This exercise challenges the side plank by adding rotation of the spine and movement at the shoulder joint.
To do this exercise you will need a mat. Start in the side plank with your hand reaching to the ceiling. Inhale into the back of your ribcage and then exhale as you fold your body around your bottom shoulder. Inhale as you open the body back up to the side plank. Repeat 8-10 times on each side.
Things to think about
As you are folding the body around the bottom shoulder be sure that you are pressing the bottom hand into the ground to maintain shoulder congruency
As you fold your hips may lift a little, be sure that you are lifting the low belly to the hips as well.