Runner's high
Another widely publicized effect of endorphin production is the so-called "runner's high", which is said to occur when strenuous exercise takes a person over a threshold that activates endorphin production. Endorphins are released during long, continuous workouts, when the level of intensity is between moderate and high, and breathing is difficult. This also corresponds with the time that muscles use up their stored glycogen and begin functioning with only oxygen. Workouts that are most likely to produce endorphins include running, swimming, cross-country skiing, long distance rowing, bicycling, weight lifting, aerobics, or playing a sport such as basketball, soccer, football.
However, some scientists question the mechanisms at work, their research possibly demonstrating the high comes from completing a challenge rather than as a result of exertion.[6] Studies in the early 1980s cast doubt on the relationship between endorphins and the runner's high. There were a couple of reasons for this doubt.
* The first was that when an antagonist (pharmacological agent that blocks the action for the substance under study) was infused (eg naloxone) or ingested (naltrexone) the same changes in mood state occurred that happened when the person exercised with no blocker.
* A second piece of evidence is much more simple. It turns out that scientists cannot make a runner's high occur in the lab with any certainty. This makes it very difficult to study, much less prove that endorphins cause the runners high.
In recent years, the connection between the "Runner's High" phenomenon and endorphins has been severed completely. A study in 2004 by Georgia Tech found that Runner's High was likely triggered by a release of another naturally produced body chemical, the endocannabinoid anandamide. Anandamide is similar to the active chemical THC in Marijuana. The body produces this chemical to deal with prolonged stress and pain from strenuous exercise, similar to the original theory attached to endorphins.
