Isometric handgrip training and arterial blood pressure: Effects and mechanisms

The purpose of this thesis was threefold: (1) to replicate previous isometric handgrip (IHG) training-induced resting arterial blood pressure (ABP) reductions in persons with hypertension, (2) to investigate improved endothelial-dependent flow-mediated dilation (FMD) as a mechanism underlying ABP modification following IHG training in persons with and without hypertension, and (3) to assess the acute hemodynamic responses to IHG exercise in persons medicated for hypertension and observe the effects of training. Previous findings that IHG training lowered resting systolic ABP (SBP) in persons medicated for hypertension were reproduced in the first study. Findings suggested that improved systemic endothelial-dependent vasodilation may be a mechanism responsible for the SBP reductions however this was refuted in the second study. Improved endothelial-dependent vasodilation did not play a role in reducing SBP in persons with normal ABP either, as indicated in the third study. The fourth study confirmed that training-induced improvements in FMD were not due to changes in endothelial-independent vasodilation, and that acute IHG exercise transiently impaired FMD in persons medicated for hypertension. The fifth study showed that forearm blood flow and vascular conductance were altered throughout a bout of IHG exercise in medicated hypertensives, yet were unchanged with training. It was also concluded that not all medicated hypertensives experience ABP reductions in response to IHG training. Finally, the sixth study demonstrated that reproducible estimations of FMD can be made in persons medicated for hypertension.;The studies in this thesis were the first to examine the effects of IHG training on: (1) ABP and endothelial-dependent FMD in medicated hypertensives, and in persons with normal ABP, and (2) the acute hemodynamic and vascular responses to IHG exercise in persons medicated for hypertension. These investigations add to the body of evidence that IHG training can lower ABP in persons with and without hypertension, yet the mechanisms remain elusive.