LAMONT, L. S., P. W. R. LEMON, and B. C. BRUOT. Menstrual cycle and exercise effects on protein catabolism. Med. Sci. Sports Exerc, Vol. 19, No. 2, pp. 106-110, 1987. 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% [latin capital V with dot above]O2max 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 arid P were significantly greater in the ML phase, and this difference was maintained throughout exercise (P < 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 < 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.
(C)1987The American College of Sports Medicine