EXERCISE INTENSITY - AN IMPORTANT FACTOR IN THE ETIOLOGY OF MENSTRUALDYSFUNCTION

The objective of this case control study was to compare training activ ity in female long distance runners with irregular (IR, n = 13) and re gular (R, n = 16) menstrual function, especially with regard to exerci se intensity. Serum estradiol concentration during the follicular phas e was considered normal in the R subjects (31 +/- 6 pg/l). In contrast , the IR runners were clearly hypoestrogenic (11 +/- 1.6 pg/l). The tw o groups had similar Vo(2max), anaerobic threshold (AT) and maximal he art frequency (HFmax). In both groups AT was found at 88% of HFmax. Th e two groups had similar mean race results in half marathons during th e previous year. The number of running contests was, however, twice as high in the IR group. A light portable pulse recorder was used to mon itor heart rate during 1 week of regular training activity, and during a controlled high intensity work-out. During a week with normal train ing activity, an equal amount of training at high intensity levels (>8 5% HFmax) was performed by the two groups. The amount of training at l ower intensities (<85% HFmax) was, however, more extensive in the grou p with irregular menstrual function. During the controlled self-admini stered, high intensity work-out, the amounts of training at and above AT were equal in the two groups. In conclusion: no difference in exten t of high intensity training between long distance runners with regula r and irregular menstrual function could be found in the present study group. The IR runners did, however, have significantly more training activity at lower intensity levels, and more frequent race participati on.