Bench or chair, medicine ball, fitness ball.
BEGINNER: Place palms on the edge of a bench or chair, keeping your arms straight, your back straight, and your knees bent. Bend at the elbows, keeping elbows pointing straight back and close to your sides and lower your body straight down until upper arms are parallel to the floor. Keep elbows pointing straight back and close to your sides. Return to starting position.
INTERMEDIATE: Perform as in beginner, but keep legs fully extended.
ADVANCED: Perform as in beginner, keeps legs extended straight and heels balanced on a medicine ball.
VERY ADVANCED: Perform as in beginner, keep on leg fully extended and resting upon a fitness ball from mid calf to heel, while holding the other leg up in the air the entire time. Switch leg positions and repeat on the other side.