Immediate treatment with cold water immersion (CWI)is the gold standard for exertional heatstroke. In the field, however, treatment is often delayed due to delayed paramedic response and/or inaccurate diagnosis. We examined the effect of treatment (reduction of rectal temperature to 37.5°C) delays of 5, 20, and 40 min on core cooling rates in eight exertionally heat-stressed (40.0°C rectal temperature) individuals. We found that rectal temperature was elevated above baseline (P < 0. We conclude that the effectiveness of 2°C CWI as a treatment for exertional heat stress remains high even when applied with a delay of 40 min. Therefore, our results support that CWI is the most appropriate treatment for exertional heatstroke as it is capable of quickly reversing hyperthermia even when treatment is commenced with a significant delay.

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