High‐Intensity Interval Training Improves Peak Oxygen Uptake and Muscular Exercise Capacity in Heart Transplant Recipients

Heart transplant (HTx) recipients usually have reduced exercise capacity with reported VO_2peak 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 VO_2peak. Secondarily, we wanted to evaluate central and peripheral mechanisms behind a potential VO_2peak 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 VO_2peak 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 VO_2peak 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 VO_2peak, 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.