Perceived exertion and anaerobic threshold during the menstrual cycle

Six adult females with normal menstrual cycles (28-31 d in length) volunteered to exercise on a bicycle ergometer on five different days of their menstrual cycles (days 2, 8, 14, 20, and 26; day 1 = onset of menstruation). Each day the subjects exercised at a maximum work load (184.4 W) and at four submaximal exercise intensities (45.0, 83.1, 121.4 and 154.4 W). Ratings of perceived exertion (RPE) were obtained during minute 4 of each 5-min submaximal exercise bout and at exhaustion each day. Overall, RPE was linearly correlated with heart rate (r = 0.87) when all exercise intensities and cycle days were considered. There was no statistically significant (P greater than 0.05) change in RPE at any exercise intensity related to cycle day. Factors (expired ventilatory volume, respiratory frequency, tidal volume, end-tidal CO2 tension, and heart rate) that may have affected RPE, maximal aerobic power, and anaerobic threshold (AT) were also statistically unchanged because of cycle day. Anaerobic threshold averaged 68.7% of the VO2max, or 1.592 l . min for all cycle days, as determined by the total expiratory volume/oxygen uptake "break point" method of Wasserman and co-workers (18). These data support the utilization of female subjects with normal menstrual cycles in psychophysiological studies without regard to menstrual cycle phase.