Asymmetry in leg extension power impacts physical function in community-dwelling older women.

Objective: The aim of this study was to examine the association between asymmetry in leg extension power (LP) and lower-extremity physical function (LEF) in community-dwelling older women.
Methods: Older women (n = 94, 74.0 ± 5.5 y) were assessed for unilateral LP (watts) using the Nottingham power rig, and absolute and relative (%ASYM) differences in LP between the dominant and nondominant legs were calculated. LEF was assessed via the 6-minute walk, 8-foot up-and-go and 30-second chair stand, and a composite measure of LEF was calculated by summing z scores of each test. In addition, body composition was measured via dual-energy x-ray absorptiometry and moderate-intensity physical activity was assessed via questionnaire.
Results: The absolute difference in LP between the dominant and nondominant legs was 10.2 ± 9.0 watts, which translated to a %ASYM of 11.3% ± 10.5% (P < 0.01). %ASYM had bivariate associations with all individual measures of LEF (r range = -0.22 to -0.34, all P < 0.05). Using multivariate linear regression, %ASYM was an independent predictor of a composite LEF z score (standardized β= -0.18, P < 0.05) after adjustment for age, comorbidities, physical activity, relative adiposity, and total leg power. Analysis of covariance indicated that women with low asymmetry had a significantly better LEF z score than those with high asymmetry (0.60 vs -0.13, P = 0.04).
Conclusions: These findings indicate that a greater magnitude of asymmetry in LP is associated with poorer LEF in older women. Research is needed to determine whether interventions that correct asymmetries in lower-body muscle power confer functional benefits in older women.