Influence of Menstrual Cycle and Oral Contraceptives on Tolerance to Uncompensable Heat Stress


  1. Tenaglia, S.A.
  2. McLellan, T.M.
  3. Klentrou, P.P.
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN)
In this study we examined the influence of menstrual cycle phase and oral contraceptive use on thermoregulation and tolerance during uncompensable heat stress. Eighteen women (18-35 years), who differed only with respect to oral contraceptive use (n = 9) or non-use (n = 9), performed light intermittent exercise at 40C and 30% relative humidity while wearing nuclear, biological and chemical protective clothing. Their responses were compared during the early follicular (EF, days 2-5) and mid-luteal (ML, days 19-22) phases of the menstrual cycle. Since oral contraceptives are presumed to inhibit ovulation, a quasi-early follicular (q-EF) and quasi-mid-luteal (q-ML) phase was assumed for the users. Estradiol and progesterone measurements verified that all subjects were tested during the desired phases of the menstrual cycle. Results demonstrated that rectal temperature (Tre) was elevated in ML compared with EF among the non-users at the beginning and throughout the heat-stress trial. For the users, Tre was higher in q-ML compared with q-EF at the beginning, and for 75 min of the heat-stress exposure. Tolerance times were significantly longer during EF (128.1 (13.4) min, mean (SD))compared with ML (107.4 (8.6) min) for the non-users, indicating that these women are at a thermoregulatory advantage during the EF phase of their menstrual cycle. TRUNCATED
Follicular phase;Luteal phase;Work tolerance time
Report Number
DCIEM-98-P-09 — Reprint
Date of publication
22 Jan 1999
Number of Pages
Reprinted from
Eur J Appl Physiol, vol 80, 1999, p 76-83
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