This study investigated the relationship between age-related declines in muscle thickness of the lower extremities and daily physical activity in elderly women. The subjects comprised 20 young women and 17 elderly women residing in a nursing home. Lower limb muscle thickness was measured by B-mode ultrasound with the following 10 muscles; gluteus maximus, gluteus medius, gluteus minimus, psoas major, rectus femoris, vastus lateralis, vastus intermedius, biceps femoris, gastrocnemius and soleus. Daily physical activity was evaluated using life-space assessment (LSA) which assessed the life-space level, degree of independence, and frequency of attainment. Muscle thickness in the gluteus maximus, gluteus medius, gluteus minimus, psoas major, rectus femoris, vastus lateralis, vastus intermedius, biceps femoris and gastrocnemius, but not soleus, was significantly greater in the young group than the elderly group. The greatest rates of age-related loss of skeletal muscle mass in the lower limbs showed in the psoas major, while the smallest loss showed in soleus muscle. Only the gluteus medius was significantly associated with the LSA score (r = 0.528, p < 0.05) in elderly women. These results suggest that the reduction in skeletal mass with age is smaller in soleus muscle, and that the age-related decline in gluteus medius muscle is influenced by daily physical activity.
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