Association Between Muscle Mass, Leg Strength, and Fat Mass With Physical Function in Older Adults: Influence of Age and Sex

OBJECTIVE: The purposes of this study were to determine the relationship between muscle mass, muscle strength, muscle quality, and fat mass with a composite measure of physical function in older adults, and to determine whether these relations differed by age and sex. METHOD: Participants consisted of 1280 adults aged ≥ 55 yr from the NHANES study. Reduced rank regression was used to identify patterns of muscle mass, muscle strength, muscle quality, and fat mass related to physical function. RESULTS: A single relevant pattern emerged that included leg strength and fat mass as predictors of the 7 physical function variables. The leg strength loading was significantly greater than the fat mass loading in men and women aged 55-64 and ≥ 75, and differed between sexes. CONCLUSION: Leg strength and fat mass best predict physical function in older adults and the relative importance varies according to age and sex.