Sleep and exercise work together like gears in a machine: When one turns smoothly, the other follows suit. Quality sleep supports athletic recovery and performance, while exercise releases useful brain chemicals, lowers stress and can help you fall asleep faster.
But for those battling insomnia, the rules can be different; even a small misalignment can throw the gears out of sync. Just as the benefits go hand-in-hand, so do the drawbacks: Exercise can stress the body, much like sleep deprivation itself. Exercising too intensely, too late in the day or too often can backfire, making it harder to drift off or stay asleep.
While most people don’t have to be overly mindful about workout routines affecting their sleep, those with insomnia — chronic dissatisfaction with sleep quality or quantity for at least three nights a week over three months — are more sensitive.
“People with full-blown insomnia tend to have a hyperactive stress system. Stressors tend to have a bit of an exaggerated response in the body,” said Dr. Christopher Kline, an associate professor of health and human development at the University of Pittsburgh. People with insomnia may not respond as well or recover as efficiently from the physical demands of exercise, he added.
But there are ways to exercise regularly without worsening sleep issues.
Why exercise sometimes leads to poor sleep
When you complete a grueling workout, you might expect to crash as soon as your head hits the pillow. But “you can’t exercise yourself to sleep,” said Dr. Kelly Baron, who is a clinical psychologist and the director of the behavioral sleep medicine program at the University of Utah.
She continued: “Sure, sometimes you can feel really physically tired from exercise, but it doesn’t mean you’re going to necessarily sleep better.”
The sleep-inducing benefits of exercise often come from moderate aerobic activities, like walking, jogging or cycling. But high-intensity exercise, like a half-marathon or a punchy HIIT session, can have the opposite effect: poor sleep quality, especially related to falling asleep.
“I’ve been working with elite athletes for years now,” said Kevin Morgan, the former director of the clinical sleep research unit at Loughborough University in England. “If there was a simple relationship between vigorous activity and energy expenditure and sleep, they would sleep like babies. And they don’t. They sleep badly.”
Exercise temporarily elevates heart rate, blood pressure and core temperature, factors that are counterproductive to sleeping. Elevated cortisol, the body’s stress hormone, is another potential cause. While most workouts lower cortisol, high-intensity or prolonged aerobic exercise can increase it.
Additionally, muscle soreness, pain and myoclonic jerks — sudden twitches from overworked muscles — can cause tossing and turning, Mr. Morgan said. “Training hurts,” he added.
How much, and when, matters
There’s no question that exercise is generally good for sleep. “People who exercise an hour get a bigger benefit than those who exercise 30 minutes,” Dr. Baron said. But you can overdo it. “More is better — up to a point,” she added.
Disturbed sleep is one of the key symptoms of overtraining, when your workout load is higher than your ability to recover, Dr. Kline said. For instance, more than six intense sessions a week can lead to difficulty falling asleep, according to a 2021 study. Another study found that both very high and low levels of exercise increased insomnia risk for some individuals, especially for those whose main physical activity comes from demanding jobs.
While the average gym-goer isn’t at risk of overtraining, a big change in exercise regimen — like preparing for a marathon or daily bootcamp classes — can exacerbate insomnia, said Dr. Cheri D. Mah, a sleep physician and lecturer at the Stanford Sleep Medicine Center. “That’s the time to evaluate what their exercise intensity, frequency and level is,” she said.
Timing matters, too. A 2022 study found that any physical activity after 8 p.m. caused people to sleep less while another study shows that intense exercise ending one hour before bed may disrupt sleep. Late-night workouts won’t negatively affect everyone with insomnia, Dr. Kline said, but people with the disorder are at greater risk than people without sleep issues.
How to tailor exercise for better sleep
While researchers haven’t definitively determined the ideal exercise routine for sleep improvement, a 2024 meta-analysis suggested moderate aerobic exercise paired with light strength training, mind-body practices (like yoga or tai chi) and traditional insomnia treatment.
Dr. Kline also recommended people with insomnia exercise at the same time every day.
“Routine is the guardian of good sleep,” Mr. Morgan said. “It maintains circadian rhythm.”
It’s also important to be deliberate about intensity and timing, pay attention to pain and soreness and find the right balance. If evening exercise leaves you feeling wired, switch to mornings or afternoons.
If the evening is your only free time, try shorter sessions and tone down the intensity.
Above all, find a rhythm. It can take weeks and months for an exercise habit to translate to better sleep, and the short-term effects can be pretty small, Dr. Baron said. Once you dial in a routine that works, the gears will start turning again — you will sleep better after being active, and your workouts will feel easier as you sleep through the night.
As Mr. Morgan said, “exercise is the gift that keeps giving.”
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