For some, working out is easiest first thing in the morning. For others, it can be after the workday or even on the lunch hour. Of course, working out some is better than not at all but research suggests that there are optimal times of the day to work out to reach your fitness goals.

If you want a better night’s sleep it is best to hit the gym early in the a.m. Studies show that those who work out first thing in the morning slept longer and had a deeper sleep cycle than those who waited to exercise until later in the day. Better sleep can also increase cardio health, decrease stress and anxiety and help maintain weight.

Afternoon or late night exercise also comes with its own benefits. Those who workout later in the day often workout harder. You may perform better in the afternoon if you are swimming, running or biking. You may also be less prone to injury later in the day because you have had a chance to warm up so muscles become more adaptable to exercise.