The effect of water intake on post-exercise hyperthermia: Investigating the implications for theories of thermoregulation.

The purpose of this investigation was to examine the role of water intake on post-exercise hyperthermia. Ten active, non-competitive male volunteers performed twenty minute treadmill exercise at equal relative intensities during two separate trials where: (1) gradual hypohydration took place, and (2) euhydration was induced by water ingestion in order to compensate for the body water volume loss demonstrated in the hypohydrated condition. Core temperature, represented by both esophageal and rectal temperatures, was recorded, along with surface temperatures (forearm, finger, chest thigh, and calf) and heart rate during a twenty-one minute adaptation period, throughout exercise and for forty minutes of recovery. Hematocrit samples were taken immediately prior to and following the exercise protocol and subject weights were measured before and after the testing session. The interaction between trials and time for esophageal and rectal temperatures and the difference between the hypohydration and euhydration trials for esophageal and rectal temperatures were all non-significant, and demonstrated that core temperature values did not differ between the hypohydrated and euhydrated conditions. However, core temperature was significantly different across time for both esophageal and rectal temperatures, due to a post-exercise elevated plateau from pre-exercise values. This elevation corresponded to the core temperature at which skin vessel dilation occurred during e exercise for both trials. The correlation between the difference in the hypohydration and euhydration esophageal elevations and the absolute and relative percentage weight loss of each subject after hypohydration further demonstrated a weak role for water intake in post-exercise hyperthermia. Several hypotheses are proposed to explain the post-exercise core temperature elevations in both the hypohydrated and euhydrated trials and the lack of significant difference between the two trials. (Abstract shortened by UMI.