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 posttransplant 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.

OUTCOME: 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). Of these patients, 106 completed the prehabilitation program; among them, compared with standard care, prehabilitation significantly improved exercise capacity (+12.8 watts [95% CI, 3.4-22.2], P = 0.008), handgrip strength (+1.8 kg [95% CI, 0.7-2.8], P < 0.001), and rectus femoris thickness (+1.2 mm; [95% CI, 0.3-2.0], 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 prespecified.

CONCLUSIONS: An 8-week exercise-based prehabilitation program may improve KT candidates' exercise capacity, muscle function, and muscle size, and these effects also were observed among frail patients. These findings may inform future research in this area and the evaluation of the value of standardized prehabilitation protocols.

FUNDING: Grant from government (Instituto de Salud Carlos III).

TRIAL REGISTRATION: Registered at Clinicaltrials.gov with study number NCT04701398.

PLAIN-LANGUAGE SUMMARY: Kidney transplantation is the preferred treatment for kidney failure, but recovery can be challenging, especially for frail patients with low physical activity and muscle strength. This study examined whether an exercise-based program before surgery can help improve fitness and muscle function in transplant candidates. Patients were randomly assigned to 1 of 2 groups: one followed an exercise program and the other received standard care. The exercise group participated in guided sessions for 8 weeks. The study found that those who exercised had better fitness, stronger grip strength, and larger muscle mass than those who did not. These findings suggest that exercise before transplantation might be clinically beneficial, though further research is needed to confirm these findings.