Ten thousand steps and more. Exercising is good for your health! This injunction proclaimed by many prevention campaigns is however easier said than done, the ability to play sports largely depends on motivation. But where does this motivation come from? It comes from a molecule, dopamine, which, during physical effort, is released in the striatum, an area of our brain involved in particular in impulses… and motivation. Dopamine, also called the happy hormone, is a neurotransmitter. That is to say, it transmits information between two neurons at contact areas called synapses. When received in large quantities by the receptor neuron, it is a pleasure signal. Since this pleasure is perceived during physical effort, the reward system is activated and pushes us to want to do sport again. Until then, we tell ourselves that nature is well done.
But we are not all equal when it comes to motivation. Why do some of us call ourselves “addicted” to sport when others struggle to put in the effort? This is what researchers from the University of Pennsylvania wanted to answer. by comparing physical performance within a cohort of mice. While they didn’t find a specific gene for physical strength, one result caught their attention. Mice for which the microbiota (all the beneficial bacteria colonizing our intestine) was suppressed showed poor sports performance compared to their congeners. By testing the effects of removing certain bacterial strains, they were able to identify that some of them, such as Eubacterium Where coprococcus, had a positive effect on motivation to exercise.
Lots of dopamine
But how do these bacteria manage to affect our physical performance? American researchers have shown that they stimulate the release of dopamine in the striatum during exercise. In fact, some bacteria release molecules with the barbaric name of N-oleoylethanolamide. These metabolites will be captured by sensory neurons that connect our gut to our brain (through the spinal cord). They will more specifically bind to small receptors present on the terminal intestinal part of neurons and thus promote their activation during sport. However, when they are active, sensory neurons inhibit the production of an enzyme called monoamine oxidase (MAO) in the striatum. This enzyme is responsible for the degradation of dopamine at the synapses. When the enzyme is absent, dopamine is maintained in sufficient quantity to induce a pleasure signal. By activating sensory neurons during exercise, bacteria guarantee the presence of a quantity significant amount of dopamine in the striatum, and therefore a feeling of pleasure that will subsequently motivate you to play sports.
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