Set-up: With the legs together and hips up, establish proper upper body posture with a neutral back. Place your hands on the ball at slightly wider than shoulder width - so that the upper arms are tucked at 45-degree angle to the torso - with fingers pointing forward.
Movement: Press the chest off the bosu ball until the arms are straight, then return to the starting position. Cue the descent by attempting to pull yourself down to the floor with your shoulder blades.