High plank with trunk rotation ("Plank (high) into side plank" Core/scapular stabilization)

Lie on your front with your hands under your shoulders.
Push yourself up into a plank position with your hands under your shoulders and a straight line from your head to your heels.
Holding this straight position, lift one arm up towards the ceiling.
Allow your head and body to follow the movement.
Your may rotate a little on the balls of your feet.
Return your hand to the floor and repeat on the other side.