The Science Behind the “Runner’s High”
If you’ve ever finished a long run feeling unexpectedly euphoric, calm, or even invincible, you’ve likely experienced what’s known as the “runner’s high.” It’s a term tossed around often in running circles, but what actually causes it? Is it just a myth, or is there real science behind that post-run bliss?
More Than Just Endorphins
For decades, scientists believed endorphins were the sole reason for the runner’s high. Endorphins are natural painkillers produced by the body in response to stress or discomfort. They’re chemically similar to morphine and can dull pain while producing a sense of well-being. During long or intense exercise, the body releases a flood of endorphins—so it made sense they were the cause.
But there’s a catch: endorphins can’t cross the blood-brain barrier easily. That means even though your body is pumping them out during exercise, they may not directly affect your brain in the way we assumed. So while endorphins contribute, they’re not the full story.
Enter Endocannabinoids
Recent research points to another group of chemicals—endocannabinoids—as the real driver behind the runner’s high. These are naturally occurring compounds in the body that are similar to the active ingredients in cannabis. One in particular, called anandamide, increases in the bloodstream during aerobic exercise.
Unlike endorphins, endocannabinoids can cross the blood-brain barrier. When they do, they interact with the same brain receptors affected by THC (the psychoactive compound in marijuana), creating a sense of calm, reduced anxiety, and mild euphoria. This is what makes that euphoric, relaxed state after a good run feel so mentally rewarding.
Your Brain on a Long Run
The runner’s high isn’t just a feel-good bonus—it’s tied to how our bodies and brains evolved. Humans are built for endurance running. Thousands of years ago, our ancestors hunted by chasing prey over long distances until it was exhausted. A brain reward system that kicks in after prolonged effort makes sense from a survival standpoint. It helped encourage persistence, even when energy was running low.
Modern neuroscience supports this. Long, steady aerobic exercise reduces activity in the amygdala, the part of the brain linked to stress and fear. It also increases blood flow to the prefrontal cortex, which helps regulate mood and decision-making. Over time, regular exercise can rewire the brain to be more resilient to stress and more prone to positive mood states.
Not Everyone Feels It the Same Way
Not all runners experience a runner’s high, and it doesn’t happen every time. Factors like intensity, duration, fitness level, and even your mindset going into the workout can affect it. Generally, the best chance to trigger it is during moderate to long sessions of steady cardio—usually lasting 30 minutes or more.
Conclusion
The runner’s high is real, and it’s more complex than we once thought. While endorphins play a role, endocannabinoids like anandamide are the real chemical stars. This natural high isn’t just about feeling good—it’s a glimpse into how deeply connected our brains are to movement. Running doesn’t just train your body; it rewires your mind.
