Stand with your feet about shoulder-width apart. This is your starting position.
Bend at your hips with your knees softly bent, and place your hands on the floor directly in front of your feet.
Inhale, and without moving your feet, walk your hands forward until you're in a plank, body in one straight line from your head to your heels. The push-up is optional.
Exhale, and without moving your feet, walk your hands back to return to the starting position, keeping your legs straight but not locked. When your hands reach your feet, stand up to return to the starting position. That's one rep.