To reap the better-sleep benefits of exercise, aim to do 30 minutes of moderate to vigorous cardio at least five days a week. "You need to work out hard enough that you get your heart pumping and break a sweat," says Prevention's fitness expert and personal trainer Chris Freytag. "While brisk walks are simple and effective, find an activity you enjoy, whether that's taking a group cardio class at your local gym or a spin around the neighborhood on your bike." And don't sweat it if the only time you have to sneak in a workout is a few hours before bedtime. "The belief that evening exercise will keep you awake at night isn't true for the majority of people," says Shawn Youngstedt, PhD, an associate professor in the department of exercise science at Arnold School of Public Health. However, if presleep exercise does keep you awake, aim to fit it in at least four hours before bedtime. Does 30 minutes sound daunting? Break it up into three 10-minute sessions throughout the day. Read More..