based treatments were found to beneficially affect strength. PMID:19561145

  8. 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

  9. The effectiveness of FES-evoked EMG potentials to assess muscle force and fatigue in individuals with spinal cord injury.

    PubMed

    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

  10. An Autonomous Wearable System for Predicting and Detecting 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 clinically investigated in order to fully understand the condition. This paper demonstrates a non-invasive technique used to automate the fatigue detection and prediction process. The system utilises the clinical aspects such as kinematics and surface electromyography (sEMG) of an athlete during isometric contractions. Various signal analysis methods are used illustrating their applicability in real-time settings. This demonstrated system can be used in sports scenarios to promote muscle growth/performance or prevent injury. To date, research on localised muscle fatigue focuses on the clinical side and lacks the implementation for detecting/predicting localised muscle fatigue using an autonomous system. Results show that automating the process of localised muscle fatigue detection/prediction is promising. The autonomous fatigue system was tested on five individuals showing 90.37% accuracy on average of correct classification and an error of 4.35% in predicting the time to when fatigue will onset. PMID:22319367

  11. Effects of Kinesio taping on scapular kinematics of overhead athletes following muscle fatigue.

    PubMed

    Zanca, Gisele Garcia; Grüninger, Bruno; Mattiello, Stela Márcia

    2016-08-01

    Scapular kinematics alterations have been found following muscle fatigue. Considering the importance of the lower trapezius in coordinated scapular movement, this study aimed to investigate the effects of elastic taping (Kinesio taping, KT) for muscle facilitation on scapular kinematics of healthy overhead athletes following muscle fatigue. Twenty-eight athletes were evaluated in a crossover, single-blind, randomized design, in three sessions: control (no taping), KT (KT with tension) and sham (KT without tension). Scapular tridimensional kinematics and EMG of clavicular and acromial portions of upper trapezius, lower trapezius and serratus anterior were evaluated during arm elevation and lowering, before and after a fatigue protocol involving repetitive throwing. Median power frequency decline of serratus anterior was significantly lower in KT session compared to sham, possibly indicating lower muscle fatigue. However, the effects of muscle fatigue on scapular kinematics were not altered by taping conditions. Although significant changes were found in scapular kinematics following muscle fatigue, they were small and not considered relevant. It was concluded that healthy overhead athletes seem to present an adaptive mechanism that avoids the disruption of scapular movement pattern following muscle fatigue. Therefore, these athletes do not benefit from the use of KT to assist scapular movement under the conditions tested. PMID:26149961

  12. Fatigue strength of Ce-TZP/Al2O3 nanocomposite with different surfaces.

    PubMed

    Takano, T; Tasaka, A; Yoshinari, M; Sakurai, K

    2012-08-01

    Ce-TZP/Al(2)O(3) nanocomposite (NANOZR) has not only higher strength, but also higher fracture toughness than conventional Y-TZP, indicating its potential for use in dental implants. Surface treatment to obtain osseointegration, however, may alter its surface topography, thus affecting the cyclic fatigue strength that plays such an important role in the durability of this material. The aim of this study was to evaluate the influence of surface treatment on cyclic fatigue strength in NANOZR as compared with grit-blasted and acid-etched Y-TZP (125BE Y-TZP). Bi-axial flexure strength was measured in both static and cyclic fatigue tests, as recommended by ISO 6872. The cyclic fatigue test was performed by the staircase method in distilled water at 37°C, with a load of 10(6) cycles and 10 Hz. Bi-axial flexure strength of NANOZR was 1111-1237 MPa and 667-881 MPa in the static and cyclic fatigue tests, respectively. The bi-axial flexure strength of NANOZR under all conditions was greater than that of 125BE Y-TZP in the static and cyclic fatigue tests. The cyclic fatigue strength of NANOZR was more than twice that of Y-TZP as specified in ISO 13356 for surgical implants (320 MPa), indicating the promise of this material for use in dental implants. PMID:22736446

  13. 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.

  14. 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…

  15. Evaluation of surgeon’s muscle fatigue during thoracoscopic pulmonary lobectomy using interoperative surface electromyography

    PubMed Central

    Yoon, Seung-Hyun; Jung, Myung-Chul

    2016-01-01

    Background The aim of this study was to document the physical stress experienced by a surgeon during thoracoscopic pulmonary lobectomy and mediastinal lymph node dissection for lung cancer by measuring the intraoperative electromyography (EMG). Methods Surface EMG was recorded during 12 cases of thoracoscopic lobectomy. During the operation, 16 channels of a wireless EMG were used to measure muscle activity and fatigue from the bilateral muscles of the splenius capitis (SC), upper trapezius (UT), middle deltoid (MD), flexor carpi radialis (FCR), extensor carpi radialis (ECR), lumbar erector spinae (LES), rectus femoralis (RF), and tibialis anterior (TA). The EMG signals were processed to collect the values of the root mean square for muscle activity and median frequency (MF) for muscle fatigue. Results All operations were completed without adverse events. The mean operating time was 99.16±35.15 minutes. During the operation, the mean muscle activity of all muscles was 21.91±12.85 mV. High muscle activity was observed in the bilateral FCR and ECR, whereas low muscle activity was observed in the bilateral SC and LES. The final MFs in the bilateral SC and LES were found to be decreased from the initial status, which implied increased muscle fatigue. The muscles of the right and left LES were significantly fatigued by up to 29% and 37% compared to their initial status (P=0.021 and P=0.007, respectively). The MFs of the bilateral LES decreased with time (an average decreases of 0.008/5 minutes, P=0.002 in right LES and 0.004/5 minutes, P=0.018 in left LES). Conclusions During thoracoscopic lobectomy, muscle fatigue was observed in muscles related to a static posture, such as the bilateral SC, UT, and ES. Further studies are required to investigate the ergonomic adjustments needed to reduce muscle fatigue in these static muscles. PMID:27293833

  16. Fatigue crack retardation of high strength steel in saltwater

    SciTech Connect

    Tokaji, K.; Ando, Z.; Imai, T.; Kojima, T.

    1983-04-01

    A high strength steel was studied in 3 percent saltwater to investigate the effects of a corrosive environment and sheer thickness on fatigue crack propagation behavior following the application of a single tensile overload. Experiments were carried out under sinusoidally varying loads at a load ratio of 0 and frequency of 10 H /SUB z/ . A single tensile overload was found to cause delayed retardation, and the crack propagation rate at first increased, followed by fairly rapid decrease to a minimum value and then increased gradually to its steady-state value, just as it did in air. The overload affected zone size and the retardation cycles increased with decreasing sheet thickness, just as they did in air. However, the zone size and the cycles were larger in 3 percent saltwater than in air. Since the crack propagation rates through the overload affected zone were not affected by the test environment, the longer retardation cycles in 3 percent saltwater were attributed to an enlargement of the overload affected zone size. The crack propagation behavior following the application of a single tensile overload in 3 percent saltwater was well explained by the crack closure concept.

  17. Muscle Activation and Performance During Trunk Strength Testing in High-Level Female and Male Football Players.

    PubMed

    Roth, Ralf; Donath, Lars; Zahner, Lukas; Faude, Oliver

    2016-06-01

    For performance and injury prevention in sport, core strength and endurance are focused prerequisites. Therefore we evaluated characteristics of trunk muscle activation and performance during strength-endurance related trunk field tests. Strength-endurance ability, as total time to failure, and activation of trunk muscles was measured in 39 football players of the highest German female football league (Bundesliga) (N = 18, age: 20.7 y [SD 4.4]) and the highest national male under-19 league (N = 21, age: 17.9 y [0.7]) in prone plank, side plank, and dorsal position. Maximal isometric force was assessed during trunk extension and flexion, rotation, and lateral flexion to normalize EMG and to compare with the results of strength-endurance tests. For all positions of endurance strength tests, a continuous increase in normalized EMG activation was observed (P < .001). Muscle activation of the rectus abdominis and external oblique in prone plank position exceeded the maximal voluntary isometric contraction activation, with a significantly higher activation in females (P = .02). We conclude, that in the applied strength-endurance testing, the activation of trunk muscles was high, especially in females. As high trunk muscle activation can infer fatigue, limb strength can limit performance in prone and side plank position, particularly during high trunk muscle activation. PMID:26671894

  18. 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

  19. Muscle strength and golf performance: a critical review.

    PubMed

    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

  20. 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

  1. 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

  2. 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

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

    PubMed

    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 10(7) 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

  4. 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.

  5. 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. PMID:25873780

  6. Compressive Strength of Notched Poly(Phenylene Sulfide) Aerospace Composite: Influence of Fatigue and Environment

    NASA Astrophysics Data System (ADS)

    Niitsu, G. T.; Lopes, C. M. A.

    2013-08-01

    The purpose of this work is to evaluate the influences of fatigue and environmental conditions (-55 °C, 23 °C, and 82 °C/Wet) on the ultimate compression strength of notched carbon-fiber-reinforced poly(phenylene sulfide) composites by performing open-hole compression (OHC) tests. Analysis of the fatigue effect showed that at temperatures of -55 and 23 °C, the ultimate OHC strengths were higher for fatigued than for not-fatigued specimens; this could be attributed to fiber splitting and delamination during fatigue cycling, which reduces the stress concentration at the hole edge, thus increasing the composite strength. This effect of increasing strength for fatigued specimens was not observed under the 82 °C/Wet conditions, since the test temperature near the matrix glass transition temperature ( T g) together with moisture content resulted in matrix softening, suggesting a reduction in fiber splitting during cycling; similar OHC strengths were verified for fatigued and not-fatigued specimens tested at 82 °C/Wet. Analysis of the temperature effect showed that the ultimate OHC strengths decreased with increasing temperature. A high temperature together with moisture content (82 °C/Wet condition) reduced the composite compressive strengths, since a temperature close to the matrix T g resulted in matrix softening, which reduced the lateral support provided by the resin to the 0° fibers, leading to fiber instability failure at reduced applied loads. On the other hand, a low temperature (-55 °C) improved the compressive strength because of possible fiber-matrix interfacial strengthening, increasing the fiber contribution to compressive strength.

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

    PubMed Central

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

    2005-01-01

    Background 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. Results 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. Conclusion These data indicate that the characteristic fatigue resistance of the extraocular muscles does not depend on CK activity. PMID:16107216

  8. 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.

  9. Muscle activity, time to fatigue, and maximum task duration at different levels of production standard time

    PubMed Central

    Nur, Nurhayati Mohd; Dawal, Siti Zawiah Md; Dahari, Mahidzal; Sanusi, Junedah

    2015-01-01

    [Purpose] This study investigated the variations in muscle fatigue, time to fatigue, and maximum task duration at different levels of production standard time. [Methods] Twenty subjects performed repetitive tasks at three different levels of production standard time corresponding to “normal”, “hard” and “very hard”. Surface electromyography was used to measure the muscle activity. [Results] The results showed that muscle activity was significantly affected by the production standard time level. Muscle activity increased twice in percentage as the production standard time shifted from hard to very hard (6.9% vs. 12.9%). The muscle activity increased over time, indicating muscle fatigue. The muscle fatigue rate increased for the harder production standard time (Hard: 0.105; Very hard: 0.115), which indicated the associated higher risk of work-related musculoskeletal disorders. Muscle fatigue was also found to occur earlier for hard and very hard production standard times. [Conclusion] It is recommended that the maximum task duration should not exceed 5.6, 2.9, and 2.2 hours for normal, hard, and very hard production standard times, respectively, in order to maintain work performance and minimize the risk of work-related musculoskeletal disorders. PMID:26311974

  10. Muscle fatigue increases beta-band coherence between the firing times of simultaneously active motor units in the first dorsal interosseous muscle.

    PubMed

    McManus, Lara; Hu, Xiaogang; Rymer, William Z; Suresh, Nina L; Lowery, Madeleine M

    2016-06-01

    Synchronization between the firing times of simultaneously active motor units (MUs) is generally assumed to increase during fatiguing contractions. To date, however, estimates of MU synchronization have relied on indirect measures, derived from surface electromyographic (EMG) interference signals. This study used intramuscular coherence to investigate the correlation between MU discharges in the first dorsal interosseous muscle during and immediately following a submaximal fatiguing contraction, and after rest. Coherence between composite MU spike trains, derived from decomposed surface EMG, were examined in the delta (1-4 Hz), alpha (8-12 Hz), beta (15-30 Hz), and gamma (30-60 Hz) frequency band ranges. A significant increase in MU coherence was observed in the delta, alpha, and beta frequency bands postfatigue. In addition, wavelet coherence revealed a tendency for delta-, alpha-, and beta-band coherence to increase during the fatiguing contraction, with subjects exhibiting low initial coherence values displaying the greatest relative increase. This was accompanied by an increase in MU short-term synchronization and a decline in mean firing rate of the majority of MUs detected during the sustained contraction. A model of the motoneuron pool and surface EMG was used to investigate factors influencing the coherence estimate. Simulation results indicated that changes in motoneuron inhibition and firing rates alone could not directly account for increased beta-band coherence postfatigue. The observed increase is, therefore, more likely to arise from an increase in the strength of correlated inputs to MUs as the muscle fatigues. PMID:26984420

  11. 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

  12. 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

  13. 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

  14. Classifying Lower Extremity Muscle Fatigue during Walking using Machine Learning and Inertial Sensors

    PubMed Central

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

    2013-01-01

    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 (SVM) 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. PMID:24081829

  15. 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. PMID:26331671

  16. Fatigue failure of hydrogen embrittled high strength steels

    NASA Technical Reports Server (NTRS)

    Kim, Y. G.; Aleszka, J.

    1975-01-01

    Results of an experimental investigation are presented concerning the fracture behavior of cathodically charged, quenched and tempered martensitic steels under cyclic load conditions. Introduction of H2 by cathodic charging reduced fatigue life by as much as 60%. It is proposed that subsurface transverse fatigue cracks nucleate simultaneously at multiple sites, such as at microcracks, voids, or inclusions. Fatigue crack growth then occurs on planes perpendicular to the major applied stress axis in the presence of the critical combination of applied external stress and hydrogen.

  17. 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.

  18. Cycle time influences the development of muscle fatigue at low to moderate levels of intermittent muscle contraction.

    PubMed

    Rashedi, Ehsan; Nussbaum, Maury A

    2016-06-01

    Localized muscle fatigue (LMF) during a repetitive task can be influenced by several aspects such as the level and duration of exertions. Among these aspects, though, the influence of cycle time remains unclear. Here, the effect of cycle time on LMF and performance was examined for a simple biomechanical system during repetitive static efforts. Participants performed 1-h trials of intermittent isometric index finger abduction with a duty cycle of 50% in all combinations of two cycle times (30 and 60s) and two exertion levels (15% and 25% of maximum voluntary capacity). Measures of discomfort, performance (force fluctuations), and muscle capacity (voluntary strength and low-frequency twitch responses) were obtained, all of which demonstrated a beneficial effect of the 30s cycle time. Specifically, the shorter cycle time led to lower rates of increase in perceived discomfort, lower rates of increase in force fluctuations, lower rates of decrease in voluntary capacity, and smaller changes in twitch responses. These benefits, reflecting less LMF development in the shorter cycle time, were quite consistent between genders and the two levels of effort. Results of this study can be used to modify current models predicting work-rest allowance and/or LMF, helping to enhance performance and reduce the risk of adverse musculoskeletal outcomes. PMID:26995711

  19. 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

  20. Thigh Muscle Strength in Senior Athletes and Healthy Controls

    PubMed Central

    McCrory, Jean L; Salacinski, Amanda J; Hunt, Sarah E; Greenspan, Susan L

    2016-01-01

    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 × gender × 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. PMID:19972628

  1. 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.

  2. 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.

  3. 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

  4. 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. PMID:27195511

  5. Isometric Arm Strength and Subjective Rating of Upper Limb Fatigue in Two-Handed Carrying Tasks

    PubMed Central

    Li, Kai Way; Chiu, Wen-Sheng

    2015-01-01

    Sustained carrying could result in muscular fatigue of the upper limb. Ten male and ten female subjects were recruited for measurements of isometric arm strength before and during carrying a load for a period of 4 minutes. Two levels of load of carrying were tested for each of the male and female subjects. Exponential function based predictive equations for the isometric arm strength were established. The mean absolute deviations of these models in predicting the isometric arm strength were in the range of 3.24 to 17.34 N. Regression analyses between the subjective ratings of upper limb fatigue and force change index (FCI) for the carrying were also performed. The results indicated that the subjective rating of muscular fatigue may be estimated by multiplying the FCI with a constant. The FCI may, therefore, be adopted as an index to assess muscular fatigue for two-handed carrying tasks. PMID:25794159

  6. 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.

  7. 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. PMID:16023345

  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 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

  9. 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. PMID:24356522

  10. 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. PMID:26705066

  11. The Development of Muscle Fatigue Suppresses Auditory Sensory Gating (P50) during Sustained Contraction

    PubMed Central

    Aleksandrov, Aleksander A.; Dmitrieva, Elena S.; Stankevich, Ludmila N.; Knyazeva, Veronika M.; Shestakova, Anna N.

    2016-01-01

    Our aim was to study the influence of fatigue development on sensory gating during a muscle load. The fatiguing task was sustained contraction of a handgrip dynamometer with 7 and 30% maximum voluntary contraction (MVC). The suppression of P50, an auditory event-related potential, was used as the sensory gating index in the paired-click paradigm with a 500 ms interstimulus interval; the difference between the P50 amplitudes of the first and the second stimuli of the pair was used as the sensory gating index. We found that the 30% MVC fatigue development strongly decreased sensory gating, sometimes totally suppressing it. We concluded that central fatigue impaired motor performance and strongly suppressed inhibitory processes, as shown by the decreased P50 amplitude to the second stimulus. Therefore, muscle central fatigue influences sensory gating, similar to schizophrenia spectrum disorders. PMID:27458348

  12. Effects of weld defects at root on rotating bending fatigue strength of small diameter socket welded pipe joints

    SciTech Connect

    Higuchi, Makoto; Nakagawa, Akira; Chujo, Noriyuki; Iida, Kunihiro; Matsuda, Fukuhisa; Sato, Masanobu

    1996-12-01

    Rotating bending fatigue tests were conducted on socket welded joints of a nominal diameter 20 mm, and effects of root defect and other various factors, including post-weld heat treatment (PWHT), pipe wall thickness, and socket wall thickness, were investigated. The socket joints exhibited, in the rotating bending fatigue mode, fatigue strengths that were markedly lower than the same 20 mm diameter joints in four-point bending fatigue. Also, where the latter specimens failed always at the toe, root-failures occurred in rotating bending fatigue. When PWHT`d, however, the fatigue strength showed a remarkable improvement, while the failure site reverted to toe. Thicker pipe walls and socket walls gave rise to higher fatigue strength. A formula relating the size of root defects to the fatigue strength reduction has been proposed.

  13. 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

  14. 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

  15. Overexpression of antioxidant enzymes in diaphragm muscle does not alter contraction-induced fatigue or recovery.

    PubMed

    McClung, Joseph M; Deruisseau, Keith C; Whidden, Melissa A; Van Remmen, Holly; Richardson, Arlan; Song, Wook; Vrabas, Ioannis S; Powers, Scott K

    2010-01-01

    Low levels of reactive oxygen species (ROS) production are necessary to optimize muscle force production in unfatigued muscle. In contrast, sustained high levels of ROS production have been linked to impaired muscle force production and contraction-induced skeletal muscle fatigue. Using genetically engineered mice, we tested the hypothesis that the independent transgenic overexpression of catalase (CAT), copper/zinc superoxide dismutase (CuZnSOD; SOD1) or manganese superoxide dismutase (MnSOD; SOD2) antioxidant enzymes would negatively affect force production in unfatigued diaphragm muscle but would delay the development of muscle fatigue and enhance force recovery after fatiguing contractions. Diaphragm muscle from wild-type littermates (WT) and from CAT, SOD1 and SOD2 overexpressing mice were subjected to an in vitro contractile protocol to investigate the force-frequency characteristics, the fatigue properties and the time course of recovery from fatigue. The CAT, SOD1 and SOD2 overexpressors produced less specific force (in N cm(-2)) at stimulation frequencies of 20-300 Hz and produced lower maximal tetanic force than WT littermates. The relative development of muscle fatigue and recovery from fatigue were not influenced by transgenic overexpression of any antioxidant enzyme. Morphologically, the mean cross-sectional area (in microm(2)) of diaphragm myofibres expressing myosin heavy chain type IIA was decreased in both CAT and SOD2 transgenic animals, and the percentage of non-contractile tissue increased in diaphragms from all transgenic mice. In conclusion, our results do not support the hypothesis that overexpression of independent antioxidant enzymes protects diaphragm muscle from contraction-induced fatigue or improves recovery from fatigue. Moreover, our data are consistent with the concept that a basal level of ROS is important to optimize muscle force production, since transgenic overexpression of major cellular antioxidants is associated with

  16. 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. PMID:26614974

  17. Differential activation of myofibrils during fatigue in phasic skeletal muscle cells.

    PubMed

    Garcia, M C; Gonzalez-Serratos, H; Morgan, J P; Perreault, C L; Rozycka, M

    1991-10-01

    In fatigued muscles the T-system is swollen; thus the action potential may fail to travel along the T-system or the T-tubule terminal cisternae signal may fail to bring about TC Ca2+ release. This would lead to a decrease in the number of myofibrils activated and in force development, but if fatigue is the result of a generalized process, all the myofibrils would be affected equally leading to a lower activation of all of them. We have investigated this possibility in isolated twitch muscle fibres by giving them repetitive tetanic stimulations until fatigue developed. The behaviour of myofibrils was followed with cinemicrophotography. Before fatigue, no lack of shortening of myofibrils could be found. During fatigue groups of myofibrils became wavy. When exposed to caffeine, the wavy myofibrils disappeared and tension similar to the control developed. The tension-caffeine concentration relationship was shifted to the left after development of fatigue. In low Na+ solution fatigue developed faster and after reintroducing normal Ringer, tension recovered substantially. K-contractures were smaller during fatigue. These results indicate that in this type of fatigue, a step in the EC coupling chain of events is involved in its development. PMID:1939605

  18. 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

  19. Detection of skeletal muscle fatigue in patients with heart failure using electromyography.

    PubMed

    Wilson, J R; Mancini, D M; Simson, M

    1992-08-15

    Patients with heart failure frequently report that leg fatigue limits maximal exercise capacity. However, objective documentation of muscle fatigue has not been obtained in such patients. In normal subjects, muscle fatigue during constant work load exercise is associated with an increase in electrical activity generated per contraction due to use of additional muscle fibers to compensate for fiber fatigue. The present study was performed to determine if this approach can be used to document muscle fatigue in patients with heart failure. Vastus lateralis surface electromyograms were monitored in 8 ambulatory patients with nonedematous heart failure and 6 normal subjects during maximal bicycle exercise (20 W increments every 2 minutes). The electromyogram was stored on tape and subsequently analyzed for integrated root-mean-square voltage/contraction (iRMSV). At each work load, the iRMSV of the first and last 30 seconds of the work load were compared. The maximal work load achieved by patients with heart failure was significantly lower (73 +/- 22 W) than that by normal subjects (150 +/- 15 W; p less than 0.01). Both groups had no significant difference between the initial and final iRMSV at submaximal work loads. However, during the 2 highest work loads, both groups reported leg fatigue and had significant increases in iRMSV, consistent with muscle fiber fatigue (maximal work load: 259 +/- 59 to 279 +/- 58 mv.ms [normals] vs 258 +/- 94 to 283 +/- 93 mv.ms [heart failure]; p less than 0.03). The data indicate that the surface electromyogram can be used to detect skeletal muscle fatigue in patients with heart failure.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1642187

  20. The Pilates Method increases respiratory muscle strength and performance as well as abdominal muscle thickness.

    PubMed

    Giacomini, Mateus Beltrame; da Silva, Antônio Marcos Vargas; Weber, Laura Menezes; Monteiro, Mariane Borba

    2016-04-01

    The aim of this study was to verify the effects of the Pilates Method (PM) training program on the thickness of the abdominal wall muscles, respiratory muscle strength and performance, and lung function. This uncontrolled clinical trial involved 16 sedentary women who were assessed before and after eight weeks of PM training. The thickness of the transversus abdominis (TrA), internal oblique (IO) and external oblique (EO) muscles was assessed. The respiratory muscle strength was assessed by measuring the maximum inspiratory (MIP) and expiratory (MEP) pressure. The lung function and respiratory muscle performance were assessed by spirometry. An increase was found in MIP (p = 0.001), MEP (p = 0.031), maximum voluntary ventilation (p = 0.020) and the TrA (p < 0.001), IO (p = 0.002) and EO (p < 0.001) thickness after the PM program. No alterations in lung function were found. These findings suggest that the PM program promotes abdominal wall muscle hypertrophy and an increase in respiratory muscle strength and performance, preventing weakness in abdominal muscles and dysfunction in ventilatory mechanics, which could favor the appearance of illnesses. PMID:27210841

  1. Fatigue detection in strength training using three-dimensional accelerometry and principal component analysis.

    PubMed

    Brown, Niklas; Bichler, Sebastian; Fiedler, Meike; Alt, Wilfried

    2016-06-01

    Detection of neuro-muscular fatigue in strength training is difficult, due to missing criterion measures and the complexity of fatigue. Thus, a variety of methods are used to determine fatigue. The aim of this study was to use a principal component analysis (PCA) on a multifactorial data-set based on kinematic measurements to determine fatigue. Twenty participants (strength training experienced, 60% male) executed 3 sets of 3 exercises with 50 (12 repetitions), 75 (12 repetitions) and 100%-12 RM (RM). Data were collected with a 3D accelerometer and analysed by a newly developed algorithm to evaluate parameters for each repetition. A PCA with six variables was carried out on the results. A fatigue factor was computed based on the loadings on the first component. One-way ANOVA with Bonferroni post hoc analysis was calculated to test for differences between the intensity levels. All six input variables had high loadings on the first component. The ANOVA showed a significant difference between intensities (p < 0.001). Post-hoc analysis revealed a difference between 100% and the lower intensities (p < 0.05) and no difference between 50 and 75%-12RM. Based on these results, it is possible to distinguish between fatigued and non-fatigued sets of strength training. PMID:27111008

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. Changes in Muscle Activity and Kinematics of Highly Trained Cyclists During Fatigue

    PubMed Central

    Dingwell, Jonathan B.; Joubert, Jason E.; Diefenthaeler, Fernando; Trinity, Joel D.

    2010-01-01

    Muscle fatigue may alter kinematics and contribute to repetitive strain injuries. This study quantified how both localized muscle fatigue and movement kinematics change over time during exhaustive cycling. Seven highly trained cyclists rode a stationary bicycle ergometer at 100% of their VO2max until voluntary exhaustion. Cycling kinematics and EMG activity from select lower extremity muscles were recorded. Cross-correlations were computed to quantify how EMG median frequencies (MDF) changed with changes in movement kinematics. All athletes maintained both cadence and power output for ~90% of the trial duration. Significant sustained muscle fatigue occurred in 18 of 28 muscles tested, most prominently in the biceps femoris (p = 0.020) and gastrocnemius (p = 0.018). Kinematics and MDF both fluctuated non-monotonically as subjects fatigued. Changes in MDF significantly preceded changes in mean trunk lean (p = 0.009) and hip angles (p = 0.025), and trunk lean range of motion (p = 0.029). Fluctuations in MDF were positively correlated with fluctuations in mean trunk lean (p = 0.009) and knee splay angles (p = 0.011), and with trunk lean (p = 0.002) and ankle (p = 0.001) range of motion. These results therefore establish a direct link between changes in muscle fatigue state and subsequent changes in movement kinematics during cycling.. PMID:18990638

  7. A Wireless sEMG Recording System and Its Application to Muscle Fatigue Detection

    PubMed Central

    Chang, Kang-Ming; Liu, Shin-Hong; Wu, Xuan-Han

    2012-01-01

    Surface electromyography (sEMG) is an important measurement for monitoring exercise and fitness. Because if its high sampling frequency requirement, wireless transmission of sEMG data is a challenge. In this article a wireless sEMG measurement system with a sampling frequency of 2 KHz is developed based upon a MSP 430 microcontroller and Bluetooth transmission. Standard isotonic and isometric muscle contraction are clearly represented in the receiving user interface. Muscle fatigue detection is an important application of sEMG. Traditional muscle fatigue is detected from the median frequency of the sEMG power spectrum. The regression slope of the linear regression of median frequency is an important muscle fatigue index. A more negative slope value represents a higher muscle fatigue condition. To test the system performance, muscle fatigue detection was examined by having subjects run on a pedaled-multifunctional elliptical trainer for approximately 30 minutes at three loading levels. Ten subjects underwent a total of 60 exercise sessions to provide the experimental data. Results showed that the regression slope gradually decreases as expected, and there is a significant gender difference. PMID:22368481

  8. 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

  9. Degradation of residual strength in SCS-6/Ti-15-3 Due to fully reversed fatigue

    NASA Astrophysics Data System (ADS)

    Calcaterra, J. R.; Mall, S.; Coghlan, S. C.

    1999-02-01

    Little attention has been given to residual strength degradation in titanium matrix composites (TMCs) after exposure to fatigue loading. To address this problem, fatigue tests on SCS-6/Ti-15-3 were performed to investigate the fatigue life and residual strength behavior of TMCs with different fiber volume fractions. Results indicate that fiber volume fraction seems to have an effect on both of these quantities. Lower fiber percentages result in a material where the characteristics of the matrix, such as hardening or cracking, play a much larger role in the composite response. Fatigue lives were not affected by fiber volume fraction at higher strain ranges, but lower fiber volume fractions resulted in shorter fatigue lives at lower strain values. Also, a slight increase in residual strength occurred up to 75 pct of fatigue life, for the lower-fiber volume fraction material. Despite these distinctions between specimens with different fiber contents, all specimens tested retained the majority of their strength prior to failure.

  10. The value of multiple tests of respiratory muscle strength

    PubMed Central

    Steier, Joerg; Kaul, Sunny; Seymour, John; Jolley, Caroline; Rafferty, Gerrard; Man, William; Luo, Yuan M; Roughton, Michael; Polkey, Michael I; Moxham, John

    2007-01-01

    Background Respiratory muscle weakness is an important clinical problem. Tests of varying complexity and invasiveness are available to assess respiratory muscle strength. The relative precision of different tests in the detection of weakness is less clear, as is the value of multiple tests. Methods The respiratory muscle function tests of clinical referrals who had multiple tests assessed in our laboratories over a 6‐year period were analysed. Thresholds for weakness for each test were determined from published and in‐house laboratory data. The patients were divided into three groups: those who had all relevant measurements of global inspiratory muscle strength (group A, n = 182), those with full assessment of diaphragm strength (group B, n = 264) and those for whom expiratory muscle strength was fully evaluated (group C, n = 60). The diagnostic outcome of each inspiratory, diaphragm and expiratory muscle test, both singly and in combination, was studied and the impact of using more than one test to detect weakness was calculated. Results The clinical referrals were primarily for the evaluation of neuromuscular diseases and dyspnoea of unknown cause. A low maximal inspiratory mouth pressure (Pimax) was recorded in 40.1% of referrals in group A, while a low sniff nasal pressure (Sniff Pnasal) was recorded in 41.8% and a low sniff oesophageal pressure (Sniff Poes) in 37.9%. When assessing inspiratory strength with the combination of all three tests, 29.6% of patients had weakness. Using the two non‐invasive tests (Pimax and Sniff Pnasal) in combination, a similar result was obtained (low in 32.4%). Combining Sniff Pdi (low in 68.2%) and Twitch Pdi (low in 67.4%) reduced the diagnoses of patients with diaphragm weakness to 55.3% in group B. 38.3% of the patients in group C had expiratory muscle weakness as measured by maximum expiratory pressure (Pemax) compared with 36.7% when weakness was diagnosed by cough gastric pressure (Pgas), and 28.3% when

  11. 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.

  12. The influence of tensile fatigue damage on residual compressive strength of woven composites

    SciTech Connect

    Mitrovic, M.; Carman, G.P.

    1995-12-31

    The long term mechanical fatigue of a Celion G30-500/PMR-15 woven composite system is investigated to study the interrelationship between thermo-mechanical properties, namely the thermal expansion coefficient (TEC) and the compressive strength. Residual compressive strength measurements (IITRI fixture) conducted on specimens subjected to tension-tension fatigue cycling indicate that this material property is sensitive to cracks and delaminations which form during mechanical cycling. Measured compressive strength degradation are as large as 49% for this material undergoing mechanical fatigue cycling with TEC degradation as large as 61%. Experimental results show that a correlation exists between TEC measurements and compressive strength. This correlation suggests that TEC measurements may be used as a damage evaluation technique.

  13. Photobiomodulation delays the onset of skeletal muscle fatigue in a dose-dependent manner.

    PubMed

    Larkin-Kaiser, Kelly A; Borsa, Paul A; Baweja, Harsimran S; Moore, Molly A; Tillman, Mark D; George, Steven Z; Christou, Evangelos A

    2016-09-01

    Photobiomodulation (PBM) therapy has been implicated as an effective ergogenic aid to delay the onset of muscle fatigue. The purpose of this study was to examine the dose-response ergogenic properties of PBM therapy and its ability to prolong time to task failure by enhancing muscle activity and delaying the onset of muscle fatigue using a static positioning task. Nine participants (24.3 ± 4.9 years) received three doses of near-infrared (NIR) light therapy randomly on three separate sessions (sham, 240, and 480 J). For the positioning task, participants held a 30 % one-repetition maximum (1-RM) load using the index finger until volitional fatigue. Surface electromyography (sEMG) of the first dorsal interosseous muscle was recorded for the length of the positioning task. Outcomes included time to task failure (TTF), muscle fatigue, movement accuracy, motor output variability, and muscle activity (sEMG). The 240-J dose significantly extended TTF by 26 % (p = 0.032) compared with the sham dose. TTF for the 240-J dose was strongly associated with a decrease in muscle fatigue (R (2) = 0.54, p = 0.024). Our findings show that a 240-J dose of NIR light therapy is efficacious in delaying the onset and extent of muscle fatigue during submaximal isometric positioning tasks. Our findings suggest that NIR light therapy may be used as an ergogenic aid during functional tasks or post-injury rehabilitation. PMID:27305924

  14. Fatigue strength and evaluation of creep damage during fatigue cycling of Inconel Alloy 625

    SciTech Connect

    Purohit, A.; Thiele, U.; O'Donnell, J.E.

    1983-06-01

    Evaluation of high strain rate and corresponding low strain rate tests indicate no creep-fatigue interaction. For T greater than or equal to 900/sup 0/C, creep damage predominates during the cyclic straining. For tests in which creep damage is largely suppressed - for example in high-frequency reverse bend fatigue tests - the cycles to fatigue failure were found to increase directly with the degree of suppression of creep damage. However, a practical limit exists for suppression of creep damage at 1100/sup 0/C; at that temperature, even for the high frequency reverse bend tests (approx. 1000 rpm with ..sigma.. = 12.3% s/sup -1/), the creep damage predominated over the fatigue damage.

  15. Vibration-induced muscle fatigue, a possible contribution to musculoskeletal injury.

    PubMed

    Adamo, Diane E; Martin, Bernard J; Johnson, Peter W

    2002-11-01

    Localized muscle fatigue resulting from 30-min sustained and intermittent grip exertions of 5% maximal voluntary contraction (MVC) with and without hand-vibration exposure (10 Hz, 7 mm displacement amplitude) was investigated. Muscle fatigue was quantified by the magnitude of the twitch force elicited in the right flexor digitorum superficialis muscle of the long finger using the low-frequency fatigue (LFF) method. The influence of vibration in the sustained grip exertion condition exacerbates fatigue as seen with the reduction in twitch force 30-60 min post-work task. Intermittent low grip force exertion conditions with and without vibration exposure show negligible fatigue, suggesting the benefit of rest in the work cycle. Perception of muscle fatigue was dissociated from the objective measure of twitch force, suggesting that LFF was not perceived. The presence of LFF and the lack of perception of LFF may increase the risk for the development of musculoskeletal disorders. The findings of this study may apply to the design of the work cycles and tasks that require the use of vibratory tools. PMID:12436281

  16. Effect of expiratory muscle strength training on elderly cough function.

    PubMed

    Kim, Jaeock; Davenport, Paul; Sapienza, Christine

    2009-01-01

    Age-related loss of muscle strength, known as sarcopenia, in the expiratory muscles, along with reductions in lung elastic recoil and chest wall compliance decreases the intrathoacic airway pressure as well as expiratory flow rates and velocity, greatly impacting an elderly person's ability to generate the forces essential for cough. This study examined the effects of a 4-week expiratory muscle strength training (EMST) program on maximum expiratory pressure (MEP) and cough function in 18 healthy but sedentary elderly adults. MEP significantly increased after the EMST program from 77.14+/-20.20 to 110.83+/-26.11cmH(2)O. Parameters measured during reflexive coughs produced by capsaicin challenge, indicated that compression phase duration significantly decreased (from 0.35+/-0.19 to 0.16+/-0.17s), peak expiratory flow rate decreased (from 4.98+/-2.18 to 8.00+/-3.05l/s) and post-peak plateau integral amplitude significantly increased (from 3.49+/-2.46 to 6.83+/-4.16l/ss) with the EMST program. EMST seems to be an effective program to increase the expiratory muscle strength in the sedentary elderly, which contribute to an enhanced cough function. PMID:18457885

  17. 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. PMID:26706555

  18. Kinesthetic imagery training of forceful muscle contractions increases brain signal and muscle strength.

    PubMed

    Yao, Wan X; Ranganathan, Vinoth K; Allexandre, Didier; Siemionow, Vlodek; Yue, Guang H

    2013-01-01

    The purpose of this study was to compare the effect of training using internal imagery (IMI; also known as kinesthetic imagery or first person imagery) with that of external imagery (EMI; also known as third-person visual imagery) of strong muscle contractions on voluntary muscle strengthening. Eighteen young, healthy subjects were randomly assigned to one of three groups (6 in each group): internal motor imagery (IMI), external motor imagery (EMI), or a no-practice control (CTRL) group. Training lasted for 6 weeks (~15 min/day, 5 days/week). The participants' right arm elbow-flexion strength, muscle electrical activity, and movement-related cortical potential (MRCP) were evaluated before and after training. Only the IMI group showed significant strength gained (10.8%) while the EMI (4.8%) and CTRL (-3.3%) groups did not. Only the IMI group showed a significant elevation in MRCP on scalp locations over both the primary motor (M1) and supplementary motor cortices (EMI group over M1 only) and this increase was significantly greater than that of EMI and CTRL groups. These results suggest that training by IMI of forceful muscle contractions was effective in improving voluntary muscle strength without physical exercise. We suggest that the IMI training likely strengthened brain-to-muscle (BTM) command that may have improved motor unit recruitment and activation, and led to greater muscle output. Training by IMI of forceful muscle contractions may change the activity level of cortical motor control network, which may translate into greater descending command to the target muscle and increase its strength. PMID:24133427

  19. Weibull models of fracture strengths and fatigue behavior of dental resins in flexure and shear.

    PubMed

    Baran, G R; McCool, J I; Paul, D; Boberick, K; Wunder, S

    1998-01-01

    In estimating lifetimes of dental restorative materials, it is useful to have available data on the fatigue behavior of these materials. Current efforts at estimation include several untested assumptions related to the equivalence of flaw distributions sampled by shear, tensile, and compressive stresses. Environmental influences on material properties are not accounted for, and it is unclear if fatigue limits exist. In this study, the shear and flexural strengths of three resins used as matrices in dental restorative composite materials were characterized by Weibull parameters. It was found that shear strengths were lower than flexural strengths, liquid sorption had a profound effect on characteristic strengths, and the Weibull shape parameter obtained from shear data differed for some materials from that obtained in flexure. In shear and flexural fatigue, a power law relationship applied for up to 250,000 cycles; no fatigue limits were found, and the data thus imply only one flaw population is responsible for failure. Again, liquid sorption adversely affected strength levels in most materials (decreasing shear strengths and flexural strengths by factors of 2-3) and to a greater extent than did the degree of cure or material chemistry. PMID:9730059

  20. Correlation between muscle electrophysiology and strength after fibular nerve injury.

    PubMed

    Won, Yu Hui; Kim, Kang-Won; Choi, Jun Tak; Ko, Myoung-Hwan; Park, Sung-Hee; Seo, Jeong-Hwan

    2016-08-01

    Muscle strength measurement is important when evaluating the degree of impairment in patients with nerve injury. However, accurate and objective evaluation may be difficult in patients with severe pain or those who intentionally try to avoid full exertion. We investigated the usefulness of the affected-to-unaffected side electrophysiological parameter ratios as a measure of objective ankle dorsiflexion (ADF) strength in patients with unilateral fibular nerve injury (FNI). ADF strength was measured in patients with FNI via handheld dynamometer and manual muscle test (MMT). Fibular nerve compound muscle action potential (CMAP) amplitude and latency and ADF strength of the affected side were presented as ratios to the corresponding measurements of the unaffected side. We analysed the correlation of the CMAP ratio with the ADF strength ratio using a dynamometer and compared the CMAP ratios according to MMT grade. Fifty-two patients with FNI were enrolled. The mean CMAP latency ratio did not differ between MMT groups (p = 0.573). The CMAP amplitude ratio proportionally increased with the quantified ADF strength ratio via dynamometer increase (ρ = 0.790; p < 0.001), but the CMAP latency ratio and the quantified ADF strength ratio did not significantly correlate (ρ = 0.052; p = 0.713). The average CMAP amplitude ratio significantly differed between MMT groups (p < 0.001), and post hoc tests showed significant differences in all paired comparisons except of Fair and Good grades (p = 0.064). Electrophysiological parameter ratio, such as the affected-to-unaffected side CMAP amplitude ratio, might be sensitive parameters for ADF power estimation after FNI. PMID:27142447

  1. 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.

  2. 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.

  3. Effects of fatigue duration and muscle type on voluntary and evoked contractile properties.

    PubMed

    Behm, D G; St-Pierre, D M

    1997-05-01

    The effects of fatigue duration and muscle type on voluntary and evoked contractile properties were investigated with an isometric, intermittent, submaximal fatigue protocol. Four groups performed contractions of the plantar flexors and quadriceps at various intensities to produce long (LDF; 19 min 30 s)- and short-duration fatigue (SDF; 4 min 17 s). The LDF group had a significantly greater decrease in muscle activation than did the SDF group (12 vs. 5.8%) during recovery, although there was no difference in the impairment of maximum voluntary contraction force beyond 30 s of recovery. The significant decrease in the compound muscle action potential of the LDF group (M-wave amplitude; 14.7%) contrasted with the M-wave potentiation of the SDF group (15.7%), suggesting changes in membrane excitation may affect LDF. The quadriceps group performing contractions at 50% MVC experienced a smaller decrease in agonist electromyograph activity than did other groups, indicating both muscle and fatigue duration specificity. Impairments in excitation-contraction coupling were indicated by changes in quadriceps peak twitch and time to peak twitch while decreases in PF M-wave amplitudes suggested a disruption of membrane potentials. Results suggest that fatigue mechanisms may be duration (activation, half relaxation time) or muscle specific (electromyograph, twitch torque) or a combination of both (M wave, time to peak twitch torque). PMID:9134916

  4. 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. PMID:24594079

  5. 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.

  6. Bone mineral density, muscle strength, and recreational exercise in men

    NASA Technical Reports Server (NTRS)

    Snow-Harter, C.; Whalen, R.; Myburgh, K.; Arnaud, S.; Marcus, R.

    1992-01-01

    Muscle strength has been shown to predict bone mineral density (BMD) in women. We examined this relationship in 50 healthy men who ranged in age from 28 to 51 years (average 38.3 years). BMD of the lumbar spine, proximal femur, whole body, and tibia were measured by dual-energy x-ray absorptiometry (Hologic QDR 1000W). Dynamic strength using one repetition maximum was assessed for the biceps, quadriceps, and back extensors and for the hip abductors, adductors, and flexors. Isometric grip strength was measured by dynamometry. Daily walking mileage was assessed by 9 week stepmeter records and kinematic analysis of video filming. Subjects were designated as exercisers and nonexercisers. Exercisers participated in recreational exercise at least two times each week. The results demonstrated that BMD at all sites correlated with back and biceps strength (p < 0.01 to p = 0.0001). Body weight correlated with tibia and whole-body BMD (p < 0.001); age negatively correlated with Ward's triangle BMD (p < 0.01). In stepwise multiple regressions, back strength was the only independent predictor of spine and femoral neck density (R2 = 0.27). Further, back strength was the most robust predictor of BMD at the trochanter, Ward's triangle, whole body, and tibia, although biceps strength, age, body weight, and leg strength contributed significantly to BMD at these skeletal sites, accounting for 35-52% of the variance in BMD. Exercisers and nonexercisers were similar for walking (3.97 versus 3.94 miles/day), age (37.8 versus 38.5) years, and weight (80.0 versus 77.7 kg). However, BMD and muscle strength were significantly greater in exercises than in nonexercisers.(ABSTRACT TRUNCATED AT 250 WORDS).

  7. 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

  8. Computation and Evaluation of Features of Surface Electromyogram to Identify the Force of Muscle Contraction and Muscle Fatigue

    PubMed Central

    Arjunan, Sridhar P.; Kumar, Dinesh K.; Naik, Ganesh

    2014-01-01

    The relationship between force of muscle contraction and muscle fatigue with six different features of surface electromyogram (sEMG) was determined by conducting experiments on thirty-five volunteers. The participants performed isometric contractions at 50%, 75%, and 100% of their maximum voluntary contraction (MVC). Six features were considered in this study: normalised spectral index (NSM5), median frequency, root mean square, waveform length, normalised root mean square (NRMS), and increase in synchronization (IIS) index. Analysis of variance (ANOVA) and linear regression analysis were performed to determine the significance of the feature with respect to the three factors: muscle force, muscle fatigue, and subject. The results show that IIS index of sEMG had the highest correlation with muscle fatigue and the relationship was statistically significant (P < 0.01), while NSM5 associated best with level of muscle contraction (%MVC) (P < 0.01). Both of these features were not affected by the intersubject variations (P > 0.05). PMID:24995275

  9. The role of cyclic plastic zone size on fatigue crack growth behavior in high strength steels

    NASA Astrophysics Data System (ADS)

    Korda, Akhmad A.; Miyashita, Y.; Mutoh, Y.

    2015-09-01

    The role of cyclic plastic zone in front of the crack tip was studied in high strength steels. Estimated plastic zone size would be compared with actual observation. Strain controlled fatigue tests of the steels were carried out to obtain cyclic stress-strain curves for plastic zone estimation. Observations of plastic zone were carried out using in situ SEM fatigue crack growth tests under a constant-ΔK. Hard microstructures in structural steels showed to inhibit the extent of plastic deformation around the crack tip. The rate of crack growth can be correlated with the size of plastic zone. The smaller the plastic zone size, the slower the fatigue crack growth.

  10. Fatigue strength improvement of MIG-welded joint by shot peening

    NASA Astrophysics Data System (ADS)

    Azida Che Lah, Nur; Ali, Aidy

    2011-02-01

    In this study, the effect of controlled shot peening (CSP) treatment on the fatigue strength of an ASTM A516 grade 70 carbon steel MIG-welded joint has been studied quantitatively. Metallurgical modifications, hardness, elemental compositions, and internal discontinuities, such as porosity and inclusions found in treated and untreated fusion welded joints, were characterized. The fatigue results of as-welded and peened skimmed joints were compared. It was observed that the effect of the CSP and skimming processes improved the fatigue life of the fusion weld by 63% on MIG-welded samples.

  11. Fatigue reliability based on residual strength model with hybrid uncertain parameters

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Qiu, Zhi-Ping

    2012-02-01

    The aim of this paper is to evaluate the fatigue reliability with hybrid uncertain parameters based on a residual strength model. By solving the non-probabilistic set-based reliability problem and analyzing the reliability with randomness, the fatigue reliability with hybrid parameters can be obtained. The presented hybrid model can adequately consider all uncertainties affecting the fatigue reliability with hybrid uncertain parameters. A comparison among the presented hybrid model, non-probabilistic set-theoretic model and the conventional random model is made through two typical numerical examples. The results show that the presented hybrid model, which can ensure structural security, is effective and practical.

  12. 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.

  13. Effect of pre-exercise phototherapy applied with different cluster probe sizes on elbow flexor muscle fatigue.

    PubMed

    Rossato, Mateus; Dellagrana, Rodolfo A; Lanferdini, Fábio J; Sakugawa, Raphael L; Lazzari, Caetano D; Baroni, Bruno M; Diefenthaeler, Fernando

    2016-08-01

    Phototherapy has been used for reducing muscle fatigue. In view of the various types of phototherapy cluster probes available in the market, the purpose of this study was to compare the effects of a similar phototherapy dosage with two different cluster probes on elbow flexor muscle fatigue: small cluster probe (SC = 9 diodes; 7.5 cm(2)) vs. large cluster probe (LC = 33 diodes; 30.2 cm(2)). Ten physically active male aged 18-35 years participate in a randomized, crossover, double-blind, placebo-controlled trial, which each participant was submitted to the same testing protocol in four sessions (separated by at least 48 h) with different treatments: LC-phototherapy, SC-phototherapy, LC-placebo, and SC-placebo. The elbow flexion maximal isometric voluntary contraction (MIVC) was performed before and after a fatigue protocol (60 % of MIVC until exhaustion). Electromyography (EMG) of the biceps brachii muscle was collected during all testing procedure. Phototherapy with dose of 60 J per muscle [LC: 33 diodes = 5 lasers (850 nm), 12 LEDs (670 nm), 8 LEDs (880 nm), and 8 LEDs (950 nm); SC: 9 diodes = 5 lasers (850 nm) and 4 LEDs (670 nm)] or placebo applications occurred before fatigue protocol. Two-way ANOVA (treatment and time factors) and one-way ANOVA were used, followed by LSD post hoc. Time to exhaustion was significantly higher in active LC (15 %; p = 0.031) and SC (14 %; p = 0.038) in comparison with their respective placebo treatments, without differences between LC and SC (p > 0.05) or between placebo conditions (p > 0.05). This larger exercise tolerance in phototherapy conditions was not accompanied by a higher decrement in the volunteers' maximal strength capacity (11-15 %; p > 0.05 for all). EMG signals presented no difference between the four condition tested here. In both large and small cluster probes (according parameters tested in this study) led to reduced fatigue in elbow flexor muscles, without

  14. 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.

  15. 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). PMID:25886019

  16. 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

  17. Potential molecular mechanisms underlying muscle fatigue mediated by reactive oxygen and nitrogen species

    PubMed Central

    Debold, Edward P.

    2015-01-01

    Intense contractile activity causes a dramatic decline in the force and velocity generating capacity of skeletal muscle within a few minutes, a phenomenon that characterizes fatigue. Much of the research effort has focused on how elevated levels of the metabolites of ATP hydrolysis might inhibit the function of the contractile proteins. However, there is now growing evidence that elevated levels of reactive oxygen and nitrogen species (ROS/RNS), which also accumulate in the myoplasm during fatigue, also play a causative role in this type of fatigue. The most compelling evidence comes from observations demonstrating that pre-treatment of intact muscle with a ROS scavenger can significantly attenuate the development of fatigue. A clear advantage of this line of inquiry is that the molecular targets and protein modifications of some of the ROS scavengers are well-characterized enabling researchers to begin to identify potential regions and even specific amino acid residues modified during fatigue. Combining this knowledge with assessments of contractile properties from the whole muscle level down to the dynamic motions within specific contractile proteins enable the linking of the structural modifications to the functional impacts, using advanced chemical and biophysical techniques. Based on this approach at least two areas are beginning emerge as potentially important sites, the regulatory protein troponin and the actin binding region of myosin. This review highlights some of these recent efforts which have the potential to offer uniquely precise information on the underlying molecular basis of fatigue. This work may also have implications beyond muscle fatigue as ROS/RNS mediated protein modifications are also thought to play a role in the loss of muscle function with aging and in some acute pathologies like cardiac arrest and ischemia. PMID:26388779

  18. Muscle Strength and Flexibility without and with Visual Impairments Judoka's

    ERIC Educational Resources Information Center

    Karakoc, Onder

    2016-01-01

    The aim of this study was to examine muscle strength and flexibility of judoka with and without visual impairments. A total of 32 male national judoka volunteered to participate in this study. There were 20 male judoka without visual impairments (mean ± SD; age: 19.20 ± 5.76 years, body weight: 66.45 ± 11.09 kg, height: 169.60 ± 7.98 cm, sport…

  19. Effects of whole-body vibration after eccentric exercise on muscle soreness and muscle strength recovery

    PubMed Central

    Timon, Rafael; Tejero, Javier; Brazo-Sayavera, Javier; Crespo, Carmen; Olcina, Guillermo

    2016-01-01

    [Purpose] The aim of this study was to investigate whether or not a single whole-body vibration treatment after eccentric exercise can reduce muscle soreness and enhance muscle recovery. [Subjects and Methods] Twenty untrained participants were randomly assigned to two groups: a vibration group (n=10) and control group (n=10). Participants performed eccentric quadriceps training of 4 sets of 5 repetitions at 120% 1RM, with 4 min rest between sets. After that, the vibration group received 3 sets of 1 min whole body vibration (12 Hz, 4 mm) with 30 s of passive recovery between sets. Serum creatine kinase, blood urea nitrogen, muscle soreness (visual analog scale) and muscle strength (peak isometric torque) were assessed. [Results] Creatine kinase was lower in the vibration group than in the control group at 24 h (200.2 ± 8.2 vs. 300.5 ± 26.1 U/L) and at 48 h (175.2 ± 12.5 vs. 285.2 ± 19.7 U/L) post-exercise. Muscle soreness decreased in vibration group compared to control group at 48 h post-exercise (34.1 ± 11.4 vs. 65.2 ± 13.2 mm). [Conclusion] Single whole-body vibration treatment after eccentric exercise reduced delayed onset muscle soreness but it did not affect muscle strength recovery. PMID:27390415

  20. Effects of whole-body vibration after eccentric exercise on muscle soreness and muscle strength recovery.

    PubMed

    Timon, Rafael; Tejero, Javier; Brazo-Sayavera, Javier; Crespo, Carmen; Olcina, Guillermo

    2016-06-01

    [Purpose] The aim of this study was to investigate whether or not a single whole-body vibration treatment after eccentric exercise can reduce muscle soreness and enhance muscle recovery. [Subjects and Methods] Twenty untrained participants were randomly assigned to two groups: a vibration group (n=10) and control group (n=10). Participants performed eccentric quadriceps training of 4 sets of 5 repetitions at 120% 1RM, with 4 min rest between sets. After that, the vibration group received 3 sets of 1 min whole body vibration (12 Hz, 4 mm) with 30 s of passive recovery between sets. Serum creatine kinase, blood urea nitrogen, muscle soreness (visual analog scale) and muscle strength (peak isometric torque) were assessed. [Results] Creatine kinase was lower in the vibration group than in the control group at 24 h (200.2 ± 8.2 vs. 300.5 ± 26.1 U/L) and at 48 h (175.2 ± 12.5 vs. 285.2 ± 19.7 U/L) post-exercise. Muscle soreness decreased in vibration group compared to control group at 48 h post-exercise (34.1 ± 11.4 vs. 65.2 ± 13.2 mm). [Conclusion] Single whole-body vibration treatment after eccentric exercise reduced delayed onset muscle soreness but it did not affect muscle strength recovery. PMID:27390415

  1. Measurements of muscle strength and performance in children with normal and diseased muscle.

    PubMed Central

    Hosking, J P; Bhat, U S; Dubowitz, V; Edwards, R H

    1976-01-01

    A study has been made of two simple means of measuring muscle power in children with normal and diseased muscle. In one the length of time that the leg and the head could be held at 45 degrees above the horizontal was measured with the child supine. In the second, measurements were made of the isometric strength of six muscle groups with the newly developed Hammersmith Myometer. In the timed performance tests only 5 (8%) of a group of 61 children known to have muscle disease achieved the minimum expected values for their ages. Myometer readings of the isometric power of the children with muscle disease also have values which were below those of a comparable group of normal children. The reproducibility of muscle strength measurements in young children has been shown to be good, whereas the timed performance tests, though able to differentiate normal children from children with muscle disease, did not show sufficient reporducibility for this test to be recommended for sequential measurements. Images FIG. 1 PMID:1015849

  2. Evoked EMG-based torque prediction under muscle fatigue in implanted neural stimulation

    NASA Astrophysics Data System (ADS)

    Hayashibe, Mitsuhiro; Zhang, Qin; Guiraud, David; Fattal, Charles

    2011-10-01

    In patients with complete spinal cord injury, fatigue occurs rapidly and there is no proprioceptive feedback regarding the current muscle condition. Therefore, it is essential to monitor the muscle state and assess the expected muscle response to improve the current FES system toward adaptive force/torque control in the presence of muscle fatigue. Our team implanted neural and epimysial electrodes in a complete paraplegic patient in 1999. We carried out a case study, in the specific case of implanted stimulation, in order to verify the corresponding torque prediction based on stimulus evoked EMG (eEMG) when muscle fatigue is occurring during electrical stimulation. Indeed, in implanted stimulation, the relationship between stimulation parameters and output torques is more stable than external stimulation in which the electrode location strongly affects the quality of the recruitment. Thus, the assumption that changes in the stimulation-torque relationship would be mainly due to muscle fatigue can be made reasonably. The eEMG was proved to be correlated to the generated torque during the continuous stimulation while the frequency of eEMG also decreased during fatigue. The median frequency showed a similar variation trend to the mean absolute value of eEMG. Torque prediction during fatigue-inducing tests was performed based on eEMG in model cross-validation where the model was identified using recruitment test data. The torque prediction, apart from the potentiation period, showed acceptable tracking performances that would enable us to perform adaptive closed-loop control through implanted neural stimulation in the future.

  3. Evoked EMG-based torque prediction under muscle fatigue in implanted neural stimulation.

    PubMed

    Hayashibe, Mitsuhiro; Zhang, Qin; Guiraud, David; Fattal, Charles

    2011-12-01

    In patients with complete spinal cord injury, fatigue occurs rapidly and there is no proprioceptive feedback regarding the current muscle condition. Therefore, it is essential to monitor the muscle state and assess the expected muscle response to improve the current FES system toward adaptive force/torque control in the presence of muscle fatigue. Our team implanted neural and epimysial electrodes in a complete paraplegic patient in 1999. We carried out a case study, in the specific case of implanted stimulation, in order to verify the corresponding torque prediction based on stimulus evoked EMG (eEMG) when muscle fatigue is occurring during electrical stimulation. Indeed, in implanted stimulation, the relationship between stimulation parameters and output torques is more stable than external stimulation in which the electrode location strongly affects the quality of the recruitment. Thus, the assumption that changes in the stimulation-torque relationship would be mainly due to muscle fatigue can be made reasonably. The eEMG was proved to be correlated to the generated torque during the continuous stimulation while the frequency of eEMG also decreased during fatigue. The median frequency showed a similar variation trend to the mean absolute value of eEMG. Torque prediction during fatigue-inducing tests was performed based on eEMG in model cross-validation where the model was identified using recruitment test data. The torque prediction, apart from the potentiation period, showed acceptable tracking performances that would enable us to perform adaptive closed-loop control through implanted neural stimulation in the future. PMID:21975831

  4. Concurrent cognitive task may improve motor work performance and reduce muscle fatigue.

    PubMed

    Evstigneeva, Maria; Aleksandrov, Aleksandr; Mathiassen, Svend Erik; Lyskov, Eugene

    2012-01-01

    Performance of certain cognitive tasks either during physical load or in rest pauses between boosts might lead to slowing of muscle fatigue and fatigue related decline in performance. Seventeen right-handed healthy volunteers (age 24 ± 1.4, 8 males) participated in this study, aiming to investigate the effect of the level of the cognitive information processing - 1) passive perception of audio stimuli, 2) active stimuli discrimination, 3) active stimuli discrimination following motor response - on motor task performance (handgrip test 30% and 7% of MVC) and muscle fatigue development. Cognitive tasks show the following effects on motor work: i) Perceived fatigue during 30 % MVC (fatiguing) condition developed slower if participant pressed button in response to deviant acoustic stimuli, as compared to passive listening. Counting task, an active task without motor component, took the intermediate position and did not differ significantly from two other cognitive tasks. ii) MVC after 30% MVC (fatiguing) condition tended to decrease stronger when accompanied with passive listening in comparison with both active tasks. iii) Motor task performance during 30% MVC (fatiguing) condition was better for active cognitive task with motor component than for passive task. Active task without motor component took the intermediate position and did not differ significantly from both the other cognitive tasks. PMID:22317158

  5. Acoustic Correlates of Fatigue in Laryngeal Muscles: Findings for a Criterion-Based Prevention of Acquired Voice Pathologies

    ERIC Educational Resources Information Center

    Boucher, Victor J.

    2008-01-01

    Purpose: The objective was to identify acoustic correlates of laryngeal muscle fatigue in conditions of vocal effort. Method: In a previous study, a technique of electromyography (EMG) served to define physiological signs of "voice fatigue" in laryngeal muscles involved in voicing. These signs correspond to spectral changes in contraction…

  6. Detection and Alert of muscle fatigue considering a Surface Electromyography Chaotic Model

    NASA Astrophysics Data System (ADS)

    Herrera, V.; Romero, J. F.; Amestegui, M.

    2011-03-01

    This work propose a detection and alert algorithm for muscle fatigue in paraplegic patients undergoing electro-therapy sessions. The procedure is based on a mathematical chaotic model emulating physiological signals and Continuous Wavelet Transform (CWT). The chaotic model developed is based on a logistic map that provides suitable data accomplishing some physiological signal class patterns. The CWT was applied to signals generated by the model and the resulting vector was obtained through Total Wavelet Entropy (TWE). In this sense, the presented work propose a viable and practical alert and detection algorithm for muscle fatigue.

  7. 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.

  8. Effects of soluble milk protein or casein supplementation on muscle fatigue following resistance training program: a randomized, double-blind, and placebo-controlled study

    PubMed Central

    2014-01-01

    Background The effects of protein supplementation on muscle thickness, strength and fatigue seem largely dependent on its composition. The current study compared the effects of soluble milk protein, micellar casein, and a placebo on strength and fatigue during and after a resistance training program. Methods Sixty-eight physically active men participated in this randomized controlled trial and underwent 10 weeks of lower-body resistance training. Participants were randomly assigned to the Placebo (PLA), Soluble Milk Protein (SMP, with fast digestion rate) or Micellar Casein (MC, with slow digestion rate) group. During the 10-week training period, participants were instructed to take 30 g of the placebo or protein twice a day, or three times on training days. Tests were performed on quadriceps muscles at inclusion (PRE), after 4 weeks (MID) and after 10 weeks (POST) of training. They included muscle endurance (maximum number of repetitions during leg extensions using 70% of the individual maximal load), fatigue (decrease in muscle power after the endurance test), strength, power and muscle thickness. Results Muscle fatigue was significantly lower (P < 0.05) in the SMP group at MID and POST (-326.8 ± 114.1 W and -296.6 ± 130.1 W, respectively) as compared with PLA (-439.2 ± 153.9 W and -479.2 ± 138.1 W, respectively) and MC (-415.1 ± 165.1 W and -413.7 ± 139.4 W, respectively). Increases in maximal muscle power, strength, endurance and thickness were not statistically different between groups. Conclusions The present study demonstrated that protein composition has a large influence on muscular performance after prolonged resistance training. More specifically, as compared with placebo or micellar casein, soluble milk protein (fast digestible) appeared to significantly reduce muscle fatigue induced by intense resistance exercise. PMID:25057266

  9. Depression of corticomotor excitability after muscle fatigue induced by electrical stimulation and voluntary contraction

    PubMed Central

    Kotan, Shinichi; Kojima, Sho; Miyaguchi, Shota; Sugawara, Kazuhiro; Onishi, Hideaki

    2015-01-01

    In this study, we examined the effect of muscle fatigue induced by tetanic electrical stimulation (ES) and submaximal isometric contraction on corticomotor excitability. Experiments were performed in a cross-over design. Motor-evoked potentials (MEPs) were elicited by transcranial magnetic stimulation (TMS). Corticomotor excitability was recorded before and after thumb opposition muscle fatigue tasks, in which 10% of the maximal tension intensity was induced by tetanic ES or voluntary contraction (VC). The participants were 10 healthy individuals who performed each task for 10 min. Surface electrodes placed over the abductor pollicis brevis (APB) muscle recorded MEPs. F- and M-waves were elicited from APB by supramaximal ES of the median nerve. After the tetanic ES- and VC tasks, MEP amplitudes were significantly lower than before the task. However, F- and M-wave amplitudes remained unchanged. These findings suggest that corticospinal excitability is reduced by muscle fatigue as a result of intracortical inhibitory mechanisms. Our results also suggest that corticomotor excitability is reduced by muscle fatigue caused by both VC and tetanic ES. PMID:26150781

  10. Immediate Effects of Kinesiology Taping of Quadriceps on Motor Performance after Muscle Fatigued Induction

    PubMed Central

    Ahn, Ick Keun; Kim, You Lim; Bae, Young-Hyeon; Lee, Suk Min

    2015-01-01

    Objectives. The purpose of this cross-sectional single-blind study was to investigate the immediate effects of Kinesiology taping of quadriceps on motor performance after muscle fatigued induction. Design. Randomized controlled cross-sectional design. Subjects. Forty-five subjects participated in this study. Participants were divided into three groups: Kinesiology taping group, placebo taping group, and nontaping group. Methods. Subjects performed short-term exercise for muscle fatigued induction, followed by the application of each intervention. Peak torque test, one-leg single hop test, active joint position sense test, and one-leg static balance test were carried out before and after the intervention. Results. Peak torque and single-leg hopping distance were significantly increased when Kinesiology taping was applied (p < 0.05). But there were no significant effects on active joint position sense and single-leg static balance. Conclusions. We proved that Kinesiology taping is effective in restoring muscle power reduced after muscle fatigued induction. Therefore, we suggest that Kinesiology taping is beneficial for fatigued muscles. PMID:26246835

  11. Evaluation of fatigue of respiratory and lower limb muscles during prolonged aerobic exercise.

    PubMed

    Nadiv, Yaara; Vachbroit, Ricki; Gefen, Amit; Elad, David; Zaretsky, Uri; Moran, Dani; Halpern, Pinchas; Ratnovsky, Anat

    2012-05-01

    The respiratory muscles may fatigue during prolonged exercises and thereby become a factor that limits extreme physical activity. The aim of the current study was to determine whether respiratory muscle fatigue imposes a limitation on extreme physical activity of well-trained young men. Electromyography (EMG) signals of respiratory (external intercostal and sternomastoid) and calf muscles (gastrocnemius) were measured (N = 8) during 1 hr of treadmill marching at a speed of 8 km/hr with and without a 15 kg backpack. The root mean square (RMS) and the mean power frequency of the EMG signals were evaluated for calculating fatigue indices. The EMG RMS revealed that the respiratory and calf muscles did not fatigue during the marching without a backpack load. The study did show, however, a significant rise in the EMG values when a backpack was carried with respect to the no-load condition (p < .05), which suggests that respiratory muscles should be trained in military recruits who are required to carry loaded backpacks while marching. PMID:22723112

  12. Effects of hyperbaric oxygen on muscle fatigue after maximal intermittent plantar flexion exercise.

    PubMed

    Shimoda, Manabu; Enomoto, Mitsuhiro; Horie, Masaki; Miyakawa, Shumpei; Yagishita, Kazuyoshi

    2015-06-01

    The purpose of this study was to investigate the effects of hyperbaric oxygen (HBO) treatment on muscle fatigue after maximal intermittent plantar flexion exercise. Twenty healthy male volunteers (aged from 21 to 24 years) were randomly assigned to either HBO or normoxic group and were blinded to their treatment and group assignment. The HBO group breathed 100% oxygen under 2.5 atmosphere absolute (ATA) for 60 minutes, whereas the normoxic group breathed room air under 1.2 ATA for 70 minutes. The subjects performed a fatigue test, which consisted of 50 maximal unilateral isometric plantar flexions, before and after intervention. Surface electromyography was recorded from triceps surae muscle. Subjects performed maximal voluntary contractions of isometric plantar flexions, and voluntary activation and twitch contractile properties were evaluated with cutaneous tibial nerve stimuli before and after intervention. Compared with initial values during repetitions 4-10, the plantar flexion torque during repetitions 41-50 decreased to 88.5 and 83.2% after HBO and normoxic treatment, respectively. A smaller decrease in muscle force was observed in the HBO group compared with the normoxic group. No differences in function between treatment groups were observed after nerve stimulation. These results suggest that HBO contributes to sustained force production due to suppressing the muscle fatigue progression. In practice, HBO can contribute to the prevention of excess fatigue of agonist muscles for specific exercises involving repeated jumping. PMID:25785701

  13. The Effects of Vibration and Muscle Fatigue on Trunk Sensorimotor Control in Low Back Pain Patients

    PubMed Central

    Abboud, Jacques; Nougarou, François; Normand, Martin C.

    2015-01-01

    Introduction Changes in sensorimotor function and increased trunk muscle fatigability have been identified in patients with chronic low back pain (cLBP). This study assessed the control of trunk force production in conditions with and without local erector spinae muscle vibration and evaluated the influence of muscle fatigue on trunk sensorimotor control. Methods Twenty non-specific cLBP patients and 20 healthy participants were asked to perform submaximal isometric trunk extension torque with and without local vibration stimulation, before and after a trunk extensor muscle fatigue protocol. Constant error (CE), variable error (VE) as well as absolute error (AE) in peak torque were computed and compared across conditions. Trunk extensor muscle activation during isometric contractions and during the fatigue protocol was measured using surface electromyography (sEMG). Results Force reproduction accuracy of the trunk was significantly lower in the patient group (CE = 9.81 ± 2.23 Nm; AE = 18.16 ± 3.97 Nm) than in healthy participants (CE = 4.44 ± 1.68 Nm; AE = 12.23 ± 2.44 Nm). Local erector spinae vibration induced a significant reduction in CE (4.33 ± 2.14 Nm) and AE (13.71 ± 3.45 Nm) mean scores in the patient group. Healthy participants conversely showed a significant increase in CE (8.17 ± 2.10 Nm) and AE (16.29 ± 2.82 Nm) mean scores under vibration conditions. The fatigue protocol induced erector spinae muscle fatigue as illustrated by a significant decrease in sEMG median time-frequency slopes. Following the fatigue protocol, patients with cLBP showed significant decrease in sEMG root mean square activity at L4-5 level and responded in similar manner with and without vibration stimulation in regard to CE mean scores. Conclusions Patients with cLBP have a less accurate force reproduction sense than healthy participants. Local muscle vibration led to significant trunk neuromuscular control improvements in the cLBP patients before and after a muscle

  14. Torque prediction using stimulus evoked EMG and its identification for different muscle fatigue states in SCI subjects.

    PubMed

    Zhang, Qin; Hayashibe, Mitsuhiro; Papaiordanidou, Maria; Fraisse, Philippe; Fattal, Charles; Guiraud, David

    2010-01-01

    Muscle fatigue is an unavoidable problem when electrical stimulation is applied to paralyzed muscles. The detection and compensation of muscle fatigue is essential to avoid movement failure and achieve desired trajectory. This work aims to predict ankle plantar-flexion torque using stimulus evoked EMG (eEMG) during different muscle fatigue states. Five spinal cord injured patients were recruited for this study. An intermittent fatigue protocol was delivered to triceps surae muscle to induce muscle fatigue. A hammerstein model was used to capture the muscle contraction dynamics to represent eEMG-torque relationship. The prediction of ankle torque was based on measured eEMG and past measured or past predicted torque. The latter approach makes it possible to use eEMG as a synthetic force sensor when force measurement is not available in daily use. Some previous researches suggested to use eEMG information directly to detect and predict muscle force during fatigue assuming a fixed relationship between eEMG and generated force. However, we found that the prediction became less precise with the increase of muscle fatigue when fixed parameter model was used. Therefore, we carried out the torque prediction with an adaptive parameters using the latest measurement. The prediction of adapted model was improved with 16.7%-50.8% comparing to the fixed model. PMID:21097036

  15. Effect of old age on human skeletal muscle force-velocity and fatigue properties.

    PubMed

    Callahan, Damien M; Kent-Braun, Jane A

    2011-11-01

    It is generally accepted that the muscles of aged individuals contract with less force, have slower relaxation rates, and demonstrate a downward shift in their force-velocity relationship. The factors mediating age-related differences in skeletal muscle fatigue are less clear. The present study was designed to test the hypothesis that age-related shifts in the force-velocity relationship impact the fatigue response in a velocity-dependent manner. Three fatigue protocols, consisting of intermittent, maximum voluntary knee extension contractions performed for 4 min, were performed by 11 young (23.5 ± 0.9 yr, mean ± SE) and 10 older (68.9 ± 4.3) women. The older group fatigued less during isometric contractions than the young group (to 71.1 ± 3.7% initial torque and 59.8 ± 2.5%, respectively; P = 0.02), while the opposite was true during contractions performed at a relatively high angular velocity of 270°·s(-1) (old: 28.0 ± 3.9% initial power, young: 52.1 ± 6.9%; P < 0.01). Fatigue was not different (P = 0.74) between groups during contractions at an intermediate velocity, which was selected for each participant based on their force-velocity relationship. There was a significant association between force-velocity properties and fatigue induced by the intermediate-velocity fatigue protocol in the older (r = 0.72; P = 0.02) and young (r = 0.63; P = 0.04) groups. These results indicate that contractile velocity has a profound impact on age-related skeletal muscle fatigue resistance and suggest that changes in the force-velocity relationship partially mediate this effect. PMID:21868683

  16. EMG parameters and EEG α Index change at fatigue period during different types of muscle contraction

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Zhou, Bin; Song, Gaoqing

    2010-10-01

    The purpose of this study is to measure and analyze the characteristics in change of EMG and EEG parameters at muscle fatigue period in participants with different exercise capacity. Twenty participants took part in the tests. They were divided into two groups, Group A (constant exerciser) and Group B (seldom-exerciser). MVC dynamic and 1/3 isometric exercises were performed; EMG and EEG signals were recorded synchronously during different type of muscle contraction. Results indicated that values of MVC, RMS and IEMG in Group A were greater than Group B, but isometric exercise time was shorter than the time of dynamic exercise although its intensity was light. Turning point of IEMG and α Index occurred synchronously during constant muscle contraction of isometric or dynamic exercise. It is concluded that IEMG turning point may be an indication to justify muscle fatigue. Synchronization of EEG and EMG reflects its common characteristics on its bio-electric change.

  17. EMG parameters and EEG α Index change at fatigue period during different types of muscle contraction

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Zhou, Bin; Song, Gaoqing

    2011-03-01

    The purpose of this study is to measure and analyze the characteristics in change of EMG and EEG parameters at muscle fatigue period in participants with different exercise capacity. Twenty participants took part in the tests. They were divided into two groups, Group A (constant exerciser) and Group B (seldom-exerciser). MVC dynamic and 1/3 isometric exercises were performed; EMG and EEG signals were recorded synchronously during different type of muscle contraction. Results indicated that values of MVC, RMS and IEMG in Group A were greater than Group B, but isometric exercise time was shorter than the time of dynamic exercise although its intensity was light. Turning point of IEMG and α Index occurred synchronously during constant muscle contraction of isometric or dynamic exercise. It is concluded that IEMG turning point may be an indication to justify muscle fatigue. Synchronization of EEG and EMG reflects its common characteristics on its bio-electric change.

  18. Increasing blood flow before exercise in spinal cord-injured individuals does not alter muscle fatigue.

    PubMed

    Olive, Jennifer L; Slade, Jill M; Bickel, C Scott; Dudley, Gary A; McCully, Kevin K

    2004-02-01

    Previous studies have shown increased fatigue in paralyzed muscle of spinal cord-injured (SCI) patients (Castro M, Apple D Jr, Hillegass E, and Dudley GA. Eur J Appl Physiol 80: 373-378, 1999; Gerrits H, Hopman MTE, Sargeant A, and de Haan A. Clin Physiol 21: 105-113, 2001). Our purpose was to determine whether the increased muscle fatigue could be due to a delayed rise in blood flow at the onset of exercise in SCI individuals. Isometric electrical stimulation was used to induce fatigue in the quadriceps femoris muscle of seven male, chronic (>1 yr postinjury), complete (American Spinal Injury Association, category A) SCI subjects. Cuff occlusion was used to elevate blood flow before electrical stimulation, and the magnitude of fatigue was compared with a control condition of electrical stimulation without prior cuff occlusion. Blood flow was measured in the femoral artery by Doppler ultrasound. Prior cuff occlusion increased blood flow in the first 30 s of stimulation compared with the No-Cuff condition (1,350 vs. 680 ml/min, respectively; P < 0.001), although blood flow at the end of stimulation was the same between conditions (1,260 +/- 140 vs. 1,160 +/- 370 ml/min, Cuff and No-Cuff condition, respectively; P = 0.511). Muscle fatigue was not significantly different between prior cuff occlusion and the control condition (32 +/- 13 vs. 35 +/- 10%; P = 0.670). In conclusion, increased muscle fatigue in SCI individuals is not associated with the prolonged time for blood flow to increase at the onset of exercise. PMID:14506095

  19. Nonsteady thermal stress analysis and thermal fatigue strength of metal-CFRP bonded joints

    NASA Astrophysics Data System (ADS)

    Yu, Qiang; Shiratori, Masaki; Mori, Takao

    1993-01-01

    In this paper, a finite-element method (FEM) system of nonsteady thermal stress analysis has been developed to analyze the problem of metal-fiber-reinforced plastic (FRP) bonded joints. The authors have presented a new algorithm for the system, which can provide an effective thermal stress analysis for metal-carbon-FRP (CFRP) bonded joints. The effectiveness, in terms of the accuracy and central processing unit (CPU) time, has been discussed by analyzing some typical problems. The thermal fatigue strength of Al-CFRP bonded joints has been studied through a series of thermal cyclic fatigue tests. It has been shown that the thermal fatigue strength of the joints can be well described by the maximum equivalent stress at the adhesive layer, which can be calculated by the developed FEM system.

  20. Prevalence of reduced muscle strength in older U.S. adults: United States, 2011-2012.

    PubMed

    Looker, Anne C; Wang, Chia-Yih

    2015-01-01

    Five percent of adults aged 60 and over had weak muscle strength and 13% had intermediate muscle strength, as defined by the new FNIH criteria. Weak muscle strength is clinically relevant because it is associated with slow gait speed, an important mobility impairment. It is also linked to an increased risk of death. The prevalence of reduced muscle strength increased with age and was higher in non-Hispanic Asian and Hispanic persons than in non-Hispanic white or non-Hispanic black persons. Decreasing muscle strength was linked with increased difficulty in rising from an armless chair, which is another important type of mobility impairment. PMID:25633238

  1. 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. PMID:26974490

  2. Residual Static Strength of ALuminum-Alloy Beams Containing Fatigue Cracks in the Tension Covers

    NASA Technical Reports Server (NTRS)

    Leybold, Herbert A.

    1961-01-01

    Static tests were performed on 31 box beams containing fatigue cracks in order to determine their residual static strengths. The beams were constructed of 7075 and 2024 aluminum alloy according to several designs and employed stringers that were either bonded, riveted, or an integral part of the skin. skin (both aaterials) had the highest residual static strengths, whereas 7075 beams with integrally stiffened covers had the lowest residual static strengths. Except for the integrally stiffened beams, the skin material did not contribute to the residual static strength of the beams because the crack propagated across the skin before maximum load was reached. For the integrally stiffened beams, crack propagation and failure were synonymous. The test results are compared with predictions of the residual static strength. Fair agreement between predicted strength and actual strength was obtained for all beams tested.

  3. Perm1 enhances mitochondrial biogenesis, oxidative capacity, and fatigue resistance in adult skeletal muscle.

    PubMed

    Cho, Yoshitake; Hazen, Bethany C; Gandra, Paulo G; Ward, Samuel R; Schenk, Simon; Russell, Aaron P; Kralli, Anastasia

    2016-02-01

    Skeletal muscle mitochondrial content and oxidative capacity are important determinants of muscle function and whole-body health. Mitochondrial content and function are enhanced by endurance exercise and impaired in states or diseases where muscle function is compromised, such as myopathies, muscular dystrophies, neuromuscular diseases, and age-related muscle atrophy. Hence, elucidating the mechanisms that control muscle mitochondrial content and oxidative function can provide new insights into states and diseases that affect muscle health. In past studies, we identified Perm1 (PPARGC1- and ESRR-induced regulator, muscle 1) as a gene induced by endurance exercise in skeletal muscle, and regulating mitochondrial oxidative function in cultured myotubes. The capacity of Perm1 to regulate muscle mitochondrial content and function in vivo is not yet known. In this study, we use adeno-associated viral (AAV) vectors to increase Perm1 expression in skeletal muscles of 4-wk-old mice. Compared to control vector, AAV1-Perm1 leads to significant increases in mitochondrial content and oxidative capacity (by 40-80%). Moreover, AAV1-Perm1-transduced muscles show increased capillary density and resistance to fatigue (by 33 and 31%, respectively), without prominent changes in fiber-type composition. These findings suggest that Perm1 selectively regulates mitochondrial biogenesis and oxidative function, and implicate Perm1 in muscle adaptations that also occur in response to endurance exercise. PMID:26481306

  4. Failure of activation of spinal motoneurones after muscle fatigue in healthy subjects studied by transcranial magnetic stimulation

    PubMed Central

    Andersen, Birgit; Westlund, Barbro; Krarup, Christian

    2003-01-01

    During a sustained maximal effort a progressive decline in the ability to drive motoneurones (MNs) develops. We used the recently developed triple stimulation technique (TST) to study corticospinal conduction after fatiguing exercise in healthy subjects. This method employs a collision technique to estimate the proportion of motor units activated by a transcranial magnetic stimulus. Following a sustained contraction of the abductor digiti minimi muscle at 50 % maximal force maintained to exhaustion there was an immediate reduction of the TST response from >95% to about 60%. This effect recovered to control levels within 1 min and implies that a decreased number of spinal MNs were excited. Additional TST experiments after maximal and submaximal efforts showed that the decrease in size of the TST response was related to duration and strength of exercise. Motor evoked potentials (MEPs) after conventional transcranial magnetic stimulation (TMS) and responses to peripheral nerve stimulation were recorded following the same fatigue protocol. The size of both the MEPs and the peripheral responses increased after the contraction and were in direct contrast to the decrease in size of the TST response. This points to increased probability of repetitive spinal MN activation during fatigue even if some MNs in the pool failed to discharge. Silent period duration following cortical stimulation lengthened by an average of 55 ms after the contraction and recovered within a time course similar to that of the TST response depression. Overall, the results suggest that the outflow from the motor cortex could become insufficient to drive all spinal MNs to discharge when the muscle is fatigued and that complex interactions between failure of activation and compensatory mechanisms to maintain motor unit activation occur during sustained voluntary activity. When inability to maintain force occurs during submaximal effort, failure of activation of motor units is predominant. PMID:12824449

  5. Associations of Sarcopenia and Sarcopenic Obesity With Metabolic Syndrome Considering Both Muscle Mass and Muscle Strength

    PubMed Central

    2016-01-01

    Objectives: We investigated the associations of sarcopenia-defined both in terms of muscle mass and muscle strength-and sarcopenic obesity with metabolic syndrome. Methods: Secondary data pertaining to 309 subjects (85 men and 224 women) were collected from participants in exercise programs at a health center in a suburban area. Muscle mass was measured using bioelectrical impedance analysis, and muscle strength was measured via handgrip strength. Sarcopenia based on muscle mass alone was defined as a weight-adjusted skeletal muscle mass index more than two standard deviations below the mean of a sex-specific young reference group (class II sarcopenia). Two cut-off values for low handgrip strength were used: the first criteria were <26 kg for men and <18 kg for women, and the second criteria were the lowest quintile of handgrip strength among the study subjects. Sarcopenic obesity was defined as the combination of class II sarcopenia and being in the two highest quintiles of total body fat percentage among the subjects. The associations of sarcopenia and sarcopenic obesity with metabolic syndrome were evaluated using logistic regression models. Results: The age-adjusted risk ratios (RRs) of metabolic syndrome being compared in people with or without sarcopenia defined in terms of muscle mass were 1.25 (95% confidence interval [CI], 1.06 to 1.47, p=0.008) in men and 1.12 (95% CI, 1.06 to 1.19, p<0.001) in women, which were found to be statistically significant relationships. The RRs of metabolic syndrome being compared in people with or without sarcopenic obesity were 1.31 in men (95% CI, 1.10 to 1.56, p=0.003) and 1.17 in women (95% CI, 1.10 to 1.25, p<0.001), which were likewise found to be statistically significant relationships. Conclusions: The associations of sarcopenia defined in terms of muscle mass and sarcopenic obesity with metabolic syndrome were statistically significant in both men and women. Therefore, sarcopenia and sarcopenic obesity must be

  6. The effect of muscle fatigue on position sense in an upper limb multi-joint task.

    PubMed

    Vafadar, Amirhossein K; Côté, Julie N; Archambault, Philippe S

    2012-04-01

    The purpose of this study was to estimate the extent to which muscle fatigue can impact on the position sense in the upper limb. Twelve healthy volunteers were asked to do a reaching task while grasping a wooden block and match the block's position with a corresponding target displayed on a flat screen, without vision. Following that, subjects performed resistive exercises with Thera-band strips until fatigue was induced and then the position sense task was repeated. A significant change in the endpoint position was observed after fatigue, in the up/down direction (p ≤ .001). The variability of endpoint positions in up/down direction was also significantly increased after fatigue (p ≤.03). There was no significant change in endpoint orientation but there was a significant fatigue × orientation effect on endpoint rotational variability. In a follow-up experiment, a group of subjects repeated the same protocol, but with a period of quiet rest between the two position sense tasks. In that group, there were no differences in endpoint position, orientation or variability. Muscle fatigue is an important factor that should be taken into consideration during the treatment of musculoskeletal injuries as well as athletic training. PMID:22357216

  7. The effect of muscle fatigue on instep kicking kinetics and kinematics in association football.

    PubMed

    Apriantono, Tommy; Nunome, Hiroyuki; Ikegami, Yasuo; Sano, Shinya

    2006-09-01

    The aim of this study was to examine the effect of leg muscle fatigue on the kinetics and kinematics of the instep football kick. Fatigue was induced by repeated, loaded knee extension (40% body weight) and flexion (50% body weight) motions on a weight-training machine until exhaustion. The kicking motions of seven male players were captured three-dimensionally at 500 Hz before and immediately after the fatigue protocol. The significantly slower ball velocity observed in the fatigue condition was due to both reduced lower leg swing speed and poorer ball contact. The reduced leg swing speed, represented by a slower toe linear velocity immediately before ball impact and slower peak lower leg angular velocity, was most likely due to a significantly reduced resultant joint moment and motion-dependent interactive moment during kicking. These results suggest that the specific muscle fatigue induced in the present study not only diminished the ability to generate force, but also disturbed the effective action of the interactive moment leading to poorer inter-segmental coordination during kicking. Moreover, fatigue obscured the eccentric action of the knee flexors immediately before ball impact. This might increase the susceptibility to injury. PMID:16882629

  8. Potential of M-Wave Elicited by Double Pulse for Muscle Fatigue Evaluation in Intermittent Muscle Activation by Functional Electrical Stimulation for Motor Rehabilitation

    PubMed Central

    Miura, Naoto; Watanabe, Takashi

    2016-01-01

    Clinical studies on application of functional electrical stimulation (FES) to motor rehabilitation have been increasing. However, muscle fatigue appears early in the course of repetitive movement production training by FES. Although M-wave variables were suggested to be reliable indices of muscle fatigue in long lasting constant electrical stimulation under the isometric condition, the ability of M-wave needs more studies under intermittent stimulation condition, because the intervals between electrical stimulations help recovery of muscle activation level. In this paper, M-waves elicited by double pulses were examined in muscle fatigue evaluation during repetitive movements considering rehabilitation training with surface electrical stimulation. M-waves were measured under the two conditions of repetitive stimulation: knee extension force production under the isometric condition and the dynamic movement condition by knee joint angle control. Amplitude of M-wave elicited by the 2nd pulse of a double pulse decreased during muscle fatigue in both measurement conditions, while the change in M-waves elicited by single pulses in a stimulation burst was not relevant to muscle fatigue in repeated activation with stimulation interval of 1 s. Fatigue index obtained from M-waves elicited by 2nd pulses was suggested to provide good estimation of muscle fatigue during repetitive movements with FES. PMID:27110556

  9. 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.

  10. Blood flow restricted and traditional resistance training performed to fatigue produce equal muscle hypertrophy.

    PubMed

    Farup, J; de Paoli, F; Bjerg, K; Riis, S; Ringgard, S; Vissing, K

    2015-12-01

    This study investigated the hypertrophic potential of load-matched blood-flow restricted resistance training (BFR) vs free-flow traditional resistance training (low-load TRT) performed to fatigue. Ten healthy young subjects performed unilateral BFR and contralateral low-load TRT elbow flexor dumbbell curl with 40% of one repetition maximum until volitional concentric failure 3 days per week for 6 weeks. Prior to and at 3 (post-3) and 10 (post-10) days post-training, magnetic resonance imaging (MRI) was used to estimate elbow flexor muscle volume and muscle water content accumulation through training. Acute changes in muscle thickness following an early vs a late exercise bout were measured with ultrasound to determine muscle swelling during the immediate 0-48 h post-exercise. Total work was threefold lower for BFR compared with low-load TRT (P < 0.001). Both BRF and low-load TRT increased muscle volume by approximately 12% at post-3 and post-10 (P < 0.01) with no changes in MRI-determined water content. Training increased muscle thickness during the immediate 48 h post-exercise (P < 0.001) and to greater extent with BRF (P < 0.05) in the early training phase. In conclusion, BFR and low-load TRT, when performed to fatigue, produce equal muscle hypertrophy, which may partly rely on transient exercise-induced increases in muscle water content. PMID:25603897

  11. Direct and indirect measurements relevant to the assessment of fatigue of the respiratory muscles - review

    NASA Astrophysics Data System (ADS)

    Kuraszkiewicz, Bożena

    2011-01-01

    The purpose of this review is to present selected tests available with the potential to detect the development of respiratory muscle fatigue in normal subjects and patients. All reviewed techniques represent a part of a variety of measures and indices, which have been employed to assess this complex process at the present time.

  12. Muscle Fatigue during Intermittent Exercise in Individuals with Mental Retardation

    ERIC Educational Resources Information Center

    Zafeiridis, Andreas; Giagazoglou, Paraskevi; Dipla, Konstantina; Salonikidis, Konstantinos; Karra, Chrisanthi; Kellis, Eleftherios

    2010-01-01

    This study examined fatigue profile during intermittent exercise in 10 men with mild to moderate mental retardation (MR) and 10 men without mental retardation (C). They performed 4 x 30 s maximal knee extensions and flexions with 1-min rest on an isokinetic dynamometer. Peak torque of flexors (PTFL) and extensors (PTEX), total work (TW), and…

  13. Vitamin D and skeletal muscle strength and endurance in COPD.

    PubMed

    Jackson, Abigail S; Shrikrishna, Dinesh; Kelly, Julia L; Kemp, Samuel V; Hart, Nicholas; Moxham, John; Polkey, Michael I; Kemp, Paul; Hopkinson, Nicholas S

    2013-02-01

    It is not known whether vitamin D levels make a significant contribution to muscle dysfunction in chronic obstructive pulmonary disease (COPD). In 104 COPD patients (mean±sd forced expiratory volume in 1 s 44±22 % predicted) and 100 age- and sex-matched controls, serum 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)(2)D) and parathyroid hormone (PTH) levels were measured and related to quadriceps strength and endurance. In a subset of 26 patients and 13 controls, quadriceps biopsy was performed and mRNA expression of myogenic regulatory factors (mrf) and fibre-specific myosin heavy chains (MHC) was determined. COPD patients were weaker and less physically active than controls. 25(OH)D levels were similar in both groups (48.5±25.5 nmol·L(-1) COPD versus 55.4±28.3 nmol·L(-1) control, p=0.07) but PTH levels were significantly higher in patients (5.2±2.3 pmol·mL(-1) versus 4.4±2.0 pmol·L(-1), p=0.01). 1,25(OH)D was significantly correlated with strength in controls, but not in COPD patients and not with quadriceps endurance assessed using repetitive magnetic stimulation in COPD (n=35) or control (n=35) subjects. In controls, but not COPD patients, muscle biopsy analysis showed a negative relationship between 25(OH)D and MHCIIa expression (r(2)=0.5, p=0.01) and a positive relationship between mrf4 and MHCIIa expression (r(2)=0.5, p=0.009), and myogenic regulatory factor myf5 and MHCI expression (r(2)=0.72, p=0.004). In contrast with healthy controls, muscle strength is not associated with vitamin D levels in COPD, which may represent vitamin D resistance. PMID:22556020

  14. Set Configuration in Resistance Exercise: Muscle Fatigue and Cardiovascular Effects

    PubMed Central

    Río-Rodríguez, Dan; Iglesias-Soler, Eliseo; Fernández del Olmo, Miguel

    2016-01-01

    Purpose Cardiovascular responses of traditional resistance (TS) training have been extensively explored. However, the fatigue mechanisms associated with an intra-set rest configuration (ISR) have not been investigated. This study compares two modalities of set configurations for resistance exercise that equates work to rest ratios and measures the central and peripheral fatigue in combination with cortical, hemodynamic and cardiovascular measures. Methods 11 subjects performed two isometric knee extension training sessions using TS and ISR configurations. Voluntary activation (VA), single twitch amplitude, low frequency fatigue (LFF), Mwave, motor evoked potential (MEP), short intracortical inhibition (SICI), intracortical facilitation (ICF) and heart rate variability were evaluated before and after each training session. During each session beat to beat heart rate, blood pressure and rate pressure product (RPP) were also evaluated. Results After exercise VA decreased significantly for TS but not for ISR (P < 0.001), single twitch amplitude and LFF values were lower for TS than ISR (P < 0.004), and SICI was reduced only for the TS configuration (P = 0.049). During exercise RPP values were significantly higher for the TS than for ISR (P = 0.001). RPP correlated with VA for TS (r = -.85 P < 0.001) suggesting a relationship between central fatigue and cardiovascular stress. Conclusions We conclude that ISR induced lower central and peripheral fatigue as well as lower cardiovascular stress in comparison with TS configuration. Our study suggests that set configuration is a key factor in the regulation of the neuromuscular and cardiovascular responses of resistance training. PMID:26982500

  15. The impact of obesity on skeletal muscle strength and structure through adolescence to old age.

    PubMed

    Tomlinson, D J; Erskine, R M; Morse, C I; Winwood, K; Onambélé-Pearson, Gladys

    2016-06-01

    Obesity is associated with functional limitations in muscle performance and increased likelihood of developing a functional disability such as mobility, strength, postural and dynamic balance limitations. The consensus is that obese individuals, regardless of age, have a greater absolute maximum muscle strength compared to non-obese persons, suggesting that increased adiposity acts as a chronic overload stimulus on the antigravity muscles (e.g., quadriceps and calf), thus increasing muscle size and strength. However, when maximum muscular strength is normalised to body mass, obese individuals appear weaker. This relative weakness may be caused by reduced mobility, neural adaptations and changes in muscle morphology. Discrepancies in the literature remain for maximal strength normalised to muscle mass (muscle quality) and can potentially be explained through accounting for the measurement protocol contributing to muscle strength capacity that need to be explored in more depth such as antagonist muscle co-activation, muscle architecture, a criterion valid measurement of muscle size and an accurate measurement of physical activity levels. Current evidence demonstrating the effect of obesity on muscle quality is limited. These factors not being recorded in some of the existing literature suggest a potential underestimation of muscle force either in terms of absolute force production or relative to muscle mass; thus the true effect of obesity upon skeletal muscle size, structure and function, including any interactions with ageing effects, remains to be elucidated. PMID:26667010

  16. 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.

  17. 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.

  18. Modeling the Tensile Strength of Carbon Fiber - Reinforced Ceramic - Matrix Composites Under Multiple Fatigue Loading

    NASA Astrophysics Data System (ADS)

    Li, Longbiao

    2015-09-01

    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.

  19. 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.

  20. Analysis of methods for determining high cycle fatigue strength of a material with investigation of titanium-aluminum-vanadium gigacycle fatigue behavior

    NASA Astrophysics Data System (ADS)

    Pollak, Randall D.

    Today, aerospace engineers still grapple with the qualitative and quantitative understanding of fatigue behavior in the design and testing of turbine-driven jet engines. The Department of Defense has taken a very active role in addressing this problem with the formation of the National High Cycle Fatigue Science & Technology Program in 1994. The primary goal of this program is to further the understanding of high cycle fatigue (HCF) behavior and develop methods in order to mitigate the negative impact of HCF on aerospace operations. This research supports this program by addressing the fatigue strength testing guidance currently provided by the DoD to engine manufacturers, with the primary goal to investigate current methods and recommend a test strategy to characterize the fatigue strength of a material at a specified number of cycles, such as the 109 design goal specified by MIL-HDBK-1783B, or range of cycles. The research utilized the benefits of numerical simulation to initially investigate the staircase method for use in fatigue strength testing. The staircase method is a commonly used fatigue strength test, but its ability to characterize fatigue strength variability is extremely suspect. A modified staircase approach was developed and shown to significantly reduce bias and scatter in estimates for fatigue strength variance. Experimental validation of this proposed test strategy was accomplished using a dual-phase Ti-6Al-4V alloy. The HCF behavior of a second material with a very different microstructure (beta annealed Ti-6Al-4V) was also investigated. The random fatigue limit (RFL) model, a recently developed analysis tool, was investigated to characterize stress-life behavior but found to have difficulty representing fatigue life curves with sharp transitions. Two alternative models (bilinear and hyperbolic) were developed based on maximum likelihood methods to better characterize the Ti-6Al-4V fatigue life behavior. These models provided a good fit to the

  1. Mechanical surface treatments of lightweight materials -- effects on fatigue strength and near-surface microstructures

    SciTech Connect

    Zinn, W.; Scholtes, B.

    1999-04-01

    Mechanical surface treatments such as shot peening or deep rolling are well-known processes to improve the fatigue strength of metallic components. This is due to favorable microstructural alterations in relatively thin surface layers as a consequence of near-surface inhomogeneous plastic deformations. Typical examples demonstrate the fatigue-strength increase for mechanically surface-treated specimens. Existing possibilities to improve the fatigue strength of welded joints by mechanical surface treatments are also included. In the case of lightweight materials (e.g., magnesium- or aluminum-base alloys), process parameters must be well adapted in individual cases to achieve optimum near-surface material states, taking into account the wide range of mechanical properties attainable as a result of their specific material microstructure. The effects of process parameters and microstructures on near-surface materials properties resulting from mechanical surface treatments are demonstrated with examples. Depth distributions of macroresidual and microresidual stresses are analyzed together with microstructural observations. An important point for the effectiveness of mechanical surface treatments is the stability of the near-surface material states during loading history. This aspect is treated for the case of fatigue loading.

  2. Sniff and Muller manoeuvres to measure diaphragmatic muscle strength.

    PubMed

    Prigent, Hélène; Orlikowski, David; Fermanian, Christophe; Lejaille, Michèle; Falaize, Line; Louis, Alain; Fauroux, Brigitte; Lofaso, Frédéric

    2008-12-01

    We hypothesized that peak values of oesophageal (Poes) and transdiaphragmatic pressure (Pdi) swings during a maximal sniff manoeuvre and a maximal static inspiratory manoeuvre (Muller manoeuvre) are comparable or give complementary information for assessing diaphragmatic and global inspiratory muscle strength. We studied 98 patients with suspected diaphragmatic dysfunction. Poes and Pdi swings were measured during maximal sniff manoeuvres (sniff), maximal Muller manoeuvres (max), and cervical magnetic phrenic nerve stimulation (cervical Tw). Eighty eight patients were able to perform both volitional manoeuvres. Among them, mean Poes sniff was significantly higher than mean Poes max (48.7+/-28.7 cm H(2)O vs. 42.9+/-27.4 cm H(2)O, p<0.05) and mean Pdi sniff was higher than mean Pdi max (49.2+/-35.1cm H(2)O vs. 42.9+/-33.3 cm H(2)O, respectively, p=0.05). Cervical Pdi Tw correlated better with Pdi sniff (p<0.0001, r=0.62) than with Pdi max (p<0.0001, r=0.44). Poes and Pdi swings were greatest during the sniff manoeuvre in 42 patients (48%) and during the Muller manoeuvre in 29 patients (33%). Among the 17 remaining patients, nine had the greatest Poes swing during a maximal sniff manoeuvre and the greatest Pdi swing during a maximal static inspiratory manoeuvre; the opposite occurred in the other eight patients. The combination of Muller manoeuvre and sniff manoeuvre increased the diagnosis of normal diaphragmatic strength from 18 patients (20%) to 21 patients (24%), and the additional analysis of cervical Pdi Tw further increased the diagnosis of normal diaphragmatic strength to 27 patients (31%). In conclusion, though sniff manoeuvre gave significantly higher values than Muller manoeuvre, both volitional manoeuvres and cervical Pdi Tw are complementary and should be used in combination to evaluate diaphragmatic muscle strength. PMID:18708281

  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. Effects of prolonged gum chewing on pain and fatigue in human jaw muscles.

    PubMed

    Farella, M; Bakke, M; Michelotti, A; Martina, R

    2001-04-01

    Gum chewing has been accepted as an adjunct to oral hygiene, as salivary stimulant and vehicle for various agents, as well as for jaw muscle training. The aim of this study was to investigate the effects of prolonged gum chewing on pain, fatigue and pressure tenderness of the masticatory muscles. Fifteen women without temporomandibular disorders (TMD) were requested to perform one of the following chewing tasks in three separate sessions: chewing a very hard gum, chewing a soft gum, and empty-chewing with no bolus. Unilateral chewing of gum or empty chewing was performed for 40 min at a constant rate of 80 cycles/min. In each session, perceived muscle pain and masticatory fatigue were rated on visual analog scales (VAS) before, throughout, and after the chewing task. Pressure pain thresholds (PPTs) of masseter and anterior temporalis muscles were assessed before and immediately after the chewing tasks, and again after 24 h. The VAS scores for pain and fatigue significantly increased only during the hard gum chewing, and after 10 min of recovery VAS scores had decreased again, almost to their baseline values. No significant changes were found for PPTs either after hard or soft gum chewing. The findings indicate that the jaw muscles recover quickly from prolonged chewing activity in subjects without TMD. PMID:11347660

  6. Movement-related cortical potentials during muscle fatigue induced by upper limb submaximal isometric contractions.

    PubMed

    Guo, Feng; Wang, Ji-Ya; Sun, Yong-Jun; Yang, A-Li; Zhang, Ri-Hui

    2014-10-01

    The aim of this study was to examine the central neurophysiological mechanisms during fatigue induced by submaximal isometric contractions. A total of 23 individuals participated in the study and were assigned to fatigue and nonfatigue groups. Handgrip force, root mean square (RMS) of surface electromyography (sEMG) signal and movement-related cortical potentials during self-paced submaximal handgrip isometric contractions were assessed for each participant. The experimental data showed significant decreases in both maximal voluntary contraction [-24.3%; F(3, 42)=19.62, P<0.001, ηp=0.48] and RMS [-30.1%; F(3, 42)=19.01, P<0.001, ηp=0.57] during maximal voluntary contractions and a significant increase [F(3, 42)=14.27, P<0.001, ηp=0.50] in the average RMS of sEMG over four blocks in the fatigue group. There was no significant difference in the readiness potential between the fatigue and the nonfatigue groups at early stages, and at late stages, significant differences were observed only at the Fp1 and FC1 sites. Motor potential amplitudes were significantly higher in the fatigue group than in the nonfatigue group irrespective of block or electrode positions. Positive waveforms were observed in the prefrontal cortex in states without muscle fatigue, whereas a negative waveform pattern was observed with muscle fatigue. Significant within-subject correlations were observed between motor potential at the C1 site and RMS of sEMG (r=-0.439, P=0.02, ηp=0.11). Neurophysiological evidence indicates that cortical activity increases in the prefrontal cortex, primary motor cortex and supplementary motor cortex with muscle fatigue. Muscle fatigue appears to have considerable effects on the components of movement-related cortical potentials during movement execution, whereas the readiness potential before movement is sensitive to cognitive demands during prolonged exercise. Our results provide additional evidence for a link between central motor command during movement

  7. The effect of sustained low-intensity contractions on supraspinal fatigue in human elbow flexor muscles

    PubMed Central

    Søgaard, Karen; Gandevia, Simon C; Todd, Gabrielle; Petersen, Nicolas T; Taylor, Janet L

    2006-01-01

    Subjects quickly fatigue when they perform maximal voluntary contractions (MVCs). Much of the loss of force is from processes within muscle (peripheral fatigue) but some occurs because voluntary activation of the muscle declines (central fatigue). The role of central fatigue during submaximal contractions is not clear. This study investigated whether central fatigue developed during prolonged low-force voluntary contractions. Subjects (n = 9) held isometric elbow flexions of 15% MVC for 43 min. Voluntary activation was measured during brief MVCs every 3 min. During each MVC, transcranial magnetic stimulation (TMS) was followed by stimulation of either brachial plexus or the motor nerve of biceps brachii. After nerve stimulation, a resting twitch was also evoked before subjects resumed the 15% MVC. Perceived effort, elbow flexion torque and surface EMG from biceps, brachioradialis and triceps were recorded. TMS was also given during the sustained 15% MVC. During the sustained contraction, perceived effort rose from ∼2 to ∼8 (out of 10) while ongoing biceps EMG increased from 6.9 ± 2.1% to 20.0 ± 7.8% of initial maximum. Torque in the brief MVCs and the resting twitch fell to 58.6 ± 14.5 and 58.2 ± 13.2% of control values, respectively. EMG in the MVCs also fell to 62.2 ± 15.3% of initial maximum, and twitches evoked by nerve stimulation and TMS grew progressively. Voluntary activation calculated from these twitches fell from ∼98% to 71.9 ± 38.9 and 76.9 ± 18.3%, respectively. The silent period following TMS lengthened both in the brief MVCs (by ∼40 ms) and in the sustained target contraction (by ∼18 ms). After the end of the sustained contraction, the silent period recovered immediately, voluntary activation and voluntary EMG recovered over several minutes while MVC torque only returned to ∼85% baseline. The resting twitch showed no recovery. Thus, as well as fatigue in the muscle, the prolonged low-force contraction produced progressive central

  8. Loading frequencies up to 20Hz as an alternative to accelerate fatigue strength tests in a Y-TZP ceramic.

    PubMed

    Fraga, Sara; Pereira, Gabriel Kalil Rocha; Freitas, Mariana; Kleverlaan, Cornelis Johannes; Valandro, Luiz Felipe; May, Liliana Gressler

    2016-08-01

    Considering the interest of the research community in the fatigue behavior of all-ceramic restorations and the time consumed in low-frequency cyclic fatigue tests, this study aimed to investigate the influence of the loading frequency on the zirconia fatigue strength. The biaxial flexural fatigue strength of Y-TZP discs was determined by the staircase approach after 500,000 cycles. The investigated frequencies were 2Hz (control-simulation of the chewing activity; n=20), 10Hz (n=20), 20Hz (n=20), and 40Hz (n=21). The fatigue strength data were analyzed using one-way ANOVA and post-hoc Tukey׳s test (α=0.05). Pearson coefficient (r) was calculated to assess the existence of a correlation between fatigue strength and loading frequency. X-ray diffraction analysis was used to determine the relative amount of monoclinic phase under each fatigue test condition. The fatigue strength was significantly higher for 40Hz group (630.7±62.1MPa) and did not differ among the groups 2Hz (550.3±89.7MPa), 10Hz (574.0±47MPa) and 20Hz (605.1±30.7MPa). Pearson correlation coefficient indicated a significantly moderate correlation (r=0.57) between fatigue strength and loading frequency. The percentage of monoclinic phase was similar among the groups. Therefore, the use of loading frequencies up to 20Hz seems a good alternative to expedite the cycling strength fatigue tests in polycrystalline ceramics without significantly changing the fatigue behavior showed by zirconia in tests employing the frequency of the masticatory cycle. PMID:26849030

  9. Postviral fatigue syndrome: persistence of enterovirus RNA in muscle and elevated creatine kinase.

    PubMed Central

    Archard, L C; Bowles, N E; Behan, P O; Bell, E J; Doyle, D

    1988-01-01

    Enterovirus-specific probes have been prepared by reverse transcription of conserved sequences in purified Coxsackie B2 virus genomic RNA and molecular cloning techniques. These probes were used in quantitative slot blot hybridizations to test for the presence of enterovirus-specific RNA in skeletal muscle biopsy specimens from 96 patients who had suffered from the postviral fatigue syndrome myalgic encephalomyelitis for up to 20 years. Biopsy specimens from 20 patients were positive for the presence of virus-specific RNA with hybridization signals more than three standard deviations greater than the mean of the normal muscle controls. Biopsies from the remaining 76 patients were indistinguishable from the controls. These data show that enterovirus RNA is present in skeletal muscle of some patients with postviral fatigue syndrome up to 20 years after onset of disease and suggest that a persistent virus infection has an aetiological role. PMID:3404526

  10. Static and Fatigue Strength Evaluations for Bolted Composite/Steel Joints for Heavy Vehicle Chassis Components

    SciTech Connect

    Sun, Xin; Stephens, Elizabeth V.; Herling, Darrell R.

    2004-09-14

    In May 2003, ORNL and PNNL began collaboration on a four year research effort focused on developing joining techniques to overcome the technical issues associated with joining lightweight materials in heavy vehicles. The initial focus of research is the development and validation of joint designs for a composite structural member attached to a metal member that satisfy the structural requirements both economically and reliably. Huck-bolting is a common joining method currently used in heavy truck chassis structures. The initial round of testing was conducted to establish a performance benchmark by evaluating the static and fatigue behavior of an existing steel/steel chassis joint at the single huck-bolt level. Both tension and shear loading conditions were considered, and the resulting static and fatigue strengths will be used to guide the joint design for a replacement composite/steel joint. A commercially available, pultruded composite material was chosen to study the generic issues related to composite/steel joints. Extren is produced by STRONGWELL, and it is a combination of fiberglass reinforcement and thermosetting polyester or vinyl ester resin systems. Extren sheets of 3.2 mm thick were joined to 1.4 mm SAE1008 steel sheets with a standard grade 5 bolt with 6.35 mm diameter. Both tension and shear loading modes were considered for the single hybrid joint under static and fatigue loading conditions. Since fiberglass reinforced thermoset polymer composites are a non-homogenous material, their strengths and behavior are dependent upon the design of the composite and reinforcement. The Extren sheet stock was cut along the longitudinal direction to achieve maximum net-section strength. The effects of various manufacturing factors and operational conditions on the static and fatigue strength of the hybrid joint were modeled and experimentally verified. It was found that loading mode and washer size have significant influence on the static and fatigue strength of

  11. Towards smart prosthetic hand: Adaptive probability based skeletan muscle fatigue model.

    PubMed

    Kumar, Parmod; Sebastian, Anish; Potluri, Chandrasekhar; Urfer, Alex; Naidu, D; Schoen, Marco P

    2010-01-01

    Skeletal muscle force can be estimated using surface electromyographic (sEMG) signals. Usually, the surface location for the sensors is near the respective muscle motor unit points. Skeletal muscles generate a spatial EMG signal, which causes cross talk between different sEMG signal sensors. In this study, an array of three sEMG sensors is used to capture the information of muscle dynamics in terms of sEMG signals. The recorded sEMG signals are filtered utilizing optimized nonlinear Half-Gaussian Bayesian filters parameters, and the muscle force signal using a Chebyshev type-II filter. The filter optimization is accomplished using Genetic Algorithms. Three discrete time state-space muscle fatigue models are obtained using system identification and modal transformation for three sets of sensors for single motor unit. The outputs of these three muscle fatigue models are fused with a probabilistic Kullback Information Criterion (KIC) for model selection. The final fused output is estimated with an adaptive probability of KIC, which provides improved force estimates. PMID:21095927

  12. Shoulder External Rotation Fatigue and Scapular Muscle Activation and Kinematics in Overhead Athletes

    PubMed Central

    Joshi, Mithun; Thigpen, Charles A.; Bunn, Kevin; Karas, Spero G.; Padua, Darin A.

    2011-01-01

    Context: Glenohumeral external rotation (GH ER) muscle fatigue might contribute to shoulder injuries in overhead athletes. Few researchers have examined the effect of such fatigue on scapular kinematics and muscle activation during a functional movement pattern. Objective: To examine the effects of GH ER muscle fatigue on upper trapezius, lower trapezius, serratus anterior, and infraspinatus muscle activation and to examine scapular kinematics during a diagonal movement task in overhead athletes. Setting: Human performance research laboratory. Design: Descriptive laboratory study. Patients or Other Participants: Our study included 25 overhead athletes (15 men, 10 women; age = 20 ± 2 years, height = 180 ± 11 cm, mass = 80 ± 11 kg) without a history of shoulder pain on the dominant side. Interventions: We tested the healthy, dominant shoulder through a diagonal movement task before and after a fatiguing exercise involving low-resistance, high-repetition, prone GH ER from 0° to 75° with the shoulder in 90° of abduction. Main Outcome Measure(s): Surface electromyography was used to measure muscle activity for the upper trapezius, lower trapezius, serratus anterior, and infraspinatus. An electromyographic motion analysis system was used to assess 3-dimensional scapular kinematics. Repeated-measures analyses of variance (phase × condition) were used to test for differences. Results: We found a decrease in ascending-phase and descending-phase lower trapezius activity (F1,25 = 5.098, P = .03) and an increase in descending-phase infraspinatus activity (F1,25 = 5.534, P = .03) after the fatigue protocol. We also found an increase in scapular upward rotation (F1,24 = 3.7, P = .04) postfatigue. Conclusions: The GH ER muscle fatigue protocol used in this study caused decreased lower trapezius and increased infraspinatus activation concurrent with increased scapular upward rotation range of motion during the functional task. This highlights the interdependence of scapular

  13. Factors affecting isokinetic muscle strength before and after anterior cruciate ligament reconstruction.

    PubMed

    Yüksel, Halil Yalçin; Erkan, Serkan; Uzun, Macit

    2011-06-01

    The purpose of this study was to evaluate the factors affecting muscle strength of ACL-deficient knees before and after ACL reconstruction. The study included 122 male patients who underwent primary ACL reconstruction with a bone-patellar tendon-bone autograft. Preoperative loss and change in muscle strength in both extensor and flexor muscle groups after ACL reconstruction were calculated separately at 60 degrees/sec and 180 degrees/sec angular velocities. We evaluated the effect of surgical delay on the preoperative deficit and on its change after surgery. Muscle strength change after ACL reconstruction was also evaluated in relation to patient compliance to treatment. The longer the delay of ACL reconstruction the more the muscle strength deficit of flexor and extensor muscles increased. In the ACL deficient knees with high strength deficit, improvement in muscle strength was higher after ACL reconstruction for both muscle groups. When delay of ACL reconstruction was short and the patient was compliant to treatment, flexor muscle strength recovery was early. Shortening the delay to reconstruction had a positive influence on muscle strength after ACL reconstruction when preoperative muscle strength deficit was high. PMID:21846002

  14. Relationship Between Respiratory Muscle Strength and Conventional Sarcopenic Indices in Young Adults: A Preliminary Study

    PubMed Central

    Ro, Hee Joon; Lee, Sang Yoon; Seo, Kyung Mook; Kang, Si Hyun; Suh, Hoon Chang

    2015-01-01

    Objective To investigate the relationships between respiratory muscle strength and conventional sarcopenic indices such as skeletal muscle mass and limb muscle strength. Methods Eighty-nine young adult volunteers who had no history of medical or musculoskeletal disease were enrolled. Skeletal muscle mass was measured by bioelectrical impedance analysis and expressed as a skeletal muscle mass index (SMI). Upper and lower limb muscle strength were evaluated by hand grip strength (HGS) and isometric knee extensor muscle strength, respectively. Peak expiratory flow (PEF), maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP) were evaluated using a spirometer to demonstrate respiratory muscle strength. The relationships between respiratory muscle strength and sarcopenic indices were investigated using Pearson correlation coefficients and multiple linear regression analysis adjusted by age, height, and body mass index. Results MIP showed positive correlations with SMI (r=0.457 in men, r=0.646 in women; both p<0.01). MIP also correlated with knee extensor strength (p<0.01 in both sexes) and HGS (p<0.05 in men, p<0.01 in women). However, PEF and MEP had no significant correlations with these sarcopenic variables. In multivariate regression analysis, MIP was the only independent factor related to SMI (p<0.01). Conclusion Among the respiratory muscle strength variables, MIP was the only value associated with skeletal muscle mass. PMID:26798601

  15. Effects of Cold Water Immersion on Muscle Oxygenation During Repeated Bouts of Fatiguing Exercise

    PubMed Central

    Yeung, Simon S.; Ting, Kin Hung; Hon, Maurice; Fung, Natalie Y.; Choi, Manfi M.; Cheng, Juno C.; Yeung, Ella W.

    2016-01-01

    Abstract Postexercise cold water immersion has been advocated to athletes as a means of accelerating recovery and improving performance. Given the effects of cold water immersion on blood flow, evaluating in vivo changes in tissue oxygenation during cold water immersion may help further our understanding of this recovery modality. This study aimed to investigate the effects of cold water immersion on muscle oxygenation and performance during repeated bouts of fatiguing exercise in a group of healthy young adults. Twenty healthy subjects performed 2 fatiguing bouts of maximal dynamic knee extension and flexion contractions both concentrically on an isokinetic dynamometer with a 10-min recovery period in between. Subjects were randomly assigned to either a cold water immersion (treatment) or passive recovery (control) group. Changes in muscle oxygenation were monitored continuously using near-infrared spectroscopy. Muscle performance was measured with isokinetic dynamometry during each fatiguing bout. Skin temperature, heart rate, blood pressure, and muscle soreness ratings were also assessed. Repeated measures ANOVA analysis was used to evaluate treatment effects. The treatment group had a significantly lower mean heart rate and lower skin temperature compared to the control group (P < 0.05). Cold water immersion attenuated a reduction in tissue oxygenation in the second fatiguing bout by 4% when compared with control. Muscle soreness was rated lower 1 day post-testing (P < 0.05). However, cold water immersion had no significant effect on muscle performance in subsequent exercise. As the results show that cold water immersion attenuated decreased tissue oxygenation in subsequent exercise performance, the metabolic response to exercise after cold water immersion is worthy of further exploration. PMID:26735552

  16. Traditional versus functional strength training: effects on muscle strength and power in the elderly.

    PubMed

    Lohne-Seiler, Hilde; Torstveit, Monica K; Anderssen, Sigmund A

    2013-01-01

    The aim was to determine whether strength training with machines vs. functional strength training at 80% of one-repetition maximum improves muscle strength and power among the elderly. Sixty-three subjects (69.9 ± 4.1 yr) were randomized to a high-power strength group (HPSG), a functional strength group (FSG), or a nonrandomized control group (CG). Data were collected using a force platform and linear encoder. The training dose was 2 times/wk, 3 sets × 8 reps, for 11 wk. There were no differences in effect between HPSG and FSG concerning sit-to-stand power, box-lift power, and bench-press maximum force. Leg-press maximum force improved in HPSG (19.8%) and FSG (19.7%) compared with CG (4.3%; p = .026). Bench-press power improved in HPSG (25.1%) compared with FSG (0.5%, p = .02) and CG (2%, p = .04). Except for bench-press power there were no differences in the effect of the training interventions on functional power and maximal body strength. PMID:22832419

  17. Strength, fracture, and fatigue behavior of advanced high-temperature intermetallics reinforced with ductile phases

    NASA Astrophysics Data System (ADS)

    Soboyejo, W. O.; Rao, K. T. Venkateswara; Sastry, S. M. L.; Ritchie, R. O.

    1993-03-01

    The results of recent studies on the fatigue and fracture behavior of extruded Ti-48A1 + 20 vol pct TiNb and hot-isostatically pressed (“hipped”) MoSi2 + 20 vol pct Nb are presented (compositions in atomic percent unless stated otherwise). The effects of ductile phase reinforcement of Ti-48A1 and MoSi2 on the micromechanisms of fracture under monotonie and cyclic loading are elucidated. Micromechanics models are applied to the prediction of crack-tip shielding components, and the effects of temperature on tensile/compressive/flexure strengths are discussed. Ductile phase toughening under monotonie loading conditions is shown to be associated with lower fatigue crack growth resistance. The lower fatigue resistance is attributed to the absence of crack-tip shielding, higher crack opening displacements, and the effects of inelastic strains that are developed in ductile phase-reinforced composites under cyclic loading conditions.

  18. Mechanisms underlying reduced maximum shortening velocity during fatigue of intact, single fibres of mouse muscle

    PubMed Central

    Westerblad, Håkan; Dahlstedt, Anders J; Lännergren, Jan

    1998-01-01

    The mechanism behind the reduction in shortening velocity in skeletal muscle fatigue is unclear. In the present study we have measured the maximum shortening velocity (V0) with slack tests during fatigue produced by repeated, 350 ms tetani in intact, single muscle fibres from the mouse. We have focused on two possible mechanisms behind the reduction in V0: reduced tetanic Ca2+ and accumulation of ADP. During fatigue V0 initially declined slowly, reaching 90 % of the control after about forty tetani. The rate of decline then increased and V0 fell to 70 % of the control in an additional twenty tetani. The reduction in isometric force followed a similar pattern. Exposing unfatigued fibres to 10 μM dantrolene, which reduces tetanic Ca2+, lowered force by about 35 % but had no effect on V0. In order to see if ADP might increase rapidly during ongoing contractions, we used a protocol with a tetanus of longer duration bracketed by standard-duration tetani. V0 in these three tetani were not significantly different in control, whereas V0 was markedly lower in the longer tetanus during fatigue and in unfatigued fibres where the creatine kinase reaction was inhibited by 10 μM dinitrofluorobenzene. We conclude that the reduction in V0 during fatigue is mainly due to a transient accumulation of ADP, which develops during contractions in fibres with impaired phosphocreatine energy buffering. PMID:9625883

  19. Strength distribution of fatigue crack initiation sites in an Al-Li alloy

    NASA Astrophysics Data System (ADS)

    Zhai, T.

    2006-10-01

    The stress-number of cycles to failure (S-N) curves were measured along the short-transverse (S) and rolling (L) directions of a hot-cross-rolled AA 8090 Al-Li alloy plate (45-mm thick). The alloy was solution heat treated, quenched in water, strained by 6 pct, and peak aged. Fatigue tests were carried out in four-point bend at room temperature, 20 Hz, R=0.1, in air. It was found that the fatigue limits in the S and L directions were 147 and 197 MPa, respectively. The crack population on the surface of a sample at failure increased with the applied stress level and was found to be a Weibull function of the applied maximum stress in this alloy. The strength distribution of fatigue weakest links, where cracks were initiated, was derived from the Weibull function determined by the experimental data. The fatigue weakest-link density was defined as the crack population per unit area at a stress level close to the ultimate tensile stress and can be regarded as a materials property. The density and strength distribution of fatigue weakest links were found to be markedly different between the L and S directions, accounting for the difference in fatigue limit between the directions in this alloy. They were also found to be different between S-L and S-T samples, and between L-T and L-S samples of this alloy, which could not be revealed by the corresponding S-N curves measured. These differences were due to the anisotropy of the microstructures in different directions in this alloy.

  20. Ankle muscle strength discriminates fallers from non-fallers

    PubMed Central

    Cattagni, Thomas; Scaglioni, Gil; Laroche, Davy; Van Hoecke, Jacques; Gremeaux, Vincent; Martin, Alain

    2014-01-01

    It is well known that center of pressure (CoP) displacement correlates negatively with the maximal isometric torque (MIT) of ankle muscles. This relationship has never been investigated in elderly fallers (EF). The purpose of this study was thus to analyze the relationship between the MIT of ankle muscles and CoP displacement in upright stance in a sample aged between 18 and 90 years old that included EF. The aim was to identify a threshold of torque below which balance is compromised. The MIT of Plantar flexors (PFs) and dorsal flexors (DFs) and CoP were measured in 90 volunteers: 21 healthy young adults (YA) (age: 24.1 ± 5.0), 12 healthy middle-aged adults (MAA) (age: 50.2 ± 4.5), 27 healthy elderly non-fallers (ENF) (age: 75.5 ± 7.0) and 30 EF (age: 78.8 ± 6.7). The MIT of PF and DF were summed to obtain the overall maximal ankle muscle strength. Body weight and height were used to normalize MIT (nMIT) and CoP (nCoP), respectively. nCoP correlated negatively with nMIT. 90% of EF generated an nMIT <3.1 N·m·kg−1, whereas 85% of non-fallers generated an nMIT >3.1 N·m·kg−1. The relationship between nMIT and nCoP implies that ankle muscle weakness contributes to increased postural instability and the risk of falling. We observed that below the threshold of 3.1 N·m·kg−1, postural stability was dramatically diminished and balance was compromised. Our results suggest that measuring ankle torque could be used in routine clinical practice to identify potential fallers. PMID:25566068

  1. Subcellular distribution of glycogen and decreased tetanic Ca2+ in fatigued single intact mouse muscle fibres

    PubMed Central

    Nielsen, Joachim; Cheng, Arthur J; Ørtenblad, Niels; Westerblad, Håkan

    2014-01-01

    In skeletal muscle fibres, glycogen has been shown to be stored at different subcellular locations: (i) between the myofibrils (intermyofibrillar); (ii) within the myofibrils (intramyofibrillar); and (iii) subsarcolemmal. Of these, intramyofibrillar glycogen has been implied as a critical regulator of sarcoplasmic reticulum Ca2+ release. The aim of the present study was to test directly how the decrease in cytoplasmic free Ca2+ ([Ca2+]i) during repeated tetanic contractions relates to the subcellular glycogen distribution. Single fibres of mouse flexor digitorum brevis muscles were fatigued with 70 Hz, 350 ms tetani given at 2 s (high-intensity fatigue, HIF) or 10 s (low-intensity fatigue, LIF) intervals, while force and [Ca2+]i were measured. Stimulation continued until force decreased to 30% of its initial value. Fibres were then prepared for analyses of subcellular glycogen distribution by transmission electron microscopy. At fatigue, tetanic [Ca2+]i was reduced to 70 ± 4% and 54 ± 4% of the initial in HIF (P < 0.01, n = 9) and LIF (P < 0.01, n = 5) fibres, respectively. At fatigue, the mean inter- and intramyofibrillar glycogen content was 60–75% lower than in rested control fibres (P < 0.05), whereas subsarcolemmal glycogen was similar to control. Individual fibres showed a good correlation between the fatigue-induced decrease in tetanic [Ca2+]i and the reduction in intermyofibrillar (P = 0.051) and intramyofibrillar (P = 0.0008) glycogen. In conclusion, the fatigue-induced decrease in tetanic [Ca2+]i, and hence force, is accompanied by major reductions in inter- and intramyofibrillar glycogen. The stronger correlation between decreased tetanic [Ca2+]i and reduced intramyofibrillar glycogen implies that sarcoplasmic reticulum Ca2+ release critically depends on energy supply from the intramyofibrillar glycogen pool. PMID:24591577

  2. Electrical Muscle Stimulation: An Effective Form of Exercise and Early Mobilization to Preserve Muscle Strength in Critically Ill Patients

    PubMed Central

    Karatzanos, Eleftherios; Gerovasili, Vasiliki; Zervakis, Dimitrios; Tripodaki, Elli-Sophia; Apostolou, Kleovoulos; Vasileiadis, Ioannis; Papadopoulos, Emmanouil; Mitsiou, Georgios; Tsimpouki, Dimitra; Routsi, Christina; Nanas, Serafim

    2012-01-01

    Purpose. This is a secondary analysis of previously published data to investigate the effects of electrical muscle stimulation (EMS) on strength of various muscle groups in critically ill patients. Methods. One hundred forty-two consecutive patients, with APACHE II score ≥ 13, were randomly assigned to the EMS or the control group. EMS sessions were applied daily on vastus lateralis, vastus medialis, and peroneus longus of both lower extremities. Various muscle groups were evaluated with the Medical Research Council (MRC) scale for muscle strength. Handgrip strength assessment was also employed. Results. Twenty four patients in the EMS group and 28 patients in the control group were finally evaluated. EMS patients achieved higher MRC scores than controls (P ≤ 0.05) in wrist flexion, hip flexion, knee extension, and ankle dorsiflexion. Collectively, the EMS group performed higher (P < 0.01) in the legs and overall. Handgrip strength correlated (P ≤ 0.01) with the upper and lower extremities' muscle strength and the overall MRC scores. Conclusions. EMS has beneficial effects on the strength of critically ill patients mainly affecting muscle groups stimulated, while it may also affect muscle groups not involved presenting itself as a potential effective means of muscle strength preservation and early mobilization in this patient population. PMID:22545212

  3. Fatigue strength reduction model: RANDOM3 and RANDOM4 user manual, appendix 2

    NASA Technical Reports Server (NTRS)

    Boyce, Lola; Lovelace, Thomas B.

    1989-01-01

    The FORTRAN programs RANDOM3 and RANDOM4 are documented. They are based on fatigue strength reduction, using a probabilistic constitutive model. They predict the random lifetime of an engine component to reach a given fatigue strength. Included in this user manual are details regarding the theoretical backgrounds of RANDOM3 and RANDOM4. Appendix A gives information on the physical quantities, their symbols, FORTRAN names, and both SI and U.S. Customary units. Appendix B and C include photocopies of the actual computer printout corresponding to the sample problems. Appendices D and E detail the IMSL, Version 10(1), subroutines and functions called by RANDOM3 and RANDOM4 and SAS/GRAPH(2) programs that can be used to plot both the probability density functions (p.d.f.) and the cumulative distribution functions (c.d.f.).

  4. Physical activity compensates for increased mortality risk among older people with poor muscle strength.

    PubMed

    Portegijs, E; Rantanen, T; Sipilä, S; Laukkanen, P; Heikkinen, E

    2007-10-01

    The aim of the study was to determine whether habitual physical activity can compensate for the increased mortality risk among older people with poor muscle strength. Mortality was followed up for 10 years after laboratory examination in 558 community dwelling 75- and 80-year-old men and women. Maximal isometric strength of five muscle groups was measured and tertile cut-off points were used to categorize participants. Participants, who reported moderate physical activity for at least 4 h a week, were categorized as physically active and the others as sedentary. High muscle strength and physical activity both protected from mortality, but their effect was not additive. Within each muscle strength tertile, physically active people had a lower mortality risk than sedentary people, the effect being most pronounced among those with lower strength in all muscle groups. A high level of physical activity may thus compensate for the increased mortality associated with low muscle strength. PMID:17166169

  5. Changes in corticomotor excitability after fatiguing muscle contractions.

    PubMed

    Sacco, P; Thickbroom, G W; Byrnes, M L; Mastaglia, F L

    2000-12-01

    To investigate whether the type and duration of activity influences corticomotor excitability following fatiguing exercise, we compared motor evoked potential (MEP) responses of the biceps brachii to transcranial magnetic stimulation (TMS) during recovery from two different exercise regimens. Responses were recorded in both the resting state and during a weak contraction. Ten subjects performed a 60-s maximal voluntary contraction (MVC) and, on a subsequent occasion, a sustained 20% MVC to the point of exhaustion. Resting MEP amplitude declined following maximal and submaximal protocols, reaching 34% and 31% of pre-exercise means, respectively (P < 0.001 for both). In contrast, mean facilitated MEP amplitude showed a smaller and more transient decrement following the sustained submaximal effort (64%; P < 0.05), but not the 60-s MVC. Abolition of the postexercise depression in resting MEP amplitude by a weak tonic contraction indicates that decreases in excitability at the spinal level contribute to the reduced corticomotor excitability observed after fatiguing exercise. PMID:11102907

  6. Muscle Size Not Density Predicts Variance in Muscle Strength and Neuromuscular Performance in Healthy Adult Men and Women.

    PubMed

    Weeks, Benjamin K; Gerrits, Tom A J; Horan, Sean A; Beck, Belinda R

    2016-06-01

    Weeks, BK, Gerrits, TAJ, Horan, SA, and Beck, BR. Muscle size not density predicts variance in muscle strength and neuromuscular performance in healthy adult men and women. J Strength Cond Res 30(6): 1577-1584, 2016-The purpose of this study was to determine the relationships between peripheral quantitative computed tomography (pQCT)-derived measures of muscle area and density and markers of muscle strength and performance in men and women. Fifty-two apparently healthy adults (26 men, 26 women; age 33.8 ± 12.0 years) volunteered to participate. Dual-energy x-ray absorptiometry (XR-800; Norland Medical Systems, Inc., Trumbull, CT, USA) was used to determine whole body and regional lean and fat tissue mass, whereas pQCT (XCT-3000; Stratec, Pforzheim, Germany) was used to determine muscle cross-sectional area (MCSA) and muscle density of the leg, thigh, and forearm. Ankle plantar flexor and knee extensor strengths were examined using isokinetic dynamometry, and grip strength was examined with dynamometry. Impulse generated during a maximal vertical jump was used as an index of neuromuscular performance. Thigh, forearm, and leg MCSA strongly predicted variance in knee extensor (R = 0.77, p < 0.001) and grip strength (R = 0.77, p < 0.001) and weakly predicted variance in ankle plantar flexor strength (R = 0.20, p < 0.001), respectively, whereas muscle density was only a weak predictor of variance in knee extensor strength (R = 0.18, p < 0.001). Thigh and leg MCSA accounted for 79 and 69% of the variance in impulse generated from a maximal vertical jump (p < 0.001), whereas thigh muscle density predicted only 18% of the variance (p < 0.002). In conclusion, we found that pQCT-derived muscle area is more strongly related to strength and neuromuscular performance than muscle density in adult men and women. PMID:26473521

  7. The effect of job rotation intervals on muscle fatigue--lactic acid.

    PubMed

    Filus, Rodrigo; Okimorto, Maria Lucia

    2012-01-01

    This study is a job rotation comparative that aims to define the properly scheme to be in use at the time it is performed. As fatigue plays directly against the work results this comprehensive study about the action of lactic acid over workers at different jobs and strength demand was realized to find the best methodology to maximize those rotations. PMID:22316939

  8. Predicting Strength and Fatigue for Suited and Unsuited Conditions from Empirical Data

    NASA Technical Reports Server (NTRS)

    Maida, James C.; Gonzalez, L. J.; Rajulu, S.; Russo, Dane M. (Technical Monitor)

    2001-01-01

    The need for longer and more labor-intensive extra-vehicular activities (EVA) is required for construction and maintenance of the International Space Station (ISS). Issues pertaining to human performance while wearing a space suit (EMU) for prolonged periods have become more important. This project was conducted to investigate how a pressurized Extra-vehicular Mobility Unit (EMU) affects human upper body joint strength and fatigue and how to predict it from computer models based on the data collected.

  9. Effects of Hydrogen Gas Environment on Fatigue Strength at 107 cycles in Plain Specimen of Type 316L Stainless Steel

    NASA Astrophysics Data System (ADS)

    Kawamoto, Kyohei; Ochi, Kazuhiko; Oda, Yasuji; Noguchi, Hiroshi

    In order to clarify the hydrogen effect on the fatigue strength at 107 cycles in a plain specimen of type 316L austenitic stainless steel, rotating bending fatigue tests in laboratory air and plane bending fatigue tests in 1.0 MPa dry hydrogen gas and in air at 313 K were carried out. The main results obtained are as follows. The observed fatigue behavior showed that the fatigue strength at 107 cycles in both environments is determined by the non-propagation of a fatigue crack of the order of the grain size. Also, the strength at 107 cycles in hydrogen gas is slightly higher than that in air. In the region of high-cycle fatigue, the fatigue life in hydrogen gas is longer than that in air, which is mainly caused by the longer crack initiation life in hydrogen gas. The crack propagation life in hydrogen gas is shorter than that in air but has only a small ratio to the fatigue life in this region.

  10. Acromiohumeral Distance and 3-Dimensional Scapular Position Change After Overhead Muscle Fatigue

    PubMed Central

    Maenhout, Annelies; Dhooge, Famke; Van Herzeele, Maarten; Palmans, Tanneke; Cools, Ann

    2015-01-01

    Context: Muscle fatigue due to repetitive and prolonged overhead sports activity is considered an important factor contributing to impingement-related rotator cuff pathologic conditions in overhead athletes. The evidence on scapular and glenohumeral kinematic changes after fatigue is contradicting and prohibits conclusions about how shoulder muscle fatigue affects acromiohumeral distance. Objective: To investigate the effect of a fatigue protocol resembling overhead sports activity on acromiohumeral distance and 3-dimensional scapular position in overhead athletes. Design: Cross-sectional study. Setting: Institutional laboratory. Patients or Other Participants: A total of 29 healthy recreational overhead athletes (14 men, 15 women; age = 22.23 ± 2.82 years, height = 178.3 ± 7.8 cm, mass = 71.6 ± 9.5 kg). Intervention(s) The athletes were tested before and after a shoulder muscle-fatiguing protocol. Main Outcome Measure(s) Acromiohumeral distance was measured using ultrasound, and scapular position was determined with an electromagnetic motion-tracking system. Both measurements were performed at 3 elevation positions (0°, 45°, and 60° of abduction). We used a 3-factor mixed model for data analysis. Results: After fatigue, the acromiohumeral distance increased when the upper extremity was actively positioned at 45° (Δ = 0.78 ± 0.24 mm, P = .002) or 60° (Δ = 0.58 ± 0.23 mm, P = .02) of abduction. Scapular position changed after fatigue to a more externally rotated position at 45° (Δ = 4.97° ± 1.13°, P < .001) and 60° (Δ = 4.61° ± 1.90°, P = .001) of abduction, a more upwardly rotated position at 45° (Δ = 6.10° ± 1.30°, P < .001) and 60° (Δ = 7.20° ± 1.65°, P < .001) of abduction, and a more posteriorly tilted position at 0°, 45°, and 60° of abduction (Δ = 1.98° ± 0.41°, P < .001). Conclusions: After a fatiguing protocol, we found changes in acromiohumeral distance and scapular position that corresponded with an impingement

  11. Muscular Activity and Fatigue in Lower-Limb and Trunk Muscles during Different Sit-To-Stand Tests

    PubMed Central

    Roldán-Jiménez, Cristina; Bennett, Paul; Cuesta-Vargas, Antonio I.

    2015-01-01

    Sit-to-stand (STS) tests measure the ability to get up from a chair, reproducing an important component of daily living activity. As this functional task is essential for human independence, STS performance has been studied in the past decades using several methods, including electromyography. The aim of this study was to measure muscular activity and fatigue during different repetitions and speeds of STS tasks using surface electromyography in lower-limb and trunk muscles. This cross-sectional study recruited 30 healthy young adults. Average muscle activation, percentage of maximum voluntary contraction, muscle involvement in motion and fatigue were measured using surface electrodes placed on the medial gastrocnemius (MG), biceps femoris (BF), vastus medialis of the quadriceps (QM), the abdominal rectus (AR), erector spinae (ES), rectus femoris (RF), soleus (SO) and the tibialis anterior (TA). Five-repetition STS, 10-repetition STS and 30-second STS variants were performed. MG, BF, QM, ES and RF muscles showed differences in muscle activation, while QM, AR and ES muscles showed significant differences in MVC percentage. Also, significant differences in fatigue were found in QM muscle between different STS tests. There was no statistically significant fatigue in the BF, MG and SO muscles of the leg although there appeared to be a trend of increasing fatigue. These results could be useful in describing the functional movements of the STS test used in rehabilitation programs, notwithstanding that they were measured in healthy young subjects. PMID:26506612

  12. Influence of blood flow occlusion on the development of peripheral and central fatigue during small muscle mass handgrip exercise.

    PubMed

    Broxterman, R M; Craig, J C; Smith, J R; Wilcox, S L; Jia, C; Warren, S; Barstow, T J

    2015-09-01

    Critical power represents an important threshold for neuromuscular fatigue development and may, therefore, dictate intensities for which exercise tolerance is determined by the magnitude of fatigue accrued. Peripheral fatigue appears to be constant across O2 delivery conditions for large muscle mass exercise, but this consistency is equivocal for smaller muscle mass exercise. We sought to determine the influence of blood flow occlusion during handgrip exercise on neuromuscular fatigue development and to examine the relationship between neuromuscular fatigue development and W '. Blood flow occlusion influenced the development of both peripheral and central fatigue, thus providing further evidence that the magnitude of peripheral fatigue is not constant across O2 delivery conditions for small muscle mass exercise. W ' appears to be related to the magnitude of fatigue accrued during exercise, which may explain the reported consistency of intramuscular metabolic perturbations and work performed for severe-intensity exercise. The influence of the muscle metabolic milieu on peripheral and central fatigue is currently unclear. Moreover, the relationships between peripheral and central fatigue and the curvature constant (W ') have not been investigated. Six men (age: 25 ± 4 years, body mass: 82 ± 10 kg, height: 179 ± 4 cm) completed four constant power handgrip tests to exhaustion under conditions of control exercise (Con), blood flow occlusion exercise (Occ), Con with 5 min post-exercise blood flow occlusion (Con + Occ), and Occ with 5 min post-exercise blood flow occlusion (Occ + Occ). Neuromuscular fatigue measurements and W ' were obtained for each subject. Each trial resulted in significant peripheral and central fatigue. Significantly greater peripheral (79.7 ± 5.1% vs. 22.7 ± 6.0%) and central (42.6 ± 3.9% vs. 4.9 ± 2.0%) fatigue occurred for Occ than for Con. In addition, significantly greater peripheral (83.0 ± 4.2% vs. 69.0 ± 6.2%) and central

  13. A NEW CLINICAL MUSCLE FUNCTION TEST FOR ASSESSMENT OF HIP EXTERNAL ROTATION STRENGTH: AUGUSTSSON STRENGTH TEST

    PubMed Central

    2016-01-01

    ABSTRACT Introduction Dynamic clinical tests of hip strength applicable on patients, non–athletes and athletes alike, are lacking. The aim of this study was therefore to develop and evaluate the reliability of a dynamic muscle function test of hip external rotation strength, using a novel device. A second aim was to determine if gender differences exist in absolute and relative hip strength using the new test. Methods Fifty–three healthy sport science students (34 women and 19 men) were tested for hip external rotation strength using a device that consisted of a strap connected in series with an elastic resistance band loop, and a measuring tape connected in parallel with the elastic resistance band. The test was carried out with the subject side lying, positioned in 45 ° of hip flexion and the knees flexed to 90 ° with the device firmly fastened proximally across the knees. The subject then exerted maximal concentric hip external rotation force against the device thereby extending the elastic resistance band. The displacement achieved by the subject was documented by the tape measure and the corresponding force production was calculated. Both right and left hip strength was measured. Fifteen of the subjects were tested on repeated occasions to evaluate test–retest reliability. Results No significant test–retest differences were observed. Intra–class correlation coefficients ranged 0.93–0.94 and coefficients of variation 2.76–4.60%. In absolute values, men were significantly stronger in hip external rotation than women (right side 13.2 vs 11.0 kg, p = 0.001, left side 13.2 vs 11.5 kg, p = 0.002). There were no significant differences in hip external rotation strength normalized for body weight (BW) between men and women (right side 0.17 kg/BW vs 0.17 kg/BW, p = 0.675, left side 0.17 kg/BW vs 0.18 kg/BW, p = 0.156). Conclusions The new muscle function test showed high reliability and thus could be useful for measuring dynamic hip

  14. Muscle Fatigue Increases Metabolic Costs of Ergometer Cycling without Changing VO2 Slow Component

    PubMed Central

    Ratkevicius, Aivaras; Stasiulis, Arvydas; Dubininkaite, Loreta; Skurvydas, Albertas

    2006-01-01

    The aim of the present study was to investigate effects of muscle fatigue on oxygen costs of ergometer cycling and slow component of pulmonary oxygen uptake (VO2) kinetics. Seven young men performed 100 drop jumps (drop height of 40 cm) with 20 s of rest after each jump. After the subsequent hour of rest, they cycled at 70, 105, 140 and 175 W, which corresponded to 29.6 ± 5.4, 39.4 ± 7.0, 50.8 ± 8.4 and 65.8 ± 11.8 % of VO2peak, respectively, for 6 min at each intensity with 4-min intervals of rest in between the exercise bouts. The VO2 response to cycling after the exercise (fatigue condition) was compared to ergometer cycling without prior exercise (control condition). From 3rd to 6th min of cycling at 105, 140 and 175 W, VO2 was higher (p < 0.05-0.01) when cycling in the fatigue compared to the control condition. Slow component of VO2 kinetics was observed when cycling at 175 W in the control condition (0.17 ± 0.09, l·min-1, mean ± SD), but tended to decrease in the fatigue condition (0.13 ± 0.15 l·min-1). In summary, results of the study are in agreement with the hypothesis that muscle fatigue increases oxygen costs of cycling exercise, but does not affect significantly the slow component of pulmonary oxygen uptake (VO2) kinetics. Key Points Repetitive fatiguing exercise induce an increase in metabolic costs of ergometer cycling exercise. It is argued that muscle pain, muscle temperature, elevated pulmonary ventilation and heart rate, shift towards from carbohydrate to fat metabolism are of minor importance in this phenomenon. Increased recruitment of type II fibres and impaired force transmission between muscle fibres due to damage of structural proteins appear to play the major role in reducing efficiency of ergometer cycling. PMID:24353462

  15. The Changes of Trunk Motion Rhythm and Spinal Loading During Trunk Flexion and Extension Motions Caused by Lumbar Muscle Fatigue.

    PubMed

    Hu, Boyi; Ning, Xiaopeng

    2015-09-01

    Previous studies indicated that lumbar extensor muscle fatigue could potentially affect lumbar-pelvic rhythm and influence spinal loading during trunk motions. In this study, the effects of lumbar extensor muscle fatigue on the normalized lumbar-pelvic rotation rhythm and the associated L5/S1 joint loading during weight lifting and lowering tasks were investigated. Thirteen volunteers performed lifting and lowering of a 20-lbs box both before and after lumbar extensor muscle fatigue, which was generated through a static weight holding task. The normalized lumbar-pelvic motion ratio (L/P ratio) and the external moment on the L5/S1 joint were calculated and compared. Results showed that subjects demonstrated significantly larger normalized L/P ratios during both weight lifting and lowering tasks with the influence of fatigue. In addition, although the spinal loadings remain unchanged at the beginning and ending of both lifting and lowering motions, significantly larger L5/S1 joint moments were observed during both motions after fatigue. Such changes indicate potentially elevated risk of back injury. In a clinical setting, the current results demonstrated that lumbar muscle fatigue could cause transient changes in lumbar-pelvic motion rhythm. Therefore, lumbar muscle fatigue must be avoided when using lumbar-pelvic motion rhythms for patient diagnosis or rehabilitation assessment. PMID:25589373

  16. An analysis of the activity and muscle fatigue of the muscles around the neck under the three most frequent postures while using a smartphone

    PubMed Central

    Choi, Jung-Hyun; Jung, Min-Ho; Yoo, Kyung-Tae

    2016-01-01

    [Purpose] The purpose of this study was to identify changes in the activity and fatigue of the splenius capitis and upper trapezius muscles, which are agonists to the muscles supporting the head, under the three postures most frequently adopted while using a smartphone. [Subjects and Methods] The subjects were 15 college students in their 20s. They formed a single group and had to adopt three different postures (maximum bending, middle bending, and neutral). While the 15 subjects maintained the postures, muscle activity and fatigue were measured using surface electromyography. [Results] Comparison of the muscle fatigue caused by each posture showed statistically significant differences for the right splenius capitis, left splenius capitis, and left upper trapezius muscles. In addition, maintaining the maximum bending posture while using a smartphone resulted in higher levels of fatigue in the right splenius capitis, left splenius capitis, and left upper trapezius muscles compared with those for the middle bending posture. [Conclusion] Therefore, this study suggests that individuals should bend their neck slightly when using a smartphone, rather than bending it too much, or keep their neck straight to reduce fatigue of the cervical erector muscles. PMID:27313393

  17. An analysis of the activity and muscle fatigue of the muscles around the neck under the three most frequent postures while using a smartphone.

    PubMed

    Choi, Jung-Hyun; Jung, Min-Ho; Yoo, Kyung-Tae

    2016-05-01

    [Purpose] The purpose of this study was to identify changes in the activity and fatigue of the splenius capitis and upper trapezius muscles, which are agonists to the muscles supporting the head, under the three postures most frequently adopted while using a smartphone. [Subjects and Methods] The subjects were 15 college students in their 20s. They formed a single group and had to adopt three different postures (maximum bending, middle bending, and neutral). While the 15 subjects maintained the postures, muscle activity and fatigue were measured using surface electromyography. [Results] Comparison of the muscle fatigue caused by each posture showed statistically significant differences for the right splenius capitis, left splenius capitis, and left upper trapezius muscles. In addition, maintaining the maximum bending posture while using a smartphone resulted in higher levels of fatigue in the right splenius capitis, left splenius capitis, and left upper trapezius muscles compared with those for the middle bending posture. [Conclusion] Therefore, this study suggests that individuals should bend their neck slightly when using a smartphone, rather than bending it too much, or keep their neck straight to reduce fatigue of the cervical erector muscles. PMID:27313393

  18. Driving Sodium/Potassium Pumps with an Oscillating Electric field: Effects on Muscle Fatigue

    NASA Astrophysics Data System (ADS)

    Lanes, Olivia; Bovyn, Matthew; Chen, Wei

    2013-03-01

    Dr. Chen has developed a technique called Synchronization Modulation, which has already been proven to be an effective tool in synchronizing and speeding up the sodium/potassium pumps in cell membranes. When synchronized, it is thought that these pumps are more efficient because they require less ATP. We hypothesized that if this was correct, this technique may be used to reduce muscle fatigue. To test our hypothesis, we had multiple test subjects hold a 15 lb weight for as long as they could while isolating the bicep muscle and applying an oscillating electric field. We compared the EMG data we took during these trials to the control, which was done the same way but without applying the electric field. To compare how fatigued subjects were, we did a Fast Fourier Transform on the first and last 10 seconds of each trial to measure the Fatigue Index. Our preliminary results suggest that the Fatigue Index decreased at a slower rate in the trials where the subject held the weight with Synchronization Modulation.

  19. Fatigue-induced Orosomucoid 1 Acts on C-C Chemokine Receptor Type 5 to Enhance Muscle Endurance

    PubMed Central

    Lei, Hong; Sun, Yang; Luo, Zhumin; Yourek, Gregory; Gui, Huan; Yang, Yili; Su, Ding-Feng; Liu, Xia

    2016-01-01

    Understanding and managing fatigue is a significant challenge in clinic and society. In attempting to explore how the body responds to and regulates fatigue, we found in rodent fatigue models that orosomucoid 1 (ORM1) was significantly increased in multiple tissues, including blood and muscle. Interestingly, administration of exogenous ORM1 increased muscle glycogen and enhanced muscle endurance, whereas ORM1 deficiency resulted in a significant decrease of muscle endurance both in vivo and in vitro, which could largely be restored by exogenous ORM1. Further studies demonstrated that ORM1 can bind to C-C chemokine receptor type 5 (CCR5) on muscle cells and deletion of the receptor abolished the effect of ORM1. Thus, fatigue upregulates the level of ORM1, which in turn functions as an anti-fatigue protein to enhance muscle endurance via the CCR5 pathway. Modulation of the level of ORM1 and CCR5 signaling could be a novel strategy for the management of fatigue. PMID:26740279

  20. Effects of Growth Hormone Administration on Muscle Strength in Men over 50 Years Old

    PubMed Central

    Tavares, A. B. W.; Micmacher, E.; Biesek, S.; Assumpção, R.; Redorat, R.; Veloso, U.; Vaisman, M.; Farinatti, P. T. V.; Conceição, F.

    2013-01-01

    Growth hormone (GH) use has been speculated to improve physical capacity in subjects without GH deficiency (GHD) through stimulation of collagen synthesis in the tendon and skeletal muscle, which leads to better exercise training and increased muscle strength. In this context, the use of GH in healthy elderly should be an option for increasing muscle strength. Our aim was to evaluate the effect of GH therapy on muscle strength in healthy men over 50 years old. Fourteen healthy men aged 50–70 years were evaluated at baseline for body composition and muscle strength (evaluated by leg press and bench press exercises, which focus primarily on quadriceps—lower body part and pectoralis major—upper body part—muscles, resp.). Subjects were randomised into 2 groups: GH therapy (7 subjects) and placebo (7 subjects) and reevaluated after 6 months of therapy. Thirteen subjects completed the study (6 subjects in the placebo group and 7 subjects in the GH group). Subjects of both groups were not different at baseline. After 6 months of therapy, muscle strength in the bench press responsive muscles did not increase in both groups and showed a statistically significant increase in the leg press responsive muscles in the GH group. Our study demonstrated an increase in muscle strength in the lower body part after GH therapy in healthy men. This finding must be considered and tested in frail older populations, whose physical incapacity is primarily caused by proximal muscle weakness. The trial was registered with NCT01853566. PMID:24382963

  1. Strength Training for the Intrinsic Flexor Muscles of the Foot: Effects on Muscle Strength, the Foot Arch, and Dynamic Parameters Before and After the Training

    PubMed Central

    Hashimoto, Takayuki; Sakuraba, Keishoku

    2014-01-01

    [Purpose] The purpose of the present study was to verify the effects of intrinsic foot flexor strength training. [Subjects] The subjects were 12 healthy males without motor system disease. [Methods] A training method that involved flexion of all toe interphalangeal and metatarsophalangeal joints against a 3-kg load was implemented and was performed for 200 repetitions once per day, three times per week, for a period of eight weeks. [Results] Significant changes were observed for intrinsic foot flexor strength scores, foot arches, vertical jumping, 1-legged long jumping, and 50-m dash time. [Conclusion] This muscle strength training method significantly improved muscle strength scores, foot arch shape, and movement performance. PMID:24707086

  2. Corrosion Fatigue of High-Strength Titanium Alloys Under Different Stress Gradients

    NASA Astrophysics Data System (ADS)

    Baragetti, Sergio; Villa, Francesco

    2015-05-01

    Ti-6Al-4V is the most widely used high strength-to-mass ratio titanium alloy for advanced engineering components. Its adoption in the aerospace, maritime, automotive, and biomedical sectors is encouraged when highly stressed components with severe fatigue loading are designed. The extents of its applications expose the alloy to several aggressive environments, which can compromise its brilliant mechanical characteristics, leading to potentially catastrophic failures. Ti-6Al-4V stress-corrosion cracking and corrosion-fatigue sensitivity has been known since the material testing for pressurized tanks for Apollo missions, although detailed investigations on the effects of harsh environment in terms of maximum stress reduction have been not carried out until recent times. In the current work, recent experimental results from the authors' research group are presented, quantifying the effects of aggressive environments on Ti-6Al-4V under fatigue loading in terms of maximum stress reduction. R = 0.1 axial fatigue results in laboratory air, 3.5 wt.% NaCl solution, and CH3OH methanol solution at different concentrations are obtained for mild notched specimens ( K t = 1.18) at 2e5 cycles. R = 0.1 tests are also conducted in laboratory air, inert environment, 3.5 wt.% NaCl solution for smooth, mild and sharp notched specimens, with K t ranging from 1 to 18.65, highlighting the environmental effects for the different load conditions induced by the specimen geometry.

  3. Development and Applications of a Self-Contained, Non-Invasive EVA Joint Angle and Muscle Fatigue Sensor System

    NASA Technical Reports Server (NTRS)

    Ranniger, C. U.; Sorenson, E. A.; Akin, D. L.

    1995-01-01

    The University of Maryland Space Systems Laboratory, as a participant in NASA's INSTEP program, is developing a non-invasive, self-contained sensor system which can provide quantitative measurements of joint angles and muscle fatigue in the hand and forearm. The goal of this project is to develop a system with which hand/forearm motion and fatigue metrics can be determined in various terrestrial and zero-G work environments. A preliminary study of the prototype sensor systems and data reduction techniques for the fatigue measurement system are presented. The sensor systems evaluated include fiberoptics, used to measure joint angle, surface electrodes, which measure the electrical signals created in muscle as it contracts; microphones, which measure the noise made by contracting muscle; and accelerometers, which measure the lateral muscle acceleration during contraction. The prototype sensor systems were used to monitor joint motion of the metacarpophalangeal joint and muscle fatigue in flexor digitorum superficialis and flexor carpi ulnaris in subjects performing gripping tasks. Subjects were asked to sustain a 60-second constant-contraction (isometric) exercise and subsequently to perform a repetitive handgripping task to failure. Comparison of the electrical and mechanical signals of the muscles during the different tasks will be used to evaluate the applicability of muscle signal measurement techniques developed for isometric contraction tasks to fatigue prediction in quasi-dynamic exercises. Potential data reduction schemes are presented.

  4. Ascorbate infusion increases skeletal muscle fatigue resistance in patients with chronic obstructive pulmonary disease.

    PubMed

    Rossman, Matthew J; Garten, Ryan S; Groot, H Jonathan; Reese, Van; Zhao, Jia; Amann, Markus; Richardson, Russell S

    2013-11-15

    Chronic obstructive pulmonary disease (COPD) is associated with systemic oxidative stress and skeletal muscle dysfunction. The purpose of this study was to examine the impact of intravenous ascorbate administration (AO) on biological markers of antioxidant capacity and oxidative stress, and subsequently skeletal muscle function during dynamic, small muscle mass exercise in patients with COPD. Ten patients with spirometric evidence of COPD performed single-leg knee extensor (KE) trials matched for intensity and time (isotime) following intravenous ascorbate (2 g) or saline infusion (PL). Quadriceps fatigue was quantified by changes in force elicited by maximal voluntary contraction (MVC) and magnetic femoral nerve stimulation (Qtw,pot). AO administration significantly increased antioxidant capacity, as measured by the ferric-reducing ability of plasma (PL: 1 ± 0.1 vs. AO: 5 ± 0.2 mM), and significantly reduced malondialdehyde levels (PL: 1.16 ± 0.1 vs. AO: 0.97 ± 0.1 mmol). Additionally, resting blood pressure was significantly reduced (PL: 104 ± 4 vs. AO: 93 ± 6 mmHg) and resting femoral vascular conductance was significantly elevated after AO (PL: 2.4 ± 0.2 vs. AO: 3.6 ± 0.4 ml·min(-1)·mmHg(-1)). During isotime exercise, the AO significantly attenuated both the ventilatory and metabolic responses, and patients accumulated significantly less peripheral quadriceps fatigue, as illustrated by less of a fall in MVC (PL: -11 ± 2% vs. AO: -5 ± 1%) and Qtw,pot (PL: -37 ± 1% vs. AO: -30 ± 2%). These data demonstrate a beneficial role of AO administration on skeletal muscle fatigue in patients with COPD and further implicate systemic oxidative stress as a causative factor in the skeletal muscle dysfunction observed in this population. PMID:24068051

  5. Strength and fatigue of zirconia-induced weak spots in optical fiber

    NASA Astrophysics Data System (ADS)

    Breuls, Anton H. E.; Svenson, T.

    1994-03-01

    The reliability of long lengths of fibers in optical cables is determined by the presence of weak spots which are infrequently produced by normal fiber production methods. It is important to investigate the influence on strength of fiber from different kinds of weak spots. The present study is confined to weak spots resulting from melted-in zirconia particles. Tensile testing of optical fiber, in which strength degrading particles of a roughly dual-size distribution have been introduced on purpose, was done At a wide range of stress rates. The Weibull plots of tensile strength of the fiber were compared with a theoretical distribution, based on a simple relation between particle size and fiber strength. In this way, failure modes could be identified and related to the size of particles. From the comparison it was concluded that the size of zirconia particles has no significant influence on the fatigue of fiber, within the applied stress rates. A significant retardment of the fatigue of weak spots was also observed at low stress rates.

  6. Fatigue strength of high-temperature alloys under conditions of cyclic temperature variation. Communication 1: Experimental procedure and results

    NASA Astrophysics Data System (ADS)

    Troshchenko, V. T.; Gryaznov, B. A.; Yamshanov, Yu. B.

    1994-03-01

    Determination of the serviceability of the material of gas-turbine engine blades, one of the most loaded elements of the engine, critical for the reliability of the turbine, is discussed. The NUM-3 setup, intended for studying fatigue strength of high-temperature alloys under conditions simulating service ones, is briefly described. The results of the investigation into the fatigue of alloys EP962 and EI698 under isothermal conditions and complex thermal-mechanical loading are presented. The analysis of the findings revealed a number of regularities in the effect of thermal cycling and resulting varying thermal stresses on the fatigue strength of the materials studied.

  7. Fatigue

    MedlinePlus

    ... sleep. Fatigue is a lack of energy and motivation. Drowsiness and apathy (a feeling of not caring ... fatigue symptoms, and your lifestyle, habits, and feelings. Tests that may be ordered include the following: Blood ...

  8. Effects of muscle fatigue on gait characteristics under single and dual-task conditions in young and older adults

    PubMed Central

    2010-01-01

    Background Muscle fatigue and dual-task walking (e.g., concurrent performance of a cognitive interference (CI) while walking) represent major fall risk factors in young and older adults. Thus, the objectives of this study were to examine the effects of muscle fatigue on gait characteristics under single and dual-task conditions in young and older adults and to determine the impact of muscle fatigue on dual-task costs while walking. Methods Thirty-two young (24.3 ± 1.4 yrs, n = 16) and old (71.9 ± 5.5 yrs, n = 16) healthy active adults participated in this study. Fatigue of the knee extensors/flexors was induced by isokinetic contractions. Subjects were tested pre and post fatigue, as well as after a 5 min rest. Tests included the assessment of gait velocity, stride length, and stride length variability during single (walking), and dual (CI+walking) task walking on an instrumented walkway. Dual-task costs while walking were additionally computed. Results Fatigue resulted in significant decreases in single-task gait velocity and stride length in young adults, and in significant increases in dual-task gait velocity and stride length in older adults. Further, muscle fatigue did not affect dual-task costs during walking in young and older adults. Performance in the CI-task was improved in both age groups post-fatigue. Conclusions Strategic and/or physiologic rationale may account for the observed differences in young and older adults. In terms of strategic rationale, older adults may walk faster with longer strides in order to overcome the feeling of fatigue-induced physical discomfort as quickly as possible. Alternatively, older adults may have learned how to compensate for age-related and/or fatigue-induced muscle deficits during walking by increasing muscle power of synergistic muscle groups (e.g., hip flexors). Further, a practice and/or learning effect may have occurred from pre to post testing. Physiologic rationale may comprise motor unit remodeling in old age

  9. Effects of thermal fatigue on shear punch strength of tooth-colored restoratives

    PubMed Central

    Melody, Fam Mei Shi; U-Jin, Yap Adrian; Natalie, Tan Wei Min; Elizabeth, Tay Wan Ling; Chien, Jessica Yeo Siu

    2016-01-01

    Aims: This study investigated the effect of thermal fatigue on the shear strength of a range of tooth-colored restorative materials including giomers, zirconia-reinforced glass ionomer cement (GIC), nano-particle resin-modified GIC, highly viscous GICs, and composite resin. Materials and Methods: Twenty specimens of each material were fabricated in standardized washers (17 mm outer diameter, 9 mm internal diameter, 1 mm thick). The specimens were cured, stored in 100% humidity at 37.5°C for 24 h, and randomly divided into two groups of 10. Group A specimens were nonthermocycled (NT) and stored in distilled water at 37°C for 168 h. Group B specimens were thermocycled (TC) for 10,000 cycles (168 h) with baths X, Y, and Z adjusted to 35°C, 15°C, and 45°C, respectively. Each cycle had dwell times of 28 s in X, and 2s in Y/Z in the order XYXZ. Specimens then underwent shear punch testing at a crosshead speed of 0.5 mm/min with a 2 kN load cell. Statistical analysis of shear strength was done using t-test and two-way ANOVA/Scheffe's post hoc test at significance level P < 0.05. Results: The effect of thermal fatigue on shear strength was material dependent. Except for the “sculptable” giomer (Beautifil II) and a highly viscous GIC (Fuji IX GP Fast), no significant differences in shear strength were generally observed between the NT and TC groups. For both groups, the composite resin (Filtek Z250XT) had the highest shear strength while the zirconia-reinforced (zirconomer) and a highly viscous GIC (Ketac Molar Quick) had the lowest. Conclusions: The effect of thermocycling on shear strength was material dependent. Thermal fatigue, however, did not significantly influence the shear strength of most materials assessed. The “sculptable” composite and giomer were significantly stronger than the other materials evaluated. Shear strength of the “flowable” injectable hybrid giomer was intermediate between the composite and GICs. PMID:27563182

  10. Fatigue-Induced Changes in Movement Pattern and Muscle Activity During Ballet Releve on Demi-Pointe.

    PubMed

    Lin, Cheng-Feng; Lee, Wan-Chin; Chen, Yi-An; Hsue, Bih-Jen

    2016-08-01

    Fatigue in ballet dancers may lead to injury, particularly in the lower extremities. However, few studies have investigated the effects of fatigue on ballet dancers' performance and movement patterns. Thus, the current study examines the effect of fatigue on the balance, movement pattern, and muscle activities of the lower extremities in ballet dancers. Twenty healthy, female ballet dancers performed releve on demi-pointe before and after fatigue. The trajectory of the whole body movement and the muscle activities of the major lower extremity muscles were recorded continuously during task performance. The results show that fatigue increases the medial-lateral center of mass (COM) displacement and hip and trunk motion, but decreases the COM velocity and ankle motion. Moreover, fatigue reduces the activities of the hamstrings and tibialis anterior, but increases that of the soleus. Finally, greater proximal hip and trunk motions are applied to compensate for the effects of fatigue, leading to a greater COM movement. Overall, the present findings show that fatigue results in impaired movement control and may therefore increase the risk of dance injury. PMID:26955753

  11. Fatigue-Induced Changes in Movement Pattern and Muscle Activity During Ballet Releve on Demi-Pointe.

    PubMed

    Lin, Cheng-Feng; Lee, Wan-Chin; Chen, Yi-An; Hsue, Bih-Jen

    2016-08-01

    Fatigue in ballet dancers may lead to injury, particularly in the lower extremities. However, few studies have investigated the effects of fatigue on ballet dancers' performance and movement patterns. Thus, the current study examines the effect of fatigue on the balance, movement pattern, and muscle activities of the lower extremities in ballet dancers. Twenty healthy, female ballet dancers performed releve on demi-pointe before and after fatigue. The trajectory of the whole body movement and the muscle activities of the major lower extremity muscles were recorded continuously during task performance. The results show that fatigue increases the medial-lateral center of mass (COM) displacement and hip and trunk motion, but decreases the COM velocity and ankle motion. Moreover, fatigue reduces the activities of the hamstrings and tibialis anterior, but increases that of the soleus. Finally, greater proximal hip and trunk motions are applied to compensate for the effects of fatigue, leading to a greater COM movement. Overall, the present findings show that fatigue results in impaired movement control and may therefore increase the risk of dance injury. PMID:27622498

  12. Cryogenic Tensile Strength and Fatigue Life of Carbon Nanotube Multi-Yarn.

    PubMed

    Misak, H E; Mall, S

    2016-03-01

    Carbon nanotube (CNT) multi-yarns, consisting of 30 yarns, were tested under monotonic tensile load and fatigue at the room temperature (298 K) and two cryogenic temperatures (232 and 123 K). Tensile stiffness increased with the decrease of temperature. The average ultimate tensile strength was higher at 123 K when compared to the higher temperatures (232 and 298 K). Failure mechanism changed from a combination of classical variant and independent fiber breakage at the two higher temperatures to mostly classical variant failure mechanism at the lower temperature. The CNT-yarn's fatigue life also increased with decreasing temperature. CNT-yarns have been shown to function well at lower temperatures making them usable for applications requiring operation at cryogenic temperatures, such as in satellites and high altitude aircraft. PMID:27455753

  13. Effects of fatigue and environment on residual strengths of center-cracked graphite/epoxy buffer strip panels

    NASA Technical Reports Server (NTRS)

    Bigelow, Catherine A.

    1989-01-01

    The effects of fatigue, moisture conditioning, and heating on the residual tension strengths of center-cracked graphite/epoxy buffer strip panels were evaluated using specimens made with T300/5208 graphite epoxy in a 16-ply quasi-isotropic layup, with two different buffer strip materials, Kevlar-49 or S-glass. It was found that, for panels subjected to fatigue loading, the residual strengths were not significantly affected by the fatigue loading, the number of repetitions of the loading spectrum, or the maximum strain level. The moisture conditioning reduced the residual strengths of the S-glass buffer strip panels by 10 to 15 percent below the ambient results, but increased the residual strengths of the Kevlar-49 buffer strip panels slightly. For both buffer strip materials, the heat increased the residual strengths of the buffer strip panels slightly over the ambient results.

  14. Severe COPD Alters Muscle Fiber Conduction Velocity During Knee Extensors Fatiguing Contraction.

    PubMed

    Boccia, Gennaro; Coratella, Giuseppe; Dardanello, Davide; Rinaldo, Nicoletta; Lanza, Massimo; Schena, Federico; Rainoldi, Alberto

    2016-10-01

    The aim of this study was to assess the changes in muscle fiber conduction velocity (CV), as a sign of fatigue during knee extensor contraction in patients with chronic obstructive pulmonary disease (COPD) as compared with healthy controls. Eleven male patients (5 with severe and 6 with moderate COPD; age 67 ± 5 years) and 11 age-matched healthy male controls (age 65 ± 4 years) volunteered for the study. CV was obtained by multichannel surface electromyography (EMG) from the vastus lateralis (VL) and medialis (VM) of the quadriceps muscle during isometric, 30-second duration knee extension at 70% of maximal voluntary contraction. The decline in CV in both the VL and VM was steeper in the severe COPD patients than in healthy controls (for VL: severe COPD vs. controls -0.45 ± 0.07%/s; p < 0.001, and for VM: severe COPD vs. controls -0.54 ± 0.09%/s, p < 0.001). No difference in CV decline was found between the moderate COPD patients and the healthy controls. These findings suggest that severe COPD may impair muscle functions, leading to greater muscular fatigue, as expressed by CV changes. The results may be due to a greater involvement of anaerobic metabolism and a shift towards fatigable type II fibers in the muscle composition of the severe COPD patients. PMID:27007486

  15. Impact on nutrition on muscle strength and performance in older adults

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Muscle strength plays an important role in determining risk for falls, which result in fractures and other injuries. While bone loss has long been recognized as an inevitable consequence of aging, sarcopenia-the gradual loss of skeletal muscle mass and strength that occurs with advancing age-has rec...

  16. Effect of thigh muscle fatigue on the biomechanical factors of the lower limbs when walking in a squatted position

    PubMed Central

    Hong, Wan-Ki; Lee, Chul-Gab; Ko, Dae-Sik

    2016-01-01

    [Purpose] The purpose of this study was to compare and analyze the effects of thigh muscle fatigue caused by walking in a squatted position on biomechanical factors, to evaluate the risk of a job performed sitting in a squatted position for a long period of time. [Subjects and Methods] Eighteen right foot dominant women without any injuries in their joints and body in the last 6 months were selected. They walked in a squatted position, and then muscle fatigue was induced by using an isokinetic muscular function measuring device (CSMI, USA). After the CSMI measurement, the participants performed walking in a squatted position again. [Results] After inducing thigh muscle fatigue, the knee joint maximum adduction moment significantly increased and the required duration was reduced. The muscle fatigue index was positively correlated with adduction moment and negatively with the duration. It influenced the changes of maximum adduction moment; 55.0% of the adduction moment change was explained by the degree of fatigue. [Conclusion] A quantitative analysis of working in a squatted position was performed. The thigh muscle fatigue index negatively the knee joint during walking in a squatted position. Therefore, this experiment can be used as an ergonomic analysis tool of general farm work. PMID:27134402

  17. Influence of surface treatment of yttria-stabilized tetragonal zirconia polycrystal with hot isostatic pressing on cyclic fatigue strength.

    PubMed

    Iijima, Toshihiko; Homma, Shinya; Sekine, Hideshi; Sasaki, Hodaka; Yajima, Yasutomo; Yoshinari, Masao

    2013-01-01

    Hot isostatic pressing processed yttria-stabilized tetragonal zirconia polycrystal (HIP Y-TZP) has the potential for application to implants due to its high mechanical performance. The aim of this study was to investigate the influence of surface treatment of HIP Y-TZP on cyclic fatigue strength. HIP Y-TZP specimens were subjected to different surface treatments. Biaxial flexural strength was determined by both static and cyclic fatigue testing. In the cyclic fatigue test, the load was applied at a frequency of 10 Hz for 10(6) cycles in distilled water at 37°C. The surface morphology, roughness, and crystal phase of the surfaces were also evaluated. The cyclic fatigue strength (888 MPa) of HIP Y-TZP with sandblasting and acid-etching was more than twice that of Y-TZP as specified in ISO 13356 for surgical implants (320 MPa), indicating the clinical potential of this material. PMID:23538763

  18. Influence of Fatigue Loading and Bone Turnover on Bone Strength and Pattern of Experimental Fractures of the Tibia in Mice.

    PubMed

    Bonnet, Nicolas; Gerbaix, Maude; Ominsky, Michael; Ammann, Patrick; Kostenuik, Paul J; Ferrari, Serge L

    2016-07-01

    Bone fragility depends on bone mass, structure, and material properties, including damage. The relationship between bone turnover, fatigue damage, and the pattern and location of fractures, however, remains poorly understood. We examined these factors and their integrated effects on fracture strength and patterns in tibia. Adult male mice received RANKL (2 mg/kg/day), OPG-Fc (5 mg/kg 2×/week), or vehicle (Veh) 2 days prior to fatigue loading of one tibia by in vivo axial compression, with treatments continuing up to 28 more days. One day post fatigue, crack density was similarly increased in fatigued tibiae from all treatment groups. After 28 days, the RANKL group exhibited reduced bone mass and increased crack density, resulting in reduced bone strength, while the OPG-Fc group had greater bone mass and bone strength. Injury repair altered the pattern and location of fractures created by ex vivo destructive testing, with fractures occurring more proximally and obliquely relative to non-fatigued tibia. A similar pattern was observed in both non-fatigued and fatigued tibia of RANKL. In contrast, OPG-Fc prevented this fatigue-related shift in fracture pattern by maintaining fractures more distal and transverse. Correlation analysis showed that bone strength was predominantly determined by aBMD with minor contributions from structure and intrinsic strength as measured by nanoindentation and cracks density. In contrast, fracture location was predicted equally by aBMD, crack density and intrinsic modulus. The data suggest that not only bone strength but also the fracture pattern depends on previous damage and the effects of bone turnover on bone mass and structure. These observations may be relevant to further understand the mechanisms contributing to fracture pattern in long bone with different levels of bone remodeling, including atypical femur fracture. PMID:26945756

  19. Effect of cyclic high loading rates on the fatigue strength of aluminum-based composites

    NASA Astrophysics Data System (ADS)

    Calderon Arteaga, Hermes Eskander

    The study of fatigue under high loading rates is of great interest in the complete characterization of a new series of composites with Al-Cu-Mg matrix reinforced with AlB2 dispersoids. Homogeneous and functionally graded composites were prepared via gravity and centrifugal casting, respectively. Through centrifugal casting a gradual variation of the volume fraction of reinforcing particles along the cross section was obtained. In specific fabrication conditions, even complete segregation of the reinforcement particles was achieved. Charpy impact tests as well as hardness tests were conducted to assess the composite strength as a function of the weight percent of boron. The tensile properties of gravity cast samples were obtained. Then for both casting conditions, simple edge-notched bend SE(B) specimens were tested under fatigue conditions (three-point bending). The results from impact and hardness tests allowed identifying an interaction between the Mg dissolved in the matrix and the diborides. This interaction, which has never been reported before, was responsible for the strength reduction observed. It was assumed that a substitutional diffusion of Al by Mg atoms in the hp3 structure of diboride was causing the strength reduction, and three approaches were developed to estimate the amount of Mg depleted from the matrix by the diborides during the composite processing. Gravity cast samples were more sensitive to monotonic damage due to fatigue loads where compared with functionally-graded composites. Contrary to the centrifugal cast samples, gravity samples were also affected by the loading rate. The Mg-AlB2 interaction was also responsible for the reduction in the fatigue resistance as the weight percent of boron increased in both types of composites; regression models were obtained to predict the crack growth curve slope change as function of the boron level. The particle distribution showed to affect the crack growth behavior of the FGMs, decreasing the

  20. Measuring mechanical properties, including isotonic fatigue, of fast and slow MLC/mIgf-1 transgenic skeletal muscle.

    PubMed

    Del Prete, Zaccaria; Musarò, Antonio; Rizzuto, Emanuele

    2008-07-01

    Contractile properties of fast-twitch (EDL) and slow-twitch (soleus) skeletal muscles were measured in MLC/mIgf-1 transgenic and wild-type mice. MLC/mIgf-1 mice express the local factor mIgf-1 under the transcriptional control of MLC promoter, selectively activated in fast-twitch muscle fibers. Isolated muscles were studied in vitro in both isometric and isotonic conditions. We used a rapid "ad hoc" testing protocol that measured, in a single procedure, contraction time, tetanic force, Hill's (F-v) curve, power curve and isotonic muscle fatigue. Transgenic soleus muscles did not differ from wild-type with regard to any measured variable. In contrast, transgenic EDL muscles displayed a hypertrophic phenotype, with a mass increase of 29.2% compared to wild-type. Absolute tetanic force increased by 21.5% and absolute maximum power by 34.1%. However, when normalized to muscle cross-sectional area and mass, specific force and normalized power were the same in transgenic and wild-type EDL muscles, revealing that mIgf-1 expression induces a functional hypertrophy without altering fibrotic tissue accumulation. Isotonic fatigue behavior did not differ between transgenic and wild-type muscles, suggesting that the ability of mIgf-1 transgenic muscle to generate a considerable higher absolute power did not affect its resistance to fatigue. PMID:18415017

  1. Correlation between vitamin D levels and muscle fatigue risk factors based on physical activity in healthy older adults

    PubMed Central

    Al-Eisa, Einas S; Alghadir, Ahmad H; Gabr, Sami A

    2016-01-01

    Purpose The purpose of this study was to investigate the relationship of serum vitamin D levels with physical activity, obesity, muscle fatigue biomarkers, and total antioxidant capacity (TAC) in healthy older adults. Methods A total of 85 healthy older subjects aged 64–96 years were recruited in this study. Based on estimated energy expenditure scores, the participants were classified into three groups: inactive (n=25), moderate (n=20), and physically active (n=35). Serum 25(OH)D (25-hydroxy vitamin D) levels, metabolic syndrome parameters, TAC activity, muscle fatigue biomarkers (Ca, creatine kinase, lactic acid dehydrogenase, troponin I, hydroxyproline), physical activity, body fatness, and fatigue score (visual analog scale) were estimated using immunoassay techniques and prevalidated questionnaires, respectively. Results Physical activity was estimated in 64.6% of the participants. Males showed higher physical activity (42.5%) compared to females (26.25%). Compared to participants with lower activity, significant reduction in body mass index, waist circumference, hips, fasting blood sugar, triglycerides, total cholesterol, HDL-cholesterol, and LDL-cholesterol were observed in moderate and physically active participants. Also, significant increase in the levels of serum 25(OH)D concentrations, calcium, and TAC activity along with reduction in the levels of muscle fatigue biomarkers: creatine kinase, lactic acid dehydrogenase, troponin I, hydroxyproline, and fatigue scores (visual analog scale) were reported in physically active participants compared to those of lower physical activity. In all participants, serum 25(OH)D concentrations correlated positively with Ca, TAC, physical activity scores, and negatively with body mass index, lipid profile, fatigue scores (visual analog scale), and muscle fatigue biomarkers. Stepwise regression analysis showed that serum 25(OH)D concentrations, physical activity, Ca, TAC, and demographic parameters explained

  2. Wavelet analysis of lumbar muscle oxygenation signals during whole-body vibration: implications for the development of localized muscle fatigue.

    PubMed

    Li, Zengyong; Zhang, Ming; Chen, Guoqiang; Luo, Site; Liu, Feifei; Li, Jianping

    2012-08-01

    The objective of this study was to assess the effects of whole-body vibration (WBV) on lumbar muscle oxygenation oscillations in healthy men based on the wavelet transform of near-infrared spectroscopy signals. Twelve healthy participants were exposed to WBV at frequencies of 3, 4.5 and 6 Hz while muscle oxygenation signal was monitored before, during and recovery from WBV. With spectral analysis based on wavelet transform of NIR signal, six frequency intervals were identified (I, 0.005-0.0095 Hz; II, 0.0095-0.02 Hz; III, 0.02-0.06 Hz; IV, 0.06-0.16 Hz; V, 0.16-0.40 Hz and VI, 0.40-2.0 Hz). It was found that the muscle oxygenation oscillations at 4.5 Hz in the frequency intervals I, II and III was lower during WBV compared with that of at 3 Hz. Present results demonstrated WBV at 4.5 Hz induced lower oscillatory activities than that of at 3 Hz. The lower oscillatory activities might indicate a decrease in the efficiency of oxygen supply to the oxygenated tissue and such mechanism might contribute to the development of local muscle fatigue. PMID:22210560

  3. Tensile and fatigue strength properties of Kevlar 29 aramid/epoxy unidirectional composites

    SciTech Connect

    Zweben, C.

    1981-07-22

    Static and fatigue tensile strength properties of filament wound undirectional Kevlar 29/epoxy, typical of filament wound material used in flywheel rotors, were studied. Machining techniques were developed to minimize fiber fuzzing on edges. The static modulus, normalized to 70% fiber volume fraction is 8.87 x 10/sup 6/ psi. The major Poisson's ratio is 0.37. The static composite tensile strength, normalized to 70% fiber volume fraction is 200 x 10/sup 3/ psi, corresponding to a fiber stress at failure of 286 x 10/sup 3/ psi, which is good for materials having a very high fiber volume fraction. The S-N curve for R = 0.7 was found to be quite flat. Although the techniques used in this program had previously been employed successfully to study the fatigue behavior of Kevlar 29/epoxy and Kevlar 49/epoxy unidirectional materials, we were unable to overcome the persistent problem of cohesive material failure in the tab regions. The apparent reason for this is the very low interlaminar shear strength of the filament wound material. 16 figures.

  4. Surface Studies of Ultra Strength Drilling Steel after Corrosion Fatigue in Simulated Sour Environment

    SciTech Connect

    M. Ziomek-Moroz; J.A. Hawk; R. Thodla; F. Gui

    2012-05-06

    The Unites States predicted 60% growth in energy demand by 2030 makes oil and natural gas primary target fuels for energy generation. The fact that the peak of oil production from shallow wells (< 5000 m) is about to be reached, thereby pushing the oil and natural gas industry into deeper wells. However, drilling to depths greater than 5000 m requires increasing the strength-to weight ratio of the drill pipe materials. Grade UD-165 is one of the ultra- high yield strength carbon steels developed for ultra deep drilling (UDD) activities. Drilling UDD wells exposes the drill pipes to Cl{sup -}, HCO{sub 3}{sup -}/CO{sub 3}{sup 2-}, and H{sub 2}S-containig corrosive environments (i.e., sour environments) at higher pressures and temperatures compared to those found in conventional wells. Because of the lack of synergism within the service environment, operational stresses can result in catastrophic brittle failures characteristic for environmentally assisted cracking (EAC). Approximately 75% of all drill string failures are caused by fatigue or corrosion fatigue. Since there is no literature data on the corrosion fatigue performance of UD-165 in sour environments, research was initiated to better clarify the fatigue crack growth (FCGR) behavior of this alloy in UDD environments. The FCGR behavior of ultra-strength carbon steel, grade UD-165, was investigated by monitoring crack growth rate in deaerated 5%NaCl solution buffered with NaHCO{sub 3}/Na{sub 2}CO{sub 3} and in contact with H{sub 2}S. The partial pressure of H{sub 2}S (p{sub H2S}) was 0.83 kPa and pH of the solution was adjusted by NaOH to 12. The fatigue experiments were performed at 20 and 85 C in an autoclave with surface investigations augmented by scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectroscopy. In this study, research focused on surface analyses supported by the fatigue crack growth rate measurements. Fig. 1 shows an SEM micrograph of the crack that propagated from the

  5. Impact of nutrition on muscle mass, strength, and performance in older adults.

    PubMed

    Mithal, A; Bonjour, J-P; Boonen, S; Burckhardt, P; Degens, H; El Hajj Fuleihan, G; Josse, R; Lips, P; Morales Torres, J; Rizzoli, R; Yoshimura, N; Wahl, D A; Cooper, C; Dawson-Hughes, B

    2013-05-01

    Muscle strength plays an important role in determining risk for falls, which result in fractures and other injuries. While bone loss has long been recognized as an inevitable consequence of aging, sarcopenia-the gradual loss of skeletal muscle mass and strength that occurs with advancing age-has recently received increased attention. A review of the literature was undertaken to identify nutritional factors that contribute to loss of muscle mass. The role of protein, acid-base balance, vitamin D/calcium, and other minor nutrients like B vitamins was reviewed. Muscle wasting is a multifactorial process involving intrinsic and extrinsic alterations. A loss of fast twitch fibers, glycation of proteins, and insulin resistance may play an important role in the loss of muscle strength and development of sarcopenia. Protein intake plays an integral part in muscle health and an intake of 1.0-1.2 g/kg of body weight per day is probably optimal for older adults. There is a moderate [corrected] relationship between vitamin D status and muscle strength. Chronic ingestion of acid-producing diets appears to have a negative impact on muscle performance, and decreases in vitamin B12 and folic acid intake may also impair muscle function through their action on homocysteine. An adequate nutritional intake and an optimal dietary acid-base balance are important elements of any strategy to preserve muscle mass and strength during aging. PMID:23247327

  6. Mathematical Models of Localized Muscle Fatigue: Sensitivity Analysis and Assessment of Two Occupationally-Relevant Models

    PubMed Central

    Rashedi, Ehsan; Nussbaum, Maury A.

    2015-01-01

    Muscle fatigue models (MFM) have broad potential application if they can accurately predict muscle capacity and/or endurance time during the execution of diverse tasks. As an initial step toward facilitating improved MFMs, we assessed the sensitivity of selected existing models to their inherent parameters, specifically that model the fatigue and recovery processes, and the accuracy of model predictions. These evaluations were completed for both prolonged and intermittent isometric contractions, and were based on model predictions of endurance times. Based on a recent review of the literature, four MFMs were initially chosen, from which a preliminary assessment led to two of these being considered for more comprehensive evaluation. Both models had a higher sensitivity to their fatigue parameter. Predictions of both models were also more sensitive to the alteration of their parameters in conditions involving lower to moderate levels of effort, though such conditions may be of most practical, contemporary interest or relevance. Although both models yielded accurate predictions of endurance times during prolonged contractions, their predictive ability was inferior for more complex (intermittent) conditions. When optimizing model parameters for different loading conditions, the recovery parameter showed considerably larger variability, which might be related to the inability of these MFMs in simulating the recovery process under different loading conditions. It is argued that such models may benefit in future work from improving their representation of recovery process, particularly how this process differs across loading conditions. PMID:26656741

  7. 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

    This report presents the results of both the fifth and sixth 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 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 five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle 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 five variables, namely, high temperature, high-cycle and low-cycle 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 an updated version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of high-cycle mechanical fatigue, creep and thermal fatigue was performed. Then using the current version of PROMISS, entitled PROMISS94, a second sensitivity study including the effect of low-cycle mechanical fatigue, as well as, the three previous effects 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 high-cycle mechanical

  8. Contribution of respiratory muscle blood flow to exercise-induced diaphragmatic fatigue in trained cyclists

    PubMed Central

    Vogiatzis, Ioannis; Athanasopoulos, Dimitris; Boushel, Robert; Guenette, Jordan A; Koskolou, Maria; Vasilopoulou, Maroula; Wagner, Harrieth; Roussos, Charis; Wagner, Peter D; Zakynthinos, Spyros

    2008-01-01

    We investigated whether the greater degree of exercise-induced diaphragmatic fatigue previously reported in highly trained athletes in hypoxia (compared with normoxia) could have a contribution from limited respiratory muscle blood flow. Seven trained cyclists completed three constant load 5 min exercise tests at inspired O2 fractions () of 0.13, 0.21 and 1.00 in balanced order. Work rates were selected to produce the same tidal volume, breathing frequency and respiratory muscle load at each (63 ± 1, 78 ± 1 and 87 ± 1% of normoxic maximal work rate, respectively). Intercostals and quadriceps muscle blood flow (IMBF and QMBF, respectively) were measured by near-infrared spectroscopy over the left 7th intercostal space and the left vastus lateralis muscle, respectively, using indocyanine green dye. The mean pressure time product of the diaphragm and the work of breathing did not differ across the three exercise tests. After hypoxic exercise, twitch transdiaphragmatic pressure fell by 33.3 ± 4.8%, significantly (P < 0.05) more than after both normoxic (25.6 ± 3.5% reduction) and hyperoxic (26.6 ± 3.3% reduction) exercise, confirming greater fatigue in hypoxia. Despite lower leg power output in hypoxia, neither cardiac output nor QMBF (27.6 ± 1.2 l min−1 and 100.4 ± 8.7 ml (100 ml)−1 min−1, respectively) were significantly different compared with normoxia (28.4 ± 1.9 l min−1 and 94.4 ± 5.2 ml (100 ml)−1 min−1, respectively) and hyperoxia (27.8 ± 1.6 l min−1 and 95.1 ± 7.8 ml (100 ml)−1 min−1, respectively). Neither IMBF was different across hypoxia, normoxia and hyperoxia (53.6 ± 8.5, 49.9 ± 5.9 and 52.9 ± 5.9 ml (100 ml)−1 min−1, respectively). We conclude that when respiratory muscle energy requirement is not different between normoxia and hypoxia, diaphragmatic fatigue is greater in hypoxia as intercostal muscle blood flow is not increased (compared with normoxia) to compensate for the reduction in , thus further compromising O2

  9. Effect of acute hypoxia on respiratory muscle fatigue in healthy humans

    PubMed Central

    2010-01-01

    Background Greater diaphragm fatigue has been reported after hypoxic versus normoxic exercise, but whether this is due to increased ventilation and therefore work of breathing or reduced blood oxygenation per se remains unclear. Hence, we assessed the effect of different blood oxygenation level on isolated hyperpnoea-induced inspiratory and expiratory muscle fatigue. Methods Twelve healthy males performed three 15-min isocapnic hyperpnoea tests (85% of maximum voluntary ventilation with controlled breathing pattern) in normoxic, hypoxic (SpO2 = 80%) and hyperoxic (FiO2 = 0.60) conditions, in a random order. Before, immediately after and 30 min after hyperpnoea, transdiaphragmatic pressure (Pdi,tw ) was measured during cervical magnetic stimulation to assess diaphragm contractility, and gastric pressure (Pga,tw ) was measured during thoracic magnetic stimulation to assess abdominal muscle contractility. Two-way analysis of variance (time x condition) was used to compare hyperpnoea-induced respiratory muscle fatigue between conditions. Results Hypoxia enhanced hyperpnoea-induced Pdi,tw and Pga,tw reductions both immediately after hyperpnoea (Pdi,tw : normoxia -22 ± 7% vs hypoxia -34 ± 8% vs hyperoxia -21 ± 8%; Pga,tw : normoxia -17 ± 7% vs hypoxia -26 ± 10% vs hyperoxia -16 ± 11%; all P < 0.05) and after 30 min of recovery (Pdi,tw : normoxia -10 ± 7% vs hypoxia -16 ± 8% vs hyperoxia -8 ± 7%; Pga,tw : normoxia -13 ± 6% vs hypoxia -21 ± 9% vs hyperoxia -12 ± 12%; all P < 0.05). No significant difference in Pdi,tw or Pga,tw reductions was observed between normoxic and hyperoxic conditions. Also, heart rate and blood lactate concentration during hyperpnoea were higher in hypoxia compared to normoxia and hyperoxia. Conclusions These results demonstrate that hypoxia exacerbates both diaphragm and abdominal muscle fatigability. These results emphasize the potential role of respiratory muscle fatigue in exercise performance limitation under conditions coupling

  10. An investigation of fatigue phenomenon in the upper limb muscle due to short duration pulses in an FES system

    NASA Astrophysics Data System (ADS)

    Naeem, Jannatul; Wong Azman, Amelia; Khan, Sheroz; Mohd Mustafah, Yasir

    2013-12-01

    Functional Electrical Stimulation (FES) is a method of artificially stimulating muscles or nerves in order to result in contraction or relaxation of muscles. Many studies have shown that FES system has helped patients to live a better lives especially those who are suffering from physical mobility. Unfortunately, one of the main limitations of an FES system besides of its high cost is largely due to muscle fatigue. Muscle fatigue will affect the training duration which could delay patients' recovery rate. In this paper, we analyzed the occurrence of this fatigue phenomenon in terms of stimulator parameters such as amplitude, frequency, pulse width and pulse shape. The objective of this investigation is to identify other key features of the FES system parameters in order to prolong the training duration among patients. The experiment has been done on a healthy person for the duration of one minute and later the muscles response will be observed. Resultant muscle response is recorded as force using force resistive sensor. The experimental results show muscles will get fatigue at a different rate as the frequency increases. The experiment also shows that the duty cycle is reciprocal to the resultant force.

  11. Effects of light-emitting diodes on muscle fatigue and exercise tolerance in patients with COPD: study protocol for a randomized controlled trial

    PubMed Central

    2013-01-01

    Background Light-emitting diodes (LED) have been used to minimize muscle fatigue in athletes and healthy subjects. Patients with chronic obstructive pulmonary disease (COPD) are susceptible to early muscle fatigue. Objective The objective of this study is to investigate the acute effects of LED on muscle function, exercise capacity and cardiorespiratory responses during isometric and dynamic exercise in patients with COPD. Methods This study will assess 30 patients with moderate to severe obstruction (forced expiratory volume-one second,FEV1 ≤70% predicted). Isometric and dynamic protocols will be conducted in two visits each, for a total of four visits a week apart. First, venous blood will be taken from the patients. The isometric protocol will start with the determination of the maximum voluntary isometric contraction (MIVC) to determine the workload (60% of MIVC) for the isometric endurance test (IET). Patients will be randomized to receive either the placebo or LED application (each point will be irradiated for 30 s and the energy received at each point will be 41.7 J). Immediately after finishing this procedure, the patients will carry out the IET until the limit of tolerance or until a 20% fall of strength is observed. After the test, another blood draw will be taken. In another visit (one week later), the same order of procedures will be performed, except with the opposite (LED or placebo). For the dynamic endurance test (DET), the same procedures described above will be followed, except with 75% of the maximal workload obtained from the incremental cycle ergometer test used instead of the IET. The electromyography will be recorded during the isometric and dynamic protocols. Differences in muscle function, exercise capacity and cardiorespiratory responses between the LED and placebo applications will be analyzed. The therapeutic effects of LED could minimize muscle fatigue in patients with COPD by increasing exercise tolerance. Trial registration Trial

  12. Microstructure, Mechanical, and Fatigue Strength of Ti-54M Processed by Rotary Swaging

    NASA Astrophysics Data System (ADS)

    Al-Khazraji, Hasan; El-Danaf, Ehab; Wollmann, Manfred; Wagner, Lothar

    2015-05-01

    TIMETAL 54M is a newly developed (α + β) titanium alloy with nominal composition Ti-5Al-4V-0.6Mo-0.4Fe. The alloy can provide a cost benefit over Ti-6Al-4V due to improved machinability and formability. In the present work, evolution of mechanical properties in terms of tensile and hardness values is investigated as a function of deformation degrees imposed via rotary swaging (RS). Microstructure, mechanical properties, and fatigue performance of Ti-54M are investigated after severe plastic deformation by RS conducted at 850 °C and after being subjected to two different post-swaging annealing conditions. Optical microscopy and scanning electron microscopy using electron back scatter diffraction were utilized to document the evolution of the microstructure. Tensile tests were conducted to characterize mechanical properties. RS, to a true strain of 3.0, is found to lead to a marked ultrafine-grained structure of about 1 μm grain size with low content of high angle grain boundaries (HAGBs). Post-swaging heat treatment at 800 °C followed by air cooling did not change the grain size but exhibited high content of HAGBs. Post-swaging heat treatment at 940 °C followed by furnace cooling resulted in a grain size of about 5 μm and enhanced work-hardening capability and ductility, which resulted in less fatigue notch sensitivity, but at the same time lower fatigue strength at 107 cycles.

  13. Effects of low-frequency electrical stimulation on cumulative fatigue and muscle tone of the erector spinae

    PubMed Central

    Kang, Da-Haeng; Jeon, Jae-Keun; Lee, Joon-Hee

    2015-01-01

    [Purpose] The aim of this study was to determine the effect of low-frequency electrical stimulation on fatigue recovery of the erector spinae with cumulative fatigue induced by repeated lifting and lowering work. [Subjects] Thirty-two healthy men volunteered to participate in this study and they were randomly divided into three groups: a MC group of 12 persons who underwent microcurrent, a TENS group of 10 persons who underwent Transcutaneous electrical nerve stimulation, and a control group of 10 persons who only rested. [Methods] Cumulative fatigue was induced and then, EMG, muscle tone, CK and LDH serum levels of the erector spinae were measured. Each group then underwent the assigned intervention and was re-measured. To analyze the differences in fatigue between before and after the intervention, the paired t-test was conducted, while groups were compared using analysis of covariance with a control group. [Results] The MC groups showed a significant reduction in muscle fatigue and decreased muscle tone when compared to the control group. However, no significant differences were found between the TENS and control groups. [Conclusion] These results suggest that microcurrent stimulation was effective for recovery from cumulative muscle fatigue while TENS had no effect. PMID:25642049

  14. Blunted angiogenesis and hypertrophy are associated with increased fatigue resistance and unchanged aerobic capacity in old overloaded mouse muscle.

    PubMed

    Ballak, Sam B; Busé-Pot, Tinelies; Harding, Peter J; Yap, Moi H; Deldicque, Louise; de Haan, Arnold; Jaspers, Richard T; Degens, Hans

    2016-04-01

    We hypothesize that the attenuated hypertrophic response in old mouse muscle is (1) partly due to a reduced capillarization and angiogenesis, which is (2) accompanied by a reduced oxidative capacity and fatigue resistance in old control and overloaded muscles, that (3) can be rescued by the antioxidant resveratrol. To investigate this, the hypertrophic response, capillarization, oxidative capacity, and fatigue resistance of m. plantaris were compared in 9- and 25-month-old non-treated and 25-month-old resveratrol-treated mice. Overload increased the local capillary-to-fiber ratio less in old (15 %) than in adult (59 %) muscle (P < 0.05). Although muscles of old mice had a higher succinate dehydrogenase (SDH) activity (P < 0.05) and a slower fiber type profile (P < 0.05), the isometric fatigue resistance was similar in 9- and 25-month-old mice. In both age groups, the fatigue resistance was increased to the same extent after overload (P < 0.01), without a significant change in SDH activity, but an increased capillary density (P < 0.05). Attenuated angiogenesis during overload may contribute to the attenuated hypertrophic response in old age. Neither was rescued by resveratrol supplementation. Changes in fatigue resistance with overload and aging were dissociated from changes in SDH activity, but paralleled those in capillarization. This suggests that capillarization plays a more important role in fatigue resistance than oxidative capacity. PMID:26970774

  15. Chemotherapy-Induced Weakness and Fatigue in Skeletal Muscle: The Role of Oxidative Stress

    PubMed Central

    St. Clair, Daret K.

    2011-01-01

    Abstract Significance Fatigue is one of the most common symptoms of cancer and its treatment, manifested in the clinic through weakness and exercise intolerance. These side effects not only compromise patient's quality of life (QOL), but also diminish physical activity, resulting in limited treatment and increased morbidity. Recent Advances Oxidative stress, mediated by cancer or chemotherapeutic agents, is an underlying mechanism of the drug-induced toxicity. Nontargeted tissues, such as striated muscle, are severely affected by oxidative stress during chemotherapy, leading to toxicity and dysfunction. Critical Issues These findings highlight the importance of investigating clinically applicable interventions to alleviate the debilitating side effects. This article discusses the clinically available chemotherapy drugs that cause fatigue and oxidative stress in cancer patients, with an in-depth focus on the anthracycline doxorubicin. Doxorubicin, an effective anticancer drug, is a primary example of how chemotherapeutic agents disrupt striated muscle function through oxidative stress. Future Directions Further research investigating antioxidants could provide relief for cancer patients from debilitating muscle weakness, leading to improved quality of life. Antioxid. Redox Signal. 15, 2543–2563. PMID:21457105

  16. Forced respiration during the deeper water immersion causes the greater inspiratory muscle fatigue in healthy young men

    PubMed Central

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

    2016-01-01

    [Purpose] The purpose of the present study was to evaluate the effect of water immersion at different water depths on respiratory function and the effect of inspiratory load breathing (ILB) during water immersion at different water depths on respiratory muscle strength evaluated by maximum inspiratory and expiratory pressures (PImax and PEmax, respectively). [Subjects] Eight healthy men participated randomly in three trials. [Methods] All sessions were conducted with the participants in a sitting position immersed in a water bath. We evaluated respiratory function, PImax and PEmax during submersion at three different levels of water depth (umbilicus; 4th-rib; or clavicle, CL) and after subsequent 15-min ILB. [Results] Decreases in vital capacity and expiratory reserve volume from baseline by water immersion were significantly greater in the CL trial than those in the other trials. In the CL trial, PImax was immediately reduced after ILB compared to that at baseline, and the reduction was significantly greater than those in the other trials. PEmax was not affected by ILB in any of the trials. [Conclusion] Forced respiration during deeper water immersion caused greater inspiratory muscle fatigue in healthy young men. PMID:27064401

  17. Forced respiration during the deeper water immersion causes the greater inspiratory muscle fatigue in healthy young men.

    PubMed

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

    2016-01-01

    [Purpose] The purpose of the present study was to evaluate the effect of water immersion at different water depths on respiratory function and the effect of inspiratory load breathing (ILB) during water immersion at different water depths on respiratory muscle strength evaluated by maximum inspiratory and expiratory pressures (PImax and PEmax, respectively). [Subjects] Eight healthy men participated randomly in three trials. [Methods] All sessions were conducted with the participants in a sitting position immersed in a water bath. We evaluated respiratory function, PImax and PEmax during submersion at three different levels of water depth (umbilicus; 4th-rib; or clavicle, CL) and after subsequent 15-min ILB. [Results] Decreases in vital capacity and expiratory reserve volume from baseline by water immersion were significantly greater in the CL trial than those in the other trials. In the CL trial, PImax was immediately reduced after ILB compared to that at baseline, and the reduction was significantly greater than those in the other trials. PEmax was not affected by ILB in any of the trials. [Conclusion] Forced respiration during deeper water immersion caused greater inspiratory muscle fatigue in healthy young men. PMID:27064401

  18. Sternohyoid muscle fatigue properties of dy/dy dystrophic mice, an animal model of merosin-deficient congenital muscular dystrophy.

    PubMed

    van Lunteren, Erik; Moyer, Michelle

    2003-10-01

    Humans with merosin-deficient congenital muscular dystrophy have both sucking problems during infancy and sleep-disordered breathing during childhood. We hypothesized that merosin-deficient pharyngeal muscles fatigue faster than normal muscles. This was tested in vitro using sternohyoid muscle from an animal model of this disease, the dy/dy dystrophic mouse. Isometric twitch contraction and half-relaxation times were similar for dy/dy and normal sternohyoid. However, rate of force loss during repetitive 25-Hz train stimulation was markedly diminished in dystrophic compared with normal sternohyoid muscle. Furthermore, force potentiation, which occurred during the early portion of the fatigue-inducing stimulation, had a longer duration in dystrophic compared with normal muscle (approximately 60 versus 20 s). As a result of these two processes, at the end of 2 min of stimulation, force of dystrophic muscle had decreased by 8 +/- 5% and that of normal muscle by 69 +/- 4% (p < 0.0001). The potassium-channel blocker, 3,4-diaminopyridine, increased force of dy/dy sternohyoid muscle during twitch and 25-Hz contractions by 148 +/- 20% (p < 0.00001) and 109 +/- 18% (p < 0.00002), respectively. During repetitive 25-Hz stimulation, force of 3,4-diaminopyridine-treated dystrophic muscle remained significantly higher than that of untreated muscle, despite the early force potentiation being eliminated and fatigue being accelerated. Thus, merosin deficiency reduces fatigue and prolongs the duration of force potentiation. The latter alterations may partially preserve the integrity of upper airway muscle function, without which the severity of pharyngeal complications (feeding problems, sleep-related respiratory dysfunction) might be even more pronounced in the human merosin-deficient congenital muscular dystrophies. PMID:12840158

  19. Fatigue strength of Inconel 625 plate and weldments used in the DIII-D configuration vacuum vessel

    SciTech Connect

    Trester, P.W.; Kaae, J.L.; Gallix, R.

    1984-12-01

    The Doublet III-D vacuum vessel will enable fusion experiments with large dee-configuration plasmas in the tokamak device at GA Technologies Inc. The vessel is a welded structure of Ni-Cr-Mo-Nb alloy Inconel 625, in the forms of mill-annealed plate and sheet. An emphasis was placed on spceifying material with small grain size to enhance fatigue resistance. Fatigue strength was determined by tension-compression axial strain cycling of specimens excised from stock plate 25 mm thick. In addition, tests were conducted on gas-tungsten-arc weldments. The strain ranges and the resulting alternating, which produced fatigue lives between 10/sup 3/ and 10/sup 6/ cycles, were determined in the test program. Comparisons are presented with published data obtained using the rotating-beam test method. A discussion is also presented on the effect of the grain size on fatigue strength.

  20. Respiratory muscle strength test: is it realistic in young children?

    PubMed Central

    Heinzmann-Filho, João Paulo; Donadio, Márcio Vinícius Fagundes

    2015-01-01

    Objective: To determine the success rate of the manovacuometry test in children between 4 and 12 years of age. Methods: Cross-sectional study involving children and adolescents from 4 to 12 years of age, enrolled in three basic education schools. All subjects had the anthropometric and respiratory muscle strength (maximum inspiratory pressure and maximum expiratory pressure) data measured. Students whose parents did not authorize participation or who did not want to undergo the test were excluded. The test was considered successful when the subject reached acceptability (no air leaks) and reproducibility (variation <10% between the two major maneuvers) criteria established by guidelines. Failure was defined when subjects did not meet the above criteria. Data were expressed as mean and standard deviation and the categorical variables in absolute and relative frequency. The comparison between proportions was performed using the chi-square test. Results: We included 196 children and adolescents, mean age of 8.4±2.5 years, 53.1% female. The success rate of the manovacuometry test in children and adolescents evaluated was 92.3%. When comparing the differences between the success rates of preschool children with those children and adolescents of school age, there was a significantly lower success rate in the pre-school (85.1%) group compared to the school group (94.6%) (p=0.032). However, no significant differences (p=0.575) were found when gender comparisons were performed. Conclusions: The manovacuometry test showed a high success rate in both preschool and school population assessed. Furthermore, the rate of success appears to be related to aging. PMID:26137867

  1. Strength and fatigue life evaluation of composite laminate with embedded sensors

    NASA Astrophysics Data System (ADS)

    Rathod, Vivek T.; Hiremath, S. R.; Roy Mahapatra, D.

    2014-04-01

    Prognosis regarding durability of composite structures using various Structural Health Monitoring (SHM) techniques is an important and challenging topic of research. Ultrasonic SHM systems with embedded transducers have potential application here due to their instant monitoring capability, compact packaging potential toward unobtrusiveness and noninvasiveness as compared to non-contact ultrasonic and eddy current techniques which require disassembly of the structure. However, embedded sensors pose a risk to the structure by acting as a flaw thereby reducing life. The present paper focuses on the determination of strength and fatigue life of the composite laminate with embedded film sensors like CNT nanocomposite, PVDF thin films and piezoceramic films. First, the techniques of embedding these sensors in composite laminates is described followed by the determination of static strength and fatigue life at coupon level testing in Universal Testing Machine (UTM). Failure mechanisms of the composite laminate with embedded sensors are studied for static and dynamic loading cases. The coupons are monitored for loading and failure using the embedded sensors. A comparison of the performance of these three types of embedded sensors is made to study their suitability in various applications. These three types of embedded sensors cover a wide variety of applications, and prove to be viable in embedded sensor based SHM of composite structures.

  2. Remote laser cutting of CFRP: influence of the edge quality on fatigue strength

    NASA Astrophysics Data System (ADS)

    Stock, Johannes W.; Zaeh, Michael F.; Spaeth, Justinian P.

    2014-02-01

    The additional weight of the batteries in electric cars can be compensated by using carbon fiber reinforced plastics (CFRP) for structural parts of the passenger cell. Various machining processes for CFRP are currently subject to investigations. Milling and abrasive waterjet cutting implicate fiber pull out or delamination and, thus, do not thoroughly meet the requirements for mass production. Despite this, laser beam cutting has a great potential in large scale cutting of CFRP and is a predominant research topic. Remote laser beam cutting especially provides a good cut surface quality. Currently, the correlation between cutting parameters and edge quality is not sufficiently known. In particular, studies on the dynamic strength of remote laser cut parts are missing. Therefore, fatigue testing was performed with specimens cut by laser radiation and the results were compared with others made by milling and abrasive waterjet cutting. With these experiments, a comparable study of the different methods of CFRP cutting was achieved. The influence of both the heat affected zone (HAZ) and of defects like micro-fissures on the fatigue strength were evaluated.

  3. Serial Changes of Quadriceps and Hamstring Muscle Strength Following Total Knee Arthroplasty: A Meta-Analysis

    PubMed Central

    Ahn, Hyeong-Sik; Lee, Dae-Hee

    2016-01-01

    This meta-analysis was performed to analyze serial changes in thigh muscles, including quadriceps and hamstring muscles, from before to one year after total knee arthroplasty (TKA). All studies sequentially comparing isokinetic quadriceps and hamstring muscle strengths between the TKA side and the contralateral uninjured limb were included in this meta-analysis. Five studies with 7 cohorts were included in this meta-analysis. The mean differences in the strengths of quadriceps and hamstring muscles between the TKA and uninjured sides were greatest three months after surgery (26.8 N∙m, 12.8 N∙m, P<0.001), but were similar to preoperative level at six months (18.4 N∙m, 7.4 N∙m P<0.001) and were maintained for up to one year (15.9 N∙m, 4.1 N∙m P<0.001). The pooled mean differences in changes in quadriceps and hamstring strengths relative to preoperative levels were 9.2 N∙m and 4.9 N∙m, respectively, three months postoperatively (P = 0.041), but were no longer significant after six months and one year. During the year after TKA, quadriceps and hamstring muscle strengths were lowest after 3 months, recovering to preoperative level after six months, but not reaching the muscle strength on the contralateral side. Relative to preoperative levels, the difference in muscle strength between the TKA and contralateral knees was only significant at three months. Because decrease of strength of the quadriceps was significantly greater than decrease in hamstring muscle strength at postoperative three months, early rehabilitation after TKA should focus on recovery of quadriceps muscle strength. PMID:26849808

  4. Strategies for Rapid Muscle Fatigue Reduction during FES Exercise in Individuals with Spinal Cord Injury: A Systematic Review

    PubMed Central

    Ibitoye, Morufu Olusola; Hamzaid, Nur Azah; Hasnan, Nazirah; Abdul Wahab, Ahmad Khairi; Davis, Glen M.

    2016-01-01

    Background Rapid muscle fatigue during functional electrical stimulation (FES)-evoked muscle contractions in individuals with spinal cord injury (SCI) is a significant limitation to attaining health benefits of FES-exercise. Delaying the onset of muscle fatigue is often cited as an important goal linked to FES clinical efficacy. Although the basic concept of fatigue-resistance has a long history, recent advances in biomedical engineering, physiotherapy and clinical exercise science have achieved improved clinical benefits, especially for reducing muscle fatigue during FES-exercise. This review evaluated the methodological quality of strategies underlying muscle fatigue-resistance that have been used to optimize FES therapeutic approaches. The review also sought to synthesize the effectiveness of these strategies for persons with SCI in order to establish their functional impacts and clinical relevance. Methods Published scientific literature pertaining to the reduction of FES-induced muscle fatigue was identified through searches of the following databases: Science Direct, Medline, IEEE Xplore, SpringerLink, PubMed and Nature, from the earliest returned record until June 2015. Titles and abstracts were screened to obtain 35 studies that met the inclusion criteria for this systematic review. Results Following the evaluation of methodological quality (mean (SD), 50 (6) %) of the reviewed studies using the Downs and Black scale, the largest treatment effects reported to reduce muscle fatigue mainly investigated isometric contractions of limited functional and clinical relevance (n = 28). Some investigations (n = 13) lacked randomisation, while others were characterised by small sample sizes with low statistical power. Nevertheless, the clinical significance of emerging trends to improve fatigue-resistance during FES included (i) optimizing electrode positioning, (ii) fine-tuning of stimulation patterns and other FES parameters, (iii) adjustments to the mode and

  5. A two-parameter model to predict fatigue life of high-strength steels in a very high cycle fatigue regime

    NASA Astrophysics Data System (ADS)

    Sun, Chengqi; Liu, Xiaolong; Hong, Youshi

    2015-06-01

    In this paper, ultrasonic (20 kHz) fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue (VHCF) regime. Experimental results showed that for most tested specimens failed in a VHCF regime, a fatigue crack originated from the interior of specimen with a fish-eye pattern, which contained a fine granular area (FGA) centered by an inclusion as the crack origin. Then, a two-parameter model is proposed to predict the fatigue life of high-strength steels with fish-eye mode failure in a VHCF regime, which takes into account the inclusion size and the FGA size. The model was verified by the data of present experiments and those in the literature. Furthermore, an analytic formula was obtained for estimating the equivalent crack growth rate within the FGA. The results also indicated that the stress intensity factor range at the front of the FGA varies within a small range, which is irrespective of stress amplitude and fatigue life.

  6. The effect of weld porosity on the cryogenic fatigue strength of ELI grade Ti-5Al-2.5Sn

    NASA Technical Reports Server (NTRS)

    Rogers, P. R.; Lambdin, R. C.; Fox, D. E.

    1992-01-01

    The effect of weld porosity on the fatigue strength of ELI grade Ti-5Al-2.5Sn at cryogenic temperature was determined. A series of high cycle fatigue (HCF) and tensile tests were performed at -320 F on specimens made from welded sheets of the material. All specimens were tested with weld beads intact and some amount of weld offset. Specimens containing porosity and control specimens containing no porosity were tested. Results indicate that for the weld configuration tested, the fatigue life of the material is not affected by the presence of spherical embedded pores.

  7. Localized Electrical Impedance Myography of the Biceps Brachii Muscle during Different Levels of Isometric Contraction and Fatigue

    PubMed Central

    Li, Le; Shin, Henry; Li, Xiaoyan; Li, Sheng; Zhou, Ping

    2016-01-01

    This study assessed changes in electrical impedance myography (EIM) at different levels of isometric muscle contraction as well as during exhaustive exercise at 60% maximum voluntary contraction (MVC) until task failure. The EIM was performed on the biceps brachii muscle of 19 healthy subjects. The results showed that there was a significant difference between the muscle resistance (R) measured during the isometric contraction and when the muscle was completely relaxed. Post hoc analysis shows that the resistance increased at higher contractions (both 60% MVC and MVC), however, there were no significant changes in muscle reactance (X) during the isometric contractions. The resistance also changed during different stages of the fatigue task and there were significant decreases from the beginning of the contraction to task failure as well as between task failure and post fatigue rest. Although our results demonstrated an increase in resistance during isometric contraction, the changes were within 10% of the baseline value. These changes might be related to the modest alterations in muscle architecture during a contraction. The decrease in resistance seen with muscle fatigue may be explained by an accumulation of metabolites in the muscle tissue. PMID:27110795

  8. Localized Electrical Impedance Myography of the Biceps Brachii Muscle during Different Levels of Isometric Contraction and Fatigue.

    PubMed

    Li, Le; Shin, Henry; Li, Xiaoyan; Li, Sheng; Zhou, Ping

    2016-01-01

    This study assessed changes in electrical impedance myography (EIM) at different levels of isometric muscle contraction as well as during exhaustive exercise at 60% maximum voluntary contraction (MVC) until task failure. The EIM was performed on the biceps brachii muscle of 19 healthy subjects. The results showed that there was a significant difference between the muscle resistance (R) measured during the isometric contraction and when the muscle was completely relaxed. Post hoc analysis shows that the resistance increased at higher contractions (both 60% MVC and MVC), however, there were no significant changes in muscle reactance (X) during the isometric contractions. The resistance also changed during different stages of the fatigue task and there were significant decreases from the beginning of the contraction to task failure as well as between task failure and post fatigue rest. Although our results demonstrated an increase in resistance during isometric contraction, the changes were within 10% of the baseline value. These changes might be related to the modest alterations in muscle architecture during a contraction. The decrease in resistance seen with muscle fatigue may be explained by an accumulation of metabolites in the muscle tissue. PMID:27110795

  9. Relation between systemic inflammatory markers, peripheral muscle mass, and strength in limb muscles in stable COPD patients

    PubMed Central

    Ferrari, Renata; Caram, Laura MO; Faganello, Marcia M; Sanchez, Fernanda F; Tanni, Suzana E; Godoy, Irma

    2015-01-01

    The aim of this study was to investigate the association between systemic inflammatory mediators and peripheral muscle mass and strength in COPD patients. Fifty-five patients (69% male; age: 64±9 years) with mild/very severe COPD (defined as forced expiratory volume in the first second [FEV1] =54%±23%) were evaluated. We evaluated serum concentrations of IL-8, CRP, and TNF-α. Peripheral muscle mass was evaluated by computerized tomography (CT); midthigh cross-sectional muscle area (MTCSA) and midarm cross-sectional muscle area (MACSA) were obtained. Quadriceps, triceps, and biceps strength were assessed through the determination of the one-repetition maximum. The multiple regression results, adjusted for age, sex, and FEV1%, showed positive significant association between MTCSA and leg extension (0.35 [0.16, 0.55]; P=0.001), between MACSA and triceps pulley (0.45 [0.31, 0.58]; P=0.001), and between MACSA and biceps curl (0.34 [0.22, 0.47]; P=0.001). Plasma TNF-α was negatively associated with leg extension (−3.09 [−5.99, −0.18]; P=0.04) and triceps pulley (−1.31 [−2.35, −0.28]; P=0.01), while plasma CRP presented negative association with biceps curl (−0.06 [−0.11, −0.01]; P=0.02). Our results showed negative association between peripheral muscle mass (evaluated by CT) and muscle strength and that systemic inflammation has a negative influence in the strength of specific groups of muscles in individuals with stable COPD. This is the first study showing association between systemic inflammatory markers and strength in upper limb muscles. PMID:26345641

  10. Relationships between Lower Limb Muscle Strength and Locomotor Capacity in Children and Adolescents with Cerebral Palsy Who Walk Independently

    ERIC Educational Resources Information Center

    Ferland, Chantale; Lepage, Celine; Moffet, Helene; Maltais, Desiree B.

    2012-01-01

    This study aimed to quantify relationships between lower limb muscle strength and locomotor capacity for children and adolescents with cerebral palsy (CP) to identify key muscle groups for strength training. Fifty 6- to 16-year-olds with CP (Gross Motor Function Classification System level I or II) participated. Isometric muscle strength of hip…

  11. Rats Bred for Low Aerobic Capacity Become Promptly Fatigued and Have Slow Metabolic Recovery after Stimulated, Maximal Muscle Contractions

    PubMed Central

    Torvinen, Sira; Silvennoinen, Mika; Piitulainen, Harri; Närväinen, Johanna; Tuunanen, Pasi; Gröhn, Olli; Koch, Lauren G.; Britton, Steven L.; Kainulainen, Heikki

    2012-01-01

    AIM Muscular fatigue is a complex phenomenon affected by muscle fiber type and several metabolic and ionic changes within myocytes. Mitochondria are the main determinants of muscle oxidative capacity which is also one determinant of muscle fatigability. By measuring the concentrations of intracellular stores of high-energy phosphates it is possible to estimate the energy production efficiency and metabolic recovery of the muscle. Low intrinsic aerobic capacity is known to be associated with reduced mitochondrial function. Whether low intrinsic aerobic capacity also results in slower metabolic recovery of skeletal muscle is not known. Here we studied the influence of intrinsic aerobic capacity on in vivo muscle metabolism during maximal, fatiguing electrical stimulation. METHODS Animal subjects were genetically heterogeneous rats selectively bred to differ for non–trained treadmill running endurance, low capacity runners (LCRs) and high capacity runners (HCRs) (n = 15–19). We measured the concentrations of major phosphorus compounds and force parameters in a contracting triceps surae muscle complex using 31P-Magnetic resonance spectroscopy (31P-MRS) combined with muscle force measurement from repeated isometric twitches. RESULTS Our results demonstrated that phosphocreatine re-synthesis after maximal muscle stimulation was significantly slower in LCRs (p<0.05). LCR rats also became promptly fatigued and maintained the intramuscular pH poorly compared to HCRs. Half relaxation time (HRT) of the triceps surae was significantly longer in LCRs throughout the stimulation protocol (p≤0.05) and maximal rate of torque development (MRTD) was significantly lower in LCRs compared to HCRs from 2 min 30 s onwards (p≤0.05). CONCLUSION We observed that LCRs are more sensitive to fatigue and have slower metabolic recovery compared to HCRs after maximal muscle contractions. These new findings are associated with reduced running capacity and with previously found lower

  12. Measurement of muscle strength with handheld dynamometer in Intensive Care Unit

    PubMed Central

    Samosawala, Nidhi R.; Vaishali, K.; Kalyana, B. Chakravarthy

    2016-01-01

    Background: Intensive Care Unit (ICU) acquired weakness is a common complication in critically ill patients affecting their prognosis. The handheld dynamometry is an objective method in detecting minimum muscle strength change, which has an impact on the physical function of ICU survivors. The minimal change in the force can be measured in units of weight such as pounds or kilograms. Aim of the Study: To detect the changes in peripheral muscle strength with handheld dynamometer in the early stage of ICU stay and to observe the progression of muscle weakness. Methodology: Three upper and three lower limb muscles force measured with handheld dynamometer during ICU stay. Data were analyzed using repeated measures ANOVA to detect changes in force generated by muscle on alternate days of ICU stay. Results: There was a reduction in peripheral muscle strength from day 3 to day 5 as well from day 5 to day 7 of ICU stay (P < 0.01). The average reduction in peripheral muscle strength was 11.8% during ICU stay. Conclusion: This study showed a progressive reduction in peripheral muscle strength as measured by handheld dynamometer during early period of ICU stay. PMID:26955213

  13. Effect of trapezius muscle strength on three-dimensional scapular kinematics

    PubMed Central

    Turgut, Elif; Duzgun, Irem; Baltaci, Gul

    2016-01-01

    [Purpose] This study aimed to investigate the effect of trapezius muscle isometric strength on three-dimensional scapular kinematics in asymptomatic shoulders. [Subjects and Methods] Thirty asymptomatic subjects were included to the study. Isometric strengths of the upper, middle, and lower trapezius muscle were measured using a handheld dynamometer. Three-dimensional scapular kinematics was recorded by an electromagnetic tracking device during frontal and sagittal plane elevation. For each muscle, the cut-off value for muscle strength was determined with the upper bound of the 95% confidence interval, and Student’s t-test was used to compare the scapular kinematics between subjects with relatively weaker or stronger trapezius muscles. [Results] Shoulders with stronger upper trapezius muscles showed greater upward scapular rotation at 30°, 60°, 90°, and 120° of elevation in the frontal plane. Shoulders with stronger middle trapezius had greater scapular upward rotation at 90° of elevation in the frontal plane. Shoulders with stronger lower trapezius showed greater scapular posterior tilt at 90° of elevation in the sagittal plane. [Conclusion] This study’s findings showed that isometric strength of the trapezius muscle affects upward scapular rotation and posterior tilt in asymptomatic shoulders. Therefore, trapezius muscle strength should be assessed and potential weakness should be addressed in shoulder rehabilitation programs. PMID:27390435

  14. Influence of cubic boron nitride grinding on the fatigue strengths of carbon steels and a nickel-base superalloy

    SciTech Connect

    Kawagoishi, N.; Chen, Q.; Kondo, E.; Goto, M.; Nisitani, H.

    1999-04-01

    The influence of cubic boron nitride (CBN) grinding on fatigue strength was investigated on an annealed carbon steel, a quenched and tempered carbon steel at room temperature, and a nickel-base superalloy, Inconel 718, at room temperature and 500 C. The results were discussed from several viewpoints, including surface roughness, residual stress, and work hardening or softening due to CBN grinding. The fatigue strength increased upon CBN grinding at room temperature, primarily because of the generation of compressive residual stress in the surface region. However, in the case of Inconel 718, this marked increase in the fatigue strength tended to disappear at the elevated temperature due to the release of compressive residual stress and the decrease of crack growth resistance at an elevated temperature.

  15. Residual strength and crack propagation tests on C-130 airplane center wings with service-imposed fatigue damage

    NASA Technical Reports Server (NTRS)

    Snider, H. L.; Reeder, F. L.; Dirkin, W. J.

    1972-01-01

    Fourteen C-130 airplane center wings, each containing service-imposed fatigue damage resulting from 4000 to 13,000 accumulated flight hours, were tested to determine their fatigue crack propagation and static residual strength characteristics. Eight wings were subjected to a two-step constant amplitude fatigue test prior to static testing. Cracks up to 30 inches long were generated in these tests. Residual static strengths of these wings ranged from 56 to 87 percent of limit load. The remaining six wings containing cracks up to 4 inches long were statically tested as received from field service. Residual static strengths of these wings ranged from 98 to 117 percent of limit load. Damage-tolerant structural design features such as fastener holes, stringers, doublers around door cutouts, and spanwise panel splices proved to be effective in retarding crack propagation.

  16. Respiratory muscle injury, fatigue and serum skeletal troponin I in rat

    PubMed Central

    Simpson, Jeremy A; Van Eyk, Jennifer; Iscoe, Steve

    2004-01-01

    To evaluate injury to respiratory muscles of rats breathing against an inspiratory resistive load, we measured the release into blood of a myofilament protein, skeletal troponin I (sTnI), and related this release to the time course of changes in arterial blood gases, respiratory drive (phrenic activity), and pressure generation. After ∼1.5 h of loading, hypercapnic ventilatory failure occurred, coincident with a decrease in the ratio of transdiaphragmatic pressure to integrated phrenic activity (Pdi/∫Phr) during sighs. This was followed at ∼1.9 h by a decrease in the Pdi/∫Phr ratio during normal loaded breaths (diaphragmatic fatigue). Loading was terminated at pump failure (a decline of Pdi to half of steady-state loaded values), ∼2.4 h after load onset. During 30 s occlusions post loading, rats generated pressure profiles similar to those during occlusions before loading, with comparable blood gases, but at a higher neural drive. In a second series of rats, we tested for sTnI release using Western blot–direct serum analysis of blood samples taken before and during loading to pump failure. We detected only the fast isoform of sTnI, release beginning midway through loading. Differential detection with various monoclonal antibodies indicated the presence of modified forms of fast sTnI. The release of fast sTnI is consistent with load-induced injury of fast glycolytic fibres of inspiratory muscles, probably the diaphragm. Characterization of released fast sTnI may provide insights into the molecular basis of respiratory muscle dysfunction; fast sTnI may also prove useful as a marker of impending respiratory muscle fatigue. PMID:14673191

  17. Effects of stress concentration on the fatigue strength of 7003-T5 aluminum alloy butt joints with weld reinforcement

    NASA Astrophysics Data System (ADS)

    Zhu, Zongtao; Li, Yuanxing; Zhang, Mingyue; Hui, Chen

    2015-03-01

    7003-T5 Aluminum (Al) alloy plates with a thickness of 5 mm are welded by gas metal arc welding (GMAW) method in this work. In order to investigate the influence of stress concentration introduced by weld reinforcement on fatigue strength, the stress concentration factor of the butt joint is calculated. Microscopic and X-ray techniques were utilized to make sure there are no weld defects with large size in butt weld, which can induce extra stress concentration. The cyclic stress - number of cycles to failure (S-N) curves of the joints with and without the welder were obtained by fatigue testing, and the results show that the fatigue strength of 7003-T5 Al alloy butt joints with the weld reinforcement is 50 MPa, which is only 45% of the joints without the weld reinforcement. Fracture surface observation indicated that the fatigue source and propagation are dissimilar for the specimens with and without the welder due to the stress concentration at the weld root. The stress concentration with a factor of 1.7 has great effect on the fatigue strength, but little influence on the tensile strength.

  18. Description of Peripheral Muscle Strength Measurement and Correlates of Muscle Weakness in Patients Receiving Prolonged Mechanical Ventilatory Support

    PubMed Central

    Chlan, Linda L.; Tracy, Mary Fran; Guttormson, Jill; Savik, Kay

    2015-01-01

    Background Intensive Care Unit Acquired Weakness (ICUAW) is a frequent complication of critical illness due to immobility and prolonged mechanical ventilatory support. Objectives To describe daily peripheral muscle strength measurement in ventilated patients and explore relationships among factors that influence ICUAW. Methods Peripheral muscle strength of 120 ventilated ICU patients (mean age 59.8 ± 15.1; 51% female; APACHE III 61.3 ± 20.7; ICU stay 10.6 ± 8.6 days) was measured daily using a standardized hand grip dynamometry protocol. Three grip measurements for each hand were recorded in pounds-force; the mean of these three assessments was used in the analysis. Correlates of ICUAW were analyzed with mixed models to explore their relationship to grip strength (age, gender, illness severity, length of ventilatory support, medications). Results Median baseline grip strength was variable yet diminished (7.7; 0-102) with either a pattern of diminishing grip strength or maintenance of the baseline low grip strength over time. Controlling for days on protocol, female gender [β = −10.4(2.5); p = <.001], age [= −.24(.08); p = .004], and days receiving ventilatory support [= −.34(.12); p = .005] explained a significant amount of variance in grip strength over time. Conclusions Patients receiving prolonged periods of mechanical ventilatory support in this sample show marked decrements in grip strength measured by hand dynamometry, a marker for peripheral muscle strength. Hand dynamometry is a reliable method to measure muscle strength in cooperative ICU patients and can be used in future research to ultimately develop interventions to prevent ICUAW. PMID:26523017

  19. The Effects of Cervical Muscle Fatigue on Balance – A Study with Elite Amateur Rugby League Players

    PubMed Central

    Gosselin, Guy; Fagan, Michael J.

    2014-01-01

    Neck muscle fatigue has been shown to alter an individual’s balance in a similar way to that reported in subjects suffering from neck pain or subjects that have suffered a neck injury. The main purpose of the present study was to quantify the effects of neck fatigue on neck muscle electromyography (EMG) activity, balance, perceived fatigue and perceived stability. Forty four elite amateur rugby league players resisted with their neck muscles approximately 35% maximum voluntary isometric contraction (MVIC) force for 15 minutes in eight different directions. Sway velocity and surface electromyography were measured. Questionnaires were used to record perceived effort and stability. Repeated measures ANOVA showed that after 15 minutes isometric contraction, significant changes were seen in sway velocity, perceived sway and EMG median frequency. There were no differences in perceived efforts. The changes in sway velocity and median frequency were more pronounced after extension and right and left posterior oblique contractions but there was no significant difference in sway velocity after contraction in the right lateral flexion, right anterior oblique and left anterior oblique direction of contraction. All the subjects showed oriented whole-body leaning in the plane of the contraction. The experiment produced significantly altered and perceived altered balance in this group of physically fit individuals. The results may contribute to our understanding of normal functional capacities of athletes and will provide a basis for further investigation in healthy non-athletes and participants that have suffered neck injuries. This may ultimately help develop accurate and valid rehabilitation outcome measures. Key points Using a percentage of MVIC permits to proportionally fatigue various neck muscle groups evenly Fatigue of different neck muscle groups will alter balance differently Fatigue of muscles producing extension and posterior oblique will alter balance the most

  20. Effect of ingested sodium bicarbonate on muscle force, fatigue, and recovery.

    PubMed

    Verbitsky, O; Mizrahi, J; Levin, M; Isakov, E

    1997-08-01

    The influence of acute ingestion of NaHCO3 on fatigue and recovery of teh quadriceps femoris muscle after exercise was studied in six healthy male subjects. A bicycle ergometer was used for exercising under three loading conditions: test A, load corresponding to maximal oxygen consumption; test B, load in test A + 17%; test C, load in test B but performed 1 h after acute ingestion of NaHCO3. Functional electrical stimulation (FES) was applied to provoke isometric contraction of the quadriceps femoris. The resulting knee torque was monitored during fatigue (2-min chronic FES) and recovery (10-s FES every 10 min, for 40 min). Quadriceps torques were higher in the presence of NaHCO3 (P < 0.05): with NaHCO3 the peak, residual, and recovery (after 40 min) normalized torques were, respectively, 0.68 +/- 0.05 (SD), 0.58 +/- 0.05, and 0.73 +/- 0.05; without NaHCO3 the values were 0.45 +/- 0.04, 0.30 +/- 0.06, and 0.63 +/- 0.06. The increased torques obtained after acute ingestion of NaHCO3 indicate the possible existence of improved nonoxidative glycolysis in isometric contraction, resulting in reduced fatigue and enhanced recovery. PMID:9296948

  1. Effect of Progressive Muscle Relaxation on the Fatigue and Quality of Life Among Iranian Aging Persons.

    PubMed

    Hassanpour-Dehkordi, Ali; Jalali, Amir

    2016-07-01

    Since the elderly population is increasing rapidly in developing countries which may decrease the physical activity and exercise and in turn could affect the elderly's quality of life, this study aimed to investigate the effect of progressive muscle relaxation on the elderly's quality of life in Iran. In a randomized clinical trial, participants were randomly divided into intervention and control groups. For the intervention group, muscular progressive relaxation was run three days per week for three months (totally 36 sessions). In relaxation, a patient contract a group of his/her muscles in each step and relaxes them after five seconds and finally loosens all muscles and takes five deep breaths. Each session lasts for 45 minutes. The instrument of data gathering consisted of questionnaires on individual's demographic data and quality of life SF-36. After intervention, quality of life increased significantly in the patients undergoing muscular progressive relaxation and fatigue severity decreased significantly in the intervention group compared to prior to intervention. In addition, there was a statistically significant difference in mean score of physical performance, restricted activity after physical problem, energy, socially function, physical pain, overall hygiene, and quality of life between intervention and control groups. By implementing regular and continuous progressive muscle relaxation, quality of life could be increased in different dimensions in the elderly and the context could be provided to age healthily and enjoy higher health and autonomy. Therefore, all of the therapeutic staffs are recommended to implement this plan to promote the elderly's quality of life. PMID:27424013

  2. Reduced Neck Muscle Strength and Altered Muscle Mechanical Properties in Cervical Dystonia Following Botulinum Neurotoxin Injections: A Prospective Study

    PubMed Central

    Mustalampi, Sirpa; Ylinen, Jari; Korniloff, Katariina; Weir, Adam; Häkkinen, Arja

    2016-01-01

    Objective To evaluate changes in the strength and mechanical properties of neck muscles and disability in patients with cervical dystonia (CD) during a 12-week period following botulinum neurotoxin (BoNT) injections. Methods Eight patients with CD volunteered for this prospective clinical cohort study. Patients had received BoNT injections regularly in neck muscles at three-month intervals for several years. Maximal isometric neck strength was measured by a dynamometer, and the mechanical properties of the splenius capitis were evaluated using two myotonometers. Clinical assessment was performed using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) before and at 2, 4, 8, and 12 weeks after the BoNT injections. Results Mean maximal isometric neck strength at two weeks after the BoNT injections decreased by 28% in extension, 25% in rotation of the affected side and 17% in flexion. At four weeks, muscle stiffness of the affected side decreased by 17% and tension decreased by 6%. At eight weeks, the muscle elasticity on the affected side increased by 12%. At two weeks after the BoNT injections, the TWSTRS-severity and TWSTRS-total scores decreased by 4.3 and 6.4, respectively. The strength, muscle mechanical properties and TWSTRS scores returned to baseline values at 12 weeks. Conclusions Although maximal neck strength and muscle tone decreased after BoNT injections, the disability improved. The changes observed after BoNT injections were temporary and returned to pre-injection levels within twelve weeks. Despite having a possible negative effect on function and decreasing neck strength, the BoNT injections improved the patients reported disability. PMID:26828215

  3. Muscle fatigue in frog semitendinosus: role of intracellular pH.

    PubMed

    Thompson, L V; Balog, E M; Fitts, R H

    1992-06-01

    The purpose of this study was to utilize glass microelectrodes to characterize the intracellular pH (pHi) before and during recovery from fatigue in the frog semitendinosus (ST) muscle. A second objective was to evaluate the relationship between pHi and contractile function. The frog ST muscle (22 degrees C) was fatigued by direct electrical stimulation with 100-ms 150-Hz trains at 1/s for 5 min. Peak tetanic force (Po) was reduced to 8.5% of initial force and recovered in a biphasic manner, returning to the resting value by 40 min. Resting pHi was 7.00 +/- 0.02 (n = 37) and declined with fatigue to an average value of 6.42 at 3 min of recovery. During recovery pHi significantly increased and by 25 min had returned to the prefatigue value. The pHi recovery was highly correlated to the slow phase of Po recovery (r = 0.98, P less than 0.001). The mean resting membrane potential was -78 +/- 1.0 mV (n = 42) and at 3 min of recovery was depolarized to -67 +/- 4 mV. Both the peak rate of twitch force development (+dP/dt) (r = 0.99, P less than 0.001) and decline (-dP/dt) (r = 0.94, P less than 0.014) were highly correlated to pHi during the slow phase of recovery. Contraction time (CT) and one-half relaxation time (1/2RT) increased significantly and recovered exponentially. The recovery of CT and 1/2RT were both significantly correlated to pHi (r = -0.93, P less than 0.001 and r = -0.86, P less than 0.001 for CT and 1/2RT, respectively).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1616012

  4. Muscle fatigue in frog semitendinosus: role of intracellular pH

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    The purpose of this study was to utilize glass microelectrodes to characterize the intracellular pH (pHi) before and during recovery from fatigue in the frog semitendinosus (ST) muscle. A second objective was to evaluate the relationship between pHi and contractile function. The frog ST muscle (22 degrees C) was fatigued by direct electrical stimulation with 100-ms 150-Hz trains at 1/s for 5 min. Peak tetanic force (Po) was reduced to 8.5% of initial force and recovered in a biphasic manner, returning to the resting value by 40 min. Resting pHi was 7.00 +/- 0.02 (n = 37) and declined with fatigue to an average value of 6.42 at 3 min of recovery. During recovery pHi significantly increased and by 25 min had returned to the prefatigue value. The pHi recovery was highly correlated to the slow phase of Po recovery (r = 0.98, P less than 0.001). The mean resting membrane potential was -78 +/- 1.0 mV (n = 42) and at 3 min of recovery was depolarized to -67 +/- 4 mV. Both the peak rate of twitch force development (+dP/dt) (r = 0.99, P less than 0.001) and decline (-dP/dt) (r = 0.94, P less than 0.014) were highly correlated to pHi during the slow phase of recovery. Contraction time (CT) and one-half relaxation time (1/2RT) increased significantly and recovered exponentially. The recovery of CT and 1/2RT were both significantly correlated to pHi (r = -0.93, P less than 0.001 and r = -0.86, P less than 0.001 for CT and 1/2RT, respectively).(ABSTRACT TRUNCATED AT 250 WORDS).

  5. Protein Intake and Muscle Strength in Older Persons: Does Inflammation Matter?

    PubMed Central

    Bartali, Benedetta; Frongillo, Edward A.; Stipanuk, Martha H.; Bandinelli, Stefania; Salvini, Simonetta; Palli, Domenico; Morais, Jose A.; Volpato, Stefano; Guralnik, Jack M.; Ferrucci, Luigi

    2011-01-01

    BACKGROUND/OBJECTIVES The effect of dietary protein intake on muscle strength in older persons is unknown. The objective of this study was to examine whether protein intake is associated with change in muscle strength in older persons. Because systemic inflammation has been associated with protein catabolism, we also evaluated whethera synergistic effect exists between protein intake and inflammatory markers on change in muscle strength using a longitudinal study of community-dwelling persons aged 65 years or older. DESIGN Longitudinal. SETTING The InCHIANTI Study. PARTICIPANTS Five hundred and ninety-eight persons. MEASUREMENTS Knee extension strength was measured at baseline (1998–2000) and during 3-year follow-up (2001–2003) using a hand-held dynamometer. Protein intake was assessed using a very detailed food frequency questionnaire. The inflammatory markers included in this study were C-reactive protein (CRP), Interleukin-6 (IL-6), and Tumor Necrosis Factor-α (TNF-α). RESULTS The main effect of protein intake on change in muscle strength was not significant, but we found a significant interaction between protein intake and CRP, IL-6 and TNF-α (p=0.003, p=0.049 and p=0.019, respectively), indicating thata lower protein intake was associated with a greater decline in muscle strength in persons with high levels of inflammatory markers. CONCLUSION Selectively in older persons with a pro-inflammatory state, low protein intake was associated with accelerated decline in muscle strength. These results may help to understand the factors contributing to decline in muscle strength and to identify the target population of older persons who may benefit from nutritional interventions aimed at preventing or reducing age-associated muscle impairments and its detrimental consequences. PMID:22283208

  6. The effect of hip joint muscle exercise on muscle strength and balance in the knee joint after meniscal injury.

    PubMed

    Park, Sun Ja; Kim, Young Mi; Kim, Ha Roo

    2016-04-01

    [Purpose] This study aimed to evaluate the effect of hip muscle strengthening on muscle strength and balance in the knee joint after a meniscal injury. [Subjects and Methods] This randomized control study enrolled 24 patients who had undergone arthroscopic treatment after a meniscal injury and began a rehabilitative exercise program 8 weeks after surgery. Subjects were divided into 2 groups of 12 subjects each: gluteus medius resistance exercise group and control group. This study investigated muscle strength and balance in the knee joint flexor, extensor, and abductor during an 8-week period. [Results] Measurements of knee extensor muscle strength revealed no significant difference between the control group and the experimental group. Measurements of abductor muscle strength, however, identified a significant difference between the 2 groups. The groups did not differ significantly with regard to balance measurements. [Conclusion] The results of this study suggest that this subject should be approached in light of the correlation between the hip abductor and injury to the lower extremities. PMID:27190461

  7. The effect of hip joint muscle exercise on muscle strength and balance in the knee joint after meniscal injury

    PubMed Central

    Park, Sun Ja; Kim, Young Mi; Kim, Ha Roo

    2016-01-01

    [Purpose] This study aimed to evaluate the effect of hip muscle strengthening on muscle strength and balance in the knee joint after a meniscal injury. [Subjects and Methods] This randomized control study enrolled 24 patients who had undergone arthroscopic treatment after a meniscal injury and began a rehabilitative exercise program 8 weeks after surgery. Subjects were divided into 2 groups of 12 subjects each: gluteus medius resistance exercise group and control group. This study investigated muscle strength and balance in the knee joint flexor, extensor, and abductor during an 8-week period. [Results] Measurements of knee extensor muscle strength revealed no significant difference between the control group and the experimental group. Measurements of abductor muscle strength, however, identified a significant difference between the 2 groups. The groups did not differ significantly with regard to balance measurements. [Conclusion] The results of this study suggest that this subject should be approached in light of the correlation between the hip abductor and injury to the lower extremities. PMID:27190461

  8. Fatigue

    MedlinePlus

    ... chemotherapy and radiation Recovering from major surgery Anxiety, stress, or depression Staying up too late Drinking too much alcohol or too many caffeinated drinks Pregnancy One disorder that causes extreme fatigue is chronic ...

  9. Strength training improves muscle quality and insulin sensitivity in older Hispanics with type 2 diabetes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hispanics have an increased risk of morbidity and mortality due to their high prevalence of diabetes. Body composition, particularly skeletal muscle, plays an important role in glycemic control and lipid metabolism. Strength training is the most effective means to increase muscle mass but limited ...

  10. Changes in the muscle strength and functional performance of healthy women with aging

    PubMed Central

    Mousavikhatir, Roghayeh

    2012-01-01

    Background Lower limbs antigravity muscles weakness and decreased functional ability have significant role in falling. The aim of this study was to find the effects of aging on muscle strength and functional ability, determining the range of decreasing strength and functional ability and relationship between them in healthy women. Methods Across-section study was performed on 101 healthy women aged 21-80 years. The participants were divided into six age groups. The maximum isometric strength of four muscle groups was measured using a hand-held dynamometer bilaterally. The functional ability was measured with functional reach (FR), timed get up and go (TGUG), single leg stance (SLS), and stairs walking (SW) tests. Results Muscle strength changes were not significant between 21-40 years of age, but decreased significantly thereafter. Also, there was a significant relationship between muscle strength and functional ability in age groups. Conclusion Both muscle strength and functional ability is reduced as a result of aging, but the decrease in functional ability can be detected earlier. PMID:23482911

  11. The effect of strength training on muscle cellular stress in prostate cancer patients on ADT

    PubMed Central

    Thorsen, L; Kirkegaard, C; Ugelstad, I; Fosså, S D; Raastad, T

    2016-01-01

    Background Androgen deprivation therapy (ADT) for prostate cancer (PCa) is associated with several side effects, including loss of muscle mass. Muscle atrophy is associated with reduced mitochondrial function and increased muscle cellular stress that may be counteracted by strength training. Thus, the aim of this study was to investigate the effect of strength training on mitochondrial proteins and indicators of muscle cellular stress in PCa patients on ADT. Methods Men diagnosed with locally advanced PCa receiving ADT were randomised to a strength training group (STG) (n=16) or a control group (CG) (n=15) for 16 weeks. Muscle biopsies were collected pre- and post-intervention from the vastus lateralis muscle, and analysed for mitochondrial proteins (citrate synthase, cytochrome c oxidase subunit IV (COXIV), HSP60) and indicators of muscle cellular stress (heat shock protein (HSP) 70, alpha B-crystallin, HSP27, free ubiquitin, and total ubiquitinated proteins) using Western blot and ELISA. Results No significant intervention effects were observed in any of the mitochondrial proteins or indicators of muscle cellular stress. However, within-group analysis revealed that the level of HSP70 was reduced in the STG and a tendency towards a reduction in citrate synthase levels was observed in the CG. Levels of total ubiquitinated proteins were unchanged in both groups. Conclusion Although reduced HSP70 levels indicated reduced muscle cellular stress in the STG, the lack of an intervention effect precluded any clear conclusions. PMID:27169606

  12. A bi-dimensional index for the selective assessment of myoelectric manifestations of peripheral and central muscle fatigue.

    PubMed

    Mesin, Luca; Cescon, Corrado; Gazzoni, Marco; Merletti, Roberto; Rainoldi, Alberto

    2009-10-01

    Two physiological factors are assumed in this paper to mainly determine the myoelectric manifestations of fatigue: (1) the decrease of the conduction velocity (CV) of motor unit action potentials (MUAP) (peripheral fatigue), and (2) the increase of MU synchronization by the central nervous system (central fatigue). To describe separately the peripheral and central components of the myoelectric manifestations of fatigue, we investigated the following indexes: (1) mean spectral frequency - MNF, (2) median spectral frequency - MDF, (3) root mean square - RMS, (4) average rectified value - ARV, (5) estimation of muscle fiber conduction velocity - ECV, (6) percentage of determinism - %DET, (7) spectral indexes defined as the ratio between signal spectral moments - FI(k), (8) MNF estimated by autoregressive analysis - MNF(AR), (9) MNF estimated by Choi-Williams time-frequency representation - MNF(CWD), (10) MNF estimated by continuous wavelet transform - MNF(CWT), (11) signal entropy - S, (12) fractal dimension - FD. The indexes were tested with a set of synthetic EMG signals, with different CV distribution and level of MU synchronization. The indexes were calculated on epochs of 0.5s. It was observed that ECV is uncorrelated with the level of simulated synchronization (promising index of peripheral fatigue). On the other hand FD was the index least affected by CV changes and most related to the level of synchronism (promising index of central fatigue). A representative application to some experimental signals from vastus lateralis muscle during an isometric endurance test supported the results of the simulations. The vector (ECV, FD) is suggested to provide selective indications of peripheral and central fatigue. The description of EMG fatigue by a bi-dimensional vector opens new perspectives in the assessment of muscle properties, with potential application in both clinical and sport sciences. PMID:18824375

  13. Influence of Cervical Muscle Fatigue on Musculo-Tendinous Stiffness of the Head-Neck Segment during Cervical Flexion

    PubMed Central

    Portero, Raphaël; Quaine, Franck; Cahouet, Violaine; Léouffre, Marc; Servière, Christine; Portero, Pierre

    2015-01-01

    Aim The aim of this study is to determine if the fatigue of cervical muscles has a significant influence on the head-neck segment musculo-tendinous stiffness. Methods Ten men (aged 21.2 ± 1.9 years) performed four quick-release trials of flexion at 30 and 50% MVC before and after the induction of muscular fatigue on cervical flexors. Electromyographic activity was recorded on the sternocleidomastoids (SCM) and spinal erectors (SE), bilaterally. Musculo-tendinous stiffness was calculated through the quick-release method adapted to the head-neck segment. Results We noticed a significant linear increase of the head-neck segment musculo-tendinous stiffness with the increase of exertion level both before (P < 0.0001) and after the fatigue procedure (P < 0.0001). However, this linear relationship was not different before and after the fatigue procedure. EMG analysis revealed a significant increase of the root mean square for the right SCM (P = 0.0002), the left SCM (P < 0.0001), the right SE (P < 0.0001), and the left SE (P < 0.0001) and a significant decrease of the median power frequency only for the right (P = 0.0006) and the left (P = 0.0003) SCM with muscular fatigue. Discussion We did not find significant changes in the head-neck segment musculo-tendinous stiffness with fatigue of cervical muscles. We found a significant increase in EMG activity in the SCM and the SE after the induction of fatigue of the SCM. Our findings suggest that with fatigue of cervical flexors, neck muscle activity is modulated in order to maintain the musculo-tendinous stiffness at a steady state. PMID:26418000

  14. In Vivo Noninvasive Analysis of Human Forearm Muscle Function and Fatigue: Applications to EVA Operations and Training Maneuvers

    NASA Technical Reports Server (NTRS)

    Fotedar, L. K.; Marshburn, T.; Quast, M. J.; Feeback, D. L.

    1999-01-01

    Forearm muscle fatigue is one of the major limiting factors affecting endurance during performance of deep-space extravehicular activity (EVA) by crew members. Magnetic resonance (MR) provides in vivo noninvasive analysis of tissue level metabolism and fluid exchange dynamics in exercised forearm muscles through the monitoring of proton magnetic resonance imaging (MRI) and phosphorus magnetic resonance spectroscopy (P-31-MRS) parameter variations. Using a space glove box and EVA simulation protocols, we conducted a preliminary MRS/MRI study in a small group of human test subjects during submaximal exercise and recovery and following exhaustive exercise. In assessing simulated EVA-related muscle fatigue and function, this pilot study revealed substantial changes in the MR image longitudinal relaxation times (T2) as an indicator of specific muscle activation and proton flux as well as changes in spectral phosphocreatine-to-phosphate (PCr/Pi) levels as a function of tissue bioenergetic potential.

  15. High fatigue strength and enhanced biocompatibility of UFG CP Ti for medical innovative applications

    NASA Astrophysics Data System (ADS)

    Polyakov, A. V.; Semenova, I. P.; Valiev, R. Z.

    2014-08-01

    This study is focused on the fatigue properties of the UFG Ti Grade 4 and its biocompatibility. The UFG titanium was produced by ECAP-Conform in combination with subsequent drawing, which allows fabricating rods of up to 3 mm suitable for industrial applications. The endurance limit of smooth and notched samples of UFG Ti is considerably higher than in conventional Ti. The UFG Ti also demonstrates an increased capacity of human osteoblast-like U2OS cells to colonize and, therefore, better osseointegration. Torsional strength of standard Ti-6Al-7Nb products and UFG Ti Grade 4 products was evaluated. An advantage of the UFG titanium over the conventional coarse-grained material was shown.

  16. Go4Life:Strength | NIH MedlinePlus the Magazine

    MedlinePlus

    ... breath during strength exercises. Holding your breath while straining can cause changes in blood pressure. Breathe in ... Muscle soreness lasting a few days and slight fatigue are normal after muscle-building exercises, at least ...

  17. Effect of duration of smartphone use on muscle fatigue and pain caused by forward head posture in adults.

    PubMed

    Kim, Seong-Yeol; Koo, Sung-Ja

    2016-06-01

    [Purpose] The effect of duration of smartphone use on neck and shoulder muscle fatigue and pain was investigated in adults with forward head posture. [Subjects and Methods] Thirty-four adults with forward head posture were classified into groups by duration of smartphone use: 11 used a smartphone for 10 minutes each (group 1), 12 for 20 minutes each (group 2), and 11 for 30 minutes each (group 3). Fatigue cervical erector spinae and upper trapezius muscles was measured by electromyography, and pain before and after the experiment was evaluated using Visual Analog Scale (VAS) scores. [Results] There was a significant difference in the degree of fatigue in the left upper trapezius muscles in group 2 and left cervical erector spinae and bilateral upper trapeziuses group 3. There was a significant difference in fatigue in the left upper trapezius in groups 1 and 3. The VAS showed significant differences in all groups before and after the experiment and between groups 1 and 3. [Conclusion] Pain and fatigue worsened with longer smartphone use. This study provided data on the proper duration of smartphone use. Correct posture and breaks of at least 20 minutes are recommend when using smartphones. PMID:27390391

  18. Effect of duration of smartphone use on muscle fatigue and pain caused by forward head posture in adults

    PubMed Central

    Kim, Seong-Yeol; Koo, Sung-Ja

    2016-01-01

    [Purpose] The effect of duration of smartphone use on neck and shoulder muscle fatigue and pain was investigated in adults with forward head posture. [Subjects and Methods] Thirty-four adults with forward head posture were classified into groups by duration of smartphone use: 11 used a smartphone for 10 minutes each (group 1), 12 for 20 minutes each (group 2), and 11 for 30 minutes each (group 3). Fatigue cervical erector spinae and upper trapezius muscles was measured by electromyography, and pain before and after the experiment was evaluated using Visual Analog Scale (VAS) scores. [Results] There was a significant difference in the degree of fatigue in the left upper trapezius muscles in group 2 and left cervical erector spinae and bilateral upper trapeziuses group 3. There was a significant difference in fatigue in the left upper trapezius in groups 1 and 3. The VAS showed significant differences in all groups before and after the experiment and between groups 1 and 3. [Conclusion] Pain and fatigue worsened with longer smartphone use. This study provided data on the proper duration of smartphone use. Correct posture and breaks of at least 20 minutes are recommend when using smartphones. PMID:27390391

  19. The effects of kinesio taping on architecture, strength and pain of muscles in delayed onset muscle soreness of biceps brachii

    PubMed Central

    Lee, Yong Sin; Bae, Sea Hyun; Hwang, Jin Ah; Kim, Kyung Yoon

    2015-01-01

    [Purpose] This study aimed to confirm the effects of kinesio taping (KT) on muscle function and pain due to delayed onset muscle soreness (DOMS) of the biceps brachii. [Subjects and Methods] Thirty-seven subjects with induced DOMS were randomized into either Group I (control, n=19) or Group II (KT, n=18). Outcome measures were recorded before the intervention (application of KT) and at 24, 48, and 72 hours after the intervention. DOMS was induced, and muscle thickness was measured using ultrasonic radiography. Maximal voluntary isometric contraction (%MVIC) was measured via electromyography (EMG). Subjective pain was measured using a visual analogue scale (VAS). [Results] Group I exhibited a positive correlation between muscle thickness and elapsed time from intervention (24, 48, and 72 hours post induction of DOMS); they also showed a significant decrease in MVIC(%). Group II showed significant increases in muscle thickness up to the 48-hour interval post induction of DOMS, along with a significant decrease in MVIC (%). However, in contrast to Group I, Group II did not show a significant difference in muscle thickness or MVIC (%) at the 72-hour interval in comparison with the values prior to DOMS induction. [Conclusion] In adults with DOMS, activation of muscles by applying KT was found to be an effective and faster method of recovering muscle strength than rest alone. PMID:25729190

  20. The effects of kinesio taping on architecture, strength and pain of muscles in delayed onset muscle soreness of biceps brachii.

    PubMed

    Lee, Yong Sin; Bae, Sea Hyun; Hwang, Jin Ah; Kim, Kyung Yoon

    2015-02-01

    [Purpose] This study aimed to confirm the effects of kinesio taping (KT) on muscle function and pain due to delayed onset muscle soreness (DOMS) of the biceps brachii. [Subjects and Methods] Thirty-seven subjects with induced DOMS were randomized into either Group I (control, n=19) or Group II (KT, n=18). Outcome measures were recorded before the intervention (application of KT) and at 24, 48, and 72 hours after the intervention. DOMS was induced, and muscle thickness was measured using ultrasonic radiography. Maximal voluntary isometric contraction (%MVIC) was measured via electromyography (EMG). Subjective pain was measured using a visual analogue scale (VAS). [Results] Group I exhibited a positive correlation between muscle thickness and elapsed time from intervention (24, 48, and 72 hours post induction of DOMS); they also showed a significant decrease in MVIC(%). Group II showed significant increases in muscle thickness up to the 48-hour interval post induction of DOMS, along with a significant decrease in MVIC (%). However, in contrast to Group I, Group II did not show a significant difference in muscle thickness or MVIC (%) at the 72-hour interval in comparison with the values prior to DOMS induction. [Conclusion] In adults with DOMS, activation of muscles by applying KT was found to be an effective and faster method of recovering muscle strength than rest alone. PMID:25729190

  1. Low level laser therapy associated with a strength training program on muscle performance in elderly women: a randomized double blind control study.

    PubMed

    Toma, Renata Luri; Vassão, Patrícia Gabrielli; Assis, Livia; Antunes, Hanna Karen Moreira; Renno, Ana Claudia Muniz

    2016-08-01

    The aging process leads to a gradual loss of muscle mass and muscle performance, leading to a higher functional dependence. Within this context, many studies have demonstrated the benefits of a combination of physical exercise and low level laser therapy (LLLT) as an intervention that enhances muscle performance in young people and athletes. The aim of this study was to evaluate the effects of combination of LLLT and strength training on muscle performance in elderly women. For this, a hundred elderly women were screened, and 48 met all inclusion criteria to participate in this double-blind placebo-controlled trial. Volunteers were divided in three groups: control (CG = 15), strength training associated with placebo LLLT (TG = 17), and strength training associated with active LLLT (808 nm, 100 mW, 7 J) (TLG = 16). The strength training consisted of knee flexion-extension performed with 80 % of 1-repetition maximum (1-RM) during 8 weeks. Several outcomes related to muscle performance were analyzed through the 6-min walk test (6-MWT), isokinetic dynamometry, surface electromyography (SEMG), lactate concentration, and 1-RM. The results revealed that a higher work (p = 0.0162), peak torque (p = 0.0309), and power (p = 0.0223) were observed in TLG compared to CG. Furthermore, both trained groups increased the 1-RM load (TG vs CG: p = 0.0067 and TLG vs CG: p < 0.0001) and decreased the lactate concentration in the third minute after isokinetic protocol (CG vs TLG: p = 0.0289 and CG vs TG: p = 0.0085). No difference in 6-MWT and in fatigue levels were observed among the groups. The present findings suggested that LLLT in combination with strength training was able to improve muscle performance in elderly people. PMID:27250715

  2. Changes of intracellular milieu with fatigue or hypoxia depress contraction of skinned rabbit skeletal and cardiac muscle.

    PubMed Central

    Godt, R E; Nosek, T M

    1989-01-01

    1. Maximal calcium-activated force (Fmax) and calcium sensitivity were markedly decreased in detergent-skinned fibres from skeletal and cardiac muscle by solutions that mimicked the total milieu changes associated with fatigue and hypoxia. Further experiments determined the relative contribution of each of the individual changes in milieu. 2. Both Ca2+ sensitivity and Fmax of skeletal and cardiac fibres were decreased with increased [H+] or inorganic phosphate (Pi). These effects were greater in cardiac muscle. 3. Decreasing MgATP over the range observed with fatigue and hypoxia (6.8-4.7 mM) had no effect on Fmax or Ca2+ sensitivity of either muscle type. 4. Decreasing phosphocreatine (PCr: 15-1 mM) increased Fmax but had little effect on Ca2+ sensitivity in both muscle types. In cardiac fibres, the effect on Fmax could be mimicked by inhibition of endogenous creatine kinase. 5. ADP (0.7 mM) increased Fmax and Ca2+ sensitivity, while AMP (0.06 mM) slightly increased Fmax but had no effect on Ca2+ sensitivity of either skeletal or cardiac fibres. 6. Creatine (25 mM) had no significant effect on either Ca2+ sensitivity or Fmax of skeletal and cardiac muscle fibres. At higher levels (50 mM), however, creatine depressed Fmax and slightly altered Ca2+ sensitivity. 7. Thiophosphorylation of myosin P light chains (phosphorylatable light chains of myosin) in rabbit psoas fibres had no effect on Ca2+ sensitivity, yet slightly but significantly increased Fmax under fatigue conditions. 8. Reducing the affinity for ATP hydrolysis (by adding ADP, AMP and creatine) over the range calculated for fatigue/hypoxia (60-45 kJ/mol) produced the enhancement in Fmax expected from added ADP and AMP in cardiac but not skeletal muscle, indicating that changes in affinity influence Fmax of skeletal muscle. Reducing affinity produced little change in Ca2+ sensitivity of skeletal muscle. In contrast, the change produced in cardiac muscle was greater than that expected from addition of ADP and

  3. Sarcoplasmic reticulum function and muscle contractile character following fatiguing exercise in humans

    PubMed Central

    Hill, Christopher A; Thompson, Martin W; Ruell, Patricia A; Thom, Jeanette M; White, Michael J

    2001-01-01

    This study examined the alterations in calcium release, calcium uptake and calcium ATPase activity of skeletal muscle sarcoplasmic reticulum in response to a bout of intense dynamic knee extensor exercise, and the relationship between these changes and alterations in muscle contractile characteristics in the human quadriceps. In biopsy samples taken from the vastus lateralis, sarcoplasmic reticulum calcium release and calcium uptake were significantly depressed (P < 0.01 and 0.05, respectively) immediately following the exercise with no alteration in the sarcoplasmic reticulum Ca2+-ATPase activity. A 33 % reduction in the maximum voluntary isometric torque was found following the exercise, with reduced torques from electrically evoked isometric contractions at low frequencies of stimulation (10 and 20 Hz) but not at higher frequencies (50 and 100 Hz). The depressed calcium release was correlated (P < 0.05) with a decreased ratio of torques generated at 20:50 Hz, indicating an involvement in low frequency fatigue; however, no correlations between the muscle relaxation times or rates of change of torque and calcium uptake were observed. PMID:11251066

  4. [Use of pulmonary rehabilitation in the treatment of decreased respiratory muscle strength].

    PubMed

    Neumannová, Kateřina

    2015-01-01

    Decreased respiratory muscle strength could lead to other health problems, which can decrease the quality of life of those patients. Ineffective expectoration and dyspnoea during physical activities and during activity of daily living are the most frequent disorders associated with decreased respiratory muscle strength. Multidisciplinary treatment including pulmonary rehabilitation programme is very important for those patients. Ventilatory muscle training (strength and endurance type of training), airway clearance techniques - active (e.g. autogenic drainage, instrumental techniques) and passive (e.g. manual thoracic compression, mechanical insufflator/exsufflator machine) and exercise training are the most frequent used techniques in these patients. Assessment of all respiratory muscles function - especially their respiratory and postural function - is important at the beginning of rehabilitation treatment. PMID:25994909

  5. Effects of Exposure to Normobaric Hyperoxia on the Recovery of Local Muscle Fatigue in the Quadriceps Femoris of Young People

    PubMed Central

    Yokoi, Yuka; Yanagihashi, Ryuya; Morishita, Katsuyuki; Fujiwara, Takayuki; Abe, Koji

    2014-01-01

    [Purpose] Acute development of local muscle fatigue and recovery often become large issues on sports fields. This study aimed to identify the effects of normobaric hyperoxia on the recovery of local muscle fatigue. [Subjects] Eleven healthy males participated in this study, and they all completed two protocols in a random order. [Methods] Subjects performed single-leg isometric knee extension at 70% of their maximum voluntary isometric contraction (MVIC) for as long as possible. Each participant was subsequently treated with one of two recovery conditions: 20.9% O2 or 30.0% O2 for 30 minutes. Afterwards, they performed an identical isometric task to measure the extent of their recovery. The following parameters were used to assess the degrees of muscle fatigue: MVIC, endurance time, surface electromyography (sEMG) power spectra, and changes in hemoglobin concentration using near-infrared spectroscopy (NIRS). [Results] The treatment of 30.0% O2 induced a significant recovery rate in MVIC compared to the 20.9% O2. Additionally, the data revealed a significantly higher concentration of total hemoglobin after the 30.0% O2 treatment than after the 20.9% O2 treatment. [Conclusion] The results of this study suggest that recovery from acute muscle fatigue can be better facilitated under 30.0% normobaric hyperoxia than a normoxic condition. Therefore, for cases requiring quicker full recovery, treatment under 30.0% O2 environment for 30 minutes is recommended. PMID:24707107

  6. Determinants of inspiratory muscle strength in healthy humans.

    PubMed

    Brown, Peter I; Johnson, Michael A; Sharpe, Graham R

    2014-06-01

    We investigated (1) the relationship between the baseline and inspiratory muscle training (IMT) induced increase in maximal inspiratory pressure (P(I,max)) and (2) the relative contributions of the inspiratory chest wall muscles and the diaphragm (P(oes)/P(di)) to P(I,max) prior to and following-IMT. Experiment 1: P(I,max) was assessed during a Müeller manoeuvre before and after 4-wk IMT (n=30). Experiment 2: P(I,max) and the relative contribution of the inspiratory chest wall muscles to the diaphragm (P(oes)/P(di)) were assessed during a Müeller manoeuvre before and after 4-wk IMT (n=20). Experiment 1: P(I,max) increased 19% (P<0.01) post-IMT and was correlated with baseline P(I,max) (r=-0.373, P<0.05). Experiment 2: baseline P(I,max) was correlated with P(oe)/P(di) (r=0.582, P<0.05) and after IMT PI,max increased 22% and Poe/Pdi increased 5% (P<0.05). In conclusion, baseline P(I,max) and the contribution of the chest wall inspiratory muscles relative to the diaphragm affect, in part, baseline and IMT-induced P(I,max). Great care should be taken when designing future IMT studies to ensure parity in the between-subject baseline P(I,max). PMID:24598814

  7. Shank Muscle Strength Training Changes Foot Behaviour during a Sudden Ankle Supination

    PubMed Central

    Hagen, Marco; Lescher, Stephanie; Gerhardt, Andreas; Lahner, Matthias; Felber, Stephan; Hennig, Ewald M.

    2015-01-01

    Background The peroneal muscles are the most effective lateral stabilisers whose tension braces the ankle joint complex against excessive supination. The purpose of this study was to identify the morphological and biomechanical effects of two machine-based shank muscle training methods. Methods Twenty-two healthy male recreationally active sports students performed ten weeks of single-set high resistance strength training with 3 training sessions per week. The subjects conducted subtalar pronator/supinator muscle training (ST) with the right leg by using a custom-made apparatus; the left foot muscles were exercised with machine-based talocrural plantar and dorsiflexor training (TT). Muscle strength (MVIC), muscle volume and foot biomechanics (rearfoot motion, ground reaction forces, muscle reaction times) during a sudden ankle supination were recorded before and after the intervention. Results Compared to TT, ST resulted in significantly higher pronator (14% vs. 8%, P<0.01) and supinator MVIC (25% vs. 12%, P<0.01). During sudden foot inversions, both ST and TT resulted in reduced supination velocity (-12%; P<0.01). The muscle reaction onset time was faster after the training in peroneus longus (PL) (P<0.01). Muscle volume of PL (P<0.01) and TA (P<0.01) increased significantly after both ST and TT. Conclusion After both ST and TT, the ankle joint complex is mechanically more stabilised against sudden supinations due to the muscle volume increase of PL and TA. As the reduced supination velocities indicate, the strength training effects are already present during free-fall. According to a sudden ankle supination in standing position, both machine-based dorsiflexor and pronator strength training is recommended for enhancing the mechanical stability of the ankle. PMID:26110847

  8. Gene transcripts associated with muscle strength: a CHARGE meta-analysis of 7,781 persons.

    PubMed

    Pilling, L C; Joehanes, R; Kacprowski, T; Peters, M; Jansen, R; Karasik, D; Kiel, D P; Harries, L W; Teumer, A; Powell, J; Levy, D; Lin, H; Lunetta, K; Munson, P; Bandinelli, S; Henley, W; Hernandez, D; Singleton, A; Tanaka, T; van Grootheest, G; Hofman, A; Uitterlinden, A G; Biffar, R; Gläser, S; Homuth, G; Malsch, C; Völker, U; Penninx, B; van Meurs, J B J; Ferrucci, L; Kocher, T; Murabito, J; Melzer, D

    2016-01-01

    Lower muscle strength in midlife predicts disability and mortality in later life. Blood-borne factors, including growth differentiation factor 11 (GDF11), have been linked to muscle regeneration in animal models. We aimed to identify gene transcripts associated with muscle strength in adults. Meta-analysis of whole blood gene expression (overall 17,534 unique genes measured by microarray) and hand-grip strength in four independent cohorts (n = 7,781, ages: 20-104 yr, weighted mean = 56), adjusted for age, sex, height, weight, and leukocyte subtypes. Separate analyses were performed in subsets (older/younger than 60, men/women). Expression levels of 221 genes were associated with strength after adjustment for cofactors and for multiple statistical testing, including ALAS2 (rate-limiting enzyme in heme synthesis), PRF1 (perforin, a cytotoxic protein associated with inflammation), IGF1R, and IGF2BP2 (both insulin like growth factor related). We identified statistical enrichment for hemoglobin biosynthesis, innate immune activation, and the stress response. Ten genes were associated only in younger individuals, four in men only and one in women only. For example, PIK3R2 (a negative regulator of PI3K/AKT growth pathway) was negatively associated with muscle strength in younger (<60 yr) individuals but not older (≥ 60 yr). We also show that 115 genes (52%) have not previously been linked to muscle in NCBI PubMed abstracts. This first large-scale transcriptome study of muscle strength in human adults confirmed associations with known pathways and provides new evidence for over half of the genes identified. There may be age- and sex-specific gene expression signatures in blood for muscle strength. PMID:26487704

  9. Gene transcripts associated with muscle strength: a CHARGE meta-analysis of 7,781 persons

    PubMed Central

    Joehanes, R.; Kacprowski, T.; Peters, M.; Jansen, R.; Karasik, D.; Kiel, D. P.; Harries, L. W.; Teumer, A.; Powell, J.; Levy, D.; Lin, H.; Lunetta, K.; Munson, P.; Bandinelli, S.; Henley, W.; Hernandez, D.; Singleton, A.; Tanaka, T.; van Grootheest, G.; Hofman, A.; Uitterlinden, A. G.; Biffar, R.; Gläser, S.; Homuth, G.; Malsch, C.; Völker, U.; Penninx, B.; van Meurs, J. B. J.; Ferrucci, L.; Kocher, T.; Murabito, J.

    2015-01-01

    Lower muscle strength in midlife predicts disability and mortality in later life. Blood-borne factors, including growth differentiation factor 11 (GDF11), have been linked to muscle regeneration in animal models. We aimed to identify gene transcripts associated with muscle strength in adults. Meta-analysis of whole blood gene expression (overall 17,534 unique genes measured by microarray) and hand-grip strength in four independent cohorts (n = 7,781, ages: 20–104 yr, weighted mean = 56), adjusted for age, sex, height, weight, and leukocyte subtypes. Separate analyses were performed in subsets (older/younger than 60, men/women). Expression levels of 221 genes were associated with strength after adjustment for cofactors and for multiple statistical testing, including ALAS2 (rate-limiting enzyme in heme synthesis), PRF1 (perforin, a cytotoxic protein associated with inflammation), IGF1R, and IGF2BP2 (both insulin like growth factor related). We identified statistical enrichment for hemoglobin biosynthesis, innate immune activation, and the stress response. Ten genes were associated only in younger individuals, four in men only and one in women only. For example, PIK3R2 (a negative regulator of PI3K/AKT growth pathway) was negatively associated with muscle strength in younger (<60 yr) individuals but not older (≥60 yr). We also show that 115 genes (52%) have not previously been linked to muscle in NCBI PubMed abstracts. This first large-scale transcriptome study of muscle strength in human adults confirmed associations with known pathways and provides new evidence for over half of the genes identified. There may be age- and sex-specific gene expression signatures in blood for muscle strength. PMID:26487704

  10. Influence of Cyclic Straining on Fatigue, Deformation, and Fracture Behavior of High-Strength Alloy Steel

    NASA Astrophysics Data System (ADS)

    Manigandan, K.; Srivatsan, T. S.; Vasudevan, V. K.; Tammana, D.; Poorganji, B.

    2016-01-01

    In this paper, the results of a study on microstructural influences on mechanical behavior of the high-strength alloy steel Tenax™ 310 are presented and discussed. Under the influence of fully reversed strain cycling, the stress response of this alloy steel revealed softening from the onset of deformation. Cyclic strain resistance exhibited a linear trend for the variation of both elastic strain amplitude with reversals-to-failure, and plastic strain amplitude with reversals-to-failure. Fracture morphology was essentially the same at the macroscopic level over the entire range of cyclic strain amplitudes examined. However, at the fine microscopic level, this high-strength alloy steel revealed fracture to be mixed-mode with features reminiscent of "locally" ductile and brittle mechanisms. The macroscopic mechanisms governing stress response at the fine microscopic level, resultant fatigue life, and final fracture behavior are presented and discussed in light of the mutually interactive influences of intrinsic microstructural effects, deformation characteristics of the microstructural constituents during fully reversed strain cycling, cyclic strain amplitude, and resultant response stress.

  11. Fatigue

    MedlinePlus

    ... Fatigue can be a symptom of anemia, particularly iron-deficiency anemia . Your body needs iron to make hemoglobin, the substance in red blood ... tissues and to your baby. Your need for iron increases during pregnancy because of the needs of ...

  12. A study of microstructure, quasi-static response, fatigue, deformation and fracture behavior of high strength alloy steels

    NASA Astrophysics Data System (ADS)

    Kannan, Manigandan

    The history of steel dates back to the 17th century and has been instrumental in the betterment of every aspect of our lives ever since, from the pin that holds the paper together to the Automobile that takes us to our destination steel touches everyone every day. Path breaking improvements in manufacturing techniques, access to advanced machinery and understanding of factors like heat treatment, corrosion resistance have aided in the advancement in the properties of steel in the last few years. In this dissertation document, the results of a study aimed at the influence of alloy chemistry, processing and influence of the quasi static and fatigue behavior of seven alloy steels is discussed. The microstructure of the as-received steel was examined and characterized for the nature and morphology of the grains and the presence of other intrinsic features in the microstructure. The tensile, cyclic fatigue and bending fatigue tests were done on a fully automated closed-loop servo-hydraulic test machine at room temperature. The failed samples of high strength steels were examined in a scanning electron microscope for understanding the fracture behavior, especially the nature of loading be it quasi static, cyclic fatigue or bending fatigue . The quasi static and cyclic fatigue fracture behavior of the steels examined coupled with various factors contributing to failure are briefly discussed in light of the conjoint and mutually interactive influences of intrinsic microstructural effects, nature of loading, and stress (load)-deformation-microstructural interactions.

  13. Development of Activity-Related Muscle Fatigue during Robot-Mediated Upper Limb Rehabilitation Training in Persons with Multiple Sclerosis: A Pilot Trial

    PubMed Central

    2015-01-01

    Robot-assisted rehabilitation facilitates high-intensity training of the impaired upper limb in neurological rehabilitation. It has been clinically observed that persons with Multiple Sclerosis (MS) have difficulties in sustaining the training intensity during a session due to the development of activity-related muscle fatigue. An experimental observational pilot study was conducted to examine whether or not the muscle fatigue develops in MS patients during one session of robot-assisted training within a virtual learning environment. Six MS patients with upper limb impairment (motricity index ranging from 50 to 91/100) and six healthy persons completed five training bouts of three minutes each performing lifting tasks, while EMG signals of anterior deltoid and lower trapezius muscles were measured and their subjective perceptions on muscle fatigue were registered. Decreased performance and higher subjective fatigue perception were present in the MS group. Increased mean EMG amplitudes and subjective perception levels on muscle fatigue were observed in both groups. Muscle fatigue development during 15′ training has been demonstrated in the arm of MS patients, which influences the sustainability of training intensity in MS patients. To optimize the training performance, adaptivity based on the detection of MS patient's muscle fatigue could be provided by means of training program adjustment. PMID:26090229

  14. Longer Interset Rest Periods Enhance Muscle Strength and Hypertrophy in Resistance-Trained Men.

    PubMed

    Schoenfeld, Brad J; Pope, Zachary K; Benik, Franklin M; Hester, Garrett M; Sellers, John; Nooner, Josh L; Schnaiter, Jessica A; Bond-Williams, Katherine E; Carter, Adrian S; Ross, Corbin L; Just, Brandon L; Henselmans, Menno; Krieger, James W

    2016-07-01

    Schoenfeld, BJ, Pope, ZK, Benik, FM, Hester, GM, Sellers, J, Nooner, JL, Schnaiter, JA, Bond-Williams, KE, Carter, AS, Ross, CL, Just, BL, Henselmans, M, and Krieger, JW. Longer interset rest periods enhance muscle strength and hypertrophy in resistance-trained men. J Strength Cond Res 30(7): 1805-1812, 2016-The purpose of this study was to investigate the effects of short rest intervals normally associated with hypertrophy-type training versus long rest intervals traditionally used in strength-type training on muscular adaptations in a cohort of young, experienced lifters. Twenty-one young resistance-trained men were randomly assigned to either a group that performed a resistance training (RT) program with 1-minute rest intervals (SHORT) or a group that employed 3-minute rest intervals (LONG). All other RT variables were held constant. The study period lasted 8 weeks with subjects performing 3 total body workouts a week comprised 3 sets of 8-12 repetition maximum (RM) of 7 different exercises per session. Testing was performed prestudy and poststudy for muscle strength (1RM bench press and back squat), muscle endurance (50% 1RM bench press to failure), and muscle thickness of the elbow flexors, triceps brachii, and quadriceps femoris by ultrasound imaging. Maximal strength was significantly greater for both 1RM squat and bench press for LONG compared to SHORT. Muscle thickness was significantly greater for LONG compared to SHORT in the anterior thigh, and a trend for greater increases was noted in the triceps brachii (p = 0.06) as well. Both groups saw significant increases in local upper body muscle endurance with no significant differences noted between groups. This study provides evidence that longer rest periods promote greater increases in muscle strength and hypertrophy in young resistance-trained men. PMID:26605807

  15. Effects of strength training on muscle cellular outcomes in prostate cancer patients on androgen deprivation therapy.

    PubMed

    Nilsen, T S; Thorsen, L; Fosså, S D; Wiig, M; Kirkegaard, C; Skovlund, E; Benestad, H B; Raastad, T

    2016-09-01

    Androgen deprivation therapy (ADT) improves life expectancy in prostate cancer (PCa) patients, but is associated with adverse effects on muscle mass. Here, we investigated the effects of strength training during ADT on muscle fiber cross-sectional area (CSA) and regulators of muscle mass. PCa patients on ADT were randomized to 16 weeks of strength training (STG) (n = 12) or a control group (CG; n = 11). Muscle biopsies were obtained from m. vastus lateralis and analyzed by immunohistochemistry and western blot. Muscle fiber CSA increased with strength training (898 μm(2) , P = 0.04), with the only significant increase observed in type II fibers (1076 μm(2) , P = 0.03). There was a trend toward a difference in mean change between groups myonuclei number (0.33 nuclei/fiber, P = 0.06), with the only significant increase observed in type I fibers, which decreased the myonuclear domain size of type I fibers (P = 0.05). Satellite cell numbers and the content of androgen receptor and myostatin remained unchanged. Sixteen weeks of strength training during ADT increased type II fiber CSA and reduced myonuclear domain in type I fibers in PCa patients. The increased number of satellite cells normally seen following strength training was not observed. PMID:26282343

  16. Effects of increasing physical activity on foot structure and ankle muscle strength in adults with obesity

    PubMed Central

    Zhao, Xiaoguang; Tsujimoto, Takehiko; Kim, Bokun; Katayama, Yasutomi; Wakaba, Kyousuke; Wang, Zhennan; Tanaka, Kiyoji

    2016-01-01

    [Purpose] The purpose of this study was to examine the effects of increasing physical activity on foot structure and ankle muscle strength in adults with obesity and to verify whether the rate of change in foot structure is related to that in ankle muscle strength. [Subjects and Methods] Twenty-seven adults with obesity completed a 12-week program in which the intensity of physical activity performed was gradually increased. Physical activity was monitored using a three-axis accelerometer. Foot structure was assessed using a three-dimensional foot scanner, while ankle muscle strength was measured using a dynamometry. [Results] With the increasing physical activity, the participants’ feet became thinner (the rearfoot width, instep height, and girth decreased) and the arch became higher (the arch height index increased) and stiffer (the arch stiffness index increased); the ankle muscle strength also increased after the intervention. Additionally, the changes in the arch height index and arch stiffness index were not associated with changes in ankle muscle strength. [Conclusion] Increasing physical activity may be one possible approach to improve foot structure and function in individuals with obesity.

  17. Impact of backpack type on respiratory muscle strength and lung function in children.

    PubMed

    Vieira, Ana Christina; Ribeiro, Fernando

    2015-01-01

    We examine the influence of backpack type on lung function and respiratory muscle strength in children. Thirty-seven children were assessed for lung function and inspiratory and expiratory muscle strength under four randomly determined conditions: unloaded erect standing and three conditions carrying 15% of the child's body weight. In these three conditions, children carried the weight on a backpack with bilateral shoulder straps carried over both shoulders, on a backpack with bilateral shoulder straps carried over one shoulder and on a backpack with a mono shoulder strap. Significantly lower forced vital capacity, forced expiratory volume in one second and maximal expiratory pressure were observed when children carried a backpack with a mono shoulder strap compared to the unloaded standing position. In conclusion, the restrictive effect and the decrease in expiratory muscle strength were more pronounced for the backpack with a mono shoulder strap, suggesting that a double strap backpack is preferable to a mono shoulder strap backpack. Practitioner summary: There is little known about the effect of schoolbags on respiratory muscle function. We investigated the influence of backpack type on lung function and respiratory muscle strength. A backpack with a mono shoulder strap created a restrictive effect and a decrease in strength, suggesting that a double strap backpack is preferable to a mono shoulder strap backpack. PMID:25584722

  18. Ductile and Compacted Graphite Iron Casting Skin -- Evaluation, Effect on Fatigue Strength and Elimination

    NASA Astrophysics Data System (ADS)

    Boonmee, Sarum

    Compacted graphite (CG) iron features a good combination of tensile strength, impact resistance, thermal conductivity and damping capacity. This combination makes CG iron a material of choice for various applications, especially for the automobile industry. The mechanical properties of CG iron listed in the standards (i.e. ASTM) are for machined specimens. However, since most iron castings retain the original casting surface (a.k.a. casting skin), the actual performance of the part could be significantly different from that of the machined specimens. Recent studies have shown the negative effect of the casting skin, but little quantification of its effect on mechanical properties is available. Further, the understanding of its mechanism of formation is at best incomplete. In this research, the effect of the casting skin on mechanical properties in CG and ductile irons (DI) is explored. The differences in tensile and fatigue properties between as-cast and machined samples were quantified and correlated to the casting skin features. It was found that the presence of the casting skin was accountable for 9% reduction of tensile strength and up to 32% reduction of fatigue strength (for CG iron with 40% nodularity). Several mechanisms of the casting skin formation are proposed in this research. The formation of ferritic and pearlitic rims is explained by decarburizing/carburizing reactions at the mold/metal interface. Mg depletion and solidification kinetics effect were identified as the formation mechanisms of the graphite degradation. A 2-D thermal diffusion model was formulated based on Mg depletion theory. The model can be used to predict the casting skin thickness when Mg depletion is the dominant mechanism. Furthermore, using the asymmetric Fe-Gr phase diagram, some instances of casting skin formation were explained based on solidification kinetics theory. The experimental microstructural evidence and the theoretical progress were conducive to the development of

  19. Internal Oblique and Transversus Abdominis Muscle Fatigue Induced by Slumped Sitting Posture after 1 Hour of Sitting in Office Workers

    PubMed Central

    Waongenngarm, Pooriput; Rajaratnam, Bala S.; Janwantanakul, Prawit

    2015-01-01

    Background Prolonged sitting leads to low back discomfort and lumbopelvic muscle fatigue. This study examined the characteristics of body perceived discomfort and trunk muscle fatigue during 1 hour of sitting in three postures in office workers. Methods Thirty workers sat for 1 hour in one of three sitting postures (i.e., upright, slumped, and forward leaning postures). Body discomfort was assessed using the Body Perceived Discomfort scale at the beginning and after 1 hour of sitting. Electromyographic (EMG) signals were recorded from superficial lumbar multifidus, iliocostalis lumborum pars thoracis, internal oblique (IO)/transversus abdominis (TrA), and rectus abdominis muscles during 1 hour of sitting. The median frequency (MDF) of the EMG power spectrum was calculated. Results Regardless of the sitting posture, the Body Perceived Discomfort scores in the neck, shoulder, upper back, low back, and buttock significantly increased after 1 hour of sitting compared with baseline values (t(9) = −11.97 to −2.69, p < 0.05). The MDF value of the EMG signal of rectus abdominis, iliocostalis lumborum pars thoracis, and multifidus muscles was unchanged over time in all three sitting postures. Only the right and left IO/TrA in the slumped sitting posture was significantly associated with decreased MDF over time (p = 0.019 to 0.041). Conclusion Prolonged sitting led to increased body discomfort in the neck, shoulder, upper back, low back, and buttock. No sign of trunk muscle fatigue was detected over 1 hour of sitting in the upright and forward leaning postures. Prolonged slumped sitting may relate to IO/TrA muscle fatigue, which may compromise the stability of the spine, making it susceptible to injury. PMID:27014491

  20. Evoked EMG versus muscle torque during fatiguing functional electrical stimulation-evoked muscle contractions and short-term recovery in individuals with spinal cord injury.

    PubMed

    Estigoni, Eduardo H; Fornusek, Che; Hamzaid, Nur Azah; Hasnan, Nazirah; Smith, Richard M; Davis, Glen M

    2014-01-01

    This study investigated whether the relationship between muscle torque and m-waves remained constant after short recovery periods, between repeated intervals of isometric muscle contractions induced by functional electrical stimulation (FES). Eight subjects with spinal cord injury (SCI) were recruited for the study. All subjects had their quadriceps muscles group stimulated during three sessions of isometric contractions separated by 5 min of recovery. The evoked-electromyographic (eEMG) signals, as well as the produced torque, were synchronously acquired during the contractions and during short FES bursts applied during the recovery intervals. All analysed m-wave variables changed progressively throughout the three contractions, even though the same muscle torque was generated. The peak to peak amplitude (PtpA), and the m-wave area (Area) were significantly increased, while the time between the stimulus artefact and the positive peak (PosT) were substantially reduced when the muscles became fatigued. In addition, all m-wave variables recovered faster and to a greater extent than did torque after the recovery intervals. We concluded that rapid recovery intervals between FES-evoked exercise sessions can radically interfere in the use of m-waves as a proxy for torque estimation in individuals with SCI. This needs to be further investigated, in addition to seeking a better understanding of the mechanisms of muscle fatigue and recovery. PMID:25479324

  1. Effects of Massage on Muscular Strength and Proprioception After Exercise-Induced Muscle Damage.

    PubMed

    Shin, Mal-Soon; Sung, Yun-Hee

    2015-08-01

    Exercise-induced muscle damage (EIMD), which is commonly associated with eccentric exercise, unaccustomed exercise, and resistance training, may lead to delayed onset muscle soreness, swelling, decreased muscle strength, and range of motion. Many researchers have evaluated various interventions to treat the signs and symptoms of EIMD. However, the effects of massage after EIMD are unclear. Here, we investigated the effect of massage on muscle strength and proprioception after EIMD. All subjects randomly were divided into an EIMD-treated control group (n = 10) and a massage-treated after EIMD experimental group (n = 11). Exercise-induced muscle damage was induced by repeated exercise. Massage treatment was provided by physiotherapist for 15 minutes. It consists of light stroking, milking, friction, and skin rolling. Lactate was evaluated by Lactate Pro analyzer in pre- and postexercise. Surface electromyography (muscle activity) and sonography (muscle thickness) were used to confirm the muscular characteristics. Proprioception was investigated by dual inclinometer. As a result, massage treatment on the gastrocnemius after EIMD increased activation of the medial gastrocnemius during contraction (p ≤ 0.05). In the lateral and medial gastrocnemius, the θs, which is the angle between muscle fibers and superficial aponeurosis, showed a significant change (p ≤ 0.05). However, there are no differences in the θd, which is the angle between muscle fibers and deep aponeurosis. We also found that proprioceptive acuity in the ankle joint was significantly greater in the massage-treated experimental group compared with that in the control group (p ≤ 0.05). These findings suggest that massage of the gastrocnemius after EIMD can improve muscle strength and proprioception by influencing the superficial layer of the gastrocnemius. PMID:25226328

  2. The one repetition maximum test and the sit-to-stand test in the assessment of a specific pulmonary rehabilitation program on peripheral muscle strength in COPD patients

    PubMed Central

    Zanini, Andrea; Aiello, Marina; Cherubino, Francesca; Zampogna, Elisabetta; Azzola, Andrea; Chetta, Alfredo; Spanevello, Antonio

    2015-01-01

    Background Individuals with COPD may present reduced peripheral muscle strength, leading to impaired mobility. Comprehensive pulmonary rehabilitation (PR) should include strength training, in particular to lower limbs. Furthermore, simple tools for the assessment of peripheral muscle performance are required. Objectives To assess the peripheral muscle performance of COPD patients by the sit-to-stand test (STST), as compared to the one-repetition maximum (1-RM), considered as the gold standard for assessing muscle strength in non-laboratory situations, and to evaluate the responsiveness of STST to a PR program. Methods Sixty moderate-to-severe COPD inpatients were randomly included into either the specific strength training group or into the usual PR program group. Patients were assessed on a 30-second STST and 1-minute STST, 1-RM, and 6-minute walking test (6MWT), before and after PR. Bland–Altman plots were used to evaluate the agreement between 1-RM and STST. Results The two groups were not different at baseline. In all patients, 1-RM was significantly related to the 30-second STST (r=0.48, P<0.001) and to 1-minute STST (r=0.36, P=0.005). The 30-second STST was better tolerated in terms of the perceived fatigue (P=0.002) and less time consuming (P<0.001) test. In the specific strength training group significant improvements were observed in the 30-second STST (P<0.001), 1-minute STST (P=0.005), 1-RM (P<0.001), and in the 6MWT (P=0.001). In the usual PR program group, significant improvement was observed in the 30-second STST (P=0.042) and in the 6MWT (P=0.001). Conclusion Our study shows that in stable moderate-to-severe inpatients with COPD, STST is a valid and reliable tool to assess peripheral muscle performance of lower limbs, and is sensitive to a specific PR program. PMID:26648705

  3. Maximum tension and force-velocity properties of fatigued, single Xenopus muscle fibres studied by caffeine and high K+.

    PubMed Central

    Lännergren, J; Westerblad, H

    1989-01-01

    1. The importance of reduced maximum force-generating capacity in the development of skeletal muscle fatigue has been studied using potassium and caffeine contractures as tools. 2. Single, intact fibres isolated from the lumbrical and iliofibularis muscles of Xenopus were fatigued by repeated tetanic stimulations until they produced close to 40% of the original tetanic tension (P0). Using this stimulation scheme three major types of fibres can be distinguished: easily fatigued (type 1), fatigue resistant (type 2), and very fatigue-resistant (type 3) fibres (Westerblad & Lännergren, 1986). 3. When activated by 8-15 mM-caffeine-Ringer solutions fatigued fibres of all three types developed tensions similar to those of controls (81.0 +/- 6.6 vs. 83.9 +/- 4.2% of P0, respectively; means +/- S.D.). 4. Tension output also increased markedly when fatigued fibres were depolarized by 190 mM-K+ solution. The tension produced was in this case fibre type dependent: 71.4 +/- 6.6, 81.3 +/- 2.5 and 95.0 +/- 4.4% of P0 in fibre types 1, 2 and 3, respectively. 5. Force-velocity measurements were performed during caffeine contractures in fatigued iliofibularis fibres (types 1 and 2) to obtain more information about the functional state of cross-bridges. 6. In fatigued type 1 fibres the shortening velocity was reduced to about 25% of that in controls, while it was not significantly depressed in type 2 fibres. 7. It is concluded that cross-bridges of fatigued fibres can produce nearly full tension, but they may work at a much slower rate in this state. 8. Fibre types 1 and 2 mostly display a long-lasting, reversible state of severely depressed tension production during the recovery period, which has been named post-contractile depression, PCD (Westerblad & Lännergren, 1986). Fibres tested in this state generated full caffeine-activated tension and the shortening velocity was not significantly reduced. The tension output during K+ contractures was, however, markedly depressed (12

  4. Muscle strength as a predictor of onset of ADL dependence in people aged 75 years.

    PubMed

    Rantanen, Taina; Avlund, Kirsten; Suominen, Harri; Schroll, Marianne; Frändin, Kerstin; Pertti, Era

    2002-06-01

    The aim of this prospective study over 5 years was to examine maximal isometric strength of multiple muscle groups as a predictor of losing independence in activities of daily living (ADL). The participants were from the Nordic Research on Aging (NORA75). These analyses are restricted to 567 people who at baseline were independent in ADL and participated in strength tests, and who five years later participated in follow-up ADL assessments. Tests on maximal isometric strength of hand grip, elbow flexion, knee extension and trunk flexion and extension were done using adjustable dynamometers. For each muscle group tested, three equal groups were formed for men and women separately based on distributions of results. Those who reported being unable or needing help for eating, dressing, bathing, toileting, walking indoors or transferring from a bed or a chair were rated as ADL dependent. Of the 227 initially ADL independent men, 21 (9.3%) became dependent in ADL. In women, the figures were 30 (8.8%) of 340. Multiple logistic regression models were used to predict the risk of ADL dependence in groups based on strength tertiles. After confirming that the association of muscle strength and incident ADL-dependence was similar in men and women, both genders were included in the same analyses adjusted for body weight and height, gender and research locality. Gender specific cut-offs were used for strength tertiles. All the strength tests predicted ADL dependence, with those being in the lowest tertile having two to three times greater risks than those in the highest tertile of strength. Further adjustments for chronic diseases did not materially change the results. Strength tests could be used to identify people who are still independent in ADL but who are at increased risk of becoming dependent because of poor muscle strength, and who could reduce their risk by strengthening exercises. PMID:12475129

  5. Muscle fatigue as an investigative tool in motor control: A review with new insights on internal models and posture-movement coordination.

    PubMed

    Monjo, Florian; Terrier, Romain; Forestier, Nicolas

    2015-12-01

    Muscle fatigue is a common phenomenon experienced in everyday life which affects both our force capacity and movement production. In this paper, we review works dealing with muscle fatigue and motor control and we attempt to demonstrate how the Central Nervous System deals with this particular state. We especially focus on how internal models--neural substrates which can estimate the current state as well as the future state of the body--face this internal perturbation. Moreover, we show that muscle fatigue is an interesting investigative tool in understanding the mechanisms involved in posture-movement coordination. PMID:26406972

  6. The response to paired motor cortical stimuli is abolished at a spinal level during human muscle fatigue

    PubMed Central

    McNeil, Chris J; Martin, Peter G; Gandevia, Simon C; Taylor, Janet L

    2009-01-01

    During maximal exercise, supraspinal fatigue contributes significantly to the decline in muscle performance but little is known about intracortical inhibition during such contractions. Long-interval inhibition is produced by a conditioning motor cortical stimulus delivered via transcranial magnetic stimulation (TMS) 50–200 ms prior to a second test stimulus. We aimed to delineate changes in this inhibition during a sustained maximal voluntary contraction (MVC). Eight subjects performed a 2 min MVC of elbow flexors. Single test and paired (conditioning–test interval of 100 ms) stimuli were delivered via TMS over the motor cortex every 7–8 s throughout the effort and during intermittent MVCs in the recovery period. To determine the role of spinal mechanisms, the protocol was repeated but the TMS test stimulus was replaced by cervicomedullary stimulation which activates the corticospinal tract. TMS motor evoked potentials (MEPs) and cervicomedullary motor evoked potentials (CMEPs) were recorded from biceps brachii. Unconditioned MEPs increased progressively with fatigue, whereas CMEPs increased initially but returned to the control value in the final 40 s of contraction. In contrast, both conditioned MEPs and CMEPs decreased rapidly with fatigue and were virtually abolished within 30 s. In recovery, unconditioned responses required <30 s but conditioned MEPs and CMEPs required ∼90 s to return to control levels. Thus, long-interval inhibition increased markedly as fatigue progressed. Contrary to expectations, subcortically evoked CMEPs were inhibited as much as MEPs. This new phenomenon was also observed in the first dorsal interosseous muscle. Tested with a high intensity conditioning stimulus during a fatiguing maximal effort, long-interval inhibition of MEPs was increased primarily by spinal rather than motor cortical mechanisms. The spinal mechanisms exposed here may contribute to the development of central fatigue in human muscles. PMID:19805743

  7. The reliability of evaluation of hip muscle strength in rehabilitation robot walking training.

    PubMed

    Huang, Qiuchen; Zhou, Yue; Yu, Lili; Gu, Rui; Cui, Yao; Hu, Chunying

    2015-10-01

    [Purpose] The primary purpose of this study was to evaluate the intraclass correlation coefficient in obtaining the torque of the hip muscle strength during a robot-assisted rehabilitation treatment. [Subjects] Twenty-four patients (15 males, 9 females) with spinal cord injury participated in the study. [Methods] The subjects were asked to walk during robot-assisted rehabilitation, and the torque of the muscle strength which was measured at hip joint flexion angles of -15, -10, -5, 0, 5, 10, 15, 20, 25, and 30 degrees. [Results] The intraclass correlation coefficient of the torque of the hip muscle strength measured by the rehabilitation training robot was excellent. [Conclusion] Our results show that measurement of torque can be used as an objective assessment of treatment with RAT. PMID:26644646

  8. The relationship between cough-specific quality of life and abdominal muscle endurance, fatigue, and depression in patients with COPD

    PubMed Central

    Arikan, Hulya; Savci, Sema; Calik-Kutukcu, Ebru; Vardar-Yagli, Naciye; Saglam, Melda; Inal-Ince, Deniz; Coplu, Lutfi

    2015-01-01

    Background Cough is a prevalent symptom that impacts quality of life in COPD. The aim of this study was to assess the relationship between cough-specific quality of life, abdominal muscle endurance, fatigue, and depression in stable patients with COPD. Methods Twenty-eight patients with COPD (mean age 60.6±8.7 years) referred for pulmonary rehabilitation participated in this cross-sectional study. Sit-ups test was used for assessing abdominal muscle endurance. Leicester Cough Questionnare (LCQ) was used to evaluate symptom-specific quality of life. Fatigue perception was evaluated with Fatigue Impact Scale (FIS). Beck Depression Inventory (BDI) was used for assessing depression level. Results The LCQ total score was significantly associated with number of sit-ups; BDI score; FIS total; physical, cognitive, and psychosocial scores (P<0.05). Scores of the LCQ physical, social, and psychological domains were also significantly related with number of sit-ups, FIS total score, and BDI score (P<0.05). FIS total score and number of sit-ups explained 58% of the variance in LCQ total score (r=0.76, r2=0.577, F(2–20)=12.296, P<0.001). Conclusion Chronic cough may adversely affect performance in daily life due to its negative effect on fatigue and decrease abdominal muscle endurance in patients with COPD. Decreased cough-related quality of life is related with increased level of depression in COPD patients. Effects of increased abdominal muscle endurance and decreased fatigue in COPD patients with chronic cough need further investigation. PMID:26379433

  9. Strength, Fatigue, and Fracture Toughness of Ti-6Al-4V Liner from a Composite Over-Wrapped Pressure Vessel

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.; Lerch, Brad; Thesken, John C.; Sutter, Jim; Russell, Richard

    2008-01-01

    It was demonstrated by way of experiment that Composite Over-wrapped Pressure Vessel (COPV) Ti-6Al-4V liner material can sustain the expected service loads and cycles. The experiments were performed as part of investigations on the residual life of COPV tanks being used in Space Shuttle Orbiters. Measured properties included tensile strength, compressive strength, reversed loading cycles to simulate liner proof strains, and cyclic fatigue loading to demonstrate the ability to sustain 1000 cycles after liner buckling. The liner material came from a salvaged 40 in. Columbia (orbiter 102) tank (SN029), and tensile strength measurements were made on both boss-transition (thick) and membrane regions (thin). The average measured yield strength was 131 ksi in the boss-transition and membrane regions, in good agreement with measurements made on 1970 s vintage forged plate stock. However, Young s modulus was 17.4+/-0.3 Msi, somewhat higher than typical handbook values (approx.16 Msi). The fracture toughness, as estimated from a failed fatigue specimen, was 74 ksi/sq in, in reasonable agreement with standardized measurements made on 1970 s vintage forged plate stock. Low cycle fatigue of a buckled test specimen implied that as-imprinted liners can sustain over 4000 load cycles.

  10. Weight loss may be a better approach for managing musculoskeletal conditions than increasing muscle mass and strength

    PubMed Central

    Kim, Bokun; Tsujimoto, Takehiko; So, Rina; Zhao, Xiaoguang; Suzuki, Shun; Kim, Taeho; Tanaka, Kiyoji

    2015-01-01

    To prevent or remedy musculoskeletal conditions, the relationship between obesity and the characteristics of muscle mass and strength need to be clarified. [Subjects and Methods] A total of 259 Japanese males aged 30–64 years were classified into 4 groups according to the Japanese obesity criteria. Body composition was evaluated, and handgrip strength and knee extensor strength were measured for the upper and lower extremities, respectively. Physical performance was evaluated with a jump test. [Results] Obesity was positively correlated with skeletal muscle mass index, percentage of whole-body fat, and leg muscle strength and negatively correlated with the percentage of muscle mass index, body weight-normalized handgrip strength, and knee extensor strength, and the jump test results. [Conclusion] Weight loss may be a better approach than increasing muscle mass and strength to improve musculoskeletal conditions in obese adult males. PMID:26834353

  11. Time-dependent strength and fatigue resistance of dental direct restorative materials.

    PubMed

    Lohbauer, Ulrich; Frankenberger, Roland; Krämer, Norbert; Petschelt, Anselm

    2003-12-01

    Elastic modulus (EM), initial fracture strength (FS) and flexural fatigue limit (FFL) of dental restorative materials were measured in a simulated oral environment to correlate mechanical response under the influence of water with the chemical nature of the test materials under investigation. One resin composite (RC; Tetric Ceram, Ivoclar-Vivadent Corp., Liechtenstein), an ion-leaching resin composite (ILRC; Ariston pHc, Ivoclar-Vivadent Corp., Liechtenstein) a compomer (CO; Dyract AP, Dentsply Corp., USA) and a glass-ionomer cement (GIC; Ketac Molar, 3MEspe Corp., Germany) were tested. Static EM, FS and dynamic FFL experiments were performed. The FFL was determined under cyclic loading for 10(5) cycles in terms of a staircase approach. The materials were stored for 1, 8, 30, 90 and 180 days in 37 degrees C distilled water, respectively. The RC degraded over time due to water adsorption followed by failure within the resin matrix. The ILRC suffered from a pronounced decrease in FS as well as in FFL due to a constant ion-leaching and macroscopic crack growth. CO failed over time due to resin-filler interface cracking. The GIC exhibited improved mechanical performance over time due to a post-hardening mechanism. The results reveal the necessity for substantial preclinical evaluation of direct restorative materials. The material parameters under investigation are capable of predicting clinical performance over time. PMID:15348497

  12. Is coordination of two-joint leg muscles during load lifting consistent with the strategy of minimum fatigue?

    PubMed

    Prilutsky, B I; Isaka, T; Albrecht, A M; Gregor, R J

    1998-11-01

    The purpose of this study was to examine if strong correlations reported for a back lift task between activity (EMG) of two-joint rectus femoris (RF), hamstrings (HA), and gastrocnemius (GA) and the difference in the joint moments could be predicted by minimizing an objective function of minimum fatigue. Four subjects lifted barbell weights (9 and 18 kg) using a back lift technique at three speeds normal, slow, and fast. Recorded ground reaction forces and coordinates of the leg joints were used to calculate the resultant joint moments. Surface EMG of five muscles crossing the knee joint were also recorded. Forces of nine muscles were calculated using static optimization and a minimum fatigue criterion. Relationships (i) (RF EMG-HA EMG) vs (knee moment hip moment) and (ii) GA EMG vs. (ankle moment knee moment) were closely related (coefficients of determination were typically 0.9 and higher). Qualitatively similar relationships were predicted by minimizing fatigue. Gastrocnemius and hamstrings had the agonistic action at both joints they cross during load lifting, and their activation and predicted forces increased with increasing flexion knee moments and extension ankle and hip moments. The rectus femoris typically had the antagonistic action at the knee and hip, and its activation and predicted force were low. Patterns of predicted muscle forces were qualitatively similar to the corresponding EMG envelopes (except in phases of low joint moments where accuracy of determining joint moments was presumably poor). It was suggested that muscle coordination in load lifting is consistent with the strategy of minimum muscle fatigue. PMID:9880059

  13. Small Crack Growth and Fatigue Life Predictions for High-Strength Aluminium Alloys. Part 1; Experimental and Fracture Mechanics Analysis

    NASA Technical Reports Server (NTRS)

    Wu, X. R.; Newman, J. C.; Zhao, W.; Swain, M. H.; Ding, C. F.; Phillips, E. P.

    1998-01-01

    The small crack effect was investigated in two high-strength aluminium alloys: 7075-T6 bare and LC9cs clad alloy. Both experimental and analytical investigations were conducted to study crack initiation and growth of small cracks. In the experimental program, fatigue tests, small crack and large crack tests A,ere conducted under constant amplitude and Mini-TWIST spectrum loading conditions. A pronounced small crack effect was observed in both materials, especially for the negative stress ratios. For all loading conditions, most of the fatigue life of the SENT specimens was shown to be crack propagation from initial material defects or from the cladding layer. In the analysis program, three-dimensional finite element and A weight function methods were used to determine stress intensity factors and to develop SIF equations for surface and corner cracks at the notch in the SENT specimens. A plastisity-induced crack-closure model was used to correlate small and large crack data, and to make fatigue life predictions, Predicted crack-growth rates and fatigue lives agreed well with experiments. A total fatigue life prediction method for the aluminum alloys was developed and demonstrated using the crack-closure model.

  14. High-temperature reverse-bend fatigue strength of Inconel Alloy 625

    SciTech Connect

    Purohit, A.; Greenfield, I.G.; Park, K.B.

    1983-06-01

    Inconel 625 has been selected as the clad material for Upgraded Transient Reactor Test Facility (TREAT Upgrade or TU) fuel assemblies. The range of temperatures investigated is 900 to 1100/sup 0/C. A reverse-bend fatigue test program was selected as the most-effective method of determining the fatigue characteristics of Inconel alloy 625 sheet metal. The paper describes the reverse bend fatigue experiments, the results obtained, and the analysis of data.

  15. Relationships of ultrasound measures of intrinsic foot muscle cross-sectional area and muscle volume with maximum toe flexor muscle strength and physical performance in young adults

    PubMed Central

    Abe, Takashi; Tayashiki, Kota; Nakatani, Miyuki; Watanabe, Hironori

    2016-01-01

    [Purpose] To investigate the relationships between toe flexor muscle strength with (TFS-5-toes) and without (TFS-4-toes) the contribution of the great toe, anatomical and physiological muscle cross-sectional areas (CSA) of intrinsic toe flexor muscle and physical performance were measured. [Subjects] Seventeen men (82% sports-active) and 17 women (47% sports-active), aged 20 to 35 years, volunteered. [Methods] Anatomical CSA was measured in two intrinsic toe flexor muscles (flexor digitorum brevis [FDB] and abductor hallucis) by ultrasound. Muscle volume and muscle length of the FDB were also estimated, and physiological CSA was calculated. [Results] Both TFS-5-toes and TFS-4-toes correlated positively with walking speed in men (r=0.584 and r=0.553, respectively) and women (r=0.748 and r=0.533, respectively). Physiological CSA of the FDB was significantly correlated with TFS-5-toes (r=0.748) and TFS-4-toes (r=0.573) in women. In men, physiological CSA of the FDB correlated positively with TFS-4-toes (r=0.536), but not with TFS-5-toes (r=0.333). [Conclusion] Our results indicate that physiological CSA of the FDB is moderately associated with TFS-4-toes while toe flexor strength correlates with walking performance. PMID:26957721

  16. Effect of Expiratory Resistive Loading in Expiratory Muscle Strength Training on Orbicularis Oris Muscle Activity

    PubMed Central

    Yanagisawa, Yukio; Matsuo, Yoshimi; Shuntoh, Hisato; Horiuchi, Noriaki

    2014-01-01

    [Purpose] The purpose of this study was to elucidate the effect of expiratory resistive loading on orbicularis oris muscle activity. [Subjects] Subjects were 23 healthy individuals (11 males, mean age 25.5±4.3 years; 12 females, mean age 25.0±3.0 years). [Methods] Surface electromyography was performed to measure the activity of the orbicularis oris muscle during maximum lip closure and resistive loading at different expiratory pressures. Measurement was performed at 10%, 30%, 50%, and 100% of maximum expiratory pressure (MEP) for all subjects. The t-test was used to compare muscle activity between maximum lip closure and 100% MEP, and analysis of variance followed by multiple comparisons was used to compare the muscle activities observed at different expiratory pressures. [Results] No significant difference in muscle activity was observed between maximum lip closure and 100% MEP. Analysis of variance with multiple comparisons revealed significant differences among the different expiratory pressures. [Conclusion] Orbicularis oris muscle activity increased with increasing expiratory resistive loading. PMID:24648644

  17. An active control logic to improve the fatigue strength of smart flexible structures

    NASA Astrophysics Data System (ADS)

    Ambrosio, Pasquale; Braghin, Francesco; Resta, Ferruccio; Ripamonti, Francesco

    2013-04-01

    In general active vibration control intrinsically implies a fatigue damage reduction. Anyway, this assumption is not always verified. In these cases it is possible to deeper investigate the fatigue phenomena on smart flexible structures and their reduction from a control point of view. In this article, to identify the problem main parameters, a simplified interpretation of fatigue damage is given using the frequency analysis framework. Then, the active control logic is defined as an optimization problem with a quadratic functional taking into account the previously cited parameters. Finally, because of non-linearity of fatigue phenomenon, an adaptive approach is applied and a numerical/experimental validation is carried out.

  18. Motor effort training with low exercise intensity improves muscle strength and descending command in aging.

    PubMed

    Jiang, Changhao; Ranganathan, Vinoth K; Zhang, Junmei; Siemionow, Vlodek; Yue, Guang H

    2016-06-01

    This study explored the effect of high mental effort training (MET) and conventional strength training (CST) on increasing voluntary muscle strength and brain signal associated with producing maximal muscle force in healthy aging. Twenty-seven older adults (age: 75 ± 7.9 yr, 8 women) were assigned into 1 of 3 groups: MET group-trained with low-intensity (30% maximal voluntary contraction [MVC]) physical exercise combined with MET, CST group-trained with high-intensity muscle contractions, or control (CTRL) group-no training of any kind. MET and CST lasted for 12 weeks (5 sessions/week). The participants' elbow flexion strength of the right arm, electromyography (EMG), and motor activity-related cortical potential (MRCP) directly related to the strength production were measured before and after training. The CST group had the highest strength gain (17.6%, P <0.001), the MET group also had significant strength gain (13.8%, P <0.001), which was not statistically different from that of the CST group even though the exercise intensity for the MET group was only at 30% MVC level. The CTRL group did not have significant strength changes. Surprisingly, only the MET group demonstrated a significant augmentation in the MRCP (29.3%, P <0.001); the MRCP increase in CST group was at boarder-line significance level (12.11%, P = 0.061) and that for CTRL group was only 4.9% (P = 0.539). These results suggest that high mental effort training combined with low-intensity physical exercise is an effective method for voluntary muscle strengthening and this approach is especially beneficial for those who are physically weak and have difficulty undergoing conventional strength training. PMID:27310942

  19. Motor effort training with low exercise intensity improves muscle strength and descending command in aging

    PubMed Central

    Jiang, Changhao; Ranganathan, Vinoth K.; Zhang, Junmei; Siemionow, Vlodek; Yue, Guang H.

    2016-01-01

    Abstract This study explored the effect of high mental effort training (MET) and conventional strength training (CST) on increasing voluntary muscle strength and brain signal associated with producing maximal muscle force in healthy aging. Twenty-seven older adults (age: 75 ± 7.9 yr, 8 women) were assigned into 1 of 3 groups: MET group—trained with low-intensity (30% maximal voluntary contraction [MVC]) physical exercise combined with MET, CST group—trained with high-intensity muscle contractions, or control (CTRL) group—no training of any kind. MET and CST lasted for 12 weeks (5 sessions/week). The participants’ elbow flexion strength of the right arm, electromyography (EMG), and motor activity-related cortical potential (MRCP) directly related to the strength production were measured before and after training. The CST group had the highest strength gain (17.6%, P <0.001), the MET group also had significant strength gain (13.8%, P <0.001), which was not statistically different from that of the CST group even though the exercise intensity for the MET group was only at 30% MVC level. The CTRL group did not have significant strength changes. Surprisingly, only the MET group demonstrated a significant augmentation in the MRCP (29.3%, P <0.001); the MRCP increase in CST group was at boarder-line significance level (12.11%, P = 0.061) and that for CTRL group was only 4.9% (P = 0.539). These results suggest that high mental effort training combined with low-intensity physical exercise is an effective method for voluntary muscle strengthening and this approach is especially beneficial for those who are physically weak and have difficulty undergoing conventional strength training. PMID:27310942

  20. Comparison of pelvic floor muscle strength evaluations in nulliparous and primiparous women: a prospective study

    PubMed Central

    Gameiro, Mônica Orsi; Sousa, Vanessa Oliveira; Gameiro, Luiz Felipe; Muchailh, Rosana Carneiro; Padovani, Carlos Roberto; Amaro, João Luiz

    2011-01-01

    OBJECTIVE: This study aimed to compare the pelvic floor muscle strength of nulliparous and primiparous women. METHODS: A total of 100 women were prospectively distributed into two groups: Group 1 (G1) (n = 50) included healthy nulliparous women, and Group 2 (G2) (n = 50) included healthy primiparous women. Pelvic floor muscle strength was subjectively evaluated using transvaginal digital palpation. Pelvic floor muscle strength was objectively assessed using a portable perineometer. All of the parameters were evaluated simultaneously in G1 and were evaluated in G2 during the 20th and 36th weeks of pregnancy and 45 days after delivery. RESULTS: In G2, 14 women were excluded because they left the study before the follow-up evaluation. The median age was 23 years in G1 and 22 years in G2; there was no significant difference between the groups. The average body mass index was 21.7 kg/m2 in G1 and 25.0 kg/m2 in G2; there was a significant difference between the groups (p = 0.0004). In G2, transvaginal digital palpation evaluation showed significant impairments of pelvic floor muscle strength at the 36th week of pregnancy (p = 0.0006) and 45 days after vaginal delivery (p = 0.0001) compared to G1. Objective evaluations of pelvic floor muscle strength in G2 revealed a significant decrease 45 days after vaginal delivery compared to nulliparous patients. CONCLUSION: Pregnancy and vaginal delivery may cause weakness of the pelvic floor muscles. PMID:21915489

  1. Upper Extremity Muscle Volumes and Functional Strength After Resistance Training in Older Adults

    PubMed Central

    Daly, Melissa; Vidt, Meghan E.; Eggebeen, Joel D.; Simpson, W. Greg; Miller, Michael E.; Marsh, Anthony P.; Saul, Katherine R.

    2014-01-01

    Aging leads to a decline in strength and an associated loss of independence. The authors examined changes in muscle volume, maximum isometric joint moment, functional strength, and 1-repetition maximum (1RM) after resistance training (RT) in the upper extremity of older adults. They evaluated isometric joint moment and muscle volume as predictors of functional strength. Sixteen healthy older adults (average age 75 ± 4.3 yr) were randomized to a 6-wk upper extremity RT program or control group. The RT group increased 1RM significantly (p < .01 for all exercises). Compared with controls, randomization to RT led to greater functional pulling strength (p = .003), isometric shoulder-adduction moment (p = .041), elbow-flexor volume (p = .017), and shoulder-adductor volume (p = .009). Shoulder-muscle volumes and isometric moments were good predictors of functional strength. The authors conclude that shoulder strength is an important factor for performing functional reaching and pulling tasks and a key target for upper extremity RT interventions. PMID:22952203

  2. MMP(-2) expression in skeletal muscle after strength training.

    PubMed

    Deus, A P L; Bassi, D; Simões, R P; Oliveira, C R; Baldissera, V; Marqueti, R de Cássia; Araujo, H S S; Arena, R; Borghi-Silva, A

    2012-02-01

    The aim of this study was to assess the effects of resistance training on ladders (RTL) on MMP(-2) expression and blood lactate concentration [La-]. 30 male (3 months of age), albino rats were divided into 3 groups: sedentary control (SC, n=10), low resistance exercise training (Low-IntRT, n=10) and high-intensive exercise training (High-IntRT, n=10). Animals of High-IntRT were submitted to a progressively increasing overload in relation to body weight until exhaustion, while the Low-IntRT group performed the same exercise regimen with no external load. The program had a frequency of 3 times per week over 8 weeks. MMP(-2) expression of tibialis anterior muscle and [La-] were measured. While there was a significant increase of MMP(-2) (pro-form) in both groups, only High-IntRT significantly increased MMP(-2) in active-form (p<0.05). Both trained groups exhibited an increase in [La-] when compared to controls, however, the increase in [La-] was significantly higher in the High-IntRT compared to Low-IntRT (p<0.05). Strong correlation was found between MMP(-2) (active form) and [La-] in High-IntRT (r=0.91). RTL in using low and high-intensity exercise can serve as a model to demonstrate different responses of MMP(-2) expression in an animal model. It appears active form expression of MMP(-2) is modulated by exercise intensity. PMID:22095325

  3. Physical characteristics as predictors of quadriceps muscle isometric strength: a pilot study.

    PubMed

    Hamzat, T K

    2001-09-01

    This one-group experimental study was carried out to investigate the relationship between isometric strength of quadriceps femoris muscle group and physical characteristics of subjects namely: age; weight; and height. Prediction equations were also derived for quadriceps isometric strength from these physical characteristics. Fifty volunteer, right-legged healthy normal male subjects participated in the study. They were aged between 19 and 27 years. The subjects had no previous history of neuromuscular and skeletal injuries to the lower limbs. Their ages, height and weight were measured in years, centimeters and kilograms, respectively. Quadriceps isometric strength was measured using an adapted cable tensiometer (ACT) and recorded in kilogramforce (kgf). Pearson's product correlation co-efficient (r) was used to study the relationship between quadriceps strength and each of age, height and weight. Linear and multiple regression analyses were also carried out. The result showed a high and positive Pearson's moment correlation coefficient (r) between quadriceps isometric strength and each of weight and height. A positive but low correlation (r) was also found between age and quadriceps isometric strength. Prediction equations were also derived from the linear and regression analyses. The study concluded that there was linear relationship between the physical characteristics and quadriceps isometric strength. It was recommended that the prediction equation be employed to estimate quadriceps strength while setting muscle strengthening goals in the clinics during medical rehabilitation for patients within the age range used in this study. PMID:14510124

  4. Age-Related Changes in Dynamic Postural Control and Attentional Demands are Minimally Affected by Local Muscle Fatigue

    PubMed Central

    Remaud, Anthony; Thuong-Cong, Cécile; Bilodeau, Martin

    2016-01-01

    Normal aging results in alterations in the visual, vestibular and somtaosensory systems, which in turn modify the control of balance. Muscle fatigue may exacerbate these age-related changes in sensory and motor functions, and also increase the attentional demands associated with dynamic postural control. The purpose of this study was to investigate the effect of aging on dynamic postural control and posture-related attentional demands before and after a plantar flexor fatigue protocol. Participants (young adults: n = 15; healthy seniors: n = 13) performed a dynamic postural task along the antero-posterior (AP) and the medio-lateral (ML) axes, with and without the addition of a simple reaction time (RT) task. The dynamic postural task consisted in following a moving circle on a computer screen with the representation of the center of pressure (COP). This protocol was repeated before and after a fatigue task where ankle plantar flexor muscles were targeted. The mean COP-target distance and the mean COP velocity were calculated for each trial. Cross-correlation analyses between the COP and target displacements were also performed. RTs were recorded during dual-task trials. Results showed that while young adults adopted an anticipatory control mode to move their COP as close as possible to the target center, seniors adopted a reactive control mode, lagging behind the target center. This resulted in longer COP-target distance and higher COP velocity in the latter group. Concurrently, RT increased more in seniors when switching from static stance to dynamic postural conditions, suggesting potential alterations in the central nervous system (CNS) functions. Finally, plantar flexor muscle fatigue and dual-tasking had only minor effects on dynamic postural control of both young adults and seniors. Future studies should investigate why the fatigue-induced changes in quiet standing postural control do not seem to transfer to dynamic balance tasks. PMID:26834626

  5. Effects of muscle strength asymmetry between left and right on isokinetic strength of the knee and ankle joints depending on athletic performance level

    PubMed Central

    Jeon, Kyoungkyu; Chun, Sungyung; Seo, Byoungdo

    2016-01-01

    [Purpose] The aim of this study was to collect basic data on the effect of asymmetry on the muscle strength of the left and right knee and ankle joints of soccer players at varying athletic performance levels, to guide the development of improved exercise programs. [Subjects and Methods] Forty-nine soccer players at three athletic performance levels participated: 15 professional, 16 amateur, and 18 college. Knee extensor and flexor strength were measured at 60°/sec and 180°/sec, and ankle plantar flexor and dorsiflexor strength were measured at 30°/sec and at 120°/sec. Variables were analyzed by one-way ANOVA. [Results] College soccer players showed greater muscle strength at 60°/sec and 180°/sec in the knee extension muscles of both the right and the left sides, lower muscle strength at 30°/sec and 120°/sec in the dorsiflexor of the right ankle, and similar levels of asymmetry between left and right. The maximum muscle strength on the same side significantly differed in the right ankle joint, with asymmetry between left and right at 30°/sec and 120°/sec. [Conclusion] These findings suggest that muscle strength asymmetry in the ankle joint may lead to counterbalancing muscle strengthening of the knee joint to maintain the center of body mass. PMID:27190469

  6. Effects of muscle strength asymmetry between left and right on isokinetic strength of the knee and ankle joints depending on athletic performance level.

    PubMed

    Jeon, Kyoungkyu; Chun, Sungyung; Seo, Byoungdo

    2016-04-01

    [Purpose] The aim of this study was to collect basic data on the effect of asymmetry on the muscle strength of the left and right knee and ankle joints of soccer players at varying athletic performance levels, to guide the development of improved exercise programs. [Subjects and Methods] Forty-nine soccer players at three athletic performance levels participated: 15 professional, 16 amateur, and 18 college. Knee extensor and flexor strength were measured at 60°/sec and 180°/sec, and ankle plantar flexor and dorsiflexor strength were measured at 30°/sec and at 120°/sec. Variables were analyzed by one-way ANOVA. [Results] College soccer players showed greater muscle strength at 60°/sec and 180°/sec in the knee extension muscles of both the right and the left sides, lower muscle strength at 30°/sec and 120°/sec in the dorsiflexor of the right ankle, and similar levels of asymmetry between left and right. The maximum muscle strength on the same side significantly differed in the right ankle joint, with asymmetry between left and right at 30°/sec and 120°/sec. [Conclusion] These findings suggest that muscle strength asymmetry in the ankle joint may lead to counterbalancing muscle strengthening of the knee joint to maintain the center of body mass. PMID:27190469

  7. In vivo assessment of contractile strength distinguishes differential gene function in skeletal muscle of zebrafish larvae.

    PubMed

    Martin, Brit L; Gallagher, Thomas L; Rastogi, Neha; Davis, Jonathan P; Beattie, Christine E; Amacher, Sharon L; Janssen, Paul M L

    2015-10-01

    The accessible genetics and extensive skeletal musculature of the zebrafish make it a versatile and increasingly used model for studying muscle contraction. We here describe the development of an in vivo assay for measuring the contractile force of intact zebrafish at the larval stage. In addition, as proof of applicability, we have used this assay to quantify contractile strength of zebrafish larvae in a morphant model of deranged rbfox function. Average maximum tetanic (180 Hz) whole body forces produced by wild-type larvae at 2, 3, 4, and 5 days postfertilization amounted to 3.0, 7.2, 9.1, and 10.8 mN, respectively. To compare at potentially different stages of muscle development, we developed an immunohistological assay for empirically determining the cross-sectional area of larval trunk skeletal muscle to quantify muscle-specific force per cross-sectional area. At 4-5 days postfertilization, specific force amounts to ∼ 300 mN/mm(2), which is similar to fully developed adult mammalian skeletal muscle. We used these assays to measure contractile strength in zebrafish singly or doubly deficient for two rbfox paralogs, rbfox1l and rbfox2, which encode RNA-binding factors shown previously to modulate muscle function and muscle-specific splicing. We found rbfox2 morphants produce maximal tetanic forces similar to wild-type larvae, whereas rbfox1l morphants demonstrate significantly impaired function. rbfox1l/rbfox2 morphants are paralyzed, and their lack of contractile force production in our assay suggests that paralysis is a muscle-autonomous defect. These quantitative functional results allow measurement of muscle-specific phenotypes independent of neural input. PMID:26251513

  8. Effects of 5 weeks of lower limb suspension on muscle size and strength

    NASA Technical Reports Server (NTRS)

    Tesch, P. A.; Ploutz, L. L.; Dudley, G. A.

    1994-01-01

    Lack of weight-bearing, as occurs in space, appears to be associated with reductions in strength and mass of skeletal muscle. Very limited data, however, is at hand describing changes in skeletal muscle size and function following manned space missions. Our current knowledge therefore is mainly based on studies of space flown rats. It is obvious though that this information, only in part can be extrapolated to humans. A few bed rest studies have demonstrated that decreases in strength and muscle size are substantial. At this time, however, the magnitude or time course of such changes either in response to space flight or simulations of microgravity have not been defined. In the last few years we have employed a human model to simulate unloading of lower limb skeletal muscles that occurs in microgravity. This model was essentially adopted from the rat hindlimb suspension technique. The purpose of this study was to assess the magnitude of decreases in muscle strength and size as a result of five weeks of unilateral lower limb suspension.

  9. Abnormalities of AMPK Activation and Glucose Uptake in Cultured Skeletal Muscle Cells from Individuals with Chronic Fatigue Syndrome

    PubMed Central

    Brown, Audrey E.; Jones, David E.; Walker, Mark; Newton, Julia L.

    2015-01-01

    Background Post exertional muscle fatigue is a key feature in Chronic Fatigue Syndrome (CFS). Abnormalities of skeletal muscle function have been identified in some but not all patients with CFS. To try to limit potential confounders that might contribute to this clinical heterogeneity, we developed a novel in vitro system that allows comparison of AMP kinase (AMPK) activation and metabolic responses to exercise in cultured skeletal muscle cells from CFS patients and control subjects. Methods Skeletal muscle cell cultures were established from 10 subjects with CFS and 7 age-matched controls, subjected to electrical pulse stimulation (EPS) for up to 24h and examined for changes associated with exercise. Results In the basal state, CFS cultures showed increased myogenin expression but decreased IL6 secretion during differentiation compared with control cultures. Control cultures subjected to 16h EPS showed a significant increase in both AMPK phosphorylation and glucose uptake compared with unstimulated cells. In contrast, CFS cultures showed no increase in AMPK phosphorylation or glucose uptake after 16h EPS. However, glucose uptake remained responsive to insulin in the CFS cells pointing to an exercise-related defect. IL6 secretion in response to EPS was significantly reduced in CFS compared with control cultures at all time points measured. Conclusion EPS is an effective model for eliciting muscle contraction and the metabolic changes associated with exercise in cultured skeletal muscle cells. We found four main differences in cultured skeletal muscle cells from subjects with CFS; increased myogenin expression in the basal state, impaired activation of AMPK, impaired stimulation of glucose uptake and diminished release of IL6. The retention of these differences in cultured muscle cells from CFS subjects points to a genetic/epigenetic mechanism, and provides a system to identify novel therapeutic targets. PMID:25836975

  10. AISI/DOE Technology Roadmap Program: Characterization of Fatigue and Crash Performance of New Generation High Strength Steels for Automotive Applications

    SciTech Connect

    Brenda Yan; Dennis Urban

    2003-04-21

    A 2-year project (2001-2002) to generate fatigue and high strain data for a new generation of high strength steels (HSS) has been completed in December 2002. The project tested eleven steel grades, including Dual Phase (DP) steels, Transformation-Induced Plasticity (TRIP) steels, Bake Hardenable (BH) steels, and conventional High Strength Low Alloy (HSLA) steels. All of these steels are of great interest in automotive industry due to the potential benefit in weight reduction, improved fuel economy, enhanced crash energy management and total system cost savings. Fatigue behavior includes strain controlled fatigue data notch sensitivity for high strength steels. High strain rate behavior includes stress-strain data for strain rates from 0.001/s to 1000/s, which are considered the important strain rate ranges for crash event. The steels were tested in two phases, seven were tested in Phase 1 and the remaining steels were tested in Phase. In a addition to the fatigue data and high st rain rate data generated for the steels studied in the project, analyses of the testing results revealed that Advanced High Strength Steels (AHSS) exhibit significantly higher fatigue strength and crash energy absorption capability than conventional HSS. TRIP steels exhibit exceptionally better fatigue strength than steels of similar tensile strength but different microstructure, for conditions both with or without notches present

  11. Relationships between Respiratory Muscle Strength and Daily Living Function in Children with Cerebral Palsy

    ERIC Educational Resources Information Center

    Wang, Hui-Yi; Chen, Chien-Chih; Hsiao, Shih-Fen

    2012-01-01

    Cerebral palsy (CP) is a common childhood disorder characterized by motor disability. Children with CP are at risk of developing significant respiratory problems associated with insufficient respiratory muscle strength. It is crucial to identify important factors which are associated with the limitations in daily living function in such children.…

  12. Angiotensin-II blockage, muscle strength, and exercise capacity in physically independent older adults

    PubMed Central

    Coelho, Vinícius A.; Probst, Vanessa S.; Nogari, Bruna M.; Teixeira, Denilson C.; Felcar, Josiane M.; Santos, Denis C.; Gomes, Marcus Vinícius M.; Andraus, Rodrigo A. C.; Fernandes, Karen B. P.

    2016-01-01

    [Purpose] This study aimed to assess the exercise capacity and muscle strength in elderly people using drugs for angiotensin-II blockage. [Subjects and Methods] Four hundred and seven older adults were recruited for this study. Data about comorbidities and medication use were recorded and the individuals were divided into three groups: control group- elderly people with normal exercise capacity (n=235); angiotensin-converting enzyme inhibitor group − individuals using angiotensin-converting enzyme inhibitors (n=140); and angiotensin-II receptor blocker group- patients using angiotensin-II receptor blockers (n= 32). Exercise capacity was evaluated by a 6-minute walking test and muscle strength was measured using a handgrip dynamometer. [Results] Patients from the angiotensin-converting enzyme inhibitor group (mean: 99 ± 12%) and the angiotensin-II receptor blocker group (mean: 101 ± 14%) showed higher predicted values in the 6-minute walking test than the control group patients (mean: 96 ± 10%). Patients from the angiotensin-converting enzyme inhibitor group (mean: 105 ± 19%) and the angiotensin-II receptor blocker group (mean: 105.1 ± 18.73%) showed higher predicted values of muscle strength than control group patients (mean: 98.15 ± 18.77%). [Conclusion] Older adults using angiotensin-converting enzyme inhibitors or angiotensin-II receptor blockers have better functional exercise capacity and muscle strength. PMID:27065543

  13. Influence of Body Composition on Lung Function and Respiratory Muscle Strength in Children With Obesity

    PubMed Central

    Costa Junior, Dirceu; Peixoto-Souza, Fabiana S.; Araujo, Poliane N.; Barbalho-Moulin, Marcela C.; Alves, Viviane C.; Gomes, Evelim L. F. D.; Costa, Dirceu

    2016-01-01

    Background Obesity affects lung function and respiratory muscle strength. The aim of the present study was to assess lung function and respiratory muscle strength in children with obesity and determine the influence of body composition on these variables. Methods A cross-sectional study was conducted involving 75 children (40 with obesity and 35 within the ideal weight range) aged 6 - 10 years. Body mass index, z score, waist circumference, body composition (tetrapolar bioimpedance), respiratory muscle strength and lung function (spirometry) were evaluated. Results Children with obesity exhibited larger quantities of both lean and fat mass in comparison to those in the ideal weight range. No significant differences were found between groups regarding the respective reference values for respiratory muscle strength. Male children with obesity demonstrated significantly lower lung function values (forced expiratory volume in the first second % (FEV1%) and FEV1/forced vital capacity % (FVC%) : 93.76 ± 9.78 and 92.29 ± 3.8, respectively) in comparison to males in the ideal weight range (99.87 ± 9.72 and 96.31 ± 4.82, respectively). The regression models demonstrated that the spirometric variables were influenced by all body composition variables. Conclusion Children with obesity demonstrated a reduction in lung volume and capacity. Thus, anthropometric and body composition characteristics may be predictive factors for altered lung function. PMID:26767078

  14. The Effects of a 10-Kilometer Run on Muscle Strength and Power.

    ERIC Educational Resources Information Center

    Gomez, Ana L.; Radzwich, Robert J.; Denegar, Craig R.; Volek, Jeff S.; Rubin, Martyn R.; Bush, Jill A.; Doan, Brandon K.; Wickham, Robbin B.; Mazzetti, Scott A.; Newton, Robert U.; French, Duncan N.; Hakkinen, Keijo; Ratamess, Nicholas A.; Kraemer, William J.

    2002-01-01

    Investigated recovery of maximal force and power following a 10-km race. Data collected on 10 healthy male distance runners pre-race, immediately post-race, and 48 hours later indicated that strength and power capabilities of these 10-km runners were for the most part restored 48 hours after the race. Only the hamstring muscle group was not fully…

  15. Reliability of Maximal Voluntary Muscle Strength and Power Testing in Older Men

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background Maximal voluntary muscle strength (MVMS) and leg power are important measures of physical function in older adults. We hypothesized that performing these measures twice within 7-10 days would demonstrate a >5% increase due to learning and familiarization of the testing procedures. Methods...

  16. Wii balance board exercise improves balance and lower limb muscle strength of overweight young adults

    PubMed Central

    Siriphorn, Akkradate; Chamonchant, Dannaovarat

    2015-01-01

    [Purpose] The potential health benefits of the Nintendo Wii balance board exercise have been widely investigated. However, no study has been conducted to examine the benefits of Wii exercise for overweight young adults. The aim of this study was to investigate the effect of exercise performed on a Nintendo Wii balance board on the balance and lower limb muscle strength in overweight young adults. [Subjects and Methods] Within-subject repeated measures analysis was used. Sixteen young adults (aged 21.87±1.13 years, body mass index 24.15 ± 0.50 kg/m2) were recruited. All subjects performed an exercise program on a Wii balance board for 8 weeks (30 min/session, twice a week for 8 weeks). A NeuroCom Balance Master and a hand-held dynamometer were used to measure balance performance and lower limb muscle strength. [Results] According to the comparison of pre- and post-intervention measurements, the Wii balance board exercise program significantly improved the limit of stability parameters. There was also a significant increase in strength of four lower-limb muscle groups: the hip flexor, knee flexor, ankle dorsiflexor and ankle plantarflexor. [Conclusion] These findings suggest that a Wii balance board exercise program can be used to improve the balance and lower limb muscle strength of overweight young adults. PMID:25642034

  17. Wii balance board exercise improves balance and lower limb muscle strength of overweight young adults.

    PubMed

    Siriphorn, Akkradate; Chamonchant, Dannaovarat

    2015-01-01

    [Purpose] The potential health benefits of the Nintendo Wii balance board exercise have been widely investigated. However, no study has been conducted to examine the benefits of Wii exercise for overweight young adults. The aim of this study was to investigate the effect of exercise performed on a Nintendo Wii balance board on the balance and lower limb muscle strength in overweight young adults. [Subjects and Methods] Within-subject repeated measures analysis was used. Sixteen young adults (aged 21.87±1.13 years, body mass index 24.15 ± 0.50 kg/m(2)) were recruited. All subjects performed an exercise program on a Wii balance board for 8 weeks (30 min/session, twice a week for 8 weeks). A NeuroCom Balance Master and a hand-held dynamometer were used to measure balance performance and lower limb muscle strength. [Results] According to the comparison of pre- and post-intervention measurements, the Wii balance board exercise program significantly improved the limit of stability parameters. There was also a significant increase in strength of four lower-limb muscle groups: the hip flexor, knee flexor, ankle dorsiflexor and ankle plantarflexor. [Conclusion] These findings suggest that a Wii balance board exercise program can be used to improve the balance and lower limb muscle strength of overweight young adults. PMID:25642034

  18. Muscle strength and bone density in patients with different rheumatic conditions: cross-sectional study

    PubMed Central

    Cvijetić, Selma; Grazio, Simeon; Gomzi, Milica; Krapac, Ladislav; Nemčić, Tomislav; Uremović, Melita; Bobić, Jasminka

    2011-01-01

    Aim To explore the relationship between muscle strength and bone density in patients with different rheumatic diseases and to examine whether inflammatory arthritis was more harmful for muscle strength and bone loss than degenerative joint diseases. Methods The study included 361 men and women with a mean ± standard deviation age of 60.5 ± 11.4 years and different rheumatic conditions: regional syndromes, osteoarthritis of the hands, shoulders, knees, and hips, and inflammatory arthritis. Maximum voluntary back strength was measured by isometric dynamometry. Bone mineral density (BMD; g/cm2) of the lumbar spine, femoral neck, and distal radius was measured by dual-energy x-ray absorptiometry. Anthropometry and lifestyle characteristics were also assessed. Results Back strength was lowest in patients with hand and shoulder osteoarthritis (20.0 ± 17.9 kg), followed by patients with inflammatory arthritis (24.8 ± 19.2 kg). Patients with inflammatory arthritis had the lowest BMD at the mid-radius (0.650 ± 0.115 g/cm2) and femoral neck (0.873 ± 0.137 g/cm2), while patients with hand and shoulder osteoarthritis had the lowest BMD at the mid-radius (0.660 ± 0.101). In both sexes, muscle strength was significantly lower in patients who had lower BMD (T score<-1.0). Multiple regression analysis identified significant predictors of back strength to be spine BMD (P = 0.024) and body mass index (P = 0.004) in men and femoral neck BMD in women (P = 0.004). Conclusion Muscle strength decline may be connected to bone loss in patients with rheumatic conditions, especially those with inflammatory joint diseases. PMID:21495199

  19. Low muscle strength in late adolescence and Parkinson disease later in life

    PubMed Central

    Gustafsson, Helena; Aasly, Jan; Stråhle, Stefan; Nordström, Anna

    2015-01-01

    Objective: To evaluate maximal isometric muscle force at 18 years of age in relation to Parkinson disease (PD) later in life. Methods: The cohort consisted of 1,317,713 men who had their muscle strength measured during conscription (1969–1996). Associations between participants' muscle strength at conscription and PD diagnoses, also in their parents, were examined using multivariate statistical models. Results: After adjustment for confounders, the lowest compared to the highest fifth of handgrip strength (hazard ratio [HR] 1.38, 95% confidence interval [CI] 1.06–1.79), elbow flexion strength (HR 1.34, 95% CI 1.02–1.76), but not knee extension strength (HR 1.24, 95% CI 0.94–1.62) was associated with an increased risk of PD during follow-up. Furthermore, men whose parents were diagnosed with PD had reduced handgrip (fathers: mean difference [MD] −5.7 N [95% CI −7.3 to −4.0]; mothers: MD −5.0 N [95% CI −7.0 to −2.9]) and elbow flexion (fathers: MD −4.3 N [95% CI −5.7 to −2.9]; mothers: MD −3.9 N [95% CI −5.7 to −2.2]) strength, but not knee extension strength (fathers: MD −1.1 N [95% CI −2.9 to 0.8]; mothers: MD −0.7 N [95% CI −3.1 to 1.6]), than those with no such familial history. Conclusions: Maximal upper extremity voluntary muscle force was reduced in late adolescence in men diagnosed with PD 30 years later. The findings suggest the presence of subclinical motor deficits 3 decades before the clinical onset of PD. PMID:25841033

  20. Effect of the cervical flexion angle during smart phone use on muscle fatigue of the cervical erector spinae and upper trapezius

    PubMed Central

    Lee, Sangyong; Lee, Daehee; Park, Jungseo

    2015-01-01

    [Purpose] The purpose of this study was to examine the influence of the cervical flexion angle when using a smart phone on muscle fatigue of the cervical erector spinae (CES) and upper trapezius (UT). [Subjects] This study recruited 12 healthy adults. [Methods] Each subject sat on a chair, with his/her back against the wall and held a smart phone with both hands. Fatigue of the neck and shoulder muscles at different cervical flexion angles (0°, 30°, and 50°) was measured by electromyography. The following muscles were assessed: the right upper trapezius (RtUT), left upper trapezius (LtUT), right cervical erector spinae (RtCES), and left cervical erector spinae (LtCES). A cervical range of motion instrument was attached to the subjects’ heads to measure the cervical angle during the experiment. [Results] The RtUT and LtUT showed the highest muscle fatigue at a cervical flexion angle of 50° and the lowest fatigue at an angle of 30°. There was no significant difference in the muscle fatigue of the RtCES and LtCES at any of the cervical flexion angles. [Conclusion] UT muscle fatigue depends on the cervical flexion angle when using a smart phone. PMID:26180333

  1. Test-retest reliability of isometric shoulder muscle strength measurement with a handheld dynamometer and belt

    PubMed Central

    Katoh, Munenori

    2015-01-01

    [Purpose] The aim of this study was to develop a method of measuring isometric shoulder joint muscle strength using a handheld dynamometer with a belt and investigate its test-retest reliability. [Subjects] The subjects comprised 40 healthy adults. [Methods] Six types of isometric shoulder muscle strength were measured twice, and reliability was assessed. [Results] The intraclass correlation coefficient (1, 1) values ranged from 0.976 to 0.902. The result of a Bland-Altman analysis showed differences in the types of errors between measurement items. [Conclusion] The relative reliability of isometric shoulder muscle measurement using a handheld dynamometer with a belt was high. However, analysis of absolute reliability revealed errors that may affect interpretation of values; therefore, it was considered that adapting the greater of two measurement values is appropriate. PMID:26180305

  2. A narrative review of exercise-associated muscle cramps: Factors that contribute to neuromuscular fatigue and management implications.

    PubMed

    Nelson, Nicole L; Churilla, James R

    2016-08-01

    Although exercise-associated muscle cramps (EAMC) are highly prevalent among athletic populations, the etiology and most effective management strategies are still unclear. The aims of this narrative review are 3-fold: (1) briefly summarize the evidence regarding EAMC etiology; (2) describe the risk factors and possible physiological mechanisms associated with neuromuscular fatigue and EAMC; and (3) report the current evidence regarding prevention of, and treatment for, EAMC. Based on the findings of several large prospective and experimental investigations, the available evidence indicates that EAMC is multifactorial in nature and stems from an imbalance between excitatory drive from muscle spindles and inhibitory drive from Golgi tendon organs to the alpha motor neurons rather than dehydration or electrolyte deficits. This imbalance is believed to stem from neuromuscular overload and fatigue. In concert with these findings, the most successful treatment for an acute bout of EAMC is stretching, whereas auspicious methods of prevention include efforts that delay exercise-induced fatigue. Muscle Nerve 54: 177-185, 2016. PMID:27159592

  3. The Effect of Stage II Posterior Tibial Tendon Dysfunction on Deep Compartment Muscle Strength: A New Strength Test

    PubMed Central

    Houck, Jeff R.; Nomides, Candace; Neville, Christopher Glenn; Flemister, Adolph Samuel

    2010-01-01

    Background The purpose of this study was to compare isometric subtalar inversion and forefoot adduction strength in subjects with Stage II posterior tibial tendon dysfunction (PTTD) to controls. Materials and Methods Twenty four subjects with Stage II PTTD and fifteen matched controls volunteered for this study. A force transducer (Model SML-200, Interface, Scottsdale, AZ) was connected with a resistance plate and oscilloscope (TDS 410A, Tektronix, Beaverton, OR) to the foot. Via the oscilloscope, subjects were given feedback on the amount of force produced and muscle activation of the anterior tibialis (AT) muscle. Subjects were instructed to maintain a plantar flexion force while performing a maximal voluntary subtalar inversion and forefoot adduction effort. A two-way ANOVA model with the factors including, side (involved/uninvolved) and group (control/PTTD) was used. Results The PTTD group on the involved side showed significantly decreased subtalar inversion and foot adduction strength (0.70 ± 0.24 N/Kg) compared to the uninvolved side (0.94 ± 0.24 N/Kg) and controls (involved side = 0.99 ± 0.24 N/Kg, uninvolved side = 0.97 ± 0.21 N/Kg). The average AT activation was between 11–17% for both groups, however, showing considerable variability in subjects with PTTD. Conclusion These data confirm a subtalar inversion and forefoot adduction strength deficit by 20% to 30% in subjects with Stage II PTTD. Although isolating the PT muscle is difficult, a test specific to subtalar inversion and forefoot adduction demonstrated the weakness in this population. PMID:18778667

  4. Skeletal muscle fat content is inversely associated with bone strength in young girls.

    PubMed

    Farr, Joshua N; Funk, Janet L; Chen, Zhao; Lisse, Jeffrey R; Blew, Robert M; Lee, Vinson R; Laudermilk, Monica; Lohman, Timothy G; Going, Scott B

    2011-09-01

    Childhood obesity is an established risk factor for metabolic disease. The influence of obesity on bone development, however, remains controversial and may depend on the pattern of regional fat deposition. Therefore, we examined the associations of regional fat compartments of the calf and thigh with weight-bearing bone parameters in girls. Data from 444 girls aged 9 to 12 years from the Jump-In: Building Better Bones study were analyzed. Peripheral quantitative computed tomography (pQCT) was used to assess bone parameters at metaphyseal and diaphyseal sites of the femur and tibia along with subcutaneous adipose tissue (SAT, mm(2) ) and muscle density (mg/cm(3) ), an index of skeletal muscle fat content. As expected, SAT was positively correlated with total-body fat mass (r = 0.87-0.89, p < .001), and muscle density was inversely correlated with total-body fat mass (r = -0.24 to -0.28, p < .001). Multiple linear regression analyses with SAT, muscle density, muscle cross-sectional area, bone length, maturity, and ethnicity as independent variables showed significant associations between muscle density and indices of bone strength at metaphyseal (β = 0.13-0.19, p < .001) and diaphyseal (β = 0.06-0.09, p < .01) regions of the femur and tibia. Associations between SAT and indices of bone strength were nonsignificant at all skeletal sites (β = 0.03-0.05, p > .05), except the distal tibia (β = 0.09, p = .03). In conclusion, skeletal muscle fat content of the calf and thigh is inversely associated with weight-bearing bone strength in young girls. PMID:21544865

  5. Muscle activation and knee biomechanics during squatting and lunging after lower extremity fatigue in healthy young women.

    PubMed

    Longpré, Heather S; Acker, Stacey M; Maly, Monica R

    2015-02-01

    Muscle activations and knee joint loads were compared during squatting and lunging before and after lower extremity neuromuscular fatigue. Electromyographic activations of the rectus femoris, vastus lateralis and biceps femoris, and the external knee adduction and flexion moments were collected on 25 healthy women (mean age 23.5 years, BMI of 23.7 kg/m(2)) during squatting and lunging. Participants were fatigued through sets of 50 isotonic knee extensions and flexions, with resistance set at 50% of the peak torque achieved during a maximum voluntary isometric contraction. Fatigue was defined as a decrease in peak isometric knee extension or flexion torque ≥25% from baseline. Co-activation indices were calculated between rectus femoris and biceps femoris; and between vastus lateralis and biceps femoris. Fatigue decreased peak isometric extension and flexion torques (p<0.05), mean vastus lateralis activation during squatting and lunging (p<0.05), and knee adduction and flexion moments during lunging (p<0.05). Quadriceps activations were greater during lunging than squatting (p<0.05). Thus, fatigue altered the recruitment strategy of the quadriceps during squatting and lunging. Lunging challenges quadriceps activation more than squatting in healthy, young women. PMID:25258248

  6. Strength and muscle activity of shoulder external rotation of subjects with and without scapular dyskinesis

    PubMed Central

    Uga, Daisuke; Nakazawa, Rie; Sakamoto, Masaaki

    2016-01-01

    [Purpose] This study aimed to clarify the relationship between scapular dyskinesis and shoulder external rotation strength and muscle activity. [Subjects and Methods] Both shoulders of 20 healthy males were evaluated. They were classified into 19 normal, 8 subtly abnormal, and 13 obviously abnormal shoulders using the scapular dyskinesis test. Subtly abnormal shoulders were subsequently excluded from the analysis. Shoulder external rotation strength and muscle activity (infraspinatus, serratus anterior, upper, middle, and lower trapezius) were measured in 2 positions using a handheld dynamometer and surface electromyography while sitting in a chair with shoulder 0° abduction and flexion (1st position), and while lying prone on the elbows with the shoulders elevated in the zero position (zero position). The strength ratio was calculated to quantify the change in strength between the positions (zero position / 1st position). [Results] In the obviously abnormal shoulder group, the strength in the 1st position was significantly stronger, the strength ratio was significantly smaller, and the serratus anterior in the zero position showed significantly lower activity than the normal shoulder group. [Conclusion] In shoulder external rotation in the zero position, in obviously abnormal shoulders, the serratus anterior is poorly recruited, weakening the shoulder external rotation strength. PMID:27190434

  7. Anti-myostatin antibody increases muscle mass and strength and improves insulin sensitivity in old mice

    PubMed Central

    Camporez, João-Paulo G.; Petersen, Max C.; Abudukadier, Abulizi; Moreira, Gabriela V.; Jurczak, Michael J.; Friedman, Glenn; Haqq, Christopher M.; Petersen, Kitt Falk; Shulman, Gerald I.

    2016-01-01

    Sarcopenia, or skeletal muscle atrophy, is a debilitating comorbidity of many physiological and pathophysiological processes, including normal aging. There are no approved therapies for sarcopenia, but the antihypertrophic myokine myostatin is a potential therapeutic target. Here, we show that treatment of young and old mice with an anti-myostatin antibody (ATA 842) for 4 wk increased muscle mass and muscle strength in both groups. Furthermore, ATA 842 treatment also increased insulin-stimulated whole body glucose metabolism in old mice, which could be attributed to increased insulin-stimulated skeletal muscle glucose uptake as measured by a hyperinsulinemic-euglycemic clamp. Taken together, these studies provide support for pharmacological inhibition of myostatin as a potential therapeutic approach for age-related sarcopenia and metabolic disease. PMID:26858428

  8. Effects of Training Attendance on Muscle Strength of Young Men after 11 Weeks of Resistance Training

    PubMed Central

    Gentil, Paulo; Bottaro, Martim

    2013-01-01

    Purpose Training attendance is an important variable for attaining optimal results after a resistance training (RT) program, however, the association of attendance with the gains of muscle strength is not well defined. Therefore, the purpose of the present study is to verify if attendance would affect muscle strength gains in healthy young males. Methods Ninety two young males with no previous RT experience volunteered to participate in the study. RT was performed 2 days a week for 11 weeks. One repetition maximum (1RM) in the bench press and knee extensors peak torque (PT) were measured before and after the training period. After the training period, a two step cluster analysis was used to classify the participants in accordance to training attendance, resulting in three groups, defined as high (92 to 100%), intermediate (80 to 91%) and low (60 to 79%) training attendance. Results According to the results, there were no significant correlations between strength gains and training attendance, however, when attendance groups were compared, the low training attendance group showed lower increases in 1RM bench press (8.8%) than the other two groups (17.6% and 18.0% for high and intermediate attendance, respectively). Conclusions Although there is not a direct correlation between training attendance and muscle strength gains, it is suggested that a minimum attendance of 80% is necessary to ensure optimal gains in upper body strength. PMID:23802051

  9. Associations of fatigue from mid to late life with physical performance and strength in early old age: Results from a British prospective cohort study

    PubMed Central

    Mänty, Minna; Kuh, Diana; Cooper, Rachel

    2015-01-01

    OBJECTIVE To examine associations of fatigue in mid and later life with physical performance and strength in early old age. METHODS Data on approximately 1800 men and women from the UK Medical Research Council National Survey of Health and Development with data on fatigue at ages 43 and 60-64 years were used. Fatigue was defined as perceived tiredness and was assessed prospectively at ages 43 and 60-64. At both ages, participants were categorized as having no, occasional or frequent fatigue. Physical performance and strength were measured at age 60-64 using four objective measures: grip strength, standing balance, chair rising, and timed get-up-and-go (TUG) tests. RESULTS There were associations between reports of frequent fatigue at both ages and poorer grip strength, chair rise and TUG performance at 60-64 years. Furthermore, individuals reporting frequent fatigue at both ages had weaker grip strength (β -4.09 kg, 95% CI -6.71, -1.48), and slower chair rise (β -4.65 rep./min, 95% CI -6.65, -2.64) and TUG (β -4.22 cm/s, 95% CI -12.16, -2.28) speeds when compared to those who reported no fatigue at both time points. These associations were robust and were maintained after adjustment for a range of covariates including physical activity and health status. CONCLUSIONS Reports of frequent fatigue were associated with poorer physical performance in early old age, especially if sustained from mid to later life. These findings indicate that it is not just fatigue but fatigue sustained across adulthood that has implications for later life functioning. PMID:26176776

  10. Association of Muscle Mass, Area, and Strength With Incident Diabetes in Older Adults: The Health ABC Study.

    PubMed

    Larsen, Britta A; Wassel, Christina L; Kritchevsky, Stephen B; Strotmeyer, Elsa S; Criqui, Michael H; Kanaya, Alka M; Fried, Linda F; Schwartz, Ann V; Harris, Tamara B; Ix, Joachim H

    2016-04-01

    The role of muscle in development of metabolic conditions is poorly understood. The authors show that, while there was no overall association between muscle mass, area, and strength and incident diabetes in older adults, more muscle at baseline was protective against incident diabetes for normal weight women. PMID:26930180

  11. Muscle Fatigue in the Three Heads of the Triceps Brachii During a Controlled Forceful Hand Grip Task with Full Elbow Extension Using Surface Electromyography

    PubMed Central

    Ali, Asraf; Sundaraj, Kenneth; Badlishah Ahmad, R.; Ahamed, Nizam Uddin; Islam, Anamul; Sundaraj, Sebastian

    2015-01-01

    The objective of the present study was to investigate the time to fatigue and compare the fatiguing condition among the three heads of the triceps brachii muscle using surface electromyography during an isometric contraction of a controlled forceful hand grip task with full elbow extension. Eighteen healthy subjects concurrently performed a single 90 s isometric contraction of a controlled forceful hand grip task and full elbow extension. Surface electromyographic signals from the lateral, long and medial heads of the triceps brachii muscle were recorded during the task for each subject. The changes in muscle activity among the three heads of triceps brachii were measured by the root mean square values for every 5 s period throughout the total contraction period. The root mean square values were then analysed to determine the fatiguing condition for the heads of triceps brachii muscle. Muscle fatigue in the long, lateral, and medial heads of the triceps brachii started at 40 s, 50 s, and 65 s during the prolonged contraction, respectively. The highest fatiguing rate was observed in the long head (slope = −2.863), followed by the medial head (slope = −2.412) and the lateral head (slope = −1.877) of the triceps brachii muscle. The results of the present study concurs with previous findings that the three heads of the triceps brachii muscle do not work as a single unit, and the fiber type/composition is different among the three heads. PMID:26240650

  12. Gigacycle Fatigue Properties of High-Strength Steels According to Inclusion and ODA Sizes

    NASA Astrophysics Data System (ADS)

    Furuya, Y.; Hirukawa, H.; Kimura, T.; Hayaishi, M.

    2007-08-01

    Gigacycle fatigue tests were conducted for several versions of JIS-SCM440 low-alloy and JIS-SUJ2 bearing steels using 20-kHz ultrasonic fatigue testing to elucidate the relationship of the inclusion size and type to fish-eye fracture properties. The total number of tested specimens was over 200. Most of the specimens revealed Al2O3 or (Cr, Fe)3C inclusion-originating types of fish-eye fractures, while TiN inclusions and the matrix also caused fish-eye fractures in some specimens. Based on these fatigue test results, 109-cycle fatigue limits were estimated according to inclusion size by resorting the obtained data points according to their inclusion sizes at the fish-eye fracture origin. The estimated fatigue limits revealed saturation when the inclusion sizes were smaller than 15 μm, while those fatigue limits depended on the inclusion sizes to the -1/6th power in the case of inclusions above 15 μm in size. The saturation of the 109-cycle fatigue limits was considered to be caused by the effects of the optically dark areas (ODAs). Moreover, the fatigue limits also depended on inclusion type. In comparing the Al2O3 and (Cr, Fe)3C inclusions, the key features causing the difference in the fatigue limits were likely to be bonding between the inclusion and the matrix, i.e., the (Cr, Fe)3C inclusions were tightly bonded to the matrix, unlike the Al2O3 inclusions, although both inclusions were of the hard type.

  13. The potential use of spectral electromyographic fatigue as a screening and outcome monitoring tool of sarcopenic back muscle alterations

    PubMed Central

    2014-01-01

    Background To examine whether or not median frequency surface electromyographic (MF-EMG) back muscle fatigue monitoring would be able to identify alterations in back muscle function in elderly muscles, if a protocol was used that allowed optimum standardization of the processes underlying electromyographic fatigue, and whether these tests were reliable from day to day. Methods A total of 42 older (21 females; 67 (±10.5) years old) and 44 younger persons (19 females; 33 (±10) years) performed maximum isometric back extensions which were followed by one 30 s lasting 80% submaximum extension. Participants were seated on a dynamometer with their trunks 30° anteflexed, and they repeated all tests after 1-2 days and 6 weeks. SEMG was recorded bilaterally from the L1 (iliocostalis lumborum), L2 (longissimus), and L5 (multifidus) recording sites. Outcome variables included maximum back extension torque, initial MF-EMG (IMF-EMG), MF-EMG slope declines, and individual MF-EMG muscular imbalance scores. Two-factorial ANOVAs served to examine the age and gender-specific effects, and models from Generalizability Theory (G-Theory) were used for assessing retest-reliability. Results Maximum back extension moment was non-significantly smaller in elders. IMF-EMG was overall higher in elders, with significant differences at the L5 recordings sites. In the elderly, MF-EMG fatigue declines were significantly smaller in L5, in the recording with the most negative slope, or if the slope of all electrodes was considered. Retest reliability was unanimous in young and older persons. ICC-type measurements from G-Theory of both the IMF and the fatigue slopes ranged from 0.7 to 0.85. Absolute SEM values were found clinically acceptable for the IMF-EMG, but relatively high for the fatigue slope declines. Conclusions The MF-EMG fatigue method is able to elucidate alterations of aging back muscles. This method, thus, might be suggested as a potential biomarker to objectively identify

  14. Fatigue Strength Prediction for Titanium Alloy TiAl6V4 Manufactured by Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Leuders, Stefan; Vollmer, Malte; Brenne, Florian; Tröster, Thomas; Niendorf, Thomas

    2015-09-01

    Selective laser melting (SLM), as a metalworking additive manufacturing technique, received considerable attention from industry and academia due to unpreceden