Assessing different trunk exercises, Marshall et al. (2010) compared a number of swiss ball exercises, including the plank with arms on the swiss ball, single - leg hip
hyperextension from the push up position with legs on the swiss ball, single - leg squat against a wall on a swiss ball, swiss ball roll - outs, and swiss ball rolls, rotating from
lying supine on the ball and moving to prone with the upper body in contact.