Ischemic preconditioning of the muscle improves maximal exercise performance but not maximal oxygen uptake in humans

Abstract

Brief episodes of nonlethal ischemia, commonly known as “ischemic preconditioning” (IP), are protective against cell injury induced by infarction. Moreover, muscle IP has been found capable of improving exercise performance. The aim of the study was the comparison of standard exercise performances carried out in normal conditions with those carried out following IP, achieved by brief muscle ischemia at rest (RIP) and after exercise (EIP). Seventeen physically active, healthy male subjects performed three incremental, randomly assigned maximal exercise tests on a cycle ergometer up to exhaustion. One was the reference (REF) test, whereas the others were performed after the RIP and EIP sessions. Total exercise time (TET), total work (TW), and maximal power output (Wmax), oxygen uptake (VO2max), and pulmonary ventilation (VEmax) were assessed. Furthermore, impedance cardiography was used to measure maximal heart rate (HRmax), stroke volume (SVmax), and cardiac output (COmax). A subgroup of volunteers ( n = 10) performed all-out tests to assess their anaerobic capacity. We found that both RIP and EIP protocols increased in a similar fashion TET, TW, Wmax, VEmax, and HRmax with respect to the REF test. In particular, Wmax increased by ∼4% in both preconditioning procedures. However, preconditioning sessions failed to increase traditionally measured variables such as VO2max, SVmax, COmax, and anaerobic capacity. It was concluded that muscle IP improves performance without any difference between RIP and EIP procedures. The mechanism of this effect could be related to changes in fatigue perception.