The role of haemodynamic stimulus in isometric exercise training: implications for cardiovascular adaptations

The purpose of this thesis was to explore the role of exercise induced blood flow haemodynamics in thcardiovascular adaptations associated with isometric exercise
training, with focus on resting blood pressure adjustment in normotensive participants. Using a cross-sectional study, it was identified that significant relationships were
present between (i) blood flow, (ii) shear stress, and (iii) shear pattern responses(measured in the femoral artery), during and immediately following isometric bilateral
leg extension exercise of increasing intensity. Based on these findings, it was feasible to suggest that the haemodynamic response to high intensities of acute isometric exercise might provide a physiological challenge to the cardiovascular system, that upon repeated exposure via isometric exercise training, may induce cardiovascular adaptation and resting blood pressure reductions. Subsequent to this, a randomised controlled trial established that performing isometric exercise training to a ‘high haemodynamic stimulus’ did not induce significantly greater adaptation in resting blood pressure than when performing isometric exercise training to a ‘low haemodynamic stimulus’ or control. When the training group (high and low combined) were compared to the control, significant reductions in resting blood pressure were observed. Furthermore, non-invasive cardiovascular variables that were considered as possible physiological mechanisms for resting blood pressure adaptation following isometric exercise training did not correlate with within group resting blood pressure changes.

Whilst these findings suggest that a haemodynamic challenge may not be the primary stimulus responsible for inducing resting blood pressure adaptation following isometric exercise training, these results do demonstrate the effectiveness of isometric exercise training for potential health gains via reductions in resting blood pressure in normotensives. Importantly, these findings have progressed the current understanding surrounding isometric exercise training induced resting blood pressure reductions and will allow future research to narrow their focus upon other physiological variables that may be the stimuli for blood pressure adaptation.