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

OBJECTIVES: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.