Decline In Peak Torque Research Articles

P478 Fatigue, physical fitness, and physical activity in patients with inflammatory bowel disease

Abstract Background Fatigue is a common and debilitating symptom in patients with Inflammatory Bowel Disease (IBD) with a great impact on quality of life and work productivity. A better comprehension of the contributing factors to fatigue could potentially pave the way for more targeted and effective strategies for managing fatigue in IBD. Fatigue may be associated with lower levels of physical activity and reduced physical fitness. Yet, the interaction between these factors in IBD, measured with validated tests, is not fully understood. Therefore, this study aimed to investigate the association between fatigue and physical fitness and physical activity in patients with IBD. Methods Adult patients with IBD in remission or with mild-to-moderate clinical disease activity with an ASA Physical Status <III were eligible for inclusion. Fatigue was defined as a Checklist Individual Strength-fatigue subscale score ≥35. Patient and clinical characteristics were collected, including age, sex, body mass index, comorbidities, disease duration, disease location and behavior, clinical and biochemical disease activity, smoking status, previous intestinal resection, and medication use. Cardiorespiratory fitness was measured using cardiopulmonary exercise testing to assess the oxygen uptake at peak exercise (VO2peak). Muscular strength (peak torque at 60°/s) and endurance (fatigue rate as percentage decline in peak torque over 30 repetitions at 180°/s) of the knee extensor and flexor muscles were assessed using an isokinetic dynamometer. Objective physical activity data were collected continuously for seven consecutive days utilizing the MOX accelerometer, with activities categorized into sedentary, standing, light (LPA), moderate (MPA), and vigorous physical activity (VPA) levels. Results In total, 50 patients were included, with 17 being classified as fatigued. Fatigued patients had significantly higher BMIs, a higher frequency of clinical disease activity, and a higher prevalence of smoking (Table 1). They also exhibited significantly lower VO2peak (mean [±SD] 28.1 [±7.9] vs. 36.0 [±9.8] mL·kg-1·min-1, p=0.007) and higher knee extensor fatigue rate (mean [±SD] 39.0% [±8.8] vs. 31.1% [±10.4], p=0.010) compared to non-fatigued patients. There was no statistical significant difference in physical activity between fatigued and non-fatigued patients. Conclusion Although physical activity did not differ between patients with and without fatigue, fatigued patients exhibited lower cardiorespiratory fitness and knee extensor muscular endurance. A larger population is needed to further investigate the influence of patient and disease characteristics on this relationship to work towards more targeted and effective strategies for managing fatigue in patients with IBD.

Neuromuscular fatigue in autoimmune myasthenia gravis: A cross-sectional study

ObjectivesTo investigate the presence of increased neuromuscular fatigue (NMF) in individuals with myasthenia gravis (IwMG), compared to healthy controls. A secondary aim was to assess associations between NMF, strength and perceived health-related quality of life (HRQoL) and symptom severity in IwMG. MethodsIn this cross-sectional study, we assessed NMF using classical myoelectrical indicators (root mean square: RMS, mean power frequency: MPF) obtained from surface electromyography (sEMG) during a sustained submaximal isometric contraction of the right Biceps Brachii and the right Vastus Lateralis and by evaluating the post-effort decline in peak torque following a fatiguing task consisting of a 40-second sustained isometric contraction. Relationships with MG-specific clinical scores (Myasthenia Muscle Score for symptom severity, MGQOL-15-F for HRQoL) were investigated. ResultsForty-one females with MG were compared to 18 control females of similar age. IwMG demonstrated reduced strength in both muscle groups, compared to control subjects. In both populations and both limbs, NMF was demonstrated by an increase in RMS and a decrease in MPF. However, IwMG did not demonstrate greater NMF based on these myoelectrical indicators nor based on post-effort peak torque decline. DiscussionDespite a decrease in baseline strength, IwMG did not display greater NMF in this specific experimental paradigm. This cohort consisted of individuals with mild-to-moderately severe MG which was well-controlled and stable. Further studies are warranted to identify simple and reliable methods to measure NMF in MG and to understand the relationship between NMF and perceived fatigue in activities of daily living for IwMG.

Examining The Association Between Muscular Fatigue Index And Physical Function In Middle-aged Women

PURPOSE: To examine the independent contribution of muscle fatigue to physical function (PF) performance in middle-aged women. METHODS: In this cross-sectional study, 104 middle-aged women (52.93 ± 6.10 years; BMI =26.38 ± 5.10 kg/m2) were assessed for muscle fatigue performance using a 25-repetition fatiguing knee flexion and extension task at 180 degrees per second. Muscle fatigue index (MFI) was calculated as the decline in peak torque from the first three repetitions to the last three repetitions. PF was objectively measured via the transfer task, 8-foot-up-and-go, 30-second chair stands, 6-minute-walk-test, and the lift-and-carry. A lower-extremity PF composite score also was calculated. Moderate to vigorous physical activity (MVPA) was measured using accelerometry and physical activity logs, while whole body and regional composition were measured using Dual Energy X-ray Absorptiometry. Muscle strength was assessed using isokinetic dynamometry for isometric knee flexion and extension at 60 degrees, and isokinetic knee flexion and extension at 60 degrees per second and 180 degrees per second, and muscle quality (MQ) was calculated as muscle strength normalized for thigh lean mass. The data were analyzed using bivariate correlation and hierarchical linear regression, with a p-value of less than 0.05 used to establish significance. RESULTS: When controlling for age, percent body fat, muscle quality, and MVPA per day, MFI was significantly associated with transfer task performance (r = .260, p < 0.05), and higher MFI was associated with slower transfer task time. While MFI contributed to 3.5% of the variance in transfer task performance (p = 0.024), percent body fat contributed to 19.4% of the variance (p = 0.001). Percent body fat was most highly associated with all measures of PF. CONCLUSIONS: The strength of the association between MFI and PF performance decreased when other independent variables (percent body fat, MVPA, MQ) were considered. Therefore, muscle fatigue may be a less important target for intervention in this population, while reducing percent body fat may be most influential in improving physical functional performance in middle-aged women.

Does increasing the number of channels during neuromuscular electrical stimulation reduce fatigability and produce larger contractions with less discomfort?

Neuromuscular electrical stimulation (NMES) is often delivered at frequencies that recruit motor units (MUs) at unphysiologically high rates, leading to contraction fatigability. Rotating NMES pulses between multiple electrodes recruits subpopulations of MUs from each site, reducing MU firing rates and fatigability. This study was designed to determine whether rotating pulses between an increasing number of stimulation channels (cathodes) reduces contraction fatigability and increases the ability to generate torque during NMES. A secondary outcome was perceived discomfort. Fifteen neurologically intact volunteers completed four sessions. NMES was delivered over the quadriceps through 1 (NMES1), 2 (NMES2), 4 (NMES4) or 8 (NMES8) channels. Fatigability was assessed over 100 contractions (1-s on/1-s off) at an initial contraction amplitude that was 20% of a maximal voluntary contraction. Torque-frequency relationships were characterized over six frequencies from 20 to 120Hz. NMES4 and NMES8 resulted in less decline in peak torque (42 and 41%) over the 100 contractions than NMES1 and NMES2 (53 and 50% decline). Increasing frequency from 20 to 120Hz increased torque by 7, 13, 21 and 24% MVC, for NMES1, NMES2, NMES4 and NMES8, respectively. Perceived discomfort was highest during NMES8. NMES4 and NMES8 reduced contraction fatigability and generated larger contractions across a range of frequencies than NMES1 and NMES2. NMES8 produced the most discomfort, likely due to small electrodes and high current density. During NMES, more is not better and rotating pulses between four channels may be optimal to reduce contraction fatigability and produce larger contractions with minimal discomfort compared to conventional NMES configurations.

Modification of a three-compartment muscle fatigue model to predict peak torque decline during intermittent tasks

This study aimed to test whether adding a rest recovery parameter, r, to the analytical three-compartment controller (3CC) fatigue model (Xia and Frey Law, 2008) will improve fatigue estimates during intermittent contractions. The 3CC muscle fatigue model uses differential equations to predict the flow of muscle between three muscle states: Resting (MR), Active (MA), and Fatigued (MF). This model uses a feedback controller to match the active state to target loads and two joint-specific parameters: F, fatigue rate controlling flow from active to fatigued compartments) and R, the recovery rate controlling flow from the fatigued to the resting compartments. This model does well to predict intensity-endurance time curves for sustained isometric tasks. However, previous studies find when rest intervals are present that the model over predicts fatigue. Intermittent rest periods would allow for the occurrence of subsequent reactive vasodilation and post-contraction hyperemia. We hypothesize a modified 3CC-r fatigue model will improve predictions of force decay during intermittent contractions with the addition of a rest recovery parameter, r, to augment recovery during rest intervals, representing muscle re-perfusion. A meta-analysis compiling intermittent fatigue data from 63 publications reporting decline in peak torque (% torque decline) were used for comparison. The original model over-predicted fatigue development from 19 to 29% torque decline; the addition of a rest multiplier significantly improved fatigue estimates to 6–10% torque decline. We conclude the addition of a rest multiplier to the three-compartment controller fatigue model provides a physiologically consistent modification for tasks involving rest intervals, resulting in improved estimates of muscle fatigue.

Reexamining Skeletal Muscle Fatigability and Fiber Type in Resistance Trained Med

Nearly 40 years ago Thorstensson and Karlsson developed an equation (THOR) allowing a fatigue test to estimate the percentage of fast-twitch muscle fibers (%FT) in an individual’s vastus lateralis (VL). Fiber-typing methodologies have advanced considerably since this time. Moreover, THOR was developed from a heterogeneous group of habitually active men. PURPOSE: Reexamine THOR using modern muscle fiber-typing techniques and in resistance-trained men. METHODS: Fifteen resistance-trained males (strength/power-trained ≥3d/wk for ≥6months; age=24.8±1.3y, height=1.79±0.05m, mass=82.2±8.0kg) performed 60 maximal knee extensions at 180°/s on an isokinetic dynamometer, returning on a separate day for a VL muscle biopsy. Approximately 200 individual fibers (per participant) were isolated and analyzed for fiber type using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Individual muscle fibers were identified as either expressing myosin heavy chain (MHC) I, I/IIa, IIa, IIa/IIx, IIx, or I/IIa/IIx. %FT was determined as a combination of MHC IIa, IIa/IIx, and IIx. RESULTS: The original correlation between FT% and percent decline in peak torque (r=0.86, p0.05). Moreover, a Bland-Altman plot suggested THOR overestimated %FT by an average of 6.91%, with a range of -27.62% to +41.44% (limits of agreement, 95% Confidence Interval) in our participants. Also, the data were heteroskedastic (correlation coefficient, R2 = 0.53, P = <0.01), indicating THOR underestimated FT% in participants with less fast-twitch fibers, and overestimated FT% in participants with more fast-twitch fibers. CONCLUSIONS: This collectively suggests fiber phenotype alone does not predict performance during a fatigue test in strength-trained men. These findings likely differ from Thorstensson and Karlsson because we utilized the highly precise single fiber-typing method that allowed differentiation of fibers into 6 isoform categories (as opposed to only 2 in THOR). However, THOR may still be valid when examining across heterogeneous exercise backgrounds or “habitually active” participants.

Influence of Hamstring Fatigue on the Estimated Percentage of Fast-Twitch Muscle Fibers for the Vastus Lateralis.

A previous study has demonstrated the ability to roughly estimate the percentage of fast-twitch muscle fibers for the vastus lateralis through the analysis of peak torque values during fatiguing isokinetic testing. We examined whether use of the hamstrings influenced peak torque and electromyographic (EMG) responses for the quadriceps during fatiguing isokinetic muscle actions. On 2 separate occasions, 21 men (mean age = 23 years) performed 50 repeated, maximal concentric isokinetic muscle actions of the left leg extensors at a velocity of 180°·s. For 1 trial, the subjects maximally flexed the knee joint after each full extension to bring the dynamometer's lever arm back to the starting position. For the other trial, the subjects relaxed after each maximal extension and an investigator assisted in returning the lever arm. Surface EMG signals were detected from the vastus lateralis and biceps femoris throughout testing. Dependent variables that assessed the decline in peak torque and EMG mean frequency for the vastus lateralis were examined using dependent samples t-tests, effect size statistics, and the number of subjects who exceeded the minimal difference needed to be considered real. Our results showed small mean differences between the trials (Cohen's d ≤0.136). For the estimated percentage of fast-twitch fibers, none of the subjects showed a difference between trials that we considered meaningful. The mean estimated percentages of fast-twitch fibers were 61.6 and 60.1. Collectively, use of the hamstrings during fatiguing isokinetic testing of the quadriceps had little influence on peak torque and EMG.

A potential mechanism by which torque output is preserved in cerebral palsy during fatiguing contractions of the knee extensors.

The purpose of this study was to compare agonist and antagonist electromyography (EMG) during an isokinetic fatigue protocol in subjects with cerebral palsy (CP) and typical development (TD). Nine individuals with CP and 11 with TD completed 50 repetitions of maximum concentric knee extensions (KE) and flexions (KF) at 60°/second. Rate of decline in peak torque for KE was significantly less in CP compared with TD. Rate of decline in agonist EMG was not significantly different between groups, but the rate of decline in antagonist EMG was significantly greater in CP. There were no differences between groups for KF. Declining agonist EMG occurred in parallel with declining antagonist hamstring activity in CP, decreasing the relative opposing force and resulting in a lesser decline in net torque. This finding illustrates a potential mechanism by which net torque is preserved in those with CP who are inherently weaker.

Peak Torque and Electromyographic Responses during Fatiguing Concentric Muscle Actions with Eyes-Open versus Eyes-Closed

This study compared peak torque and electromyographic (EMG) mean frequency responses during fatiguing muscle actions with eyes-open vs eyes-closed. On four separate days, 21 men (M age = 23 yr.) performed 100 repeated maximal concentric muscle actions of the forearm flexors with eyes-open, eyes-closed, eyes-closed for first 50 muscle actions, and eyes-closed for the last 50 muscle actions while surface EMG signals were collected from the biceps brachii. The data were examined with seven separate repeated measures analyses of variance. There were no mean differences among the conditions for initial, average, and final peak torque, percent decline, the linear slope coefficient for the decline in peak torque, as well as the linear slope coefficient and y-intercept for the normalized EMG mean frequency vs repetition number relationships. These findings indicate performance during fatiguing muscle actions is not influenced by whether participants have their eyes open or closed throughout testing.

Efeitos de diferentes intervalos de recuperação nas respostas neuromusculares em crianças - doi: 10.4025/reveducfis.v22i4.11074

The purpose of this study was to compare the effect of two different rest intervals between sets of isokinetic knee extension exercise on peak torque (PT), and Total Work (TW) in children. 18 boys (11.1 ± 0.52 yrs, 32.9 ± 3.32 kg and 142.6 ± 4.78 cm, Tanner stage 1 and 2) performed 3 sets of 10 unilateral isokinetic knee extension repetitions at 60°/s and 180°/s. The rest intervals between sets were 1 and 2 minutes. There was no significant decline in PT and TW when 1 and 2 min rest intervals were used at 60°/s and 180°/s. The present study indicated that children need only 1min to recover muscle performance, indicating high resistance to muscle fatigue during high intensity resistance exercise and different movement velocities.

Consumo de suplementos proteicos e expressão da raiva em praticantes de musculação

O proposito do presente estudo foi verificar os efeitos de diferentes intervalos de recuperacao (IRs) entre series de exercicios resistidos em criancas nas variaveis de pico de torque (PT) e trabalho total (TT). Participaram do estudo 18 meninos (11,1 ± 0,52 anos, 32,9 ± 3,32 kg e 142,6 ± 4,78 cm, classificados nos estagios de Tanner 1 e 2). Foi utilizado um protocolo de tres series de dez repeticoes de exercicios isocineticos em dois IRs (de um e dois minutos) nas velocidades de 60o/s e 180o/s. Nao foram encontradas diferencas significativas (P> 0,05) no PT, TT entre os IRs de um e dois minutos nas velocidades de 60o/s e 180o/s. Conclui-se que as criancas necessitam de curtos periodos de recuperacao (um minuto) para a manutencao da performance muscular, indicando assim uma alta capacidade de resistencia a fadiga em exercicios resistidos de alta intensidade e com diferentes velocidades de execucao.

Efeitos do intervalo de recuperação nas respostas neuromusculares em crianças

The purpose of this study was to compare the effect of two different rest intervals between sets of isokinetic knee extension exercise on peak torque (PT), and Total Work (TW) in children. 18 boys (11.1 ± 0.52 yrs, 32.9 ± 3.32 kg and 142.6 ± 4.78 cm, Tanner stage 1 and 2) performed 3 sets of 10 unilateral isokinetic knee extension repetitions at 60°/s and 180°/s. The rest intervals between sets were 1 and 2 minutes. There was no significant decline in PT and TW when 1 and 2 min rest intervals were used at 60°/s and 180°/s. The present study indicated that children need only 1min to recover muscle performance, indicating high resistance to muscle fatigue during high intensity resistance exercise and different movement velocities.

The Effects of Diverting Activities on Recovery from Fatiguing Concentric Isokinetic Muscle Actions

The purpose of this study was to examine the effects of diverting activities on recovery from fatiguing concentric isokinetic muscle actions. On 3 separate occasions, 11 men (mean ± SD age = 22.2 ± 1.5 years) and 8 women (mean ± SD age = 22.2 ± 2.1 years) performed 2 bouts of 50 consecutive maximal concentric isokinetic muscle actions of the dominant leg extensors. Between these bouts, the subjects either performed math problems (mental diverting activity), contralateral dynamic constant external resistance (DCER) leg extensions (physical diverting activity), or rested quietly (control). For each trial, the peak torque data from the first and second bouts of 50 muscle actions served as the pretest (Pre) and posttest (Post) data, respectively. The results indicated that when the subjects rested quietly or performed contralateral DCER leg extensions between the fatiguing bouts, the initial peak torque values observed for Post were significantly less than those for Pre. When the subjects performed math problems, however, no decline in the initial peak torque values was observed, thus indicating better recovery. In addition, a decline in the average torque values was observed from Pre to Post for the control trial but not for the math problem or contralateral exercise trials. No differences were observed among the trials for final peak torque, percent decline, or the linear slope of the decline in peak torque. These findings demonstrated that performing either mental or physical diverting activities after fatiguing isokinetic muscle actions enhanced recovery.

Effects of antagonist pre-load on knee extensor isokinetic muscle performance

The aim of this study was to evaluate and compare acute effects of a reciprocal action protocol and a super-set protocol on knee extensor performance during concentric isokinetic exercise. Fourteen men aged 29.4 ± 6.1 years were tested on three different protocols, with 1 min of rest between sets: control (3 sets of 10 isokinetic knee extension repetitions), reciprocal action protocol (3 sets of 10 repetitions of reciprocal isokinetic concentric knee flexion and knee extension repetitions), and super-set protocol (3 sets of a combination of 10 repetitions of knee flexion immediately followed by 10 repetitions of knee extension repetitions). Tests were performed at 60° · s−1 and 180° · s−1, randomized across 3 days and separated by at least 72 h. There were no significant differences between protocols for peak torque at 60° · s−1 or 180° · s−1. Total work was significantly higher during the reciprocal action protocol compared with the super-set protocol at 60° · s−1. There was a significant decline in peak torque (from 240.6 to 212.9 N · m) and total work (from 2294 to 1899 J) for the control condition at 60° · s−1. Also, total work declined significantly across sets for the super-set protocol at 60° · s−1 (from 2157 to 1707 J). Results indicate that a reciprocal action protocol provides torque maintenance during multiple sets of isokinetic training, both at slow and high velocities.

Gender Muscle Recovery During Isokinetic Exercise

The purpose of this study was to examine the effect of two between set rest intervals (RI) on isokinetic knee extension peak torque (PT) produced by sedentary women and men. Seventeen young women (27.18 ± 4.05 yrs) and 16 young men (26.75 ± 4.73 yrs) performed 3 sets of 10 unilateral isokinetic knee extension at 60° and 180°/s. The RI between sets was 60 and 120 s, counterbalanced across 2 testing days. Statistical evaluation of the data was performed using a 3-way mixed factor ANOVA (gender x rest interval x sets). Males and females exhibited decreases (p<0.05) in PT with 120 s RI at 60°/s. There was no significant decline in PT in the female group during both RI at 180°/s. Men showed a significant decrease in PT only with 60 s RI. Young women and men require more than 120 s of RI to recover full PT at 60°/s. However, full quadriceps's muscle strength recovery can be attained with a 60 and 120 s at 180°/s in women, but in men only with a 120 s at the same velocity.

Effects of Age and Rest Interval on Strength Recovery

The purpose of this study was to compare the effect of two different rest intervals between sets of isokinetic knee extension exercise on peak torque (PT), and Total Work (TW) between untrained younger and older men. Seventeen young men (24.22+/-2.58 yrs) and 20 older men (66.85+/-4.02 yrs) performed 3 sets of 10 unilateral isokinetic knee extension repetitions at 60 degrees /s. The rest intervals between sets were 1 and 2 min. There was a significant decline in PT when 1 and 2 min rest intervals were used for young men, but not when a 2 min rest interval was applied for old men. There was also a significant decline in TW among the 3 sets when 1 and 2 min rest intervals were applied for young men, whereas the decline in TW in older men occurred only between the 2(nd) and 3(rd) sets. PT and TW in the 3(rd) set were significant greater following a 2 min rest interval than a 1 min rest in both young and older men. The present study indicated that non-resistance trained young men may require longer rest interval to recover full PT and TW when compared to older men.

Relationship between Muscle Oxygenation Kinetics and the Rate of Decline in Peak Torque during Isokinetic Knee Extension in Acute Hypoxia and Normoxia

To investigate whether low FiO2 affects muscle oxygenation and the rate of decline in peak torque (DR) during isokinetic knee extension, subjects performed 50 isokinetic knee extensions at 180 degrees /s and at 0.5 Hz while inhaling low O2 gas (12 %O2; H) or air (N). Muscle oxygenation kinetics was assessed by near-infrared spectroscopy, and whole-body V.O2 and HR were measured. We calculated total-, oxy- and deoxy-hemoglobin/myoglobin concentrations (TotalHb/Mb, OxyHb/Mb, DeoxyHb/Mb), and the slopes of the change in OxyHb/Mb during exercise. SpO2 decreased in H while DR and V.O2 did not differ between the conditions. During exercise, OxyHb/Mb was lower in H than in N, and DeoxyHb/Mb was higher in H than in N. TotalHb/Mb began to increase from the resting level earlier in H. HR was higher during the latter half of the exercise in H. The slopes of the change in OxyHb/Mb were the same in the two conditions. Our results show that low FiO2 decreases SpO2 and muscle oxygenation during maximal isokinetic knee extension. However, low SpO2 and muscle oxygenation did not affect the rates of decline of peak torque. These results suggest that the decline in peak torque occurs for reasons other than O2 availability.

Endurance training delays age of decline in leg strength and muscle morphology.

It has been reported that maximal strength peaks at approximately 30 yr of age, plateaus, and remains relatively stable for the next 20 yr, with an age-related decline in strength becoming significant after age 50. Much of the research attributes this decrease in peak force to age-associated reductions in muscle mass, with a selective atrophy and reduction in Type II fiber area and number being the primary factors. The influence that chronic endurance training has upon age-associated changes in muscular strength and muscle morphology has been largely undetermined. The purpose of this investigation was to examine the influence of chronic endurance training and age on leg extensor strength, and muscle fiber size and type distribution. Male master runners (N = 107, age range = 40-88 yr) were tested for maximal strength of the leg extensor muscles. A subgroup of 30 master athletes participated in muscle biopsy testing. The effects of age were addressed by subdividing the sample into five cohorts. Peak isokinetic concentric torque did not differ between age groups until after age 70 yr. Regression analysis revealed a significant (P < 0.05, r(2) = 0.1838) age-associated decrease in relative strength (N.m.kg(-1) lean body mass). Type I and Type II fiber area and distribution did not differ between age groups through the eighth decade. These data suggest that chronic endurance training can delay the age of significant decline in peak torque and changes in muscle morphology characteristics of the vastus lateralis.

The effect of age, speed, and arm dominance on shoulder function in untrained men.

Bilateral shoulder motor output measurements were obtained in 40 subjects with a Biodex dynamometer. The subjects included two groups, a younger group (20 to 30 years) and an older group (50 to 60 years). They were engaged in low to moderate levels of occupational and spare-time physical activity. Each subject performed three maximum effort shoulder movements in flexion/extension, abduction/adduction, and internal/external rotation at 60 degrees/sec and 120 degrees/sec. Side tested, axis, and speed were randomly selected. The findings indicate that a significant decline occurred in peak torque, work, and power for all axes of movement at both speeds when the older group was compared with the younger group. A decline in peak torque and work and a corresponding increase in power resulting from an increase in speed occurred in both age groups. The effect of age was the same at 60 degrees/sec and at 120 degrees/sec. Overall, no difference in dominant and nondominant motor function was seen in either the younger or older untrained men.

Recovery From a 1-Minute Bout of Fatiguing Exercise: Characteristics, Reliability, and Responsiveness

The purposes of this study were (1) to describe the characteristics of recovery of peak torque after a 1-minute bout of isokinetic exercise of the quadriceps femoris muscle, (2) to determine the short-term reliability of the recovery of peak torque, and (3) to determine whether the recovery of peak torque more closely associates with maximal endurance exercise capacity than does the decline in peak torque at the end of the fatigue test. Thirty-three nondisabled subjects, ranging in age from 23 to 34 years (X = 27, SD = 3.4), participated in the reliability portion (phase 1) of the study. A different group of 21 nondisabled subjects, ranging in age from 21 to 47 years (X = 27.5, SD = 5.2), participated in the correlational portion (phase 2) of the study. The short-term reliability of percentage of decline in peak torque and recovery of peak torque was assessed in phase 1. Each subject performed two quadriceps femoris muscle fatigue tests (test-retest) on an isokinetic dynamometer. In phase 2, each subject performed a single fatigue test and a test of maximal oxygen uptake (VO2max) to examine the relationships between VO2max and percentage of decline in peak torque at the end of the fatigue test and recovery of peak torque. Intraclass correlation coefficient values at every 30-second interval during recovery were acceptable (ICC = .67-.87), indicating recovery of peak torque is a consistent measure of quadriceps femoris muscle performance. A high negative correlation (r = -.84) was found between the percentage of decline at 30 seconds of recovery and VO2max, but a lower negative correlation (r = -.48) was found between the percentage of decline in torque at the end of the fatigue test and VO2max. These results suggest recovery of peak torque is a reliable measure of muscle performance and closely associates with maximal aerobic exercise capacity.