Want to sleep better? Hit the gym.
Getting quality, restorative sleep and seeing improvements in your athletic performance are two sides of the same coin. Poor sleep can kill your willpower to eat clean and exercise, and moving your body in healthy ways can set you up for better, more restorative sleep later in the evening.
Let’s look at the science behind it.
Endorphins, temperature, and sleep
The time of day that you exercise can impact your sleep. A lot of that has to do with rises in your core body temperature and release of endorphins.
Endorphins are chemicals produced by your brain and released for full body action during aerobic exercise (running, swimming, and other “cardio.”). These special brain chemicals can provide a natural, biological energy boost, because they can create a level of activity in the brain that causes some people to feel extra awake, alert, and happy. This is why some people say the “runner’s high” is an overwhelmingly positive experience.
Due to the potentially powerful effects of these endorphins, it takes a few hours for the body to calm down after their release. Overall, aerobic exercise a few hours before bed will give your body time to wind down and put you in a better place to have a restful, restorative sleep.
Exercise and body temperature
Physical activity raises your core body temperature not unlike the effect of taking a hot shower first thing in the morning. Elevations in core body temperature is a signal to your brain to wake up. Therefore, you don’t ever want to sleep when your core body temperature is elevated because your sleep likely won’t be restful and restorative.
The goal is to keep your core body temperature low throughout the night. Hypothetically, the lower your core body temperature is, the deeper sleep you’ll have. Lower core body temperature also increases likelihood of REM (rapid eye movement) sleep. REM sleep is necessary for learning and memory. To keep your core body temperature low in order to maximize restorative sleep after a workout, sleep in a cool room and even try sleeping naked.
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Cortisol and hormones
The biggest benefit of restorative sleep after working out is that a majority of your anabolic hormone release happens at night. The deepest stages of sleep trigger the release of testosterone (even in females) and growth hormone. The release of testosterone and growth hormone during the night aid in tissue repair, muscle growth, and anti-inflammation. This is why sleep is naturally restorative.
When you experience poor quality sleep over an extended period of time, your anabolic hormone release is reduced by 50 percent. There is nearly a direct linear relationship between hours of sleep lost and percent decrease in anabolic hormone release.
Blood sugar and hunger
Your body also releases less insulin, the hormone that regulates blood sugar levels. At the same time, your body secretes an increased amount of cortisol, a stress hormone that controls metabolism and blood pressure. Increases is cortisol and decreases in anabolic hormones shifts your body into a catabolic state. Catabolic states are detrimental to your overall health and fitness progress. Catabolic states make you more prone to injury, illness, and at the very worst, predisposed to diabetes.
Another effect of not getting enough sleep as it relates to blood sugar levels is an increase in your appetite. Your levels of satiety—that feeling of being comfortably full after eating a meal—can also be skewed, possibly causing you to consume calories that you otherwise wouldn’t. A recent study that looked at correlations between sleep deprivation and obesity found that people who consistently received between four and six hours of sleep each night had difficulties controlling their appetite signals and were inconsistent with physical activity.
There’s no magic recipe for what kind of exercise you should do to best support your sleep health. This is because everyone’s body is different and will respond to various forms of exercise in different ways. So what’s the best advice for choosing a fitness activity? Pick something that you’ll want to do consistently. Does heavy lifting or running inspire you to visit the gym? Do it. Does an active yoga class get your heart rate going? Go with that. Follow your instincts, as they will often lead you to something you actually enjoy doing.
For those of you who select heavy lifting, your recovery through sleep will be even more important. You will have to maximize your time spent in restorative sleep (go to bed early and sleep naked to stay cool) and possibly take a sleep-inducing supplement such as magnesium which helps to maintain health of the central nervous system.
Sleep is often a forgotten key element of a successful training plan. While a consistent exercise plan can improve the quality of your sleep, studies show that the inverse is also true. Decades of research have proven that getting quality, restorative sleep helps your body regulate stress, crush cravings for sugary foods and unhealthy carbohydrates, encourage muscle growth, and much more.
Enhancing your athletic performance doesn’t happen overnight. It takes the right combination of commitment, talent, nutrition, and appropriate rest. Quality sleep and consistent exercise go hand in hand, and creating a space for a healthy sleep routine can work wonders for your fitness goals.
CPT Allison Brager, PhD is a neurobiologist serving as an active duty Army officer with expertise in sleep and chronobiology. She currently serves as a sleep scientist in the Center for Military Psychiatry and Neuroscience at the Walter Reed Army Institute of Research, the largest and most diverse biomedical sleep research laboratory in the Department of Defense. She sits on the Federal Fatigue Management Working Group and has contributed to Army Doctrine on Holistic Health and Fitness through the Office of the Surgeon General. She consults with US Olympic, big-time collegiate, and professional sporting teams. CPT Brager recently received eight golds at the Gay Olympics in Paris, France, is an active competitor in Crossfit® and former Reebok Crossfit® Games team athlete, has coached NCAA decathletes and pole-vaulters, and a four-year varsity letterman in Division 1 Track and Field at Brown University.