This isn't a technical answer to the request for research on lactational amenorrhea and exercise, just some general info. Many women who engage in extensive physical exercise such as marathon running, tennis, even gymnastics, find that their body fat levels far very very low. This is correlated with anovulation and amenorrhea several mechanisms have been proposed, but the basic idea is that your body interprets the low levels of nutritional reserves as a sign that the environmental conditions are not good for a pregnancy and several years of lactation. If your body is sending signals that you don't have the energy reserves to give a pretty good guarantee of a healthy pregnancy and lactation, then your body cuts its losses by not ovulating, not menstruating, not getting pregnant. Breastfeeding will contribute to low body fat stores a little bit (most of the necessary nutrients are extracted from the food, rather than drawing on reserves). If this woman wants to get pregnant again and is having irregular or no menstrual periods, she probably needs to have her body fat levels assessed, maybe cut back on the exercise and increase her food intake. You can do a literature search under "Rose Frisch" and "Sara Quandt" for more references. ---------------------------------------------------------------------------- ------- Katherine A. Dettwyler, Ph.D. email: [log in to unmask] Anthropology Department phone: (409) 845-5256 Texas A&M University fax: (409) 845-4070 College Station, TX 77843-4352