Author(s): NATSUI, T., TSUNODA, K., HOSHI, R., GOTO, K., Institution: RITSUMEIKAN UNIVERSITY, Country: JAPAN, Abstract-ID: 819

INTRODUCTION:
Athletes are often required to exercise in a hot environment at night during summer. However, high-intensity exercise at night caused sustained elevation of body temperature and sympathetic nervous activation, leading to reduced sleep quality (Oda and Shirakawa 2014). Exercise in a hot environment further elevates core body temperature (Périard et al., 2021), which may impair sleep quality compared to the exercise in a thermoneutral environment. However, few studies have examined the effects of nighttime endurance exercise in a hot environment on sleep. Therefore, the present study aimed to investigate whether nighttime endurance exercise in a hot environment aggravates sleep quality.
METHODS:
Eight endurance male athletes (19 ± 1 years, 171.2 ± 6.4 cm, 63.1 ± 8.2 kg, VO2max: 56.4 ± 6.4 ml/kg/min) performed 60min endurance exercise under two different environments (1) hot environment (HOT: 35℃,50%RH), (2) thermoneutral environment (CON: 20℃,50%RH). Exercise in each trial was performed between 7:00 PM to 8:00 PM. Sleep variables (evaluated by EEG) and body (skin, rectal) temperature were measured during sleep.
RESULTS:
Exercise-induced increases in rectal body temperature, sweat rate, and heart rate were significantly higher in HOT compared to CON. On the other hand, no significant differences were observed between conditions for sleep efficiency, sleep latency, wake after sleep onset or time of each sleep stage (non-REM stages 1-3, REM). Furthermore, rectal and skin temperature during sleep did not differ significantly between conditions.
CONCLUSION:
Endurance exercise performed at night (7:00 PM – 8:00 PM) in a hot environment does not impair sleep quality. This may be attributable to unchanged body (rectal, skin) temperature fluctuation during sleep following the exercise in a hot environment.
References
Julien D. Périard, Thijs M. H. Eijsvogels, and Hein A. M. Daanen (2021) Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies Physiological Reviews 101:4, 1873-1979
Oda, S., & Shirakawa, K. (2014). Sleep onset is disrupted following pre-sleep exercise that causes large physiological excitement at bedtime. European Journal of Applied Physiology, 114, 1789 – 1799.