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.

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.

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.

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.

Previous research has demonstrated that ingesting fluid of different temperatures results in different whole-body sweat losses (WBSL) and transient changes in local sweat rate (LSR) without any parallel differences in core or skin temperatures. The purpose of this thesis was to determine the potential location and relative contribution of gastrointestinal thermoreceptors that modify sudomotor activity. Eight participants cycled for 75 min while cold (1.5°C) and warm (50°C) water was either swilled in the mouth, or delivered directly to the stomach bypassing the mouth using a nasogastric tube, after 15, 30 and 45-min of exercise. Mouth-swilling warm or cold water did not alter sudomotor output, however delivering warm or cold water directly into the stomach led to a temperature-dependent change in sudomotor output, despite similar core and skin temperatures. These data indicate that thermoreceptors independently modulating sudomotor output probably reside within the abdominal area, but not the mouth.

Previous research has demonstrated that ingesting fluid of different temperatures results in different whole-body sweat losses (WBSL) and transient changes in local sweat rate (LSR) without any parallel differences in core or skin temperatures. The purpose of this thesis was to determine the potential location and relative contribution of gastrointestinal thermoreceptors that modify sudomotor activity. Eight participants cycled for 75 min while cold (1.5°C) and warm (50°C) water was either swilled in the mouth, or delivered directly to the stomach bypassing the mouth using a nasogastric tube, after 15, 30 and 45-min of exercise. Mouth-swilling warm or cold water did not alter sudomotor output, however delivering warm or cold water directly into the stomach led to a temperature-dependent change in sudomotor output, despite similar core and skin temperatures. These data indicate that thermoreceptors independently modulating sudomotor output probably reside within the abdominal area, but not the mouth.