HOW: Begin in a single arm high plank position keeping your body in line (feet up to shoulders). Allow the scapula to sag then push the scapula away from you pushing your chest away from the floor. Return back to starting position and repeat. Keep elbows relatively locked out, motion should primarily coming from the shoulder blade.
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.