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.

This study aimed to estimate in vivo 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_BB) 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_BB was curvilinear and consisted of an initial region characterized by a large increase in tendon length with increasing F_BB 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.

Muscle strength per unit muscle area related to age was investigated in normal 131 males and 127 females, 7 to 18 years of age. A cybex machine was used to measure the isometric muscle strength of elbow flexion and extension, knee flexion and extension, respectively. The cross-sectional muscle area of extensor and flexor at right upper arm and thigh were determined by using ultrasonic apparatus. The muscle area in male increased with age from 7 years to 17 or 18 years. Females showed increment in muscle area from 7 to 12 years for elbow flexor muscle, and from 7 to 16 years for another muscles. Muscle strength in both males and females increased with age from 7 to 16 or 17 years. Muscle strength per unit muscle area tended to increase with age in males from 7 to 12 years, and in girls 7 to 9 years except for elbow extension. The strength per area under 12 years of age for males and 9 years of age for females except for elbow extension were significantly lower than that of the above age. There were little differences in the strength per unit area with age among males from 13 to 18 years and females from 10 to 18 years, respectively. These results indicate that under 12 years for boys and 9 years for girls the increment in muscle area with age is not accompanied with the development of muscle function.

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 (VO₂). VO₂ and HR was normalized to maximal VO₂ (%VO₂max) 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_MVC). Time that cardiorespiratory parameters became stable was 4-6 min in both exercises. VO₂, %VO₂max, 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_MVC 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.

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.

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^1/3 (Mt/Wt^1/3 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^1/3 ratio at every site than the women. Between the elderly groups, however, Mt/Wt^1/3 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^1/3 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.

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.

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.

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.

The purpose of the present study is to observe the accuracy of the ultrasonic A-mode method for measuring subcutaneous fat thickness. Nine healthy adults (4 males and 5 females) volunteered as experimental subjects. The skin and subcutaneous fat thickness at four different positions, the anterior, posterior, medialis and lateralis of the forearm, upper arm, leg and thigh, were measured by means of an A-mode ultrasonic subcutaneous fat caliper (CANON, CH 300-FT) and also by a B-mode method (ALOKA, SSD-120, ECHOVISION, Circular compound scanner) . Correlation coefficients of subcutaneous fat thickness between both ultrasonic methods were 0.808 for the forearm, 0.780 for the upper arm, 0.833 for the leg and 0.843 for the thigh with a statistical significance of 0.1 % level, respectively.
Differences of the thickness of subcutaneous fat between both methods were from 0.6 to 2.0mm as every absolute mean values. No significant differences were observed for mean subcutaneous fat thickness between both methods at each position. From these results, the A-mode ultrasonic method (CANON, CH 300-FT) is considered to be useful for measuring the thickness of skin and subcutaneous fat in human limbs.