Effects of the menstrual cycle on selected responses to short constant-load exercise

The purpose of this study was to determine whether there were differences in blood lactate (La), pulmonary ventilation (VE), rating of perceived exertion (RPE), volume of carbon dioxide expired (VCO2), oxygen consumption (VO2) and heart rate (HR) among four phases of the menstrual cycle during short constant-load exercise. The subjects of this investigation were 21 female physical education students at Springfield College. After determination of maximal oxygen consumption (VO2 max) on the bicycle ergometer, subjects exercised at intensities designed to elicit 70 and 90% VO2 max in each of four phases of the menstrual cycle : menses, follicular (F), luteal (L) and premenses (PM). Phases were identified by menstrual history and variation in basal morning oral temperatures. For purposes of description the variation in body weight was analysed by a one-factor ANOVA across the four phases of the menstrual cycle. Post hoc comparisons revealed that body weight was higher (P 0.05) in PM when compared to L and F, but there was no difference between PM and menses, and among menses, L and F. Each criterion variable was treated by a 4 x 2 ANOVA with repeated measures on both factors to compare responses across phases of the menstrual cycle at differing exercise intensities. There were no significant differences in La, VE, RPE, VO2, VCO2 and HR among the four phases of the menstrual cycle at exercise intensities corresponding to 73 and 90% VO2 max. It was concluded that these dependent variables are not affected by the menstrual cycle during short constant-load exercise in women who do not experience dysmenorrhoea.