The motor balance of the fingers of the open hand. An experimental study using a gonio-electromyographic technique.
The object of the present study was to shed light on the manner in which motor systems balance the fingers in the hand's opening phase in anticipation of a flexion grip. Using a previously described technique of gonio myographic recordings, the author performed a number of experiments in an attempt to demonstrate the mutual balance between the opening and grip-closing motor systems and between the extensor digitorum and the lumbrical system. The experiment involving execution of a normal precision flexion grip revealed that passive tension of the flexor dig. profundus under the influence of the lumbrical system was capable of balancing the extended fingers not just distally but even proximally against the extensor digitorum. The interplay between the active and passive forces of the opening and grip-closing motor systems respectively ensures continuity of motor balance throughout the gripping action. The experiments concerning the mutual balance of the extensor and lumbrical systems revealed that the functional task of the extensor, i.e. to create a basal grip size, provides the functional basis for lumbrical's operation in balancing the distal phalanges in a gripping position. As regards the flexion grip, the lumbrical system, by altering the grip size, serves as a regulating mechanism in the mutual balance of the hand's opening and closing. On the basis of the results of the present study the author outlines some fundamentals for exercising the hand in order to restore the flexion grip.
D004576:Electromyography; D005385:Fingers / Q000502:physiology*; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009132:Muscles / Q000502:physiology*