Endorphins and the Runner's High

Man and woman enjoying endorphin release after exercise
Exercise can cause a release of endorphins. Peopleimages/Getty Images

Often referred to as the body's natural pain relievers, endorphins are biochemical substances your body makes. They have some of the same properties as opiates. Released into your body as a response to situations like pain or stress, endorphins help to reduce pain and can bring about feelings of euphoria, calm, relaxation, and well-being. Since strenuous exercise, especially running, can produce endorphins, sometimes these euphoric feelings are called the "runner's high."

How Endorphins Work

There are over 20 different kinds of endorphins. They are proteins that are produced by the pituitary gland and hypothalamus during exercise and in response to pain, excitement, and other stress stimuli. Acupuncture, chocolate, and hot peppers can also stimulate your body to produce endorphins.

In response to pain, endorphins are distributed throughout the nervous system, where they interact with opiate receptors to reduce the perception of pain. Plus, endorphins also make us feel happy, boost our immune systems, aid with memory, balance our appetites, contribute to the release of sex hormones, and help regulate our body temperature. So anytime we're laughing, stressed out, engaging in sexual activity, exercising, or in pain, endorphins are being released into our bloodstreams.


Endorphins were first discovered in the 1970s by two separate groups of independent investigators, both studying the brains of animals. Scientists John Hughes and Hans W. Kosterlitz from the University of Aberdeen in Scotland first identified and isolated endorphins from the brain of a pig. Simultaneously, Rabi Simantov and Solomon Snyder, both from the United States, identified endorphins in a calf brain. It was also discovered around this time that these endorphins in the human body, as well as the bodies of many animals, are capable of producing morphine-like effects.

The Painkilling Effect

The results of this varied research enabled neuroscientists to determine that the human brain contains endorphins, which the pituitary gland releases when the body is under stress or feeling pain. These endorphins interact with receptors to allow more dopamine to be released into the body, which reduces the overall perception of pain. The effects of this process are similar to the use of a drug such as morphine.

Thus, if an artificial painkiller such as morphine is introduced into your body, it has an effect on the naturally occurring endorphins. The painkiller occupies more of your brain’s pain receptors. Your body senses this, and in return, produces fewer naturally occurring pain reducers. However, when the artificial source is removed (the drug wears off), many pain receptors become empty. This causes a craving for endorphins, and this is how addiction can begin. But endorphins on their own are not dangerous or addictive.

The Runner’s High

For some people, running a long distance can cause a sense of euphoria that's comparable to the high you can get from drugs. The reported sensations of this runner’s high include feelings of extreme peace, a sensation of floating, bliss, euphoria, and increased pain tolerance.

This runner’s high has been credited to an increased level of endorphins in the brain, particularly in a small study first published in 2008. Though endorphins are consistently released to your body as you run and certainly increase in your bloodstream, research has since shown that they may be too big to move from your blood into your brain. So they may not actually be the chemical that's responsible for creating a runner's high.

According to a 2015 study on mice, what might be behind these feelings instead is a neurotransmitter called anandamide, an endocannabinoid that is released into your blood (along with endorphins) when you run. Since both chemicals are also released in mice when they run, the study was done with mice that ran on a wheel, using medications to block the effects of each chemical. When endorphins were blocked, there was no change in the symptoms of runner's high like calm, pain tolerance, and sedation. However, when they blocked anandamide, all the runner's high signs went away. Thus, the researchers found that the release of anandamide may be the key to the feelings behind a runner's high.

The bottom line: It may be a while before scientists figure out exactly which chemicals are responsible for a runner's high, but research increasingly points to endocannabinoids rather than endorphins.

Long-Term Benefits of Endorphins

Thanks to brain chemicals, if you're a habitual long-distance runner, your anxiety level is likely much lower than the average person's, and you may have less sensitivity to pain too. The neurotransmitters dopamine, serotonin, and norepinephrine are also boosted when you exercise, which can account for the good feeling many of us get when we're done with a workout.

If you're just getting started with running, you too can build up this level of calm, relaxation, pain tolerance, and feelings of well-being by consistently engaging in moderate to intense levels of exercise. In fact, it's often the reward of those good feelings we get after a long run, which seem to be heavily influenced by endocannabinoids like anandamide, that inspires us to do it again and again, despite the risk of injury and the time and energy running takes.

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