Catherine, I believe running a few miles(if you mean 2-3) a day or every other day is moderate rather than heavy exercise. For persons training for marathons they usually run 40 miles or more a week. I am not aware of any reports that moderate exercise effects prolactin secretion or causes LAM. I just recently worked with a 1st time mother who was having problems breastfeeding. I saw her for the first time 1 week post delivery. She reported very little breast changes during her pregnancy and following delivery. She is a dietician and works as a fitness instructor in a wellness center. She is also a marathon runner (just qualified for the Boston) - so she's also FAST. After much effort (i.e. pumping post feeds, SNS, etc) there was very little response in the way of milk volume. However, studies thus far have not shown exercise to have a negative influence on lactation. have not. In obtaining a history from this mother, however, she did say that she had anorexia and LAM as a teenager. It would seem to me that this could significantly effect the development of glandular breast tissue. Interesting to consider. BTW, her husband said he was going to be waiting for her at the finish line at the recent Tenneco Marathon here in Houston because they want to have another baby. She has already asked me if I think she will be successful this next time. We'll see.