Abstract
Background and Aims
Cardiovascular disease (CVD) is a major cause of morbidity and mortality in renal transplant recipients (RTRs). General CVD risk scores underestimate the risk in RTRs who also exhibit elevated inflammation and impaired immune function. Exercise has a positive impact on these unique factors and there is growing consensus on the need for formal and specific exercise guidelines in RTRs. Despite this, there is limited rigorous research in this population, particularly surrounding novel high intensity interval training (HIIT) versus moderate intensity continuous training (MICT).
Method
24 RTRs (male 17; eGFR 55 ml/min/1.73 m2 [26-90]; age 48 years [27-76]) were randomised to: HIITA (n=8; 4, 2 and 1 min intervals; 80-90% of watts at peak oxygen uptake (V̇O2 peak)), HIITB (n=8, 4 × 4 min intervals; 80-90% V̇O2 peak) or MICT (n=8, ∼35.5 min; 50-60% V̇O2 peak) for 24 supervised sessions on a stationary bike (approx. 3x/week over 8 weeks). Assessments of cardiorespiratory fitness, body composition (weight and body fat %), and physical function (sit-to-stand 60 (STS60), gait speed, and calf strength) were conducted pre and post-intervention. Data were analysed using ANCOVA and paired samples t-tests.
Results
Twenty participants completed the intervention, 8 of whom reached the required intensity (HIITA 0/6 [0%], HIITB 3/8 [38%], MICT 5/6 [83%]). Although participants completed 92% (average) of the 24 sessions, there were 105 cancelled/rearranged sessions (illness 68, other commitments 33, investigator illness 4) and an average duration of 10 weeks to complete the intervention. There were significant post-training improvements in V̇O2 peak (ml/kg/min)(See Table 1: HIITA, p=0.007; HIITB, p=0.025; MICT, p=0.012) and in peak power output (wattpeak)(HIITA, p=0.001; HIITB, p=0.005; MICT, p=0.002) for all groups. There was a significant post-training reduction in systolic and diastolic blood pressure (SBP and DBP, respectively) in MICT (p<0.001) and a significant reduction in DBP in HIITB (p<0.001). There were no significant changes in body composition. Gait speed improved in MICT (p=0043) and STS60 performance improved in HIITA (p=0.012). After controlling for baseline values, there were no significant between group differences for any post-training variables.
Conclusion
Enhanced cardiorespiratory fitness has been widely reported to correlate with a reduced risk of CVD and mortality. These early feasibility results, whilst acknowledging some baseline variations, show promising effects of both HIIT and MICT on the cardiorespiratory fitness of RTRs. Results also show promising reductions in blood pressure, a leading risk factor for CVD. Although fewer RTRs met the required intensity for the HIIT protocols than MICT, there were no serious adverse events or detrimental results reported. There were a large number of sessions cancelled due to illness; potentially attributable to immunosuppressive agents. We would recommend further large-scale trials of different HIIT protocols potentially with shorter intervals and less intense recovery periods in order to facilitate the achievement of the required intensity. Overall, these results further support the call for specific exercise guidance in this population in order to supplement current post-transplantation clinical advice.
COMPARISON OF TWO MEASURES OF BODY COMPOSITION IN RENAL TRANSPLANT RECIPIENTS