It seems like Jennifer Aniston is a mainstay on the list of the best bodies. In addition to her years of yoga, Aniston has taken up the aqua treadmill, a new fitness craze of water aerobics, according to reports. "I try to do some form of exercise, even if it's just for 20 minute a day, so that I get my body sweating and blood pumping," she recently said. Setting aside that time to do cardio or take the dog out for a run actually makes a difference. Take on Aniston's challenge to achieve 20 minutes of cardio per day and experience increased energy, better circulation and, of course, burned calories.