Body temperature, respiration, and acid-base equilibrium during prolonged running.

The purpose of this investigation was to study respiratory responses related to acid-base equilibrium during two bouts of prolonged high intensity treadmill running, each at different body temperature levels. In an attempt to augment elevation in body temperature during prolonged running, incomplete rehydration procedures were employed. Rectal temperature was found to increase significantly during the course of each run. In addition, rectal temperature was found to be significantly higher during the second run at each respective time period. After the transition to exercise, plasma volume, arterial lactate concentration, arterial hydrogen ion concentration, arterial carbon dioxide partial pressure, arterial bicarbonate concentration, pulmonary ventilation, and ventilatory equivalent of carbon dioxide remained constant throughout each run. It was also found that arterial carbon dioxide partial pressure was lower and ventilatory equivalent of carbon dioxide was higher during the second run at each respective time period. For the studied population, these results indicate that after initial adjustments most of the examined variables remain fairly constant despite increasing rectal temperature during prolonged running.