Ice slurry on outdoor running performance in heat.

The efficacy of ingestion of ice slurry on actual outdoor endurance performance is unknown. This study aimed to investigate ice slurry ingestion as a cooling intervention before a 10 km outdoor running time-trial. Twelve participants ingested 8 g · kg (- 1) of either ice slurry ( - 1.4°C; ICE) or ambient temperature drink (30.9°C; CON) and performed a 15-min warm-up prior to a 10 km outdoor running time-trial (Wet Bulb Globe Temperature: 28.2 ± 0.8°C). Mean performance time was faster with ICE (2 715 ± 396 s) than CON (2 730 ± 385 s; P=0.023). Gastrointestinal temperature (Tgi) reduced by 0.5 ± 0.2°C after ICE ingestion compared with 0.1 ± 0.1°C (P<0.001) with CON. During the run, the rate of rise in Tgi was greater (P=0.01) with ICE than with CON for the first 15 min. At the end of time-trial, Tgi was higher with ICE (40.2 ± 0.6°C) than CON (39.8 ± 0.4°C, P=0.005). Ratings of thermal sensation were lower during the cooling phase and for the first kilometre of the run ( - 1.2 ± 0.8; P<0.001). Although ingestion of ice slurry resulted in a transient increase in heat strain following a warm up routine, it is a practical and effective pre-competition cooling manoeuvre to improve performance in warm and humid environments.