Abstract

Introduction: Aging is a complex physiological process whose main feature is the progressive loss of functionality, which may be delayed or attenuated by improving physical fitness. Objective: To determine the association between leg strength and the muscle cross-sectional area of the quadriceps femoris in relation to physical activity level in the elderly. Materials and methods: Thirty-two functionally autonomous people over 80 years (men: 82.80 +/- 2.09 years; women: 83.77 +/- 4.09 years) participated in this study. The Barthel Index, the Yale Physical Activity Survey and the Chair Stand Test were the instruments used. Results: There were significant differences between sexes in muscle area (p0.001) in the Chair Stand Test (p=0.028) and the walk index (p=0.029), with higher values in men. The muscle area and the Chair Stand Test correlated significantly with the walk index (r=0.445, p0.005, and r=0.522, p0.001, respectively) and the total weekly activity index (r=0.430, p0.005, and r=0.519, p0.001, respectively). In the multiple linear regression models for the total weekly activity index, muscle area and the Chair Stand Test, only the latter behaved as a predictor variable. Conclusions: Muscle strength and muscle mass of quadriceps showed a significant association with the physical activity level in older people. Leg muscle strength was useful to reveal muscle mass and physical activity level in older people, which is relevant as a clinical practice indicator.