Since I travel so much, I’ve learned to be pretty self-directed in my exercise. I’ll take advantage of a hotel gym or pool, or grab a morning run outdoors (a great way to help alleviate jet lag). But over the years I have worked with personal trainers, to help me learn more about how to exercise more effectively and safely, and to raise my fitness to a new level.
Sleep has deep ties to physical activity. It’s during sleep that the cells of muscles, joints, tendons repair and restore themselves, so we’re able to be active the next day. Being rested makes us more attentive, with greater balance, coordination, strength, and endurance, all of which helps us work out faster, harder, smarter—and with less risk for accidents and injuries. Without a good night’s rest, we’re less likely to have the mindset and motivation—or the energy—to stick with our intentions to hit the gym.
With all that sleep can do to enhance exercise, there’s still a lot of missing knowledge about sleep among personal trainers and other exercise and athletic professional. These are the things I’d most like personal trainers—and everyone who exercises—to know about sleep.
The timing of workouts matter—but the when of exercise is NOT one-size-fits all
Yes, there are optimal times to exercise. But they aren’t the same for everyone. That’s because exercise, like so much else about the way we live and the way our bodies function, depends on our individual bio rhythms and bio type. (Don’t know your bio type yet? Take my quiz at www.chronoquiz.comto find out.) The best time for exercise also depends on the type of workout you’re doing, and what you want to accomplish from that workout (such as fat burning, performance enhancements, energy boost, improvements to sleep itself).
Morning and evening runs or other aerobic workouts are the best times to burn fat and boost metabolism. Morning exercise also helps improve sleep, including increasing amounts of deep sleep. (Dolphin bio types: aerobic exercise early in your day can be especially beneficial for you, a type that naturally spends less time in deep sleep and more time in lighter, more restless sleep.)
For strength training, physical trainers should encourage their clients to work out when their muscle strength is at its peak daily rhythm. (Yep, muscle strength fluctuates with bio time.) For early rising Lions, that means midafternoon, between 3-5 p.m. Bears hit their muscle strength peak a little later, typically between 4-7. Wolves will find their peak strength between 6-7 p.m. and Dolphins at around 8 p.m.
Midday (for early rising bio types) and late afternoon (for late-rising bio types) are an ideal time for a yoga or Pilates session, or a dance class—at these times, our bodies are warmed up, and able to handle the different moves and positions with less risk of injury. Gentle yoga or other mind-body exercise can also be part of your evening Power Down Hour, especially for Dolphins and Wolves. This relaxing exercise can reduce levels of cortisol, which is particularly helpful for these wired-at-night types.
For every bio type and every type of exercise, there are a couple of worst times for a vigorous workout. One is right at dawn. I know it’s convenient to schedule exercise early to get it out of the way, but not even Lions can get the best out of their exercise this early in the morning. Injury risk is high, and performance is low. If you’re looking to work out in the morning, wait until an hour after the sun rises before you start to sweat it out. The other is right before bed. A gentle, relaxing round of stretching or yoga is fine as part of a pre-bedtime routine, but a vigorous workout will elevate core body temperature and release endorphins, both of which can keep you awake.
Lack of sleep makes us more prone to injury
Sleep continues to be an overlooked factor in injury risk for regular exercisers, as well as competitive, elite, and professional athletes. How does lack of sleep contribute to higher risk for injury? By slowing reaction times, compromising motor skills, impairing judgment, inhibiting our ability to assess risk. Getting abundant sleep on a nightly basis is one way to lower your risk of athletic injury. This 2017 study found that routinely sleeping more than 8 hours a night reduced young athletes’ injury risk by more than 60%.
Not sleeping enough interferes with healing
Responsible personal trainers and coaches know that the body needs rest to heal itself after injury and illness. But I think too often the idea of “rest” focuses on refraining from exercise—which is important—but overlooks the power of sleep in healing and rebounding from a workout-sidelining injury. Sleep—particularly deep, slow-wave sleep—is a time of intense cellular regeneration and repair. It’s during nightly sleep that body produces its highest levels of HGH (human growth hormone), one of our most potent natural healing bio-chemicals. The immune system also restores itself to full, optimal function during sleep. Research shows poor quality and insufficient sleep increase inflammation, and reduce the activity of the immune system’s healing and disease-fighting cells. In addition to a greater risk for injury, we’re also more likely to get sick when short on sleep. This 2009 study, for example, shows that sleeping less than 7 hours a night is linked to a nearly 3 times higher risk of catching a cold.
Sleep improves our mental and emotional game
Sleep isn’t only a time for physical healing. It’s also when the mind restores an emotional balance, enabling a more positive outlook and greater mental persistence and focus. Many people in the athletic world (and beyond it) still don’t give sleep its due for the role it plays in elevating mood, and strengthening mental endurance. There’s abundant research showing that sleep can alleviate depression, stress, and anxiety. Sleep also influences mental toughness—something that every athlete, at every level, needs. A 2019 study focused on the relationship between mental toughness and sleep in a group of athletes, and found that sleeping for longer amounts and getting more restful sleep both increased mental toughness, while a lack of sleep was linked to diminished mental toughness. To reach new goals in physical workouts, sometimes we need to dig deep mentally. Sleep helps us do that.
Lack of sleep limits coordination and motor skills learning
If you’ve ever worked with a personal trainer, you know they like to mix things up. One day might be power yoga, the next day a cycling workout, followed by HIIT training or an endurance swim. You and your trainer might not realize it, but sleep plays a critically important role in your ability to learn new skills and routines. Sleep reinforces the brain’s motor skills learning capacity—our ability to learn how to perform new actions and routines with our bodies. What’s more, we need ample sleep on both ends of motor skills learning; we’re better able to pick up new routines and physical actions when we’re rested, and as research, including this 2017 study, shows, getting a good night’s rest after we’ve learned a new skill helps reinforce that learning, thanks to the time we log in deep, slow-wave sleep.
A morning workout routine may require a bedtime shift
Your trainer may recommend morning workouts to you—I hope after they’ve considered your individual biotype information and the other when factors of exercise that I’ve touched on above. What your trainer might not realize? That an early morning workout routine may mean you need to make an adjustment to your bedtime, to keep getting the right amount of nightly sleep for you. (You can use my bedtime calculator to determine your optimal sleep amount.)
Morning workouts can be tremendously energizing and productive, a great way to start the day. New research shows that morning exercise can help advance the body’s bio clock, helping us feel more alert, energized, and able to be active earlier in the day. (Thanks to factors including a society-wide clock that’s out of sync with our own, and excessive exposure to artificial light at night, many people’s body clocks lag behind where they would fall naturally and optimally, leading to fatigue and sluggishness in the morning.)
But pitting sleep and exercise against one another doesn’t do you any good. If you’re carving out time for workouts in the morning, make sure you’ve also earmarked enough time to get all the sleep you need.
Exercise has big benefits for biorhythms (and that’s a big deal for health)
It’s not only the timing of the body clock that can benefit from exercise. Because our bio hythms affect nearly every aspect of our physiology, any benefit exercise delivers to circadian biorhythms stands to have a huge ripple effect on our health. Increasingly, scientists are identifying the benefits of exercise on biorhythms. Research shows that exercise affects the activity of the body’s master bio clock, located in the brain’s suprachiasmatic nucleus, as well as the “peripheral” bio clocks that exist in cells throughout the body. By helping keep these clocks running in sync, exercise improves sleep as well as a myriad of other physiological functions, including cardiovascular health and the regulation of hormones, including those that promote sleep. Sleeping well and exercising regularly can limit unhealthful levels of cortisol, boost serotonin and melatonin. A new study published in 2019 shows that scheduling exercise at bio-clock friendly times can have potent positive effects on metabolism, and may help to treat metabolic disease, such as obesity and type 2 diabetes.
Poor sleep magnifies pain
You know the expression, no pain, no gain? Well, if your trainer pushes you to get into the pain-zone in order to improve your strength, speed, agility or endurance, they’d better also be pushing you to get plenty of rest before and after those intense workout days. Sleeplessness lowers our threshold for pain, making us more sensitive and attuned to the discomfort, and less able to cope with ongoing or chronic pain. Poor quality sleep compromises the body’s ability to inhibit pain, by lowering the activity of the body’s own natural pain-soothing chemicals. Research shows poor sleep also makes us more vulnerable to future chronic musculoskeletal pain, as well as to pain conditions including headaches, migraine, and fibromyalgia.
Exercise—of all types—really does improve sleep
Okay, so your physical trainer probably does know this one. But it’s worth repeating anyway. Physical activity helps keep sleep-wake cycles regular (thanks to its positive effects on biorhythms), it lengthens time in deep sleep and makes sleep less restless, shortens the time it takes to fall asleep, and can increase overall sleep amounts. Cardiovascular exercise, strength training, mind-body exercise—they’ve all been shown to enhance the quality and quantity of nightly rest. As we age, exercise can become an especially effective natural therapy for maintaining healthy sleep. (This 2016 study showed that 30 minutes daily of either cardio or strength training made significant improvements to sleep quality and reduced restless sleep in older adults.)
There’s no magic bullet for sleep. But exercise is about as potent a weapon as there is in your sleep arsenal.
Michael J. Breus, PhD, DABSM
The Sleep Doctor™
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