Purpose: To investigate the effect of ice slurry ingestion on thermoregulatory responses and submaximal running time in the heat.
Methods: On two separate occasions, in a counterbalanced order, 10 males ingested 7.5 g·kg−1 of either ice slurry (−1°C) or cold water (4°C) before running to exhaustion at their first ventilatory threshold in a hot environment (34.0°C ± 0.2°C, 54.9% ± 5.9% relative humidity). Rectal and skin temperatures, HR, sweating rate, and ratings of thermal sensation and perceived exertion were measured.
Results: Running time was longer (P = 0.001) after ice slurry (50.2 ± 8.5 min) versus cold water (40.7 ± 7.2 min) ingestion. Before running, rectal temperature dropped 0.66°C ± 0.14°C after ice slurry ingestion compared with 0.25°C ± 0.09°C (P = 0.001) with cold water and remained lower for the first 30 min of exercise. At exhaustion, however, rectal temperature was higher (P = 0.001) with ice slurry (39.36°C ± 0.41°C) versus cold water ingestion (39.05°C ± 0.37°C). During exercise, mean skin temperature was similar between conditions (P = 0.992), as was HR (P = 0.122) and sweat rate (P = 0.242). After ice slurry ingestion, subjects stored more heat during exercise (100.10 ± 25.00 vs 78.93 ± 20.52 W·m−2, P = 0.005), and mean ratings of thermal sensation (P = 0.001) and perceived exertion (P = 0.022) were lower.
Conclusions: Compared with cold water, ice slurry ingestion lowered preexercise rectal temperature, increased submaximal endurance running time in the heat (+19% ± 6%), and allowed rectal temperature to become higher at exhaustion. As such, ice slurry ingestion may be an effective and practical precooling maneuver for athletes competing in hot environments.
1School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Joondalup, WA, AUSTRALIA; and 2National Heat Training and Acclimatisation Centre, Northern Territory Institute of Sport, AUSTRALIA
Address for correspondence: Rodney Siegel, B.App.Sc. (Hons), School of Exercise, Biomedical and Health Sciences, Edith Cowan University, 270 Joondalup Dr, Joondalup, WA, Australia 6027; E-mail: firstname.lastname@example.org.
Submitted for publication May 2009.
Accepted for publication August 2009.