Effects of short term and prolonged immersion on the cardiovascular responses to exercise

The primary purpose of this investigation was to examine the effects of water immersion in 35°C water, per se, and the effects of 3 h of water immersion on the physiological responses to exercise. Experiments in air were conducted after 15 min of water immersion and after 3 h of water immersion. After each condition, exercises of 20%, 40%, 60%, 80%, and 100% of the subject's maximum oxygen consumption were performed on a cycle ergometer. Oxygen consumption (V̇O₂), cardiac output, heart rate (HR), stroke volume, and blood pressure were determined. At submaximal workloads, no significant differences in the data were observed. The V̇O₂ at the maximal workload after 3 h of immersion (3.32 ± 0.15 L · min^-1) was significantly higher than the value after 15 min of immersion (3.03 ± 0.20 L · min^-1). Both of these values were significantly lower than the value in air (3.83 ± 0.30 L · min^-1). The peak HR's were significantly higher after 3 h of immersion (167 ± 2 b · min^-1). These observations suggest that 3 h of immersion can cause alterations in the cardiovascular responses to maximal exercise; however, submaximal responses were unaffected.