There are no excuses for skipping this 20-minute workout; it requires no equipment, so no matter where you are, you can fit in a sweat session. Quick and effective, today's workout in our Better-Body Challenge mixes classic cardio moves with bodyweight strength-training exercises to burn calories and build muscle. 

Print the workout, learn the moves below, and then get at it. Run in place while lifting your knees high to the level of your waist. Engage your abs as the knee comes up. Pump your arms to warm up your upper body. Read more here: