It is described as a feeling of euphoria that occurs during or right after exercise.
There is not total agreement about the reaction in the body that is responsible for causing this feeling of euphoria. A long-held theory is that "runners high" is caused by endorphins that are generated by intensive exercise. These endorphins are neurotransmitters that act by binding to the same cell receptors as drugs like morphine or heroin. In this manner they act as natural pain killers and mood enhancers.
Exercise also increases levels of other neurotransmitters that impact mood. In addition exercise causes the production of endocannabinoids. These compounds are related to cannabis, better known as marijuana, and can be thought of as a natural marijuana generated by your own body when you exercise. In other words you can do something that is totally legal and healthy with the added benefit that you can get high naturally.
There is no agreement regarding how intense you must exercise to activate the pleasure reward center in the brain. In fact some researchers suggest that only moderate exercise boosts endocannabinoids. It is also important to point out that not everyone who exercises, no matter how hard they work out experience this natural high.
