Start in a Side plank on a straight arm, with your top arm reaching to the ceiling.
Rotate your torso towards the floor and thread your top arm under your body, reaching as far as you can behind you.
Rotate back open and reach the arm to the ceiling again, then repeat.
Form tips
Keep your hips high as you rotate: the movement comes from your upper back.
Keep pushing the floor away with the support arm.
Risks
Unstable (weak) shoulders are at risk of dislocation with this exercise, so make sure you practiced a lot of Side plank and One-arm plank before attempting this one.
