A good night’s sleep is the key to having the energy we need to conquer the day, and yet, more than 30 percent of us don’t get the seven hours of shut-eye we need per night just to stay healthy, according to the CDC.
Big deal, or no? Well, if you care about getting the most out of your workouts (and life in general), your sleep is a pretty big deal. Skimp on sleep and your workouts (not to mention, your gains from the exertion) will suffer.
No Rest? You Won't Be Your Best
“People believe that, ‘Well if I don’t sleep I’m kind of a mess, but I can go for days on end and I’m fine,’” says Dr. W. Chris Winter, M.D., sleep specialist and author of The Sleep Solution: Why Your Sleep is Broken and How to Fix It. Winter explains that you may feel okay, and even have the energy you need to get through your day, but the research is clear that when it comes to exercise performance, you’re definitely not okay.
In fact, people who exercise may need more sleep than their inactive counterparts — especially when they exercise at a high intensity. “Since the role of sleep is to restore the body’s energy supply, it’s intuitive that the more high-intensity [the exercise], the more sleep you require,” says Dr. Robert Graham, M.D., M.P.H., co-founder of FRESH Med at Physiologic NYC.
Sleep plays the all-important role of restoring your immune and endocrine systems — the latter is responsible for creating and spreading key performance hormones like testosterone and human growth hormone throughout your body — as well as regulating brain function. And according to one scholarly literature review, the dreamless non-REM sleep phase in particular increases protein synthesis and the mobilization of free fatty acids to provide you with energy, which helps repair the muscles you broke down during your workout.
Sleep Better, Sweat Better
Winter notes that your exercise performance can decline very quickly after just one night of restricted sleep. A study on the effects of sleep deprivation on running endurance, for example, found that participants covered nearly three percent less distance on no sleep than they did when well-rested. Similarly, inadequate sleep can limit the maximal muscle strength you have to perform compound movements during resistance training, according to another recent review.
One of the main reasons poor sleep leads to less-than-optimal exercise performance has less to do with actual physiological changes to the muscles and cardiovascular system and more to do with perceived effort. In other words, a bad night’s sleep can make exercise feel harder, which will only make you fatigue sooner, according to a review in Sports Medicine.
In addition to making your workouts feel harder, poor sleep can wreck your motivation to work out at all. Participants in one study were less likely to complete their exercise session after a bad night’s sleep than they were after a night of restorative sleep. And the less sleep they got, the shorter their workout.
You may also find that disrupted sleep is messing with your workout recovery, making your next training session tougher to handle. The reason: When you don’t sleep, your muscles can’t fully restock their energy stores (in the form of muscle glycogen). As you may know, glycogen is one of your body’s main energy sources during exercise, and when you run out, you wind up hitting that dreaded wall. As the authors of one review say, “muscle glycogen shortage is known to reduce muscle function and total work capacity.”
What to Do After a Bad Night’s Sleep
Everyone’s goal should be to nab seven to eight hours of sleep per night. If you’re planning a high-intensity workout, Dr. Graham advises to “try to optimize that eight hours.” Think of that time as a bank of energy, which you'll spend on your workout.
But what if you’re really tired, or scored too few z’s last night?
First, dial back your exercise intensity and duration. Graham suggests 20 to 30 minutes of low-intensity movement (think: walking, jogging, swimming, yoga) as the ideal. Be patient and increase your work capacity slowly. “You don’t need to go all the way to the limit of where your body is at,” Graham says.
After all, sleep restriction acts as additional stress on your body, so why stress yourself even more with an intense workout session?