The instant center of rotation (also, instantaneous velocity center, instantaneous center, or instant center) is the point fixed to a body undergoing planar movement that has zero velocity at a particular instant of time.
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The physiological cervical spine [[kinematics]] involves not only the amount of motion but also the nature of motion. The nature of [[motion]], known as quality of motion, is difficult to evaluate clinically, although it can be assessed by measuring the mean instant center of rotation
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