Heart transplantation is the long-term treatment for children and adults with advanced heart failure. Post-transplant outcomes have improved over time, such that 50% of pediatric heart transplant recipients (HTR) remain alive with a need for re-transplantation 17-years following the initial transplant. With improved short- and medium-term outcomes, focus has shifted towards optimizing long-term survival and reducing transplant-associated morbidities. This includes strategies aimed at optimizing cardiorespiratory fitness and physical activity levels. Pediatric and adult HTRs have reduced exercise capacity compared with the general population. Previous groups have shown gradual improvements in heart rate response to exercise and exercise capacity in pediatric HTRs. However, after an initial improvement, exercise capacity appears to plateau, or even decline in pediatric HTRs, and remains sub-optimal compared with the general population. Most exercise interventions in HTRs to date have focused on moderate-intensity continuous exercise (MICE), with some resistance components incorporated. More recently, high-intensity interval training (HIIT), consisting of short, intense bursts of exercise with rest periods, has been explored in the adult HTR population, with findings to date suggesting that it may yield greater improvements in cardiorespiratory fitness compared with MICE. Exercise interventions, particularly HIIT interventions, have consistently shown clinically important improvements in exercise capacity in adult HTRs that are linked with improved long-term post-transplant outcomes and well-being. Unfortunately, trials of exercise interventions in pediatric HTRs remain lacking. This study team is proposing an assessment of the feasibility of a home-based HIIT exercise program using a novel telemedicine-enable video game linked customizable cycle ergometer (MedBIKE™).