Start on your hands and knees, with your hands under your shoulders and knees under your hips.
Take one hand off the floor and reach in and through between your other arm and your legs.
Allow your body and head to follow, moving your shoulder down towards the floor as your hand reaches through.
You should feel a stretch down your side, your shoulder blade and neck.
Hold this position, and then return to the starting position.
Reach your arm out to the other side, and then up towards the ceiling.
Follow the movement of your hand with your head, twisting in the other direction to look up towards the ceiling.
Hold this position, and then repeat the sequence.