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

Abstract

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. 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. 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. 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.