Contrived from the Merriam Webster Dictionary, exercise is defined as the bodily exertion for the sake of developing and maintaining physical fitness. It is often synonymous with longevity and a healthy lifestyle. The activities can range from moderate to intensive activities such as walking or swimming but the benefits are still the same. Exercise controls weight, combats diseases, and altogether boosts self-confidence in a person. One specific result of strenuous exercise is a mood booster caused by the release of chemicals in the brain. But how do these processes come into play?
This process goes back to the beginning of humans and their behavior. Many professionals such as David A Raichlen, Ph.D., assistant professor of anthropology at Arizona University, infers that the runner’s high was a long-term effect of prehistoric humans travelling to find food as it provided motivation and a pain-killing effect to deal with the physical pain that came with these vigorous exercises.(1) Similar to the effect it has on humans in modern day, although running and more intensive exercises are not usually done for survival, the same production of these “happy chemicals” in your brain are produced.
What exactly are the “happy chemicals” produced during these strenuous exercises? When the body is involved in activities such as running, swimming, and cycling, it releases a chemical in your brain, called endorphins. Endorphins are released in the pituitary gland of the brain, in response to pain and stress, similar to morphine, it acts as an analgesic and sedative, diminishing your perception of pain. (2) Another alternative in releasing this chemical is laughter. Although the effect is different for every runner, the energizing and mood-boosting feelings that come from endorphins make the runner feel like they are on a high, hence the origin of the name.
Although endorphins have been commonly believed to be the main factor, recent studies have also come across a different chemical that is thought of to have a similar effect. Endocannabinoids, the naturally synthesized version of tetrahydrocannabinol (THC), is responsible for the buzz that Marijuana produces. (3) Endocannabinoids are a stress reliever and sustains calmness in the body. Researchers questioned the effects of endorphins after they realized that endorphins can’t pass through the blood-brain barrier, but a lipid-soluble endocannabinoid called anandamide—also found at high levels in people’s blood after running—can travel from the blood into the brain, where it can cause a high. (4) This finding led to countless inquiries on the process and many experiments to test out the theory.
At the University Medical Center Hamburg-Eppendorf, researchers investigated by setting up an experiment on mice running on exercise wheels. The researchers separated the mice into two groups: one group ran for five hours on the exercise wheels and the others stayed inactive. In every result, the group of mice that were active, showed less anxious behavior. When placed in a dark-light box test, researchers measured the frequency of the mice running from light areas to hide in the dark. The active mice also produced more pain tolerance, tested by putting the mice on hot plates and observing the reactions between both groups. Then, the researchers redid both experiments but genetically engineered the mice to have either endorphin or endocannabinoid antagonists and observed the results. In the mice given endorphin antagonists, there was insignificant changes, but the mice given endocannabinoid antagonists were still susceptible to pain and anxiety from running for five hours. (4) From this research, scientists concluded that endocannabinoids could have an influence in causing the runner’s high. As the conversation continues, the research from this experiment aids the idea of various causes that influences the effect it has on a runner’s brain.
Other researchers such as Cedric Bryant, Ph.D., chief science officer for the American Council on Exercise, has also refuted the claims of endorphins being the sole factor for the runner’s high. Like the previous researchers, Bryant understood that even when endorphins were blocked in a system, runners still experienced the high, leading him to believe in other causes, even straying from endocannabinoids and focusing on other neurotransmitters such as norepinephrine secretion, dopamine, and serotonin that tend to be produced in higher concentrations during exercise, as they also have shown to help reduce depression. (6) Bryant also believed that temperature could also play a factor in the high as there have been theories of temperature linked mechanisms that could indirectly affect mood during high-duration activities.
Although the source of the runner’s high is commonly argued, endocannabinoids and endorphins are currently the most researched factors of this process. As the analysis continues, the answer to this question will only become more complex as other factors will be put into play. But what has been proven, is the multitude of benefits that come from challenging your body in physical ways, no matter the mood.
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