If you’ve ever had a good workout and then a great night sleep afterward, you already know that exercising is associated with better sleep. “We know that there are many specific physical effects of exercise on sleep itself,” says board-certified clinical psychologist Michael J. Breus, PhD, aka (The Sleep Doctor). “Research shows that regular exercise seems to give people deeper —stage three and four—sleep.” Dr. Breus also says that it seems to make people sleep longer, and reduce stress, which could also affect your sleep. The question is how to exercise for better sleep. Because some workouts may have the opposite effect, depending on what time of day you do them—kinda like drinking coffee.

While exercise overall improves sleep quality, and according to Johns Hopkins Center for Sleep, individuals who partake in at least 30 minutes of moderate aerobic exercise daily may notice a difference in sleep quality the same evening, there is still debate about what time of day that cardio work should take place. One of the main reasons for this—exercise raises the core body temperature. “As our bodies cool, starting at about 10:30 at night, this is a signal for the brain to release melatonin to start the sleep process,” explains Dr. Breus. “If you exercise too close to bedtime, within about three to four hours, you will artificially raise the temperature of the body, and then disrupt sleep.”

The other culprit for the jolt of energy you may get form a workout? The neurochemicals released by the body during exercise, also known as endorphins. “There is no question that exercise can cause a level of alertness, which will translate into ‘waking you up,’” explains Dr. Breus. Longer workouts that stress your body at the type that cause endorphins to spike (as well as cortisol, the stress hormone, which is naturally lower while you sleep). This is why running and other high-intensity workouts aren’t ideal before bed.

If you have a hard time sleeping post-workout, maybe try exercising earlier in the day, or if you must get your activity in close to bedtime, Dr. Breus recommends low-intensity options. “Something like balance work or yoga might be great,” he says. Practicing meditative breathing exercises and stretching may also improve the quality of your sleep because both slow down the heart rate and help relax the brain.

Try this yoga flow for better sleep before bedtime: 

The take way: Exercising improves sleep quality, but you want to avoid doing long, stressful workouts within three or four hours of your bedtime to prevent disturbing your zzzs. So maybe snooze that HIIT workout until the morning.

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