A new study reveals what causes the euphoric feeling after a workout known as a “runner’s high.” Most prior research attributed this feeling to a flood of endorphins released during exercise. In addition to being produced after a workout, pain or stress also trigger the release of endorphins. However, a new study on the neuroscience of exercise found a different source of runner’s high that might surprise you.
A new study published in the journal Cannabis and Cannabinoid Research found that exercise consistently increases levels of endocannabinoids. These molecules help maintain balance in the body and mind, otherwise known as homeostasis. The natural release of this chemical may explain the benefits of exercise better than endorphins.
Dr. Hilary A. Marusak, a neuroscientist at the Wayne State University School of Medicine, led the study. Her lab performs research on brain development, mental health, and how the endocannabinoid system can help regulate stress and anxiety disorders. She says the research has implications for those who exercise to lower stress and should help motivate those who don’t exercise regularly.
Exercise Offers Numerous Benefits and Boosts “Feel-Good” Hormones
Mounting evidence proves that exercise can enhance physical health and lower the risk of premature death in addition to chronic health problems such as cancer, heart disease, and high blood pressure.
Exercise also offers many mental health benefits, such as reducing symptoms of anxiety, depression, and neurodegenerative diseases such as Parkinson’s. Regular exercise can also improve cognitive performance, mood, self-esteem, and stress levels.
Prior to the study by Dr. Marusak, researchers didn’t know what caused these boosts in mental health. However, it’s clear that exercise affects the brain in several ways, such as increasing metabolism and blood flow. It also promotes the production of new brain cells and increases several chemicals in the brain.
Some of these chemicals are called neurotrophic factors, such as brain-derived neurotrophic factors. BDNF plays an important role in neuroplasticity, or the brain’s ability to modify and adapt both structure and function throughout life.
The role of endorphins in a runner’s high
Scientists also discovered that exercise increases endorphins – a natural opioid – in the blood. Opioids not only help relieve pain but reduce stress as well. Some studies in the 1980s attributed this endorphin release to the feeling of bliss called the “runner’s high.”
However, scientists have recently questioned this early research since endorphins cannot cross the blood-brain barrier, which prevents toxins and pathogens from entering the brain. Because of this, endorphins likely don’t trigger the positive effects on mood and mental state following an intense workout.
Dr. Marusak’s research discovered that our body’s naturally occurring cannabinoids, called endocannabinoids, may cause the “runner’s high.” These minuscule molecules made of lipids, or fats, circulate throughout the brain and body. Endocannabinoids bind to various cannabinoid receptors throughout our brains and bodies and can help relieve pain, reduce anxiety, and improve learning and memory. They also impact appetite, inflammation, and the immune system.
Of course, cannabis offers similar benefits but comes with side effects such as cognitive impairment. Due to this, Dr. Marusak suggests exercising instead of ingesting cannabis to induce euphoria without actually getting high.
Researchers Finally Understand the Exact Cause of a “Runner’s High”
Previous human and animal studies point to endocannabinoids instead of endorphins as the driving mechanism behind a runner’s high. However, those studies didn’t show whether all types of exercise, not just running, produced these effects. Also, it’s unknown whether people with preexisting health conditions like PTSD, depression, and fibromyalgia experience boosts in endocannabinoids.
To find out more about how endocannabinoids influence the brain, undergraduate student Shreya Desai led a systematic review and meta-analysis of 33 previous studies on the subject. The analysis compared the impacts of short-term exercise sessions, such as running for 30 minutes, with long-term programs such as a 10-week weightlifting program.
What the scientists learned
They separated them into two groups since exercise of varying intensity may have different effects on endocannabinoids. The research found that acute, or short-term, exercise boosted endocannabinoid levels consistently across multiple studies. The team observed the greatest consistency in endocannabinoid boosts in one chemical messenger called anandamide – known as the “bliss” molecule.
They also noted this exercise-induced boost across many types of workouts, including swimming, weightlifting, and running. It also remained steady in individuals with and without preexisting conditions.
Finally, the analysis found that moderate-intensity exercise, such as cycling or running, boosted endocannabinoids more than low-intensity exercise. So, you’ll want to keep your heart rate elevated – or at about 70%-80% of maximum heart rate – for at least thirty minutes to experience the “runner’s high” feeling.
However, a few questions remain regarding how endocannabinoids affect exercise. For instance, the researchers didn’t observe consistent effects for how a long-term exercise program may impact resting endocannabinoid levels. Also, it’s unclear how long a person should exercise before they notice a boost in endocannabinoid levels. Finally, researchers aren’t sure how long the chemicals remain elevated after short-term exercise.