You’ve probably heard of “runner’s high,” which you could call a thrill of elation that comes from your brain and muscles being on the same page after a good workout. It’s also referred to as an “endorphin rush,” which can arrive to flood your senses with varying degrees of pleasure and satisfaction.

Pride in a job well done (including exercise), eating hot peppers and watching your children discover nature can do something similar, but new science indicates that endorphins released with more exercise intensity, especially with high-intensity interval training (HIIT), can create a powerful response in your brain that can affect every area of your body. Shape Magazine explains:

“High-intensity interval training describes any workout that alternates between intense bursts of activity and fixed periods of less-intense activity or even complete rest. For example, a good starter workout is running as fast as you can for 1 minute and then walking for 2 minutes. Repeat that 3-minute interval five times for a 15-minute, fat-blasting workout.”1

The feeling may involve a combination of an increase in energy expenditure that, rather than making you feel tired and spent, does just the opposite. Endorphins have actually been called your body’s natural opiate. How Stuff Works explains some of the early science done to discover the source of this response:

“In the early 1970s, researchers were studying how the brain is affected by opiates, such as heroin or morphine. They found that opiates interact with specialized receptors in cells that are primarily massed in the brain and spinal cord. When opiates enter these receptors, they hinder or block the cell’s transmission of pain signals.

But why, wondered the scientists studying this phenomenon, would these specialized receptors exist in the first place? The most plausible answer was that opioid receptors exist due to the presence of an opiate-like substance produced naturally in the body.”2

Study: Endorphins in Your Brain Depend on Exercise Intensity

Endorphins serve a few other purposes, though, being neurochemicals produced in the hypothalamus and pituitary gland areas of your brain, considered natural painkillers that are similar in structure to morphine. They even activate opioid receptors in your brain to help minimize pain. Science Daily describes endorphins as “peptides produced by the brain that bind to the brain’s opiate receptors, reducing the perception of pain and triggering feelings of euphoria.”3

Endorphins that kick in during exercise impact you physically, mentally, emotionally and certainly physiologically. But the latest research indicates it’s all about the intensity of your workout. Endorphin release, known throughout the study as “central opioidergic mechanisms,” was approached in the study with the knowledge that it may modify the positive effects of physical exercise such as mood elevation and stress reduction.

Scientists monitored the opioid receptors engaged by 22 “healthy, recreationally active males,” all ranging from 21 to 36 years old, using positron emission tomography (PET) during acute physical exercise. Endorphin release was measured repeatedly throughout three separate days in three ways:

  • After a 60-minute aerobic moderate-intensity exercise session
  • After an HIIT session
  • After rest

Also measured were the participants’ moods following their exercise sessions. The study was conducted at Turku PET Centre at the University of Turku in Finland and reported in the journal Neuropsychopharmacology.4

According to current physical activity guidelines set forth by the Centers for Disease Control and Prevention (CDC), from the U.S. Department of Health and Human Services,5 if adults want to improve or maintain physical health, adults should either engage in a minimum of 150 minutes of moderate-intensity aerobic activity a week, or 75 minutes of vigorous-intensity aerobic activity in the same period.

Are Endorphins Different Depending on Moderate Versus Intense Exercise?

As already acknowledged, it’s clear the results go far beyond the physical, extend to a person’s mood and can even help alleviate anxiety and depression as a direct result of the endorphins being activated by exercise.

Study co-author Tiina Saanijoki said one reason the study was significant was because although scientists already knew the level of plasma β-endorphin or beta-endorphin can often elevate during intense exercise, research hadn’t yet established whether there might be a link between circulating endorphin concentrations and mood.

On the question of whether endorphins can be more or less beneficial depending on whether the exercise is moderate or more intense, the researchers had their 22 male study subjects engage in the aforementioned types of exercise mentioned above, as well as rest, measuring their moods and endorphins using PET involving a radioactive compound that binds to the brain’s opioid receptors. According to Medical News Today:

“The researchers found that HIIT led to a significant rise in the release of endorphins in the men. This occurred in areas of the brain associated with pain, reward, and emotion, including the thalamus, insula, orbitofrontal cortex, hippocampus, and anterior cingulate cortex. Furthermore, the team found that HIIT caused negative feelings in the men, which was also associated with an increase in endorphin release.”6

Saanijoki explained that high exercise intensities release endorphins that seem to be associated with increased negative feelings and pain, and that endorphin release may be necessary to counteract how emotionally and physically challenging such exercise is. The problem is that negative feelings about HIIT may discourage further exercise, she said.

However, the more moderate aerobic exercise triggered, as Medical News Today described it, feelings of pleasure and euphoria, which further helped the researchers in their understanding of how endorphins work. Neuroscience News described the study results this way:

“HIIT leads to endorphin release in the brain, which might alleviate the physical and emotional stress caused by the high-intensity exercise. A less demanding, traditional one-hour aerobic exercise does not cause similar endorphin release. HIIT significantly increased the release of endorphins and other opioid peptides in the brain areas controlling pain and emotions.

In addition, HIIT induced negative feelings in the test subjects, which was associated with higher endorphin release. Although one-hour aerobic exercise did not induce significant release of endorphins, it increased pleasurable feelings and euphoria, which correlated with endorphin release.”7

Studies: What High-Intensity Exercise Can Do for You

The overall take-away from the study is that the endorphin release that exercise induces could be an important factor in motivation, as well as maintaining a regimen of regular exercise. In addition, knowing that such “euphoria” can be expected may even be something reluctant workout warriors can take into account when deciding which exercise routines to incorporate.

To reiterate what HIIT can do for you, consider this: One minute of strenuous activity in a 10-minute exercise session can be as effective as working out for 45 minutes at a moderate pace. That also means that 12 minutes of extreme exertion gets you more results than five hours of moderate exercise. It will also affect your overall health dramatically.

One of the most incredible aspects of HIIT is that such exertion improves glucose tolerance more than any other type of exercise, can burn from 6 percent to 15 percent more calories, produces immediate changes in your DNA and also triggers production of human growth hormone and mitochondrial biogenesis, which could even help you live longer.8

Oncology Nurse Advisor revealed that HIIT can benefit colorectal cancer survivors, because when people put off exercise that would benefit their cardiorespiratory fitness, it impacts their health more than they realize. In fact, this omission may lower survival rates in people who’ve received anticancer therapy. A study showed that survivors who engaged in HIIT or even moderate exercise experienced improved peak oxygen consumption.9

And the same website noted that HIIT can help heart transplant patients who are stabilized gain stamina, increase their exercise capacity and improve their blood pressure more than moderate intensity exercise, plus it’s is safe and more efficient in improving exercise capacity for patients with different types of heart disease.10

Even If It’s Not HIIT, Regular Exercise Improves Your Brain, Study Says

One reason this is especially crucial is that it comes at a time when Alzheimer’s and other forms of dementia are on a critical rise. In fact, the Alzheimer’s Association says around 5.5 million Americans of all ages have Alzheimer’s disease and about 200,000 of them are under the age of 65.11 Here are a few more benefits that exercise offers: It can improve your skin, slow down the aging process, help you recover faster from chronic disease and, in regard to weight loss, can shrink fat cells.

According to a Harvard study,12 besides reducing your risk of developing “the big three” serious health complications — heart disease, stroke and diabetes — exercising on a regular basis can lower your blood pressure, lower your weight and even prevent depression. But in relation to your brain, changes can be made that will improve your memory and thinking skills, and alleviate brain fog.

Between these advantages and getting happier from the release of pleasurable endorphins, exercise is a no-brainer — or rather a routine you could develop to make sure yours is getting sharper every day.