It's time to invigorate your workouts -- and you're more ready than you think, says fitness expert and Reebok master trainer Sara Haley, who designed this series to boost cardiovascular endurance and burn fat. Pair these cardio moves with either your upper body or lower body strengtheners (or both!), depending on your Week 3 daily schedule.

For this first move, stand with your weight on the balls of your feet, heels slightly lifted, knees softly bent. Take small hops, rotating your clenched hands by your hips as if jumping rope. (Action jump rope is optional.) Continue for 60 seconds.

Begin with feet together, knees bent. Jump legs apart, arms in a Y, and land with soft knees (next image). Jump back to starting position with arms at your side. Continue for 60 seconds.

Run in place, lifting knees toward chest, squeezing abs, and pumping arms (alternate angle shown in next image). Keep chest lifted. Continue for 45 seconds.

Step right foot out to the side in a low squat and quickly bring left foot in to meet it. Repeat three times in one direction, then return (next image). Stay low throughout. Continue for 30 seconds.