Abstract
The purpose of this study was to investigate the hypothesis that the reduction in walking ability is due to muscle atrophy in the lower limb muscles with aging using equational structure modeling as well as investigate the influence of muscle on walking ability. The subjects consisted of 127 persons (57 males and 70 females) aged 20-84 year, who were grouped into 6 age brackets of 20-39, 40-49, 50-59, 60-69, 70-74, and 75 or older. Using MRI, muscle cross-sectional area was measured on psoas major and thigh muscle (divided into extensor and flexor) . For walking patterns, each subject walked along a 7-m walking passage at normal speed for VTR-recording of the motion. The resulting pictures were used to analyze stride length, trunk inclination and walking speeds. Walking speeds showed a statistically significant decrease in value from the 50's age group in males and the 60's age group in females when compared with the 20-39 age bracket (p<0.05) . In males, a significant co-relationship was observed only between the muscle cross-sectional area of thigh extensor and walking speed (p<0.01) while in females, a significant co-relationship was found between the muscle cross-sectional area of psoas major (p<0.001) /thigh muscle extensor (p<0.01) and walking speed. These results indicate that the muscle atrophy with aging in psoas major and thigh muscle extensor is a factor responsible for the decrease in walking speed. Meanwhile, a difference in sex was observed between the muscle cross-sectional area of psoas major and walking speed. It was considered that the muscle atrophy rate of the female's psoas major being higher than the male's influenced this. Furthermore, it was suggested possibility that the decline of walking ability is due to decreased muscle mass of the lower limbs with aging.
