Abstract
This study was designed to (1) investigate the effects of acute short‐duration intermittent hypoxia on muscle mRNA and microRNA expression levels; and (2) clarify the mechanisms by which short‐duration intermittent hypoxia improves endurance capacity. Experiment‐1: Male mice were subjected to either acute 1‐h hypoxia (12% O2), acute short‐duration intermittent hypoxia (12% O2 for 15 min, room air for 10 min, 4 times, Int‐Hypo), or acute endurance exercise (Ex). The expression of vascular endothelial growth factor‐A mRNA was significantly greater than the control at 0 h post Ex and 6 h post Int‐Hypo in the deep red region of the gastrocnemius muscle. miR‐16 expression levels were significantly lower at 6 and 10 h post Int‐Hypo. Peroxisome proliferator‐activated receptor gamma coactivator 1‐alpha (PGC‐1α) mRNA levels were significantly greater than the control at 3 h post Ex and 6 h post Int‐Hypo. miR‐23a expression levels were lower than the control at 6–24 h post Int‐Hypo. Experiment‐2: Mice were subjected to normoxic exercise training with or without intermittent hypoxia for 3 weeks. Increases in maximal exercise capacity were significantly greater by training with short‐duration intermittent hypoxia (IntTr) than without hypoxia. Both 3‐Hydroxyacyl‐CoA‐dehydrogenase and total carnitine palmitoyl transferase activities were significantly enhanced in IntTr. Peroxisome proliferator‐activated receptor delta and PGC‐1α mRNA levels were both significantly greater in IntTr than in the sedentary controls. These results suggest that exercise training under normoxic conditions with exposure to short‐duration intermittent hypoxia represents a beneficial strategy for increasing endurance performance by enhancing fatty acid metabolism in skeletal muscle.
Highlights
Exercise training at high altitude was developed in the early 1990s in order to enhance exercise performance
The expression of VEGF-A mRNA in Gr was significantly greater than the control at 0 h post Ex and 6 h post Int-Hypo
proliferator-activated receptor gamma coactivator 1-alpha (PGC-1a) mRNA levels in Gr were significantly greater than the control at 3 and 6 h post Ex and 6 h post Int-Hypo
Summary
Exercise training at high altitude was developed in the early 1990s in order to enhance exercise performance. Numerous combinations of the duration of hypoxic exposure, intensity of exercise, and period of training have been experimentally investigated, an essential strategy to improve athletic performance, especially endurance capacity at sea level, has not yet been clearly identified (Terrados et al.1990; Levine et al 1992; Vogt et al 2001; Julian et al 2004; Katayama et al 2004; Bakkman et al 2007; Vogt and Hoppeler 2010; De Paula and Niebauer 2012). Intermittent hypoxic training comprises several hours or overnight hypoxic exposure at rest per day with exercise training under normoxia, and has been proposed as a useful strategy that does not restrict the daily training regimens of athletes (Julian et al 2004; Katayama et al 2004). The effects of hypoxic exposure, comprising a 3–6-min hypoxia/normoxia cycle,
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