Scientists have known for a while that sleep and exercise have a symbiotic relationship, but that link is proving to be deeper and more essential than expected.
"The functions of sleep are to conserve energy and to repair tissues in the body," says Bradley Cardinal, Ph.D., a codirector of the Sport and Exercise Psychology Laboratory at Oregon State University. The more time you spend in the gym, then, the more shut-eye your body needs, says Cardinal. The results can be dramatic: After working out for four months, insomniacs got a life-changing 85 more minutes of sleep a night—better than any drug can deliver, a study in the journal Sleep Medicine found. (That's much better than any of these kooky insomnia cures.)
And the benefits go both ways: Deeper sleep ensures that your energy stores and muscle function are replenished, says Cardinal. "Snoozing well the night after you exercise makes your muscles and tissues stronger and more resistant to fatigue and injury," adds Jennifer Martin, Ph.D., a clinical sleep psychologist and a member of the Equinox Health Advisory Board. You can gain the full power of the sleep-sweat connection by following the four-point plan, here.
1. Have a High-Protein Bedtime Snack
People who drank a protein shake before hitting the sheets experienced a greater increase in muscle strength than those who didn't, according to research in the Journal of Nutrition. That's because in your body, protein breaks down into amino acids, which build up your muscles. Since most of us consume protein only with meals, "there typically aren't many amino acids available overnight for muscle growth," says Jorn Trommelen, Ph.D., a sports nutrition researcher at Maastricht University in the Netherlands. That means your body's prime recovery hours aren't being used to their full potential. To get the most muscle-building power while you sleep, try a protein-rich snack like Greek yogurt or a turkey roll-up. (Better yet, try one of these high-protein desserts.)
2. Step Up Your Game
It takes just 20 to 30 minutes of moderate-intensity exercise a few days a week to improve your sleep, says Kelly G. Baron, Ph.D., a clinical psychologist specializing in sleep at Rush University Medical Center in Chicago. "But more seems to be better," she says. Increasing the amount of time you work out or the intensity of your routine will translate into even sounder sleep, since your body will require more time to reenergize and repair. Dial it up slightly to get the bigger benefits: For instance, if you're a runner, tack a few extra miles onto one or two runs a week, or add one weekly session of sprints or hill repeats.
3. Turn In a Little Earlier
When you get more quality z's, your motivation to work out skyrockets, says Baron, who found that people spent more time in the gym when they slept more the night before. "Sleep affects people's perception of how hard exercise is," she says. If you're tired, your brain may try to convince you to save your depleted resources by hijacking your good intentions to visit the gym or by making your workout feel unusually difficult once you're there, according to the journal Sleep Science. All you have to do to regain your motivation is get to bed a little sooner—but not so early that you'll have trouble drifting off. Just 30 minutes should be enough to increase your drive to exercise the next day.
4. Go Fast In the Morning and Heavy at Night
If possible, schedule your cardio workouts for first thing and strength training for after work, say researchers at Appalachian State University in North Carolina. They found that people who did aerobic exercise at 7 a.m. spent more time in the deep sleep cycle—the kind that's most beneficial for your health—than those who did cardio at 1 or 7 p.m. For weight-lifting workouts, nighttime sessions improved sleep quality more than morning ones. (Up Next: The Health Benefits of Morning Workouts.)
Both types of exercise help you sleep by reducing the amount of stress hormones your body releases, says Scott R. Collier, Ph.D., the study's author. But doing cardio too close to lights-out can backfire. Your body temperature usually dips around bedtime, signaling to your system that it's time to sleep. A sweaty workout may disrupt that process by keeping you hotter for longer, says Collier. Resistance routines don't cause that big spike in your body temperature, so even if you lift an hour or two before bed, you'll still be able to nod off easily.