Comparison of Age-Related, Site-Specific Muscle Loss Between Young and Old Active and Inactive Japanese Women

Purpose: To compare the effect of habitual recreational sports and exercise activity on age-related, site-specific muscle loss in young and old women in Japan. Methods: Participants included 152 young (aged 20-35 years) and 157 old (aged 60-85 years) women who were classified into 4 subgroups on the basis of their habitual (more than once a week) sports and exercise activity: young active (n = 86), young inactive (n = 66), old active (n = 43), and old inactive (n = 114). Muscle thickness (MTH) and fat thickness (FTH) were measured by ultrasonography at 8 sites, with MTH expressed in terms relative to limb length (MTH/L) or height (MTH/Ht). Percent fat was estimated from FTH, and fat-free mass was calculated. Results: Fat-free mass was similar between younger and older women and between active and inactive women. MTH/L in the quadriceps (P < .001), abdomen (P < .001), and triceps surae (P < .05) was lower in the older women than in the younger women. In contrast, MTH/L in the hamstrings, subscapula, and biceps was higher (P < .01) in the older women than in the younger women. Compared with the MTH of the young inactive women, the MTH of the young active women was greater (P < .05) in 5 sites. Similarly, MTH/L in the quadriceps and triceps was higher (P < .05) in the old active women than in the old inactive women. However, quadriceps MTH/L and abdomen MTH/Ht were still lower (P < .001) in the old active women than in the young inactive women. Conclusion: Age-related muscle loss remains site-specific in both active and inactive young and old women, even when habitual physical activity has an effect on muscle size.