HOW: Begin in a single arm high plank position keeping your body in line (feet up to shoulders). From a high plank position, push yourself into a downward facing down, push the shoulder blade away from you as you move into this position. Return back to starting position and repeat. Keep elbows relatively locked out, motion should primarily coming from the shoulders.
FEEL: The Shoulder muscles working.
COMPENSATION: Avoid moving at the elbows as you perform this exercise. Also avoid rotating, keep your hips and torso towards the floor throughout this motion.