Abstract and Introduction
Purpose: Isocaloric interval exercise training programs have been shown to elicit improvements in numerous physiological indices in patients with CAD. Low-volume high-intensity interval exercise training (HIT) is effective in healthy populations; however, its effectiveness in cardiac rehabilitation has not been established. This study compared the effects of 12-wk of HIT and higher-volume moderate-intensity endurance exercise (END) on brachial artery flow-mediated dilation (FMD) and cardiorespiratory fitness (V·O2peak) in patients with CAD.
Methods: Twenty-two patients with documented CAD were randomized into HIT (n = 11) or END (n = 11) based on pretraining FMD. Both groups attended two supervised sessions per week for 12 wk. END performed 30–50 min of continuous cycling at 58% peak power output (PPO), whereas HIT performed ten 1-min intervals at 89% PPO separated by 1-min intervals at 10% PPO per session.
Results: Relative FMD was increased posttraining (END, 4.4% ± 2.6% vs 5.9% ± 3.6%; HIT, 4.6% ± 3.6% vs 6.1% ± 3.4%, P ≤ 0.001 pre- vs posttraining) with no differences between groups. A training effect was also observed for relative V·O2peak (END, 18.7 ± 5.7 vs 22.3 ± 6.1 mL·kg−1·min−1; HIT, 19.8 ± 3.7 vs 24.5 ± 4.5 mL·kg−1·min−1, P < 0.001 for pre- vs posttraining), with no group differences.
Conclusions: Low-volume HIT provides an alternative to the current, more time-intensive prescription for cardiac rehabilitation. HIT elicited similar improvements in fitness and FMD as END, despite differences in exercise duration and intensity.
Interval training has gained considerable attention as a suitable exercise program for patients with cardiovascular diseases including CAD and heart failure.[2,5,10] Investigations using various types of high-intensity interval protocols in CAD patients demonstrate training-induced improvements in numerous physiological indices.[19–21,27,35,36] In addition, when compared with the current exercise program used in cardiac rehabilitation of high-volume moderate-intensity endurance exercise (END), interval exercise has been shown to elicit superior improvements in indices of cardiorespiratory fitness[27,35,36] and endothelial function. These previous investigations, however, used isocaloric protocols, where the energy expenditure of the interval bout was matched to that of the END bout. No studies have examined the effectiveness of an interval protocol not matched to END for energy expenditure in patients with CAD.
Low-volume interval protocols, which are not matched for energy expenditure, are time-efficient strategies that have been shown to be effective in healthy populations.[13,26] Given that "lack of time" is one of the commonly cited barriers to exercise adherence in cardiac rehabilitation, a low-volume, high-intensity interval protocol may be a superior treatment strategy in terms of adherence if the resultant physiological benefits are comparable. The purpose of this study was to compare the effects of 12 wk of END and low-volume high-intensity interval exercise training (HIT) on endothelial function and cardiorespiratory fitness in patients with CAD. These indices were chosen for examination because they are related to future risk of mortality.[17,22] On the basis of evidence from investigations in healthy populations, it was hypothesized that the effects of HIT would be comparable with those found with END for the indices examined.
Med Sci Sports Exerc. 2013;45(8):1436-1442. © 2013 American College of Sports Medicine