Thermoregulation in shallow water aquatic exercise during second trimester pregnancy

Thermoregulation in shallow water aquatic exercise during second trimester pregnancy in two environmental conditions (control = 27.7 and treatment = 33.5°C) was investigated. Twelve subjects (age = 27.6 +/- 4.4 years) volunteered to participate. Oxygen consumption, heart rate, rating of perceived exertion, and core temperature were measured prior to, during, and following 50 minutes of aquatic exercise in each condition. There were no significant differences in maternal core temperature during exercise due to water temperature conditions. Regardless of condition, core temperature significantly increased during exercise. The mean core temperature change in the control (0.35°C) versus the treatment (0.39°C) condition was not significant. Two subjects stopped exercise in both the control and treatment conditions due to core temperature elevation greater than 38°C. Total body water loss to estimate sweat rate was significantly higher (p = 0.002) in the treatment (mean = 0.26 kg) versus control (mean = 0.10 kg) conditions. Oxygen consumption was not significantly different due to water temperature conditions. Oxygen consumption was significantly greater during the exercise session compared to the warm-up and cool-down periods. Rating of perceived exertion (RPE) was not significantly different between treatments, but significantly increased during exercise. Heart rate was significantly greater during exercise in the treatment versus the control conditions. These results suggest that the thermoregulatory response to aquatic exercise is similar between 27.7°C and 33.5°C water temperatures. Individual thermoregulatory responses suggest that sedentary subjects with excess body fat may need to monitor exercise intensity to reduce risk of hyperthermia.