Using Bilateral and Unilateral Exercise to Better Understand the Blood Pressure Lowering Effects of Isometric Handgrip Training: Preliminary Findings

Isometric handgrip (IHG) training reduces resting blood pressure (BP) in normotensive individuals following 8-10 weeks of unilateral (4 x 2 minute sustained contractions at 30% maximal voluntary contraction (MVC) performed by the non-dominant limb, separated by 4 minutes rest) or bilateral IHG training (contractions alternating between dominant and non-dominant limb, separated by 1 minute rest), performed 3-5 times per week. Investigating the effects of a single bout of unilateral or bilateral IHG on vascular function (brachial artery flow-mediated dilation (FMD) and low-flow mediated constriction (L-FMC)) may provide insight into the underlying hypotensive mechanisms of IHG training. Eight young adult (25.3 ± 3.81 years), normotensive (99.65/61.25 ± 11.72/9.14 mmHg) women performed a single bout of bilateral (n=4) or unilateral (n=4) IHG exercise. FMD and L-FMC were assessed using ultrasound pre- and post-IHG bout. Following a single IHG bout, no significant changes were observed in FMD (unilateral: pre- = 13.56 ± 7.8%, post- =17.26 ± 21%, bilateral: pre- = 17.11 ± 1.1%, post- = 21.18 ± 8.9%) or L-FMC (unilateral: pre- = 3.36 ± 11%, post- =-2.26 ± 16%, bilateral: pre- = -2.86 ± 3.1%, post- = -1.94 ± 9.7%) in either group (all p > 0.05). Taken together these preliminary data suggest that in young healthy women, irrespective of isometric exercise on 1 or 2 limbs, the endothelium is not altered significantly. Further research with a larger sample is warranted to confirm that mechanisms other than improved vascular function play a role in IHG-training induced BP lowering.