Recreational Exercise Does Not Impair Menstrual Cycles: A Prospective Study

Abstract

To determine whether recreational levels of training (jogging) will provoke short luteal phase menstrual cycles, a prospective study was conducted. Out of 132 women who initiated this study 57 completed it. These individuals were within normal range of cardiorespiratory fitness for 18-40-year-old women. After a control menstrual cycle (#1) and two additional menstrual cycles (#2 and #3) in which light calisthenics were performed, the subjects were then assigned to run less than 10 mi/wk, 10-20 mi/wk or 20-30 mi/wk for either two menstrual cycles (#4 and #5), or four menstrual cycles (#4, #5, #6, #7), followed by a detraining period lasting two menstrual cycles (i.e. #6 and #7 for the 2-month running groups; #8 and #9 for the 4-month running groups). Blood samples were obtained throughout every second menstrual cycle (i.e. cycles #1, #3, #5, #7, #9). Samples were assayed for LH, FSH and P. Body weight and body fat (%) were not altered by training (p greater than 0.05). Improvements in cardiovascular fitness did occur (p less than 0.05). No change in LH attributable to running was found in any of the 6 experimental groups (p greater than 0.05). In some of the groups quite large changes occurred in FSH (p less than 0.05), but there was no discernable pattern of onset of these changes among groups. Some increments in P were found (p less than 0.05) but again these were not consistent. Finally, in none of the six groups was an altered menstrual cycle length discernable (p greater than 0.05), nor was the luteal phase length altered (p greater than 0.05) by running. Therefore, in gynecologically mature women recreational running of up to 30 miles/week for 4 menstrual cycles has no deleterious effects upon their menstrual cycle.