Selected physiological and menstrual characteristics of runners and non-runners

Includes bibliographical references (pages 77-85)The purpose of this study was to determine if low\ud percent body fat, strenuous exercise, or a combination of\ud the two are primarily responsible for menstrual dysfunction\ud in athletes and non-athletes.\ud Thirty-one women between 17 and 39 years old\ud participated in the study. The subjects were categorized\ud into four groups: l) amenorrheic controls, 2) amenorrheic\ud runners, 3) normally-menstruating runners,\ud 4) normally-menstruating controls. Height, weight,\ud hematocrit and hemoglobin levels, percentage of body fat by hydrostatic weighing and skinfold methods were determined\ud for each subject. In addition, all subjects\ud completed a questionnaire regarding personal data, training\ud schedules, weight changes, menstrual and reproductive\ud history, and contraceptive information. Serial blood\ud samples were taken from a subset of nine amenorrheic subjects\ud for hormone analyses.\ud The major findings regarding the two hypotheses are\ud as follows:\ud 1. Amenorrheic controls and amenorrheic runners\ud did not differ in body weight, percent body fat by skinfold\ud technique, or hematocrit and hemoglobin levels.\ud However, amenorrheic runners had significantly fewer\ud menstrual periods in the previous year than did amenorrheic\ud controls. Analysis of the data suggests that the\ud controls had higher levels of estrogen and FSH. These\ud findings suggest that the added stress of exercise, to \ud below normal ranges of body fat and body weight, may \ud contribute to further disturbances of menstrual function.\ud 2. An unanticipated finding in this study was that\ud hydrostatic weighing and K40 formulas appear to be\ud population specific and overestimate the relative fat of\ud an underweight ectomorphic female population. Because\ud of this finding an accurate comparison of percent body\ud fat between amenorrheic controls and the other study\ud groups could not he made. However, it was substantiated\ud that by use of hydrostatic weighing, normal competitive\ud runners averaged 18.5% body fat; whereas amenorrheic\ud competitive runners averaged 13.3%, Normal runners also\ud tended to be somewhat heavier than amenorrheic runners\ud and amenorrheic controls. A mean weight loss of 8 kg\ud over a period of three years or less for the amenorrheic\ud controls appeared to be responsible for their menstrual\ud irregularities.\ud It was concluded that exercise, total body weight,\ud weight loss, and percent body fat each have a significant\ud effect on menstrual function