Classification of Motion

Motions can be classified into five categories according to the length of the motion as shown below:

Class I. Movement of the fingers only as when picking up a cotton roll.

Class II. Fingers and wrist motion as used when transferring an instrument to the operator.

Class III. Fingers, wrist, and elbow as when reaching for a handpiece.¹

Class IV. The entire arm and shoulder as when reaching to change the light position.

Class V. The entire torso as when turning around to reach for equipment from the fixed cabinetry.¹