I love working out in the morning. It’s one of my keystone habits – the one routine that occurs at the beginning of the day that naturally puts me in the right frame of mind and on the path to a successful day. After my morning workout, I’m more energized, my mind is clear knowing my workout is behind me, and I just feel great after.

If I tell myself I’ll exercise after work, it never happens. Life catches up and my priorities change by the end of the day.

But that’s not to say the morning is the best time to exercise.

When is the ideal time – morning or afternoon/evening?

It depends.

AM Workouts – The Pros
When you wake after sleeping for 8 hours, your body has burned through the carbs and starts to tap into fat for fuel. You can take advantage of this if you exercise in a fasted state. You can also increase your calorie-burning rate throughout the remainder of the day. Plus, you can use the morning’s natural cortisol surge for an extra energy boost.

According to some research, early morning exercise is best for reducing blood pressure and improving sleep.

If you do an intense workout in the morning, I recommend getting some protein and fat (optional) in prior to prevent a catabolic state (your body eats your muscles for energy). My pre-workout food of choice is evolved coffee.

Also, if you have a difficult time getting your workout in in the evening because your drained from work or your willpower’s spent, its best to get it out of the way first thing in the morning.

Morning workouts are also a great time to use moderate amounts of caffeine from coffee or tea to improve performance and increase fat-burning (read more here).

The one negative to morning workouts (besides having to wake up early!), is the perceived effort may seem higher.

Since your core body temperature is relatively low first thing in the morning, it’s important to get a good warm-up in along with some dynamic stretches to reduce the possibility of injury.

So, if your goal is to burn fat and lose weight or you lack motivation at the end of the day, it’s best to do your routine in the morning.

PM Workouts – The Pros
Physiologically, the window for peak performance and lower risk of injury is in the late afternoon or early evening (4-5PM) when your focus, strength, and physically flexibility peak. Core body temperature and the rate at which your muscles can repair and recover (protein synthesis) peak around this time as well.

Research has shown that cardiovascular efficiency (VO2max) and sprint capabilities are also higher in the afternoon.

According to Dr. Charles Czeiser, the chief Division of Sleep Medicine in at Brigham and Women’s Hospital at Harvard Medical School, this is the time the body is sending out its strongest drive for wakefulness and funny enough, when most Olympic records are broken.

So if your goal is to improve performance and achieve the highest possible intensities during your routine, go for an evening workout.

One note about evening workouts – limit any type of exercise two hours before bed to prevent interruption in sleep.

Ultimately, the best time of day to exercise is the time of day during which you’re most likely to actually do it consistently. You could even mix it up a little if that’s more convenient.

Keep in mind, it’s just as important (if not more important) to just move often throughout the day than rely on one structured exercise period each day.