But, there’s more to the exercise-sleep story. Not all workouts are created equal, so their physiological effects on the body also differ. And, since you might not want to take that aromatherapy, slow-moving yoga class all the time, there are some workout dos and don’ts to keep in mind, or what Geralyn Coopersmith, an exercise physiologist at Equinox calls "good sleep hygiene."
If you’re a cardio fanatic, Coopersmith suggests that in a perfect, never-have-to-work-a-day-job world, you should finish up your workout about six hours before bedtime — only if, and this is key, you are not a regular worker-outer. “If you are new to exercise, or just getting back into it, you really shouldn’t do intense cardio after 2 p.m. — instead, aim for a.m. workouts,” she says. “Heat revs the body up. And, exercise creates heat, therefore revving up your body’s core temperature. If you aren’t accustomed to that, it’s harder for your body to bring it back to base, which is what can disrupt sleep.”
Coopersmith says that after about three months of working out approximately three times per week, your body will generally get used to the heat-up and cool-down process. Essentially, working out is the calorie-burning equivalent of taking a hot bath to have a better night’s sleep — it’s not the heat itself that helps you get drowsy, but the rise and then fall of the body’s temperature that spurs the production of melatonin, the body’s natural sleep aid. (And, why experts often suggest sleeping in a cool, not warm, room: The sweet spot is normally around 68 degrees.)
“But, with more slow and steady cardio, a more parasympathetic response is triggered, and so it stimulates less of an effect on your body’s core temperature.” Also, super important to know: Remember to give your body rest days to recover between workouts. “One of the main signs of overtraining is insomnia,” she adds.
Lastly, if your sleep patterns are getting worse or suddenly on the fritz out of nowhere, that’s a warning. “At a certain point, the body starts to interpret the pain and fatigue that your muscles and body feels as danger, and this could cause you to not sleep well at night,” she says.