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The control of movements which vary in accuracy and complexity

University of British Columbia

The time required to program a movement response (reaction time) has been found to be directly related to the accuracy requirements of the response (Sidaway, 1991) as well as to the number of movement segments comprising the response (Henry & Rogers, 1960). However, since many of the experiments which have manipulated response complexity have concurrently manipulated the amplitude of the entire movement (Fischman, 1984; Lajoie & Franks, 1995), it was not possible to determine which of these factors was responsible for the change in reaction time. The main purpose of the present experiment was to determine whether the time required to program a limb movement was affected by response complexity, by movement amplitude, by target size, or by some combination of these factors. To answer this question, fourteen subjects made forearm extension and extension-flexion movements of varying amplitudes in the horizontal plane, to targets of varying sizes. The kinematic properties of these movements and the muscular activity which accompanies them (measured by EMG) were also investigated to determine whether these movements were exclusively programmed prior to movement initiation or whether some programming occurred during the execution of the movement. Pre-motor reaction time was found to be dependent upon response amplitude more than it was on response complexity or target size. However, a variation in the terminal target size was found to effect the kinematics of the entire movement, while a variation in the size of the start target was found to effect the kinematics of the initial portion of the movement. In addition, subjects adopted on-line control when the amplitude of the movement was increased and when the terminal target size was decreased. Finally, subjects appeared to control the EMG activation of their muscles by pre-programming the pattern of activity prior to movement initiation as well as controlling it during movement execution.

Thesis/Dissertation

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2009-02-12

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http://hdl.handle.net/2429/4522

Human Kinetics

University of British Columbia

UBCV

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