Impact of body mass index on blood pressure and cardiovascular adaptation to isometric exercise training

Obesity is characterised by excess adipose tissue, which impairs vascular function and blood pressure (BP) regulation. However, it remains unclear whether adiposity influences the BP-lowering response to isometric exercise training (IET). This randomised-controlled trial explored the impact of body mass index on BP and cardiovascular adaptation following IET. 80 participants with normal to high-normal systolic BP (range 120-140 mmHg) were recruited for the study. Participants were randomised into two BMI groups: normal BMI (18.5-24.9 kg/m²; n=40) and high BMI (25-34.9 kg/m²; n=40) and then either performed home-based lower-body IET, 3 times per week, for 4 weeks (each session comprised 4 x 2-minute bouts), or were allocated to the control group. Cardiovascular variables, including BP, total peripheral resistance (TPR), and heart rate variability (HRV), were measured at rest pre- and post-intervention. Overall, there were significant reductions in systolic BP, diastolic BP and mean arterial pressure (MAP) in the IET group compared to control. However, the normal-BMI group had significantly greater reductions in diastolic BP (- 8.5 [- 11.8, - 5.3] mmHg) and MAP (- 9.2 [- 11.9, - 6.6] mmHg) compared to the high-BMI group (dBP: - 2.6 [- 6.2, 1.1]; MAP: -4.7 [- 7.6, - 1.8]). Although TPR was significantly greater in the high-BMI group at week 4 (p=0.022), it was also elevated at baseline, and change-score analyses revealed no significant between-group difference in the magnitude of TPR reduction (Δ p=0.964). These findings indicate that BMI may modulate the BP-lowering response to IET, suggesting that individuals with higher BMI may require adjunctive or prolonged interventions to optimise BP reduction.