Strength Training May Be Better Than Cardio for Improving Sleep, Study Suggests

But the new data underscores that any exercise is better than none, when it comes to bettering sleep quality.

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woman doing strength training exercise to aid sleep
For the research, people who did strength training workouts focused on all the major muscle groups during their workouts.Getty Images

If you're looking to up your workout's?sleep-boosting?effects, try strength training, new data says.

Also known as resistance training, it helps you build muscle and improve flexibility, posture, and bone density. Now new research suggests strength training trumps cardio when it comes to better sleep outcomes.

The new data from researchers at Iowa State University found that for people struggling with sleep who were previously sedentary and overweight, consistent strength training workouts helped with falling asleep faster, staying asleep longer, and feeling rested and refreshed the next day compared with aerobic workouts or not exercising at all.

“This is the first big study to directly compare the effects of different types of exercise on sleep on a general adult population,” says Angelique Brellenthin, PhD, an assistant professor of kinesiology at Iowa State University in Ames.

“We always knew that aerobic exercise is good for sleep — there really is no argument there — but we were intrigued to find in the study that resistance training went above and beyond the benefits of aerobic exercise,” Dr. Brellenthin says.

Brellenthin reported the data today in a presentation at the American Heart Association Epidemiology, Prevention, Lifestyle, and Cardiometabolic Health Conference in Chicago. The data has not yet been published in a peer-reviewed journal.

Compared With Cardio, Strength Training Yielded Biggest Benefits for Sleep

Brellenthin’s study included 386 people classified as overweight or obese based on their body mass index. At the start of the study, participants had sedentary lifestyles and high blood pressure.

They were randomly assigned to four groups: no-exercise, cardio only, strength training only, or a combination of cardio and strength training. For 12 months, the study participants assigned to one of the exercise groups completed three, 60-minute workouts a week that were monitored by the research team.

For the cardio group, workouts were done on treadmills, stationary bikes, and elliptical machines. The strength training involved 12 resistance machines to work on all the major muscle groups in each session. The exercises included: leg presses, chest presses, leg curls, leg extensions, bicep curls, and shoulder presses.

Study participants had a key fob they plugged into each exercise machine to track their activity, allowing the researchers to track participants’ heart rate and progress.

At the start of the study and at the 12-month mark, participants rated their sleep quality using the Pittsburgh Sleep Quality Index, a validated self-assessment designed to measure seven domains of sleep (such as duration, disturbances during sleep, and restfulness).

The data showed that 35 percent of all participants were struggling with sleep at the start. And by the end of the year, everyone on average reported better sleep (yes, even the control group that did not do supervised workouts).

But by the end of the year, among those in the strength-training-only exercise group who weren’t getting at least 7 hours of sleep at the start of the study, 42 percent increased their sleep by an average of 40 minutes. By the end of the year those with sleep problems who were assigned to cardio increased sleep by 23 minutes, and those from the group that did both exercises who struggled with sleep initially got an extra 17 minutes of slumber. For the control group, poor sleepers reported getting an extra 15 minutes of sleep by the end of the year.

Other measures of sleep improved more for those doing just strength training, too, according to the data. Sleep efficiency — or how much time you spend asleep while in bed — increased for people who were strength training or doing both cardio and strength training. And sleep latency — or how much time it takes to fall asleep — also improved, decreasing by about three minutes for people who were pumping iron. There were no notable changes in these measure for the other groups.

Research Underscores That Any Exercise Is Better Than None and Can Help With Sleep

It’s unclear why resistance training may be more effective. Brellenthin has some suspicions why: for starters, when muscles adapt during weight training, they release testosterone and growth hormones, both of which are linked to better sleep.

She says that sleep provides our bodies with much-needed physical restoration. If study participants’ bodies are healing from the strain left from weight training, this may encourage them to sleep more deeply or longer throughout the night, too — because strength training would be more taxing on the muscles and require more recovery than cardio alone. Finally, Brellenthin says exercise is a great tool to manage stress and bolster mental health.

There is a major caveat to the research, though. Participants’ sleep outcomes were measured according to self-reported data instead of objective measures, like wrist sensors, electroencephalography (EEG), or polysomnography, which is used to monitor sleep and diagnose sleep disorders.

Marie-Pierre St-Onge, PhD, director of the Sleep Center of Excellence at Columbia University Irving Medical Center in New York City, says the study has an “impressive” sample size and retention rate. (The researchers had 400 participants to start with 100 in each group, and ended up with 386 participants who completed a year of committing to gym workouts.)

She isn’t dissuaded by the self-reported data either, she says. “Having a perception of better sleep is very important, no matter what the objective values say.”

Instead, Dr. St-Onge says the latest findings add to a growing body of research that suggests any regular exercise improves sleep quality — in a big way. It helps to relieve stress and anxiety; it tires you out, increasing your sleep drive; and if you’re exercising outdoors, the natural sunlight fine tunes your circadian rhythm, according to the Cleveland Clinic.

The bottom line and key takeaway from this study, she adds, is that any exercise is going to have marked benefits for sleep.

Other research pointed to both cardio and strength training boosting sleep quality, St-Onge says. A review published in 2017 in the journal Advances in Preventive Medicine, for example, concluded that exercise (either cardio or strength training) is an effective intervention if you’re having trouble falling asleep, staying asleep, or getting enough sleep. An earlier review also concluded that even moderate amounts of different types of exercise, such as brisk walking or resistance training, can improve your sleep.

How to Use Exercise to Improve Your Sleep

Brellenthin says definitely continue aerobic exercise if you’re already doing it. But if you’re looking for maxiumum benefts to your sleep, consider adding resistance training, too, which might help with sleep even more.

“The bottom line here is no matter what type of exercise you’re doing, you’ll have benefits for your sleep, and overall health,” St-Onge says.

More specifically, when it comes to making sure your workout routine helps promote good sleep:

  • Aim for 30 minutes of exercise five days per week. Adults should get about 150 minutes of moderate-intensity exercise per week, or 30 minutes a day on five days, according to the "Physical Activity Guidelines for Americans" from the U.S. Department of Health and Human Services. If the gym isn’t your thing, sneak in an afternoon walk on your lunch break, take a yoga class, or join an intramural sports team to get that activity in.
  • Add strength training into your workouts. If you’re new to resistance training, add it gradually, says Brellenthin. “Don’t go all out at first,” she warns. That’s because you may be putting yourself at risk of soreness, potential injuries, or straining a muscle. Start small, with a lighter weight load, and focus on getting comfortable with the equipment and nailing proper form, she says.
  • Avoid exercising too close to bedtime. Research has yielded mixed results on whether exercise may tamper with your sleep. While some research suggests that intensive exercise three hours before bedtime may increase your heart rate and body temperature in a way that’s disruptive to sleep, other data suggests as long as you leave an hour between the gym and your bed, sleep won’t be disrupted, according to a review published in 2019 in the journal Sports Medicine. St-Onge suggests one to two hours before bedtime should be the cut off, but figure out what works best for you.
  • If you do exercise later in the day, stick to light-?or moderate-intensity exercise. If your schedule only allows for evening workouts, make time to wind down with lighter exercise, such as yoga or stretching. These types of exercise are going to be less likely to disrupt sleep, and because they’re relaxing can actually help you wind down and prime the body for bedtime, St-Onge says.