Abstract
The purpose of this study was to document, using electromyography and electrogoniometry, the normal function and interaction of extrinsic finger muscles of normal subjects during five exercises to establish a baseline of “normality.” The exercises, typical components of occupational therapy activities, were resisted grasp, resisted finger extension, rapid and slow unresisted finger extension, and grasp-release of a lightweight cylinder. A high percentage of electrical output of all three extrinsic finger muscles was generated during resisted or rapid exercises A very low percentage of output was generated during unresisted slow exercises Carryover effects of the exercises (i.e., changes seen in movement after versus before) were limited to increased range of motion and increased level of electrical activity of the three muscles during rhythmical opening of the hand after resisted grasp and rapid extension The most common pattern of usage was reciprocal between agonist and antagonist, although no muscle was ever silent. True cocontraction occurred in only the most resistive exercise—grasp. No correlation was found between average wrist position and percent of muscle output. Intersubject variability suggests that the specific results of this study cannot be generalized However, the concept that resistance and speed increase motor unit recruitment of antagonist as well as agonist may be generalized.
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