Left ventricular systolic function during isometric handgrip exercise and post-exercise circulatory occlusion in healthy male and female adults

Post-exercise circulatory occlusion (PECO) stimulates metabolically senstitive afferents, activating the muscle metaboreflex and eliciting a greater blood pressure response in males than females, possibly owing to greater absolute exercise workloads that contributes to disproportionate increases in stroke volume (SV). We tested the hypotheses that isometric handgrip exercise (EX) and PECO would increase SV greater in males than females, and accounting for strength would negate differences. Ten males and 10 females underwent cardiac MRI during rest, EX, and PECO. SV, end-systolic (ESV) and end-diastolic volume (EDV), all indexed to body surface area, and wall stress, systolic blood pressure (SBP) and total peripheral resistance (TPR) were measured. EX and PECO lowered SVi in males (both P<0.001) but not females (both P=0.998). The reduction in SVi during EX and PECO in males remained with ANCOVA (covariate handgrip strength; P=0.020). EX increased ESVi in both sexes ( P≤0.018), whereas ESVi increased during PECO in males ( P<0.001) but not females ( P≥0.092). EX and PECO increased EDVi, SBP, TPR, and wall stress (all P≤0.015) in both sexes. The SVi response to PECO was negatively related with ESVi responses in males ( r=-0.822, P=0.004) but not females ( P=0.216). PECO lowers SVi in males but not females independent of handgrip strength, despite comparable pressor responses. These novel findings support differential afterload sensitivity on SV between sexes in response to the exercise pressor and muscle metaboreflex reflex. Remarkably, SV is not augmented as part of the pressor response elicited by isometric handgrip exercise or muscle metaboreflex activiation in either sex.