Do four to five rounds, rest 60 seconds, and repeat one time.
How to do it: Grab a pair of dumbbells and stand with your feet hip-width apart. (This exercise is tough, so you may want to try it without weights at first.)
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Keeping your torso upright, step forward with your right leg and lower your body until your front knee is bent at least 90 degrees and your back knee almost touches the floor. Push yourself back to the starting position and repeat with your left leg. Now move immediately to Part 2.
Instead of stepping straight forward into a lunge, step out at a 45-degree angle. Do a rep with both legs, then move on to Part 3.
Take a big step to the side with your right leg, then push your hips back, bend your right knee and lower your body until your right knee is bent at least 90 degrees. Push yourself back to the start and repeat with your left leg. Move to Part 4.
Instead of stepping straight forward into a lunge, step back at a 45-degree angle. Do a rep with both legs, then move on to Part 5.