Exercise-Based Prehabilitation for Kidney Transplant Candidates: The FRAILMar Randomized Controlled Trial.

RATIONALE & OBJECTIVE Kidney transplantation (KT) is the preferred treatment for kidney failure but carries significant post-transplant risks, particularly for frail patients. This study evaluated the effects of an exercise-based prehabilitation program on exercise capacity, muscle function, and muscle size among KT candidates. STUDY DESIGN Analysis of functional outcomes within the FRAILMar study, a randomized controlled trial. SETTING & PARTICIPANTS 121 KT candidates on the KT waiting list. INTERVENTION The intervention group participated in a prehabilitation program comprising 24 exercise sessions (1 hour, 3 times per week for 8 weeks), the control group received standard care. Randomization was stratified by frailty status. OUTCOMES The primary outcome was exercise capacity assessed by maximal workload during a cardiopulmonary exercise test. Secondary outcomes included peripheral muscle function, respiratory muscle function, muscle size, and changes in frailty status. RESULTS The mean age of the 121 individuals who were randomized was 63.4 years, 76% were men, and 40% were frail (Fried phenotype ≥ 2). 106 patients completed the prehabilitation program and, among them, compared to standard care, prehabilitation significantly improved exercise capacity (+12.8 watts; [95% CI: 3.4 to 22.2]; p=0.008), handgrip strength (+1.8 kg; [95% CI: 0.7 to 2.8]; p<0.001), and rectus femoris thickness (+1.2 mm; [95% CI: 0.3 to 2.0]; p=0.007). Frail patients showed significant improvements across most measures, demonstrating potential benefits for this subgroup. LIMITATIONS This analysis was limited by a short follow-up period and the risk of type I error due to multiple comparisons, even though outcomes were pre-specified. CONCLUSIONS An 8-week exercise-based prehabilitation program may improve KT candidates' exercise capacity, muscle function, and muscle size, effects also observed among frail patients. These findings may inform future research in this area and the evaluation of the value of standardized prehabilitation protocols.