The runner’s euphoria, during or after a physical effort, is not linked to endorphins but to endocannabinoids. These substances bind to the same receptors as cannabis.
On this autumn Sunday cooled by winter temperatures, courageous runners will put on their trainers. Some will drag their feet a little but others, driven by the pleasure, even the ecstasy, that the race gives them, will take great strides. A euphoria caused by endocannabinoids, substances produced by the body that have the same effect as cannabis, reveals a study published in Proceedings of the National Academy of Science (PNAS).
According to a popular belief, it is the endorphins which are responsible for the ecstasy of the runner, thanks to their analgesic properties. However, these hormones are too big to cross the blood-brain barrier, indicates researchers from the University of Hamburg and Heidelberg (Allemafne). This is why they tried to identify the molecules responsible for this phenomenon described by many joggers.
Less anxious and sensitive to pain
To do this, they placed wheels in the cages of around 30 mice. For 3 days, the mice were able to roam freely, traveling an average of 5.4 km per day. They then removed the wheel from half the group. After a final 5-hour run, the researchers studied the behavior, anxiety and pain levels of the mice.
In a context of stress, it appears that mice joggers are less anxious and stressed than others. In addition, by placing them on a hot plate, the researchers found that guinea pigs that ran reacted less quickly than other mice, reflecting a decrease in pain sensitivity.
Endorphins have no effect
To identify the substances potentially responsible for these effects, the researchers carried out blood tests. They then notice that the animals that ran have higher endocannabinoid levels than the mice that remained inactive. To make sure that these hormones produced by the body are involved, the researchers injected the mice with a drug that blocks the cannabinoid receptors. The smiling joggers no longer felt the ecstasy of the runner. They were also stressed and felt the same pain as everyone else.
In order to assess the role of endorphins, the researchers performed the same experiment by blocking their receptors. Results: The two groups of mice showed no difference, a sign that these hormones do not induce pleasure and the euphoria written by runners after the race. One myth falls, but another is born: running acts like cannabis.
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