Researchers from Germany may have found the real reason behind the "runner's high" sensation that many athletes and fitness enthusiasts experience.
Based on the results of their study, this feeling may actually be caused by a natural substance that replicates the effects of marijuana, Scientific American reported.
Those who enjoy running for long periods of time are familiar with the calmness and feeling of elation that they experience after the intense workout. Since the 1980s, scientists have attributed this sensation to the release of endorphins, also known as the natural painkillers of the body.
These are released by the body after rigorous exercise sessions and increase a person's tolerance to pain. Due to the natural functions of endorphins, scientists assumed that they are also responsible for producing the euphoric sensation by interacting with the brain's receptors.
However, other scientists noted that endorphins are actually made up of large molecules that are too big to enter the brain, which means they cannot be responsible for "runner's high."
Jumping off from this idea, the researchers from the University of Heidelberg in Germany set out to identify the real reason behind the post-exercise sensation. After a series of tests conducted on mice, they discovered that endocannabinoids may be the substances that produce the euphoric feeling.
The researchers explained that endocannabinoids are chemical substances produced naturally by the body. Their effect is similar to the cannabinoids found in marijuana, which is used as a psychoactive drug.
Unlike endorphins, endocannabinoids are small enough to enter the brain and interact with its receptors and produce various physiological effects such as calmness and higher tolerance for pain.
The research team was able to come up with this theory after observing two groups of mice. One group was made to run for five hours while the other set remained sedentary.
The two groups were then subjected to a test that involved using light to illuminate certain areas of a box. The researchers saw that the mice that ran were less anxious and were not affected by the light. The other group, however, darted away from the light and hid in the darker areas of the box.
The same experiment was then conducted on another set of mice but this time, they were given endorphin and endocannabinoid antagonist, or chemicals that prevent these substances from affecting the brain's receptors.
No significant changes were seen in the animals that were given endorphin antagonists. However, for those that received endcocannabinoid antagonists, they remained anxious and more sensitive to pain even though they ran for five hours.
These findings clearly show how endocannabinoids can affect the brain and produce "runner's high." However, since the tests were conducted on mice, it is not yet clear if these will produce the same results on humans, according to the Washington Post.
The findings of the researchers were detailed in a report published in the academic journal Proceedings of the National Academy of Sciences on October 5.
