title: Menstrual cycle phase and carbohydrate ingestion alter immune response following endurance exercise and high intensity time trial performance test under hot conditions.
abstract: BACKGROUND
  Sex hormones are known to regulate some responses during exercise. Evaluation of the differences in exercise response with regard to menstrual cycle will help understand the menstrual cycle phase specific adaptations to exercise and athletic performance.
  
  
  METHODS
  We investigated the effects of menstrual cycle phase and carbohydrate (CHO) ingestion on immune response during endurance exercise at 30°C. Six healthy women completed 4 trials comprising 90 min of cycling at 50% peak aerobic power [Formula: see text] and a high intensity time trial performance test (POST). They ingested a placebo- or CHO-containing beverage during the trials, which were performed during both the follicular and luteal phases of the menstrual cycle. In all trials, thermoregulatory, cardiorespiratory, and immune responses were measured during exercise and after POST.
  
  
  RESULTS
  Although the thermoregulatory responses differed between the menstrual cycle phases, the cardiorespiratory responses were not different. After placebo ingestion, leukocyte concentration (cells/μL) at POST (15.9 × 10(3)) in the luteal phase was significantly higher than that in the follicular phase (12.9 × 10(3)). The rise in leukocyte concentration was attenuated upon CHO ingestion, and the difference between menstrual cycle phases disappeared. A significant positive correlation was found between leukocyte concentration and serum free fatty acid concentrations. Interleukin-6, calprotectin, and myeloperoxidase concentrations significantly increased at POST in all trials, but no significant differences were observed between menstrual cycle phase or beverage type. Concentrations of other cytokines did not change during exercise in any of the 4 trials. Menstrual cycle phase and beverage type had no significant effect on the POST outcome. Thus, differences in leukocyte mobilization between menstrual cycle phases could result from the effect of sex hormones on substrate utilization.
  
  
  CONCLUSIONS
  The menstrual cycle affected circulating leukocyte concentrations during endurance exercise with POST when a placebo was ingested. Therefore, we recommend ingesting CHO beverages to attenuate immune disturbances, especially in the luteal phase, even though they are unlikely to enhance test performance.
authors.affiliation: Faculty of Sport Sciences, Waseda University, Saitama, Japan ; Products Research & Development Laboratory, Asashi Soft Drinks Co., Ltd, Ibaraki, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Hashimoto
authors.affiliation: Faculty of Sport Sciences, Waseda University, Saitama, Japan ; School of Human Culture, The University of Shiga Prefecture, Shiga, Japan.
authors.forename: Toshimichi
authors.initials: T
authors.lastname: Ishijima
authors.affiliation: Faculty of Sport Sciences, Waseda University, Saitama, Japan ; Faculty of Health Promotional Sciences, Tokoha University, Shizuoka, Japan.
authors.forename: Harumi
authors.initials: H
authors.lastname: Hayashida
authors.affiliation: Faculty of Sport Sciences, Waseda University, Saitama, Japan.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Faculty of Sport Sciences, Waseda University, Saitama, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Higuchi
keywords: Carbohydrate; Cytokines; Leukocytes; Prolonged exercise