Lee, J. K., Yeo, Z. W., Nio, A. Q., Ang, W. H., & Fan, P. W. (2011). Ice slurry ingestion improves subsequent outdoor 10 km running performance in the heat. Medicine and Science in Sports and Exercise, 43(5). Supplement abstract 762.

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This study investigated thermoregulatory responses and performance after the ingestion of ice slurry before an outdoor 10 km running time-trial in the heat (~28.3C). Healthy runners (M = 9; F = 4) completed a full familiarization run, followed by two experimental trials in a counterbalanced order, ingesting either 8 g/kg body mass of ice slurry or ambient temperature (30C) drink before a 10 km run. Each run was preceded by a 15 minute warm-up session. All trials were conducted on an outdoor 400 m running track. Ambient temperature drinks were provided ad libitum approximately every three kilometers in the time-trial. An ingestible temperature capsule was consumed 8 to 17 hours before all trials for measurement of gastrointestinal temperature as an index of body core temperature. Chest temperature, heart rate, sweat rate, 200 m split times, and ratings of thermal sensation and perceived exertion were assessed.

Twelve of the thirteen runners ran faster with ice slurry compared to ambient temperature drink. Before the run, gastrointestinal temperature (N = 12) decreased by ~0.5 C with ice slurry which was significantly more than with ambient temperature drink. At the end of the run, gastrointestinal temperature was significantly higher with ice slurry than with the ambient temperature drink. Mean ratings of thermal sensation were lower during the cooling phase and for the first kilometer of the run following ice slurry ingestion than with the drink. Running pace was increased at every 200 m split for the final 2.4 km of the 10 km time-trial with ice slurry. Chest temperature, heart rate, sweat rate and perceived exertion were similar during both trials.

Implication. Compared to a drink at ambient temperature, ice slurry consumption decreased body core temperature before the run and increased running pace in the final quarter of the time-trial. Ingesting ice slurry improves subsequent performance in endurance events in the heat.

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