Correlation between Muscle Strength and Muscle Mass, and Their Association with Walking Speed, in Community-Dwelling Elderly Japanese Individuals

Objectives: We aimed to assess the correlation between muscle strength and muscle mass based on sex and age, and their association with walking speed, which is a health predictor for independent living, in elderly Japanese individuals. Methods: The participants included 318 (111 men, 207 women) community-dwelling elderly Japanese individuals aged >= 65 years. Knee extension strength was assessed as an indicator of muscle strength, and bioelectrical impedance analysis was used to measure muscle mass. The maximum walking speed of participants was recorded. All measurements were categorized based on sex and age groups as follows: young-old (age, 65-74 years) and old-old (age >= 75 years). Results: Appendicular muscle mass and knee extension strength decreased with age in both men and women. In men, knee extension strength showed significant positive correlations with leg and appendicular muscle mass in both young-old and old-old age groups. However, in women, only the old-old age group showed significant positive correlations between knee extension strength and leg and appendicular muscle mass. Muscle strength was significantly positively correlated with maximum walking speed in all groups, whereas muscle mass was not significantly correlated with maximum walking speed in men and women. Conclusions: Muscle strength was significantly correlated with muscle mass in both age groups in men. However, in women, the correlation between muscle strength and muscle mass differed according to age. This finding suggests that the relationship between muscle strength and muscle mass differs according to sex and age. Muscle strength showed significant correlation with walking speed in both men and women in both age groups. These findings suggest that it is necessary to recognize that muscle strength is different from muscle mass, and that an individualized approach to prevent decline of muscle strength and muscle mass is necessary for health promotion in elderly.