Trouble Sleeping or Insomnia After Working Out? Here's Why

There was a time where I trained late at night.

I’d come home exhausted...but then I’d end up lying in bed restless.

This is a pretty common story among people who try to sleep shortly after working out. I’ve summarized all the research I could find on this topic so that we can get some answers and potential treatment ideas.

How Common is Insomnia After Working Out?

The relationship between exercise and sleep is complex, and that has led to a lot of misunderstandings.

Back in the 1990s, not exercising at all anytime near your bed time was a part of good sleep hygiene.

Since then, it’s been found that light to moderate exercise doesn’t worsen sleep in most people (1).

Evening exercise was not associated with worse sleep. These findings add to the growing body of evidence that sleep hygiene recommendations should not discourage evening exercise.

We also know that exercise in general improves sleep, especially in older people who are more likely to have sleep issues (2).

But very few researchers have looked at the effect of intense workouts before sleep.

Recently, a study looked at the complaints of 36 young weightlifters after they worked out (3):

• Increased fatigue (27 out of 36)
• Sleep problems (26 out of 36)
• Restlessness (18 out of 36)
• Decreased appetite (12 out of 36)

Fatigue is expected, but the fact that nearly 75% of the subjects experienced sleep problems demonstrates that intense exercise is likely to cause sleep problems.

SummaryLight exercise is unlikely to cause difficulty falling asleep, and it may even improve sleep. However, the limited research on intense workouts suggests that performing these any time close to sleeping could lead to insomnia symptoms.

The 4 Potential Causes of Sleep Troubles After Working Out

As I said, research in this area is pretty light, so the causes of sleep problems after working out aren’t 100% clear.

However, there is some research that does suggest some likely causes.

Hormones (Adrenaline, Cortisol)

Intense exercise simulates a “fight or flight” response, which triggers some pretty drastic hormonal changes.

This is by far the most likely reason for sleep difficulty after exercise.

Let’s start with adrenaline.

Epinephrine (adrenaline) and norepinephrine mostly go together in your body. High levels of these lead to high levels of energy and concentration.

Good when you’re fighting for your life, but not when you’re trying to fall asleep.

During mild or moderate exercise, there’s very little rise in plasma levels of adrenaline (4).

However, there’s a significant rise during exercise that is perceived as intense (i.e. a hard workout). Take a look at these graphs of various hormones (mainly the top 2) in untrained patients after 30 minutes of high intensity exercise (5):

Adrenaline and noradrenaline were rising the entire duration of exercise, and then returned to baseline levels after about 60 minutes of rest.

In a study of more trained individuals performing HIIT (sprints), it was found that adrenaline concentration continued to rise after each sprint (6):

Unfortunately, they didn’t measure adrenaline levels during recovery. However, with a higher peak level of adrenaline, it may be possible that it also takes longer to return back to baseline levels.

Now what about cortisol?

The other main hormone involved in exercise and sleep is cortisol - the “stress” hormone.

Typically, cortisol peaks in the morning and declines throughout the day (with a few small peaks after eating). This is important since you need low cortisol levels to sleep well.

But exercise can also spike cortisol. The longer the exercise, the more likely the cortisol will become an issue. That makes this a big concern for endurance athletes who exercise at night.

You can reduce cortisol spikes with vitamin C supplementation (more on that later), which may help.

SummaryIntense exercise causes adrenaline, noradrenaline, and cortisol to rise and remain elevated afterwards for at least an hour. You need low levels of all of these to sleep well.

Working Out Raises Your Core Temperature

Much like light affects our circadian rhythm (which helps govern processes like sleep), so does body temperature (7).

You typically sleep better when it's cold, which is why so many people have sleep troubles when their room is too hot.

This is an issue because exercise raises your core body temperature (8):

That graph above is from a study where they looked at temperature during and after exercise at different room temperatures.

If you’re in a cold room (the bottom line at 4 degrees Celsius), it only takes 10 minutes to get your core temperature back down to baseline.

However, if you’re in a typical room temperature environment, your core temperature will remain slightly elevated even after 30 minutes. And if you live in a really hot place, it’s likely worse, making it even harder to fall asleep.

Research has clearly shown that an elevated temperature leads to sleep onset and maintenance insomnia (trouble getting to sleep and staying asleep) (9).

This can also lead to a significantly altered sleep architecture, as your circadian rhythm is disrupted. This may lead to less deep sleep, meaning more restless sleep in general.

SummaryExercise raises your core body temperature significantly, which is likely to cause sleep difficulties if you try to sleep before it’s cooled back down. Depending on the temperature of your environment, this can take 10 minutes, 30 minutes, or much longer.

Sleep Hygiene Issues

Depending on the form of working out that you’re doing, it may introduce some sleep hygiene issues, which can lead to low sleep quality.

If you go to a commercial gym, it’s likely quite bright, and more importantly you might be exposed to blue light (which comes from screens), which is known to make it very difficult to get to sleep (10).

Gyms often have TVs playing non-stop, and you many gym-goers look at their phones between sets.

Additionally, some people consume caffeine before workouts (caffeine is one of the biggest risk factors of insomnia).

Electrolyte Depletion

This is less studied and less likely to be an issue, but if you’ve tried everything else, there is a small chance that electrolyte depletion could be causing insomnia symptoms.

The electrolyte that is most important for sleeping is magnesium.

Magnesium is used and depleted during muscle contractions (11).

If your magnesium levels are too low, it can lead to sleep difficulties. Use a tool like Cronometer to monitor how much magnesium you’re consuming, or get a blood test from your doctor.

Having an important mineral deficiency can also cause restless leg syndrome. There's a decent amount of research connecting restless leg syndrome and insomnia.

How To Reduce Sleep Troubles After Working Out

Now that we know what might be causing sleep troubles after working out, we can try to find a way to at least mitigate them a bit.

Here’s a full list of potential things that may help someone with exercise induced insomnia:

• Working out earlier - I mean, duh, but it’s the simplest solution. While early morning is ideal for some people, even 30 to 60 minutes earlier than you're used to in the late afternoon or evening can help hormone levels and body temperature to drop to appropriate levels.
• Reduce the intensity - High intensity training is linked to sleep issues in research. However, many studies have shown that moderate exercise rarely causes sleep problems and typically leads to better sleep than none at all.
• Take a moderately cold shower afterwards - If you want to bring down your body temperature quickly, a cold shower (plus A/C after) is a good way to do so. Don’t go too cold, as that might stimulate more adrenaline.
• Supplement with vitamin C - Studies have shown that vitamin C supplementation can blunt cortisol response during exercise (12). You can have it earlier in the day at any point. The best results were seen in runners who supplemented with 1500 mg, compared to 500 mg (small effect) (13).
• Avoid screens - Sometimes it’s out of your control, but if you’re able to turn off TVs in the gym, do it. Additionally, try not to look at your phone as much as possible.

One final thing I want to mention is that stress is a leading cause of insomnia symptoms in general.

What I’ve experienced in the past is that I would train hard and feel exhausted, then think about all the things I needed to do the next day, and that would cause stress and anxiety.

This isn’t the easiest thing to solve, but you can mitigate the stress by planning to do easier things in the morning, and just remembering that you won’t feel as tired when you wake up as you do right after the workout.

If you get to the point where you don’t think that any of these causes are the root of your sleep trouble, it’s time to go see a doctor. They can do blood tests for nutritional deficiencies, and sleep tests to identify specific issues you’re having.

References

1. Does nighttime exercise really disturb sleep? Results from the 2013 National Sleep Foundation Sleep in America Poll
2. Exercise training improves sleep quality in middle-aged and older adults with sleep problems: a systematic review
3. Post-intense exercise sleep concerns in weightlifters: A pilot study
4. Adrenaline Secretion during Exercise
5. Continuous Glucose Monitoring Reveals Delayed Nocturnal Hypoglycemia After Intermittent High-Intensity Exercise in Nontrained Patients with Type 1 Diabetes
6. Plasma catecholamine and nephrine responses to brief intermittent maximal intensity exercise
7. Thermosensitivity of the circadian timing system
8. Exercising in the cold inhibits growth hormone secretion by reducing the rise in core body temperature
9. The relationship between insomnia and body temperatures
10. Sleep Disturbances Are Related to Decreased Transmission of Blue Light to the Retina Caused by Lens Yellowing
11. Can Magnesium Enhance Exercise Performance?
12. Inhibitory effect of ascorbic acid (vitamin C) on cortisol secretion following adrenal stimulation in children
13. Vitamin C supplementation attenuates the increases in circulating cortisol