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Sample records for muscle strength fatiguability

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

    PubMed

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

    2015-07-01

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

  2. 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.

  3. 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

  4. Effects of age and muscle action type on acute strength and power recovery following fatigue of the leg flexors.

    PubMed

    Thompson, Brennan J; Conchola, Eric C; Stock, Matt S

    2015-12-01

    Short-term strength and power recovery patterns following fatigue have received little research attention, particularly as they pertain to age-specific responses, and the leg flexors (i.e., hamstrings) muscle group. Thus, research is warranted addressing these issues because both age-related alterations in the neuromuscular system and mode of muscle action (e.g., eccentric, concentric, isometric) may differentially influence recovery responses from fatigue. The aim of this study was to investigate the strength and power recovery responses for eccentric, concentric, and isometric muscle actions of the leg flexors in young and older men following an isometric, intermittent fatigue-inducing protocol. Nineteen young (age = 25 ± 3 years) and nineteen older (71 ± 4) men performed maximal voluntary contractions (MVCs) for eccentric, concentric, and isometric muscle actions followed by a fatigue protocol of intermittent (0.6 duty cycle) isometric contractions of the leg flexors at 60% of isometric MVC. MVCs of each muscle action were performed at 0, 7, 15, and 30 min following fatigue. Peak torque (PT) and mean power values were calculated from the MVCs and the eccentric/concentric ratio (ECR) was derived. For PT and mean power, young men showed incomplete recovery at all time phases, whereas the older men had recovered by 7 min. Eccentric and isometric muscle actions showed incomplete recovery at all time phases, but concentric recovered by 7 min, independent of age. The ECR was depressed for up to 30 min following fatigue. More rapid and pronounced recovery in older men and concentric contractions may be related to physiological differences specific to aging and muscle action motor unit patterns. Individuals and clinicians may use these time course responses as a guide for recovery following activity-induced fatigue.

  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

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

    2014-01-01

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

  7. 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.

  8. An indentation fatigue strength law

    NASA Astrophysics Data System (ADS)

    Xu, Baoxing; Yonezu, Akio; Chen, Xi

    2010-05-01

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

  9. Arterial elasticity, strength, fatigue, and endurance in older women.

    PubMed

    Hunter, Gary R; Neumeier, William H; Bickel, C Scott; McCarthy, John P; Fisher, Gordon; Chandler-Laney, Paula C; Glasser, Stephen P

    2014-01-01

    Arterial health may influence muscle function in older adults. Study purpose was to determine whether arterial elasticity is related to strength, central and peripheral fatigue, fatigue at rest, and treadmill endurance. Subjects were 91 healthy women aged >60. Treadmill endurance and maximal oxygen uptake (VO2 max) were measured. Peripheral and central fatigue for the knee extensors were evaluated using two isometric fatigue tests (one voluntary and one adding electrical stimulation). Arterial elasticity was determined using radial artery pulse wave analysis. Linear multiple regression was used in statistical analysis. Large artery elasticity was associated with central fatigue (P < 0.01) and treadmill endurance (P < 0.02) after adjusting for VO2 max and knee extension strength. Subjective fatigue at rest was related to large artery elasticity after adjusting for ethnic origin (<0.02). Strength was significantly related to small artery elasticity after adjusting for ethnic origin, leg lean tissue, age, and blood pressure. Arterial elasticity is independently related to strength and fatigue in older women, especially in the central nervous system where arterial elasticity is independently related to perceptions of fatigue at rest and central fatigue. These results suggest that arterial health may be involved with the ability of the central nervous system to activate muscle in older women.

  10. Bonded joint strength - Static versus fatigue

    NASA Technical Reports Server (NTRS)

    Johnson, W. S.; Mall, S.

    1984-01-01

    Adhesives are commonly characterized only by their static strength even though they are used in structural joints that are subjected to fatigue loads. This paper reviews the relationship between static and fatigue strength for four different specimen types: single-lap-shear, edge-delamination, double cantilever beam, and cracked-lap-shear. It was found that the ratio of static strength to fatigue strength varied from 2.3 to 4.7, depending on the adhesive and specimen configuration.

  11. 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....

  12. 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....

  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, 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....

  15. 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....

  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. Muscle glycogen stores and fatigue.

    PubMed

    Ørtenblad, Niels; Westerblad, Håkan; Nielsen, Joachim

    2013-09-15

      Studies performed at the beginning of the last century revealed the importance of carbohydrate as a fuel during exercise, and the importance of muscle glycogen on performance has subsequently been confirmed in numerous studies. However, the link between glycogen depletion and impaired muscle function during fatigue is not well understood and a direct cause-and-effect relationship between glycogen and muscle function remains to be established. The use of electron microscopy has revealed that glycogen is not homogeneously distributed in skeletal muscle fibres, but rather localized in distinct pools. Furthermore, each glycogen granule has its own metabolic machinery with glycolytic enzymes and regulating proteins. One pool of such glycogenolytic complexes is localized within the myofibrils in close contact with key proteins involved in the excitation-contraction coupling and Ca2+ release from the sarcoplasmic reticulum (SR). We and others have provided experimental evidence in favour of a direct role of decreased glycogen, localized within the myofibrils, for the reduction in SR Ca2+ release during fatigue. This is consistent with compartmentalized energy turnover and distinctly localized glycogen pools being of key importance for SR Ca2+ release and thereby affecting muscle contractility and fatigability.

  18. Muscle glycogen stores and fatigue

    PubMed Central

    Ørtenblad, Niels; Westerblad, Håkan; Nielsen, Joachim

    2013-01-01

    Studies performed at the beginning of the last century revealed the importance of carbohydrate as a fuel during exercise, and the importance of muscle glycogen on performance has subsequently been confirmed in numerous studies. However, the link between glycogen depletion and impaired muscle function during fatigue is not well understood and a direct cause-and-effect relationship between glycogen and muscle function remains to be established. The use of electron microscopy has revealed that glycogen is not homogeneously distributed in skeletal muscle fibres, but rather localized in distinct pools. Furthermore, each glycogen granule has its own metabolic machinery with glycolytic enzymes and regulating proteins. One pool of such glycogenolytic complexes is localized within the myofibrils in close contact with key proteins involved in the excitation–contraction coupling and Ca2+ release from the sarcoplasmic reticulum (SR). We and others have provided experimental evidence in favour of a direct role of decreased glycogen, localized within the myofibrils, for the reduction in SR Ca2+ release during fatigue. This is consistent with compartmentalized energy turnover and distinctly localized glycogen pools being of key importance for SR Ca2+ release and thereby affecting muscle contractility and fatigability. PMID:23652590

  19. Weakening of Functional Corticomuscular Coupling during Muscle Fatigue

    PubMed Central

    Yang, Qi; Fang, Yin; Sun, Chang-Kai; Siemionow, Vlodek; Ranganathan, Vinoth K.; Khoshknabi, Dilara; Davis, Mellar P.; Walsh, Declan; Sahgal, Vinod; Yue, Guang H.

    2009-01-01

    Objective Recent research has shown dissociation between changes in brain and muscle signals during voluntary muscle fatigue, which may suggest weakening of functional corticomuscular coupling. However, this weakening of brain-muscle coupling has never been directly evaluated. The purpose of this study was to address this issue by quantifying EEG-EMG coherence at times when muscles experienced minimal versus significant fatigue. Methods Nine healthy subjects sustained an isometric elbow flexion at 30% maximal level until exhaustion while their brain (EEG) and muscle (EMG) activities were recorded. The entire duration of the EEG and EMG recordings was divided into the first half (stage 1 with minimal fatigue) and second half (stage 2 with severer fatigue). The EEG-EMG coherence and power spectrum in each stage was computed. Results The power of both EEG and EMG increased significantly while their coherence decreased significantly in stage 2 compared with stage 1 at beta (15-35 Hz) band. Conclusions Despite an elevation of the power for both the EEG and EMG activities with muscle fatigue, the fatigue weakens strength of brain-muscle signal coupling at beta frequency. Significance Weakening of corticomuscular coupling may be a major neural mechanism contributing to muscle fatigue and associated performance impairment. PMID:19028460

  20. Recovery of gait after quadriceps muscle fatigue.

    PubMed

    Barbieri, Fabio Augusto; Beretta, Stephannie Spiandor; Pereira, Vinicius A I; Simieli, Lucas; Orcioli-Silva, Diego; dos Santos, Paulo Cezar Rocha; van Dieën, Jaap H; Gobbi, Lilian Teresa Bucken

    2016-01-01

    The aim of this study was to investigate the effect of recovery time after quadriceps muscle fatigue on gait in young adults. Forty young adults (20-40 years old) performed three 8-m gait trials at preferred velocity before and after muscle fatigue, and after 5, 10 and 20min of passive rest. In addition, at each time point, two maximal isometric voluntary contractions were preformed. Muscle fatigue was induced by repeated sit-to-stand transfers until task failure. Spatio-temporal, kinetic and muscle activity parameters, measured in the central stride of each trial, were analyzed. Data were compared between before and after the muscle fatigue protocol and after the recovery periods by one-way repeated measures ANOVA. The voluntary force was decreased after the fatigue protocol (p<0.001) and after 5, 10 and 20min of recovery compared to before the fatigue protocol. Step width (p<0.001) and RMS of biceps femoris (p<0.05) were increased immediately after the fatigue protocol and remained increased after the recovery periods. In addition, stride duration was decreased immediately after the fatigue protocol compared to before and to after 10 and 20min of rest (p<0.001). The anterior-posterior propulsive impulse was also decreased after the fatigue protocol (p<0.001) and remained low after 5, 10 and 20min of rest. We conclude that 20min is not enough to see full recovery of gait after exhaustive quadriceps muscle fatigue.

  1. 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.

  2. Fatiguing exercise enhances hyperalgesia to muscle inflammation.

    PubMed

    Sluka, Kathleen A; Rasmussen, Lynn A

    2010-02-01

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

  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. 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

  5. Mechanisms of exertional fatigue in muscle glycogenoses.

    PubMed

    Vissing, John; Haller, Ronald G

    2012-12-01

    Exertional fatigue early in exercise is a clinical hallmark of muscle glycogenoses, which is often coupled with painful muscle contractures and episodes of myoglobinuria. A fundamental biochemical problem in these conditions is the impaired generation of ATP to fuel muscle contractions, which relates directly to the metabolic defect, but also to substrate-limited energy deficiency, as exemplified by the "second wind" phenomenon in McArdle disease. A number of secondary events may also play a role in inducing premature fatigue in glycogenoses, including (1) absent or blunted muscle acidosis, which may be important for maintaining muscle membrane excitability by decreasing chloride permeability, (2) loss of the osmotic effect related to lactate accumulation, which may account for absence of the normal increase in water content of exercised muscle, and thus promote higher than normal concentrations of extracellular potassium in exercising muscle and (3) exaggerated accumulation of ADP during exercise that may inhibit sodium-potassium and calcium-ATPases. Disorders of muscle glycogenolysis and glycolysis reveal the crucial role of these metabolic processes for supplying both anaerobic and aerobic energy for muscle contraction; and the pathological fatigue that occurs when glycogenolysis and/or glycolysis is blocked imply an important role for theses metabolic pathways in normal muscle fatigue. PMID:23182633

  6. 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.

  7. Measurement of fatigue in knee flexor and extensor muscles.

    PubMed

    Kawabata, Y; Senda, M; Oka, T; Yagata, Y; Takahara, Y; Nagashima, H; Inoue, H

    2000-04-01

    In order to examine fatigue of the knee flexor and extensor muscles and to investigate the characteristics of muscular fatigue in different sports, a Cybex machine was used to measure muscle fatigue and recovery during isokinetic knee flexion and extension. Eighteen baseball players, 12 soccer players and 13 marathon runners were studied. Each subject was tested in the sitting position and made to perform 50 consecutive right knee bends and stretches at maximum strength. This was done 3 times with an interval of 10 min between each series. The peak torque to body weight ratio and the fatigue rate were determined in each case. In all subjects, the peak torque to body weight ratio was higher for extensors than flexors. Over the 3 trials, the fatigue rate of extensors showed little change, while that of flexors had a tendency to increase. In each subject, knee extensors showed a high fatigue rate but a quick recovery, while knee flexors showed a low fatigue rate but a slow recovery. As the marathon runners had the smallest fatigue rates for both flexors and extensors, we concluded that marathon runners had more stamina than baseball players and soccer players.

  8. 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.

  9. 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

  10. 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

  11. EFFECTS OF MUSCLE FATIGUE ON MULTI-MUSCLE SYNERGIES

    PubMed Central

    Singh, Tarkeshwar; Latash, Mark L.

    2011-01-01

    We studied the effects of fatigue of ankle dorsiflexors on multi-muscle synergies defined as co-varied adjustments of elemental variables (M-modes) that stabilize a task related performance variable (trajectory of the center of pressure, COP). M-modes were defined as muscle groups with parallel changes in activation levels. Healthy participants performed voluntary body sway in the anterior-posterior direction while trying to minimize sway in the medio-lateral direction at 0.25, 0.5 and 0.75 Hz. The trials were repeated before and during fatigue induced with a timed voluntary contraction against a constant load. Factor extraction using the principal component method was used to identify four M-modes within the space of integrated indices of muscle activity. Variance in the M-mode space at different phases across sway cycles was partitioned into two components, one that did not affect the average value of COP shift and the other that did. There were no significant effects of fatigue on variability of performance of the explicit task and on the amplitude of the COP shift. Variance of muscle activation indices and M-mode magnitudes increased during fatigue for muscles (and M-modes) both involved and not involved in the fatiguing exercise. Most of the M-mode variance increase was within the sub-space compatible with the unchanged COP trajectory resulting in an increase of the index of the multi-M-mode synergy. We conclude that one of the adaptive mechanisms to fatigue within a redundant multi-muscle system involves an increase in the variance of activation of non-fatigued muscles with a simultaneous increase in co-variation among muscle activations. The findings can be interpreted within the referent configuration hypothesis on the control of whole-body actions. PMID:21842189

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

    PubMed

    Singh, Tarkeshwar; Latash, Mark L

    2011-10-01

    We studied the effects of fatigue of ankle dorsiflexors on multi-muscle synergies defined as co-varied adjustments of elemental variables (M-modes) that stabilize a task-related performance variable (trajectory of the center of pressure, COP). M-modes were defined as muscle groups with parallel changes in activation levels. Healthy participants performed voluntary body sway in the anterior-posterior direction while trying to minimize sway in the medio-lateral direction at 0.25, 0.5, and 0.75 Hz. The trials were repeated before and during fatigue induced with a timed voluntary contraction against a constant load. Factor extraction using the principal component method was used to identify four M-modes within the space of integrated indices of muscle activity. Variance in the M-mode space at different phases across sway cycles was partitioned into two components, one that did not affect the average value of COP shift and the other that did. There were no significant effects of fatigue on variability of performance of the explicit task and on the amplitude of the COP shift. Variance of muscle activation indices and M-mode magnitudes increased during fatigue for muscles (and M-modes) both involved and not involved in the fatiguing exercise. Most of the M-mode variance increase was within the sub-space compatible with the unchanged COP trajectory resulting in an increase of the index of the multi-M-mode synergy. We conclude that one of the adaptive mechanisms to fatigue within a redundant multi-muscle system involves an increase in the variance of activation of non-fatigued muscles with a simultaneous increase in co-variation among muscle activations. The findings can be interpreted within the referent configuration hypothesis on the control of whole-body actions. PMID:21842189

  13. 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).

  14. 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

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

    PubMed Central

    Hui-li, Wang; Si-feng, Qin

    2014-01-01

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

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

    PubMed

    Hui-li, Wang; Si-feng, Qin

    2014-01-01

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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Sildenafil increases muscle protein synthesis and reduces muscle fatigue.

    PubMed

    Sheffield-Moore, Melinda; Wiktorowicz, John E; Soman, Kizhake V; Danesi, Christopher P; Kinsky, Michael P; Dillon, Edgar L; Randolph, Kathleen M; Casperson, Shannon L; Gore, Dennis C; Horstman, Astrid M; Lynch, James P; Doucet, Barbara M; Mettler, Joni A; Ryder, Jeffrey W; Ploutz-Snyder, Lori L; Hsu, Jean W; Jahoor, Farook; Jennings, Kristofer; White, Gregory R; McCammon, Susan D; Durham, William J

    2013-12-01

    Reductions in skeletal muscle function occur during the course of healthy aging as well as with bed rest or diverse diseases such as cancer, muscular dystrophy, and heart failure. However, there are no accepted pharmacologic therapies to improve impaired skeletal muscle function. Nitric oxide may influence skeletal muscle function through effects on excitation-contraction coupling, myofibrillar function, perfusion, and metabolism. Here we show that augmentation of nitric oxide-cyclic guanosine monophosphate signaling by short-term daily administration of the phosphodiesterase 5 inhibitor sildenafil increases protein synthesis, alters protein expression and nitrosylation, and reduces fatigue in human skeletal muscle. These findings suggest that phosphodiesterase 5 inhibitors represent viable pharmacologic interventions to improve muscle function. PMID:24330691

  2. 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.

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

    PubMed

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

    2006-10-01

    The purpose of the present study was to compare vertical jump performance after 2 different fatigue protocols. In the first protocol, subjects performed consecutive sets of 10 repetitions of stretch-shortening cycle (SSC) contractions. In the second protocol, successive sets of 10 repetitions of isometric contractions were performed for 10 s with the knee at 90 degrees of flexion. The exercises were stopped when the subjects failed to reach 50% of their maximum voluntary isometric contractions. Maximal isometric force and maximal concentric power were assessed by performing supine leg presses, squat jumps, and drop jumps. Surface EMG was used to determine changes in muscle activation before and after fatigue. In both groups, the fatigue exercises reduced voluntary isometric force, maximal concentric power, and drop jump performance. Kinematic data showed a decrease in knee muscle-tendon stiffness accompanied by a lengthened ground contact time. EMG analysis showed that the squat and drop jumps were performed similarly before and after the fatigue exercise for both groups. Although it was expected that the stiffness would decrease more after SSC than after isometric fatigue (as a result of a greater alteration of the reflex sensitivity SSC), our results showed that both protocols had a similar effect on knee muscle stiffness during jumping exercises. Both fatigue protocols induced muscle fatigue, and the decrease in jump performance was linked to a decrease in the strength and stiffness of the knee extensor muscles. PMID:17111011

  4. Flexural and fatigue strengths of root canal posts.

    PubMed

    Peutzfeldt, A; Asmussen, E

    1990-12-01

    This study measured the flexural and fatigue strengths of root canal posts of different alloy, design, and diameter. Fixed posts were loaded up to a preset force and the number of loadings endured until fracture was recorded at each loading force. The flexural strength was defined as the maximum force a post could endure before fracture when loaded once. The fatigue strength was determined as the maximum force a post could endure when loaded 10,000 times. Both modes of strength were found to increase with increasing diameter. Aluminum posts had lower flexural and fatigue strengths than posts of titanium, stainless steel, and a Ag-Pd alloy, all of which had strength values of about the same magnitude. Among the investigated brands, Triax and Radix were stronger than the others at comparable diameters. The high strength of Triax may be explained by the design of the post, whereas a superior alloy may account for the high strength of Radix.

  5. 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…

  6. 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.

  7. 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.

  8. 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.

  9. Effect of muscle fatigue on internal model formation and retention during reaching with the arm.

    PubMed

    Takahashi, Craig D; Nemet, Dan; Rose-Gottron, Christie M; Larson, Jennifer K; Cooper, Dan M; Reinkensmeyer, David J

    2006-02-01

    The motor system adapts to novel dynamic environments by forming internal models that predict the muscle forces needed to move skillfully. The goal of this study was to determine how muscle fatigue affects internal model formation during arm movement and whether an internal model acquired while fatigued could be recalled accurately after rest. Twelve subjects adapted to a viscous force field applied by a lightweight robot as they reached to a target. They then reached while being resisted by elastic bands until they could no longer touch the target. This protocol reduced the strength of the muscles used to resist the force field by approximately 20%. The bands were removed, and subjects adapted again to the viscous force field. Their adaptive ability, quantified by the amount and time constant of adaptation, was not significantly impaired following fatigue. The subjects then rested, recovering approximately 70% of their lost force-generation ability. When they reached in the force field again, their prediction of the force field strength was different than in a nonfatigued state. This alteration was consistent with the use of a higher level of effort than normally used to counteract the force field. These results suggest that recovery from fatigue can affect recall of an internal model, even when the fatigue did not substantially affect the motor system's ability to form the model. Recovery from fatigue apparently affects recall because the motor system represents internal models as a mapping between effort and movement and relies on practice to recalibrate this mapping.

  10. 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

  11. Tubule orientation and the fatigue strength of human dentin.

    PubMed

    Arola, Dwayne D; Reprogel, Robert K

    2006-03-01

    In this study the influence of tubule orientation on the strength of human dentin under static and cyclic loads was examined. Rectangular beams were sectioned from the coronal dentin of virgin extracted molars (N=83) and then loaded in quasi-static 4-point flexure or 4-point flexural fatigue to failure. The flexure strength, energy to fracture and fatigue strength were evaluated for specimens with the dentin tubules aligned parallel (theta=0 degrees ) and perpendicular (theta=90 degrees ) to the plane of maximum normal stress. Results from monotonic loading showed that both the flexural strength and energy to fracture of dentin specimens with theta=0 degrees were significantly greater than those with theta=90 degrees . Furthermore, the apparent endurance strength of dentin with theta=0 degrees (44MPa) was significantly greater than that of the dentin with theta=90 degrees (24MPa). The ratio of apparent endurance strength (for fully reversed loading) to the flexure strength for theta=0 degrees and theta=90 degrees was 0.41 and 0.28, respectively. Although the influence of tubule orientation was most important to mechanical behavior, the flexure strength and energy to fracture also decreased with an increase in tubule density. According to differences in the fatigue strength with tubule orientation, restorative practices promoting large cyclic normal stresses perpendicular to the tubules would be more likely to facilitate fatigue failure in dentin with cyclic loading.

  12. 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.

  13. 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.

  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. Peripheral and central fatigue after muscle-damaging exercise is muscle length dependent and inversely related.

    PubMed

    Skurvydas, Albertas; Brazaitis, Marius; Kamandulis, Sigitas; Sipaviciene, Saule

    2010-08-01

    Healthy untrained men performed 10 series of 12 knee eccentric extension repetitions (EE) at 160 degrees /s. The maximal voluntary isometric contraction force of the quadriceps muscle, the maximal rate of electrically induced torque development (RTD) and relaxation (RTR), isokinetic concentric torque at 30 degrees /s, the electrostimulation-induced torque at 20 and 100Hz frequencies were established before and after EE at shorter and longer muscle lengths. Besides, voluntary activation (VA) index and central activation ratio (CAR) were tested. There was more peripheral fatigue than central after EE. We established more central fatigue as well as low frequency fatigue at a shorter muscle length compared to the longer muscle length. Relative RTD as well as relative RTR, improved after EE and did not depend on the muscle length. Finally, central fatigue is inversely significantly related with the eccentric torque reduction during eccentric exercise and with the changes in muscle torque induced by low frequency stimulation.

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

    PubMed

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

    2006-01-01

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

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

    PubMed Central

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

    1993-01-01

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

  18. 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.

  19. 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.

  20. Respiratory muscle strength and muscle endurance are not affected by acute metabolic acidemia.

    PubMed

    Nizet, Tessa A C; Heijdra, Yvonne F; van den Elshout, Frank J J; van de Ven, Marjo J T; Bosch, Frank H; Mulder, Paul H; Folgering, Hans Th M

    2009-11-01

    Respiratory muscle fatigue in asthma and chronic obstructive lung disease (COPD) contributes to respiratory failure with hypercapnia, and subsequent respiratory acidosis. Therapeutic induction of acute metabolic acidosis further increases the respiratory drive and, therefore, may diminish ventilatory failure and hypercapnia. On the other hand, it is known that acute metabolic acidosis can also negatively affect (respiratory) muscle function and, therefore, could lead to a deterioration of respiratory failure. Moreover, we reasoned that the impact of metabolic acidosis on respiratory muscle strength and respiratory muscle endurance could be more pronounced in COPD patients as compared to asthma patients and healthy subjects, due to already impaired respiratory muscle function. In this study, the effect of metabolic acidosis was studied on peripheral muscle strength, peripheral muscle endurance, airway resistance, and on arterial carbon dioxide tension (PaCO(2)). Acute metabolic acidosis was induced by administration of ammonium chloride (NH(4)Cl). The effect of metabolic acidosis was studied on inspiratory and expiratory muscle strength and on respiratory muscle endurance. Effects were studied in a randomized, placebo-controlled cross-over design in 15 healthy subjects (4 male; age 33.2 +/- 11.5 years; FEV(1) 108.3 +/- 16.2% predicted), 14 asthma patients (5 male; age 48.1 +/- 16.1 years; FEV(1) 101.6 +/- 15.3% predicted), and 15 moderate to severe COPD patients (9 male; age 62.8 +/- 6.8 years; FEV(1) 50.0 +/- 11.8% predicted). An acute metabolic acidemia of BE -3.1 mmol x L(-1) was induced. Acute metabolic acidemia did not significantly affect strength or endurance of respiratory and peripheral muscles, respectively. In all subjects airway resistance was significantly decreased after induction of metabolic acidemia (mean difference -0.1 kPa x sec x L(-1) [95%-CI: -0.1 - -0.02]. In COPD patients PaCO(2) was significantly lowered during metabolic acidemia (mean

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    PubMed

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

    2014-01-01

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

  3. The role of motor neuron drive in muscle fatigue.

    PubMed

    Ranieri, Federico; Di Lazzaro, Vincenzo

    2012-12-01

    Large experimental evidence indicates that motor neuron drive plays an important role in the origin of fatigue. Some key findings from electrophysiological investigations provide evidence for central fatigue during prolonged exercise: (1) maximal voluntary activation is usually below maximal muscle force; (2) the amount of voluntary activation decreases and (3) motor unit firing rate tends to decline during maximal voluntary isometric contractions. Spinal and supra-spinal mechanisms can be involved. A fundamental contribution to the comprehension of these mechanisms is provided by non-invasive brain stimulation techniques, such as transcranial magnetic stimulation. They have revealed a general reduction of motor cortical excitability and central drive during fatiguing exercise, also confirmed by direct recording of corticospinal activity. Additional data suggesting concomitant intracortical inhibitory and facilitatory phenomena during sustained muscle contraction are discussed. The picture is made more complex in all pathological conditions where the motor unit pool is reduced by muscle disease. Recent findings showed the capacity of specific repetitive transcranial magnetic stimulation protocols to reinforce facilitatory processes within the motor cortex and to reduce the loss of muscle force during exercise. This approach might represent a way of access to central processes underlying muscle fatigue in motor neuron and neuromuscular disorders. PMID:23182631

  4. 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.

  5. Effects of High-Intensity Blood Flow Restriction Exercise on Muscle Fatigue

    PubMed Central

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

    2014-01-01

    Strength training combined with blood flow restriction (BFR) have been used to improve the levels of muscle adaptation. The aim of this paper was to investigate the acute effect of high intensity squats with and without blood flow restriction on muscular fatigue levels. Twelve athletes (aged 25.95 ± 0.84 years) were randomized into two groups: without Blood Flow Restriction (NFR, n = 6) and With Blood Flow Restriction (WFR, n = 6) that performed a series of free weight squats with 80% 1-RM until concentric failure. The strength of the quadriceps extensors was assessed in a maximum voluntary isometric contraction integrated to signals from the surface electromyogram. The average frequency showed significant reductions in the WFR group for the vastus lateralis and vastus medialis muscles, and intergroup only for the vastus medialis. In conclusion, a set of squats at high intensity with BFR could compromise muscle strength immediately after exercise, however, differences were not significant between groups. PMID:25114743

  6. 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.

  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. 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

  9. 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

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

    PubMed

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

    2015-01-01

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

  11. 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

  12. 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.

  13. 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.

  14. Strength improvement of knee extensor muscles in patients with chronic heart failure by neuromuscular electrical stimulation.

    PubMed

    Quittan, M; Sochor, A; Wiesinger, G F; Kollmitzer, J; Sturm, B; Pacher, R; Mayr, W

    1999-05-01

    Patients with severe chronic heart failure (CHF) suffer from marked weakness of skeletal muscles. Neuromuscular electrical stimulation (NMES) proved to be an alternative to active strength training. The objective of this study was to test the feasibility and effectiveness of NMES in patients with chronic heart failure. Seven patients (56.0 +/- 5.0 years, CHF for 20 +/- 4 months, left ventricular ejection fraction 20.1 +/- 10.0%) finished an 8 week course of NMES of the knee extensor muscles. The stimulator delivered biphasic, symmetric, constant voltage impulses of 0.7 ms pulse width with a frequency of 50 Hz, 2 s on and 6 s off. No adverse effects occurred. After the stimulation period, the isokinetic peak torque of the knee extensor muscles increased by 13% from 101.0 +/- 8.7 Nm to 113.5 +/- 7.2 Nm (p = 0.004). The maximal isometric strength increased by 20% from 294.3 +/- 19.6 N to 354.14 +/- 15.7 N (p = 0.04). This increased muscle strength could be maintained in a 20 min fatigue test indicating decreased muscle fatigue. These results demonstrate that NMES of skeletal muscles in patients with severe chronic heart failure is a promising method for strength training in this group of patients.

  15. 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

  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.

  17. The effect of leg muscle activation state and localized muscle fatigue on tibial response during impact.

    PubMed

    Holmes, Adriana M; Andrews, David M

    2006-11-01

    The purpose of this research was to examine the effects of voluntarily manipulating muscle activation and localized muscle fatigue on tibial response parameters, including peak tibial acceleration, time to peak tibial acceleration, and the acceleration slope, measured at the knee during unshod heel impacts. A human pendulum delivered consistent impacts to 15 female and 15 male subjects. The tibialis anterior and lateral gastrocnemius were examined using electromyography, thus allowing voluntary contraction to various activation states (baseline, 15%, 30%, 45%, and 60% of the maximum activation state) and assessing localized muscle fatigue. A skin-mounted uniaxial accelerometer, preloaded medial to the tibial tuberosity, allowed tibial response parameter determination. There were significant decreases in peak acceleration during tibialis anterior fatigue, compared to baseline and all other activation states. In females, increased time to peak acceleration and decreased acceleration slope occurred during fatigue compared to 30% and 45%, and compared to 15% through 60% of the maximum activation state, respectively. Slight peak acceleration and acceleration slope increases, and decreased time to peak acceleration as activation state increased during tibialis anterior testing, were noted. When examining the lateral gastrocnemius, the time to peak acceleration was significantly higher across gender in the middle activation states than at the baseline and fatigue states. The acceleration slope decreased at all activation states above baseline in females, and decreased at 60% of the maximum activation state in males compared to the baseline and fatigue states. Findings agree with localized muscle fatigue literature, suggesting that with fatigue there is decreased impact transmission, which may protect the leg. The relative effects of leg stiffness and ankle angle on tibial response need to be verified.

  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. 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).

  20. SIZE DEPENDENCE OF FLEXURAL STRENGTH AND FATIGUE STRENGTH OF PAVEMENT CONCRETE

    NASA Astrophysics Data System (ADS)

    Yoshimoto, Toru; Sato, Ryoichi

    The size effect on flexural fatigue strength of concrete was experime ntally investigated. For this purpose, specimens of two sizes were prepared: 150mm x 150mm x 530mm (span=450mm) and 200mm x 450mm x 1800mm (span=1350mm). The stress levels were set at 70%, 80% and 90% of the compressive strength. Experimental results showed that the number of loading cycles at failure increased with the enlargement of specimens. Based on a fracture mechanics approach, with a stress level of 70%, this dependence of flexural fatigue strength on size was explained by the difference in the stress distributions in the sections of small and large sized specimens. A te nsion softening stress region was formed in the section of the small specimen, whereas elastic stress was produced over the full section in the large specimen.

  1. Effects of Increased Muscle Strength and Muscle Mass on Endurance-Cycling Performance.

    PubMed

    Mujika, Iñigo; Rønnestad, Bent R; Martin, David T

    2016-04-01

    Despite early and ongoing debate among athletes, coaches, and sport scientists, it is likely that resistance training for endurance cyclists can be tolerated, promotes desired adaptations that support training, and can directly improve performance. Lower-body heavy strength training performed in addition to endurance-cycling training can improve both short- and long-term endurance performance. Strength-maintenance training is essential to retain strength gains during the competition season. Competitive female cyclists with greater lower-body lean mass (LBLM) tend to have ~4-9% higher maximum mean power per kg LBLM over 1 s to 10 min. Such relationships enable optimal body composition to be modeled. Resistance training off the bike may be particularly useful for modifying LBLM, whereas more cycling-specific training strategies like eccentric cycling and single-leg cycling with a counterweight have not been thoughtfully investigated in well-trained cyclists. Potential mechanisms for improved endurance include postponed activation of less efficient type II muscle fibers, conversion of type IIX fibers into more fatigue-resistant IIa fibers, and increased muscle mass and rate of force development.

  2. Effects of Increased Muscle Strength and Muscle Mass on Endurance-Cycling Performance.

    PubMed

    Mujika, Iñigo; Rønnestad, Bent R; Martin, David T

    2016-04-01

    Despite early and ongoing debate among athletes, coaches, and sport scientists, it is likely that resistance training for endurance cyclists can be tolerated, promotes desired adaptations that support training, and can directly improve performance. Lower-body heavy strength training performed in addition to endurance-cycling training can improve both short- and long-term endurance performance. Strength-maintenance training is essential to retain strength gains during the competition season. Competitive female cyclists with greater lower-body lean mass (LBLM) tend to have ~4-9% higher maximum mean power per kg LBLM over 1 s to 10 min. Such relationships enable optimal body composition to be modeled. Resistance training off the bike may be particularly useful for modifying LBLM, whereas more cycling-specific training strategies like eccentric cycling and single-leg cycling with a counterweight have not been thoughtfully investigated in well-trained cyclists. Potential mechanisms for improved endurance include postponed activation of less efficient type II muscle fibers, conversion of type IIX fibers into more fatigue-resistant IIa fibers, and increased muscle mass and rate of force development. PMID:27068517

  3. 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

  4. Effects of quadriceps muscle fatigue on stiff-knee gait in patients with hemiparesis.

    PubMed

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

    2014-01-01

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

  5. 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…

  6. Human forearm position sense after fatigue of elbow flexor muscles

    PubMed Central

    Walsh, L D; Hesse, C W; Morgan, D L; Proske, U

    2004-01-01

    After a period of eccentric exercise of elbow flexor muscles of one arm in young, adult human subjects, muscles became fatigued and damaged. Damage indicators were a fall in force, change in resting elbow angle and delayed onset of soreness. After the exercise, subjects were asked to match the forearm angle of one arm, whose position was set by the experimenter, with their other arm. Subjects matched the position of the unsupported reference arm, when this was unexercised, with a significantly more flexed position in their exercised indicator arm. Errors were in the opposite direction when the reference arm was exercised. The size of the errors correlated with the drop in force. Less consistent errors were observed when the reference arm was supported. A similar pattern of errors was seen after concentric exercise, which does not produce muscle damage. The data suggested that subjects were using as a position cue the perceived effort required to maintain a given forearm angle against the force of gravity. The fall in force from fatigue after exercise meant more effort was required to maintain a given position. That led to matching errors between the exercised and unexercised arms. It was concluded that while a role for muscle spindles in kinaesthesia cannot be excluded, detailed information about static limb position can be derived from the effort required to support the limb against the force of gravity. PMID:15181165

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

    PubMed

    Kodesh, Einat; Dar, Gali

    2015-01-01

    This study aimed to evaluate the effect of kinesiotape (KT) on dynamic stability following ankle muscle fatigue among individuals with chronic ankle instability (CAI). Twenty participants with CAI participated in the study. Participants were tested under three conditions: KT, non-elastic tape, and no tape pre- and post-fatigue of the ankle muscles. Ankle muscles fatigue was induced using an isokinetic apparatus, activity of the fibularis muscle was recorded using one-channel vibromyography (VMG), and dynamic balance and neuromuscular control were assessed using the Y-Balance Test. Following fatigue exercises, the VMG signal significantly decreased in all groups (p < 0.01), without differences between groups. No significant difference in dynamic balance test scores was found between the pre- and post-fatigue condition for each group and between groups. Our results demonstrate that KT had no significant effects on dynamic balance and muscle activity following ankle muscle fatigue among individuals with CAI. PMID:26279271

  8. 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.

  9. 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.

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

    PubMed

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

    2007-01-01

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

  11. 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.

  12. Fatigue crack initiation and strain-controlled fatigue of some high strength low alloy steels

    NASA Astrophysics Data System (ADS)

    Kim, Y. H.; Fine, M. E.

    1982-01-01

    Initiation and growth of fatigue microcracks were investigated in several Nb and V alloyed high strength low alloy steels, including conventional and dual phase microstructures. Fatigue microcracks initiated along prominent slip bands. Macrocracks formed by linking up of small microcracks. At low applied stress or strain, the number of cycles to crack initiation increased with the cyclic yield stress. Comparing the cyclic stress-strain curves to the monotonie stress-strain curves, cyclic hardening or softening occurred, depending upon strain amplitude. Plateau regions were observed in plots of cyclic stress amplitude vs cyclic plastic strain amplitude obtained by increasing the total strain amplitude in steps after 30 cycles at each step. In polycrystalline 0.03 pct Nb steel, the plateau region was identified with prominent slip band formation, as others have observed in single crystals of copper, C-doped iron, and other metals.

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

    PubMed

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

    2007-01-01

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

  14. Strength and fatigue of polyacid-modified restorative materials (compomers).

    PubMed

    Boberick, Ken G; McCool, John I; Baran, George R

    2002-06-01

    The purpose of this study was to compare the fatigue behavior of a hybrid composite, four compomers, and two viscous glass ionomers after short- and long-term soaking in distilled water. Bars with dimensions of 30 mm x 2 mm x 2 mm were formed in stainless steel molds, finished with 600 grit SiC, then soaked for either 24 h or one year, and tested in 3-point flexure at stressing rates between 0.001 and 2500 MPa s(-1). Data were plotted as fracture stress vs. stressing rate, and the exponent N in the power law for crack growth rate was computed from the slope of these plots. All compomer and resin composite materials tested exhibited subcritical crack growth (i.e. a reduction in strength with a decrease in stressing rate). Soaking lowered the slope for all materials, that is, increased the crack propagation rate. F2000 exhibited an increase in fracture strength while Hytac and Compoglass exhibited a decrease following long-term soaking in distilled water. Crack-growth exponents obtained from these fatigue data were used to estimate the stresses which would result in a five-year lifetime for these materials.

  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. 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

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

    PubMed

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

    2015-01-13

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

  18. 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.

  19. 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.

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

    PubMed Central

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

    2009-01-01

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

  1. Effect of polishing on cyclic fatigue strength of CAD/CAM ceramics.

    PubMed

    Nakazato, T; Takahashi, H; Yamamoto, M; Nishimura, F; Kurosaki, N

    1999-12-01

    The biaxial flexural strength and cyclic fatigue biaxial flexural strength of CAD/CAM ceramics polished with #220, 400, 600 and 1000 diamond pads were measured in an effort to determine the effect of surface roughness on fatigue behavior of dental ceramics. The surface roughness was improved after polishing with a smaller diamond grain pad. The flexural strengths of the specimens polished with #220, 400, 600 and 1000 diamond pad were 75.2, 76.6, 82.2, and 83.3 MPa, respectively; the fatigue flexural strength of those with #220, 400, 600 and 1000 were 53.0, 58.1, 60.0, and 61.5 MPa, respectively. Both the flexural and fatigue flexural strengths increased with improvement of surface profile. These results suggest the importance of polishing of dental ceramics for not only the static strength but also the cyclic fatigue strength.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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

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

    PubMed

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

    2004-09-01

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

  9. 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.

  10. 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.

  11. 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

  12. 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

  13. Muscle Damage and Its Relationship with Muscle Fatigue During a Half-Iron Triathlon

    PubMed Central

    Coso, Juan Del; González-Millán, Cristina; Salinero, Juan José; Abián-Vicén, Javier; Soriano, Lidón; Garde, Sergio; Pérez-González, Benito

    2012-01-01

    Background To investigate the cause/s of muscle fatigue experienced during a half-iron distance triathlon. Methodology/Principal Findings We recruited 25 trained triathletes (36±7 yr; 75.1±9.8 kg) for the study. Before and just after the race, jump height and leg muscle power output were measured during a countermovement jump on a force platform to determine leg muscle fatigue. Body weight, handgrip maximal force and blood and urine samples were also obtained before and after the race. Blood myoglobin and creatine kinase concentrations were determined as markers of muscle damage. Results Jump height (from 30.3±5.0 to 23.4±6.4 cm; P<0.05) and leg power output (from 25.6±2.9 to 20.7±4.6 W · kg−1; P<0.05) were significantly reduced after the race. However, handgrip maximal force was unaffected by the race (430±59 to 430±62 N). Mean dehydration after the race was 2.3±1.2% with high inter-individual variability in the responses. Blood myoglobin and creatine kinase concentration increased to 516±248 µg · L−1 and 442±204 U · L−1, respectively (P<0.05) after the race. Pre- to post-race jump change did not correlate with dehydration (r = 0.16; P>0.05) but significantly correlated with myoglobin concentration (r = 0.65; P<0.001) and creatine kinase concentration (r = 0.54; P<0.001). Conclusions/significance During a half-iron distance triathlon, the capacity of leg muscles to produce force was notably diminished while arm muscle force output remained unaffected. Leg muscle fatigue was correlated with blood markers of muscle damage suggesting that muscle breakdown is one of the most relevant sources of muscle fatigue during a triathlon. PMID:22900101

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  15. 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…

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

    PubMed

    Han, Jin Tae; Lee, Jung-Hoon

    2014-06-01

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

  17. 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.

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

    PubMed

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

    2016-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  20. The influence of strength-endurance training on the oxygenation of isometrically contracted forearm muscles.

    PubMed

    Usaj, Anton; Jereb, Blaz; Robi, Pritrznik; von Duvillard, Serge P

    2007-08-01

    Ice-climbers frequently use the squeezing of rubber rings for increasing their isometric strength-endurance in the forearm muscles. The aim of this study was to ascertain whether such training influences oxygenation and endurance of forearm muscles at higher as well as lower testing intensities. Fourteen healthy young ice-climbers were divided and randomized into two groups. Group A performed a specific ice-climbing test, an ice-axe-grasping (axe weight 750 g) until fatigue. Group B performed 150 N isometric hand-squeezing of dynamometer until fatigue. Both groups performed similar training of squeezing a rubber ring at 30% of Maximal Voluntary Contraction (MVC) for 6 weeks. The forearm oxygenation was assessed by relative saturation of oxygen (RSO(2)), total hemoglobin concentration (RTOTHb), the concentration of oxygenated hemoglobin (ROXYHb) and concentration of deoxygenated hemoglobin (RDEOXYHb). The results revealed that muscle strength-endurance training increased performance of forearm muscles during 150 N contraction with an accompanied increase in oxygenation of the exercising muscles. In contrast, the same training did not influence the performance of forearm muscles during ice-axe-grasping in spite of increased oxygenation. Muscle oxygenation during intense isometric contraction is low in spite of an increase observed in training. This may be due to oxygenation levels that were below the limit where oxygenation may influence the duration of the contraction. Increased oxygenation may have occurred due to an increased blood flow and perfusion through superficial muscles or layers may not have contributed to the generation of the force of the contraction, as would be the case in deeper muscle layers.

  1. [A study of mechanomyography analysis for muscle fatigue with Hilbert-Huang transform].

    PubMed

    Hu, Shuxian; Shi, Jun

    2011-04-01

    The mechanomyography (MMG) records and quantifies the low-frequency lateral oscillations of active muscle fibers. It can represent the mechanical characteristics of muscle activity. MMG has been used to evaluate muscle fatigue. Hilbert-Huang transform (HHT) is a time-frequency method with the feature of self-adaptation, and designed specifically for nonlinear and nonstationary signal analysis. In this study, MMG signal was recorded from biceps brachii during isometric fatigue contraction. HHT was used to calculate the difference between the maximum and minimum values of instantaneous frequency, named as the band ratio, to estimate muscle fatigue. The results showed that the band ratios were 0.431 +/- 0.607 and 0.286 +/- 0.218 after fatigue for the maximum voluntary contraction (MVC) of 50% and 70%, respectively. These indicated that the frequency declined after muscles fatigue.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  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. 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.

  8. 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

  9. Predictive value of strength loss as an indicator of muscle damage across multiple drop jumps.

    PubMed

    Skurvydas, Albertas; Brazaitis, Marius; Venckūnas, Tomas; Kamandulis, Sigitas

    2011-06-01

    The aim of the present study was to compare the time-course of indirect symptoms of exercise-induced muscle damage after 50 and 100 drop jumps. A high-force, low intensity exercise protocol was used to avoid discrepancies regarding metabolic fatigue immediately after exercise. Healthy untrained men performed 50 ("50 group", n = 13) or 100 ("100 group", n = 13) intermittent (30-s interval between each jump) drop jumps, respectively, from the height of 0.5 m with a counter-movement to a 90° knee flexion angle and immediate maximal rebound. Voluntary and electrically evoked knee extensor strength was assessed using an isokinetic dynamometer immediately before and at 2 min after exercise, as well as 3, 7, and 14 days after exercise. Creatine kinase (CK) activity and muscle soreness within 7 days after exercise were also determined. The results showed that the decrease in voluntary isometric and isokinetic torque as well as 100 Hz stimulation torque at the end of the 50 and 100 drop jumps was very similar, while substantial differences were found in low-frequency fatigue, shift in optimal knee joint angle, muscle soreness, and CK activity. In addition, there was slower muscle strength recovery after the 100 drop jumps. It is concluded that the predictive value of strength loss immediately after exercise as an indicator of muscle damage decreases as the jump number increases. Still, stimuli must be large enough for muscle torque to reach the reduction plateau. Therefore, magnitude of exercise becomes a major factor in accuracy of muscle damage predictions. PMID:21574783

  10. Citrulline malate limits increase in muscle fatigue induced by bacterial endotoxins.

    PubMed

    Goubel, F; Vanhoutte, C; Allaf, O; Verleye, M; Gillardin, J M

    1997-03-01

    Citrulline malate is known to improve performance in weakened muscles. The present experiment was designed to test the hypothesis that citrulline malate can limit the effect of endotoxins on muscle fatigability. Endotoxemia was induced in rats by injection of lipopolysaccharides from Klebsiella pneumoniae. Resistance to fatigue was quantified by measuring tension production during repetitive electrical stimulation of the isolated epitrochlearis muscle. Oral treatment by citrulline malate was found to increase resistance to fatigue in infected rats, whereas twitch tension was not modified. This demonstrates the efficacy of citrulline malate for limiting an increase in muscle fatigue elicited with bacterial endotoxins. PMID:9164703

  11. Self-regulatory strength depletion and muscle-endurance performance: a test of the limited-strength model in older adults.

    PubMed

    Bray, Steven R; Martin Ginis, Kathleen A; Woodgate, Jennifer

    2011-07-01

    Self-regulation consumes a form of strength or energy. The authors investigated aftereffects of self-regulation depletion on muscle-endurance performance in older adults. Participants (N = 61, mean age = 71) were randomized to a self-regulation-depletion or control group and completed 2 muscle-endurance performance tasks involving isometric handgrip squeezing that were separated by a cognitive-depletion task. The depletion group showed greater deterioration of muscle-endurance performance than controls, F(1, 59) = 7.31, p = .009. Results are comparable to those of younger adults in a similar study and support Baumeister et al.'s limited-strength model. Self-regulation may contribute to central-nervous-system fatigue; however, biological processes may allow aging muscle to offset depletion of self-regulatory resources affecting muscle-endurance performance.

  12. 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.

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

    PubMed

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

    2014-01-01

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

  14. Inspiratory muscle work in acute hypoxia influences locomotor muscle fatigue and exercise performance of healthy humans.

    PubMed

    Amann, Markus; Pegelow, David F; Jacques, Anthony J; Dempsey, Jerome A

    2007-11-01

    Our aim was to isolate the independent effects of 1) inspiratory muscle work (W(b)) and 2) arterial hypoxemia during heavy-intensity exercise in acute hypoxia on locomotor muscle fatigue. Eight cyclists exercised to exhaustion in hypoxia [inspired O(2) fraction (Fi(O(2))) = 0.15, arterial hemoglobin saturation (Sa(O(2))) = 81 +/- 1%; 8.6 +/- 0.5 min, 273 +/- 6 W; Hypoxia-control (Ctrl)] and at the same work rate and duration in normoxia (Sa(O(2)) = 95 +/- 1%; Normoxia-Ctrl). These trials were repeated, but with a 35-80% reduction in W(b) achieved via proportional assist ventilation (PAV). Quadriceps twitch force was assessed via magnetic femoral nerve stimulation before and 2 min after exercise. The isolated effects of W(b) in hypoxia on quadriceps fatigue, independent of reductions in Sa(O(2)), were revealed by comparing Hypoxia-Ctrl and Hypoxia-PAV at equal levels of Sa(O(2)) (P = 0.10). Immediately after hypoxic exercise potentiated twitch force of the quadriceps (Q(tw,pot)) decreased by 30 +/- 3% below preexercise baseline, and this reduction was attenuated by about one-third after PAV exercise (21 +/- 4%; P = 0.0007). This effect of W(b) on quadriceps fatigue occurred at exercise work rates during which, in normoxia, reducing W(b) had no significant effect on fatigue. The isolated effects of reduced Sa(O(2)) on quadriceps fatigue, independent of changes in W(b), were revealed by comparing Hypoxia-PAV and Normoxia-PAV at equal levels of W(b). Q(tw,pot) decreased by 15 +/- 2% below preexercise baseline after Normoxia-PAV, and this reduction was exacerbated by about one-third after Hypoxia-PAV (-22 +/- 3%; P = 0.034). We conclude that both arterial hypoxemia and W(b) contribute significantly to the rate of development of locomotor muscle fatigue during exercise in acute hypoxia; this occurs at work rates during which, in normoxia, W(b) has no effect on peripheral fatigue.

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

    PubMed

    Ma, Ming; Zhang, Shi-min

    2015-08-01

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

  16. 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.

  17. 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.

  18. 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

  19. Changes in the flexion-relaxation response induced by hip extensor and erector spinae muscle fatigue

    PubMed Central

    2010-01-01

    Background The flexion-relaxation phenomenon (FRP) is defined by reduced lumbar erector spinae (ES) muscle myoelectric activity during full trunk flexion. The objectives of this study were to quantify the effect of hip and back extensor muscle fatigue on FRP parameters and lumbopelvic kinematics. Methods Twenty-seven healthy adults performed flexion-extension tasks under 4 different experimental conditions: no fatigue/no load, no fatigue/load, fatigue/no load, and fatigue/load. Total flexion angle corresponding to the onset and cessation of myoelectric silence, hip flexion angle, lumbar flexion angle and maximal trunk flexion angle were compared across different experimental conditions by 2 × 2 (Load × Fatigue) repeated-measures ANOVA. Results The angle corresponding to the ES onset of myoelectric silence was reduced after the fatigue task, and loading the spine decreased the lumbar contribution to motion compared to the hip during both flexion and extension. A relative increment of lumbar spine motion compared to pelvic motion was also observed in fatigue conditions. Conclusions Previous results suggested that ES muscles, in a state of fatigue, are unable to provide sufficient segmental stabilization. The present findings indicate that, changes in lumbar-stabilizing mechanisms in the presence of muscle fatigue seem to be caused by modulation of lumbopelvic kinematics. PMID:20525336

  20. 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

  1. 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

    2014-07-14

    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.

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

    PubMed

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

    2014-09-01

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

  3. Evaluation of rotator cuff muscle strength in healthy individuals

    PubMed Central

    Cortez, Paulo José Oliveira; Tomazini, José Elias

    2015-01-01

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

  4. An autonomous wearable system for predicting and detecting localised muscle fatigue.

    PubMed

    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

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

    SciTech Connect

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

    1993-12-31

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

  6. The interaction between peripheral and central fatigue at different muscle temperatures during sustained isometric contractions.

    PubMed

    Lloyd, Alex; Hodder, Simon; Havenith, George

    2015-08-15

    Changes in central fatigue have been linked to active and passive changes in core temperature, as well as integration of sensory feedback from thermoreceptors in the skin. However, the effects of muscle temperature (Tm), and thereby metaboreceptor and local afferent nerve temperature, on central fatigue (measured using voluntary activation percentage) during sustained, high muscle fatigue exercise remain unexamined. In this study, we investigated Tm across the range of cold to hot, and its effect on voluntary activation percentage during sustained isometric contractions of the knee extensors. The results suggest that contrary to brief contractions, during a sustained fatiguing contraction Tm significantly (P < 0.001) influences force output (-0.7%/°C increase) and central fatigue (-0.5%/°C increase), showing a negative relationship across the Tm continuum in moderately trained individuals. The negative relationship between voluntary activation percentage and Tm indicates muscle temperature may influence central fatigue during sustained and high muscle fatigue exercise. On the basis of on an integrative analysis between the present data and previous literature, the impact of core and muscle temperature on voluntary muscle activation is estimated to show a ratio of 5.5 to 1, respectively. Accordingly, Tm could assume a secondary or tertiary role in the reduction of voluntary muscle activation when body temperature leaves a thermoneutral range.

  7. 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

  8. 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.

  9. 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

  10. [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

  11. Dynamic strength of the quadriceps muscle and sports activity.

    PubMed

    Hahn, T; Foldspang, A; Ingemann-Hansen, T

    1999-04-01

    The study objectives were to examine the dynamic strength of the quadriceps muscle in athletes, and investigate its association with participation in sport. The study comprised 168 active competitive non-pregnant athletes, aged 14-24 years. The dynamic strength of their quadriceps muscle was measured, and they answered a questionnaire about sports activity and occupation. The dynamic strength of the quadriceps muscle was significantly higher in men than in women, and was positively associated with body weight, years of jogging, years of soccer, and weekly hours of basketball. In conclusion, the dynamic strength of the quadriceps muscle seems to be associated with sports activity. The results suggest sport specific adaptation, which may reflect high levels of running and jumping activity.

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

    PubMed Central

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

    2014-01-01

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

  13. Measurement of muscle strength in the intensive care unit.

    PubMed

    Bittner, Edward A; Martyn, Jeevendra A; George, Edward; Frontera, Walter R; Eikermann, Matthias

    2009-10-01

    Traditional (indirect) techniques, such as electromyography and nerve conduction velocity measurement, do not reliably predict intensive care unit-acquired muscle weakness and its clinical consequences. Therefore, quantitative assessment of skeletal muscle force is important for diagnosis of intensive care unit-acquired motor dysfunction. There are a number of ways for assessing objectively muscle strength, which can be categorized as techniques that quantify maximum voluntary contraction force and those that assess evoked (stimulated) muscle force. Important factors that limit the repetitive evaluation of maximum voluntary contraction force in intensive care unit patients are learning effects, pain during muscular contraction, and alteration of consciousness.The selection of the appropriate muscle is crucial for making adequate predictions of a patient's outcome. The upper airway dilators are much more susceptible to a decrease in muscle strength than the diaphragm, and impairment of upper airway patency is a key mechanism of extubation failure in intensive care unit patients. Data suggest that the adductor pollicis muscle is an appropriate reference muscle to predict weakness of muscles that are typically affected by intensive care unit-acquired weakness, i.e., upper airway as well as extremity muscles. Stimulated (evoked) force of skeletal muscles, such as the adductor pollicis, can be assessed repetitively, independent of brain function, even in heavily sedated patients during high acuity of their disease. PMID:20046117

  14. Coherence and Sequential Information in Brain and Muscle Signals during Muscle Fatigue

    NASA Astrophysics Data System (ADS)

    Yao, Bing; Yue, Guang; Brown, Robert; Liu, Jingzhi

    2003-10-01

    In this study we investigated coherence and sequential orders among EEG signals of different cortical locations and between EEG and EMG signals. 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 EMG signals. Coherence among EEG signals of different channels and between EEG and EMG signals were computed. Phase spectrum was obtained by calculating the phase difference between any two signals. Time lag between two signals was estimated by measuring the slope of the phase in the frequency range of interest. The results showed that: (1) Coherence among EEG signals from different motor-related cortical areas showed slight decrease during muscle fatigue. (2) Coherence between EEG and EMG signals became lower when fatigue was more severe. (3) Fatigue-related changes in phase and time lag were observed, indicating fatigue effects on the speed of responses in the corticomuscular system.

  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. Changes in the flexion relaxation response induced by lumbar muscle fatigue

    PubMed Central

    Descarreaux, Martin; Lafond, Danik; Jeffrey-Gauthier, Renaud; Centomo, Hugo; Cantin, Vincent

    2008-01-01

    Background The flexion relaxation phenomenon (FRP) is an interesting model to study the modulation of lumbar stability. Previous investigations have explored the effect of load, angular velocity and posture on this particular response. However, the influence of muscular fatigue on FRP parameters has not been thoroughly examined. The objective of the study is to identify the effect of erector spinae (ES) muscle fatigue and spine loading on myoelectric silence onset and cessation in healthy individuals during a flexion-extension task. Methods Twenty healthy subjects participated in this study and performed blocks of 3 complete trunk flexions under 4 different experimental conditions: no fatigue/no load (1), no fatigue/load (2), fatigue/no load(3), and fatigue/load (4). Fatigue was induced according to the Sorenson protocol, and electromyographic (EMG) power spectral analysis confirmed that muscular fatigue was adequate in each subject. Trunk and pelvis angles and surface EMG of the ES L2 and L5 were recorded during a flexion-extension task. Trunk flexion angle corresponding to the onset and cessation of myoelectric silence was then compared across the different experimental conditions using 2 × 2 repeated-measures ANOVA. Results Onset of myoelectric silence during the flexion motion appeared earlier after the fatigue task. Additionally, the cessation of myoelectric silence was observed later during the extension after the fatigue task. Statistical analysis also yielded a main effect of load, indicating a persistence of ES myoelectric activity in flexion during the load condition. Conclusion The results of this study suggest that the presence of fatigue of the ES muscles modifies the FRP. Superficial back muscle fatigue seems to induce a shift in load-sharing towards passive stabilizing structures. The loss of muscle contribution together with or without laxity in the viscoelastic tissues may have a substantial impact on post fatigue stability. PMID:18218087

  17. EMG analysis of human inspiratory muscle resistance to fatigue during exercise.

    PubMed

    Segizbaeva, M O; Donina, Zh A; Timofeev, N N; Korolyov, Yu N; Golubev, V N; Aleksandrova, N P

    2013-01-01

    The aim of this study was to characterize the pattern of inspiratory muscle fatigue and to assess the resistance to fatigue of the diaphragm (D), parasternal (PS), sternocleidomastoid (SCM), and scalene (SC) muscles. Nine healthy, untrained male subjects participated in this study. Electromyographic activity (EMG) of D, PS, SCM, and SC was recorded during an incremental cycling test to exhaustion (workload of 1.0 W/kg with 0.5 W/kg increments every 5 min). The before-to-after exercise measurements of maximal inspiratory pressure (MIP) and EMG power spectrum changes were performed. The maximal inspiratory pressure declined about 8.1 % after exercise compared with that in the control condition (124.3 ± 8.5 vs. 114.2 ± 8.9 cmH2O) (P > 0.05), whereas the peak magnitude of integrated electrical activity of D, PS, SCM, and SC during the post-exercise Müller maneuver was significantly greater in all subjects than that pre-exercise. The extent of inspiratory muscles fatigue was evaluated by analysis of a shift in centroid frequency (fc) of EMG power spectrum. Exercise-induced D fatigue was present in three subjects and PS fatigue was another in two; whereas both D and PC fatigue were observed in four subjects. All subjects demonstrated a significant reduction in fc of SCM and SC. Results indicate that early signs of the fatiguing process might be detected in the D, PS, SCM, and SC muscles during exercise to exhaustion. Fatigue of either D or PS muscles develops selectively or together during exhaustive exercise, depending on the recruitment pattern of respiratory muscles. Accessory inspiratory muscles of the neck are less resistant to fatigue compared with the D and PS muscles.

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

    PubMed Central

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

    2015-01-01

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

  19. 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.

  20. 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

  1. 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…

  2. 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

  3. 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

  4. 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.

  5. The association between hip muscle cross-sectional area, muscle strength, and bone mineral density.

    PubMed

    Ahedi, Harbeer; Aitken, Dawn; Scott, David; Blizzard, Leigh; Cicuttini, Flavia; Jones, Graeme

    2014-07-01

    Studies examining the association between muscle size, muscle strength, and bone mineral density (BMD) are limited. Thus, this study aimed to describe the association between hip muscles cross-sectional area (CSA), muscle strength, and BMD of the hip and spine. A total of 321 subjects from the Tasmanian Older Adult Cohort study with a right hip MRI scan conducted between 2004 and 2006 were included. Hip muscles were measured on MR images by OsiriX (Geneva) software measuring maximum muscle CSA (cm(2)) of gluteus maximus, obturator externus, gemelli, quadratus femoris, piriformis, pectineus, sartorius, and iliopsoas. Dual-energy X-ray absorptiometry measured total hip, femoral neck, and spine BMD, and lower limb muscle strength was assessed by dynamometer. Muscle CSA of the hip flexors (pectineus, sartorius, and iliopsoas) and the hip rotators, obturator externus, and quadratus femoris were associated with both total hip and femoral neck BMD (all p < 0.05). The associations between CSA of pectineus and sartorius and BMD were stronger in women (p = 0.01-0.001) compared to men (p = 0.12-0.54). Additionally, only gemelli CSA was associated with BMD of the spine (p = 0.002). Gluteus maximus and piriformis showed no relationship with BMD. CSA of most hip muscles (except gluteus maximus and gemelli) were positively associated with leg strength (p = 0.02 to <0.001). Lastly, leg strength was weakly associated with BMD (p = 0.11-0.007). Hip muscle CSA, and to a lesser extent muscle strength, were positively associated with hip BMD. These data suggest that both higher muscle mass and strength may contribute to the maintenance of bone mass and prevention of disease progression in older adults. PMID:24829114

  6. Stature is an essential predictor of muscle strength in children

    PubMed Central

    2012-01-01

    Background Children with growth retardation or short stature generally present with lower strength than children of the same chronological age. The aim of the study was to establish if strength was dependent on variables related to stature in a population of healthy children and to propose practical predictive models for the muscle functions tested. A secondary aim was to test for any learning effects concerning strength measured at two successive visits by children. Methods Hand grip, elbow flexion and extension, and knee flexion and extension were measured by fixed dynamometry in 96 healthy subjects (47 girls and 49 boys, aged from 5 to 17 years). Results For the present paediatric population, muscle strength was highly dependent on height. Predictive models are proposed for the muscle functions tested. No learning effect between the first and the second visit was detected for any of the muscle functions tested. Conclusions This work shows that strength measurements using fixed dynamometry are reliable in children when using appropriate standardization of operating procedures. It underlines the particular relationship between body stature and muscle strength. Predictive equations may help with assessing the neuromuscular involvement in children suffering from various disorders, particularly those affecting their stature. PMID:22989265

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

    PubMed Central

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

    2016-01-01

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

  8. 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

  9. 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.

  10. 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.

  11. 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

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

    PubMed

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

    2014-03-01

    Fatigue in lower extremity musculature is associated with decline in postural stability, motor performance and alters normal walking patterns in human subjects. Automated recognition of lower extremity muscle fatigue condition may be advantageous in early detection of fall and injury risks. Supervised machine learning methods such as support vector machines (SVMs) have been previously used for classifying healthy and pathological gait patterns and also for separating old and young gait patterns. In this study we explore the classification potential of SVM in recognition of gait patterns utilizing an inertial measurement unit associated with lower extremity muscular fatigue. Both kinematic and kinetic gait patterns of 17 participants (29 ± 11 years) were recorded and analyzed in normal and fatigued state of walking. Lower extremities were fatigued by performance of a squatting exercise until the participants reached 60% of their baseline maximal voluntary exertion level. Feature selection methods were used to classify fatigue and no-fatigue conditions based on temporal and frequency information of the signals. Additionally, influences of three different kernel schemes (i.e., linear, polynomial, and radial basis function) were investigated for SVM classification. The results indicated that lower extremity muscle fatigue condition influenced gait and loading responses. In terms of the SVM classification results, an accuracy of 96% was reached in distinguishing the two gait patterns (fatigue and no-fatigue) within the same subject using the kinematic, time and frequency domain features. It is also found that linear kernel and RBF kernel were equally good to identify intra-individual fatigue characteristics. These results suggest that intra-subject fatigue classification using gait patterns from an inertial sensor holds considerable potential in identifying "at-risk" gait due to muscle fatigue. PMID:24081829

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

    PubMed Central

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

    2016-01-01

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

  14. 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

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

    PubMed

    Al Saif, Amer A; Al Senany, Samira

    2015-01-01

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

  16. Changes in joint coupling and variability during walking following tibialis posterior muscle fatigue

    PubMed Central

    2011-01-01

    Background The tibialis posterior muscle is believed to play a key role in controlling foot mechanics during the stance phase of gait. However, an experiment involving localised tibialis posterior muscle fatigue, and analysis of discrete rearfoot and forefoot kinematic variables, indicated that reduced force output of the tibialis posterior muscle did not alter rearfoot and forefoot motion during gait. Thus, to better understand how muscle fatigue affects foot kinematics and injury potential, the purpose of this study was to reanalyze the data and investigate shank, rearfoot and forefoot joint coupling and coupling variability during walking. Methods Twenty-nine participants underwent an exercise fatigue protocol aimed at reducing the force output of tibialis posterior. An eight camera motion analysis system was used to evaluate 3 D shank and foot joint coupling and coupling variability during treadmill walking both pre- and post-fatigue. Results The fatigue protocol was successful in reducing the maximal isometric force by over 30% and a concomitant increase in coupling motion of the shank in the transverse plane and forefoot in the sagittal and transverse planes relative to frontal plane motion of the rearfoot. In addition, an increase in joint coupling variability was measured between the shank and rearfoot and between the rearfoot and forefoot during the fatigue condition. Conclusions The reduced function of the tibialis posterior muscle following fatigue resulted in a disruption in typical shank and foot joint coupling patterns and an increased variability in joint coupling. These results could help explain tibialis posterior injury aetiology. PMID:21294889

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

    PubMed

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

    2016-10-01

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

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

    PubMed

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

    2016-10-01

    The study investigates whether tensiomyography (TMG) is sensitive to differentiate between strength and endurance athletes, and to monitor fatigue after either one week of intensive strength (ST) or endurance (END) training. Fourteen strength (24.1±2.0years) and eleven endurance athletes (25.5±4.8years) performed an intensive training period of 6days of ST or END, respectively. ST and END groups completed specific performance tests as well as TMG measurements of maximal radial deformation of the muscle belly (Dm), deformation time between 10% and 90% Dm (Tc), rate of deformation development until 10% Dm (V10) and 90% Dm (V90) before (baseline), after training period (post1), and after 72h of recovery (post2). Specific performance of both groups decreased from baseline to post1 (P<0.05) and returned to baseline values at post2 (P<0.05). The ST group showed higher countermovement jump (P<0.05) and shorter Tc (P<0.05) at baseline. After training, Dm, V10, and V90 were reduced in the ST (P<0.05) while TMG changes were less pronounced in the END. TMG could be a useful tool to differentiate between strength and endurance athletes, and to monitor fatigue and recovery especially in strength training. PMID:27317976

  19. 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.

  20. 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

  1. Muscle strength and hormonal levels in adolescents: gender related differences.

    PubMed

    Ramos, E; Frontera, W R; Llopart, A; Feliciano, D

    1998-11-01

    The purpose of the present investigation was to study muscle strength in adolescents and its relationship to serum levels of testosterone and growth hormone in both genders. Thirty active adolescents (15 boys; age range 11 -12 y/o) participated in the first study. Isokinetic muscle strength of the dominant knee extensors (KE) was determined at 0, 12, 20, 30, 120, 180 and 240 deg/sec using a Cybex 340 dynamometer. The assessment of pubertal status was accomplished using the criteria of Tanner. Serum levels of total testosterone (T) and growth hormone (GH) were determined using radioimmunoassay techniques. Boys had higher (p< 0.001) T levels but no differences in muscle strength were detected between genders. Fifty-seven additional subjects representing three age groups (11-12 y/o, n=18; 13-14, n=21; 17-18, n=18) participated in the second study. A significant increase in peak torque (absolute and corrected for body weight) with age was observed in both genders. There were no significant gender differences in strength for the two youngest age groups, but boys were stronger than girls in the oldest age group (group 3). Testosterone and GH levels increased with age in boys but not in girls. Gender related differences in T were found in groups 2 and 3. A positive correlation (r=0,64 boys; r=0.46 girls) between testosterone levels and absolute muscle strength was seen in both genders. Our results suggest that increases in anabolic hormones precede muscle strength gains in adolescent males. In addition, gender related differences in muscle strength during adolescents cannot be explained solely on the basis of difference in body size or T levels. PMID:9877143

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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

  11. 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

  12. 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.

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

    PubMed

    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

  14. 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

  15. Development on the Tensile Fatigue Test Apparatus and Strength Evaluation of Thin Metal Films

    NASA Astrophysics Data System (ADS)

    Fukushi, Miyuki; Miyata, Hiroshi; Murakami, Akira

    Recently, development of medical devices such as catheter and stent are advanced in the low invasion medical field. Considering the functions of human body are affected severely by the medical devices, the high strength reliability of devices must be secured. In these circumstances, the thin metal film, which has high reliability of strength, is useful structural material for further development of low invasion medical device. As the strength characteristics of a thin film depend on thickness and formation process of itself, there is little strength database concerning a thin metal film. In this study, a tensile fatigue testing apparatus with cyclic loading frequency up to 30Hz and maximum loading 8 N for the thin metal film has been developed, and thin rolled films Ti and SUS304 were evaluated on tensile and load-controlled fatigue strength. The static tensile tests give that both are also over the twice of the bulk material on the tensile strength, and the proof stress is high-strength with over 90% of tensile strength respectively. The fatigue test shows that Ti thin film has long life in comparison with the bulk material, however, the fatigue characteristic itself is similar like that of bulk material.

  16. Hamstring muscle strain recurrence and strength performance disorders.

    PubMed

    Croisier, Jean-Louis; Forthomme, Bénédicte; Namurois, Marie-Hélène; Vanderthommen, Marc; Crielaard, Jean-Michel

    2002-01-01

    We determined the frequency of strength disorders in 26 athletes with a history of hamstring muscle injury and recurrent strains and discomfort. We also assessed the effectiveness of rehabilitation to correct muscle performance. After concentric and eccentric isokinetic assessment, 18 athletes were found to have strength deficits, as determined by statistically selected cutoffs of peak torque, bilateral differences, and the flexors/quadriceps ratio. The discriminating character of the eccentric trial was demonstrated, combining a preferential eccentric peak torque deficit and a significant reduction of the mixed eccentric flexors/concentric quadriceps ratio. The athletes with muscle imbalances followed a rehabilitation program individually adapted from their strength profile. Treatment length was from 10 to 30 sessions and resulted in isokinetic parameter normalization in 17 of 18 subjects. Isokinetically corrected subjects were observed for 12 months after return to athletics. None sustained a clinically diagnosed hamstring muscle reinjury. Subjective intensity of pain and discomfort were significantly reduced, and they all returned to their prior level of competition. These results demonstrate that persistent muscle strength abnormalities may give rise to recurrent hamstring injuries and discomfort. An individualized rehabilitation program emphasizing eccentric training based on specific deficits contributes to a decrease in symptoms on return to sports.

  17. 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

  18. 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.

  19. 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.

  20. A study of optimal handle shape and muscle strength distribution on lower arm when holding a foil.

    PubMed

    Chang, Chih-Lin; Lin, Fang-Tsan; Li, Kai-Way; Jou, Yung-Tsan; Huang, Chuen-Der

    2009-04-01

    The strength of five working muscle groups of the lower arms of 8 male fencers, including adductor pollicis, extensor carpi radialis, flexor carpi radialis, extensor carpi ulnaris, and flexor carpi ulnaris, were examined during competition. Root mean square values of muscular electromyographic signals indicated that the shape of foil handles significantly influenced distribution of working strength of each muscle group. Use of the Pistol-Viscounti type of foil handle showed better distribution of strength among the 5 muscle groups than did other types of foils. Using the Pistol-Viscounti foil handle not only reduced muscular fatigue but also lessened cumulative trauma symptoms while holding a foil for a long duration. PMID:19544957

  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-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

  3. 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.

  4. 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

  5. Age at spinal cord injury determines muscle strength

    PubMed Central

    Thomas, Christine K.; Grumbles, Robert M.

    2014-01-01

    As individuals with spinal cord injury (SCI) age they report noticeable deficits in muscle strength, endurance and functional capacity when performing everyday tasks. These changes begin at ~45 years. Here we present a cross-sectional analysis of paralyzed thenar muscle and motor unit contractile properties in two datasets obtained from different subjects who sustained a cervical SCI at different ages (≤46 years) in relation to data from uninjured age-matched individuals. First, completely paralyzed thenar muscles were weaker when C6 SCI occurred at an older age. Muscles were also significantly weaker if the injury was closer to the thenar motor pools (C6 vs. C4). More muscles were strong (>50% uninjured) in those injured at a younger (≤25 years) vs. young age (>25 years), irrespective of SCI level. There was a reduction in motor unit numbers in all muscles tested. In each C6 SCI, only ~30 units survived vs. 144 units in uninjured subjects. Since intact axons only sprout 4–6 fold, the limits for muscle reinnervation have largely been met in these young individuals. Thus, any further reduction in motor unit numbers with time after these injuries will likely result in chronic denervation, and may explain the late-onset muscle weakness routinely described by people with SCI. In a second dataset, paralyzed thenar motor units were more fatigable than uninjured units. This gap widened with age and will reduce functional reserve. Force declines were not due to electromyographic decrements in either group so the site of failure was beyond excitation of the muscle membrane. Together, these results suggest that age at SCI is an important determinant of long-term muscle strength, and fatigability, both of which influence functional capacity. PMID:24478643

  6. 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. Bond and fatigue characteristics of high-strength cement-based composites

    SciTech Connect

    Chimamphant, S.D.

    1989-01-01

    The results of a series of tests on a variety of high strength cementitious composites yield a model from which an empirical equation of general normalized pull-out stress vs. pull-out displacement relationship is developed. A new variable named the Brittleness Index and is defined and used in the proposed equation. Additionally, the concept of maximum strain is used to predict the fatigue life of high strength concrete. Three sizes of deformed bars and two types of steel fiber with four different volume fractions were used to observe bond-slip and pull-out characteristics of high strength concrete. The results indicate that the maximum slippage of deformed bars is only about 10% of that observed in normal concrete. Consequently, the required development length may have to be longer for high strength concrete members as compared to normal concrete. For the fatigue characteristics study, standard 3 x 6 in. cylinders were tested at the rates of 6 and 12 Hz. in a closed-loop load-controlled system. The results show that as the compressive strength of the composites increases from 4000 to 11000 psi., the fatigue strength increases by 17 percents. The rate of loading does not significantly affect the S-N relationship, fatigue strength and fatigue limit of the high strength cement-based composites. The S-N curves of high strength concrete shows a faster decay rate than those of normal concrete. The maximum strain at any cycle under cyclic loading is always less than the maximum strain at failure under monotonic loading. Also observed is that the maximum strain-cycle relationship is linear. These results indicate that the design code for flexure of normal concrete cannot be applied to high strength concrete.

  8. 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.

  9. Stretch-shortening cycle: a powerful model to study normal and fatigued muscle.

    PubMed

    Komi, P V

    2000-10-01

    Stretch-shortening cycle (SSC) in human skeletal muscle gives unique possibilities to study normal and fatigued muscle function. The in vivo force measurement systems, buckle transducer technique and optic fiber technique, have revealed that, as compared to a pure concentric action, a non-fatiguing SSC exercise demonstrates considerable performance enhancement with increased force at a given shortening velocity. Characteristic to this phenomenon is very low EMG-activity in the concentric phase of the cycle, but a very pronounced contribution of the short-latency stretch-reflex component. This reflex contributes significantly to force generation during the transition (stretch-shortening) phase in SSC action such as hopping and running. The amplitude of the stretch reflex component - and the subsequent force enhancement - may vary according to the increased stretch-load but also to the level of fatigue. While moderate SSC fatigue may result in slight potentiation, the exhaustive SSC fatigue can dramatically reduce the same reflex contribution. SSC fatigue is a useful model to study the processes of reversible muscle damage and how they interact with muscle mechanics, joint and muscle stiffness. All these parameters and their reduction during SSC fatigue changes stiffness regulation through direct influences on muscle spindle (disfacilitation), and by activating III and IV afferent nerve endings (proprioseptic inhibition). The resulting reduced stretch reflex sensitivity and muscle stiffness deteriorate the force potentiation mechanisms. Recovery of these processes is long lasting and follows the bimodal trend of recovery. Direct mechanical disturbances in the sarcomere structural proteins, such as titin, may also occur as a result of an exhaustive SSC exercise bout.

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

    SciTech Connect

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

    1995-12-31

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

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

    PubMed

    Ahmed, Taghread

    2013-01-01

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

  12. 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.

  13. 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.

  14. 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.

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

    SciTech Connect

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

    2009-01-01

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

  16. 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.

  17. 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.

  18. Effects of moisture on apparent flexure strength and on torsion and flexure fatigue properties of graphite-epoxy composites

    NASA Technical Reports Server (NTRS)

    Sumsion, H. T.; Adamson, M. J.

    1979-01-01

    The effects of moisture and temperature on unidirectional and multi-ply laminates of T300/934 and AS/3501 graphite-epoxy systems were investigated. Properties studied were static flexure strength and flexure and torsion fatigue strengths at room temperature and at 74 C. Specimens with increased moisture content showed a reduced static flexure strength; water as the test environment had only a negligible influence. In flexure fatigue and torsion fatigue, the water environment caused somewhat reduced fatigue strengths at room temperature and significantly greater degradation in 74 C water. The failure mode in all cases was interlaminar delamination.

  19. Effects of Kinesiology Taping on Repositioning Error of the Knee Joint after Quadriceps Muscle Fatigue

    PubMed Central

    Han, Jin Tae; Lee, Jung-hoon

    2014-01-01

    [Purpose] The purpose of this study was to identify the effects of kinesiology taping on repositioning error of the knee joint after quadriceps muscle fatigue. [Subjects] Thirty healthy adults with no orthopaedic or neurological problems participated in this study. [Methods] The repositioning error of the knee joint was measured using a digital goniometer when the subjects extended their dominant-side knee to a random target angle (30°, 45°, or 60°) with their eyes closed, before and after a quadriceps muscle fatigue protocol, and after application of kinesiology tape. [Results] We found that repositioning errors of the dominant-side knee joint increased after quadriceps fatigue compared with no-fatigue conditions. However, kinesiology taping of the quadriceps muscle and patella after quadriceps fatigue significantly decreased repositioning errors of the knee joint. [Conclusion] These results suggest that quadriceps fatigue increases the repositioning error of the knee joint, whereas application of kinesiology tape decreases fatigue-induced joint repositioning error. PMID:25013297

  20. Muscle fatigue and contraction intensity modulates the complexity of surface electromyography.

    PubMed

    Cashaback, Joshua G A; Cluff, Tyler; Potvin, Jim R

    2013-02-01

    Nonlinear dynamical techniques offer a powerful approach for the investigation of physiological time series. Multiscale entropy analyses have shown that pathological and aging systems are less complex than healthy systems and this finding has been attributed to degraded physiological control processes. A similar phenomenon may arise during fatiguing muscle contractions where surface electromyography signals undergo temporal and spectral changes that arise from the impaired regulation of muscle force production. Here we examine the affect of fatigue and contraction intensity on the short and long-term complexity of biceps brachii surface electromyography. To investigate, we used an isometric muscle fatigue protocol (parsed into three windows) and three contraction intensities (% of maximal elbow joint moment: 40%, 70% and 100%). We found that fatigue reduced the short-term complexity of biceps brachii activity during the last third of the fatiguing contraction. We also found that the complexity of surface electromyography is dependent on contraction intensity. Our results show that multiscale entropy is sensitive to muscle fatigue and contraction intensity and we argue it is imperative that both factors be considered when evaluating the complexity of surface electromyography signals. Our data contribute to a converging body of evidence showing that multiscale entropy can quantify subtle information content in physiological time series.

  1. Instantaneous quantification of skeletal muscle activation, power production, and fatigue during cycle ergometry.

    PubMed

    Coelho, A C; Cannon, D T; Cao, R; Porszasz, J; Casaburi, R; Knorst, M M; Rossiter, H B

    2015-03-01

    A rapid switch from hyperbolic to isokinetic cycling allows the velocity-specific decline in maximal power to be measured, i.e., fatigue. We reasoned that, should the baseline relationship between isokinetic power (Piso) and electromyography (EMG) be reproducible, then contributions to fatigue may be isolated from 1) the decline in muscle activation (muscle activation fatigue); and 2) the decline in Piso at a given activation (muscle fatigue). We hypothesized that the EMG-Piso relationship is linear, velocity dependent, and reliable for instantaneous fatigue assessment at intolerance during and following whole body exercise. Healthy participants (n = 13) completed short (5 s) variable-effort isokinetic bouts at 50, 70, and 100 rpm to characterize baseline EMG-Piso. Repeated ramp incremental exercise tests were terminated with maximal isokinetic cycling (5 s) at 70 rpm. Individual baseline EMG-Piso relationships were linear (r(2) = 0.95 ± 0.04) and velocity dependent (analysis of covariance). Piso at intolerance (two legs, 335 ± 88 W) was ∼45% less than baseline [630 ± 156 W, confidence interval of the difference (CIDifference) 211, 380 W, P < 0.05]. Following intolerance, Piso recovered rapidly (F = 44.1; P < 0.05; η(2) = 0.79): power was reduced (P < 0.05) vs. baseline only at 0-min (CIDifference 80, 201 W) and 1-min recovery (CIDifference 13, 80 W). Activation fatigue and muscle fatigue (one leg) were 97 ± 55 and 60 ± 50 W, respectively. Mean bias ± limits of agreement for reproducibility were as follows: baseline Piso 1 ± 30 W; Piso at 0-min recovery 3 ± 35 W; and EMG at Piso 3 ± 14%. EMG power is linear, velocity dependent, and reproducible. Deviation from this relationship at the limit of tolerance can quantify the "activation" and "muscle" related components of fatigue during cycling.

  2. Preventive effects of stretching and stabilization exercises on muscle fatigue in mobile phone users

    PubMed Central

    Kim, Hye-Young; Yeun, Young-Ran; Kim, Sung-Joong

    2016-01-01

    [Purpose] The purpose of this study was to investigate the preventive effects of stretching and stabilization exercises on muscle fatigue of the neck erector spine and upper trapezius muscles. [Subjects and Methods] The subjects of this study were 26 healthy university students (14 males and 12 females). Each subject was assigned randomly to each of three study groups in order to prevent order effect. The three groups included in this study were the no-exercise, stretching exercise, and neck stabilization exercise groups. The median electromyographic frequency was used as a gauge of muscle fatigue. [Results] Decreased muscle fatigue was demonstrated by an increase in the median electromyographic frequency values in all the four muscle groups in the comparison between conditions 1 and 3. In particular, statistically significant differences were found between the two conditions in the right upper trapezius muscle group. [Conclusion] These findings suggest that the effect of stretching and stabilization exercises can reduce muscle fatigue in mobile phone users. PMID:27799686

  3. 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

  4. Effects of endurance and strength-directed electrical stimulation training on the performance and histological properties of paralyzed human muscle: a pilot study.

    PubMed

    Duffell, Lynsey D; Rowlerson, Anthea M; Donaldson, Nick De N; Harridge, Stephen D R; Newham, Di J

    2010-11-01

    Electrical stimulation (ES) improves muscle properties after spinal cord injury (SCI), but cycling power output (PO) remains low. We investigated the effect of endurance and strength ES training on these parameters. Assessments of quadriceps strength and fatigue resistance, cycling PO, and muscle biopsies were made in four well-trained SCI subjects (three cyclists and one rower) before and after additional weight training in the cyclists and once in the rower. Weight training improved muscle strength, but cycling PO was low in all subjects. There was no effect of training type on biopsy data. Biopsies showed non-specific signs of pathology, predominance of type IIa fibers, and uniform metabolic activity. Oxidative activity was low, as were capillary:fiber ratios in the cyclists. Cycling PO is limited by factors other than muscle strength. Future ES training studies should attempt to improve muscle oxidative capacity to optimize the potential benefits of ES exercise. PMID:20976779

  5. [Inspiratory muscle resistance to fatigue during exercise and simulated airway obstruction].

    PubMed

    Segizbaeva, M O; Aleksandrova, N P

    2014-01-01

    Respiratory muscle fatigue can develop during simulated airway obstruction. The aim of this study was to characterize the pattern of inspiratory muscle fatigue and to assess the resistance to fatigue of diaphragm (D), parasternal (PS), sternocleidomastoid (SM) and scalene (SC). 8 healthy untrained subjects participated in this study. To identify signs of inspiratory muscles fatigue development electromyographic activity of D, PS, SCM and SC was recorded during 5-min exercise with loaded breathing (40 cm H2O/L · s(-1)). The before-to-after exercise measurements of maximal inspiratory pressure (MIP) and EMG power spectrum changes were performed. Maximal inspiratory pressure declined about 12% after exercise test compared with control, whereas the peak magnitude of integrated electrical activity of D, PS, SCM and SC during post-exercise Muller's maneuver was significantly greater than in pre-exercise test in all subjects. The extent ofinspiratory muscles fatigue was evaluated by analysis of shift in centroid frequency (fc) of EMG power spectrum. All subjects demonstrated a significant reduction in fc of PS, SCM and SC.fc of D was not changed. Diaphragm is more resistantto fatigue during obstructive breathing compared with PS, SCM and SC. The data suggest that the reduction of maximum inspiratory pressure in chronic obstructive pulmonary disease also caused primarily by the weakening of the accessory muscles, while the weakness of the diaphragm may occur in the later stages of the disease. The functional failure of accessory muscles is an additional factor, which, along with the additional breathing resistance increases the load on the diaphragm, promoting its fatigue and reduced respiratory reserve.

  6. 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

  7. 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.

  8. Fatigue strength of cantilevered metal frameworks for tissue-integrated prostheses.

    PubMed

    Stewart, R B; Desjardins, R P; Laney, W R; Chao, E Y

    1992-07-01

    The design of the metal alloy framework in cantilevered sections of fixed tissue-integrated prostheses, is critical. Several cross-sectional designs have been advocated, including the popular L-shaped beam, which permits the economical use of space for tooth placement. The fatigue strengths of 15 L-shaped cantilevered framework sections of the same metal alloy were tested. The castings were divided into three groups of five according to vertical wall heights of 4, 5, and 6 mm. Fatigue durability of each sample was determined by counting the number of cycles of vertical forces required to induce catastrophic failure. Statistical analysis revealed significant differences between all three groups in the cycles counted at failure (p less than 0.0019). Fatigue strengths improved significantly with increasing vertical wall height of the L-shaped cantilevered frameworks. In addition, beam flexure was shown to be indirectly proportional to fatigue strength. Theoretical beam deflection was calculated and shown to correlate with the actual beam deflection during the testing. Theoretical calculations in static bending specific for a cross-sectional design may aid in the predictability of fatigue strength.

  9. 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.

  10. A real-time fatigue monitoring and analysis system for lower extremity muscles with cycling movement.

    PubMed

    Chen, Szi-Wen; Liaw, Jiunn-Woei; Chan, Hsiao-Lung; Chang, Ya-Ju; Ku, Chia-Hao

    2014-01-01

    A real-time muscle fatigue monitoring system was developed to quantitatively detect the muscle fatigue of subjects during cycling movement, where a fatigue progression measure (FPM) was built-in. During the cycling movement, the electromyogram (EMG) signals of the vastus lateralis and gastrocnemius muscles in one leg as well as cycling speed are synchronously measured in a real-time fashion. In addition, the heart rate (HR) and the Borg rating of perceived exertion scale value are recorded per minute. Using the EMG signals, the electrical activity and median frequency (MF) are calculated per cycle. Moreover, the updated FPM, based on the percentage of reduced MF counts during cycling movement, is calculated to measure the onset time and the progressive process of muscle fatigue. To demonstrate the performance of our system, five young healthy subjects were recruited. Each subject was asked to maintain a fixed speed of 60 RPM, as best he/she could, under a constant load during the pedaling. When the speed reached 20 RPM or the HR reached the maximal training HR, the experiment was then terminated immediately. The experimental results show that the proposed system may provide an on-line fatigue monitoring and analysis for the lower extremity muscles during cycling movement. PMID:25014101

  11. 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

  12. Acute effects of blood flow restriction on muscle activity and endurance during fatiguing dynamic knee extensions at low load.

    PubMed

    Wernbom, Mathias; Järrebring, Rickard; Andreasson, Mikael A; Augustsson, Jesper

    2009-11-01

    The purpose of this study was to investigate muscle activity and endurance during fatiguing low-intensity dynamic knee extension exercise with and without blood flow restriction. Eleven healthy subjects with strength training experience performed 3 sets of unilateral knee extensions with no relaxation between repetitions to concentric torque failure at 30% of the 1 repetition maximum. One leg was randomized to exercise with cuff occlusion and the other leg to exercise without occlusion. The muscle activity in the quadriceps was recorded with electromyography (EMG). Ratings of perceived exertion (RPE) and acute pain were collected immediately, and delayed onset muscle soreness (DOMS) was rated before and at 24, 48, and 72 hours after exercise. The results demonstrated high EMG levels in both experimental conditions, but there were no significant differences regarding maximal muscle activity, except for a higher EMG in the eccentric phase in set 3 for the nonoccluded condition (p = 0.005). Significantly more repetitions were performed with the nonoccluded leg in every set (p < 0.05). The RPE and acute pain ratings were similar, but DOMS was higher in the nonoccluded leg (p < 0.05). We conclude that blood flow restriction during low-intensity dynamic knee extension decreases the endurance but does not increase the maximum muscle activity compared with training without restriction when both regimes are performed to failure. The high levels of muscle activity suggest that performing low-load dynamic knee extensions in a no-relaxation manner may be a useful method in knee rehabilitation settings when large forces are contraindicated. However, similarly to fatiguing blood flow restricted exercise, this method is associated with ischemic muscle pain, and thus its applications may be limited to highly motivated individuals.

  13. 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.

  14. 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

  15. 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

  16. Strength and fatigue performance versus filler fraction of different types of direct dental restoratives.

    PubMed

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

    2006-01-01

    The aim of this study was to evaluate the mechanical properties, such as Young's moduli, fracture strengths (FS), and flexural fatigue limits of todays resin composite dental restoratives. All materials have been subdivided into flowable, aesthetic hybrid and nano-filled hybrid composites as marketed by dental manufacturers and analyzed in terms of the actual filler configurations. Specimen bars have been manufactured in reference to ISO 4049 standard, light-cured for 20 s, and stored in distilled water before testing. The elastic moduli (EM), FS, and flexural fatigue limits (FFL) were measured after 14 days storage by using the four-point bending test. The FFL was determined for 10(4) cycles. The fatigue data were analyzed by using the "staircase" approach and statistically treated by ANOVA analysis. Flowable materials with a reduced filler content exhibited the lowest Young's moduli, compared with those measured for higher filled materials. A linear relationship has been found between elastic moduli and filler loading (r(2) = 0.798). Correlations of FS and fatigue data to different filler fractions could not be proved. FS ranged between 61.3 and 124.9 MPa. After 10(4) cycles of fatigue loading, the FS suffered from a decrease between 45.2 and 61.7%. However, materials providing high initial strengths do not obviously reveal the best fatigue resistance. A marketing-based grouping of direct restorative materials has no meaning toward laboratory testing of mechanical properties.

  17. Damage formation, fatigue behavior and strength properties of ZrO2-based ceramics

    NASA Astrophysics Data System (ADS)

    Kozulin, A. A.; Narikovich, A. S.; Kulkov, S. N.; Leitsin, V. N.; Kulkov, S. S.

    2016-08-01

    It is suggested that a non-destructive testing technique using a three-dimensional X-ray tomography be applied to detecting internal structural defects and monitoring damage formation in a ceramic composite structure subjected to a bending load. Three-point bending tests are used to investigate the fatigue behavior and mechanical and physical properties of medical-grade ZrO2-based ceramics. The bending strength and flexural modulus are derived under static conditions at a loading rate of 2 mm/min. The fatigue strength and fatigue limit under dynamic loading are investigated at a frequency of 10 Hz in three stress ranges: 0.91-0.98, 0.8-0.83, and 0.73-0.77 MPa of the static bending strength. The average values of the bending strength and flexural modulus of sintered specimens are 43 MPa and 22 GPa, respectively. The mechanical properties of the ceramics are found to be similar to those of bone tissues. The testing results lead us to conclude that the fatigue limit obtained from 105 stress cycles is in the range 33-34 MPa, i.e. it accounts for about 75% of the static bending strength for the test material.

  18. Changes in force and intracellular metabolites during fatigue of human skeletal muscle.

    PubMed Central

    Cady, E B; Jones, D A; Lynn, J; Newham, D J

    1989-01-01

    1. The relationship between intracellular metabolites and the generation of force during fatigue has been examined in the first dorsal interosseous muscle of the hand. With the arm made ischaemic, the muscle was fatigued by three bouts of maximal voluntary contraction, leaving approximately three minutes ischaemic rest between contractions. During one series of experiments intracellular phosphorus metabolites were measured by nuclear magnetic resonance during the intervals between the fatiguing contractions: in the second series contractile properties were tested with brief electrical stimulation during the rest intervals. 2. The relationships between loss of force and change in metabolite concentrations obtained with four normal subjects were compared with those from one subject with myophosphorylase deficiency (MPD) who could not utilize muscle glycogen and therefore produced no hydrogen ion from glycolysis during exercise. 3. For both the MPD and normal subjects the relationship between relative force loss and inorganic phosphate (Pi) concentration was curvilinear, force changing little in the early stages of the contraction when the intracellular Pi was accumulating rapidly but falling faster when the Pi was above 25 mM and increasing relatively slowly. 4. In the normal subjects intracellular pH fell from a mean of 7.03 +/- 0.01 (mean +/- S.E. of mean, n = 19) in the fresh muscle to 6.51 +/- 0.02 at the end of the fatiguing exercise; force, as a percentage of the initial value, fell in proportion to the increase in H+ concentration. In the MPD subject pH did not change and force loss was therefore independent of H+ accumulation. In the normal subjects the force of the fatiguing muscle showed an approximately linear relationship with the concentration of the monobasic form of inorganic phosphate. However, the MPD subject showed a quite different relationship, with force loss being much greater for a given concentration of monobasic phosphate. This result

  19. 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

  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. 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.

  2. 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

  3. 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).

  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. 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.

  6. Effects of successive judo matches on fatigue and muscle damage markers.

    PubMed

    Detanico, Daniele; Dal Pupo, Juliano; Franchini, Emerson; Dos Santos, Saray G

    2015-04-01

    This study aimed to investigate the acute effects of simulated judo matches on fatigue and muscle damage markers. Twenty male judo athletes participated in this study. The athletes performed three 5-minute judo matches separated by 15 minutes of passive rest between each match. The following measurements were performed before and after each match: shoulder external/internal rotation isokinetic torque and countermovement jump (CMJ). Blood samples were taken before the first match and after the third match for serum creatine kinase (CK) and lactate dehydrogenase (LDH) analysis. T-tests for dependent samples and analysis of variance for repeated measures were used to compare the variables over the time; the level of significance was set at 0.05. An overall effect of the successive matches on shoulder internal (PTIN) and external (PTEX) rotation peak torque and CMJ performance was observed. PTIN and PTEX showed significant decreases in postmatch 2 and postmatch 3 when compared with the baseline (p < 0.01). Also, CMJ height declined in postmatch 2 and postmatch 3 (p < 0.01) when compared with the baseline. Serum CK and LDH activity increased significantly after the third match (p < 0.01). It was concluded that 3 successive judo matches induced a decline of peak torque and muscle power in the upper and lower limbs, respectively, and also provoked an increase of muscle damage markers. These findings may provide important knowledge for coaches and physical trainers to improve judo-specific strength training in both the upper and lower limbs. PMID:25426512

  7. Age-Related Loss of Muscle Mass and Strength

    PubMed Central

    Goldspink, Geoffrey

    2012-01-01

    Age-related muscle wasting and increased frailty are major socioeconomic as well as medical problems. In the quest to extend quality of life it is important to increase the strength of elderly people sufficiently so they can carry out everyday tasks and to prevent them falling and breaking bones that are brittle due to osteoporosis. Muscles generate the mechanical strain that contributes to the maintenance of other musculoskeletal tissues, and a vicious circle is established as muscle loss results in bone loss and weakening of tendons. Molecular and proteomic approaches now provide strategies for preventing age-related muscle wasting. Here, attention is paid to the role of the GH/IGF-1 axis and the special role of the IGFI-Ec (mechano growth factor/MGF) which is derived from the IGF-I gene by alternative splicing. During aging MGF levels decline but when administered MGF activates the muscle satellite (stem) cells that “kick start” local muscle repair and induces hypertrophy. PMID:22506111

  8. Associations between personality traits, physical activity level, and muscle strength.

    PubMed

    Tolea, Magdalena I; Terracciano, Antonio; Simonsick, Eleanor M; Metter, E Jeffrey; Costa, Paul T; Ferrucci, Luigi

    2012-06-01

    Associations among personality as measured by the Five Factor Model, physical activity, and muscle strength were assessed using data from the Baltimore Longitudinal Study of Aging (N = 1220, age: mean = 58, SD = 16). General linear modeling with adjustment for age, sex, race, and body mass index, and bootstrapping for mediation were used. We found neuroticism and most of its facets to negatively correlate with strength. The extraversion domain and its facets of warmth, activity, and positive-emotions were positively correlated with strength, independent of covariates. Mediation analysis results suggest that these associations are partly explained by physical activity level. Findings extend the evidence of an association between personality and physical function to its strength component and indicate health behavior as an important pathway. PMID:23966753

  9. Associations between personality traits, physical activity level, and muscle strength.

    PubMed

    Tolea, Magdalena I; Terracciano, Antonio; Simonsick, Eleanor M; Metter, E Jeffrey; Costa, Paul T; Ferrucci, Luigi

    2012-06-01

    Associations among personality as measured by the Five Factor Model, physical activity, and muscle strength were assessed using data from the Baltimore Longitudinal Study of Aging (N = 1220, age: mean = 58, SD = 16). General linear modeling with adjustment for age, sex, race, and body mass index, and bootstrapping for mediation were used. We found neuroticism and most of its facets to negatively correlate with strength. The extraversion domain and its facets of warmth, activity, and positive-emotions were positively correlated with strength, independent of covariates. Mediation analysis results suggest that these associations are partly explained by physical activity level. Findings extend the evidence of an association between personality and physical function to its strength component and indicate health behavior as an important pathway.

  10. 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.

  11. 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…

  12. 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.

  13. 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

  14. 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

  15. 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

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

    PubMed

    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.

  17. Low-intensity electrical muscle stimulation induces significant increases in muscle strength and cardiorespiratory fitness.

    PubMed

    Miyamoto, Toshiaki; Kamada, Hiroyuki; Tamaki, Akira; Moritani, Toshio

    2016-11-01

    The aim of this study was to investigate the effect of low-intensity exercise training using belt electrode skeletal muscle electrical stimulation on muscle strength and cardiorespiratory fitness in healthy subjects. Nineteen healthy subjects were allocated into control or intervention groups; in both groups the participants kept regular physical activity while the intervention group underwent 30 min B-SES training at 3-4 METs for four weeks. Knee extensor muscle strength and cardiorespiratory endurance during incremental exercise test were measured at baseline and after four weeks for all participants. The relative change of knee extensor muscle strength in the intervention group was significantly higher than control group (p < .05). Also, oxygen uptake at ventilator threshold and peak oxygen uptake during incremental exercise test significantly increased in the intervention group when compared with control group (p < .05). This study showed that prolonged low-intensity B-SES training resulted in significant increases in muscle strength and cardiorespiratory fitness in healthy subjects. Our present work suggested that B-SES training could assist patients who might have difficulty performing adequate voluntary exercise because of excessive obesity, orthopaedic problems and chronic diseases such as cardiovascular disease and type 2 diabetes. An intervention study conducted for such patients is strongly recommended.

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

    PubMed Central

    Callahan, Damien M.

    2011-01-01

    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

  19. 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…

  20. 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

  1. Proprioception and Neuromuscular Control of the Shoulder After Muscle Fatigue

    PubMed Central

    Myers, Joseph B.; Guskiewicz, Kevin M.; Schneider, Robert A.; Prentice, William E.

    1999-01-01

    Objective: To examine the effects of fatigue on proprioception and neuromuscular control of the shoulder. Design and Setting: Subjects were randomly assigned to either an experimental group or control group. Subjects were tested using either the active angle-reproduction or the single- arm dynamic stability test. The subjects were then fatigued using a dynamometer performing continuous, concentric rotation exercises of the shoulder. Once fatigued, the subjects were posttested using the same test. One week later, the subjects returned and were pretested, fatigued, and posttested using the other test. Subjects: Thirty-two college-age (18 to 25 years) subjects (16 males, 16 females) with no history of glenohumeral instability or upper extremity injury volunteered for this study. Measurements: Absolute angular error was measured using an electrogoniometer present within the isokinetic dynamometer, while sway velocity was measured using a force-plate system. Results: Repeated-measures analysis of variance revealed a significant difference between the pretest and posttest values for absolute angular error in the experimental group, whereas no significant difference was revealed between pretest and posttest sway velocity for either the control or experimental group. Conclusions: Fatigue of the internal and external rotators of the shoulder decreased proprioception of the shoulder, while having no significant effect on neuromuscular control. ImagesFigure 1.Figure 2.Figure 3. PMID:16558590

  2. 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.

  3. Ankle muscle strength influence on muscle activation during dynamic and static ankle training modalities.

    PubMed

    Lucas-Cuevas, Angel Gabriel; Baltich, Jennifer; Enders, Hendrik; Nigg, Sandro; Nigg, Benno

    2016-01-01

    Muscle weakness is considered a risk factor for ankle injury. Balance training and barefoot running have been used in an attempt to strengthen the muscles crossing the ankle. It is expected that training tasks that successfully strengthen the ankle would elicit increased muscular activity. However, it is unknown how an individual's ankle strength will influence the muscle activity used during a given task. Twenty-six participants performed dynamic (shod, barefoot running) and static tasks (squat on ground, squat on ®Bosu Ball) believed to strengthen the muscles surrounding the ankle. Electromyographic signals of the tibialis anterior, peroneus longus, gastrocnemius lateralis (GL) and gastrocnemius medialis (GM) were recorded and analysed using a non-linearly scaled wavelet analysis. Participants were divided into a strong group and a weak group according to their isometric plantar-flexion torque. The weak group required more relative GL and GM muscle activity during each training task compared to the strong group. No difference was observed between shod and barefoot running. There was a significant effect of training task on muscle activation level for the weak group. Differences in ankle strength had a significant impact on muscle activation.

  4. 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

  5. Evaluation of the strength and creep-fatigue behavior of hot isostatically pressed silicon nitride

    SciTech Connect

    Ferber, M.K.; Jenkins, M.G. )

    1992-09-01

    This paper reports that the strength of a commerically available hot isostatically pressed silicon nitride was measured as a function of temperature. To evaluate long-term mechanical reliability of this material, the tensile creep and fatigue behavior was measured at 1150[degrees], 1260[degrees], and 1370[degrees]C. The stress and temperature sensitivities of the secondary (or minimum) creep strain rate were used to estimate the stress exponent and activation energy associated with the dominant creep mechanism. The fatigue characteristics were evaluated by allowing individual creep tests to continue until specimen failure. The applicability of the four-point load geometry to the study of strength and creep behavior was also determined by conducting a limited number of flexural creep tests. The tensile fatigue data revealed two distinct failure mechanisms. At 1150[degrees]C, failure was controlled by a slow crack growth mechanism. At 1260[degrees] and 1370[degrees]C, the accumulation of creep damage in the form of grain boundary cavities and cracks dominated the fatigue behavior. In this temperature regime, the fatigue life was controlled by the secondary (or minimum) creep strain rate in accordance with the Monkman-Grant relation.

  6. Impaired mitochondrial respiration and decreased fatigue resistance followed by severe muscle weakness in skeletal muscle of mitochondrial DNA mutator mice.

    PubMed

    Yamada, Takashi; Ivarsson, Niklas; Hernández, Andrés; Fahlström, Andreas; Cheng, Arthur J; Zhang, Shi-Jin; Bruton, Joseph D; Ulfhake, Brun; Westerblad, Håkan

    2012-12-01

    Mitochondrial dysfunction can drastically impair muscle function, with weakness and exercise intolerance as key symptoms. Here we examine the time course of development of muscle dysfunction in a mouse model of premature ageing induced by defective proofreading function of mitochondrial DNA (mtDNA) polymerase (mtDNA mutator mouse). Isolated fast-twitch muscles and single muscle fibres from young (3-5 months) and end-stage (11 months) mtDNA mutator mice were compared to age-matched control mice. Force and free myoplasmic [Ca(2+)] ([Ca(2+)](i)) were measured under resting conditions and during fatigue induced by repeated tetani. Muscles of young mtDNA mutator mice displayed no weakness in the rested state, but had lower force and [Ca(2+)](i) than control mice during induction of fatigue. Muscles of young mtDNA mutator mice showed decreased activities of citrate synthase and β-hydroxyacyl-coenzyme A dehydrogenase, reduced expression of cytochrome c oxidase, and decreased expression of triggers of mitochondrial biogenesis (PGC-1α, PPARα, AMPK). Muscles from end-stage mtDNA mutator mice showed weakness under resting conditions with markedly decreased tetanic [Ca(2+)](i), force per cross-sectional area and protein expression of the sarcoplasmic reticulum Ca(2+) pump (SERCA1). In conclusion, fast-twitch muscles of prematurely ageing mtDNA mutator mice display a sequence of deleterious mitochondrial-to-nucleus signalling with an initial decrease in oxidative capacity, which was not counteracted by activation of signalling to increase mitochondrial biogenesis. This was followed by severe muscle weakness in the end stage. These results have implication for normal ageing and suggest that decreased mitochondrial oxidative capacity due to a sedentary lifestyle may predispose towards muscle weakness developing later in life.

  7. Fatigue

    MedlinePlus

    ... to help you find out what's causing your fatigue and recommend ways to relieve it. Fatigue itself is not a disease. Medical problems, treatments, and personal habits can add to fatigue. These include Taking certain medicines, such as antidepressants, ...

  8. Upper body muscle strength and batting performance in cricket batsmen.

    PubMed

    Taliep, Mogammad S; Prim, Sebastian K; Gray, Janine

    2010-12-01

    The aim of this study was to determine if upper body muscle strength (as measured by the 1 repetition maximum bench press) was associated with cricket batting performance. Cricket batting performance was defined by the maximum hitting distance during a batting task and batting average and strike rate during 1-Day and Twenty/20 (T/20) matches. Eighteen, provincial level, elite cricket batsmen participated in the study. Upper body muscle strength was found to be positively correlated with maximum hitting distance (p = 0.0052). There were no significant correlations between upper body strength, batting average, and strike rate for both the 1-Day and T/20 matches. The results of this study have implications for coaches choosing a particular batting line-up. Batsmen who have stronger upper bodies could be favored to bat when a match situation requires them to hit powerful strokes resulting in boundaries. However, coaches cannot use upper body strength as a predictor of overall batting performance in 1-Day or T/20 matches.

  9. Central fatigue contributes to the greater reductions in explosive than maximal strength with high-intensity fatigue.

    PubMed

    Buckthorpe, Matthew; Pain, Matthew T G; Folland, Jonathan P

    2014-07-01

    The study aimed to assess the influence of fatigue induced by repeated high-force explosive contractions on explosive and maximal isometric strength of the human knee extensors and to examine the neural and contractile mechanisms for the expected decrement. Eleven healthy untrained males completed 10 sets of voluntary maximal explosive contractions (five times 3 s, interspersed with 2 s rest). Sets were separated by 5 s, during which supramaximal twitch and octet contractions [eight pulses at 300 Hz that elicit the contractile peak rate of force development (pRFD)] were evoked. Explosive force, at specific time points, and pRFD were assessed for voluntary and evoked efforts, expressed in absolute terms and normalized to maximal/peak force. Maximal voluntary contraction force (MVCF) and peak evoked forces were also determined. Surface EMG amplitude was measured from three superficial agonists and normalized to maximal compound action potential area. By set 10, explosive force (47-52%, P < 0.001) and MVCF (42%, P < 0.001) had declined markedly. Explosive force declined more rapidly than MVCF, with lower normalized explosive force at 50 ms (29%, P = 0.038) that resulted in reduced normalized explosive force from 0 to 150 ms (11-29%, P ≤ 0.038). Neural efficacy declined by 34%, whilst there was a 15-28% reduction in quadriceps EMG amplitude during voluntary efforts (all P ≤ 0.03). There was demonstrable contractile fatigue (pRFD: octet, 27%; twitch, 66%; both P < 0.001). Fatigue reduced normalized pRFD for the twitch (21%, P = 0.001) but not the octet (P = 0.803). Fatigue exerted a more rapid and pronounced effect on explosive force than on MVCF, particularly during the initial 50 ms of contraction, which may explain the greater incidence of injuries associated with fatigue. Both neural and contractile fatigue mechanisms appeared to contribute to impaired explosive voluntary performance.

  10. Degradation in the fatigue strength of dentin by diamond bur preparations: Importance of cutting direction.

    PubMed

    Majd, B; Majd, H; Porter, J A; Romberg, E; Arola, D

    2016-01-01

    The objectives of this investigation were to evaluate the degradation in fatigue strength of dentin by diamond bur preparations and to identify the importance of cutting direction. Three groups of coronal dentin specimens were prepared from unrestored third molars, including a flaw free "control," and two groups that received a diamond bur cutting treatment performed parallel or perpendicular to the specimen length. The specimens were subjected to static or cyclic flexural loading to failure and the results were compared with data for carbide bur cutting. Under static loading diamond bur cutting resulted in significantly lower flexure strength (p ≤ 0.05) than the control for both cutting directions (from 154 to ∼124 MPa). However, there was no significant difference in the strength between the control and carbide bur treated specimens. Similarly, the fatigue strength of the diamond bur treated specimens was significantly lower (p ≤ 0.0001) than that of the control for both cutting directions. Cutting in the perpendicular direction resulted in nearly 60% reduction to the endurance limit (from 44 to 19 MPa). Based on the results, diamond bur cutting of cavity preparations causes a reduction in the fatigue strength of dentin, regardless of the cutting direction. To maintain the durability of dentin, cavity preparations introduced using diamond burs must be performed with appropriate cutting direction and followed by a finishing pass.

  11. 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.

  12. Evaluation of weldment creep and fatigue strength-reduction factors for elevated-temperature design

    SciTech Connect

    Corum, J.M.

    1989-01-01

    New explicit weldment strength criteria in the form of creep and fatigue strength-reduction factors were recently introduced into the American Society of Mechanical Engineers Code Case N-47, which governs the design of elevated-temperature nuclear plants components in the United States. This paper provides some of the background and logic for these factors and their use, and it describes the results of a series of long-term, confirmatory, creep-rupture and fatigue tests of simple welded structures. The structures (welded plates and tubes) were made of 316 stainless steel base metal and 16-8-2 weld filler metal. Overall, the results provide further substantiation of the validity of the strength-reduction factor approach for ensuring adequate life in elevated-temperature nuclear component weldments. 16 refs., 7 figs.

  13. 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.

  14. 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…

  15. 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.

  16. 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.

  17. 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

  18. Respiratory muscle strength in the physically active elderly.

    PubMed

    Summerhill, Eleanor M; Angov, Nadia; Garber, Carol; McCool, F Dennis

    2007-12-01

    Advancing age is associated with a decline in the strength of the skeletal muscles, including those of respiration. Respiratory muscles can be strengthened with nonrespiratory activities. We therefore hypothesized that regular exercise in the elderly would attenuate this age-related decline in respiratory muscle strength. Twenty-four healthy subjects older than 65 years were recruited (11 males and 13 females). A comprehensive physical activity survey was administered, and subjects were categorized as active (n = 12) or inactive (n = 12). Each subject underwent testing of maximum inspiratory and expiratory pressures (PI(max) and PE(max)). Diaphragmatic thickness (tdi) was measured via two-dimensional B-mode ultrasound. There were no significant differences between the active and inactive groups with respect to age (75 vs. 73 years) or body weight (69.1vs. 69.9 kg). There were more women (9) than men (3) in the inactive group. Diaphragm thickness was greater in the active group (0.31 +/- 0.06 cm vs. 0.25 +/- 0.04 cm; p = 0.011). PE(max) and PI(max) were also greater in the active group (130 +/- 44 cm H(2)O vs. 80 +/- 24 cm H(2)O; p = 0.002; and 99 +/- 32 cm H(2)O vs. 75 +/- 14 cm H(2)O; p = 0.03). There was a positive association between PI(max )and tdi (r = 0.43, p = 0.03). Regular exercise was positively associated with diaphragm muscle thickness in this cohort. As PE(max) was higher in the active group, we postulate that recruitment of the diaphragm and abdominal muscles during nonrespiratory activities may be the source of this training effect. PMID:17917778

  19. Fatigue-related electromyographic coherence and phase synchronization analysis between antagonistic elbow muscles.

    PubMed

    Wang, Lejun; Lu, Aiyun; Zhang, Shengnian; Niu, Wenxin; Zheng, Fanhui; Gong, Mingxin

    2015-03-01

    The aim of this study was to examine coherence and phase synchronization between antagonistic elbow muscles and thus to explore the coupling and common neural inputs of antagonistic elbow muscles during sustained submaximal isometric fatiguing contraction. Fifteen healthy male subjects sustained an isometric elbow flexion at 20 % maximal level until exhaustion, while surface electromyographic signals (sEMG) were collected from biceps brachii (BB) and triceps brachii (TB). sEMG signals were divided into the first half (stage 1 with minimal fatigue) and second half (stage 2 with severe fatigue) of the contraction. Coherence and phase synchronization analysis was conducted between sEMG of BB and TB, and coherence value and phase synchronization index in alpha (8-12 Hz), beta (15-35 Hz) and gamma (35-60 Hz) frequency bands were obtained. Significant increase in EMG-EMG coherence and phase synchronization index in alpha and beta frequency bands between antagonistic elbow flexion muscles was observed all increased in stage 2 compared to stage 1. Coupling of EMG activities between antagonistic muscles increased as a result of fatigue caused by 20 % maximal level sustained isometric elbow flexion, indicating the increased interconnection between synchronized cortical neurons and the motoneuron pool of BB and TB, which may be cortical in origin. This increased coupling may help to maintain coactivation level so as to ensure joint stability on the basis of maintaining the joint force output. PMID:25515087

  20. 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

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. 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

  7. Fatigue and pain in human jaw muscles during a sustained, low-intensity clenching task.

    PubMed

    Svensson, P; Burgaard, A; Schlosser, S

    2001-08-01

    Fatigue, pain and changes in the electromyographic (EMG) activity of the jaw-closing muscles are well documented during short, high-intensity tooth-clenching tasks but less so during sustained, low-intensity tasks. In this study, 11 healthy men clenched on a bite-force meter for 60 min at 10% of the maximal voluntary contraction (MVC) and scored the intensity of fatigue and pain on separate 10 cm visual analogue scales (VAS). Surface EMG activity from the masseter and anterior temporalis muscles was recorded in 10 s epochs every 5 min throughout the task. Pressure-pain thresholds (PPTs) in the jaw-closing muscles, unassisted maximum jaw opening and MVC were determined before and after the task. All participants reported an increasing sensation of fatigue in the jaw-closing muscles during the task (mean+/-SD: peak VAS=7.5+/-2.0 cm) but all were able to maintain the required force. Most (7/11) also reported a painful sensation (peak VAS=2.7+/-2.8 cm). The jaw-opening capacity (59.5+/-7.4 vs. 58.3+/-6.5 mm, P=0.031) and the MVC (777+/-73 vs. 652+/-115 N,P=0.002) were slightly, but significantly, decreased immediately after the task whereas the PPTs remained unchanged (ANOVA: P=0.612). The mean frequency of the EMG activity decreased in all muscles during the task (95.7 vs. 46.6 Hz;P<0.001), and the root mean squares increased (53.2 vs. 154 microV, P<0.001). The changes in EMG activity were more strongly correlated with the sensation of fatigue than pain. These findings demonstrate that a sustained, low-intensity clenching task can induce subjective and electrophysiological indications of fatigue.

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

    SciTech Connect

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

    1993-03-01

    The results of recent studies on the fatigue and fracture behavior of extruded Ti-48Al + 20 vol pct TiNb and hot-isostatically pressed ('hipped') MoSi[sub 2] + 20 vol pct Nb are presented (compositions in atomic percent unless stated otherwise). The effects of ductile phase reinforcement of Ti-48Al and MoSi[sub 2] on the micromechanisms of fracture under monotonic 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 monotonic 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.

  9. Effect of Gender, Disease Duration and Treatment on Muscle Strength in Myasthenia Gravis

    PubMed Central

    Citirak, Gülsenay; Cejvanovic, Sanja; Andersen, Henning; Vissing, John

    2016-01-01

    Introduction The aim of this observational, cross-sectional study was to quantify the potential presence of muscle weakness among patients with generalized myasthenia gravis (gMG). The influence of gender, treatment intensity and disease duration on muscle strength and disease progression was also assessed. Methods Muscle strength was tested in 8 muscle groups by manual muscle testing and by hand-held dynamometry in 107 patients with gMG and 89 healthy age- and gender-matched controls. Disease duration, severity and treatment history were reviewed and compared with muscle strength. Results Patients had reduced strength in all tested muscle group compared to control subjects (p<0.05). Women with gMG were stronger than men (decrease in strength 22.6% vs. 32.7% in men, P<0.05). Regional differences in muscle weakness were also evident, with proximal muscles being more affected. Interestingly, muscle strength did not correlate with disease duration and treatment intensity. Conclusions The results of this study show that in patients with gMG; 1) there is significant muscle weakness, 2) muscle weakness is more pronounced in men than women, 3) shoulder abductors, hip flexors, and neck muscles are the most affected muscle groups and 4) disease duration or treatment intensity alone are not predictors of loss of muscle strength in gMG. PMID:27741232

  10. Single-cycle and fatigue strengths of adhesively bonded lap joints

    SciTech Connect

    Metzinger, K.E.; Guess, T.R.

    1998-12-31

    This study considers a composite-to-steel tubular lap joint in which failure typically occurs when the adhesive debonds from the steel adherend. The same basic joint was subjected to compressive and tensile axial loads (single-cycle) as well as bending loads (fatigue). The purpose of these tests was to determine whether failure is more dependent on the plastic strain or the peel stress that develops in the adhesive. For the same joint, compressive and tensile loads of the same magnitude will produce similar plastic strains but peel stresses of opposite signs in the adhesive. In the axial tests, the tensile strengths were much greater than the compressive strengths - indicating that the peel stress is key to predicting the single-cycle strengths. To determine the key parameter(s) for predicting high-cycle fatigue strengths, a test technique capable of subjecting a specimen to several million cycles per day was developed. In these bending tests, the initial adhesive debonding always occurred on the compressive side. This result is consistent with the single-cycle tests, although not as conclusive due to the limited number of tests. Nevertheless, a fatigue test method has been established and future tests are planned.

  11. Effects of muscle fatigue on the usability of a myoelectric human-computer interface.

    PubMed

    Barszap, Alexander G; Skavhaug, Ida-Maria; Joshi, Sanjay S

    2016-10-01

    Electromyography-based human-computer interface development is an active field of research. However, knowledge on the effects of muscle fatigue for specific devices is limited. We have developed a novel myoelectric human-computer interface in which subjects continuously navigate a cursor to targets by manipulating a single surface electromyography (sEMG) signal. Two-dimensional control is achieved through simultaneous adjustments of power in two frequency bands through a series of dynamic low-level muscle contractions. Here, we investigate the potential effects of muscle fatigue during the use of our interface. In the first session, eight subjects completed 300 cursor-to-target trials without breaks; four using a wrist muscle and four using a head muscle. The wrist subjects returned for a second session in which a static fatiguing exercise took place at regular intervals in-between cursor-to-target trials. In the first session we observed no declines in performance as a function of use, even after the long period of use. In the second session, we observed clear changes in cursor trajectories, paired with a target-specific decrease in hit rates. PMID:27455381

  12. 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.

  13. 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.

  14. Influence of Carbon Content on Fatigue Strength of Drawn Steel Tubes for Small Once-Through Boiler

    NASA Astrophysics Data System (ADS)

    Yonekura, Daisuke; Fujie, Yuta; Murakami, Ri-Ichi; Tokunaga, Yukihiro

    Tension-tension fatigue tests were performed to examine the influence of carbon content on the fatigue properties of drawn specific steel tube (STB340) with/without post heat treatment for small once-through boiler. Two different carbon content steel tubes, C=0.06 and 0.12% were prepared. The as-received, as-drawn and post drawing heat treated series for each carbon content tube were prepared for fatigue test. The hardness, grain size and residual stress were measured for each series. As a result, the fatigue strength of as-received and as-drawn series showed a small difference between C=0.06 and 0.12% specimens. However, the post drawing heat treatment series showed obvious difference in the fatigue strength. The fatigue strength of higher carbon content tubes significantly decreased by the post drawing heat treatment, whereas the decrease of fatigue strength was little for lower carbon content heat treated tubes. The difference of fatigue strength was mainly caused by the degree of relaxation of work hardening by post heat treatment.

  15. Relative appendicular skeletal muscle mass is associated with isokinetic muscle strength and balance in healthy collegiate men.

    PubMed

    Kim, Sung-Eun; Hong, Ju; Cha, Jun-Youl; Park, Jung-Min; Eun, Denny; Yoo, Jaehyun; Jee, Yong-Seok

    2016-11-01

    There are few studies on the relationship between skeletal muscle mass and balance in the young ages. We investigated the relationship between appendicular skeletal muscle mass, isokinetic muscle strength of lower extremity, and balance among healthy young men using relative skeletal muscle index. Thirty men were grouped according to relative appendicular skeletal muscle mass index: higher skeletal muscle group (n = 15) and lower skeletal muscle group (n = 15). Static and dynamic balance abilities were measured using the following: a test where participants stood on one leg with eyes closed, a modified Clinical Test of Sensory Interaction on Balance (mCTSIB) with eyes open and eyes closed, a stability test, and limits of stability test. The muscle strength of lower extremities was measured with an isokinetic analyser in hip, knee, and ankle joints. Participants with higher appendicular skeletal muscle mass were significantly more stable in maintaining dynamic balance than those with lower appendicular skeletal muscle mass. Moreover, appendicular skeletal muscle mass index was positively correlated with dynamic balance ability. Participants with higher appendicular skeletal muscle mass had stronger strength in the lower extremity, and there were significant differences in the isokinetic torque ratios between groups. From these results, it can be inferred that higher appendicular skeletal muscle mass relates to muscle strength and the alteration in the peak torque ratio of the lower extremity, contributing to the maintenance of balance.

  16. 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

  17. Investigation of Contact Fatigue of High Strength Steel Gears Subjected to Surface Treatment

    NASA Astrophysics Data System (ADS)

    Dimitrov, L.; Michalopoulos, D.; Apostolopoulos, Ch. Alk.; Neshkov, T. D.

    2009-10-01

    In this paper the contact fatigue resistance of gearwheel teeth, subjected to shot-peening treatment, was investigated experimentally and analytically. The main objective was the evaluation and prediction of fatigue crack initiation, propagation, direction, and rate. A specially designed experimental rig was used to test a number of spur gears with the following characteristics: (a) unhardened, thermally untreated unpeened surfaces, (b) thermally treated unpeened surfaces, (c) unhardened peened surfaces, and (d) thermally treated peened surfaces. The theoretical model assumed initiation and propagation of surface cracks of gears operating in the elastohydrodynamic lubrication regime while loading was due to simultaneous rolling and sliding. Finite element modeling was used for the calculation of the stress field at the gear teeth. Comparison of the experimental and analytical results showed considerable improvement in the contact fatigue strength of thermally treated gear teeth and especially those that underwent shot peening, which increased surface durability. The residual stresses induced by shot peening are mainly effective in stopping microcrack propagation. When shot peening is applied on thermally untreated gear teeth surface, it increases the contact fatigue life of the material by 17% at 7 × 105 loading cycles. If shot peening is applied on carburized gear teeth surfaces, it increases the surface fatigue life by approximately 8% at 106 cycles. Contact fatigue and eventual pitting are treated as a normal consequence of the operation of machine elements. To study this failure process different types of testing machines have been designed. The purpose of this paper is the presentation and evaluation of a new design experimental rig for studying contact fatigue damage of gear teeth subjected to different load patterns.

  18. 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.

  19. 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

  20. Isolation and characterization of muscle fatigue substance with anti-tumor activities.

    PubMed

    Munoz, Ruben M; Han, Haiyong; Tegeler, Tony; Petritis, Konstantinos; Von Hoff, Daniel D; Hoffman, Stanley A

    2013-01-01

    Research during the 1950's indicated that exercise played a role in the reduction of tumor growth. In the 1960's our studies confirmed that tumor-bearing rats, exercised to fatigue, demonstrated tumor inhibition. Our further studies isolated an extract (Fatigue Substance, or F-Substance) from rectus femoris muscles of rats which had been electrically stimulated to fatigue. This extract significantly inhibited growth of transplanted rat tumors. Research continued until 1978 when it became apparent the methodology at that time was not able to further identify the substance's active components. Using current technology, we now report on the further isolation and characterization of F-Substance. In cell proliferation assays, extracts from electrically stimulated rat rectus femoris muscles had more significant inhibitory effect on the breast cancer cell line MCF-7 than those isolated from unstimulated muscles. To identify the molecule(s) responsible for the antitumor activity, a rat cytokine antibody array was used to profile the cytokines in the substances. Among the 29 different cytokines contained on the array, 3 showed greater than 3-fold difference between the substances isolated from the stimulated and unstimulated muscles. LIX (also known as CXCL5) is 6-fold higher in the substances isolated from stimulated muscles than those from the unstimulated muscles. TIMP-1 is 4.6 fold higher and sICAM is 3.6 fold higher in the substances from the stimulated muscles. Our results indicated that cytokines released from contracting muscles might be responsible for the antitumor effect of F-Substance.

  1. Scapulothoracic muscle fatigue associated with alterations in scapulohumeral rhythm kinematics during maximum resistive shoulder elevation.

    PubMed

    McQuade, K J; Dawson, J; Smidt, G L

    1998-08-01

    Clinical examinations and biomechanical analysis of the shoulder often include an assessment of the scapulohumeral rhythm. It is important to understand factors which may affect the scapulohumeral rhythm so that optimal diagnostic and therapeutic strategies can be devised. The purpose of this study was to determine if the scapulohumeral rhythm, when assessed under dynamic conditions, is altered as a result of a fatigue-inducing exercise. Twenty-five subjects were required to elevate their arm against maximum resistance until they were no longer able to completely elevate their arm. Three-dimensional kinematics were measured using an electromagnetic tracking system. Electromyographic activity was recorded from the upper trapezius, lower trapezius, serratus anterior, and the middle deltoid muscles. Power frequency spectrum using the Fast Fourier Transform and the root mean square signal amplitudes were determined for each muscle. The scapulohumeral rhythm was determined using least squares regressions of humeral elevation to scapular upward rotation for 20% intervals (phases) of elevation for each subject. The results showed that during the midrange of elevation to maximum elevation [phases 3-5 (60-150 degrees)], the scapulohumeral rhythm decreased with fatigue, and that the decrease in the scapulohumeral rhythm was associated with myoelectric indicators of fatigue (median power frequency). The study suggests that shoulder fatigue affects the way in which the scapula moves concomitantly with the humerus. Fatigue tends to result in increased motion of the scapula, which alters the scapulohumeral rhythm.

  2. DIFFERENTIATING sEMG SIGNALS UNDER MUSCLE FATIGUE AND NON-FATIGUE CONDITIONS USING LOGISTIC REGRESSION CLASSIFIERS.

    PubMed

    Venugopal, G; Ramakrishnan, S

    2014-01-01

    In this work, an attempt has been made to differentiate surface electromyography signals under fatigue and non-fatigue conditions. Signals are recorded from the biceps brachii muscles of 50 healthy volunteers. A well-established experimental protocol is followed for this purpose. Signals are subjected to further processing and features namely amplitude of first burst, myopulse percentage rate, Willison amplitude, power spectrum ratio and variance of central frequency are extracted. Three types of logistic regression classifiers, linear logistic, polykernel logistic regression and multinomial regression with ridge estimator are used for automated analysis. Classifier parameters are tuned to enhance the accuracy and performance indices of algorithms, and are compared. The results show distinct values for extracted features in fatigue conditions which are statistically significant (0.0027 = P = 0.03). All classifiers are found to be effective in demarcating the signals. The linear logistic regression algorithm provides 79% accuracy with 40 iterations. However, in the case of multinomial regression with ridge estimator, only 7 iterations are required to achieve 80% accuracy. The polykernel logistic regression algorithm (0.06 = ? = 0.1) also provides 80% accuracy but with a marginal increment (1 % to 4 %) for precision, recall and specificity compared to other two classifiers.

  3. Back and hip extensor muscles fatigue in healthy subjects: task-dependency effect of two variants of the Sorensen test

    PubMed Central

    Champagne, Annick; Descarreaux, Martin

    2008-01-01

    Paraspinal muscle fatigability during various trunk extension tests has been widely investigated by electromyography (EMG), and its task-dependency is established recently. Hip extensor muscle fatigability during the Sorensen test has been reported. The aim of the present experiments was to evaluate the task-dependency of back and hip extensor muscle fatigue during two variants of the Sorensen test. We hypothesized that the rate of muscular fatigue of the hip and back extensor muscles varies according to the test position. Twenty healthy young males with no history of low back pain volunteered to participate in this cross-sectional study. They were asked to perform two body weight-dependent isometric back extension tests (S1 = Sorensen test; S2 = modified Sorensen on a 45° Roman chair). Surface EMG activity of the paraspinal muscles (T10 and L5 levels) and hip extensor muscles (gluteus maximus; biceps femoris) was recorded, and muscular fatigue was assessed through power spectral analysis of the EMG data by calculating the rate of median power frequency change. We observed hip extensor muscle fatigue simultaneously with paraspinal muscle fatigue during both Sorensen variants. However, only L5 level EMG fatigue indices showed a task-dependency effect between S1 and S2. Hip extensor muscles appear to contribute to load sharing of the upper body mass during both Sorensen variants, but to a different extent because L5 level fatigue differs between the Sorensen variants. Our findings suggest that task-dependency has to be considered when EMG variables are compared between two types of lumbar muscle-fatiguing tasks. PMID:18813961

  4. 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

  5. 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.

  6. Major League Baseball pace-of-play rules and their influence on predicted muscle fatigue during simulated baseball games.

    PubMed

    Sonne, Michael W L; Keir, Peter J

    2016-11-01

    Major League Baseball (MLB) has proposed rule changes to speed up baseball games. Reducing the time between pitches may impair recovery from fatigue. Fatigue is a known precursor to injury and may jeopardise joint stability. This study examined how fatigue accumulated during baseball games and how different pace of play initiatives may influence fatigue. Pitcher data were retrieved from a public database. A predictive model of muscle fatigue estimated muscle fatigue in 8 arm muscles. A self-selected pace (22.7 s), 12 s pace (Rule 8.04 from the MLB) and a 20 s rest (a pitch clock examined in the 2014 Arizona Fall League (AFL)) were examined. Significantly more muscle fatigue existed in both the AFL and Rule 8.04 conditions, when compared to the self-selected pace condition (5.01 ± 1.73%, 3.95 ± 1.20% and 3.70 ± 1.10% MVC force lost, respectively). Elevated levels of muscle fatigue are predicted in the flexor-pronator mass, which is responsible for providing elbow stability. Reduced effectiveness of the flexor-pronator mass may reduce the active contributions to joint rotational stiffness, increasing strain on the ulnar collateral ligament (UCL) and possibly increasing injury risk.

  7. Major League Baseball pace-of-play rules and their influence on predicted muscle fatigue during simulated baseball games.

    PubMed

    Sonne, Michael W L; Keir, Peter J

    2016-11-01

    Major League Baseball (MLB) has proposed rule changes to speed up baseball games. Reducing the time between pitches may impair recovery from fatigue. Fatigue is a known precursor to injury and may jeopardise joint stability. This study examined how fatigue accumulated during baseball games and how different pace of play initiatives may influence fatigue. Pitcher data were retrieved from a public database. A predictive model of muscle fatigue estimated muscle fatigue in 8 arm muscles. A self-selected pace (22.7 s), 12 s pace (Rule 8.04 from the MLB) and a 20 s rest (a pitch clock examined in the 2014 Arizona Fall League (AFL)) were examined. Significantly more muscle fatigue existed in both the AFL and Rule 8.04 conditions, when compared to the self-selected pace condition (5.01 ± 1.73%, 3.95 ± 1.20% and 3.70 ± 1.10% MVC force lost, respectively). Elevated levels of muscle fatigue are predicted in the flexor-pronator mass, which is responsible for providing elbow stability. Reduced effectiveness of the flexor-pronator mass may reduce the active contributions to joint rotational stiffness, increasing strain on the ulnar collateral ligament (UCL) and possibly increasing injury risk. PMID:26940036

  8. Effect of bond thickness on fracture and fatigue strength of adhesively bonded composite joints

    NASA Technical Reports Server (NTRS)

    Mall, S.; Ramamurthy, G.

    1989-01-01

    An experimental investigation of composite to composite bonded joints was undertaken to study the effect of bond thickness on debond growth rate under cyclic loading and critical strain energy release rate under static loading. Double cantilever beam specimens of graphite/epoxy adherends bonded with EC 3445 were tested under mode I loading. A different behavior of fracture and fatigue strength was observed with variation of bondline thickness.

  9. Composite-to-metal tubular lap joints: Strength and fatigue resistance

    NASA Astrophysics Data System (ADS)

    Reedy, E. D., Jr.; Guess, T. R.

    1993-10-01

    The axial strength and fatigue resistance of thick-walled, adhesively bonded E-glass composite-to-aluminum tubular lap joints have been measured for tensile and compressive loadings. The joint specimen bonds a 63 mm OD aluminum tube within each end of a 300 mm long, 6 mm thick E-glass/epoxy tube. Untapered, 12.5 mm thick aluminum adherends were used in all but four of the joint specimens. The aluminum adherends in the remaining four specimens were tapered to a thickness of 1 mm at the inner bond end (the bond end where the aluminum adherend terminates). For all loadings, joint failure initiates at the inner bond end as a crack grows in the adhesive adjacent to the interface. Test results for a tension-tension fatigue loading indicate that fatigue can severely degrade joint performance. Interestingly, measured tensile strength and fatigue resistance for joints with untapered adherends is substantially greater than compressive strength and fatigue resistance. The joint specimen has been analyzed in two different ways: one approach models the adhesive as an uncracked, elastic-perfectly plastic material, while the other approach uses a linear elastic fracture mechanics methodology. Results for the uncracked, elastic-plastic adhesive model indicate that observed bond failure occurs in the region of highest calculated stresses, extensive bond yielding occurs at load levels well below that required to fail the joint, and a tensile peel stress is generated by a compressive joint loading when the aluminum adherends are untapered. This latter result is consistent with the observed joint tensile-compressive strength differential. Results of the linear elastic fracture mechanics analysis of a joint with untapered aluminum adherends are also consistent with the observed differential strength effect since a mode 1 crack loading is predicted for a compressive joint loading. Calculations and a limited number of tests suggest that it may be possible to selectively control the

  10. Can acoustic emission detect the initiation of fatigue cracks: Application to high-strength light alloys used in aeronautics

    NASA Technical Reports Server (NTRS)

    Bathias, C.; Brinet, B.; Sertour, G.

    1978-01-01

    Acoustic emission was used for the detection of fatigue cracking in a number of high-strength light alloys used in aeronautical structures. Among the features studied were: the influence of emission frequency, the effect of surface oxidation, and the influence of grains. It was concluded that acoustic emission is an effective nondestructive technique for evaluating the initiation of fatigue cracking in such materials.

  11. Assessment of muscle fatigue in low level monotonous task performance during car driving.

    PubMed

    Hostens, I; Ramon, H

    2005-06-01

    Knowledge of the muscle activation and the development of muscle fatigue may provide more inside in the effects of long-term driving in the occurrence of health problems in the neck/shoulder/back area. The basic assumption behind fatigue detection with electromyography (EMG) is an increase in the EMG amplitude and a decrease of the mean frequency (MF). This study aimed at checking this assumption in monotonous task performance with low level activity during car driving. Surface electromyography was captured from left and right trapezius and deltoid muscles, during a repetitive, non-continuous, driving task (gearing and steering) and the active parts were separated from the non-active parts. Muscle stiffness was reported by more than half of the subjects after a 1 h drive. Only for the active parts a significant decrease of the MF was seen. But also the EMG amplitude decreased significantly. Two possible mechanisms are posted in literature for this finding: no extra recruitment of motor units (MU) and potentiation of muscle fibers. Literature also hypothesizes that low-force occupational work engages only a fraction of the MU available for recruitment and that these units are selectively type I muscle fibers (Cinderella fibers). Initiators of this phenomenon are probably the time lag between activations and the stress from driving and vibration exposure.

  12. 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

  13. 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

  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. Carnitine Acetyltransferase Mitigates Metabolic Inertia and Muscle Fatigue during Exercise.

    PubMed

    Seiler, Sarah E; Koves, Timothy R; Gooding, Jessica R; Wong, Kari E; Stevens, Robert D; Ilkayeva, Olga R; Wittmann, April H; DeBalsi, Karen L; Davies, Michael N; Lindeboom, Lucas; Schrauwen, Patrick; Schrauwen-Hinderling, Vera B; Muoio, Deborah M

    2015-07-01

    Acylcarnitine metabolites have gained attention as biomarkers of nutrient stress, but their physiological relevance and metabolic purpose remain poorly understood. Short-chain carnitine conjugates, including acetylcarnitine, derive from their corresponding acyl-CoA precursors via the action of carnitine acetyltransferase (CrAT), a bidirectional mitochondrial matrix enzyme. We show here that contractile activity reverses acetylcarnitine flux in muscle, from net production and efflux at rest to net uptake and consumption during exercise. Disruption of this switch in mice with muscle-specific CrAT deficiency resulted in acetyl-CoA deficit, perturbed energy charge, and diminished exercise tolerance, whereas acetylcarnitine supplementation produced opposite outcomes in a CrAT-dependent manner. Likewise, in exercise-trained compared to untrained humans, post-exercise phosphocreatine recovery rates were positively associated with CrAT activity and coincided with dramatic shifts in muscle acetylcarnitine dynamics. These findings show acetylcarnitine serves as a critical acetyl buffer for working muscles and provide insight into potential therapeutic strategies for combatting exercise intolerance. PMID:26154055

  16. Effect of intravaginal electrical stimulation on pelvic floor muscle strength.

    PubMed

    Amaro, João Luiz; Gameiro, Mônica Orsi; Padovani, Carlos Roberto

    2005-01-01

    The aim of this study was to evaluate the effect of intravaginal electrical stimulation (IES) on pelvic floor muscle (PFM) strength in patients with mixed urinary incontinence (MUI). Between January 2001 and February 2002, 40 MUI women (mean age: 48 years) were studied. Urge incontinence was the predominant symptom; 92.5% also presented mild stress urinary incontinence (SUI). Selection criteria were clinical history and urodynamics. Pre-treatment urodynamic study showed no statistical differences between the groups. Ten percent of the women in each group had involuntary detrusor contractions. Patients were randomly distributed, in a double-blind study, into two groups. Group G1 (n=20), effective IES, and group G2 (n=20), sham IES, with follow-up at 1 month. The following parameters were studied: (1) clinical questionnaire, (2) examiner's evaluation of perineal muscle strength, (3) objective evaluation of perineal muscle by perineometry, (4) vaginal weight test, and (5) urodynamic study. The IES protocol consisted of three 20-min sessions per week over a 7-week period using a Dualpex Uro 996 at 4 Hz. There was no statistically significant difference in the demographic data of both groups. The number of micturitions per 24 h after treatment was reduced significantly in both groups. Urge incontinence, present in all patients before treatment, was reduced to 15% in G1 and 31.5% in G2 post-treatment. The subjective evaluation of PFM strength demonstrated a significant improvement in G1. Objective evaluation of PFM force by perineometer showed a significant improvement in maximum peak contraction post-treatment in both groups. In the vaginal weight test, there was a significant increase in average number of cone retentions post-treatment in both groups. With regard to satisfaction level, after treatment, 80% of the patients in G1 and 65% of the patients in G2 were satisfied. There was no statistically significant difference between the groups. There was a significant

  17. Low force contractions induce fatigue consistent with muscle mRNA expression in people with spinal cord injury.

    PubMed

    Petrie, Michael A; Suneja, Manish; Faidley, Elizabeth; Shields, Richard K

    2014-02-01

    Spinal cord injury (SCI) is associated with muscle atrophy, transformation of muscle fibers to a fast fatigable phenotype, metabolic inflexibility (diabetes), and neurogenic osteoporosis. Electrical stimulation of paralyzed muscle may mitigate muscle metabolic abnormalities after SCI, but there is a risk for a fracture to the osteoporotic skeletal system. The goal of this study was to determine if low force stimulation (3 Hz) causes fatigue of chronically paralyzed muscle consistent with selected muscle gene expression profiles. We tested 29 subjects, nine with a SCI and 20 without and SCI, during low force fatigue protocol. Three SCI and three non-SCI subjects were muscle biopsied for gene and protein expression analysis. The fatigue index (FI) was 0.21 ± 0.27 and 0.91 ± 0.01 for the SCI and non-SCI groups, respectively, supporting that the low force protocol physiologically fatigued the chronically paralyzed muscle. The post fatigue potentiation index (PI) for the SCI group was increased to 1.60 ± 0.06 (P <0.001), while the non-SCI group was 1.26 ± 0.02 supporting that calcium handling was compromised with the low force stimulation. The mRNA expression from genes that regulate atrophy and fast properties (MSTN, ANKRD1, MYH8, and MYCBP2) was up regulated, while genes that regulate oxidative and slow muscle properties (MYL3, SDHB, PDK2, and RyR1) were repressed in the chronic SCI muscle. MSTN, ANKRD1, MYH8, MYCBP2 gene expression was also repressed 3 h after the low force stimulation protocol. Taken together, these findings support that a low force single twitch activation protocol induces paralyzed muscle fatigue and subsequent gene regulation. These findings suggest that training with a low force protocol may elicit skeletal muscle adaptations in people with SCI. PMID:24744911

  18. 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

  19. 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

  20. 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.

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

    PubMed

    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.

  2. 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

  3. Muscle fatigue during cross country sprint assessed by activation patterns and electromyographic signals time-frequency analysis.

    PubMed

    Zory, R; Molinari, F; Knaflitz, M; Schena, F; Rouard, A

    2011-12-01

    The aims of this study were as follows: (i) analysis of activation patterns during the spurt of two heats of a cross country skiing sprint with the double poling technique and (ii) quantification of muscle fatigue of the investigated muscles. Eight elite skiers were tested and surface electromyographic signals (EMG) were recorded from seven muscles of the upper and lower limbs. For each subject and each muscle, the activation intervals were calculated for relying on a double-threshold statistical detector and the average rectified value was calculated on each activation interval. The detected activations were processed by a time-frequency algorithm in order to assess the progression of muscle fatigue. The EMG activation patterns and EMG amplitude highlighted no significant difference between the two spurts, despite a generally lower speed in the second spurt. The frequency analysis showed that upper body muscles are the first to be affected by fatigue and that clear signs of muscle fatigue appear right from the first spurt of the sprint simulation (i.e., biceps and triceps brachii) with a decrease in the instantaneous mean frequency. Biceps brachii activations and fatigue demonstrated the involvement of this muscle in propulsion.

  4. Reversible oxidation of vicinal-thiols motif in sarcoplasmic reticulum calcium regulatory proteins is involved in muscle fatigue mechanism.

    PubMed

    Vázquez, Pável; Tirado-Cortés, Aldo; Álvarez, Rocío; Ronjat, Michel; Amaya, Araceli; Ortega, Alicia

    2016-10-01

    The mechanism underlying fatigue in skeletal muscle (SM) related to the redox-potential hypothesis, ranges from a direct effect of oxygen reactive species, to a number of other free radical intermediates targeting specific amino acids in the Ca(2+)-regulatory proteins of the sarcoplasmic reticulum (SR). In the present study, we investigate the selective oxidation/reduction of the protein motif Cys-(Xn=2-6)-Cys, known as a vicinal thiol group (VTG), present in the SR Ca(2+)-ATPase (SERCA) and in the Ca(2+)-channel ryanodine receptor (RyR) which are modified during muscle fatigue in SM. Selective oxidation of VTG with phenyl arsine oxide (PAO) increases fatigue in rat isolated SM and fatigue is prevented when muscle is previously incubated with a VTG selective reducing agent, 2,3-dimercaptopropanol (British anti-Lewisite (BAL)). In isolated SR membranes, PAO [<0.1mM] modifies SERCA conformation and inhibits ATPase activity but does not affect Ca(2+)-release. However, PAO at [>0.1mM] inhibits SERCA and RyR activities in a reversible manner by selectively reducing them. Interestingly, as observed by differential scanning calorimetry, the conformation of SERCA from fatigued muscle changed in a similar manner as when SERCA VTG where oxidized. The addition of BAL to fatigued muscle restored the structural conformation and activity of SERCA with full recovery of muscle force production after fatigue. We conclude that VTG reversible oxidation of SR Ca(2+) regulatory proteins are involved in muscle contraction/relaxation and are a molecular mechanism to be considered for muscle fatigue.

  5. 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

  6. Assessment of skeletal muscle fatigue of road maintenance workers based on heart rate monitoring and myotonometry

    PubMed Central

    Roja, Zenija; Kalkis, Valdis; Vain, Arved; Kalkis, Henrijs; Eglite, Maija

    2006-01-01

    Objective This research work is dedicated to occupational health problems caused by ergonomic risks. The research object was road building industry, where workers have to work very intensively, have long work hours, are working in forced/constrained work postures and overstrain during the work specific parts of their bodies. The aim of this study was to evaluate the work heaviness degree and to estimate the muscle fatigue of workers after one week work cycle. The study group consisted of 10 road construction and maintenance workers and 10 pavers aged between 20 and 60 years. Methods Physical load were analyzed by measuring heart rate (HR), work postures (OWAS) and perceived exertion (RPE). Assessments of the muscles strain and functional state (tone) were carried out using myotonometric (MYO) measurements. The reliability of the statistical processing of heart rate monitoring and myotonometry data was determined using correlating analysis. Results This study showed that that road construction and repairing works should be considered as a hard work according to average metabolic energy consumption 8.1 ± 1.5 kcal/min; paving, in its turn, was a moderately hard work according to 7.2 ± 1.1 kcal/min. Several muscle tone levels were identified allowing subdivision of workers into three conditional categories basing on muscle tone and fatigue: I – absolute muscle relaxation and ability to relax; II – a state of equilibrium, when muscles are able to adapt to the work load and are partly able to relax; and III – muscle fatigue and increased tone. It was also found out that the increase of muscle tone and fatigue mainly depend on workers physical preparedness and length of service, and less – on their age. Conclusion We have concluded that a complex ergonomic analysis consisting of heart rate monitoring, assessment of compulsive working postures and myotonometry is appropriate to assess the work heaviness degree and can provide prognosis of occupational pathology

  7. 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.

  8. 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

  9. 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

  10. 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

  11. Physiological functions of the effects of the different bathing method on recovery from local muscle fatigue

    PubMed Central

    2012-01-01

    Background Recently, mist saunas have been used in the home as a new bathing style in Japan. However, there are still few reports on the effects of bathing methods on recovery from muscle fatigue. Furthermore, the effect of mist sauna bathing on human physiological function has not yet been revealed. Therefore, we measured the physiological effects of bathing methods including the mist sauna on recovery from muscle fatigue. Methods The bathing methods studied included four conditions: full immersion bath, shower, mist sauna, and no bathing as a control. Ten men participated in this study. The participants completed four consecutive sessions: a 30-min rest period, a 10-min all out elbow flexion task period, a 10-min bathing period, and a 10-min recovery period. We evaluated the mean power frequency (MNF) of the electromyogram (EMG), rectal temperature (Tre), skin temperature (Tsk), skin blood flow (SBF), concentration of oxygenated hemoglobin (O2Hb), and subjective evaluation. Results We found that the MNF under the full immersion bath condition was significantly higher than those under the other conditions. Furthermore, Tre, SBF, and O2Hb under the full immersion bath condition were significantly higher than under the other conditions. Conclusions Following the results for the full immersion bath condition, the SBF and O2Hb of the mist sauna condition were significantly higher than those for the shower and no bathing conditions. These results suggest that full immersion bath and mist sauna are effective in facilitating recovery from muscle fatigue. PMID:22980588

  12. 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.

  13. 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

  14. Locomotor muscle fatigue increases cardiorespiratory responses and reduces performance during intense cycling exercise independently from metabolic stress.

    PubMed

    Marcora, Samuele M; Bosio, Andrea; de Morree, Helma M

    2008-03-01

    Locomotor muscle fatigue, defined as an exercise-induced reduction in maximal voluntary force, occurs during prolonged exercise, but its effects on cardiorespiratory responses and exercise performance are unknown. In this investigation, a significant reduction in locomotor muscle force (-18%, P < 0.05) was isolated from the metabolic stress usually associated with fatiguing exercise using a 100-drop-jumps protocol consisting of one jump every 20 s from a 40-cm-high platform. The effect of this treatment on time to exhaustion during high-intensity constant-power cycling was measured in study 1 (n = 10). In study 2 (n = 14), test duration (871 +/- 280 s) was matched between fatigue and control condition (rest). In study 1, locomotor muscle fatigue caused a significant curtailment in time to exhaustion (636 +/- 278 s) compared with control (750 +/- 281 s) (P = 0.003) and increased cardiac output. Breathing frequency was significantly higher in the fatigue condition in both studies despite similar oxygen consumption and blood lactate accumulation. In study 2, high-intensity cycling did not induce further fatigue to eccentrically-fatigued locomotor muscles. In both studies, there was a significant increase in heart rate in the fatigue condition, and perceived exertion was significantly increased in study 2 compared with control. These results suggest that locomotor muscle fatigue has a significant influence on cardiorespiratory responses and exercise performance during high-intensity cycling independently from metabolic stress. These effects seem to be mediated by the increased central motor command and perception of effort required to exercise with weaker locomotor muscles. PMID:18184760

  15. 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.

  16. 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

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

    SciTech Connect

    Bigelow, C.A. )

    1989-03-01

    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. 6 refs.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. Comparison of Two Different Modes of Active Recovery on Muscles Performance after Fatiguing Exercise in Mountain Canoeist and Football Players

    PubMed Central

    Mika, Anna; Oleksy, Łukasz; Kielnar, Renata; Wodka-Natkaniec, Ewa; Twardowska, Magdalena; Kamiński, Kamil; Małek, Zbigniew

    2016-01-01

    Background The aim of this study is to assess if the application of different methods of active recovery (working the same or different muscle groups from those which were active during fatiguing exercise) results in significant differences in muscle performance and if the efficiency of the active recovery method is dependent upon the specific sport activity (training loads). Design A parallel group non-blinded trial with repeated measurements. Methods Thirteen mountain canoeists and twelve football players participated in this study. Measurements of the bioelectrical activity, torque, work and power of the vastus lateralis oblique, vastus medialis oblique, and rectus femoris muscles were performed during isokinetic tests at a velocity of 90°/s. Results Active legs recovery in both groups was effective in reducing fatigue from evaluated muscles, where a significant decrease in fatigue index was observed. The muscles peak torque, work and power parameters did not change significantly after both modes of active recovery, but in both groups significant decrease was seen after passive recovery. Conclusions We suggest that 20 minutes of post-exercise active recovery involving the same muscles that were active during the fatiguing exercise is more effective in fatigue recovery than active exercise using the muscles that were not involved in the exercise. Active arm exercises were less effective in both groups which indicates a lack of a relationship between the different training regimens and the part of the body which is principally used during training. PMID:27706260

  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. Myostatin Neutralization Results in Preservation of Muscle Mass and Strength in Preclinical Models of Tumor-Induced Muscle Wasting.

    PubMed

    Smith, Rosamund C; Cramer, Martin S; Mitchell, Pamela J; Capen, Andrew; Huber, Lysiane; Wang, Rong; Myers, Laura; Jones, Bryan E; Eastwood, Brian J; Ballard, Darryl; Hanson, Jeff; Credille, Kelly M; Wroblewski, Victor J; Lin, Boris K; Heuer, Josef G

    2015-07-01

    Skeletal muscle wasting occurs in a great majority of cancer patients with advanced disease and is associated with a poor prognosis and decreased survival. Myostatin functions as a negative regulator of skeletal muscle mass and has recently become a therapeutic target for reducing the loss of skeletal muscle and strength associated with clinical myopathies. We generated neutralizing antibodies to myostatin to test their potential use as therapeutic agents to attenuate the skeletal muscle wasting due to cancer. We show that our neutralizing antimyostatin antibodies significantly increase body weight, skeletal muscle mass, and strength in non-tumor-bearing mice with a concomitant increase in mean myofiber area. The administration of these neutralizing antibodies in two preclinical models of cancer-induced muscle wasting (C26 colon adenocarcinoma and PC3 prostate carcinoma) resulted in a significant attenuation of the loss of muscle mass and strength with no effect on tumor growth. We also show that the skeletal muscle mass- and strength-preserving effect of the antibodies is not affected by the coadministration of gemcitabine, a common chemotherapeutic agent, in both non-tumor-bearing mice and mice bearing C26 tumors. In addition, we show that myostatin neutralization with these antibodies results in the preservation of skeletal muscle mass following reduced caloric intake, a common comorbidity associated with advanced cancer. Our findings support the use of neutralizing antimyostatin antibodies as potential therapeutics for cancer-induced muscle wasting.

  5. Effects of hip abductor muscle fatigue on gait control and hip position sense in healthy older adults.

    PubMed

    Arvin, Mina; Hoozemans, Marco J M; Burger, Bart J; Rispens, Sietse M; Verschueren, Sabine M P; van Dieën, Jaap H; Pijnappels, Mirjam

    2015-10-01

    We experimentally investigated whether unilateral hip abductor muscle fatigue affected gait control and hip position sense in older adults. Hip abductor muscles were fatigued unilaterally in side-lying position in 17 healthy older adults (mean age 73.2 SD 7.7 years). Hip joint position sense was assessed by an active-active repositioning test while standing and was expressed as absolute and relative errors. Participants walked on a treadmill at their preferred walking speed, while 3D linear accelerations were collected by an inertial sensor at the lower back. Gait parameters, including step and stride time, local divergence exponents and harmonic ratio were quantified. In fatigued gait, stride time variability and step-to-step asymmetry in the frontal plane were significantly increased. Also a significantly slower mediolateral trunk movement in fatigued leg late stance toward the non-fatigued leg was observed. Despite these temporal and symmetry changes, gait stability in terms of the local divergence exponents was not affected by fatigue. Hip position sense was also affected by fatigue, as indicated by an increased relative error of 0.7° (SD 0.08) toward abduction. In conclusion, negative effects of fatigue on gait variability, step-to-step symmetry, mediolateral trunk velocity control and hip position sense indicate the importance of hip abductor muscles for gait control.

  6. 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

  7. 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

  8. Tibialis anterior muscle fatigue leads to changes in tibial axial acceleration after impact when ankle dorsiflexion angles are visually controlled.

    PubMed

    Duquette, Adriana M; Andrews, David M

    2010-08-01

    Heel impact forces may lead to injury as they travel through the human musculoskeletal system. Previous work on the effect that localized muscle fatigue has on the tibial response (shank axial acceleration) to impact was limited because ankle angle was not controlled. The purpose of this study was to compare the tibial response when the tibialis anterior was fatigued and when not fatigued, while participants controlled dorsiflexion angles at impact using visual feedback. Twenty participants (10 male, 10 female; M+/-SD=21.8+/-2.9 years) were strapped supine to a human pendulum apparatus, and instrumented with a low mass accelerometer (affixed medial to the tibial tuberosity). Participant dorsiflexion angle range was recorded by an electro-goniometer, and divided into four angle ranges so tibial response variables (peak tibial acceleration, time to peak acceleration, acceleration slope) could be compared when fatigued and not fatigued. Peak tibial acceleration and acceleration slopes decreased, and time to peak acceleration increased following fatigue, when comparing values across the same dorsiflexion ranges. Dorsiflexion angle alone did not account for differences in tibial response during localized leg muscle fatigue; supporting prior work and suggesting that the muscle and ankle joint become less stiff when fatigued, thereby increasing the lower extremity attenuation capability to heel impacts.

  9. Assessment of muscle mass and strength in mice

    PubMed Central

    Bonetto, Andrea; Andersson, Daniel C; Waning, David L

    2015-01-01

    Muscle weakness is an important phenotype of many diseases that is linked to impaired locomotion and increased mortality. The force that a muscle can generate is determined predominantly by muscle size, fiber type and the excitation–contraction coupling process. Here we describe methods for the histological assessment of whole muscle to determine fiber cross-sectional area and fiber type, determination of changes in myocyte size using C2C12 cells, in vivo functional tests and measurement of contractility in dissected whole muscles. The extensor digitorum longus and soleus muscles are ideally suited for whole-muscle contractility, and dissection of these muscles is described. PMID:26331011

  10. 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.

  11. Asymmetric six-strand core sutures enhance tendon fatigue strength and the optimal asymmetry.

    PubMed

    Kozono, N; Okada, T; Takeuchi, N; Hanada, M; Shimoto, T; Iwamoto, Y

    2016-10-01

    Under cyclic loading, we recorded the fatigue strength of a six-strand tendon repair with different symmetry in the lengths of suture purchase in two stumps of 120 dental rolls and in 30 porcine tendons. First, the strengths of the repairs with 1, 2, 3, 4 and 5 mm asymmetry were screened using the dental rolls. The asymmetric core suture repairs were then made with a Kessler repair of equal suture purchase (10 mm) in two tendon stumps, and shifting two other Kessler repairs by 1, 3 or 5 mm, respectively, along the longitudinal axis of the tendon in relation to the first (symmetric) Kessler repair. The core repairs with 3 mm or more asymmetry in suture purchases in two tendon ends showed significantly greater fatigue strength and significantly smaller gaps compared with 1 mm asymmetry in core suture repair. Our results support that asymmetric placement of core sutures in two tendon ends favour resisting gapping at the repair site and 3 mm or more asymmetry is needed to produce such beneficial effects.

  12. 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

  13. 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

  14. 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

    Hashimoto, Takayuki; Sakuraba, Keishoku

    2014-03-01

    [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.

  15. 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

  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. Effects of string stiffness on muscle fatigue after a simulated tennis match.

    PubMed

    Fabre, Jean Bernard; Martin, Vincent; Borelli, Gil; Theurel, Jean; Grélot, Laurent

    2014-06-01

    We tested the influence of string stiffness on the occurrence of forearm muscle fatigue during a tennis match. Sixteen tennis players performed two prolonged simulated tennis matches with low-stiffness or high-stiffness string. Before and immediately after exercise, muscle fatigability was evaluated on the forearm muscles during a maximal intermittent gripping task. Groundstroke ball speeds and the profile of acceleration of the racquet frame at collision were recorded during each match. The peak-to-peak amplitude of acceleration and the resonant frequency of the frame were significantly greater with high- (5060 ± 1892 m/s(2) and 204 ± 29 Hz, respectively) than with low-stiffness string (4704 ± 1671 m/s(2) and 191 ± 16 Hz, respectively). The maximal and the averaged gripping forces developed during the gripping task were significantly reduced after the tennis match with high- (-15 ± 14%, and -22 ± 14%, respectively), but not with low-stiffness string. The decrease of ball speed during the simulated matches tended to be greater with high- than with low-stiffness string (P = .06). Hence, playing tennis with high-stiffness string promotes forearm muscle fatigue development, which could partly contribute to the groundstroke ball speed decrement during the game.

  18. The effects of lumbar massage on muscle fatigue, muscle oxygenation, low back discomfort, and driver performance during prolonged driving.

    PubMed

    Durkin, J L; Harvey, A; Hughson, R L; Callaghan, J P

    2006-01-15

    An increasing dependence of society on automobiles for both work and leisure and the corresponding increase in time spent seated in the car has been correlated with a greater risk of low back pain and absence from work (Porter and Gyi 2002). This study examined the effects of three types of lumbar massage units on seating comfort, muscle fatigue, muscle oxygenation, muscle blood flow and driving performance during a 1 h simulated driving task. Electromyographic (EMG) signals were recorded from the right and left thoracic and lumbar erector spinae musculature. Average EMG (AEMG), mean power frequency (MPF), gaps and amplitude probability distribution function (APDF) parameters were analysed from the three massage seats and compared to a control seat. Near infrared spectroscopy (NIRS) and skin temperature from the right thoracic and lumbar erector spinae were used as an indication of muscle oxygenation and blood flow throughout the driving task. Ratings of perceived discomfort were used to assess driver discomfort, and driving performance was assessed by calculating mean lap times for the duration of each driving trial. The results showed statistically significant increases in skin temperature compared with the control seat after 60 min of driving. The NIRS results reflected these trends although the results were not statistically significant. AEMG and MPF measures showed no significant differences between the seats. MPF measures were found to increase over time, effects attributed to increases in muscle temperature. Gaps and APDF analyses revealed greater rest times and lower activation levels, respectively, with the control seat, which could result in increased loading of passive structures. This study demonstrated the beneficial effects of lumbar massage systems in increasing muscle blood flow and oxygenation. Although EMG parameters were not significantly different, the trends support the significant blood flow results. Future research should include longer

  19. The effects of low temperature fatigue on the RRR and strength of pure aluminum

    SciTech Connect

    Hartwig, K.T.; Lehmann, P.; Yuan, G.S.

    1985-03-01

    Low temperature fatigue effects on residual resistivity ratio (RRR = /rho/ /sub 273K/ //rho/ /sub 4.2K/ ) and strength of 30 and 1000 RRR aluminum are reported. The objective of this investigation is to select the best initial purity for the stabilizer aluminum used in energy storage magnets. Monolythic centimeter diameter specimens were fatigued at 4.2 K to strains (epsilon) reaching 0.3 percent. The resistivity ratio rapidly decreases during the first 100 cycles and approaches saturation (RRR/sub f/) after about 1000 cycles for all strains tested. The RRR/sub f/ values are different for different initial resistivity ratio (RRR/sub i/) values, but all tend to come together at 0.3% strain independent of RRR/sub i/. The maximum specimen stress (sigma/sub max/) is reached after about 1000 cycles also, and approaches a common value (sigma/sub max/ = epsilonE/2, where epsilon is the strain range and E the elastic modulus) independent of RRR/sub i/. Thus high purity aluminum becomes ''fully hard'' at equilibrium and behaves elastically. The impact of fatigue damage on conductor design and choice of stabilizer purity is considered.

  20. 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.

  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. 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

  3. Changes in Serum Free Amino Acids and Muscle Fatigue Experienced during a Half-Ironman Triathlon.

    PubMed

    Areces, Francisco; González-Millán, Cristina; Salinero, Juan José; Abian-Vicen, Javier; Lara, Beatriz; Gallo-Salazar, Cesar; Ruiz-Vicente, Diana; Del Coso, Juan

    2015-01-01

    The aim of this study was to investigate the relationship between changes in serum free amino acids, muscle fatigue and exercise-induced muscle damage during a half-ironman triathlon. Twenty-six experienced triathletes (age = 37.0 ± 6.8 yr; experience = 7.4 ± 3.0 yr) competed in a real half-ironman triathlon in which sector times and total race time were measured by means of chip timing. Before and after the race, a countermovement jump and a maximal isometric force test were performed, and blood samples were withdrawn to measure serum free amino acids concentrations, and serum creatine kinase levels as a blood marker of muscle damage. Total race time was 320 ± 37 min and jump height (-16.3 ± 15.2%, P < 0.001) and isometric force (-14.9 ± 9.8%; P = 0.007) were significantly reduced after the race in all participants. After the race, the serum concentration of creatine kinase increased by 368 ± 187% (P < 0.001). In contrast, the serum concentrations of essential (-27.1 ± 13.0%; P < 0.001) and non-essential amino acids (-24.4 ± 13.1%; P < 0.001) were significantly reduced after the race. The tryptophan/BCAA ratio increased by 42.7 ± 12.7% after the race. Pre-to-post changes in serum free amino acids did not correlate with muscle performance variables or post-race creatine kinase concentration. In summary, during a half-ironman triathlon, serum amino acids concentrations were reduced by > 20%. However, neither the changes in serum free amino acids nor the tryptophan/BCAA ratio were related muscle fatigue or muscle damage during the race.

  4. Changes in Serum Free Amino Acids and Muscle Fatigue Experienced during a Half-Ironman Triathlon

    PubMed Central

    Areces, Francisco; González-Millán, Cristina; Salinero, Juan José; Abian-Vicen, Javier; Lara, Beatriz; Gallo-Salazar, Cesar; Ruiz-Vicente, Diana; Del Coso, Juan

    2015-01-01

    The aim of this study was to investigate the relationship between changes in serum free amino acids, muscle fatigue and exercise-induced muscle damage during a half-ironman triathlon. Twenty-six experienced triathletes (age = 37.0 ± 6.8 yr; experience = 7.4 ± 3.0 yr) competed in a real half-ironman triathlon in which sector times and total race time were measured by means of chip timing. Before and after the race, a countermovement jump and a maximal isometric force test were performed, and blood samples were withdrawn to measure serum free amino acids concentrations, and serum creatine kinase levels as a blood marker of muscle damage. Total race time was 320 ± 37 min and jump height (-16.3 ± 15.2%, P < 0.001) and isometric force (-14.9 ± 9.8%; P = 0.007) were significantly reduced after the race in all participants. After the race, the serum concentration of creatine kinase increased by 368 ± 187% (P < 0.001). In contrast, the serum concentrations of essential (-27.1 ± 13.0%; P < 0.001) and non-essential amino acids (-24.4 ± 13.1%; P < 0.001) were significantly reduced after the race. The tryptophan/BCAA ratio increased by 42.7 ± 12.7% after the race. Pre-to-post changes in serum free amino acids did not correlate with muscle performance variables or post-race creatine kinase concentration. In summary, during a half-ironman triathlon, serum amino acids concentrations were reduced by > 20%. However, neither the changes in serum free amino acids nor the tryptophan/BCAA ratio were related muscle fatigue or muscle damage during the race. PMID:26372162

  5. 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

  6. A three-dimensional quantitative understanding of short fatigue crack growth in high strength aluminum alloys

    NASA Astrophysics Data System (ADS)

    Wen, Wei

    The behaviors of short fatigue crack (SFC) propagation through grain boundaries (GBs) were monitored during high cycle fatigue in an Al-Li alloy AA8090. The growth behaviors of SFCs were found to be mainly controlled by the twist components (alpha) of crack plane deflection across each of up to first 20 GBs along the crack path. The crack plane twist at the GB can result in a resistance against SFC growth; therefore SFC propagation preferred to follow a path with minimum alpha at each GB. In addition to the grain orientation, the tilting of GB could also affect alpha. An experiment focusing on quantifying GB-resistance was conducted on an Al-Cu alloy AA2024-T351. With a focused ion beam (FIB) and electron backscatter diffraction (EBSD), the micro-notches were made in front of the selected GBs which had a wide range of alpha, followed by monitoring the interaction of crack propagation from the notches with the GBs during fatigue. The crack growth rate was observed to decrease at each GB it had passed; and such growth-rate decrease was proportional to alpha. The resistance of the GB was determined to vary as a Weibull-type function of alpha. Based on these discoveries, a microstructure-based 3-D model was developed to quantify the SFC growth in high-strength Al alloys, allowing the prediction of crack front advancement in 3-D and the quantification of growth rate along the crack front. The simulation results yielded a good agreement with the experimental results about the SFC growth rate on the surface of the AA8090 Al alloy. The model was also used to predict the life of SFC growth statistically in different textures, showing potential application to texture design of alloys. Fatigue crack initiation at constituent particles (beta-phase) was preliminarily studied in the AA2024-T351 Al alloy. Cross-sectioning with the FIB revealed that the 3-D geometry, especially the thickness, of fractured constituent particles (beta-phase) was the key factor controlling the

  7. 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...

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. Relationship of fatigued run and rapid stop to ground reaction forces, lower extremity kinematics, and muscle activation.

    PubMed

    Nyland, J A; Shapiro, R; Stine, R L; Horn, T S; Ireland, M L

    1994-09-01

    Fatigue may be related to lower extremity injury. The effect of lower extremity fatigue on ground reaction force production, lower extremity kinematics, and muscle activation during the landing phase of a run and rapid stop was investigated. Subjects were 19 female, Division 1 collegiate basketball and volleyball players (mean age = 20.8 +/- 1.8 years, mean weight = 71.7 +/- 6.9 kg, mean height = 174 +/- 5 cm). Dominant leg ground reaction and muscle activation data were sampled at 2,000 Hz. Lower extremity kinematic data were sampled at 200 Hz, and three-dimensional analysis was performed. Knee extensor/flexor muscle activation tended to be delayed during fatigue (p < or = .08). Maximum knee flexion tended to occur earlier during fatigue (p < or = .09). Step-wise multiple regression suggested that the knee may be the primary site of force attenuation following fatigue. During fatigue, biodynamical compensations in the mechanical properties of the knee extensor musculature, as evidenced by differences in knee kinematics and muscle activation times, may occur to enhance knee stability.

  13. The effect of isokinetic testing speed on the reliability of muscle fatigue indicators during a hip abductor-adductor fatigue protocol.

    PubMed

    Gautrey, C N; Watson, T; Mitchell, A

    2013-07-01

    The aim of this study was to investigate the reliability of fatigue indicators calculated from peak torque and total work during isokinetic speeds of 60, 90, 120 and 180° · s-1 during a hip fatigue protocol. 10 males suffering from a history of unilateral functional ankle instability and 10 male healthy controls performed 5 maximal concentric contractions on an isokinetic dynamometer. Following a 4 min rest period subjects were instructed to perform repeated maximal concentric contractions to fatigue, which was defined as 3 consecutive repetitions below 50% of the maximum peak torque value. Each testing speed was randomised with 24 h between speeds. The subjects were asked to return to the laboratory 7 days later to repeat the 4 speeds, with 24 h between speeds. Muscle fatigue was determined for each testing speed by the fatigue index, the percent decrease in performance and the slope of the regression equation. The most reliable fatigue determination method was the slope of the regression equation, when testing at a speed of 120° · s-1. It is recommended that future investigators examine and plot their data before choosing the slope of the regression equation as their fatigue indicator, as a linear model is required. PMID:23549692

  14. 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.

  15. 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.

  16. Inspiratory muscle fatigue after race-paced swimming is not restricted to the front crawl stroke.

    PubMed

    Lomax, Mitch; Iggleden, Colin; Tourell, Alice; Castle, Sophie; Honey, Jo

    2012-10-01

    The occurrence of inspiratory muscle fatigue (IMF) has been documented after front crawl (FC) swimming of various distances. Whether IMF occurs after other competitive swimming strokes is not known. The aim of the present study was to assess the impact of all 4 competitive swimming strokes on the occurrence of IMF after race-paced swimming and to determine whether the magnitude of IMF was related to the breathing pattern adopted and hence breathing frequency (f(b)). Eleven, nationally ranked, youth swimmers completed four 200-m swims (one in each competitive stroke) on separate occasions. The order of the swims, which consisted of FC, backstroke (BK), breaststroke (BR), and butterfly (FLY), was randomized. Maximal inspiratory mouth pressure (MIP) was assessed before (after a swimming and inspiratory muscle warm-up) and after each swim with f(b) calculated post swim from recorded data. Inspiratory muscle fatigue was evident after each 200-m swim (p < 0.05) but did not differ between the 4 strokes (range 18-21%). No relationship (p > 0.05) was observed between f(b) and the change in MIP (FC: r = -0.456; BK: r = 0.218; BR: r = 0.218; and FLY: r = 0.312). These results demonstrate that IMF occurs in response to 200-m race-paced swimming in all strokes and that the magnitude of IMF is similar between strokes when breathing is ad libitum occurring no less than 1 breath (inhalation) every third stroke. PMID:22130403

  17. 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

  18. Role of central respiratory muscle fatigue in endurance exercise in normal subjects.

    PubMed

    Marciniuk, D; McKim, D; Sanii, R; Younes, M

    1994-01-01

    The role of central respiratory muscle fatigue in determining endurance time (ET) of steady-state ergometry, ventilation (VE), and breathing pattern during exhaustive submaximal exercise is not known. Six normal subjects exercised on a cycle ergometer to exhaustion at 72-82% of maximal power output on three occasions. During the second test, inspiratory muscle load was reduced (approximately 50% of baseline load) for all but the last 3 min of exercise. ET was determined, and VE, tidal volume (VT), respiratory rate (f), and sense of breathing effort (Borg scale) were assessed at different points during the assisted exercise and compared with the values obtained at the same time in identical tests without assist, carried out before and after the assisted test (different days). Borg scale rating was less and there was a nonsignificant trend for VT and VE to be higher and for f to be lower when the assist was in place than at the same time during the unassisted runs. In the last 3 min of exercise, when the respiratory load was comparable (assist removed) but ventilatory work history was different, there were no significant differences in sense of respiratory effort, VE, VT, or f between the experimental and control tests, and ET was also similar. We conclude that central respiratory muscle fatigue plays no role in determining ET, sense of respiratory effort, or breathing pattern in normal subjects during exhaustive submaximal exercise.

  19. Inspiratory muscle fatigue after race-paced swimming is not restricted to the front crawl stroke.

    PubMed

    Lomax, Mitch; Iggleden, Colin; Tourell, Alice; Castle, Sophie; Honey, Jo

    2012-10-01

    The occurrence of inspiratory muscle fatigue (IMF) has been documented after front crawl (FC) swimming of various distances. Whether IMF occurs after other competitive swimming strokes is not known. The aim of the present study was to assess the impact of all 4 competitive swimming strokes on the occurrence of IMF after race-paced swimming and to determine whether the magnitude of IMF was related to the breathing pattern adopted and hence breathing frequency (f(b)). Eleven, nationally ranked, youth swimmers completed four 200-m swims (one in each competitive stroke) on separate occasions. The order of the swims, which consisted of FC, backstroke (BK), breaststroke (BR), and butterfly (FLY), was randomized. Maximal inspiratory mouth pressure (MIP) was assessed before (after a swimming and inspiratory muscle warm-up) and after each swim with f(b) calculated post swim from recorded data. Inspiratory muscle fatigue was evident after each 200-m swim (p < 0.05) but did not differ between the 4 strokes (range 18-21%). No relationship (p > 0.05) was observed between f(b) and the change in MIP (FC: r = -0.456; BK: r = 0.218; BR: r = 0.218; and FLY: r = 0.312). These results demonstrate that IMF occurs in response to 200-m race-paced swimming in all strokes and that the magnitude of IMF is similar between strokes when breathing is ad libitum occurring no less than 1 breath (inhalation) every third stroke.

  20. Effect of pressure and timing of contraction on human rib cage muscle fatigue.

    PubMed

    Zocchi, L; Fitting, J W; Majani, U; Fracchia, C; Rampulla, C; Grassino, A

    1993-04-01

    Breathing against inspiratory loads can be accomplished with different degrees of coupling between the diaphragm and the other muscles attached to the rib cage (RCM). Thus, the electromyographic signs of fatigue develop separately in each muscle group. While breathing with diaphragm emphasis, the occurrence of diaphragmatic fatigue was found to be related to the tension-time index TTdi (= Pdi/Pdimax x Ti/Ttot). Above the critical range of 0.15 to 0.18, the endurance of the diaphragm is less than 1 h and it is inversely related to the TTdi value. However, in most loaded breathing conditions, the spontaneous pattern of breathing is characterized by predominant activation of RCM. The tension-time conditions at which fatigue develops during breathing with RCM emphasis are not known. We assessed the critical tension-time value in four normal subjects breathing with RCM emphasis against inspiratory threshold loads. RCM predominance was achieved by developing negative abdominal pressure swings during inspiration, and it was characterized by the tension-time index TTrc (Ppl/Pplmax x Tl/Ttot), where Ppl is pleural pressure developed under this condition. Above a critical TTrc value of 0.30, endurance time was inversely related to TTrc, and it resulted from failure of the RCM rather than of the diaphragm. We conclude that the critical threshold, as assessed by TTrc, is higher for breathing patterns with RCM emphasis than previously described by TTdi for diaphragm emphasis. However, when predominantly recruited, as in breathing patterns commonly adopted in loaded conditions, the RCM fatigue earlier than the diaphragm. PMID:8466120

  1. Development of FRP composite structural biomaterials: fatigue strength of the fiber/matrix interfacial bond in simulated in vivo environments.

    PubMed

    Latour, R A; Black, J

    1993-10-01

    Fiber/matrix interfacial bonding in fiber reinforced polymer (FRP) composite materials is potentially sensitive to degradation in aqueous environments. Ultimate bond strength (UBS) in carbon fiber/polysulfone (CF/PSF) and polyaramid/polysulfone (K49/PSF) was previously reported to be significantly decreased in two simulated in vivo environments. While UBS is a useful parameter, for orthopedic implant applications the fatigue behavior of the interface is probably a more relevant indicator of long-term composite material performance. In this article, the effects of simulated in vivo environments (saline, exudate) upon the fatigue behavior of the interface of CF/PSF and K49/PSF are reported. The fatigue behavior of both material combinations was linearly dependent on the logarithm of fatigue life in the dry (control), saline, and exudate environments. Testing either material in saline and exudate resulted in significantly lower fatigue strength than in the dry environment; however, results in the two wet environments were indistinguishable. The CF/PSF interface experienced fatigue failure at approximately 10(5) load cycles at a maximum applied load level of only 15% of its ultimate dry bond strength without indication of an endurance limit being reached. These results raise some important questions regarding the durability of CF/PSF composite in load bearing orthopedic applications.

  2. 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

  3. 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.

  4. Insulin Resistance Is Associated With Decreased Quadriceps Muscle Strength in Nondiabetic Adults Aged ≥70 Years

    PubMed Central

    Barzilay, Joshua I.; Cotsonis, George A.; Walston, Jeremy; Schwartz, Ann V.; Satterfield, Suzanne; Miljkovic, Iva; Harris, Tamara B.

    2009-01-01

    OBJECTIVE Lower-limb muscle strength is reduced in many people with diabetes. In this study, we examined whether quadriceps muscle strength is reduced in relation to insulin resistance in well-functioning ambulatory nondiabetic individuals. RESEARCH DESIGN AND METHODS Participants (age ≥70 years) underwent dual-energy X-ray absorptiometry (DEXA) scanning to ascertain muscle and fat mass, tests of quadriceps strength, computed tomography scanning of the quadriceps to gauge muscle lipid content, and fasting insulin and glucose level measurements from which homeostasis model assessment of insulin resistance (HOMA-IR) was derived. RESULTS In regression analysis, quadriceps strength per kilogram of muscle mass was negatively associated (P < 0.0001) with HOMA-IR independent of other factors negatively associated with strength such as increased age, female sex, low-physical activity, impaired fasting glucose, and increased total body fat. Muscle lipid content was not associated with strength. CONCLUSIONS A small decrease in quadriceps muscle force is associated with increased HOMA-IR in well-functioning nondiabetic adults, suggesting that diminished quadriceps muscle strength begins before diabetes. PMID:19171728

  5. 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.

  6. 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.

  7. 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

  8. Time-dependent strength degradation of a siliconized silicon carbide determined by dynamic fatigue

    SciTech Connect

    Breder, K.

    1995-10-01

    Both fast-fracture strength and strength as a function of stressing rate at room temperature, 1,100, and 1,400 C were measured for a siliconized SiC. The fast-fracture strength increased slightly from 386 MPa at room temperature to 424 MPa at 1,100 C and then dropped to 308 MPa at 1,400 C. The Weibull moduli at room temperature and 1,100 were 10.8 and 7.8, respectively, whereas, at 1,400 C, the Weibull modulus was 2.8. The very low Weibull modulus at 1,400 C was due to the existence of two exclusive flaw populations with very different characteristic strengths. The data were reanalyzed using two exclusive flaw populations. The ceramic showed no slow crack growth (SCG), as measured by dynamic fatigue at 1,100 C, but, at 1,400 C, an SCG parameter, n, of 15.5 was measured. Fractography showed SCG zones consisting of cracks grown out from silicon-rich areas. Time-to-failure predictions at given levels of failure probabilities were performed.

  9. Fatigue and caffeine effects in fast-twitch and slow-twitch muscles of the mouse.

    PubMed

    Brust, M

    1976-12-28

    In excised, curarized and massively stimulated fast-twitch mouse gastrocnemius muscles the early twitch tension enhancements (treppe) during 1/s activity between 10 and 36 degrees C increase and affect more contractions as temperature increases. Tension output eventually declines at a temperature-independent rate. Half-relaxation time lengthens below 25 degrees C and shortens above 25 degrees C. During 1/0.63s twitches half-relaxation time lengthens even at 25 degrees C. In slow-twitch soleus muscles activity decreases twitch tension and half-relaxation time regardless of temperature. Activity shortens contraction times in both muscles. Oxygen lack induced by NaN3 cannot account satisfactorily for these results. Activation is apparently more plastic in the gastrocnemius than in the soleus, and the relationship between the rates of their activation and relaxation processes and the temperature sensitivities of these rates also seem to differ. In both muscles caffeine can convert activity-induced shortened of half-relaxation times into prolongations. In the soleus this effect is more pronounced at 30 than at 25 degrees C. At high temperature and twitch rates caffeine reduces treppe amplitude and duration without affecting the eventual twitch tension decline in the gastrocnemius while it greatly accelerates twitch tension decline in the soleus. In both muscles intrafiber Ca2+ movements are apparently major determinants of fatigue behavior. PMID:1034914

  10. 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.

  11. Residual Stress and Fatigue Strength of Hybrid Laser-MIG-Welded A7N01P-T4

    NASA Astrophysics Data System (ADS)

    Wang, Qiuying; Chen, Hui; Qiu, Peixian; Zhu, Zongtao

    2016-09-01

    A7N01P-T4 aluminum alloy is widely used in some important welded components of high-speed trains. The hybrid laser-metal inert gas (MIG) welding process was studied to solve problems associated with the MIG welding process, such as low welding efficiency, high residual stress and deformation, and serious loss of strength. A high-speed camera, a voltage and current collection system, and NI DAQ were used to acquire arc profiles, welding voltage, and welding current simultaneously. Thermal cycle tests were carried out. Residual stresses induced by the welding process and fatigue strength of the joint were investigated. Large-size fatigue specimens were used in fatigue tests. The results show that the energy of the hybrid welding process is focused, and the power density of hybrid welding process is intense. The heat input per unit of the hybrid welding process is only half of that of the MIG welding process. Compared with the MIG welded joint, the overall residual stress level of the hybrid-welded joint is lower. The peak longitudinal stress of the hybrid-welded joint is reduced by 20 pct. The fatigue strength of hybrid joints is 14 pct higher than that of MIG-welded joints. Narrow weld and HAZ, weak softening behavior, and low residual stress level are the causes of the improvement of fatigue strength.

  12. Fatigue

    MedlinePlus

    Bennett RM. Fibromyalgia, chronic fatigue syndrome, and myofascial pain. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine . 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 274. Thames TA, Karrh ...

  13. Impact of longus colli muscle massage on the strength and endurance of the deep neck flexor muscle of adults.

    PubMed

    Gong, Wontae

    2013-05-01

    [Purpose] The purpose of the present study was to examine the effects of longus colli muscle massage on the strength and endurance of the deep neck flexor muscle in adults. [Subjects] A total of 60 subjects were divided into an experimental group of 30 subjects and a control group of 30 subjects. [Methods] The experimental group received massage of the longus colli muscle, which is the deep neck flexor muscle, and the control group received superficial neck muscle massage. The strength and endurance of both the experimental group and the control group were measured before and after the intervention using a pressure biofeedback unit (PBU). [Results] After the experiment, the strength of DNF of the experimental group showed a statistically significant increase, and the endurance of DNF of the experimental group showed an increase in its average value. The independent sample t-test revealed no statistically significant differences in the groups. [Conclusion] Massage of the longus colli muscle, which is the deep neck flexor, was shown to improve its strength and endurance, which are measures of neck stabilization. Therefore, longus colli muscle massage can be performed for patients who cannot perform neck-stabilizing exercises or before performing other neck-stabilizing exercises.

  14. 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

  15. Phosphorylase re-expression, increase in the force of contraction and decreased fatigue following notexin-induced muscle damage and regeneration in the ovine model of McArdle disease.

    PubMed

    Howell, J McC; Walker, K R; Creed, K E; Dunton, E; Davies, L; Quinlivan, R; Karpati, G

    2014-02-01

    McArdle disease is caused by a deficiency of myophosphorylase and currently a satisfactory treatment is not available. The injection of notexin into, or the layering of notexin onto, the muscles of affected sheep resulted in necrosis followed by regeneration of muscle fibres with the expression of both non-muscle isoforms of phosphorylase within the fibres and a reduction of the amount of glycogen in the muscle with an increase in the strength of contraction and a decrease in fatiguability in the muscle fibres. The sustained re-expression of both the brain and liver isoforms of phosphorylase within the muscle fibres provides further emphasis that strategies to enhance the re-expression of these isoforms should be investigated as a possible treatment for McArdle disease.

  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. Handgrip strength dominance is associated with difference in forearm muscle size.

    PubMed

    Abe, Takashi; Loenneke, Jeremy P

    2015-07-01

    [Purpose] It is unknown whether handgrip strength dominance is related to the size of the forearm flexor muscles. The purpose of the present study was to investigate the relationship between side-by-side differences in handgrip strength and forearm muscle thickness. [Subjects] Thirty-one young women (26 right handed and 5 left handed) between the ages of 20 and 33 years volunteered to participate. [Methods] Two muscle thicknesses (forearm-ulna and forearm-radius muscle thicknesses) were measured using B-mode ultrasound at the anterior forearm on both sides of the body. Handgrip strength was also measured on both sides. [Results] The side-by-side difference in handgrip strength was 10.2% for the right-handed group, meaning the right hand was stronger. However, the left hand of the left-handed group was 7.8% stronger compared with their right hand. There was a significant positive correlation between side-by-side differences in handgrip strength and forearm-ulna muscle thickness (r = 0.765) and between handgrip strength and forearm-radius muscle thickness (r = 0.622). [Conclusion] Our results indicate that side-by-side differences in forearm muscle size may strongly contribute to handgrip strength dominance.

  18. 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

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

    PubMed

    Moon, Young-Wan; Kim, Hyun-Jung; 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.

  1. Effect of nutritional interventions and resistance exercise on aging muscle mass and strength.

    PubMed

    Candow, Darren G; Forbes, Scott C; Little, Jonathan P; Cornish, Stephen M; Pinkoski, Craig; Chilibeck, Philip D

    2012-08-01

    Sarcopenia, defined as the age-related loss of muscle mass, has a negative effect on strength, functional independence and overall quality of life. Sarcopenia is a multifactorial phenomenon characterized by changes in muscle morphology, protein and hormonal kinetics, oxidative stress, inflammation, physical activity and nutrition. It is well known that resistance exercise increases aging muscle mass and strength and these physiological adaptations from exercise may be further enhanced with certain nutritional interventions. Research indicates that essential amino acids and milk-based proteins, creatine monohydrate, essential fatty acids, and vitamin D may all have beneficial effects on aging muscle biology. PMID:22684187

  2. 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

  3. 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).

  4. 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…

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

    PubMed

    Ferrari, Renata; Caram, Laura M O; 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.

  6. 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

  7. 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

  8. 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

  9. Vitamin D and muscle strength throughout the life course: a review of epidemiological and intervention studies.

    PubMed

    McCarthy, E K; Kiely, M

    2015-12-01

    The putative role of vitamin D in muscle function and strength throughout the life course is of interest because muscle strength is required for engagement in physical activity at all ages. As vitamin D deficiency is widely reported in the population, especially in countries at high latitude, the potential importance of vitamin D in muscle function throughout life, and the potential impacts on growth and development, participation in physical activity, and effects on skeletal and cardio-metabolic health, comprise an important topic for discussion. This review provides an overview of muscle function and summarises the role of the vitamin D receptor and the proposed molecular mechanisms of action of vitamin D in muscle cells. In addition, the review provides a comprehensive assessment of the clinical evidence surrounding the association between vitamin D and muscle strength. Among adults, particularly older adults, cross-sectional and cohort studies reported a positive association between vitamin D status and muscle strength. These associations have been largely confirmed by intervention studies. Limited research has been carried out in adolescents and children; two cross-sectional studies in adolescents have suggested an association between serum 25-hydroxyvitamin D concentrations and muscle strength. However, the two intervention studies in adolescents have yielded conflicting results. Other than a single observational study, data in young children are very limited and further investigation in under 12-year-olds is warranted.

  10. Cycle training induces muscle hypertrophy and strength gain: strategies and mechanisms.

    PubMed

    Ozaki, Hayao; Loenneke, J P; Thiebaud, R S; Abe, T

    2015-03-01

    Cycle training is widely performed as a major part of any exercise program seeking to improve aerobic capacity and cardiovascular health. However, the effect of cycle training on muscle size and strength gain still requires further insight, even though it is known that professional cyclists display larger muscle size compared to controls. Therefore, the purpose of this review is to discuss the effects of cycle training on muscle size and strength of the lower extremity and the possible mechanisms for increasing muscle size with cycle training. It is plausible that cycle training requires a longer period to significantly increase muscle size compared to typical resistance training due to a much slower hypertrophy rate. Cycle training induces muscle hypertrophy similarly between young and older age groups, while strength gain seems to favor older adults, which suggests that the probability for improving in muscle quality appears to be higher in older adults compared to young adults. For young adults, higher-intensity intermittent cycling may be required to achieve strength gains. It also appears that muscle hypertrophy induced by cycle training results from the positive changes in muscle protein net balance.

  11. 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

  12. Central fatigue of the first dorsal interosseous muscle during low-force and high-force sustained submaximal contractions.

    PubMed

    Eichelberger, Tamara D; Bilodeau, Martin

    2007-09-01

    The aim of this study was to compare the extent of central fatigue in the first dorsal interosseous (FDI) muscle of healthy adults in low, moderate and high-force submaximal contractions. Nine healthy adults completed four experimental sessions where index finger abduction force was recorded during voluntary contractions and in response to brief trains (five pulses at 100 Hz) of electrical stimulation. The ability to maximally activate FDI under volition, or voluntary activation, and its change with sustained activity (central fatigue) was assessed using the twitch interpolation technique. The fatigue tasks consisted of continuous isometric index finger abduction contractions held until exhaustion at four target force levels: 30%, 45%, 60% and 75% of the maximal voluntary contraction. The main finding was the presence of central fatigue for the 30% task, but not for the three other fatigue tasks. The extent of central fatigue was also associated with changes in a measure reflecting the status of peripheral structures/mechanisms. It appears that central fatigue contributed to task failure for the lowest force fatigue task (30%), but not for the other (higher) contraction intensities.

  13. Fatigue and fracture behavior of high strength and high conductivity copper alloys for high heat flux applications

    NASA Astrophysics Data System (ADS)

    Li, Meimei

    High strength, high conductivity copper alloys are candidate materials for high heat flux applications in fusion systems. In these applications, copper alloys must withstand exposure in extreme irradiation and thermal conditions. Most studies have concentrated on the influence of temperature, environment, irradiation exposure and microstructure on tensile properties. Relatively few studies have been performed on fatigue and fracture behavior of these alloys. This work aims to characterize and understand fracture, fatigue and creep-fatigue for three copper alloys, dispersion-strengthened CuAl25, and precipitation-hardened CuCrZr and CuNiBe. The role of temperature and environment on the fracture behavior of copper alloys was examined in vacuum between 20 and 300°C. This was accomplished through mechanical tests, microstructural examination and in-situ TEM straining experiments. The results showed that all three copper alloys experienced a loss of fracture resistance at elevated temperatures. Environment is not the single, or even most important, factor contributing to poor toughness at high temperatures. The evaluation of fracture mechanisms revealed that grain boundaries have a significant impact on the fracture behavior of copper alloys. The influence of irradiation on the fatigue behavior of two selected copper alloys, CuAl25 and CuCrZr, was evaluated. The fatigue lives were estimated from tensile properties using the Universal Slopes method. It was found that the influence of irradiation on fatigue performance was not as severe as on tensile properties. The Universal Slopes method provides a reasonable prediction of fatigue response for most unirradiated and irradiated conditions. The fatigue performance of CuAl25 and CuCrZr and OFHC copper was also evaluated under creep-fatigue loading conditions. It was found that creep and stress relaxation have a major impact on fatigue behavior. Fatigue lives were reduced notably with hold time even at room temperature

  14. Mechanisms underlying muscle fatigue differ between multiple sclerosis patients and controls: a combined electrophysiological and neuroimaging study.

    PubMed

    Steens, A; Heersema, D J; Maurits, N M; Renken, R J; Zijdewind, I

    2012-02-15

    Increased sense of fatigue is an important and conspicuous symptom in multiple sclerosis (MS). Muscle fatigue is associated with increased sense of fatigue in MS (Steens et al., 2011). The aim of this study was to investigate mechanisms that can explain muscle fatigue in MS patients and controls. We assessed changes in cortical activation (BOLD), voluntary activation (twitch interpolation) and muscle force during a sustained maximal voluntary contraction (MVC) in twenty MS patients and twenty healthy controls. In control participants, individual differences in force decline (mean 65% MVC, 8 SD) during the sustained maximal contraction could be accounted for by differences in maximal voluntary force (R(2): 0.49, p = 0.001); stronger participants presented a larger force decline. The small decline in voluntary activation (mean 7.8%, 11.8 SD) did not contribute significantly to the force decline. During the sustained contraction, the force decline was accompanied by an increase in cortical activation in the main motor areas. In MS patients, the differences in the decline in force (mean 67% MVC, 9 SD) were significantly associated (R(2): 0.51, p = 0.001) with a decline in voluntary activation (mean 20.1%, 20.6 SD) and not with maximal force or decline in rest twitch. The corresponding cortical activation in motor areas showed an increase in the first two intervals of the sustained contraction but declined during the last interval. Our data indicate that muscle fatigue during a sustained contraction in MS patients is associated with changes in the voluntary activation that are not sufficiently compensated by increased cortical activation. Control participants, however, show increased cortical activation to compensate for these fatigue-related changes in voluntary activation and the major cause of force decline is therefore to be found in the periphery (muscles).

  15. Responsiveness of muscle size and strength to physical training in very elderly people: a systematic review.

    PubMed

    Stewart, V H; Saunders, D H; Greig, C A

    2014-02-01

    The purpose of this review was to determine whether very elderly muscle (>75 years) hypertrophies in response to physical training. The databases MEDLINE; EMBASE; CINAHL Plus and SPORTDiscus were systematically literature searched with reference lists of all included studies and relevant reviews. Controlled trials (inactive elderly control group) involving healthy elderly participants over 75 years participating in an intervention complying with an established definition of physical training were included. Data extraction and quality assessment were performed using the PEDro scale. Data analysis was performed on muscle size and strength using RevMan (software version 5.1). Four studies were included of which four of four measured changes in gross muscle size. Training induced increases in muscle size from 1.5%-15.6% were reported in three of four studies, and one of four studies reported a decrease in muscle size (3%). The greatest gain in muscle mass was observed in a study of whole body vibration training. Meta-analysis of three studies found an increase of thigh muscle cross-sectional area (mean difference 2.31 cm(2) or 0.2%, 95% confidence interval (CI): 0.62 to 4.00; P = 0.008) and muscle strength (standardized mean difference 1.04, 95% CI: 0.65 to 1.43; P < 0.001). Physical training when delivered as resistance training has the ability to elicit hypertrophy and increase muscle strength in very elderly muscle.

  16. 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.

  17. The relationship between lower-limb strength and match-related muscle damage in elite level professional European soccer players.

    PubMed

    Owen, Adam; Dunlop, Gordon; Rouissi, Mehdi; Chtara, Moktar; Paul, Darren; Zouhal, Hassane; Wong, Del P

    2015-01-01

    In professional soccer, the benefits of lower limb strength training have been advocated. However, from an aspect of performance development, specifically with respect to expression of fatigue and injury prevention, the advantages of increased lower body strength have received limited attention at the elite level of the game. The primary aim of this cross-sectional investigation was to examine the association between lower body strength and the expression of markers of fatigue as evaluated through muscle damage assessment following match play in professional soccer players. Ten male professional soccer players participated in this investigation (mean ± SD age 26.2 ± 4.3 years, height 181.6 ± 4.8 cm and body mass 78.7 ± 6.1 kg); creatine kinase (CK) was collected 2-days post-match for a 5-month period and at three different time points (Phase 1, Phase 2 and Phase 3); muscular strength (e.g. 4 repetition half-squat) was measured 3-day post-match. No significant change in CK and muscular force across three time points was found (F = 0.60, P = 0.56, η(2) = 0.06 and F = 2.65, P = 0.10, η(2) = 0.23, respectively). Muscular force was negatively correlated (moderate to very large) with CK. It can be concluded that players who produce greater lower body force as a result of being stronger in the lower limbs show reduced levels of CK 48 h post-match.

  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. 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

  20. Effects of some technological aspects on the fatigue strength of a cementless hip stem.

    PubMed

    Viceconti, M; Toni, A; Giunti, A

    1995-07-01

    Four prototype cementless hip stems were tested following the ISO 7206 protocol for the assessment of the endurance properties and compared with a cast Cr-Co-Mo (ASTM F75) commercially available stem which was used as reference design. All the tested stems were similar in shape and size, but with some substantial differences. The first was made of forged Ti6A14V alloy (ASTM F136). The second, made of the same material, featured a central hole intended to reduce the bending stiffness of the stem itself. The third was identical to the second but for a small tooling notch in one of the fillets of the hole. The fourth was similar to the first but had a coating of sintered titanium beads in the proximal part. All of these modifications were made to evaluate the effect of fatigue strength of intentional or unintentional features commonly found in commercial stems. The forged Ti6A14V allow was found to be substantially stronger than the cast ASTM F75 Cr-Co-Mo alloy. However, tooling notches or sintered coatings were found to dramatically reduce this strength. Thus, the Ti6A14V alloy calls for an accurate design process, especially when complex shapes or sintered structures are required.

  1. 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

  2. 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

  3. Addition of an anabolic steroid to strength training promotes muscle strength in the nonparetic lower limb of poststroke hemiplegia patients.

    PubMed

    Shimodozono, Megumi; Kawahira, Kazumi; Ogata, Atsuko; Etoh, Seiji; Tanaka, Nobuyuki

    2010-09-01

    In this prospective observer-blinded open-label nonrandomized controlled trial, 25 inpatients with hemiplegia 1-8 months after stroke were assigned to an anabolic androgenic steroid (AAS; n = 14) or a control (n = 11) group: the former received 100 mg metenolone enanthate by intramuscular injection once a week for 6 weeks along with rehabilitation therapy including muscle strength training of the nonparetic lower limb, which consisted of 100 repetitions of isokinetic reciprocal knee extension/flexion (60 degrees /s) on a dynamometer once a day for 5 days a week over 6 weeks, and the latter received rehabilitation therapy alone. The maximal peak torque of the nonparetic lower limb, including the isokinetic (60 degrees /s, 120 degrees /s, and 180 degrees /s), isotonic, and isometric muscle strength of knee extension/flexion, measured every 2 weeks, was compared with the baseline values. Significant increases in peak torque were seen at 2 weeks in 9 of the 10 conditions and at 6 weeks in 8 of the 10 conditions tested for the AAS group but in only 1 and 5 conditions for the control group, respectively. While no contraindications for AAS were encountered, the combination of AAS and muscle strength training tended to have a positive effect on muscle strength after stroke.

  4. 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 ...

  5. An investigation of the reduction in tensile strength and fatigue life of pre-corroded 7075-T6 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Obert, B.; Ngo, K.; Hashemi, J.; Ekwaro-Osire, S.; Sivam, T. P.

    2000-08-01

    In aging aircraft, the synergetic interaction between corrosion and fatigue has been shown to reduce the life expectancy of aluminum alloys. The objective of this study was to quantify the effects of corrosion, in terms of mass loss per unit area, on the static strength and fatigue life of 7075-T6 aluminum alloy. This was an experimental study in which test specimens were corroded in a laboratory environment. The corrosion process was accelerated by use of a corrosion cell. Test specimens were cut from flat sheets of aluminum and covered with masking material to restrict corrosion to a confined area. After testing, the fatigue life, ultimate tensile strength (UTS), and hardness of the specimens were observed to drop significantly with small amounts of corrosion. After the initial decrease, the UTS was observed to decrease linearly with increasing corrosion levels. The fatigue life of the specimens decreased in an inverse exponential fashion as mass loss per unit area increased. The hardness values of the corroded surfaces were also observed to drop. The topology of the pits and the related subsurface damage produced areas of high stress concentration resulting in the immediate reduction of UTS and fatigue life of the specimens. Subsurface corrosion damage was responsible for the reduction in hardness.

  6. Triphasic multinutrient supplementation during acute resistance exercise improves session volume load and reduces muscle damage in strength-trained athletes.

    PubMed

    Bird, Stephen P; Mabon, Tom; Pryde, Mitchell; Feebrey, Sarah; Cannon, Jack

    2013-05-01

    We hypothesized that triphasic multinutrient supplementation during acute resistance exercise would enhance muscular performance, produce a more favorable anabolic profile, and reduce biochemical markers of muscle damage in strength-trained athletes. Fifteen male strength-trained athletes completed two acute lower-body resistance exercise sessions to fatigue 7 days apart. After a 4-hour fast, participants consumed either a multinutrient supplement (Musashi 1-2-3 Step System, Notting Hill, Australia) (SUPP) or placebo (PLA) beverage preexercise (PRE), during (DUR), and immediately postexercise (IP). Session volume loads were calculated as kilograms × repetitions. Lower-body peak power was measured using unloaded repeated countermovement jumps, and blood samples were collected to assess biochemistry, serum hormones, and muscle damage markers at PRE, DUR, IP, 30 minutes postexercise (P30), and 24 hours postexercise (P24h). The SUPP demonstrated increased glucose concentrations at DUR and IP compared with at PRE (P < .01), whereas PLA demonstrated higher glucose at P30 compared with at PRE (P < .001). Session volume load was higher for SUPP compared with PLA (P < .05). Cortisol increased at DUR, IP, and P30 compared with at PRE in both treatments (P < .05); however, SUPP also displayed lower cortisol at P24h compared with at PRE and PLA (P < .01). The total testosterone response to exercise was higher for PLA compared with SUPP (P < .01); however, total creatine kinase and C-reactive protein responses to exercise were lower for SUPP compared with PLA (P < .05). These data indicate that although triphasic multinutrient supplementation did not produce a more favorable anabolic profile, it improved acute resistance exercise performance while attenuating muscle damage in strength-trained athletes.

  7. The effect of ankle muscle strength and flexibility on dolphin kick performance in competitive swimmers.

    PubMed

    Willems, Tine M; Cornelis, Justien A M; De Deurwaerder, Lien E P; Roelandt, Filip; De Mits, Sophie

    2014-08-01

    The velocity of a swimmer is determined by biomechanical and bioenergetics factors. However, little is known about the effect of ankle flexibility on dolphin kick performance. Next to this, scientific evidence is lacking concerning the influence of ankle muscle strength. Therefore, the aim of this study was to investigate the effect of ankle flexibility and muscle strength on dolphin kick performance in competitive swimmers. Ankle range of motion (ROM) and ankle muscle strength were measured in 26 healthy competitive swimmers. The effect of both was assessed on the swimmer's velocity and lower extremity joint angles during three maximal dolphin kick trials. Additionally, the effect of a flexibility restriction by a tape on the dolphin kick performance was assessed. Correlations were calculated between the flexibility, muscle strength and dolphin kick performance and differences were investigated between the unrestricted and restricted condition. Muscle strength of dorsal flexors and internal rotators were positively significantly correlated with the velocity. Active and passive plantar flexion ROM and internal rotation ROM were not significantly correlated. A plantar flexion-internal rotation restriction during the dolphin kick showed a significant decrease in velocity. This restriction was associated with a changed movement pattern in the knee towards more flexion. The results suggest that dolphin kick velocity might be enhanced by ankle muscle strength exercises and that subjects with a restricted ankle flexibility might profit from a flexibility program. PMID:24984154

  8. 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.

  9. Mechanisms of excitation-contraction uncoupling relevant to activity-induced muscle fatigue.

    PubMed

    Lamb, Graham D

    2009-06-01

    If the free [Ca2+] in the cytoplasm of a skeletal muscle fiber is raised substantially for a period of seconds to minutes or to high levels just briefly, it leads to disruption of the normal excitation-contraction (E-C) coupling process and a consequent long-lasting decrease in force production. It appears that the disruption to the coupling occurs at the triad junction, where the voltage-sensor molecules (dihydropyridine receptors) normally interact with and open the Ca2+ release channels (ryanodine receptors) in the adjacent sarcoplasmic reticulum (SR). This disruption results in inadequate release of SR Ca2+ upon stimulation. Such E-C uncoupling may underlie the long-duration low-frequency fatigue that can occur after various types of exercise, as well as possibly being a contributing factor to the muscle weakness in certain muscle diseases. The process or processes causing the disruption of the coupling between the voltage sensors and the release channels is not known with certainty, but might be associated with structural changes at the triad junction, possibly caused by activation of the Ca2+-dependent protease, micro-calpain.

  10. Evaluation of hamstring muscle strength and morphology after anterior cruciate ligament reconstruction.

    PubMed

    Nomura, Y; Kuramochi, R; Fukubayashi, T

    2015-06-01

    This study aimed to clarify the relationship between knee flexor strength and hamstring muscle morphology after anterior cruciate ligament (ACL) reconstruction using the semitendinosus (ST) tendon and to determine the causative factors of decreased knee flexor muscle strength. Fourteen male and ten female patients who resumed sports activities after surgery participated in the experiment. Isometric knee flexion torque was measured at 30°, 45°, 60°, 90°, and 105° of knee flexion. Magnetic resonance imaging (MRI) was used to calculate ST muscle length and hamstring muscle volume, and to confirm the status of ST tendon regeneration. The correlation between the MRI findings and flexor strength was analyzed. Regenerated ST tendon was confirmed in 21 of the 24 patients, but muscle volume (87.6%) and muscle length (74.5%) of the ST in the operated limb were significantly smaller than those in the normal limb. The percentage of the knee flexion torque of the operated limb compared with that of the normal was apparently lower at 105° (69.1%) and 90° (68.6%) than at 60° (84.4%). Tendon regeneration, ST muscle shortening, and ST muscle atrophy correlated with decreased knee flexion torque. These results indicated that preserving the morphology of the ST muscle-tendon complex is important.

  11. Shear elastic modulus can be used to estimate an index of individual muscle force during a submaximal isometric fatiguing contraction.

    PubMed

    Bouillard, Killian; Hug, François; Guével, Arnaud; Nordez, Antoine

    2012-11-01

    The present study was designed to determine whether fatigue alters the ability to estimate an index of individual muscle force from shear elastic modulus measurements (experiment I), and to test the ability of this technique to highlight changes in load sharing within a redundant muscle group during an isometric fatiguing task (experiment II). Twelve subjects participated in experiment I, which consisted of smooth linear torque ramps from 0 to 80% of maximal voluntary contraction (MVC) performed before and after an isometric fatigue protocol, beginning at 40% of MVC and stopped when the force production dropped below 30% of MVC. Although the relationships between modulus and torque were very similar for pre- and postfatigue [root mean square deviation (RMS(deviation)) = 3.7 ± 2.6% of MVC], the relationships between electromyography activity level and torque were greatly altered by fatigue (RMS(deviation) = 10.3 ± 2.6% of MVC). During the fatiguing contraction, shear elastic modulus provided a significantly lower RMS(deviation) between measured torque and estimated torque than electromyography activity level (5.7 ± 0.9 vs. 15.3 ± 3.8% of MVC). Experiment II performed with eight participants consisted of an isometric knee extension at 25% of MVC sustained until exhaustion. Opposite changes in shear elastic modulus were observed between synergists (vastus medialis, vastus lateralis, and rectus femoris) of some participants, reflecting changes in load sharing. In conclusion, despite the fact that we did not directly estimate muscle force (in Newtons), this is the first demonstration of an experimental technique to accurately quantify relative changes in force in an individual human muscle during a fatiguing contraction.

  12. Influence of exercise order on maximum strength and muscle volume in nonlinear periodized resistance training.

    PubMed

    Spineti, Juliano; de Salles, Belmiro Freitas; Rhea, Matthew R; Lavigne, Danielle; Matta, Thiago; Miranda, Fabrício; Fernandes, Liliam; Simão, Roberto

    2010-11-01

    The purpose of this study was to examine the influence of exercise order on strength and muscle volume (MV) after 12 weeks of nonlinear periodized resistance training. The participants were randomly assigned into 3 groups. One group began performing large muscle group exercises and progressed to small muscle group exercises (LG-SM), whereas another group started with small muscle group exercises and advanced to large muscle group exercises (SM-LG). The exercise order for LG-SM was bench press (BP), machine lat pull-down (LPD), triceps extension (TE), and biceps curl (BC). The order for the SM-LG was BC, TE, LPD, and BP. The third group did not exercise and served as a control group (CG). Training frequency was 2 sessions per week with at least 72 hours of rest between sessions. Muscle volume was assessed at baseline and after 6 weeks and 12 weeks of training by ultrasound techniques. One repetition maximum strength for all exercises was assessed at baseline and after 12 weeks of training. Effect size data demonstrated that differences in strength and MV were exhibited based on exercise order. Both training groups demonstrated greater strength improvements than the CG, but only BP strength increased to a greater magnitude in the LG-SM group as compared with the SM-LG. In all other strength measures (LPD, TE, and BC), the SM-LG group showed significantly greater strength increases. Triceps MV increased in the SM-LG group; however, biceps MV did not differ significantly between the training groups. In conclusion, if an exercise is important for the training goals of a program, then it should be placed at the beginning of the training session, regardless of whether or not it is a large muscle group exercise or a small muscle group exercise.

  13. Fatigue during high-intensity intermittent exercise: application to bodybuilding.

    PubMed

    Lambert, Charles P; Flynn, Michael G

    2002-01-01

    Resistance exercise is an activity performed by individuals interested in competition, those who wish to improve muscle mass and strength for other sports, and for individuals interested in improving their strength and physical appearance. In this review we present information suggesting that phosphocreatine depletion, intramuscular acidosis and carbohydrate depletion are all potential causes of the fatigue during resistance exercise. In addition, recommendations are provided for nutritional interventions, which might delay muscle fatigue during this type of activity.

  14. 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

  15. 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

  16. No Decrease in Muscle Strength after Botulinum Neurotoxin-A Injection in Children with Cerebral Palsy

    PubMed Central

    Eek, Meta N.; Himmelmann, Kate

    2016-01-01

    Spasticity and muscle weakness is common in children with cerebral palsy (CP). Spasticity can be treated with botulinum neurotoxin-A (BoNT-A), but this drug has also been reported to induce muscle weakness. Our purpose was to describe the effect on muscle strength in the lower extremities after BoNT-A injections in children with CP. A secondary aim was to relate the effect of BoNT-A to gait pattern and range of motion. Twenty children with spastic CP were included in the study, 8 girls and 12 boys (mean age 7.7 years). All were able to walk without support, but with increased muscle tone interfering with motor function and gait pattern. Sixteen children had unilateral spastic CP and four bilateral spastic CP. Twenty-four legs received injections with BoNT-A in the plantar flexor muscles. The children were tested before treatment, around 6 weeks after at the peak effect of BoNT-A, and at 6 months after treatment, with measurement of muscle strength, gait analysis, and range of motion. There were no differences in muscle strength in plantar flexors of treated legs at peak effect compared to baseline. Six months after treatment, there was still no change in untreated plantar flexor muscles, but an increasing trend in plantar flexor strength in legs treated with BoNT-A. Parents reported positive effects in all children, graded as: small in three children, moderate in eight, and large in nine children. The gait analysis showed a small improvement in knee extension at initial contact, and there was a small increase in passive range of motion for ankle dorsiflexion. Two children had a period with transient weakness and pain. We found that voluntary force production in plantar flexor muscles did not decrease after BoNT-A, instead there was a trend to increased muscle strength at follow-up. The increase may be explained as an effect of the blocking of involuntary nerve impulses, leading to an opportunity to using and training the muscles with voluntary control. Adequate

  17. Simulation of post-tetanic potentiation and fatigue in muscle using a visco-elastic model.

    PubMed

    Ducati, A; Parmiggiani, F; Schieppati, M

    1982-01-01

    Post-tetanic potentiation (PTP) in single motor units was simulated using a simple visco-elastic model. Single isometric twitches and unfused tetani were obtained using a wide range of physiological input rates. Values of model parameters were chosen to simulate contraction times close to those of fast and slow muscle fibers. PTP has been attributed either to i) an augmented plateau level of active state or ii) an increase in time constant of active state decay. Our results show that a prolonged decay time of active state can account for most of the experimental data obtained in amphibian and mammalian preparations. In particular, potentiation is more marked in unfused tetani than in single twitches. Moreover the model accounts for PTP even in the case of a reduction of active state plateau due to fatigue.

  18. Effects of Different Environment Temperatures on Some Motor Characteristics and Muscle Strength

    ERIC Educational Resources Information Center

    Çakir, Ergün; Yüksek, Selami; Asma, Bülent; Arslanoglu, Erkal

    2016-01-01

    The aim of this study was determine the effects of different environment temperatures on motor characteristics and muscle strength. 15 athletes participated to study. Flexibility, vertical jump, hand grip-leg strength, 30m sprint, 20-meter shuttle run and coordination-agility tests were measured in five different environment temperatures. (22°C,…

  19. Fatigue in repeated-sprint exercise is related to muscle power factors and reduced neuromuscular activity.

    PubMed

    Mendez-Villanueva, Alberto; Hamer, Peter; Bishop, David

    2008-07-01

    The purpose of this study was (1) to determine the relationship between each individual's anaerobic power reserve (APR) [i.e., the difference between the maximum anaerobic (Pana) and aerobic power (Paer)] and fatigability during repeated-sprint exercise and (2) to examine the acute effects of repeated sprints on neuromuscular activity, as evidenced by changes in the surface electromyogram (EMG) signals. Eight healthy males carried out tests to determine Pana (defined as the highest power output attained during a 6-s cycling sprint), Paer (defined as the highest power output achieved during a progressive, discontinuous cycling test to failure) and a repeated cycling sprint test (10 x 6-s max sprints with 30 s rest). Peak power output (PPO) and mean power output (MPO) were calculated for each maximal 6-s cycling bout. Root mean square (RMS) was utilized to quantify EMG activity from the vastus lateralis (VL) muscle of the right leg. Over the ten sprints, PPO and MPO decreased by 24.6 and 28.3% from the maximal value (i.e., sprint 1), respectively. Fatigue index during repeated sprints was significantly correlated with APR (R = 0.87; P < 0.05). RMS values decreased over the ten sprints by 14.6% (+/-6.3%). There was a strong linear relationship (R2 = 0.97; P < 0.05) between the changes in MPO and EMG RMS from the vastus lateralis muscle during the ten sprints. The individual advantage in fatigue-resistance when performing a repeated sprint task was related with a lower anaerobic power reserve. Additionally, a suboptimal net motor unit activity might also impair the ability to repeatedly generate maximum power outputs.

  20. Fatigue is specific to working muscles: no cross-over with single-leg cycling in trained cyclists.

    PubMed

    Elmer, Steven J; Amann, Markus; McDaniel, John; Martin, David T; Martin, James C

    2013-02-01

    Fatigue induced via a maximal isometric contraction of a single limb muscle group can evoke a "cross-over" of fatigue that reduces voluntary muscle activation and maximum isometric force in the rested contralateral homologous muscle group. We asked whether a cross-over of fatigue also occurs when fatigue is induced via high-intensity endurance exercise involving a substantial muscle mass. Specifically, we used high-intensity single-leg cycling to induce fatigue and evaluated associated effects on maximum cycling power (P (max)) in the fatigued ipsilateral leg (FAT(leg)) as well as the rested contralateral leg (REST(leg)). On separate days, 12 trained cyclists performed right leg P (max) trials before and again 30 s, 3, 5, and 10 min after a cycling time trial (TT, 10 min) performed either with their right or left leg. Fatigue was estimated by comparing exercise-induced changes in P (max) and maximum handgrip isometric force (F (max)). Mean power produced during the right and left leg TTs did not differ (203 ± 8 vs. 199 ± 8 W). Compared to pre-TT, FAT(leg) P (max) was reduced by 22 ± 3 % at 30 s post-TT and remained reduced by 9 ± 2 % at 5 min post-TT (both P < 0.05). Despite considerable power loss in the FAT(leg), post-TT REST(leg) P (max) (596-603 W) did not differ from pre-TT values (596 ± 35 W). There were no alterations in handgrip F (max) (529-547 N). Our data suggest that any potential cross-over of fatigue, if present at all, was not sufficient to measurably compromise REST(leg) P (max) in trained cyclists. These results along with the lack of changes in handgrip F (max) indicate that impairments in maximal voluntary neuromuscular function were specific to working muscles.

  1. 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

  2. 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.

  3. Application of perineometer in the assessment of pelvic floor muscle strength and endurance: a reliability study.

    PubMed

    Rahmani, Nahid; Mohseni-Bandpei, Mohammad A

    2011-04-01

    Despite different studies on the reliability of pelvic floor muscle assessment, there is still no general consensus on the most valid and reliable method. The purpose of this study was to investigate the intra-rater (within-day and between-days) reliability of perineometer in the assessment of pelvic floor muscle strength and endurance. Following ethical approval, 15 healthy women aged from 22 to 50-years old, with no history of low back pain were recruited. The Peritron perineometer instrument was used to measure pelvic floor muscle strength and endurance. Two measurements were taken on the same day with an hour interval to assess within-day reliability and the third measurement was taken five days later to determine between-days reliability. Intraclass Correlation Coefficients (ICCs) and the level of agreement between measurements were used for data analysis. The high ICC values (0.95 for strength and 0.94 for endurance) and high level of agreement between measurements indicated high within-day reliability for pelvic floor muscle strength and endurance. The perineometer was also shown to be reliable for between-days measurements with high ICC (0.88 for strength and 0.83 for endurance) and high level of agreement between measurements. The results demonstrated that the perineometer appears to be a highly reliable method of measuring pelvic floor muscle strength and endurance when measurements are taken in healthy subject by the same investigator.

  4. Association of insulin sensitivity and muscle strength in overweight and obese sedentary postmenopausal women.

    PubMed

    Karelis, Antony D; Tousignant, Benoit; Nantel, Julie; Proteau-Labelle, Majorique; Malita, Florin M; St-Pierre, David H; Brochu, Martin; Doucet, Eric; Rabasa-Lhoret, Rémi

    2007-04-01

    The objective of this study was to examine the relationship between insulin sensitivity and lower body muscle strength in overweight and obese sedentary postmenopausal women. The design of the study was cross-sectional. The study population consisted of 82 non-diabetic overweight and obese sedentary postmenopausal women (age: 58.2 +/- 5.1 y; body mass index (BMI): 32.4 +/- 4.6 kg.m-2). Subjects were classified by dividing the entire cohort into quartiles based on relative insulin sensitivity expressed per kilograms of lean body mass (LBM) (Q1, < 10.3, vs. Q2, 10.3-12.4, vs. Q3, 12.5-14.0, vs. Q4, >14.0 mg.min-1.kg LBM-1). We measured insulin sensitivity (using the hyperinsulinemic-euglycemic clamp technique), body composition (using dual-energy X-ray absorptiometry), visceral fat and muscle attenuation (using computed tomography), and a lower-body muscle strength index expressed as weight lifted in kilograms per kilogram of LBM (kg.kg LBM-1) (using weight-training equipment). A positive and significant relationship was observed between insulin sensitivity and the muscle strength index (r = 0.37; p < 0.001). Moreover, a moderate but significant correlation was observed between the muscle strength index and muscle attenuation (r = 0.22; p < 0.05). Finally, the muscle strength index was significantly higher in the Q4 group compared with the Q2 and Q1 groups, respectively (3.78 +/- 1.13 vs. 2.99 +/- 0.77 and 2.93 +/- 0.91 kg.kg LBM-1; p < 0.05). Insulin sensitivity is positively associated with lower-body muscle strength in overweight and obese sedentary postmenopausal women.

  5. 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

  6. 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.

  7. 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.

  8. Myocytic androgen receptor controls the strength but not the mass of limb muscles.

    PubMed

    Chambon, Céline; Duteil, Delphine; Vignaud, Alban; Ferry, Arnaud; Messaddeq, Nadia; Malivindi, Rocco; Kato, Shigeaki; Chambon, Pierre; Metzger, Daniel

    2010-08-10

    The anabolic effects of androgens on skeletal muscles are thought to be mediated predominantly through the androgen receptor (AR), a member of the ligand-dependent nuclear receptor superfamily. However, despite numerous studies performed in men and in rodents, these effects remain poorly understood. To characterize androgen signaling in skeletal muscles, we generated mice in which the AR is selectively ablated in myofibers. We show that myocytic AR controls androgen-induced insulin-like growth factor IEa (IGF-IEa) expression in the highly androgen-sensitive perineal muscles and that it mediates androgen-stimulated postnatal hypertrophy of these muscles. In contrast, androgen-dependent postnatal hypertrophy of limb muscle fibers is independent of myocytic AR. Thus, androgens control perineal and limb muscle mass in male mice through myocytic AR-dependent and -independent pathways, respectively. Importantly, we also show that AR deficiency in limb myocytes impairs myofibrillar organization of sarcomeres and decreases muscle strength, thus demonstrating that myocytic AR controls key pathways required for maximum force production. These distinct androgen signaling pathways in perineal and limb muscles may allow the design of screens to identify selective androgen modulators of muscle strength.

  9. Comparison of toe grip strength and muscle activities during maximal toe grip strength exertion according to the presence/absence of an ankle immobilization belt.

    PubMed

    Soma, Masayuki; Murata, Shin; Kai, Yoshihiro; Nakae, Hideyuki; Satou, Yousuke; Murata, Jun; Miyazaki, Junya

    2015-10-01

    [Purpose] The aim of this study was to compare toe grip strength and muscle activity during toe grip strength exertion according to the presence/absence of an ankle immobilization belt and to examine the relationship between the differences in muscle activity and toe grip strength. [Subjects] The Subjects were 13 healthy young women. [Methods] We measured toe grip strength and muscle activity during toe grip strength exertion in the presence and absence of an ankle immobilization belt using electromyography. Activity in the following leg muscles was recorded: rectus femoris, biceps femoris, medial head of the gastrocnemius, and tibialis anterior. We then calculated the percent integrated electromyography during toe gripping. [Results] Toe grip strength and percent integrated electromyography of the medial head of the gastrocnemius muscle were significantly higher with ankle belt immobilization compared with without ankle belt immobilization. In addition, in the presence of ankle belt immobilization, the percent integrated electromyography of the tibialis anterior muscle and medial head of the gastrocnemius muscle demonstrated a positive correlation with toe grip strength (r = 0.75 and r = 0.65, respectively). [Conclusion] These findings suggest that greater toe grip strength could be exerted in the presence of ankle belt immobilization. The measured values reflect the percent integrated electromyography of the crural muscles. Therefore, it was shown that toe grip strength should be measured in the presence of an immobilization belt.

  10. Muscle fiber conduction velocity and fractal dimension of EMG during fatiguing contraction of young and elderly active men.

    PubMed

    Boccia, Gennaro; Dardanello, Davide; Beretta-Piccoli, Matteo; Cescon, Corrado; Coratella, Giuseppe; Rinaldo, Nicoletta; Barbero, Marco; Lanza, Massimo; Schena, Federico; Rainoldi, Alberto

    2016-01-01

    Over the past decade, linear and nonlinear surface electromyography (EMG) variables highlighting different components of fatigue have been developed. In this study, we tested fractal dimension (FD) and conduction velocity (CV) rate of changes as descriptors, respectively, of motor unit synchronization and peripheral manifestations of fatigue. Sixteen elderly (69  ±  4 years) and seventeen young (23  ±  2 years) physically active men (almost 3-5 h of physical activity per week) executed one knee extensor contraction at 70% of a maximal voluntary contraction for 30 s. Muscle fiber CV and FD were calculated from the multichannel surface EMG signal recorded from the vastus lateralis and medialis muscles. The main findings were that the two groups showed a similar rate of change of CV, whereas FD rate of change was higher in the young than in the elderly group. The trends were the same for both muscles. CV findings highlighted a non-different extent of peripheral manifestations of fatigue between groups. Nevertheless, FD rate of change was found to be steeper in the elderly than in the young, suggesting a greater increase in motor unit synchronization with ageing. These findings suggest that FD analysis could be used as a complementary variable providing further information on central mechanisms with respect to CV in fatiguing contractions.

  11. 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 fi