Sex-based comparison of the blood pressure, haemodynamic and cardiac autonomic adaptations following isometric exercise training in sedentary adults: a randomised controlled trial

Objectives: We aimed to explore sex-specific differences in resting blood pressure (BP) reduction and associated cardiovascular adaptations following isometric exercise training (IET). Methods: 100 sedentary adults with normal to high- normal systolic BP volunteered for the study. Participants either performed home-based lower-body IET in the form of a wall squat three times a week for 4 weeks (each session comprised 4×2 min bouts) or were allocated to the control group. Cardiovascular variables, including BP, cardiac output, total peripheral resistance, stroke volume and heart rate variability (HRV), were measured at rest preintervention and postintervention. Results: Following 4 weeks of IET, there were no significant differences in resting systolic BP and diastolic BP between females (122.1±6.9 and 80.0±8.3 mm Hg) and males (119.6±7.2 and 77.4±8.6 mm Hg). However, female participants had a greater cardiac autonomic response following training, evidenced by a lower low- frequency to high-frequency HRV ratio (F: 1.38±1.27 and M: 2.1±1.5, p=0.004) and decreased and elevated low- frequency normalised units (F: 50.3%±16.2% and M: 60.9%±16.9%, p=0.015) and high-frequency normalised units (F: 49.7%±16.2% and M: 39.1%±16.9%, p=0.015), respectively. Conclusions: While resting BP reductions were comparable between female and male participants, there was a greater autonomic response and a higher incidence of clinically important BP reductions in females, which could indicate a greater cardioprotective effect following IET. These findings highlight the importance of considering sex differences in the prescription and evaluation of exercise interventions for hypertension management.