Author(s): IWATA, R., NAKAMURA, M., TAKAHASHI, S., TAMAI, S., SASADAI, J., SHIMIZU, R., FUKAMI, K., SHOJI, R., NAKAJIMA, K., Institution: JAPAN INSTITUTE OF SPORTS SCIENCES, Country: JAPAN, Abstract-ID: 1746

INTRODUCTION:
Compared to tap water immersion, CO2-water immersion is expected to increase oxygen supply through vasodilation, decrease pain, enhance immunity, and increase parasympathetic nerve activity (1,2). Therefore, CO2-water immersion has been used in our support centers to promote recovery in athletes. However, the effects of CO2-water immersion on recovery after training or consecutive games have not been reported. The purpose of the present study was to clarify the effects of CO2-water immersion on core body temperature, sleep condition, and fatigue in college athletes after training.
METHODS:
In a crossover design, ten male college baseball players completed three trials: CO2-water immersion (CO2), tap water immersion at 40 °C (HOT), and seated at room temperature (25 °C) (CON) for 15 min after regular training. Participants wore Actiwatch sleep monitors on their wrists on the night of the experiment to evaluate their sleep state. Core temperature (Tcore) was measured throughout the night until the morning of the next day.
RESULTS:
The maximum Tcore showed moderately higher values (d = 0.534, p = 0.541) in the CO2 trail (38.12 ± 0.50 °C) than in the HOT trail (37.86 ± 0.48 °C). The CO2 and HOT trials exhibited mostly higher values (d = 1.852, p = 0.004 and 1.238, p = 0.032, respectively) than the CON trail (37.38 ± 0.27 °C). Minimal variations were observed in sleep duration (CO2, 5.76 ± 1.1 h; HOT, 5.42 ± 1.1 h; and CON, 5.93 ± 1.0 h), and the effect size was small (d < 0.5). Sleep efficiency and quality of sleep were moderately higher in the CO2 trail than in the HOT trail (d = 0.577, p = 0.574 and 0.512, p = 0.669, respectively). The difference between the Tcore at sleep onset and the maximal Tcore was slightly greater (d = 0.364, p = 0.497) in the CO2 trail (-0.94 ± 0.54 °C) than in the HOT trail (-0.78 ± 0.32 °C).
CONCLUSION:
CO2-water immersion increased core body temperatures more significantly than hot tap water immersion at 40 °C. These increased temperatures resulted in positive effects on sleep efficiency and sleep quality, which may be due in part to the significant decrease in core body temperature at the time of sleep onset.
References
(1) Ihsan M, Watson G, Abbiss CR. What are the physiological mechanisms for post-exercise cold water immersion in the recovery from prolonged endurance and intermittent exercise?. Sports Med,46(8):1095–109,2016.
(2) Versey NG, Halson SL, Dawson BT. Water immersion recovery for athletes: effect on exercise performance and practical recommendations. Sports Med,43(11):1101–30,2013.