Body Heat Storage, Sweating and Skin Blood Flow Responses Following Cold and Warm Water Ingestion during Exercise

Abstract

Ingestion of cold (<10°C) compared to warm (>37°C) fluid has been suggested to attenuate heat storage levels during exercise. However, modulations in sweat output may yield differences in evaporative heat loss that are greater than differences in heat transfer with the ingested fluid. The purpose of the thesis was to evaluate thermoregulatory control and human heat balance, and compare thermometrically derived values of heat storage with those derived from partitional calorimetry following water ingestion of varying temperature during exercise. We found that water ingestion of 50°C compared to 1.5°C decreases heat storage in thermoneutral environments, and further exacerbates the error of thermometric heat storage estimations. Differences in heat storage were attributed exclusively to disproportionate reductions in whole-body and local sweat output and thus evaporative heat loss potential. Ingested fluid temperature only minimally altered skin blood flow and did not influence dry heat exchange with the ambient environment.