BACKGROUND: Growing evidence in long-term treatment of heart transplant (HTx) recipients indicates effects of high-intensity interval training (HIIT) on several parameters, including oxygen uptake, vascular function and psychological distress. In this study we compare the effect of HIIT vs continued moderate training (CON) on vascular function, biomarkers and health-related quality of life (HRQoL) in HTx recipients.

METHODS: A randomized, controlled crossover trial of stable HTx recipients >12 months after transplantation was done on patients with 12 weeks of HIIT or 12 weeks of CON, followed by a 5-month washout and crossover. Outcomes included endothelial function, arterial stiffness, biomarkers, HRQoL and markers of anxiety and depression.

RESULTS: Sixteen HTx recipients (mean age 52 years, 75% male) completed the study. HIIT increased VO2peak more than CON (between-group difference, p < 0.001). The physical component score of the 36-item Short Form (SF-36) was increased significantly in HIIT patients (p = 0.02) and borderline increased in CON patients (p = 0.07), whereas there was no significant effect of exercise on the mental component. Depression score decreased significantly in HIIT patients (p = 0.04) with no change in CON patients (p = 0.75), whereas anxiety score decreased significantly in both HIIT (p < 0.01) and CON (p < 0.05) patients. There were no between-group differences in any of the measures (all p > 0.05). Arterial stiffness and biomarkers were not changed, nor did endothelial function change after HIIT (p = 0.08) or CON (p = 0.68).

CONCLUSIONS: HIIT and CON are both well tolerated and induce similar improvements in physical components of HRQoL and in markers of anxiety. Effects of either training modality on vascular function and biomarkers could not be confirmed.