Temperature of Ingested Water and Thermoregulation During Moderate-Intensity Exercise

The effect of the temperature of ingested water on the rise in core temperature (TCO) during exercise is not clear. Seven trained subjects were recruited to complete 2 hr of recumbent cycling at 51% VO2 peak in a temperate environment (Ta = 26 °C, relative humidity = 40%) on four occasions, while ingesting either no fluid (trial NF26), cold water (0.5 °C; trial CD26), cool water (19 °C; trial CL26), or warm water (38 °C; trial WA26) during the second hour of exercise. A fifth trial was conducted during which convective and radiative heat loss were reduced by raising Ta to 31 °C. During this trial, subjects ingested cold water (0.5 °C; trial CD31). When compared to WA26, over the second hour of exercise, CD26 attenuated the time-averaged changes in (TCO) and forearm blood flow and decreased whole-body sweat rate and forearm sweat rate (p < .05). Similarly, relative to WA26, the CL26 trial attenuated the time-averaged changes in TCO and reduced whole-body sweat rate (p < .05) during the second hour of exerc...