Home-based exercise and PHysical activity maintenance interventiOn after livEr traNsplantation: Impact of eXercise intensity (PHOENIX-Liver).

Liver transplant recipients experience comorbidities, including impaired physical fitness, which could be managed by exercise and physical activity interventions. This study aims to evaluate the feasibility, clinical effectiveness and cost-effectiveness of a 6-month exercise intervention, followed by a 15-month tailored physical activity maintenance intervention, in de novo liver transplant recipients. This single-centre, randomised, controlled, single-blinded trial will recruit 147 adult liver transplant recipients at 3-5 months post-transplant. Participants will be randomised into (1) 6 months of enhanced usual care, not followed by a physical activity intervention (control (CON) group, n=49), (2) 6 months of moderate-intensity exercise training, followed by a physical activity intervention (moderate-intensity training (MIT) group; n=49) or (3) consecutively 3 months of moderate-intensity exercise training, 3 months of high-intensity interval training and a physical activity intervention (moderate and high-intensity training (MHIT) group; n=49). Exercise training will consist of home-based stationary bicycling and muscle-strengthening exercises, partially supervised by participants' local physiotherapists. The physical activity intervention includes an array of behaviour change techniques. Primary hypothesis: after the exercise intervention, peak oxygen uptake (V̇O₂peak) will be higher in MHIT versus CON (α-level 0.05). Secondary hypotheses: after the exercise intervention, V̇O₂peak will be higher in MIT versus CON and MHIT versus MIT (α-level 0.025). Secondary outcomes, assessed up to 2 years post-transplant, include physical fitness, cardiovascular and graft health, quality of life, physical activity and implementation outcomes. Trial registration number NCT06302205.