Association between accelerometer-measured physical activity and muscle capacity in middle-aged postmenopausal women.

Objective: Greater muscle strength and power are associated with better physical function in middle-aged and older women. The aim of the present study was to determine whether accelerometer-measured physical activity was associated with muscle strength and power in middle-aged postmenopausal women.
Methods: Postmenopausal women (N = 60; mean [SD] age, 58.9 [3.9] y) were assessed for physical activity (step count and moderate to vigorous physical activity [MVPA]) via accelerometer, for body composition via dual-energy x-ray absorptiometry, for concentric isokinetic knee torque at 60°/s and 180°/s using isokinetic dynamometry, and for leg extensor power with the Nottingham power rig.
Results: In linear regression analysis, daily step count was independently associated with isokinetic knee torque at 60°/s (standardized β = 0.32, P = 0.01), isokinetic knee torque at 180°/s (standardized β = 0.32, P = 0.01), and total leg extensor power (β = 0.36, P = 0.01) after adjustment for covariates. Daily MVPA had similar associations with isokinetic knee torque at 60°/s (β = 0.38, P < 0.01), isokinetic knee torque at 180°/s (β = 0.41, P < 0.01), and leg power (β = 0.31, P = 0.02). Analysis of covariance indicated that women who engaged in MVPA for 30 minutes or more per day produced significantly greater isokinetic knee torque (60°/s and 180°/s) and leg extensor power compared with women not meeting this guideline (all P < 0.05).
Conclusions: These findings suggest that daily step count and MVPA are independently associated with muscle strength and power in middle-aged postmenopausal women. Future studies should determine whether interventions that increase habitual physical activity in middle-aged women are associated with concomitant improvements in muscle capacity.