You probably know cortisol as “the stress hormone.” It got that nickname because it’s released — from the adrenal glands, located on top of each kidney — in response to stressors, explains Dr Justin Mullner, a primary care sports medicine physician with the Orlando Health Jewett Orthopedic Institute. A stressor is anything that activates the stress response in your body; stress is the resulting neurological and physiological response.

“The issue with the nickname ‘the stress hormone’ is that it creates a negative association with cortisol, and this could not be further from the truth,” says Alex Rothstein, a certified strength and conditioning specialist, ACSM exercise physiologist, and coordinator in the Exercise Science Programme at New York Institute of Technology.

Activating your body’s sympathetic nervous system, a.k.a. your fight-or-flight response, is only part of cortisol’s role in the body. “Because most of the tissues in the body have receptors for cortisol, it’s a hormone that can interact with most of the body systems, and it’s a critical link in maintaining homeostasis and helping regulate the body,” says Rothstein.

For example, cortisol helps suppress the body’s inflammatory response, regulates blood pressure, blood sugar, and metabolic reactions in the body, and helps to control your sleep-wake cycle.

It’s your brain’s job, in conjunction with the pituitary gland — an endocrine gland at the base of the brain that produces hormones — to regulate how much cortisol your adrenal glands produce so the levels in your body don’t get out of whack and negatively affect those important functions.

What does cortisol have to do with exercise?
Exercise is a stressor. When you start breaking a sweat, that “serves as a robust activator of the neuroendocrine system, provided that the exercise is of sufficient volume (i.e., intensity and/or duration),” according to research published in the Expert Review of Endocrinology & Metabolism.

Physiologically, exercise causes a chain reaction that stimulates cortisol production: The brain’s hypothalamus secretes certain hormones in response to exercise, which activates the anterior pituitary, which controls the function of several other endocrine glands and eventually stimulates the adrenal glands to release cortisol, explains Mullner.

In other words, your body goes into a high-alert mode when you exercise, downgrading certain bodily functions, like digestion, while prioritizing those that are essential to the stressful situation, like increasing the amount of glucose in your blood for quick energy.

When your body starts to feel the stress of moderate- to high-intensity exercise, your cortisol levels do increase — but it’s a short-term surge that serves a larger purpose. “Stimulating the release of cortisol through regular exercise is an excellent and healthy way to regulate your stress response,” says Rothstein. “It’s a dose-response relationship: The body learns the appropriate amount of cortisol to release in response to various levels of stress by experiencing various levels of healthy stress.”

So that post-workout influx of cortisol is a good thing: Just like progressive training helps your body adapt to handle a higher load, increasing cortisol in your system helps your body adapt so it can better handle similar stressful situations in the future.

Here’s a simplistic running-specific example from Mullner: “If you increase your [kilometre pace] from 5 minutes to 4 minutes, your body releases less cortisol in response to the same load as before,” he explains. “If you can now run a four-minute kilometre, running a 5-minute kilometre will be less taxing on your system and less cortisol will be released as compared to when you could only run a 5-minute kilometre at your best.” That also improves how your body will react to other stressors, like a scary, unexpected email from your boss or an argument with a friend.

What happens when exercise results in too much cortisol?
There is such a thing as too much of a good thing. “An exercise load far in excess of what your body is adapted to can cause a massive release of cortisol, which is ultimately catabolic and can interfere with the body’s attempts to recover and to adapt to the exercise stimulus,” Mullner says.

Releasing excessive amounts of cortisol in response to excessive amounts of exercise is a protective measure by your body, he adds, but when you’re in a catabolic state, that means your body is breaking down fat or muscle — and recovery is when your body should be repairing muscle.

“Too much of anything creates a problem, and if you are constantly stressing out your body and causing it to release cortisol, then you are constantly breaking the body down and never giving it its ‘rest and digest’ (parasympathetic nervous system) phase to recover from the stressful experiences,” says Rothstein.

When your body is stressed to the max and starts dumping out a bunch of cortisol into your system, you’re likely to feel fatigued and lose motivation — that’s a red flag alert meant to communicate that you’ve pushed past your limits, says Mullner.

FYI: People who participate in endurance sports are more likely to risk cortisol imbalances — distance runners, for example, spend a significant amount of time putting their body under physical stress, which is associated with elevated cortisol exposure over prolonged periods of time, according to an older study published in the journal Psychoneuroendocrinology.

In fact, elevated cortisol is a potential biomarker of overtraining syndrome, according to a 2019 study in the BMJ Open Sport & Exercise Medicine. The symptoms of overtraining include an elevated resting heart rate, sleep disturbances, lack of appetite or weight loss, frequent colds and viruses, impaired recovery, higher perceived effort for the same sessions, and a lack of motivation

How can you keep your cortisol levels in check?
This isn’t something most people should overthink; unless you’re dealing with really severe symptoms that could indicate a more serious cortisol imbalance, you don’t really need to be doing regular blood, urine, or saliva tests to check your cortisol levels.

What you do need to do is manage your stress. It’s super important to remember that exercise is always a stressor, and stress is additive — our body can’t distinguish between a stressful day at work and your intense track workout. It’s called “allostatic load,” research published in Psychotherapy and Psychosomatics reports. Once your total amount of stress exceeds your ability to cope, it will lead to poorer health outcomes.

Chronic psychological stress impaired recovery of muscular function in a 2014 study published in The Journal of Strength & Conditioning Research, and the stress of negative life events impaired running economy alongside recovery, according to a 2016 study published in the International Journal of Sports Medicine. And people with higher stress levels failed to show fitness improvements over a two-week period, a 2012 study in Frontiers in Physiology found.

If you’re feeling overwhelmed, practice breathwork. Breathwork was deemed effective for improving stress and mental health, according to a 2023 meta-analysis published in Scientific Reports.

Practising mindfulness — a mental state prioritising being present — helped significantly reduce anxiety, depression, psychological distress, and stress levels, a 2021 review in Mindfulness determined. Using visualisation, positive self-talk, affirmations; reaching out to a friend; listening to music; and doing low-intensity exercise are all proven ways to relieve stress when you need to chill out fast.

But if tension lingers, you might want to tone down the intensity and frequency of your workouts — especially if that stress has been hanging around for multiple days in a row.

“People need to be more mindful of their daily, acute exercise loads as well as their more chronic workloads, so that there isn’t too much of a spike in load above what you have trained yourself for,” says Mullner. “Your body is very resilient and can handle incredible amounts of work, as long as it is properly prepared and adapted. Optimising your recovery through nutrition, sleep, and stress relief can also go a long way to minimising the negative effects of cortisol.”

When you give your body the proper time to rest and repair itself post-workout, cortisol will help you make gains — not impair that ability.

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