Acute effects of volume-matched isometric exercise intensity on vascular function and autonomic regulation in men with elevated blood pressure

Abstract

Isometric exercise (IE) has been introduced as an effective non-pharmacological strategy for blood pressure (BP) management; however, the influence of exercise intensity remains unclear during lower-limb IE. This study investigated the acute effects of volume-matched high-intensity (HIIE) and low-intensity IE (LIIE) on cardiovascular function in men with elevated BP. Seventeen men with prehypertension or stage I hypertension completed three randomized crossover conditions, including HIIE (60% of maximal voluntary contraction (MVC)), LIIE (30% of MVC), and a non-exercise control condition (CON). BP, heart rate variability (HRV), brachial-ankle pulse wave velocity (baPWV) were measured at baseline and three different time points during recovery, while flow-mediated dilation (FMD) was measured at baseline and 30-min post-exercise. No significant BP reduction was observed. However, HIIE induced greater autonomic disturbance with elevated heart rate and reduced HRV indices during recovery (p < 0.05). Right baPWV decreased following HIIE (p < 0.05) while FMD increased after both exercise conditions (p < 0.001). Our findings suggest that volume-matched HIIE induces greater acute autonomic and vascular responses than LIIE in men with elevated BP, despite no immediate changes in BP. HIIE may provide a stronger physiological stimulus associated with vascular adaptation.