Menstrual response to running: nursing implications.

Overt (length of menstrual cycle, duration of menses, and amount of menses) and covert (luteal surge indicative of ovulation and length of luteal phase) menstrual cycle characteristics were studied in a sample of 146 women who participated in four levels of running intensity. Menstrual and running data were collected for 4 months or 3 cycles. There was a significant difference among the four groups in duration of menses and in the amount of menses, with nonrunners having significantly more days of menses and larger amounts of menses than the two highest intensity running groups. However, when a history of skipping menstrual periods between menarche and age 18 was controlled, the differences between the groups were not significant. There were no significant differences among the four groups in incidence of luteal surge or length of luteal phase. When runners were compared to nonrunners, runners reported, on average, a shorter luteal phase than nonrunners. This difference remained when controlling for age and history of skipping menstrual periods. There was no significant difference between the four groups on incidence of ovulatory disturbances (anovulation or more than one cycle with a shortened luteal phase). But, when compared to nonrunners, runners were found to have significantly more ovulatory disturbances. The best predictors of the variance in menstrual cycle characteristics were history of skipping periods between menarche and age 18, and running versus nonrunning.