Initially, plan to exercise for 20 minutes for a minimum of 3 days a week, Dr. Chromiak says. Build up to 30 to 40 minutes at a time. The more days you exercise, the better, but 3 days is a good starting point if you haven't been exercising.
If your size or fitness level prevents you from working out for 20 minutes a day, start with just 15 minutes and gradually work your way up, he suggests. Don't put off exercising if time is an issue. Even exercising for 10 to 15 minutes intermittently through the day helps strengthen your heart. And just a few minutes of exercise done regularly will eventually make it easier to go for longer periods.