Place both hands on your yoga mat shoulder-width apart. Fully extend your legs so that your body is in one straight line from head to toe. You should be resting on the balls of your feet. Gently draw your ribs to your hips to engage your core. This is your starting position.
Keeping your left foot on the floor, bend your right knee and bring it in toward your chest. Then extend your right leg to return to the starting position.
Keeping your right foot on the floor, bend your left knee and bring it in toward your chest. Then extend your left leg to return to the starting position.
As you become more familiar with the movement, begin to pick up the pace. It should feel like you're running in place. Don't forget to drive your knees to your elbows, always picking your feet up and off the mat.
Continue alternating between your right and left sides for 40 seconds, then take 20 seconds of rest.