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° 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° 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.
From the 1University of Georgia, Athens, GA; and 2University of Alabama at Birmingham, Birmingham, AL.
Received December 2, 2013; revised and accepted January 29, 2014.
Financial disclosure/conflicts of interest: C.L.W.-R. has no conflict of interest to declare. A.L.A. has no conflict of interest to declare. M.A.J. currently receives funding from the US Department of Agriculture. E.M.E. has received funding from the National Institutes of Health, US Department of Agriculture and from the Kellogg Company and is currently working on projects funded by the Egg Nutrition Center and the National Cattleman’s Beef Association. L.Q.R. currently receives funding from the National Cancer Institute and the American Institute for Cancer Research and has previously received compensation for continuing medical education talks delivered at Rush Medical Center.
Address correspondence to: Christie L. Ward-Ritacco, PhD, Department of Kinesiology, Ramsey Student Center, University of Georgia, 330 River Road, Athens, GA 30602. E-mail: firstname.lastname@example.org