Correlation of physical function with the thickness of multiple muscles of the quadriceps femoris in community-dwelling elderly individuals

Purpose: The purpose of this study was to clarify the reference values of muscle thicknesses by age and to elucidate the association of muscle thickness with physical function in a large group of community-dwelling elderly individuals. Participants and methods: The muscle thicknesses of the rectus femoris (RF), vastus intermedius (VI), and quadriceps femoris (QF) in 777 of 831 enrolled elderly individuals were measured by ultrasonography, and physical function was measured using knee extension strength (KES), one-legged stance, walking, Timed Up and Go, and grip strength tests. Muscle thickness data were divided by sex and categorized into 5-year age groups. Differences in muscle thickness and KES among the age groups were examined, and correlations between muscle thickness and physical function test results were compared by age. The non-parametric independent two-sample Mann-Whitney U-test, Kruskal-Wallis test, and Spearman's correlation coefficients were used in the statistical analysis. Results: Thickness of the RF showed fewer significant differences among all groups and less decreases compared to thickness of the VI in older age groups, especially in men. Thicknesses of the RF, VI, and QF correlated with KES in almost all the thicknesses of muscles in the 65 69 and 70-74 years age groups in men and in almost all age groups in women. The decrease in muscle thicknesses and degree of correlations with aging were different between men and women. Conclusions: Reductions in the thicknesses of the muscles and KES differed by age group and sex. Our results could be used for prescribing exercise in community-dwelling elderly individuals of varying ages.