According to experts the best time to work out is between 5:00 and 7:00 pm,” says James Maas, PhD and YouBeauty Sleep Expert. Exercise at that time enhances the depth of sleep. And any aerobic activity, even fast walking, will improve your sleep. However, if you plan to be in bed at 10:00, finish up by 7:00. Exercise raises your body temperature and can interfere with sleep within three hours of bedtime. So block off those after-work hours for a solid run or class, and you may even get a better night’s sleep out of it.