Published September 28, 2026 11:53AM<\/p>\n<\/div>\n For this article, <\/i><\/b>Outside Run <\/b>contributor Danielle Zickl spoke to two endocrinologists to find out whether your high-intensity runs are actually messing with your hormones.<\/i><\/b><\/p>\n If you\u2019ve scrolled through social media lately, you\u2019ve probably seen wellness influencers claim high-intensity exercise increases cortisol<\/a>, the infamous \u201cstress hormone\u201d that, in excess amounts, can lead to fatigue, weight gain, trouble sleeping, high blood pressure, and elevated blood sugar.<\/p>\n 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\u2014and serve as excellent cross-training activities for runners\u2014HIIT workouts (like hill repeats, sprint intervals, and tempo runs) are key if you\u2019re training for a race or looking to build speed and power.<\/p>\n But are high-intensity runs and workouts actually messing with your hormones, or is the wellness side of the internet spreading misinformation? Here\u2019s what you need to know.<\/p>\n Cortisol is a hormone made by your adrenal glands<\/a>, which are located on top of your kidneys and are part of your body\u2019s endocrine system.<\/p>\n \u201cCortisol helps regulate metabolism, blood pressure, and the immune response, and it makes energy available when the body is under stress\u2014including during exercise,\u201d says Aysegul Eren, MD<\/a>, endocrinologist and medical director of the Adrenal Program at The Ohio State University Wexner Medical Center<\/a>.<\/p>\n 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\u2019s response to exercise and your ability to complete workouts.<\/p>\n \u201cHigher-intensity (HIIT) exercise reliably causes a temporary cortisol rise, generally related to exercise intensity,\u201d Eren says. \u201cThis is normal physiology, not something harmful to prevent.\u201d<\/p>\n How long cortisol remains elevated depends on the stressor, according to Feyza Erenler, MD<\/a>, an endocrinologist at Tufts Medical Center. It may be minutes to hours for a brief stimulus like exercise, she explains.<\/p>\n A 2021 meta-analysis of ten studies on HIIT<\/a>, published in the Scandinavian Journal of Medicine & Science in Sports<\/i>, found that cortisol increased immediately after exercise, often fell below baseline about two hours later, and returned to baseline within 24 hours.<\/p>\n \u201cThere\u2019s no evidence that a specific number of HIIT sessions causes chronically high cortisol,\u201d Eren says. \u201cThe more relevant concern is overtraining\u2014chronic training without adequate recovery\u2014which can lead to persistent underperformance. \u2018Too much\u2019 is individual, depending on training load, sleep, nutrition, recovery, and other stressors.\u201d<\/p>\n In fact, research<\/a> shows physical activity can actually lead to lower cortisol levels. A 2026 study<\/a> in the Journal of Sport and Health Science<\/i> found that those who did 150 minutes of moderate- to vigorous-intensity aerobic exercise (50 to 85 percent of their max heart rate) every week for a year saw a reduction in long-term cortisol levels.<\/p>\n Symptoms frequently attributed to \u201chigh cortisol,\u201d such as fatigue, poor sleep, anxiety, or difficulty losing weight, don\u2019t indicate that a person has high cortisol, according to Erenler. \u201cThese symptoms are extremely common and nonspecific and can occur for many different reasons,\u201d she says.<\/p>\n Signs of true high cortisol\u2014not the brief, self-resolving spike during exercise\u2014include 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.<\/p>\n If you\u2019re 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.<\/p>\n But rest assured, cortisol disorders are rare. For instance, Cushing\u2019s syndrome, a condition where you have too much cortisol in your blood for a long period of time, only affects ten to 15 people per million each year, according to the Endocrine Society<\/a>. Cushing syndrome is caused by a tumor on the pituitary gland at the base of your brain. It\u2019s not caused by too much high-intensity exercise.<\/p>\n \u201cDuring exercise, cortisol temporarily rises in response to the physiological stress and then decreases as the body recovers and the stressor resolves,\u201d Erenler says. \u201cIn Cushing\u2019s syndrome, cortisol exposure remains inappropriately elevated over time, and the normal regulatory mechanisms\u2014including the normal circadian pattern and suppression of cortisol production\u2014are disrupted.\u201d<\/p>\n For most healthy people, there\u2019s 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.<\/p>\n \u201cDon\u2019t worry about the temporary rise in cortisol that occurs with exercise,\u201d Eren says. \u201cIt\u2019s a normal part of the body\u2019s response to physical activity, not a sign that exercise is harming you.\u201d<\/p>\n Erenler agrees and says the goal isn\u2019t to eliminate cortisol\u2014it\u2019s to challenge your body appropriately and give it enough recovery to adapt to the stress you\u2019re placing on it.<\/p>\n Want more <\/b>Outside<\/i><\/b> health stories? <\/b>Sign up for the Bodywork newsletter<\/b><\/a>. And for tips on how to train, fuel, and recover better, <\/b>sign up for the Sweat Science 101 newsletter<\/b>.\u00a0<\/b><\/p>\nKey Takeaways:<\/h4>\n
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What Is Cortisol\u2019s Role in the Body?<\/h2>\n
The Connection Between Cortisol and High-Intensity Workouts<\/h2>\n
What Are the Signs of High Cortisol?<\/h2>\n
What This Means for You<\/h2>\n