Objective: Poor physical function performance is associated with risks for disability in late life; however, determinants of physical function are not well characterized in middle-aged women. The aim of this cross-sectional study was to examine the contributions of body composition, physical activity, muscle capacity, and muscle quality to physical function performance.
Methods: Postmenopausal women (N = 64; mean [SD] age, 58.6 [3.6] y) were assessed for body composition via dual-energy x-ray absorptiometry, for physical activity via accelerometer (steps per day), and for physical function via Timed Up and Go, 30-second chair stand, and 6-minute walk. Leg strength was assessed using isokinetic dynamometry at 60[degrees] second-1. Leg power was assessed with the Nottingham Leg Extensor Power Rig. Muscle quality was calculated as (1) the ratio of leg strength at 60[degrees] second-1 to upper leg lean mass and (2) the ratio of leg power to total lower body lean mass.
Results: Regression analyses revealed the following: (1) age and muscle quality calculated with leg power are independently related to Timed Up and Go, explaining 12% and 11% of the variance, respectively (P < 0.05); (2) age and muscle quality calculated with leg strength are independently related to 30-second chair stand, explaining 12% and 10% of the variance, respectively (P < 0.05); and (3) number of medical conditions, muscle quality calculated with leg strength, steps per day, and adiposity are independent predictors of 6-minute walk, collectively explaining 51% of the variance.
Conclusions: In postmenopausal women, a more optimal body composition (including lower adiposity and higher lean mass) and higher levels of physical activity are associated with better physical function performance at midlife.
(C) 2014 by The North American Menopause Society.