Ischemic preconditioning improves maximal performance in humans

Abstract

Repeated episodes of ischemia followed by reperfusion, commonly referred to as ischemic preconditioning (IPC), represent an endogenous protective mechanism that delays cell injury. IPC also increases blood flow and improves endothelial function. We hypothesize that IPC will improve physical exercise performance and maximal oxygen consumption. The purpose of the study was to examine the effect of ischemic preconditioning in leg skeletal muscles on cycling exercise performance in healthy individuals. Fifteen healthy, well-trained subjects performed two incremental maximal exercise tests on a bicycle ergometer. Power output, oxygen consumption, ventilation, respiratory quotient, and heart rate were measured continuously. Blood pressure and blood lactate were measured before and after the test. One exercise test was performed after the application of ischemic preconditioning, using a protocol of three series of 5-min ischemia at both legs with resting periods of 5 min in between. The other maximal cycling test served as a control. Tests were conducted in counterbalanced order, at least 1 week apart, at the same time of the day. The repeated ischemic periods significantly increased maximal oxygen consumption from 56.8 to 58.4 ml/min per kg (P = 0.003). Maximal power output increased significantly from 366 to 372 W (P = 0.05). Ischemic preconditioning had no effect on ventilation, respiratory quotient, maximal heart rate, blood pressure or on blood lactate. Repeated short-term leg ischemia prior to an incremental bicycle exercise test improves maximal oxygen consumption by 3% and power output by 1.6%. This protocol, which is suggested to mimic the effects of ischemic preconditioning, may have important implications for exercise performance.

Fig. 1

Protocol of the study. IPC ischemic preconditioning, VO ₂ max test incremental bicycle exercise test with measurement of maximal oxygen consumption, LL left leg, RL right leg. Gray square boxes represent 5-min arterial occlusion, alternated by 5 min without arterial occlusion (white boxes). During the maximal exercise test the gray boxes represent power output (W)

Fig. 2

Individual and mean maximal oxygen consumption (VO₂max in ml/min per kg) during the maximal exercise test without (black square) and with ischemic preconditioning (IPC, open square). N = 15. Error bars represent SE. *P < 0.003