Comparison of the effects of cold water and ice ingestion on endurance cycling capacity in the heat

Purpose The purpose of this study was to examine the effects of pre-cooling and fluid replacement with either crushed ice or cold water. Methods On 2 separate occasions, in a counterbalanced order, 9 recreationally-trained males ingested 1.25 g/kg (80–100 g) of either crushed ice (0.5°C) or cold water (4°C) every 5 min for 30 min before exercise. They also ingested 2.0 g/kg (130–160 g) of the same treatment drink at 15 min, 30 min, and 45 min after the commencement of cycling to exhaustion at 60%VO_2max until voluntary exhaustion in a hot environment (35°C and 30% relative humidity). Results The cycling time to exhaustion in the crushed ice trial (50.0 ± 12.2 min) was longer than the cold water trial (42.2 ± 10.1 min; p = 0.02). Although the rectal temperature fell by 0.37°C ± 0.03°C (p = 0.01) at the end of the resting period after the crushed ice ingestion, the rates of rise in rectal temperature during the exercise period were not significantly different between these 2 conditions (crushed ice: 0.23°C ± 0.07°C, 5 min; cold water: 0.22°C ± 0.07°C, 5 min; p = 0.94). Conclusion Crushed ice ingestion before and during exercise in a hot environment may be a preferred and effective approach for minimizing thermal strain, and for improving endurance performance as compared with cold water ingestion.