In the past, endorphins have been the star of the show for the exercise-mood connection: a good sweat session will trigger the release of endorphins, which are neurochemicals produced in the pituitary gland that react with opiate receptors, thereby which means that they make you feel very good. Exercising also stimulates the production of serotonin and norphenylephrine, which are other neurotransmitters that induce happiness, well-being, and pleasure.
These mood-boosting stimuli would probably be enough to give you that post-yoga glow. But there is something even more going on.
Researchers have come to understand that when our muscles contract, they produce substances that are dispersed throughout the body. Some of these are chains of amino acids called myokines, and they can cross the blood-brain barrier, which means they can act on your brain. And when they get there, they improve brain function.
“Several myokines (irisin, hydroxybutyrate, etc.) have been shown to stimulate neuronal function and facilitate synapses, which is how neurons communicate with each other,” Mychael Vinicius Lourenco, PhD, assistant professor of neuroscience at the Federal University of Rio. de Janeiro, who co-authored a recent review of research on myokines and brain function, previously told Well+Good.
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That potentially includes “mediating the beneficial actions of physical exercise on the brain,” Lourenco and co-authors write in the review. As a potential example, helping with neural communication could mean that myokines are helping the feel-good messages sent by endorphins, serotonin, and norphenylephrine to be heard.
Beyond helping the brain do its job better, researchers also believe that myokines could be a bulwark against depression. This has led to the substances getting the name “molecules of hope.”
In 2016, physiotherapy and psychiatry researchers writing in the journal Physical therapy they were reviewing the research on the connection between exercise and depression. He referred to a 2014 study in mice in which mice with lower levels of a certain type of myokin showed less resilience under stress than mice with higher levels of myokin.
“After a significant amount of stress, the mice appeared to ‘lose hope,’ as evidenced by decreased survival efforts during forced swimming (an indicator of depression),” the authors write. “Taken together, these results suggest that the release of ‘molecules of hope’ from rodent skeletal muscles influences mood disorder symptoms.”
While we can’t necessarily extrapolate the findings from the mouse studies to humans, both species share an underlying biology that could cause myokines to work similarly. That is, these myokines could inhibit a neurotransmitter pathway that, when overactive, is linked to depression.
This was convincing enough for Stanford University psychologist Kelly McGonigal, author of the joy of movement, to take note of the study and popularize the term. The “molecules of hope,” McGonigal previously said on the Rich Roll podcast, could be like “an intravenous dose of hope.”
“It’s not just an endorphin rush,” McGonigal says on the podcast. “You go for a walk or run or lift weights and your muscles contract and secrete these proteins into your bloodstream. They travel to your brain, they cross the blood-brain barrier. And in your brain, they can act like an antidepressant. Like irisin (a myokine) it can make your brain more resistant to stress. They increase motivation. They help you learn from experience. And the only way to get these chemicals is by using your muscles.”
Even if research is still underway on how exercise improves mood and mental health, the link between exercise and well-being has never been clearer. Two recent meta-analyses on the effects of exercise in adults and children have found that it is an effective bulwark against depression.
With our emerging understanding of myokines and the undeniable benefits of exercise, there has never been a more compelling reason to take your medicine: a dose of movement.
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