title: The effect of the menstrual cycle and water consumption on physiological responses during prolonged exercise at moderate intensity in hot conditions.
abstract: BACKGROUND
  Reproductive hormones are likely to be involved in thermoregulation through body fluid dynamics. In the present study, we aimed to investigate the effect of the menstrual cycle and water consumption on physiological responses to prolonged exercise at moderate intensity in hot conditions.
  
  
  METHODS
  Eight healthy young women with regular menstrual cycles performed cycling exercise for 90 minutes at 50% V̇O2peak intensity during the low progesterone (LP) level phase and high progesterone (HP) level phase, with or without water consumption, under hot conditions (30°C, 50% relative humidity). For the water consumption trials, subjects ingested water equivalent to the loss in body weight that occurred in the earlier non-consumption trial. For all four trials, rectal temperature, cardiorespiratory responses, and ratings of perceived exertion (RPE) were measured.
  
  
  RESULTS
  Throughout the 90-minute exercise period, rectal temperatures during HP were higher than during LP by an average of 0.4 °C in the non-consumption trial (P<0.01) and 0.2 °C in the water consumption trial (P<0.05). During exercise, water consumption affected the changes in rectal temperature and heat rate (HR) during HP, but it did not exert these effects during LP. Furthermore, we found a negative correlation between estradiol levels and rectal temperature during LP.
  
  
  CONCLUSIONS
  During prolonged exercise at moderate intensity under hot conditions, water consumption is likely to be useful for suppressing the associated increase in body temperature and HR, particularly during HP, whereas estradiol appears to be useful for suppressing the increase in rectal temperature during LP.
authors.affiliation: Faculty of Sport Sciences, Waseda University, Saitama, Japan - hideki.hashimoto@asahiinryo.co.jp.
authors.forename: Hideki
authors.initials: H
authors.lastname: Hashimoto
authors.forename: Toshimichi
authors.initials: T
authors.lastname: Ishijima
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Suzuki
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Higuchi
mesh_terms: D000328:Adult; D001831:Body Temperature; D001833:Body Temperature Regulation / Q000502:physiology; D004326:Drinking; D004958:Estradiol / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate; D006358:Hot Temperature; D006801:Humans; D008597:Menstrual Cycle / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D011374:Progesterone / Q000097:blood; D055815:Young Adult
chemical_list: D011374:Progesterone; D004958:Estradiol