Sex differences in ventricular-vascular interactions associated with aerobic capacity

Aerobic capacity measured by maximal oxygen uptake (VO₂max) is related to functional capacity and is a strong independent predictor of all-cause and disease-specific mortality. Sex-specific cardiac and vascular responses to endurance training have been observed, however, their relative contributions to VO₂max are less understood. The purpose of this study was to evaluate sex-specific ventricular-vascular interactions associated with VO₂max in healthy males and females.

Sixty-eight males and females (38% females, 35 ± 10y) characterised as recreational exercisers to highly trained endurance athletes, and free of chronic disease underwent a cycle ergometer to assess VO₂max. Resting arterial compliance and echocardiographic evaluation of left ventricular (LV) structure and function were measured and indexed to body surface area.

VO₂max was similar between groups (54 ± 6 vs. 50 ± 7 ml/kg/min, p = 0.049). Indexed LV mass (LVMi) was higher (96 ± 15 vs. 81 ± 11, p = 0.001) in males versus females, respectively. Linear regression analysis revealed two models that were significantly associated with VO₂max in males and females. In males, the two models included (1) longitudinal diastolic strain rate and LVMi (r² = 0.31, p = 0.003) and (2) indexed end-diastolic volume (EDVi) and longitudinal diastolic strain rate (r² = 0.34, p < 0.001). In females, the linear regression models included (1) LVMi, large arterial compliance, longitudinal systolic strain rate, and age (r² = 0.69, p < 0.001) and (2) EDVi, large arterial compliance, longitudinal systolic strain rate, and age (r² = 0.52, p = 0.003).

These findings reveal that while in both sexes, LVMi and LVEDVi are associated with VO₂max, arterial compliance was also found to contribute to the variance in VO₂ max in females, but not in males. Further, ventricular relaxation was a significant factor in aerobic capacity in males, while in females ventricular contraction was a significant factor.