Effect of high-intensity interval training in young heart transplant recipients: results from two randomized controlled trials
Question
Do young heart transplant recipients show greater improvements in aerobic capacity and strength after HIT than with moderate-intensity training or no structured exercise?
Summary
This hypothesis-generating analysis combined young adult heart transplant recipients from two randomized trials. Supervised treadmill HIT was associated with larger gains in peak oxygen consumption and maximal strength than moderate training or usual activity, but the sample was very small and highly clinical.
Methodology
- Young adult heart transplant recipients from two RCTs.
- 28 participants.
- Treadmill.
- Work intervals: Continuous for MICT.
- Intensity: 85-95% peak effort.
- Not fully restated in this substudy.
- TEX: 3 sessions/week during three 8-week periods; HITTS not fully restated.
- 9 months in HITTS; 1 year in TEX.
- Hypothesis-generating young-subgroup analysis from two randomized controlled trials.
- Peak oxygen consumption, Maximal muscle strength, Muscular exercise capacity, and Chronotropic response were tracked.
Outcomes
Peak oxygen consumption in HITTS young recipients
HIT improved peak oxygen consumption more than MICT.
Difference 4.7 ml/kg/min, 95% CI 0.4 to 9.1, p=0.034.
Peak oxygen consumption in TEX young recipients
HIT improved peak oxygen consumption more than no specific intervention.
Difference 7.0 ml/kg/min, 95% CI 2.6 to 11.3, p=0.005.
Maximal strength
Young HIT participants had greater maximal strength gains than comparators in both parent-trial subsets.
HITTS difference 45 Nm p=0.004; TEX difference 41 Nm p=0.031.
Muscular exercise capacity
Muscular exercise capacity differences were not significant.
Insights
- Clinical high-risk HIIT evidence should be used to define guardrails, not consumer programming.
- Heart transplant status should route users to clinician-led exercise advice.
- Individualized intensity and supervision are central in this population.
Limitations
- Very small young subgroup
- Combines two different parent RCTs
- Not pediatric despite discussion of young recipients
- Adherence and safety details not separately reported for the subgroup
- Clinical population limits generalizability
Safety
- No young-subgroup adverse-event counts were reported.
- Exercise was professionally supervised or closely monitored in a clinical transplant context.