title: Menstrual cycle and exercise effects on protein catabolism.
abstract: The purpose of this investigation was to determine whether exercise at different times of the menstrual cycle alters protein catabolism. Nine women exercised for 60 min at 70% VO2max when serum estradiol (E) and progesterone (P) were low (menses) and when both were high [mid-luteal (ML)]. Diet was reproduced on both occasions. Serum urea nitrogen (N), E, and P were analyzed at rest, after 15, 30, 45, and 60 min of exercise, and 15 min into recovery. Sweat urea N excretion was also determined. Urinary area N excretion was measured the day before, the day of, and 2 d following exercise. E and P were significantly greater in the ML phase, and this difference was maintained throughout exercise (P less than 0.05). No change was seen in serum urea N across exercise or between phases. Both exercise day urinary urea N excretion and total urea N excretion in sweat and urine, when added across all experimental days, were significantly greater in the ML phase compared to menses (8.5 +/- 0.96 vs 5.5 +/- 0.81 g and 24.8 +/- 2.38 vs 19.3 +/- 1.38 g, respectively, P less than 0.05). The data suggest that the greater protein use in the ML phase was due to the combined effects of exercise, a changing hormonal milieu and other unknown causes.
mesh_terms: D000328:Adult; D001806:Blood Urea Nitrogen; D004958:Estradiol / Q000097:blood; D005260:Female; D006801:Humans; D008597:Menstrual Cycle; D009584:Nitrogen / Q000378:metabolism* / Q000652:urine; D005082:Physical Exertion; D011374:Progesterone / Q000097:blood; D011506:Proteins / Q000378:metabolism*; D013542:Sweat / Q000378:metabolism
chemical_list: D011506:Proteins; D011374:Progesterone; D004958:Estradiol; D009584:Nitrogen