Are High-Intensity Workouts Messing With Your Cortisol?

For this article, Outside Run contributor Danielle Zickl spoke to two endocrinologists to find out whether your high-intensity runs are actually messing with your hormones.

If you’ve scrolled through social media lately, you’ve probably seen wellness influencers claim high-intensity exercise increases cortisol, the infamous “stress hormone” that, in excess amounts, can lead to fatigue, weight gain, trouble sleeping, high blood pressure, and elevated blood sugar.

Many influencers say to switch to a no-stress, low-sweat regimen. And while low-intensity exercises such as Pilates, treadmill walking, or yoga are valid ways to work out—and serve as excellent cross-training activities for runners—HIIT workouts (like hill repeats, sprint intervals, and tempo runs) are key if you’re training for a race or looking to build speed and power.

But are high-intensity runs actually messing with your hormones, or is the wellness side of the internet spreading misinformation? We’re here to separate fact from fiction.

More About Cortisol’s Role in Your Body

Cortisol is a hormone made by your adrenal glands, which are located on top of your kidneys and are part of your body’s endocrine system.

“Cortisol helps regulate metabolism, blood pressure, and the immune response, and it makes energy available when the body is under stress—including during exercise,” says Dr. Aysegul Eren, M.D., endocrinologist and medical director of the Adrenal Program at The Ohio State University Wexner Medical Center.

This hormone rises when your body faces increased physical or metabolic demand, such as exercise, illness, fasting, low blood sugar, or psychological stress, Eren explains. During exercise, cortisol naturally spikes as a way to provide energy to your body so it can perform. Viewed through that lens, cortisol is an important part of your body’s response to exercise and your ability to complete workouts.

The Connection Between Cortisol and HIIT Workouts

“Higher-intensity exercise reliably causes a temporary cortisol rise, generally related to exercise intensity,” Eren says. “This is normal physiology, not something harmful to prevent.”

How long cortisol remains elevated depends on the stressor, according to Dr. Feyza Erenler, M.D., an endocrinologist at Tufts Medical Center. It may be minutes to hours for a brief stimulus like exercise, she explains.

A 2021 meta-analysis of 10 studies on HIIT, published in the Scandinavian Journal of Medicine & Science in Sports, found that cortisol increased immediately after exercise, often fell below baseline about two hours later, and returned to baseline within 24 hours.

“There’s no evidence that a specific number of HIIT sessions causes chronically high cortisol,” Eren says. “The more relevant concern is overtraining—chronic training without adequate recovery—which can lead to persistent underperformance. ‘Too much’ is individual, depending on training load, sleep, nutrition, recovery, and other stressors.”

In fact, research shows physical activity can actually lead to lower cortisol levels. A 2026 study in the Journal of Sport and Health Science found that those who did 150 minutes of moderate- to vigorous-intensity aerobic exercise (50 to 85% of their max heart rate) every week for a year saw a reduction in long-term cortisol levels.

Signs of High Cortisol

Symptoms frequently attributed to “high cortisol,” such as fatigue, poor sleep, anxiety, or difficulty losing weight, don’t indicate that a person has high cortisol, according to Erenler. “These symptoms are extremely common and nonspecific and can occur for many different reasons,” she says.

Signs of true high cortisol—not the brief, self-resolving spike during exercise—include bruising, muscle weakness (particularly in the upper legs), wide purple stretch marks, worsening high blood pressure or diabetes, and sometimes changes in fat distribution, according to Eren.

If you’re experiencing any of the above symptoms, Eren recommends discussing them with your healthcare provider rather than trying to diagnose yourself with high cortisol all on your own (or with the help of a chatbot). Chronic high cortisol levels that are undiagnosed can cause high blood pressure, diabetes, muscle and bone loss, higher infection risk, and cardiovascular complications.

But rest assured, cortisol disorders are rare. For instance, Cushing syndrome, a condition where you have too much cortisol in your blood for a long period of time, only affects 10 to 15 people per million each year, according to the Endocrine Society. Cushing syndrome is caused by a tumor on the pituitary gland at the base of your brain, not too much high-intensity exercise.

“During exercise, cortisol temporarily rises in response to the physiological stress and then decreases as the body recovers and the stressor resolves,” Erenler says. “In Cushing syndrome, cortisol exposure remains inappropriately elevated over time, and the normal regulatory mechanisms—including the normal circadian pattern and suppression of cortisol production—are disrupted.”

The Bottom Line

For most healthy people, there’s no need to try to suppress the normal cortisol response to exercise. Instead, the goal should be a sustainable training program that includes adequate recovery, sufficient sleep and nutrition, and variation in workout intensity.

“Don’t worry about the temporary rise in cortisol that occurs with exercise,” Eren says. “It’s a normal part of the body’s response to physical activity, not a sign that exercise is harming you.”

Erenler agrees and says the goal isn’t to eliminate cortisol—it’s to challenge your body appropriately and give it enough recovery to adapt to the stress you’re placing on it.