AIM： To evaluate the myoelectric manifestations of peripheral fatigability in patients with primary biliary cirrhosis in comparison to healthy subjects. METHODS： Sixteen women with primary biliary cirrhosis without ...AIM： To evaluate the myoelectric manifestations of peripheral fatigability in patients with primary biliary cirrhosis in comparison to healthy subjects. METHODS： Sixteen women with primary biliary cirrhosis without comorbidity and 13 healthy women matched for age and body mass index （BMI） completed the selfreported questionnaire fatigue impact scale. All subjects underwent surface electromyography assessment of peripheral fatigability. Anterior tibial muscle isometric voluntary contraction was executed for 20 s at 80% of maximal voluntary isometric contraction. During the exercise electromyographic signal series were recorded and root mean square （expression of central drive） as well as mean and median of electromyographic signal frequency spectrum （estimates of muscle fatigability） were com- puted. Each subject executed the trial two times. EMG parameters were normalized, then linear regression was applied and slopes were calculated. RESULTS： Seven patients were fatigued （median fatigue impact scale score： 38, range： 26-66） and 9 were not fatigued （median fatigue impact scale score： 7, range： 0-17）. The maximal voluntary isometric contraction was similar in patients （82, 54-115 N） and controls （87, 74-101 N）, and in patients with high （81, 54-115 N） and low fatigue impact scale scores （86, 65-106 N）. Root mean square as well as mean and median of frequency spectrum slopes were compared with the Mann-Whitney U test, and no significant difference was found between fatigued and non-fatigued patients and controls. CONCLUSION： No instrumental evidence of peripheral fatigability can be found in women with primary biliary cirrhosis but no comorbidity, suggesting that fatigue in such patients may be of central origin.展开更多
Background: Attractor-based kinematic gait analysis using the Fatigue Index Kliniken Schmieder (FKS), have been suggested as a sensitive tool to determine motor fatigability in persons with Multiple Sclerosis (pwMS). ...Background: Attractor-based kinematic gait analysis using the Fatigue Index Kliniken Schmieder (FKS), have been suggested as a sensitive tool to determine motor fatigability in persons with Multiple Sclerosis (pwMS). Hypothesis: Depression does not affect the FKS to a similar degree as in pwMS. Methods: We recruited 32 patients with major depression. Data were collected with two accelerometers attached to both ankles. Data were recorded for one minute at the beginning and at the end of the treadmill test. Attractor attributes were used to analyze the data. Results: The mean Fatigue Index Kliniken Schmieder (FKS) was 2.1. The change of the attractor (δM) was 3.7 and the change of variability (δD) was 0.6. Mean values were clearly below values of pwMS with fatigability from a previous publication. However, the individual level values from six individuals—five of them showed pain related comorbidity besides depression—fell within the lower pathological range. There was no correlation between Hamilton depression scale and the attractor attributes (δM and δD). Discussion: Depression does not affect gait as motor fatigability does in pwMS. Results from subjects with pain during the treadmill test show a moderately increased variability and moderately altered attractors.展开更多
Muscle unloading due to long-term exposure of weightlessness or simulated weightlessness causes atrophy, loss of functional capacity, impaired locomotor coordination, and decreased resistance to fatigue in the antigra...Muscle unloading due to long-term exposure of weightlessness or simulated weightlessness causes atrophy, loss of functional capacity, impaired locomotor coordination, and decreased resistance to fatigue in the antigravity muscles of the lower limbs. Besides reducing astronauts' mobility in space and on returning to a gravity environment, the molecular mechanisms for the adaptation of skeletal muscle to unloading also play an important medical role in conditions such as disuse and paralysis. The tail-suspended rat model was used to simulate the effects of weightlessness on skeletal muscles and to induce muscle unloading in the rat hindlimb. Our series studies have shown that the maximum of twitch tension and the twitch duration decreased significantly in the atrophic soleus muscles, the maximal tension of high-frequency tetanic contraction was significantly reduced in 2-week unloaded soleus muscles, however, the fatigability of highfrequency tetanic contraction increased after one week of unloading. The maximal isometric tension of intermittent tetanic contraction at optimal stimulating frequency did not alter in 1-and 2-week unloaded soleus, but significantly decreased in 4-week unloaded soleus. The 1-week unloaded soleus, but not extensor digitorum longus(EDL), was more susceptible to fatigue during intermittent tetanic contraction than the synchronous controls. The changes in K+ channel characteristics may increase the fatigability during high-frequency tetanic contraction in atrophic soleus muscles. High fatigability of intermittent tetanic contraction may be involved in enhanced activity of sarcoplasmic reticulum Ca2+-ATPase(SERCA) and switching from slow to fast isoform of myosin heavy chain, tropomyosin, troponin I and T subunit in atrophic soleus muscles. Unloaded soleus muscle also showed a decreased protein level of neuronal nitric oxide synthase(nNOS), and the reduction in nNOS-derived NO increased frequency of calcium sparks and elevated intracellular resting Ca2+ concentration([Ca2+]i) in unloaded soleus muscles. High [Ca2+]i activated calpain-1 which induced a higher degradation of desmin. Desmin degradation may loose connections between adjacent myofibrils and further misaligned Z-disc during repeated tetanic contractions. Passive stretch in unloaded muscle could preserve the stability of sarcoplasmic reticulum Ca2+ release channels by means of keeping nNOS activity, and decrease the enhanced protein level and activity of calpain to control levels in unloaded soleus muscles. Therefore, passive stretch restored normal appearance of Z-disc and resisted in part atrophy of unloaded soleus muscles. The above results indicate that enhanced fatigability of high-frequency tetanic contraction is associated to the alteration in K+ channel characteristics, and elevated SERCA activity and slow to fast transition of myosin heavy chain(MHC) isoforms increases fatigability of intermittent tetanic contraction in atrophic soleus muscle. The sarcomeric damage induced by tetanic contraction can be retarded by stretch in atrophic soleus muscles.展开更多
Purpose The purpose of the present study was to examine the day-to-day consistency and inter-subject variability of com-posite and individual,neuromuscular and torque patterns of responses as a result of a fatiguing b...Purpose The purpose of the present study was to examine the day-to-day consistency and inter-subject variability of com-posite and individual,neuromuscular and torque patterns of responses as a result of a fatiguing bout of maximal,bilateral,isokinetic leg extension muscle actions.Methods Ten men (Mean ± SD =21.6 ± 2.5 years) completed two testing visits consisting of pretest and posttest maximal voluntary isometric contractions (MVIC) as well as 25 maximal,bilateral,isokinetic (180°/s),leg extension muscle actions.Electromyographic (EMG) and mechanomyographic (MMG) signals were collected from the vastus lateralis and normalized to the MVIC.Performance fatigability was defined as the percent decline in torque between the average of repetitions 1,2,and 3 and repetitions 23,24,and 25.Polynomial regression was used to examine the individual and composite relation-ships between EMG amplitude (AMP),EMG mean power frequency (MPF),MMG AMP,MMG MPF,and torque versus repetitions.Results There was no significant difference (d =0.80;P =0.17) in the performance fatigability between Day 1 (19.3% ± 7.1%)and Day 2 (26.9% ± 11.3%).Polynomial regression indicated substantial inter-subject variability,but high day-to-day consistency.Conclusion The composite EMG AMP,MMG AMP,and MMG MPF patterns of responses demonstrated consistency across days.The composite EMG MPF patterns of responses,however,were not consistent between Day 1 and Day 2.In addition,based on the high inter-subject variability,future studies should present both composite patterns of neuromuscular responses and the patterns of responses on a subject-by-subject basis to make inferences regarding fatigue-induced changes in motor unit activation strategies.展开更多
Periods of hypo-activity result in profound changes in skeletal muscle morphology and strength. This review primarily addresses the differential impact of de-training, bed-rest, limb immobilisation and unilateral lowe...Periods of hypo-activity result in profound changes in skeletal muscle morphology and strength. This review primarily addresses the differential impact of de-training, bed-rest, limb immobilisation and unilateral lower limb suspension on muscle morphology, strength and fatigability. The degree of muscle atrophy differs depending on the hypo-activity model and the muscles in question, with the leg and postural muscles being the most susceptible to atrophy. Hypo-activity also results in the dramatic loss of strength that often surpasses the loss of muscle mass, and consequently, the nervous system and contractile properties adapt to adjust for this excessive loss of strength. In addition, the degree of muscle strength loss is different depending on the hypo-activity model, with immobilisation appearing to have a greater impact on strength than unloaded models. There is a step-wise difference in the magnitude of muscle loss so that, even after accounting for differential durations of interventions immobilisation ≥ unilateral lower limb suspension ≥ bed-rest ≥ de-training. Muscle fatigability varies between hypoactivity models but the results are equivocal and thismay be due to task-specific adaptations. This review also addresses potential nutritional interventions for attenuating hypo-activity induced muscle atrophy and strength declines, in the absence of exercise. Essential amino acid supplementation stands as a strong candidate but other supplements are good contenders for attenuating hypo-activity induced atrophy and strength losses. Several potential nutritional supplements are highlighted that could be used to combat muscle atrophy but extensive research is needed to determine the most effective.展开更多
文摘AIM： To evaluate the myoelectric manifestations of peripheral fatigability in patients with primary biliary cirrhosis in comparison to healthy subjects. METHODS： Sixteen women with primary biliary cirrhosis without comorbidity and 13 healthy women matched for age and body mass index （BMI） completed the selfreported questionnaire fatigue impact scale. All subjects underwent surface electromyography assessment of peripheral fatigability. Anterior tibial muscle isometric voluntary contraction was executed for 20 s at 80% of maximal voluntary isometric contraction. During the exercise electromyographic signal series were recorded and root mean square （expression of central drive） as well as mean and median of electromyographic signal frequency spectrum （estimates of muscle fatigability） were com- puted. Each subject executed the trial two times. EMG parameters were normalized, then linear regression was applied and slopes were calculated. RESULTS： Seven patients were fatigued （median fatigue impact scale score： 38, range： 26-66） and 9 were not fatigued （median fatigue impact scale score： 7, range： 0-17）. The maximal voluntary isometric contraction was similar in patients （82, 54-115 N） and controls （87, 74-101 N）, and in patients with high （81, 54-115 N） and low fatigue impact scale scores （86, 65-106 N）. Root mean square as well as mean and median of frequency spectrum slopes were compared with the Mann-Whitney U test, and no significant difference was found between fatigued and non-fatigued patients and controls. CONCLUSION： No instrumental evidence of peripheral fatigability can be found in women with primary biliary cirrhosis but no comorbidity, suggesting that fatigue in such patients may be of central origin.
文摘Background: Attractor-based kinematic gait analysis using the Fatigue Index Kliniken Schmieder (FKS), have been suggested as a sensitive tool to determine motor fatigability in persons with Multiple Sclerosis (pwMS). Hypothesis: Depression does not affect the FKS to a similar degree as in pwMS. Methods: We recruited 32 patients with major depression. Data were collected with two accelerometers attached to both ankles. Data were recorded for one minute at the beginning and at the end of the treadmill test. Attractor attributes were used to analyze the data. Results: The mean Fatigue Index Kliniken Schmieder (FKS) was 2.1. The change of the attractor (δM) was 3.7 and the change of variability (δD) was 0.6. Mean values were clearly below values of pwMS with fatigability from a previous publication. However, the individual level values from six individuals—five of them showed pain related comorbidity besides depression—fell within the lower pathological range. There was no correlation between Hamilton depression scale and the attractor attributes (δM and δD). Discussion: Depression does not affect gait as motor fatigability does in pwMS. Results from subjects with pain during the treadmill test show a moderately increased variability and moderately altered attractors.
基金supported by a Natural Science Foundation of China Grant(30770805)
文摘Muscle unloading due to long-term exposure of weightlessness or simulated weightlessness causes atrophy, loss of functional capacity, impaired locomotor coordination, and decreased resistance to fatigue in the antigravity muscles of the lower limbs. Besides reducing astronauts' mobility in space and on returning to a gravity environment, the molecular mechanisms for the adaptation of skeletal muscle to unloading also play an important medical role in conditions such as disuse and paralysis. The tail-suspended rat model was used to simulate the effects of weightlessness on skeletal muscles and to induce muscle unloading in the rat hindlimb. Our series studies have shown that the maximum of twitch tension and the twitch duration decreased significantly in the atrophic soleus muscles, the maximal tension of high-frequency tetanic contraction was significantly reduced in 2-week unloaded soleus muscles, however, the fatigability of highfrequency tetanic contraction increased after one week of unloading. The maximal isometric tension of intermittent tetanic contraction at optimal stimulating frequency did not alter in 1-and 2-week unloaded soleus, but significantly decreased in 4-week unloaded soleus. The 1-week unloaded soleus, but not extensor digitorum longus(EDL), was more susceptible to fatigue during intermittent tetanic contraction than the synchronous controls. The changes in K+ channel characteristics may increase the fatigability during high-frequency tetanic contraction in atrophic soleus muscles. High fatigability of intermittent tetanic contraction may be involved in enhanced activity of sarcoplasmic reticulum Ca2+-ATPase(SERCA) and switching from slow to fast isoform of myosin heavy chain, tropomyosin, troponin I and T subunit in atrophic soleus muscles. Unloaded soleus muscle also showed a decreased protein level of neuronal nitric oxide synthase(nNOS), and the reduction in nNOS-derived NO increased frequency of calcium sparks and elevated intracellular resting Ca2+ concentration([Ca2+]i) in unloaded soleus muscles. High [Ca2+]i activated calpain-1 which induced a higher degradation of desmin. Desmin degradation may loose connections between adjacent myofibrils and further misaligned Z-disc during repeated tetanic contractions. Passive stretch in unloaded muscle could preserve the stability of sarcoplasmic reticulum Ca2+ release channels by means of keeping nNOS activity, and decrease the enhanced protein level and activity of calpain to control levels in unloaded soleus muscles. Therefore, passive stretch restored normal appearance of Z-disc and resisted in part atrophy of unloaded soleus muscles. The above results indicate that enhanced fatigability of high-frequency tetanic contraction is associated to the alteration in K+ channel characteristics, and elevated SERCA activity and slow to fast transition of myosin heavy chain(MHC) isoforms increases fatigability of intermittent tetanic contraction in atrophic soleus muscle. The sarcomeric damage induced by tetanic contraction can be retarded by stretch in atrophic soleus muscles.
文摘Purpose The purpose of the present study was to examine the day-to-day consistency and inter-subject variability of com-posite and individual,neuromuscular and torque patterns of responses as a result of a fatiguing bout of maximal,bilateral,isokinetic leg extension muscle actions.Methods Ten men (Mean ± SD =21.6 ± 2.5 years) completed two testing visits consisting of pretest and posttest maximal voluntary isometric contractions (MVIC) as well as 25 maximal,bilateral,isokinetic (180°/s),leg extension muscle actions.Electromyographic (EMG) and mechanomyographic (MMG) signals were collected from the vastus lateralis and normalized to the MVIC.Performance fatigability was defined as the percent decline in torque between the average of repetitions 1,2,and 3 and repetitions 23,24,and 25.Polynomial regression was used to examine the individual and composite relation-ships between EMG amplitude (AMP),EMG mean power frequency (MPF),MMG AMP,MMG MPF,and torque versus repetitions.Results There was no significant difference (d =0.80;P =0.17) in the performance fatigability between Day 1 (19.3% ± 7.1%)and Day 2 (26.9% ± 11.3%).Polynomial regression indicated substantial inter-subject variability,but high day-to-day consistency.Conclusion The composite EMG AMP,MMG AMP,and MMG MPF patterns of responses demonstrated consistency across days.The composite EMG MPF patterns of responses,however,were not consistent between Day 1 and Day 2.In addition,based on the high inter-subject variability,future studies should present both composite patterns of neuromuscular responses and the patterns of responses on a subject-by-subject basis to make inferences regarding fatigue-induced changes in motor unit activation strategies.
文摘Periods of hypo-activity result in profound changes in skeletal muscle morphology and strength. This review primarily addresses the differential impact of de-training, bed-rest, limb immobilisation and unilateral lower limb suspension on muscle morphology, strength and fatigability. The degree of muscle atrophy differs depending on the hypo-activity model and the muscles in question, with the leg and postural muscles being the most susceptible to atrophy. Hypo-activity also results in the dramatic loss of strength that often surpasses the loss of muscle mass, and consequently, the nervous system and contractile properties adapt to adjust for this excessive loss of strength. In addition, the degree of muscle strength loss is different depending on the hypo-activity model, with immobilisation appearing to have a greater impact on strength than unloaded models. There is a step-wise difference in the magnitude of muscle loss so that, even after accounting for differential durations of interventions immobilisation ≥ unilateral lower limb suspension ≥ bed-rest ≥ de-training. Muscle fatigability varies between hypoactivity models but the results are equivocal and thismay be due to task-specific adaptations. This review also addresses potential nutritional interventions for attenuating hypo-activity induced muscle atrophy and strength declines, in the absence of exercise. Essential amino acid supplementation stands as a strong candidate but other supplements are good contenders for attenuating hypo-activity induced atrophy and strength losses. Several potential nutritional supplements are highlighted that could be used to combat muscle atrophy but extensive research is needed to determine the most effective.
