HOW: Start on your hands and knees then assume a high plank position. Perform the exercise by lifting one arm up and reaching towards the ceiling as you rotate your chest 90 degrees to the same direction to assume a high side plank position. Hold this position for a moment, then return to starting position. Repeat in the opposite direction, then repeat again.
FEEL: This should feel like an upper body and core workout, especially your shoulders and shoulder blades and triceps. Your lower body will be working as well to keep your hips up off the ground.
COMPENSATION: Maintain ideal shoulder position and keep your shoulders and arms stable as you perform this exercise. Do not let your hips sag, you should be rock solid maintaining ideal high plank and high side plank form as you move through this exercise. Quality over speed.