Long-term effects of high-intensity training vs moderate intensity training in heart transplant recipients: A 3-year follow-up study of the randomized-controlled HITTS study

The randomized controlled High-Intensity Interval Training in De Novo Heart Transplant Recipients in Scandinavia (HITTS) study compared 9 months of high-intensity interval training (HIT) with moderate intensity continuous training in de novo heart transplant recipients. In our 3-year follow-up study, we aimed to determine whether the effect of early initiation of HIT on peak oxygen consumption (VO 2peak ) persisted for 2 years postintervention. The study's primary end point was the change in VO 2peak (mL/kg/min). The secondary end points were muscle strength, body composition, heart rate response, health-related quality of life, daily physical activity, biomarkers, and heart function. Of 78 patients who completed the 1-year HITTS trial, 65 entered our study and 62 completed the study tests. VO 2peak increased from baseline to 1 year and leveled off thereafter. During the intervention period, the increase in VO 2peak was larger in the HIT arm; however, 2 years later, there was no significant between-group difference in VO 2peak . However, the mean change in the anaerobic threshold and extensor muscle endurance remained significantly higher in the HIT group. Early initiation of HIT after heart transplantation appears to have some sustainable long-term effects. Clinical trial registration number: NCT01796379.