Effects of acute and chronic low-volume high-intensity interval exercise on cardiovascular health in patients with coronary artery disease

Abstract

The merits of low-volume high-intensity interval exercise (HIT) have been established in healthy populations; however, no studies have examined this exercise prescription in patients with coronary artery disease (CAD). The present thesis examined the acute and chronic effects of HIT in patients with CAD. The first study demonstrated transient improvements in brachial artery endothelial-dependent function, which was assessed using flow-mediated dilation (FMD) 60 min following a single bout of either HIT or moderate-intensity endurance exercise (END) in habitually active patients. The second study demonstrated no effects of training status on the acute endothelial responses to exercise; following 12-weeks of either HIT or END training. However, there was a significant reduction in endothelial-independent function immediately postexercise, at both pre- and post-training, which requires further examination. The third study demonstrated comparable increases in fitness and resting FMD following 12-weeks of END and HIT, lending support to the notion that favourable adaptations are obtainable with a smaller volume of exercise. Finally, the fourth study demonstrated no change in heart rate recovery following 12-weeks of END and HIT. However, pre-training heart rate recovery values reported by our sample were in a low risk range, which suggests training induced improvements may only be achievable in populations with attenuated pre-training values. The results of this thesis provide preliminary evidence that supports the use of HIT in patients with CAD. The findings of favourable transient and chronic improvements following HIT are notable, especially given that the HIT protocol involves less time and work than END, which was modelled after the current exercise prescription in cardiac rehabilitation. Further investigations are necessary, including the assessment of additional physiological indices; the feasibility and adherence to HIT; the inclusion of CAD populations with comorbidities, including heart failure and diabetes; as well as other forms of HIT training, including HIT combined with resistance training.