ABSTRACT
This study aimed to clarify the relative growth in thigh muscle size and sprint performance in children from 3 to 15 years. A total of 902 children performed a 30-m sprint test. Sprint time was measured by a photocell system. Muscle thicknesses of thigh anterior and posterior were determined by using a B-mode ultrasound. For 431 children, step frequency (SF) and step length (SL) during the sprint running were also analyzed with the films, and corrected by leg length. Using an allometry equation based on body height, relative growth of thigh muscle size and sprint performance was estimated. In both boys and girls, there was a breakpoint (BP) at which the rate of development in sprint velocity changes, and the rate of development was slower after the BP. On the other hand, the rate of growth in thigh muscle size after the BP was superior to that before the point, except of thigh posterior in boys. Regardless of sex, the rate of development in SL index after the BP became to be lower with increasing body height, whereas SF index relatively increased. These current findings indicate that in boys and girls, the rate of development in sprint velocity becomes to be lower above a certain body height, and the relative slow development may result from those in SF and SL.
ABSTRACT
<p>We aimed to elucidate the impact of the conducting state in exercise programs and the degree of improvement in sit-to-stand power index (STS-PI) on the continuation of Chokin exercise by participants one year from the completion of the intervention period. Subjects participated in a 12-week Chokin exercise class for the elderly, which consisted of 10 body mass-based exercises. As variables indicating exercise conditions, the number of exercise days weekly and the total number of sets performed during the intervention period were adopted. STS-PI was calculated using the time required to perform 10-times-repeated sit-to-stand task, and its relative change (%∆STS-PI) was used to represent the degree of improvement in physical function. Among 52 men and 129 women who responded to the inquiry about the continuation of Chokin exercise one year from the completion of the intervention period, 32 men and 93 women confirmed continuation of the exercise program. Logistic regression analysis showed that %∆STS-PI for men, as well as %∆STS-PI and the number of exercise days weekly for women, were factors associated with the decision of subjects to continue the Chokin exercise. These results indicate that the degree of improvement in STS-PI associated with the Chokin exercise class is a factor for continuing the exercise program one year from the completion of the intervention period, at least in elderly men and women. Furthermore, high exercise frequency during the intervention period may be associated with the decision to continue Chokin exercise after the completion of the intervention among women.</p>
ABSTRACT
<p>This study aimed to clarify the differences in cardiorespiratory and metabolic responses to body mass-based front lunge and squat exercises with relation to muscular activity. Seven healthy adult males performed 200 times body mass-based squat and front lunge exercises. During the exercises, oxygen uptake, heart rate (HR), blood lactate concentration (La), ground reaction force were measured. Oxygen uptake was divided by body mass (VO<sub>2</sub>). VO<sub>2</sub> and HR was normalized to maximal VO<sub>2</sub> (%VO<sub>2</sub>max) and maximal HR (%HRmax) obtained from an incremental load test. Electromyograms (EMGs) during the two exercises were recorded from the vastus lateralis (VL), rectus femoris, vastus medialis (VM), biceps femoris, gluteus maximus (GM). EMG amplitudes during both exercises were normalized to those during maximal voluntary contraction, and expressed as relative value (%EMG<sub>MVC</sub>). Time that cardiorespiratory parameters became stable was 4-6 min in both exercises. VO<sub>2</sub>, %VO<sub>2</sub>max, metabolic equivalent, were higher in the front lunge than the squat. No significant differences in HR, %HRmax and La were found between both tasks. %EMG<sub>MVC</sub> in VL, VM and GM were higher in the front lunge than the squat. These current findings indicate that 1) body mass-based squat and front lunge exercises are physiologically of more than moderate intensity, and 2) the cardiorespiratory responses to body mass-based front lunge are greater than those to body mass-based squat. This may be due to the difference in muscular activities of VL, VM and GM during the tasks.</p>
ABSTRACT
This study aimed to elucidate how body composition, force-generating capacity and jump performances are associated with 50-m sprint velocity in circumpubertal boys, in relation to sprint phases and maturation. One hundred thirty four circumpubertal boys were allocated to preadolescent or adolescent group on basis of the height at the peak height velocity of Japanese boys (154 cm) reported in literature: those with body heights over 154 cm as adolescent group and others as preadolescent group. Body composition was determined by bioelectrical impedance analysis. In addition to maximal voluntary isometric knee extension torque, the performances of counter movement jump (CMJ), rebound jump (RJ), standing long jump (SLJ) and standing 5-step jump (SFJ) were also measured. RJ-index was calculated by dividing height by contact time. The time of 50-m sprint was determined at 10-m intervals. Multiple regression analysis showed that in preadolescent boys, SFJ become a predictor for the sprint speed during acceleration phases, and SFJ, RJ-index and CMJ as predictors for the sprint speeds during maximal speed and deceleration phases. In the adolescent boys, age, CMJ, SLJ, and SFJ become a predictor for the sprint speed during acceleration phases, and torque relative to body mass, CMJ and SFJ were selected as predictors for the sprint speeds during maximal speed and deceleration phases. Thus, the current results indicate that force-generating capacity and jumping ability are determinants for sprint performance in circumpubertal boys, but the relative contribution of each of the two factors differs between preadolescent and adolescent stages and among the sprint phases.
ABSTRACT
This study aimed to determine the relationships between the torque generating capacity of the lower extremity muscles and either running or jump performance in primary and junior high school boys. A total of 102 primary and junior high school boys participated in this study. Muscle thicknesses (MTs) of the knee extensors and plantar flexors were determined using ultrasonography. Muscle volumes (MVs) of the knee extensors and plantar flexors were estimated using MTs and limb lengths. The isometric joint torques (TQs) for knee extensors and ankle plantar flexors were measured using myometer. MV and TQ were divided by body mass (MV/BM and TQ/BM, respectively). Running velocity was measured using a non-motorized treadmill. The counter movement jump (CMJ) and squat jump (SJ) were performed on a matswitch system. The flight time was measured and used to calculate the heights of CMJ and SJ using the following equation; height (cm) = g × (flight time)<sup>2</sup> /8/10. As the result of multiple regression analysis, age, MV/BM and TQ/BM were selected as predictors of running velocity in the primary school boys, whereas TQ and lean body mass in junior high school boys. In the primary school boys, TQ/BM and body fat mass was selected as significant contributors for SJ and CMJ performances, whereas, in the junior high school boys, TQ and the percent of body fat for SJ performance and MV/BM and TQ for CMJ performance. Thus, the present results indicate that the relationships between torque generating capacity of the lower extremity muscles and either running or jump performance differ between primary and junior high school boys. It may be assumed that, for running and jump performances, muscle mass and strength become determinant factors in junior high school boys, whereas their values relative to body mass in primary school boys.
ABSTRACT
In this study, we examined applicability of existing equations to predicting the body surface area (BSA) of children, and newly developed prediction equations for the BSA of children. BSA of 87 children of both genders (7∼12 yr) was determined by the three-dimensional photonic image scanning (3DPS), which was used as reference. BSA predicted using existing equations yielded overestimation or underestimation and/or a systematic error with respect to the reference. BSA prediction equations for boys and girls were developed using height and body mass as independent variables for the validation group and cross-validated for another group. The standard errors of estimation of the prediction equations were 105 cm<sup>2</sup> (0.9 %) for boys and 158 cm<sup>2</sup>(1.4 %) for girls. In the cross-validation group, there was no significant difference between the predicted and measured values without systematic errors. These findings indicate that existing equations cannot accurately predict BSA of children, and that the newly developed prediction equations are capable of predicting BSA of children with adequate accuracy.
ABSTRACT
This study was conducted to examine the reliability of three-dimensional photonic image scanning (3DPS) for measuring body surface area (BSA), and formulate equations for predicting BSA based on 3DPS. The surface area (SA) of a cylinder with known SA and BSA of 7 males were repeatedly measured by 3DPS. BSA was determined by 3DPS for 122 subjects (25–76 yrs). BSA prediction equations for both genders were developed for the validation group (16 males and 45 females) using body height and mass as independent variables, and were cross-validated for the cross-validation group (16 males and 45 females). The standard error of measurement was 2.2cm<sup>2</sup> (0.16%). The coefficients of variation (CV) for repeated measurements of SA were less than 0.2%. The BSA of subjects did not differ significantly on any given day nor between days, with a CV of less than 1%. The coefficient of determination and standard error of estimation of the prediction equations were 0.98 and 183cm<sup>2</sup> (1.1%), respectively, for males and 0.98 and 204cm<sup>2</sup> (1.3%), respectively, for females. There was no significant difference between the predicted and measured values. In the cross-validation group, there was no significant difference between the predicted and measured values without systematic errors. These findings indicate that 3DPS is reliable for measuring BSA, and the formulated equations are valid and applicable to individuals within a wide age-range.
ABSTRACT
The present study aimed to investigate the profiles of activities of thigh muscles during 100 m sprint running in track and field athletes experienced hamstrings (muscle) strain injury, with specific emphasis on the difference between injured and non-inured legs. The subjects were 20 track and field athletes who were divided into muscle strain injury group (MS) and non muscle strain injury group (NMS). The electromyograms (EMGs) of five thigh muscles (the biceps femoris, semitendinosus, rectus femoris, vastus lateralis and vastus medialis) and knee joint angles were recorded during 100 m sprint running. For NMS, there were no significant differences between the right and left legs. For MS, the averaged EMG of every muscle,expressed as relative to that during maximum voluntary contraction (%mEMG<sub>MVC</sub>), values of the biceps femoris and semitendinosus in the latter phases of takeoff and swing periods were significantly higher in the injured leg than in the non-injured leg. Also, the maximal flexed and extended angles of the knee joint during takeoff and swing period, respectively, for the injured leg were significantly greater than those for non-injured leg. Thus, the present results indicate that track and field athletes experienced hamstrings (muscle) strain injury show by higher EMG activities in the biceps femoiris and semitendinosus of the injured leg at the later phases of swing and takeoff periods during 100 m sprint running. This may be partially related to the running style with a greater extended position of knee joint angles at the corresponding phases.
ABSTRACT
The aim of this study was to investigate the differences between male and female in the activity level of trunk and lower limb muscles during basic daily physical actions. Six young adult male and six female subjects performed 14 daily life actions, i. e. postural maintenance and change, and body weight transfer actions. The surface EMG of six muscles of the trunk and the lower limb was recorded using a portable electromyography apparatus. Maximal EMG response (EMG<sub>max</sub>) during isometric maximal voluntary contraction for each muscle was used to normalize the EMG signal. In the performed actions, the average activity level of each muscle corresponded to 20% EMG<sub>max</sub> or less in male and 30% EMG<sub>max</sub> or less in female subjects, though there were some actions which exceeded 40% EMG<sub>max</sub> in the soleus muscle. As a result of 3-way ANOVA, significant effects for each of the 3 factors (action, muscle and sex) for muscular activity level were recognized and there were significant interactions among each pair of factors. The mean activity level of leg muscles in actions which support and transfer body weight was significantly higher in females than males. In the case of identical actions, the total time taken to reach a high muscular activity level was longer in females than males. From these results, it can be assumed that the load on the lower limb muscles is larger for females than males in the case of supporting and transferring body weight in daily life.
ABSTRACT
This study aimed to estimate <I>in vivo</I> the compliance of tendon structure in human biceps brachii (BB) muscle for eight healthy male subjects. Elongation of the tendon of BB during isometric elbowflexion was directly measured by ultrasonography. Muscle force of BB (F<SUB>BB</SUB>) was calculated from the elbow flexion torque and moment arm of elbow-flexor. When the EBB increased to 80%MVC (maximum voluntary contraction), the tendinous tissue of BB was elongated 10.24±2.52 mm, horizontally. The relationship between tendon length and F<SUB>BB</SUB> was curvilinear and consisted of an initial region characterized by a large increase in tendon length with increasing F<SUB>BB</SUB> under 50%MVC, immediately followed by a linear region. The compliance of tendinous tissues, estimated from the slope of the linear region, was 0.010±0.005 mm N, and did not show a significant correlation with MVC and muscle volume of the elbow flexors, estimated from muscle thickness. The compliance value observed here was lower than those of the medial gastrocnemius muscle and the tibialis anterior muscle, reported previously using the same ultrasonic method as the present study. This may be related to the functional differences among limb muscles in various human movements.
ABSTRACT
The present study aimed to investigate the level of muscular activities such as postural mainte nance and change, and body weight transfer during daily physical activities, through electromyogram (EMG) recordings. In each of 27 prescribed movements, EMGs of a total of 8 muscles located in the upper arms, trunk and lower limbs were recorded in 12 young adult men and women using a port-able surface electromyograph apparatus. The percentage of integrated EMG per time (mEMG) to that during isometric maximum voluntary contraction (MVC) was calculated as an index by assessing the muscular activity level in each of the prescribed movements. In most of the prescribed movements, the muscular activity level of every muscle corresponded to about 20-30% of MVC, and tended to be higher in women than men. However, some actions induced an activity level of 40% and more of MVC in the soleus muscle. The activity levels of the lower limb muscles in going up and down stairs and a slope at a fast speed, and jogging were higher compared to other prescribed movements. Thus, the results indicate that body weight transfer actions in daily life raise the activities of the lower limb muscles to a level sufficient for maintaining and increasing their function.
ABSTRACT
Walking is the most basic movement in daily life, and is a popular exercise for eloerly individuals to keep their health. However, it is not clear how walking is effective in keeping or increasing the muscle mass and bone intensity of the lower limbs. This study aimed to investigate the relationships between walking steps per day during daily life and either the muscle thickness values of lower leg anterior and posterior or the bone intensity of calcaneus. The subjects were 116 healthy men (n=31) and women (n=85) aged from 60 to 78 yrs, Walking steps per day were deter-mined using a pedometer. Muscle thickness values at the lower leg anterior and posterior sites and the osteo sono assessment index (OSI) of calcaneus were determined using ultrasonographic apparatuses. In women, OSI correlated significantly with walking steps (r=0.265, p<0.05) and the product of walking steps and weight (r=0.369, p<0.05) . In both genders, however, no significant correlations were found between walking steps and muscle thickness values at the two sites. The findings here suggest that increasing the number of walking steps during daily life will improve the intensity of calcaneus for elderly women, but is not effective for inducing hypertrophic change in the muscles located in the lower limbs for elderly individuals of both genders.
ABSTRACT
According to cross-sectional studies, decreased postural stability, assessed by center of pressure (COP) sway, has been remarkable over the past 60 years, and has become one of the impairment factors for quality of life in the elderly. In the present study, in order to determine whether exercise training, consisting of bicycle ergometer and strength training inhibits decreased postural stability for elderly individuals (60 years of age or more), we investigated changes in COP sway and plantar flexors muscle volume. Healthy male (n=9) and female (n=8) subjects aged 62 to 76 yrs participated in the present study. Subjects were requested to maintain a quiet standing barefoot position on a force platform (type 9281B, Kistler) with their eyes opened or closed. Mean velocity of COP (COP sway length/time) was calculated from anterior-posterior COP sway from force platform data. From the spectral analysis of COP sway, low (0-1 Hz) and high (1 -10 Hz) frequency components of COP series were extracted. The muscle volume of the plantar flexors muscle group was estimated from multi-regression analysis based on measured muscle thickness at the lower leg posterior site using an ultrasonographic apparatus (SSD-500, Aloka) . Mean velocity of COP significantly (P< 0.05) decreased due to training, and this was accompanied by a decrease in COP sway high frequency components. On the other hand, COP sway low frequency components and muscle volume did not change. These findings suggest that an inhibition of decreased postural stability in the elderly is not mainly related to muscle volume, but to improvement of a feedback system from somatosensory function. With respect to the elderly, who have a larger mean velocity of COP, however, postural stability could be related to muscle volume.
ABSTRACT
The factors influencing ankle range of motion were investigated for 185 middle-aged and elderly subjects (116 women and 69 men, aged 48-86 years) . Each subject was seated with the right knee extended, and the ankle joint was passively dorsiflexed by a dynamometer with torque just tolerable for each subject, to measure the maximal dorsiflexion angle. During passive loading, elongation of muscle fibers in the gastrocnemius and Achilles tendon was determined in vivo by ultrasonography. There was a difference between women and men for the passive dorsiflexion angle (men smaller than women), which negatively correlated with muscle thickness of the posterior portion of the leg determined by ultrasonography. Both in women and men, the passive dorsiflexion angle negatively correlated with age, even after normalizing for maximal voluntary plantar flexion torque. Both elongation of muscle fibers and tendon was related to the passive dorsiflexion angle, and the ratio of tendon elongation to muscle fiber elongation positively correlated with the passive dorsiflexion angle. The active dorsiflexion angle, measured separately with the subject maximally dorsiflexing the ankle with no load, correlated with the passive dorsiflexion angle but not with age, and there was no gender difference. From the results it was suggested 1) that the mobility of the ankle joint is affected by elongation of both muscle fibers and tendon, but with the effect of the tendon being greater than that of muscle fibers, and 2) that muscle mass negatively affects passively-induced joint range of motion. Actively performed joint range of motion would be affected by elongation of the muscle-tendon corn plex and force-generating capability of the ankle. Gender difference in joint range of motion and the aging effect are related to these factors.
ABSTRACT
This study was aimed to investigate the influences of age and gender on isometric muscle torque and explosive muscle power output with reference to muscle volume. A total of 177 healthy subjects of both genders were divided into four groups according to their age and gender : 46 young men (22.0±3.2yrs), 43 young women (22.7±3.3yrs), 46 elderly men (71.2±4.3yrs) and 42 elderly women (72.7±4.5 yrs) . The maximal voluntary isometric knee extension torque of the right leg (hip and knee angle at 90 degrees) and the power of bilateral leg extension in sitting position were mea sured. The ratios of both torque and power to muscle volume, estimated using ultrasonograph measurement, was calculated (torque/MV and power/MV respectively) . Torque was significantly less among the elderly than among the young for both genders, and among women than among the men for both age groups. Significant age-related differences were evident even in terms of torque/ MV, but the corresponding differences between men and women disappeared. On the other hand, power MV showed significant age- and gender-related differences, and the age-related difference was larger than that for torque MV. These results suggest that age- and gender-related differences in power are more noticeable than differences in torque and that these differences are not simply explained by differences in muscle volume.
ABSTRACT
The influences of age on muscle architectural characteristics, i. e., muscle thickness, pennation angle, fascicle length, were studied in 121 men and 229 women aged 17 to 85 yrs. The subjects were divided into three age groups (younger : 17-39 yrs, middle-aged : 40-59 yrs, elderly : 60-85 yrs) for both genders. Muscle thickness and pennation angle of the vastus lateralis (VL), medial gastrocnemius (MG), and long head of triceps brachii (TB) muscles were measured using B-mode ultraso-nography, and fascicle length was estimated. In all age groups, men had significantly greater relative muscle thickness (to limb length) in VI, and TB than women, but not in MG. Relative muscle thickness of VL was significantly lower in elderly than in younger and middle-aged subjects. Ilowever, the corresponding differences in MG and TB were insignificant. The pennation angle of VL was significantly lower in elderly than in younger and middle-aged subjects, although there were no significant differences in pennation angles of MG and TB among the three groups. These results suggest that the decrease in thickness of vastus lateralis muscle with aging is significant, but not significant for medial gastrocnemius and triceps hrachii muscles.
ABSTRACT
This study aimed to investigate the influence of aging on muscle thickness in lower limbs, with specific emphasis on the site- and gender-related differences. Subjects were a total of 191 healthy young and elderly persons of both genders : 51 young men (24.2±3.6 yrs), 45 young women (23.1±3.2yrs), 51 elderly males, and 44 elderly females. Lower leg anterior, and lower leg posterior muscle thickness was determined using a brightness mode ultrasonographic apparatus. At all sites except for the thigh posterior, the muscle thickness values were significantly greater in the young than in the elderly groups of both genders, even in terms of the ratio of muscle thickness to body mass<SUP>1/3</SUP> (Mt/Wt<SUP>1/3</SUP> ratio), calculated to normalize the morphological differences. The relative difference in muscle thickness between the two age groups was the greatest at the thigh anterior and the least at the thigh posterior in both genders. Between young men and women, the men showed significantly greater muscle thickness and Mt/Wt<SUP>1/3</SUP> ratio at every site than the women. Between the elderly groups, however, Mt/Wt<SUP>1/3</SUP> ratios at all sites, except for the thigh anterior, did not show significant gender-related differences. Relative differences in both muscle thickness and Mt/Wt<SUP>1/3</SUP> ratio between the young men and women were similar among the sites, but between the elderly groups the corresponding values at the thigh anterior were greater than at the other sites. These results indicate that 1) the influence of aging on muscle thickness differs between the muscle groups located in the anterior and posterior sited within the same segment, 2) for women, the age-related loss of muscle thickness at the thigh anterior is relatively greater as compared to those at the other sites of the lower limb.
ABSTRACT
The purpose of this study was to investigate the viscoelastic properties of tendon structures in humans. Elongation of the tendon and aponeurosis of medial gastrocnemius muscle (MG) was directly measured by ultrasonography, while subjects (N=12) performed ramp isometric plantar flexion up to the voluntary maximum, followed by a ramp relaxation. The relationship between estimated muscle force (Ff) and tendon elongation (dL) was fitted to a linear regression, the slope of which was defined as stiffness of the tendon structures. The hysteresis was calculated as the ratio of the area within the Ff-dL loop (elastic energy dissipated) to the area beneath the load portion of the curve (elastic energy input) . The resulting Ff-dL relationship was non-linear in form, as previously reported on animal and human tendons in vitro. The mean stiffness was 24.0±5.6 N/mm. However, there was a considerable inter-subject variability (15.8 to 36.8 N/mm) . The Young's modulus, i. e., the slope of the stress-strain curve, was 280 MPa, which tended to be lower than the previously reported values for human tendons. It was also found that the strain of the tendon structures was homogeneously distributed along its length. The mean hysteresis (energy dissipation) was 23.4±12.4%. However, again there was a considerable inter-subject variability (8.7 to 39.3%) . The present results indicated that the tendon structures of human MG was considerably compliant and its hysteresis was in accordance with previously reported values.
ABSTRACT
The pourpose of this study is to investigate the differences in muscle thickness between males and females of Japanese elite athletes. Subjects were 82 males and 65 females who were Japan candidates for the 1986 Asian and the 1988 Olympic Games 8 sports events, e, g., sprinters, middle and long distance runners, throwers, swimmers, gymnasts, volleyball players, basketball players, and oarsmen. Muscle thicknesses were measured by using B-scan ultrasound equipment with a 5 MHz transducer at the follwing sites: forearm anterior, biceps, triceps, subsucapular, abdomen, quadriceps, hamstrings and posterior calf. In results, comparison in muscle thickness between males and females were made at upper extremity (forearm+biceps+triceps), trunk (subsucapular+ abdomen) and lower extremity (quadriceps+hamstrings+calf) . Males showed siginificantly higher values in muscle thickness than females at all sites, except for trunk of distance runners and lower extremity of volleyball players. Relative values of females to males in muscle thickness were 59-84% for upper extremity, 68-89% for trunk, 84-94% for lower extremity. At upper extremity and trunk, Males indicated significantly higher values in muscle thickness per body height (muscle thickness/Ht) execpt for distance runners. At lower extremity, however, there were no siginificant differences in muscle thickness/Ht at lower between males and females except for gymnasts. Relative values of females to males in muscle thickness/Ht were 66-94% for upper extremity, 72-99% for trunk and 89-100% for lower extremity. Males showed significantly higher values in upper/lower extremity ratio of muscle thickness than females, except for sprinters and distance runners. On the other hand, females had significantly higher values in lower/trunk ratio of muscle thickness than males, except for distance runners and gymnasts. These results indicate that the differences in muscle thickness between males and females exist remarkably at upper extremity and trunk commpared to lower extremity. These anatomical differences in the degree of muscle development may be refered to genetic and/or enviromental factors.
ABSTRACT
To investigate the relationship between maximal aerobic power (VO<SUB>2</SUB>max) and fatigu-abililty during repeated isokinetic contractions, 39 male speed skaters (mean 20.8 years) served as subjects. They were divided into two groups according to their VO<SUB>2</SUB>max levels ; high VO<SUB>2</SUB>max group (HI, n=19) and low VO<SUB>2</SUB>max group (LO, n=20) . VO<SUB>2</SUB>max was measured in all subjects during incremental exercise on a bicycle ergometer and body composition was determined by densitometry. Cross-sectional area (CSA) of the leg extensor muscles was evaluated using ultrasonic method. Fatiguability was assessed during the fatigue test consisting of 50 repeated isokinetic knee-extensions at an angular velocity of 180 deg⋅sec<SUP>-1</SUP>. Remark-able findings include :<BR>1. There were no significant differences in body composition and thigh composition between the two groups except for high subcutaneous fat in group LO.<BR>2. There were significant differences in VO<SUB>2</SUB>max between group HI (3.93<I>l</I>⋅min<SUP>-1</SUP>, 67.3 m<I>l</I>⋅kg LBM<SUP>-1</SUP>⋅min<SUP>-1</SUP>) and group LO (3.59<I>l</I>⋅min<SUP>-1</SUP>, 59.9 m<I>l</I>⋅kg LBM<SUP>-1</SUP>⋅min<SUP>-1</SUP>) .<BR>3. In the fatigue test, the average initial values did not differ, however, the average final values were higher in group HI. Also, a significant difference was observed in per unit CSA between the two groups.<BR>4. Higher peak forces (kg) in group HI were observed after the initial 30 dymanic contractions per unit CSA and % of peak values (% peak force) .<BR>5. A close relationship was demonstrated between VO<SUB>2</SUB>max per LBM and the fatigue index, i. e., the mean decline in peak force with 50 contractions (r=-0.37, p<0.05) .<BR>Based on the present findings it is suggested that maximal aerobic power (VO<SUB>2</SUB>max) influences the rate of fatigue development even during short-term maximal isokinetic contractions, and that there may be some physiological cross-linkages between cardiopulmonary regulation and the metabolic properties of skeletal muscles. This finding is also in conformity with earlier results indicating the importance of oxygen delivery as a limiting factor for muscle performance.