The Fat-Blasting Model Secret: Three-Circuit Cardio Workout

This workout from Andrea Orbeck — trainer to models like Heidi Klum and the women of Victoria's Secret — is great for those days when you need a solid routine but don't want to go crazy. "Cardio is important to get into a fat-burning zone to keep you nice and lean," Andrea says. This workout "breaks up the monotony of a 45-minute session."

This simple workout is broken up into three 15-minute circuits. The first section is done at one continuous moderate-effort pace, followed by a second section broken up into intervals: three minutes at a hard pace followed by two minutes of recovery. The final section features pumped-up incline and resistance to keep the sweat going. You can do this on either a treadmill or a stationary bike; feel free to modify the level and speed suggestions below if you need something slower or faster. Remember to adjust the incline down to what is comfortable during the interval section (such as 0 or one percent incline).