Analysis of plasma volume changes and total plasma protein movement during walking exercise in neutral, hot-dry, and hot-humid environments during follicular and luteal phases of the menstrual cycle

The purpose of this study was to determine whether menstrual cycle phase influences plasma volume changes and total plasma protein movement before, during, or after walking exercise in neutral (25°C, 50% relative humidity [RH]), hot-dry (35°C, 30%RH), and hot-wet (35°C, 70% RH) environments. Nine female subjects were tested in each of the three environments in either the luteal or follicular phase of the menstrual cycle. For each subject the workload for the treadmill exercise was determined to cost 17.5 W/m 2 body surface area (BSA) during the 60 min exercise period. Measurements of heart rate (HR), mean skin temperature (Tsk), rectal temperature (Tre), mean body temperature (Tb), and oxygen consumption (VO2) were recorded every 5 min throughout the session.;The results indicated that subject characteristics, such as height, weight, BSA, body composition, and maximum oxygen consumption (VO2max) did not differ significantly between follicular and luteal groups within each environment. Total sweat loss (TSL) and sweat rate (SR) were lower in the neutral environment than the hot environments, but not different between the hot environments. SR based on body surface area (SR/BSA) was lowest in the neutral environment and highest in the hot-wet environment. Sweat responses did not differ between luteal and follicular groups in any environment T sk, Tre, and Tb were generally lowest in the neutral environment but did not differ significantly between the two hot environments. Tsk, Tre, and Tb increased over time and this increase tended to occur earliest in the hot-wet environment. Luteal subjects experienced higher Tre during recovery in the hot-dry environment and higher Tb during equilibration and exercise in the neutral environment compared to foIlicular subjects. HR measures were significantly lower during exercise and recovery in the neutral environment compared to the hot-wet environment. HR measures increased throughout the exposures in all environments, but there was no effect due to menstrual status.;FBF was lower in the neutral environment than in the hot-wet environment, but only significantly so during equilibration. FBF increased with exercise in all three environments. There were no menstrual cycle effects on FBF in the neutral, hot-dry, or hot-wet environment. PP movement did not vary between environments. PP movement into the vascular compartment occurred by the end of recovery in the neutral environment, but there was no significant PP movement in the hot environments. Menstrual cycle phase did not affect PP movement. PV increased (hemodilution) in the neutral environment and decreased (hemoconcentration) in the hot environments. In the hot-wet environment the hemoconcentration was more gradual than in the hot-dry environment; however, the hot environments did not differ at the end of recovery in the amount of PV loss. There were no significant differences in PV changes due to menstrual cycle phase. (Abstract shortened by UMI.)...