Influence of menopausal status on the main contributors of muscle quality.

Background: Muscle quality is a strong independent predictor of physical function. Body mass and fatness, muscle mass and cardiorespiratory fitness are known to influence muscle quality.Objective: To identify the contributors of muscle quality in young and postmenopausal women and whether hormone replacement therapy (HT) could influence this relationship at the age of menopause.Methods: Fifty-four postmenopausal women, 27 not on HT (PMW) and 27 on HT (PMW-HT), and 33 young women (YW) were evaluated for (1) body composition (body mass index, BMI), total fat mass (FM, %), appendicular lean mass (ALM, in kg and %), and appendicular skeletal mass index (ASMI=ALM/height(2) in kg/m(2)); (2) absolute peak oxygen uptake (VO2peak, in ml/min) and relative peak oxygen uptake (VO2peakRel in ml/kg/min); and (3) absolute isometric knee extension strength (iKES in kg) and relative isometric knee extension strength (iKES/BMI and iKES/ALM).Results: YW, PMW and PMW-HT had similar BMI (32.110.2, 27.3 +/- 4.7 and 26.7 +/- 4kg/m(2)) and FM (39.8 +/- 10.0, 39.8 +/- 7.3 and 39.9 +/- 7.1%), respectively. Correlations were found between iKES/BMI index and FM (r=-0.52), ALM (r=0.32) and VO2peak (r=0.31). Regression analysis demonstrated that, in YW, total amount of variance in iKES/BMI was mostly explained by ALM (42%), whereas, in PMW and PMW-HT, it was cumulatively explained by FM along with VO2peakRel (34 and 46%, respectively).Conclusion: The main contributors of muscle quality differ between young and postmenopausal women and HT does not seem to influence this relationship.