Isometric handgrip training improves local flow-mediated dilation in medicated hypertensives

Bilateral isometric handgrip (IHG) training lowers resting arterial blood pressure (BP) in medicated hypertensives. Numerous mechanisms have been suggested, but have yet to be investigated. One such mechanism is that of improved systemic endothelial-dependent vasodilation. The purpose of this investigation was twofold: (1) to determine if bilateral IHG training had any beneficial effects on endothelial-dependent vasodilation, and (2) to see if improved systemic endothelial-dependent vasodilation was responsible for lowering BP. Sixteen participants performed four, 2 min IHG contractions at 30% of their maximal voluntary effort, using either a bilateral (n = 7) or a unilateral IHG protocol (n = 9), three times per week for 8 weeks. Brachial artery (BA) flow-mediated dilation (FMD, an index of endothelial-dependent vasodilation, measured in both arms) was assessed pre- and post-training. Following bilateral IHG training, BA FMD improved in both arms (normalized to peak shear rate 0.005 ± 0.001 to 0.02 ± 0.002 s⁻¹, P < 0.01). Following unilateral IHG training, BA FMD improved in the trained arm only (normalized 0.009 ± 0.002 to 0.02 ± 0.005 s⁻¹, P < 0.01). These findings suggest that although IHG training improves endothelial-dependent vasodilation, the improvements only occur locally in the trained limbs. This suggests that enhanced systemic endothelial-dependent vasodilation is not the mechanism responsible for the observed post-IHG training reductions in BP in medicated hypertensives.