• Aerobic exercise;
  • chronotropic response;
  • heart transplantation;
  • maximum oxygen uptake;
  • muscle strength;
  • VO2peak

Heart transplant (HTx) recipients usually have reduced exercise capacity with reported VO2peak levels of 50–70% predicted value. Our hypothesis was that high-intensity interval training (HIIT) is an applicable and safe form of exercise in HTx recipients and that it would markedly improve VO2peak.

Secondarily, we wanted to evaluate central and peripheral mechanisms behind a potential VO2peak increase. Forty-eight clinically stable HTx recipients >18 years old and 1–8 years after HTx underwent maximal exercise testing on a treadmill and were randomized to either exercise group (a 1-year HIIT-program) or control group (usual care). The mean ± SD age was 51 ± 16 years, 71% were male and time from HTx was 4.1 ± 2.2 years. The mean VO2peak difference between groups at follow-up was 3.6 [2.0, 5.2] mL/kg/min (p < 0.001). The exercise group had 89.0 ± 17.5% of predicted VO2peak versus 82.5 ± 20.0 in the control group (p < 0.001). There were no changes in cardiac function measured by echocardiography. We have demonstrated that a long-term, partly supervised and community-based HIIT-program is an applicable, effective and safe way to improve VO2peak, muscular exercise capacity and general health in HTx recipients. The results indicate that HIIT should be more frequently used among stable HTx recipients in the future.