CHANGES IN MUSCLE THICKNESS AND MECHANICAL POWER IN JAPANESE MIDDLE AND OLD AGED WOMEN

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In order to study the decrease in mechanical power with aging, force-velocity characteristics and maximum power were examined during upper and lower limb human movements. Subjects were 167 healthy middle and old aged Japanese females aged 31 to 82 yrs who did not participate in any daily physical exercise activity programs. They were fully informed the contents and signed to consensus of this project. Special dynamometer was developed for the measurements of peak power (Pp), force (Fp) and velocity (Vp) during mono and multi articular movements such as elbow flexion (EF), knee extension (KE), hip flexion (HF) and gh clean (HIC). In each movements, Pp and Fp-Vp relations were obtained from different several loads of the dynamometer which was provided by the electrically controlled powder brake system. Muscle thickness was measured by ultrasound technique. Mean values of Pp for EE,KE,HF and HIC were 108,332,141 and 486W for thirties and 62,131,55 and 206W for seventies, respectively. Decreased ratio in power with aging had tendency to be higher in lower limb movements compared to that of upper movement. Decreased ratio were 61% for KE and HF,58% for HIC and 43% for EF.Decrease in muscle thickness with aging was more pronounced in lower limb (Quardriceps femoris) than upper one (Biceps brachii). From the force-velocity relations with aging, decrease in force was obvious than velocity for lower limb movements such as KE,HF and HIC movements. It was concluded that the larger decrease in power with aging in lower limb movements was mainly caused from the decrease in force than velocity of muscle contraction. This finding suggests the necessity of muscle strength training for middle and old aged women particularly to the lower limb musculature for preventing the drop-off in mechanical power with aging.