Chad R Straight1, Anne O Brady2, Ellen M Evans3. 1. University of Georgia, Department of Kinesiology, 330 River Road, Athens, GA 30602, United States. Electronic address: chad1419@uga.edu. 2. The University of North Carolina at Greensboro, Department of Kinesiology, 1408 Walker Avenue, 237K HHP Building, Greensboro, NC 27402, United States. Electronic address: aobrady@uncg.edu. 3. University of Georgia, Department of Kinesiology, 330 River Road, Athens, GA 30602, United States. Electronic address: emevans@uga.edu.
Abstract
OBJECTIVES: The aim of this study was to examine the relative contributions of physical activity, adiposity, lean mass and muscle quality to lower-extremity physical function (LEPF) in older women. STUDY DESIGN: Cross-sectional analysis at a university research laboratory. MAIN OUTCOME MEASURES: Community-dwelling older women (n=96, 73.9 ± 5.6 years, BMI=26.5 ± 4.7 kg/m(2)) were assessed for body composition via dual-energy X-ray absorptiometry, leg extension power using the Nottingham power rig, muscle quality (W/kg) as the ratio of leg extension power (W) to lower-body mineral free lean mass (kg) and moderate-intensity physical activity via questionnaire. A composite measure of LEPF was calculated by summing Z-scores of the 6-min walk, 8-foot up-and-go and 30-s chair stand tests. RESULTS: Muscle quality and physical activity were associated with all measures of LEPF (all p<0.01). Relative adiposity was related to the 6-min walk and 30-s chair stand (both p<0.01); lower-body mineral-free lean mass was not related to any measure of LEPF (p>0.05). Hierarchical linear regression analyses revealed that muscle quality (standardized β=0.47, p<0.01) and relative adiposity (β=-0.33, p<0.01) were the strongest independent predictors of composite LEPF Z-score explaining 24% and 17% of the variance, respectively. CONCLUSIONS: Muscle quality and relative adiposity are the strongest independent predictors of LEPF in older women. These findings suggest that maintaining muscle quality, especially relative to adiposity, may be a critical target for interventions to prevent declines in physical function in older women.
OBJECTIVES: The aim of this study was to examine the relative contributions of physical activity, adiposity, lean mass and muscle quality to lower-extremity physical function (LEPF) in older women. STUDY DESIGN: Cross-sectional analysis at a university research laboratory. MAIN OUTCOME MEASURES: Community-dwelling older women (n=96, 73.9 ± 5.6 years, BMI=26.5 ± 4.7 kg/m(2)) were assessed for body composition via dual-energy X-ray absorptiometry, leg extension power using the Nottingham power rig, muscle quality (W/kg) as the ratio of leg extension power (W) to lower-body mineral free lean mass (kg) and moderate-intensity physical activity via questionnaire. A composite measure of LEPF was calculated by summing Z-scores of the 6-min walk, 8-foot up-and-go and 30-s chair stand tests. RESULTS: Muscle quality and physical activity were associated with all measures of LEPF (all p<0.01). Relative adiposity was related to the 6-min walk and 30-s chair stand (both p<0.01); lower-body mineral-free lean mass was not related to any measure of LEPF (p>0.05). Hierarchical linear regression analyses revealed that muscle quality (standardized β=0.47, p<0.01) and relative adiposity (β=-0.33, p<0.01) were the strongest independent predictors of composite LEPF Z-score explaining 24% and 17% of the variance, respectively. CONCLUSIONS: Muscle quality and relative adiposity are the strongest independent predictors of LEPF in older women. These findings suggest that maintaining muscle quality, especially relative to adiposity, may be a critical target for interventions to prevent declines in physical function in older women.
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