The effects of ischemic preconditioning on parameters of athletic performance

The benefit of ischemic preconditioning (IPC) within the area of cardiology is well established. However, there are potential benefits of IPC that may enhance sports performance, where IPC has been suggested to offer a small but practically significant ergogenic effect to predominantly aerobic fuelled exercise performance. Since De Groot et al. (2011) initial finding that a prior-exercise repeated dose of non-lethal occlusion-reperfusion (IPC) enhanced VO2max and maximal power output, speculated to be due to up-regulation of potassium ATP channels and ATP saving, a growing body of evidence has been accumulating regarding the effects of IPC across a range of exercise performances types and modalities (Table 2.1). The purpose of this dissertation was to assess the effect of, and elucidate the mechanisms underpinning, IPC as an exercise performance ergogenic aid. To accomplish this, the impact of the intervention was assessed using key variables including exercise performance, muscle oxygenation, and VO2 and muscle kinetics, during specific exercise modalities. Insight into the potential for ergogenic effectiveness was further expanded using a range of participant abilities. In study 1 (Chapter 4) we used recreationally active participants to assess the effectiveness of remote- and local-IPC on a repeated sprint exercise (RSE) protocol, where we found a significant attenuation of fatigue decrement with IPC. In study 2 (Chapter 5) we assessed the impact of IPC on an ecologically valid RSE protocol which reflected the pre-competition warm-up and in-competition movement demands of professional, Olympic level, Rugby 7s; we did not find any impact of IPC on the athlete’s performance or any other variable assessed. In study 3 (Chapter 6) we assessed IPC’s impact on semi-professional athletes during an 80-minute simulated team sport by measuring performance and VO2 and muscle kinetics using an ergometer based intermittent sprint protocol (ISE). The findings showed that IPC reduced work done across the 80-minutes, and positively impacted muscle kinetics during the 2nd 40-minutes where there was a faster oxygen extraction. In study 4 (Chapter 7), using recreationally trained participants and the 3-minute all-out test, it was demonstrated that IPC could significantly enhance critical power (CP) by ~3%, which was supported by a trend towards an increased O2 extraction; a simulation model lent further support to the suggestion that IPC could enhance aerobic contribution to exercise performance with a significant impact of IPC on performance as the aerobic contribution to performance was increased. Finally, in study 5 (Chapter 8) IPC’s impact on time-to-exhaustion above CP was assessed using recreationally trained participants, where no performance benefit was established, but we did demonstrate slower muscle kinetics suggesting enhanced mitochondrial efficiency. Collectively, we have demonstrated that IPC can induce acute functional changes in working skeletal muscle and enhance exercise performance. We have shown positive acute effects on the peripheral microvasculature and VO2 and muscle kinetics across a range of exercise modalities where O2 extraction was increased and/or up-regulation of mitochondrial processes, along with an attenuation of fatigue decrement in RSE and ISE, and an increase in the aerobic energy contribution to aerobic and anaerobic fuelled exercise. The novel findings in this dissertation highlight important physiological mechanisms that add to the current body of scientific literature regarding IPC as a potential ergogenic aid for sports performance.