Effect of High-Intensity Interval Training on Aerobic Capacity and Heart Rate Control of Heart Transplant Recipients: a Systematic Review with Meta-Analysis

INTRODUCTION: Heart transplantation (HTx) is the gold standard procedure for selected individuals with refractory heart failure. High-intensity interval training (HIIT) is safe and allows patients to exercise in high intensity for longer time when compared to moderate-intensity continuous training (MICT). The primary aim of this study was to perform a systematic review and meta-analysis about the effect of HIIT compared to MICT on exercise capacity, peak heart rate, and heart rate reserve in HTx recipients. Secondarily, we pooled data comparing MICT and no exercise training in these patients. METHODS: This systematic review followed the standardization of the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement and the Cochrane Collaboration Handbook. We presented the treatment effects of HIIT on the outcomes of interest as mean difference (MD) and 95% confidence interval (CI). Meta-analysis was performed using the random-effects, generic inverse variance method. RESULTS: HIIT improved peak oxygen consumption (peakVO2) (MD = 2.1; 95% CI 1.1, 3.1; P<0.0001), peak heart rate (MD = 3.4; 95% CI 0.8, 5.9; P=0.009), and heart rate reserve (MD = 4.8; 95% CI -0.05, 9.6; P=0.05) compared to MICT. Improvements on peakVO(2) (MD = 3.5; 95% CI 2.3, 4.7; P<0.00001) and peak heart rate (MD = 5.6; 95% CI 1.6, 9.6; P=0.006) were found comparing HIIT and no exercise training. CONCLUSION: Current available evidence suggests that HIIT leads to improvements on peakVO(2), peak heart rate, and heart rate reserve compared to MICT in HTx recipients. However, the superiority of HIIT should be tested in isocaloric protocols.