The euphoria that one gets after a serious jogging session, also known as the runner's high, is comparable to a real high after smoking cannabis. This is shown by a research on mice by German scientists of the Heidelberg University.
Since the 80s, it has been believed that endorphins are responsible for the joyful feeling one can experience after working out. The endorphins are thought to take away the pain and give the athlete a feeling of euphoria. According to the German scientists, it may well be that this experience is not caused by the release of endorphins but by endocannabinoids. This is a substance that is synthesized by the body, but that can also be found in cannabis.
The researchers concluded this after letting mice run in an exercise wheel. It turned out that the mice had a far larger endocannabinoid-content in their brain than those that hadn't walked. They became less fearful and were more resistant to pain. When the scientists blocked their endocannabinoids and let them run in the exercise wheel once more, the mice remained fearful and were less resistant to pain.
Although the experiment was only tested on mice, the scientists believe that they have found a breakthrough. "It's the first time that we have shown that the endocannabinoid receptors are part of the crucial aspects of the runners high", as stated in the scientific journal Proceedings of the National Academy of Sciences.