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Want to Sleep Better? Avoid This Exercise Mistake at All Costs

Even in fitness, you can have too much of a good thing.

Sleep often feels like one of the most elusive pillars of health. So many things impact it, including your stress levels, how much caffeine you've had, and what you eat before bed. And if you're in pursuit of a better night's sleep, there's one piece of advice almost universal among experts: Exercise more.

Generally, any kind of exercise will help support better sleep, says Rob Arthur, CSCS. You just don't want to do any strenuous exercise too close to bedtime (within an hour) since per Harvard Health, that can make it harder to fall asleep and affect the quality of your sleep.

However, there is one type of exercise that, if done incorrectly, can mess with your sleep patterns no matter when you workout. "High-intensity HIIT-style workouts. If you do them a ton, and you're not recovering properly, you can get into a state where you're just overstressed…[and] your sleep can suffer," Arthur says.

But wait, isn't HIIT—which focuses on short bursts of intense exercises—really good for fat loss and getting strong? Yes, but it does have limitations. Here's exactly why too much HIIT can affect sleep—and how to ensure you get in your favorite workout without disrupting your rest. And for more sleep tips, check out 20 Ways to Double Your Sleep Quality.

The HIIT-cortisol connection

hiit workout

Doing really intense exercise (such as HIIT, or a super long run) makes your body release cortisol, aka the stress hormone. The hormone helps your body perform and adapt to physical stress by revving up your heart rate and breaking down carbs and fats faster for energy. This is a normal part of your body's "fight-or-flight" response, and is supposed to happen in short bursts.

How HIIT (and cortisol) affect sleep


However, if you push your body too hard without properly recovering (like doing HIIT workouts every day of the week), the constant release of cortisol can make sleep "go down the drain," Arthur says. Research published in Natural Medicine Journal found that elevated cortisol levels can disrupt the functioning of systems that control your sleep cycles, making it harder to fall and stay asleep.

This might explain why a Frontiers in Psychology study found that HIIT workouts did not help improve sleep quality for older adults with sleep issues. HIIT might also make people too sore and amped up to sleep, "counteracting the potential beneficial effects of exercise on sleep and tipping the balance toward inhibiting, rather than promoting, sleep," the study authors wrote.

Other risks of too much cortisol

Woman holding sore neck

Overtraining at the gym doesn't just disrupt your sleep. Consistently having too much cortisol floating around in your system can also throw the rest of your hormones out of whack. This can have a trickle-down effect on the rest of your body, contributing to issues like elevated anxiety and stress levels, muscle fatigue, and more. 

There are additional implications for women and people with uteruses. "[High cortisol levels] can increase hormones like testosterone and subsequently estrogen, while also decreasing hormones like progesterone," Robin Berzin, MD, founder of Parsley Health, told Well+Good. This can cause skipped periods, fertility issues, and even mess with your bone density if gone unaddressed.

Beyond hormones, HIIT can be rough on your bones, muscles, and joints. If you do it too often without recovering, you run the risk of injuring yourself. (Instead, consider trying: This One Workout Drives 29 Percent More Fat Loss, Says Science.)

Enjoy HIIT in moderation (with lots of rest)

hiit workout class

This isn't to say that HIIT is bad or should be avoided. But it's definitely a prime example of the risks of doing too much of a good thing. While some people thrive on daily HIIT, other people may have issues, says Arthur. If you're new to HIIT, the American Council on Exercise recommends doing it no more than one to two times per week.

Arthur also recommends that you use your sleep patterns as a way to track your overall stress, Arthur recommends. For example, if you change up your fitness routine and find that you're sleeping poorly, he says that could be a sign you're training too intensely for your specific circumstances or body.

"The body can only take so much stress," says Arthur. Listen to what it's telling you about your fitness, and adjust accordingly. For more on combatting stress, check out: Secret Side Effects of Meditating Just 12 Minutes Per Day, Says Study.

Jessie Van Amburg
Jessie Van Amburg is a freelance writer and editor who has covered health, nutrition, and lifestyle topics for top media outlets including Women's Health Magazine,, and Well+Good. Read more about Jessie
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