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Control of Wrist and Arm Movements of Varying Difficulties

Control of Wrist and Arm Movements of Varying Difficulties. (December 2010) Jason Baxter Boyle, B.S., Texas A&M University Chair of Advisory Committee: Dr. Charles H. Shea Three experiments compared wrist and arm performance in a cyclical Fitts’ target task. The purpose of Experiment I was to determine if movement kinematics differed for wrist/elbow flexion/extension movements to targets of varying difficulty. Participants were asked to flex/extend a manipulandum in the horizontal plane at the wrist and elbow joint in an attempt to move back and forth between two targets. Online knowledge of effector position was displayed as a visual trace on a projector screen. Target widths were manipulated with amplitude constant (16) in order to create Indexes of Difficulty of 1.5, 3, 4.5, and 6. Results failed to detect differences in elbow and wrist movements either in terms of movement time, movement accuracy, or kinematic characteristics of the movement. In studies that have reported difference in wrist and arm performance in Fitts’ target tasks, experimenters have typically utilized visual amplification to counterbalance the small resulting wrist movements. The purpose of Experiments II and III was to investigate how changes in task parameters and visual gain play a role in providing a performance advantage for the wrist. In these experiments arm movement amplitude was increased to 32 and wrist amplitude was decreased to 8. Results found similar overall movement times for arm and wrist movements. However, kinematic analysis of the movement revealed relatively large dwell times for wrist movements at IDs of 4.5 and 6. Removal of dwell time resulted in faster