Sex dimorphism in cardiac and aerobic capacities: the influence of body composition

Abstract

Objective: The contribution of body composition to sex differences in strong prognostic cardiorespiratory variables remains unresolved. This study aimed to elucidate whether body composition determines sex differences in cardiac and oxygen (O2) uptake responses to incremental exercise. Methods: Healthy moderately active women and men (n=60, age=60.7±12.3 yr) matched by age and cardiorespiratory fitness were included. Body composition was determined via dual-energy x-ray absorptiometry. Transthoracic echocardiography and O2 uptake were assessed at rest and throughout incremental exercise with established methods. Major cardiac and pulmonary outcomes were normalized by body surface area (BSA), total or leg lean body mass (LBM). Results: Women presented smaller anthropometrical indices (height, weight, BSA) and LBM compared with men (P<0.001). Peak exercise cardiac dimensions and output (Qpeak), commonly normalized by BSA, were reduced in women relative to men (P≤0.019). Cardiac sex differences were abolished after normalization by total or leg LBM (P≥0.115). Strong linear relationships of total and leg LBM with Qpeak and VO2peak were detected exclusively in women (r≥0.53, P≤0.003), independently of body fat percentage. Conclusions: Total and leg LBM stand out as strong independent determinants of cardiac and aerobic capacities in women, regardless of body fat percentage, relationships not present in age- and fitness-matched men.