Author(s): MATSUDO, H., GOTO, K., Institution: RITSUMEIKAN UNIVERSITY, Country: JAPAN, Abstract-ID: 980

INTRODUCTION:
Sleep is an indispensable activity to maintain health. Insufficient sleep duration or decreased sleep quality has been associated with an increased risk of injuries and augmented inflammation (Milewski et al., 2014). Previous research has revealed that sleep quality tends to be decreased during sleep in hypoxia compared with sleep in normoxia (Heinzer et al., 2016). However, typical type of “living low, training high” procedure involves exercise in hypoxia (< 2h) and sleep in normoxia. Therefore, further investigations need to clarify how high-intensity exercise under hypoxia affects sleep quality. The present study was designed to clarify the effect of strenuous exercise session under hypoxia on sleep-related physiological responses in young
METHODS:
Ten healthy active males(20.3±0.4year, 172.7±1.8cm, 65.29±2.1kg) were recruited. They performed 3 conditions on different days, (1)exercise in hypoxia (Hypoxia; FiO2:14.5%), (2) exercise in normoxia (Normoxia; FiO2:20.9%), and (3)rest (Rest; without exercise). The exercise consisted of 30min pedaling exercise (the load was set as 3% of body weight) followed by repeated sprint exercise [(6s maximal pedaling with 30s rest periods between sprints×6session×2set), the load was set as 7.5% body weight]. During exercise session (16:30~17:30) HR, SpO2, and RPE were evaluated. During subsequent sleep (24:00~7:00) sleep architecture (EEG), skin temperature, and autonomic nerve activity(HF, LF/HF) were further evaluated.
RESULTS:
During exercise, SpO2 was significantly lower in Hypoxia (85±0.3%) than in Normoxia (97±0.1%) and Rest (98±0.1%, P<0.05). HR was significantly higher in Hypoxia (144±1 bpm) and Normoxia (138±2 bpm) than in Rest (66±0.4 bpm, P<0.05), with no significant differences between Hypoxia and Normoxia. During 7 hours of sleep, autonomic nerve activity (HF, LF/HF) did not differ significantly among three conditions. Moreover, total sleep time, sleep efficiency, and sleep latency did not differ significantly among three conditions. However, sleep latency of slow wave sleep (SWS; stage 3) was significantly longer in Hypoxia (18.2±11.7 min) than in Normoxia (9.0±0.8 min) and Rest (7.2±1 min, P<0.05).
CONCLUSION:
Although strenuous exercise session under hypoxia did not affect sleep efficiency, it significantly delayed the onset of the SWS, which may be potentially negative for sleep quality.

REFERENCE:
・Milewski, M. D., Skaggs, D. L., Bishop, G. A., Pace, J. L., Ibrahim, D. A., Wren, T. A., & Barzdukas, A. (2014). Chronic lack of sleep is associated with increased sports injuries in adolescent athletes. Journal of Pediatric Orthopedics, 34(2), 129–133.

・Heinzer, R., Saugy, J. J., Rupp, T., Tobback, N., Faiss, R., Bourdillon, N., Rubio, J. H., & Millet, G. P. (2016). Comparison of Sleep Disorders between Real and Simulated 3,450-m Altitude. Sleep, 39(8), 1517–1523.