The ability to walk is just as important for the elderly as it is for young people. In fact, in the elderly, decreased mobility limits function in daily life and can lead to more serious situations (e.g., becoming bedridden) . The elderly population has increased over the last decade, and many researchers have studied the mobility of the elderly. However, the focus of most studies has been to facilitate recovery of bedridden individuals and prevent the elderly from becoming bedridden, and particularly to prevent fall-induced fractures, which often cause the elderly to become bedridden. However, about 70-80% of the elderly population do not require care, and it is necessary to conduct research on the maintenance of activities of daily living to make it possible for the elderly to work or volunteer. From this perspective, mobility is an important physical factor. Mobility is dependent on muscle activity and it has long been known that aging reduces muscle mass. Therefore, it is feasible to assume that reduced muscle mass leads to decreased ability to walk, and we have proven that there is a close correlation between the two. When presenting the idea of strength training to the elderly, it is appropriate to focus on the maintenance and improvement of mobility, not on the training itself. The results of our research can be summarized as follows:
Muscle mass decreases with age, with the legs being affected to a greater degree than the arms. Moreover, muscle atrophy is dependent on weakening of muscle fibers, especially fast-twitch (Type II) fibers. Reduced lower limb muscle mass increases the risk of falling and can decrease walking ability to a degree that can affect daily living activities.
In order to improve reduced muscle mass in aging, it is important to use an exercise program that is designed to strengthen fast-twitch fibers, which can be followed even by the elderly. Since walking therapy mostly mobilizes slow twitch fibers, it is not effective in preventing and improving muscle atrophy. It is important to have an exercise program that is designed to mobilize fast-twitch fibers.

In order to clarify the effect of exercise on the walking performance and the muscle volume in lower limbs, elderly athletes long continuing to be trained and untrained elderly were compared with regard to their muscle cross-sectional area (CSA) of m. psoas major, thigh muscle and crus muscle and their walking ability. The subjects used consisted of thirty-six 80's-aged male and 70's-aged female elderly athletes and twenty-four elders having no regular exercise (control male group : CM, control female group : CF) . The elderly athletes were further divided into two groups in accordance with their results of Japan Fitness Test (high performance male group : HPM, low performance male group : LPM, high performance female group : HPF, low performance female group : LPF) . The walking performance was evaluated by analyzing their walking speed, stride-length and step rate during walking along a 15 m-strip of passage at normal and fast paces using videotaping. The muscle CSA was determined at m. psoas major, thigh muscle (extensors and flexors) and crus muscle (m. tibialis anterior and m. triceps surae) using MRI. As for the walking speed and stride-length at the normal pace, only HPM and HPF showed significantly higher values than CM and CF (male : p<0.05, female : p<0.01) . Meanwhile at the faster pace, HPF and LPF showed significantly higher values than CF in female (HPF : p<0.01, LPF : p<0.05) and in the case of males, only HPM have a higher value only of the walking speed than CM (p<0.05) . The CSA of m. psoas major in HPM and HPF significantly higher than that in CM and CF (all p<0.05), while in CSAs of knee extensor muscles and m. triceps surae, the statistical differences were not consistent among male and female groups. The results suggested that greater muscle mass of m. psoas major could influence higher walking speed in elderly people, and might be affected by regular exercise training.