Abstract
Ischemic preconditioning (IPC) improves maximal exercise performance. However, the potential mechanism(s) underlying the beneficial effects of IPC remain unknown. The dynamics of pulmonary oxygen uptake (VO2) and muscle deoxygenation during exercise is frequently used for assessing O2 supply and extraction. Thus, this study examined the effects of IPC on systemic and local O2 dynamics during the incremental step transitions from low- to moderate- and from moderate- to severe-intensity exercise. Fifteen healthy, male subjects were instructed to perform the work-to-work cycling exercise test, which was preceded by the control (no occlusion) or IPC (3 × 5 min, bilateral leg occlusion at >300 mmHg) treatments. The work-to-work test was performed by gradually increasing the exercise intensity as follows: low intensity at 30 W for 3 min, moderate intensity at 90% of the gas exchange threshold (GET) for 4 min, and severe intensity at 70% of the difference between the GET and VO2 peak until exhaustion. During the exercise test, the breath-by-breath pulmonary VO2 and near-infrared spectroscopy-derived muscle deoxygenation were continuously recorded. Exercise endurance during severe-intensity exercise was significantly enhanced by IPC. There were no significant differences in pulmonary VO2 dynamics between treatments. In contrast, muscle deoxygenation dynamics in the step transition from low- to moderate-intensity was significantly faster in IPC than in CON (27.2 ± 2.9 vs. 19.8 ± 0.9 sec, P < 0.05). The present findings showed that IPC accelerated muscle deoxygenation dynamics in moderate-intensity exercise and enhanced severe-intensity exercise endurance during work-to-work test. The IPC-induced effects may result from mitochondrial activation in skeletal muscle, as indicated by the accelerated O2 extraction.
Highlights
Ischemic preconditioning (IPC) by brief episodes of ischemia and reperfusion in the organs, especially the heart, provides protection from tissue damage such as myocardial injury (Murry et al 1986)
Results of the dynamics of pulmonary VO2 during the work-to-work cycling exercise test are shown in Table 1 and Figure 2
Previous studies have reported that IPC enhances maximal exercise performance, such as VO2 peak and maximal workload
Summary
Ischemic preconditioning (IPC) by brief episodes of ischemia and reperfusion in the organs, especially the heart, provides protection from tissue damage such as myocardial injury (Murry et al 1986). The dynamics of pulmonary oxygen uptake (VO2) and muscle deoxygenation during exercise are frequently used for assessing O2 supply and extraction (DeLorey et al 2003; Wilkerson et al 2004; Bailey et al 2010). Those systemic and local O2 dynamics may be useful for understanding the beneficial effects of IPC on exercise performance. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society
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