Exercise strategies to improve vascular health and exercise tolerance. Implications for rehabilitation.

Exercise tolerance strongly predicts morbidity and mortality, and correlates with health-related quality of life. The mechanisms underpinning exercise intolerance were investigated in Chapter 3. Peripheral vascular dysfunction occurs when there is an imbalance between endothelial damage and endogenous repair mechanisms, and can contribute to exercise intolerance. Vascular dysfunction typically precedes a diagnosis of cardiovascular disease and is related to disease severity in cardiovascular disease patients (e.g. chronic heart failure; CHF). Exercise training increases vascular function and exercise tolerance in health and CHF, with high-intensity interval training (HIIT) often inducing greater improvements than continuous ‘control’ protocols. However, it is unknown whether the effectiveness of HIIT can be improved.

Therefore, Chapter 4 investigated the acute and chronic effect of HIIT with and without blood flow restriction (BFR) on vascular endogenous repair capacity, ramp-incremental exercise tolerance and V̇O2peak in CHF. Four weeks of HIIT did not induce acute or chronic vascular adaptations; however, chronic HIIT increased ramp-incremental exercise tolerance and V̇O2peak. BFR did not increase training efficacy.

Chapter 5 determined whether 6 weeks of HIIT at a high work rate with short work:recovery bouts (intended to maximise the volume of shear rate accumulated) increased vascular endogenous repair capacity, endothelial function, exercise tolerance and V̇O2peak more than intensity-matched continuous exercise training in healthy adults. No acute or chronic vascular adaptations were seen with HIIT. This type of HIIT increased post-training exercise tolerance and V̇O2peak but was no more effective than intensity-matched constant work rate exercise training.

Overall, increases in exercise tolerance and V̇O2peak in both training studies were not underpinned by improvements in peripheral vascular endothelial function and/or increases in vascular endogenous repair capacity. Therefore, despite the efficacy of training to increase exercise tolerance, further work is needed to develop exercise strategies that effectively and specifically target improvements in vascular endogenous repair capacity and peripheral vascular function.