The Runner’s High Is More Cannabinoid Than We Realized

The Runner’s High Is More Cannabinoid Than We Realized

For decades, exercise euphoria was largely explained through endorphins. Research into anandamide, 2-AG and the endocannabinoid system is revealing a much bigger story about what happens inside us when we run, surf, cycle or train.

Most people have experienced some version of it. You begin a run, surf, ride or long training session feeling normal, sometimes even uncomfortable, and somewhere further into the effort the experience changes. Your body is still working, your heart rate is elevated and the physical load has not disappeared, but your perception of it begins to shift. Pain can feel less intrusive, anxiety can drop, your thoughts can become quieter and movement can begin to feel unusually rewarding.

For decades, we had an easy explanation for that feeling: endorphins. The term “endorphin rush” became so embedded in popular culture that it was almost treated as settled science. Exercise releases endorphins, endorphins make you feel good, therefore the runner’s high must be an endorphin high.

The reality is considerably more interesting. Research over the past two decades has increasingly implicated the endocannabinoid system, the same biological network that THC and other compounds from cannabis interact with. Human studies have shown that sustained exercise can raise concentrations of naturally produced cannabinoids such as anandamide and 2-arachidonoylglycerol, or 2-AG. More importantly, experiments blocking opioid receptors suggest that some of the defining features of a runner’s high can still occur even when normal opioid signalling is disrupted.

That does not mean endorphins have suddenly become irrelevant. Exercise affects multiple neurochemical systems simultaneously, and endogenous opioids can still contribute to pain modulation and other responses. What the newer research challenges is the idea that endorphins alone explain the experience. A more accurate description is that exercise changes a network of chemical signals, with the endocannabinoid system appearing to play a much more important role than most people outside neuroscience realise.

The cannabis system was already inside us

This is where the subject becomes especially relevant to cannabis culture.

The endocannabinoid system is not something cannabis puts into the human body. It is an existing signalling system composed broadly of cannabinoid receptors, naturally produced molecules called endocannabinoids, and enzymes that produce and break those molecules down.

Two of the most researched endocannabinoids are anandamide, or AEA, and 2-AG. Anandamide can interact with CB1 cannabinoid receptors, which are abundant throughout areas of the nervous system involved in functions including reward, emotion, memory and pain processing.

THC is able to affect us partly because its molecular structure allows it to activate CB1 receptors. In other words, those receptors did not evolve because humans eventually discovered cannabis. Cannabis happens to contain compounds capable of interacting with biological machinery that was already operating inside us.

One of the earliest important human exercise studies demonstrated this in 2003. Trained participants ran or cycled for 50 minutes at approximately 70–80% of maximum heart rate, and researchers found evidence of increased endocannabinoid activity. That helped introduce an alternative explanation for some of the analgesia and psychological changes associated with exercise.

Since then, the evidence has expanded considerably. A systematic review covering 33 studies and 57 samples found that roughly three quarters of the samples measuring anandamide showed a significant increase following acute exercise. Its meta-analysis also found overall increases in both anandamide and 2-AG, although responses differed substantially depending on factors including exercise intensity, fitness level and when measurements were taken.

That variability is important because the ECS should not be thought of as a switch that exercise simply turns on. It is a constantly operating regulatory network whose activity changes according to what the body is experiencing.

What the runner’s-high experiment actually showed

One of the clearest human experiments arrived in 2021 and directly challenged the traditional endorphin explanation.

Researchers had 63 participants undertake moderate-intensity treadmill running and compared the results with walking. Running produced increased euphoria, decreased anxiety and elevated concentrations of anandamide and 2-AG.

The clever part of the experiment was the use of naltrexone, a drug that blocks opioid receptors. If the psychological runner’s high depended on opioid signalling, blocking those receptors should have prevented or substantially reduced the response.

It did not. Participants still experienced increased euphoria and reduced anxiety after running despite opioid blockade, while endocannabinoid levels also increased. The researchers therefore concluded that these central features of the human runner’s high did not depend on opioid signalling and that endocannabinoids were strong candidates for explaining the effect.

That result is much more meaningful than simply observing that a chemical increases after exercise. It separates two systems that had previously been difficult to disentangle and shows why saying the runner’s high is purely an endorphin phenomenon no longer reflects the evidence.

It still would not be scientifically accurate to say every feeling after exercise is entirely caused by cannabinoids. Exercise influences dopamine, noradrenaline, serotonin, endogenous opioids, neurotrophic factors and numerous metabolic signals alongside the ECS. What has changed is our understanding of how important cannabinoid signalling may be within that larger response.

Why anandamide keeps appearing in the research

Anandamide is particularly interesting because researchers repeatedly see it rise during or after aerobic activity.

Studies have reported increases following running and cycling, while research comparing self-selected and prescribed exercise found increased anandamide and 2-AG under both conditions. More recent outdoor-running research has also found increases in mood alongside elevated anandamide and 2-AG following a 60-minute run.

This does not mean the more intensely you train, the more cannabinoid activity you will necessarily create. Exercise responses depend on intensity, duration, fitness and individual biology. Some studies suggest that particular moderate-to-vigorous aerobic workloads may produce stronger endocannabinoid responses than very light activity, while other work shows that even lower-intensity exercise can alter endocannabinoid dynamics. The science is still developing rather than pointing to a single magical heart-rate number.

That makes real-world activities particularly interesting. Running is easy to study because researchers can control speed and duration on a treadmill, but humans do not only exercise on treadmills. Surfing combines paddling, bursts of intense effort, anticipation, cold exposure, balance and periods of recovery. Cycling can produce long periods of sustained aerobic work. Hiking combines prolonged locomotion with changes in terrain and elevation. Swimming, rowing and many forms of training can keep cardiovascular demand elevated for significant periods.

We cannot automatically claim that every enjoyable outdoor sport produces the same biochemical response as a controlled treadmill run. However, the broader exercise literature gives us good reason to investigate these experiences through the endocannabinoid system rather than treating every post-exercise change in mood as an undefined “endorphin rush.”

The bigger question is what the ECS is doing when cannabis isn’t involved

For cannabis culture, this may be the most interesting part of the entire story.

We generally encounter the endocannabinoid system through cannabis. Someone consumes THC, THC activates cannabinoid receptors, and we discuss the resulting change in perception, appetite, mood or physical sensation. That naturally makes the ECS sound like a system primarily concerned with cannabis.

Biologically, the relationship runs in the opposite direction. The ECS is involved in ordinary physiology whether someone uses cannabis or has never touched it. Research has connected endocannabinoid signalling with areas including stress regulation, pain processing, appetite and metabolism, emotional behaviour, cognition and reward. Physical activity is another influence capable of modifying that signalling.

So asking how much we “use” the endocannabinoid system outside cannabis needs a slight adjustment. We do not activate it occasionally and then shut it off again. We are using it continuously. Exercise is better understood as one circumstance capable of changing the concentrations of certain endocannabinoids and altering signalling within a system already working in the background.

That distinction opens up a much broader way of thinking about cannabinoids. When someone experiences stress, eats, exercises, recovers, processes pain or adapts emotionally to an environment, the ECS may be participating alongside many other biological systems. Cannabis introduces external cannabinoids into that existing network rather than creating cannabinoid activity from nothing.

This also helps explain why cannabis can influence such apparently unrelated experiences. Hunger, memory, emotional state, pain and reward may seem like separate categories, but cannabinoid receptors and endocannabinoid signalling intersect with regulatory pathways involved across many of them.

Cannabis and exercise are not producing the same “high”

There is an important line to draw here because the similarities can easily be exaggerated.

A rise in anandamide during a run is not equivalent to inhaling THC. Anandamide and THC have different pharmacological behaviour, different concentrations and different durations of action. The overall chemical environment of exercise is also dramatically more complicated than the activation of a single receptor.

Blood measurements create another limitation. Researchers can measure circulating anandamide and 2-AG relatively easily, but a higher concentration in blood does not automatically tell us exactly what is happening at every cannabinoid receptor inside the brain.

This is why the strongest argument is not that exercise is somehow “natural weed.” That would reduce fascinating science to an inaccurate slogan. The more important point is that two very different experiences can intersect with parts of the same ancient biological signalling network.

Cannabis is therefore better understood as interacting with an existing human language.

Exercise gives us an opportunity to watch that language change without administering an external cannabinoid.

Why would exercise produce this response at all?

There is also an evolutionary question underneath the research.

Endurance movement is expensive. Running for extended periods consumes energy and exposes an animal to discomfort, fatigue and potentially injury. Humans nevertheless evolved an unusual capacity for sustained locomotion compared with many species.

Researchers have proposed that rewarding neurochemical responses may have helped make prolonged movement more tolerable and reinforcing. One study comparing humans, dogs and ferrets found increased endocannabinoid signalling after endurance exercise in humans and dogs—both species adapted for sustained locomotion—but not the same response in ferrets.

That does not prove the runner’s high evolved specifically to make our ancestors enjoy endurance exercise, but it gives the theory an intriguing biological basis. Reducing discomfort, modifying anxiety and providing a sense of reward during sustained physical activity could plausibly make an organism more willing to continue moving when movement matters.

Viewed this way, the runner’s high becomes more than a fitness curiosity. It may provide a window into how human movement, motivation and cannabinoid signalling became intertwined.

A much larger cannabinoid conversation

Cannabis culture spends enormous amounts of time discussing cannabinoids produced by the plant, particularly THC and CBD. Comparatively little attention is given to the cannabinoids humans produce themselves and the circumstances that alter them.

Exercise research shows why that deserves to change.

The evidence does not tell us that endorphins are meaningless, that every sport creates a runner’s high, or that every pleasant feeling during exercise comes from anandamide. What it does show is that the familiar explanation of exercise euphoria as nothing more than an endorphin rush is increasingly difficult to defend.

Human beings possess an active cannabinoid signalling system. Sustained physical activity can measurably alter it. Those changes occur alongside shifts in mood, anxiety and pain perception, while opioid blockade does not eliminate some of the defining psychological features associated with the runner’s high. Taken together, that places the endocannabinoid system much closer to the centre of the story than popular understanding has historically allowed.

For cannabis, that changes the perspective completely. Instead of viewing the ECS primarily as the mechanism through which a plant gets us high, it makes more sense to view cannabis as one outside influence capable of entering a regulatory system that is already responding to our behaviour, our environment and our physical state.

Running simply gives us one of the clearest examples. The more interesting question moving forward is how much of what humans experience through movement, stress, recovery, reward and physical challenge is being influenced by cannabinoid signalling before cannabis ever enters the equation.

ARTICLE BY: WT Bridger