Augmented muscle glycogen utilization following a single session of sprint training in hypoxia

Purpose This study determined the effect of a single session of sprint interval training in hypoxia on muscle glycogen content among athletes. Methods Ten male college track and field sprinters (mean +/- standard error of the mean: age, 21.1 +/- 0.2 years; height, 177 +/- 2 cm; body weight, 67 +/- 2 kg) performed two exercise trials under either hypoxia [HYPO; fraction of inspired oxygen (FiO2), 14.5%] or normoxia (NOR: FiO2, 20.9%). The exercise consisted of 3 x 30 s maximal cycle sprints with 8-min rest periods between sets. Before and immediately after the exercise, the muscle glycogen content was measured using carbon magnetic resonance spectroscopy in vastus lateralis and vastus intermedius muscles. Moreover, power output, blood lactate concentrations, metabolic responses (respiratory oxygen uptake and carbon dioxide output), and muscle oxygenation were evaluated. Results Exercise significantly decreased muscle glycogen content in both trials (interaction, P = 0.03; main effect for time, P < 0.01). Relative changes in muscle glycogen content following exercise were significantly higher in the HYPO trial (- 43.5 +/- 0.4%) than in the NOR trial (- 34.0 +/- 0.3%; P < 0.01). The mean power output did not significantly differ between the two trials (P = 0.80). The blood lactate concentration after exercise was not significantly different between trials (P = 0.31). Conclusion A single session of sprint interval training (3 x 30 s sprints) in hypoxia caused a greater decrease in muscle glycogen content compared with the same exercise under normoxia without interfering with the power output.