Ice Slurry Mitigates Hyperventilation and Cerebral Hypoperfusion, and May Enhance Endurance Performance in the Heat

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PURPOSE: Hyperthermia causes hyperventilation and associated cerebral hypoperfusion, both of which may limit endurance performance in the heat. Here, we investigated the hypothesis that pre-exercise ice slurry ingestion may mitigate hyperventilation and cerebral hypoperfusion during exercise in the heat, enhancing endurance performance. METHODS: Twelve healthy men ingested 7.5 g·kg -1 body weight of ice slurry (Ice) or the same solution at 37°C (Con) within 30 min. Thereafter, the participants performed cycle exercise for 30 min at 55% of peak oxygen uptake in the heat (35°C), followed by a cycle exercise at 90% of peak oxygen uptake until exhaustion. RESULTS: Esophageal, rectal, and gastrointestinal temperatures were lower throughout moderate-intensity exercise in the Ice than the Con trial (all P < 0.05). Correspondingly, minute ventilation was lower and cerebral blood flow index was higher in the Ice trial (both P ≤ 0.042, main effects of trial). Subjective severity of diarrhea and stomachache was increased in the Ice versus Con trial (both P ≤ 0.041, main effects of trial). The duration of high-intensity exercise was not statistically different between the two trials ( P = 0.160), although 8 out of the 10 participants exercised for a longer duration in the Ice trial, with a moderate effect size ( r = 0.47). Based on z -scores and Grubbs' test, one outlier, who exhibited an extreme increase in ventilation and gastrointestinal complaints following ice slurry ingestion, showed a marked reduction in exercise duration. CONCLUSIONS: Pre-exercise ice slurry ingestion alleviates hyperventilation and cerebral hypoperfusion during submaximal exercise in the heat and potentially improves subsequent high-intensity endurance performance, although the adverse effects associated with ice slurry ingestion might hinder the ergogenic effect in some individuals.

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