Take weight loss to the limit through this cardio-intense workout created by the personal training team behind "The Biggest Loser," with ultimate motivator Bob Harper setting the pace in a six-week program designed to get the heart pounding. Harper leads off with a 25-minute core strength session, and former contestants Tara Costa and Sione Fe fuel the calorie burn with 10-minute segments that can be alternated or combined to crank the intensity.