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Many people have experienced reductions in stress, pain, and anxiety, and sometimes even euphoria, after exercising. What is behind this so-called “runner’s high”? New research on the neuroscience of exercise may surprise you.
The “runner’s high” has long been attributed to endorphins. These are chemicals that are naturally produced in the body of humans and other animals after exercise and in response to pain or stress.
However, new research from my laboratory summarizes nearly two decades of work on the subject. We found that exercise reliably increases levels of the body’s own endocannabinoids – the molecules that maintain balance in the brain and body – a process known as “homeostasis”. This natural chemical boost may better explain some of the beneficial effects of exercise on the brain and body.
I’m a neuroscientist at Wayne State University School of Medicine. My laboratory studies brain development and mental health, as well as the role of the endocannabinoid system in stress regulation and anxiety disorders in children and adolescents.
This research has implications for anyone who exercise for the purpose of stress reduction and should serve as a motivator for those who do not exercise regularly.
Health benefits of exercise
Several decades of research have shown that exercise is beneficial for physical health. These studies find a consistent association between varying levels of physical activity and reduced risk of premature death and dozens of chronic health conditions, including diabetes, high blood pressure, cancer, and heart disease.
From the Dana Foundation: “How Exercise Affects the Brain”
Scientists have also shown that exercise increases blood levels of endorphins, one of the body’s natural opioids. Opioids are chemicals that work in the brain and have a variety of effects, including pain relief. Some early research in the 1980s contributed to the long-held belief that this release of endorphins was related to the euphoric feeling known as runner’s high.
Scientists, however, have long questioned the role of endorphins in runners feeling elated, in part because endorphins cannot cross the blood-brain barrier into the brain, which protects the brain from toxins and pathogens. So endorphins are probably not the primary reason exercise has positive effects on mood and mental state.
At this point, our research and that of others point to the role of the natural cannabinoid versions of our bodies called endocannabinoids.
The surprising role of endocannabinoids
You may be familiar with cannabinoids like tetrahydrocannabinol – better known as THC – the psychoactive compound in cannabis (derived from the Cannabis sativa L. plant) that gets people high. Or, you may have heard of cannabidiol, commonly known as CBD, a cannabis extract found in some foods, medicines, oils, and many other products.
However, many people do not realize that people also make their own versions of these chemicals called endocannabinoids. These are tiny molecules made up of lipids – or fats – that circulate in the brain and body; “Endo” refers to those that are produced in the body and not from a plant or laboratory.
Endocannabinoids act on cannabinoid receptors throughout the brain and body. They produce a variety of effects, including pain relief, reducing anxiety and stress, and improving learning and memory. They also affect hunger, inflammation, and immune functions. Endocannabinoid levels can be affected by food, time of day, exercise, obesity, injury, inflammation, and stress.
It’s worth noting that one shouldn’t be tempted to give up running or cycling and instead resort to smoking or ingesting cannabis. Endocannabinoids lack the unwanted effects that come with a high, such as: B. Mental impairment.
Understand runner’s high
Human and animal studies suggest endocannabinoids – not endorphins – as the star players in runner’s high.
These elegant studies show that even when opioid receptors are blocked – in one example by a drug called naltrexone – people still experience euphoria and less pain and anxiety after exercising. On the other hand, the studies showed that blocking the effects of cannabinoid receptors reduced the beneficial effects of exercise on euphoria, pain, and anxiety.
While several studies have shown that exercise increases levels of endocannabinoids in the blood, some have reported inconsistent results or that different endocannabinoids have different effects. We also don’t yet know if all types of exercise like cycling, running, or resistance exercises like weight lifting produce similar results. And it’s an open question whether people with and without pre-existing conditions like depression, PTSD, or fibromyalgia experience the same endocannabinoid boosts.
To answer these questions, Shreya Desai, a student in my lab, led a systematic review and meta-analysis of 33 published studies on the impact of exercise on endocannabinoid levels. We compared the effects of an “acute” exercise session – such as a 30-minute run or cycle – with the effects of “chronic” programs such as a 10-week running or weight lifting program. We separated them because different levels and patterns of exercise can have very different effects on the endocannabinoid response.
We found that acute exercise increased endocannabinoid levels across all studies. The effects for a chemical messenger substance called anandamide – the so-called “happiness” molecule, which was named because of its positive effects on mood, among other things, were the most consistent.
Interestingly, we observed this exercise-related increase in endocannabinoids in different types of exercise, including running, swimming, and weight lifting, and in people with and without pre-existing medical conditions. Although few studies looked at the intensity and duration of exercise, it appears that moderate exercise intensities – like cycling or running – are more effective than lower intensity exercises – like slow walking or low incline – when it comes to increasing endocannabinoid levels. This suggests that it is important to keep your heart rate elevated for at least 30 minutes – i.e.
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There are still many questions about the connections between endocannabinoids and the beneficial effects of exercise. For example, we didn’t see consistent effects on how a chronic exercise program, like a six-week cycling program, might affect endocannabinoid levels at rest. Likewise, it is not yet clear what the minimum amount of exercise is to get a boost in endocannabinoids and how long these compounds will remain elevated after acute exercise.
Despite these open questions, these results bring researchers one step closer to understanding the benefits of exercise for the brain and body. And they are an important motivator for taking time to exercise in the hustle and bustle of the holidays.
Dr. Marusak is funded in part by the National Institutes of Mental Health (K01MH119241).
This article was republished by The Conversation under a Creative Commons license.
The holidays are a time when people like to indulge themselves a bit, but you don’t want to overdo it either. Try to make small changes in your daily life to compensate for the extra calories you may be consuming.
For example, skip the cheese on your sandwich or spend your lunch break strolling the neighborhood so you don’t have to turn down your favorite vacation treats.
The Christmas season comes with family visits, trips, get-togethers, and other time-consuming activities that can get in the way of daily exercise.
Instead of skipping them, create a schedule for the next few months that includes all of your commitments and then write down your workouts like any other appointment. That way you won’t be tempted to skip them.
If you are unsure about finding healthy choices at a holiday gathering, offer to bring a tasty, healthy dish that you love and that others like, too.
Usually the offering to bring something makes menu planning easier for the host, and you can rest assured that a nutritious option will be available when you meet.
Party foods like french fries and salsa, cheese and crackers, and store-bought cookies are foods you can find year round. Instead of filling up on these foods, treat yourself to treats once a year like your mother-in-law’s sweet potato casserole or some beautifully decorated homemade Christmas cookies.
At vacation gatherings, it’s easy to feast on baked goods, sweets, and french fries. Instead, take a handful of mixed nuts and slowly snack. Nuts are replete with healthy fats and are very filling.
Holiday meals typically include many vegetable dishes. Unless they’re swimming in butter or topped with marshmallows, load your plate with vegetables first. Once your plate is filled with vegetables, add other options. Basically, eat the healthiest foods first, then nibble on the goodies.
Before heading to the mall for your Christmas shopping, grab your sneakers for an early morning stroll. Many malls open their doors a few hours before stores open so you can work out your day before you shop until you drop.