Lie on your back with a neutral spine and your knees bent at 90-degree angles. Extend both arms in the air. This is the starting position.
Pull your abs in toward your spine, keeping your ribs and pelvis still as you slowly lower your right leg and left arm down away from each other, extending them down until they are almost parallel to the floor. Move your leg and arm with control as you keep your torso and spine completely stable.
Return to the starting position, and repeat on the left side. This completes two reps.