The Alligator Sway Undulating their tails from side to side in a wavelike motion, alligators propel their bodies through space. In humans, undulation is most easily observed in traditional belly dancing, where the head and shoulders move in opposition to one another. This side-to-side movement of the cervical spine helps pump oxygen and nutrients to the joints, increases strength and flexibility, and aids in circulating cerebrospinal fluid. Since movement through each vertebral joint is critical