The Effects of Differences in the Timing of Ice Ingestion before Exercise on Endurance Cycling Capacity, Body Temperature and Perceptual Sensation in the Heat*

Abstract

The timing at which ice is ingested prior to exercise may be important for optimizing internal pre-cooling effects. However, previous reports have not evaluated the influence of timing of ice ingestion on internal pre-cooling in the heat. The purpose of this study was to investigate the effects of differences in the timing of ice ingestion on endurance cycling capacity, body temperature and perceptional sensation in the heat. Seven healthy males [age=26±2 yr, height=1.71±0.04 m, body mass=63.6±2.8 kg, body surface area=1.74±0.03 m², maximal oxygen uptake (VO₂max)=49.7±4.4 mL·kg⁻¹·min⁻¹] ingested ice for 30 minutes before exercise under three separate conditions: ice ingestion at 30- (30D), 15- (15D) and 5- (5D) minute intervals. The total volume of ice ingestion was identical during 30D, 15D, 5D and was divided equally by the number of drinking times in each experiment. Subjects performed cycling to exhaustion at 70%VO₂max in a hot environment (35℃ room temperature and 30% relative humidity). Rating of thermal sensation was lower in 5D at 15 min period during exercise than those under the other conditions (p<.05). Rating of perceived exertion was lower in 5D at 20 and 25 min periods during exercise than those under the other conditions (p<.05). There were no significant differences in rectal temperature, mean skin temperature or exhaustion time between the three conditions. These results suggest that there are no significant differences in exhaustion time and rectal temperature if the total volume of ice ingestion is identical, although the ice ingestion until just before exercise attenuated the perceptual sensation during exercise in a hot environment.