Abstract 1721: Double Blind Randomized Controlled Crossover Studies of the Effects of Remote Preconditioning on the Exercise Performance of Elite Swimmers: Evidence for a Persistent Preconditioned State
Background: Remote ischemic preconditioning (RIPC), induced by transient limb ischemia, releases a dialysable, circulating protective factor that reduces ischemia-reperfusion (IR) injury. Maximal performance in elite swimmers is limited by exercise induced arterial hypoxemia and may therefore represent a form of IR stress.
Methods: 11 national level swimmers, 13 to 18 years of age, were randomised to real (4 cycles of 5 minutes arm ischemia) or sham preconditioning with cross-over. In study 1, subjects performed two incremental submaximal swimming tests with measurement of swimming velocity, blood lactate, and heart rate at each of 7 stages. For study 2, subjects (n = 8) performed two maximal competitive swims of 100m. All observers were blinded to the treatment protocol. Study 3: To determine the presence of circulating protective factors, blood samples taken before and after RIPC (n = 5) were dialysed and used to perfuse mouse hearts (n = 10) in Langendorff preparation (30 minutes of global ischemia/1 hour reperfusion). TTC staining was used to measure infarct size as a % of area at risk. Results were compared to dialysate obtained from non athletic controls pre and post RIPC.
Results: RIPC had no effect on incremental submaximal exercise performance in study 1. In study 2, RIPC led to a significant improvement in swim time (64.9 ± 3.9 (sham) vs. 64.0 ± 3.7s, p < 0.05), but this was not at the expense of increased lactate production (p = 0.46). Using linear regression models adjusted for repeated measures and order of treatment assignment, there was a 0.93 ± 0.35s reduction in competitive swim time (p = 0.009) with RIPC. In study 3, infarct size was unaffected by dialysate from swimmers (pre RIPC 27 + 9 vs. post RIPC 23 + 10%, p = ns), but infarct size was significantly (p + 0.02) lower than control dialysate pre RIPC (51 + 21%) and no different compared with control dialysate post RIPC (27 + 4%, p = ns).
Conclusion: Elite swimmers have evidence of a pre-existing circulating protective factor that provides cross-species protection against IR injury. Additional RIPC does not affect submaximal testing but significantly improves maximal performance.