Cold Water Immersion: Simultaneous Assessment of Cerebral Oxygenation, Vascular Function, and Thermoregulatory Responses.
Level 3 - non-randomized controlled study
Controlled crossover trial without stated randomization
PubMed 41247291 · doi:10.1093/milmed/usaf570
What was done
Twenty-six participants (mean age 23.6 ± 4.3 years) completed two 10-minute water immersion testing visits: thermoneutral water immersion (TWI; 35 °C) and cold water immersion (CWI; 15 °C). Investigators measured prefrontal cortex oxygenated hemoglobin (O2Hb) using functional near-infrared spectroscopy (fNIRS), common carotid artery (CCA) diameter, respiratory rate, tidal volume, skin temperature, and thermal perception.
What was found
Prefrontal cortex O2Hb increased significantly during CWI (P < .01) but did not change during TWI (P = .15). CCA diameter increased during CWI (P < .01) and was unchanged during TWI (P = .84). Tidal volume was significantly greater during CWI compared to TWI (P < .01), showing an initial 43% increase, while respiratory rate remained unchanged (P = .59). Skin temperature decreased (P < .01) and thermal perception was greater (P < .01) during CWI compared to TWI.
Why it matters
This study shows that acute cold water immersion elicits rapid increases in prefrontal oxygenation and common carotid artery diameter alongside hyperpnea, demonstrating the feasibility of using fNIRS to monitor neurovascular responses under cold stress.
Limits
The sample was small (n = 26) and restricted to young adults, with no indication of whether condition order was randomized. Cognitive and physical performance tasks were not tested directly, and core body temperature was not reported in the abstract.