But, depending on your goals, there are a few instances in which timing things right could work in your favor, says McCall:

If you’re looking to burn fat…on a deadline: Sweat in the morning. Why? When you wake up, your levels of the hormone cortisol tend to be high. “This hormone helps you metabolize fat for fuel,” says McCall. The thought is that you go for a run first thing in the morning (without eating anything first), you will burn more fat. (There’s still a debate on whether this works for high intensity exercise as well.) “Thing is, after a period of time your body adapts. So you can’t do it forever. If you want to lose a little extra weight for a wedding, you might do this five or six weeks before the event,” he says. Just remember: Weight loss is best done at a slow, steady pace. 

Try mixing these bodyweight exercises you can literally do anywhere into your new morning routine:

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If you’ve got a race on the calendar: Exercise around the same time of day the race will take place. This will help your body get acclimated to the specific time-of-day environment—conditions in the morning can be very different from the afternoon, says McCall. (Ready for a running challenge? Sign up for the Women’s Health Run 10 Feed 10 10-K!) 

If you’re jacked up from the day: If your work leaves you stressed out, a nice yoga class can be calming. (Or maybe you prefer to release pent-up anger with a balls-to-the-walls rowing workout.) It’ll be way more effective at energizing you through the rest of your night (hello, dinner prep) than an energy drink (or a handful of Sour Patch Kids).

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If you usually go to the gym after work, challenge yourself for a month or two to get up and work out first thing in the morning, and see how that feels, says McCall. “It might help you bust through a plateau.”

Otherwise, the rule of the game is to exercise when it fits into your routine, when it can be consistent, and when it feels natural for you. Don’t stress yourself out about finding the perfect time. Love a few sprints to the sounds of the birds singing at 5 a.m.? Do it. Crave hot yoga in the evening? That’s perfect. The idea is to make exercise easy to achieve—not throw roadblocks in your way.