The "Runner's High" was first described in the 1970's. Runners, after covering lengthy distances, described their mood as euphoric. This description initiated a great deal of research to determine if the "runner's high" had a basis in physiology. In the 80's a number of studies were published linking the "runner's high" to the release of endorphins, natural opioids produced by the body. Research suggested that endorphins released during extended endurance exercise acted similar to morphine producing feelings of euphoria. In other words, endorphin release created the "runner's high". Case closed.
The "runner's high" has become an Integral part of the literature of endurance exercise. A search of Google shows many current articles on endorphin release. However, scientific scrutiny reveals the endorphin effect doesn't hold up to science. Yes, there are clearly measurable and positive mood changes discernible after extended endurance exercise. Unfortunately most researchers are convinced it is not due to endorphins.
The major evidence against endorphins is they are large molecules, too large to get to the brain where mood changes take place. So if it is not endorphins what is the cause of runner's high? You'll be surprised to learn the answer in next week's Performance Tip.