Core body temperature responses during lower-body cold water immersion using carbon dioxide hydrate

This study aimed to investigate the effect of lower-body cold water immersion (CWI) using Carbon Dioxide Hydrate (CDH) on core body temperature compared to conventional ice-water CWI. Twelve healthy adult males underwent two 15-minute CWI sessions at 12°C: one with normal cold water immersion and the other with CDH-dissolved water immersion (1800 ppm CO2). Core temperature continuously monitored using ingestible capsule sessors, and subjective thermal sensation was assessed using a Numerical Rating Scale (NRS) at three timed points (immediately after CWI, midpoint CWI, end of CWI). Two-way repeated measures ANOVA revealed significant main effects of condition and time. Notably, the CDH condition showed a statistically significant reduction in core temperature at 15 minutes compared to Start CWI (p = 0.0029), No significant difference in NRS was found between conditions at any time point. CDH cold water immersion induced a greater and sustained decrease in core body temperature without increasing thermal discomfort, suggesting it is a practical and comfortable cooling strategy for field applications.