Sex Differences In Physiological Responses During Acute Exercise: Heritage Family Study

PURPOSE: Studies reporting on acute exercise responses typically involve more males than females and are underpowered to understand sex differences. Given recent efforts to understand the role of sex as a biological variable in biomedical research, we elucidate its impact on acute exercise responses among a large cohort of physically inactive male and female participants. METHODS: We performed cardiopulmonary exercise testing in 846 individuals from the HERITAGE Family Study (mean age: 34 years, 55% female) and measured 53 responses reflecting cardiorespiratory fitness, cardiac output, peripheral oxygen utilization, and blood pressure. We utilized a principal component analysis for unbiased exploration of the sources of variability in acute exercise responses. We also performed two sample t-tests on exercise traits scaled to body size to ascertain whether sex differences remain after accounting for body size. RESULTS: Sex was strongly correlated with the primary principal component in the overall acute exercise response (Figure 1). We observed sex differences in nearly all acute exercise traits. Male participants exhibited higher values of V̇O2max, maximal stroke volume, and arterio-venous oxygen difference (males vs females, V̇O2max: 36 vs 27 ml·kg − 1·min − 1, p < 0.001; maximal stroke volume: 57 vs 48 ml/m2, p < 0.001; maximal arterio-venous oxygen difference: 14 vs 12 ml/dL, p < 0.001). During submaximal exercise, male participants demonstrated a higher V̇O2 at anaerobic threshold (18 vs 17 ml·kg − 1·min − 1, p < 0.001), but had a lower anaerobic threshold as a percentage of V̇O2max (51 vs 60%, p < 0.001) compared to female participants. There were no sex differences in the blood pressure response at a fixed workload (systolic blood pressure at 50 W: 149 vs 147 mmHg, p = 0.2). CONCLUSIONS: Marked sex differences are present in the global acute exercise response, as well as in individual exercise traits even after rigorously accounting for body size and composition.John S. LaDue Memorial Fellowship at Harvard Medical School