THE PATTERNING OF SKILLED MOVEMENTS 



1683 



angular cone of action (see fig. 2). This action is 

 mediated by a series of muscles acting in the several 

 planes. From the combination of various active 

 muscles and their relative intensity of contraction 

 there results an infinite variety of possible positions 

 of the lever arm. Aside from the hinge joints of the 

 metacarpals and between the phalanges which give 

 more rigidity to the digitals, the articulations of the 

 fingers, of the thumb and of the wrist are ball joint 

 articulations with all their multiple possibilities. 



It becomes difficult, in the presence of such an 

 organization, to justify the classic dichotomy be- 

 tween the agonist and the antagonist muscles re- 

 quired by a rigid adherence to the principle of 

 reciprocal innervation. The only cases in which this 

 convenient distinction is justifiable are those of the 

 hinge joints. 



Every movement results from the cooperative 

 action of a number of muscles. "An isolated muscular 

 action does not exist in nature," exclaimed Duchenne 

 de Boulogne (28), observing foi the first time the 

 effects of 'localized electrization" in man and noting 

 the lack of gestural significance of the movements 

 produced by this method. 



Winslow (134) has the merit of having clearly ex- 

 pressed the necessity for complex cooperation of 

 muscles to "move a part of the body or to hold it in 

 a determined position." The analysis by this great 

 anatomist led him to propose a functional classifica- 

 tion of the divers muscles implicated in a particular 

 action, according to the nature of their participation. 



a) The 'principaux moteurs,' later named "prime 

 movers' by Beevor (9), which directly carry the 

 movement to the determined situation or attitude. 



b) The 'moderateurs' which moderate or counter- 

 balance the action of the former, Beevor's 'antag- 

 onists.' <) The 'directeurs' which stabilize the action 

 laterally. Beevor distinguished 'synergists' which 

 cooperate directly with the prime movers and 'fixers' 

 which stabilize the articulations involved. 



Forms of Expression 



It is to Duchenne de Boulogne (28) that we owe 

 the first precise description of certain basic motor 

 figures which underlie the execution of our move- 

 ments. He underlined the 'obligatory and impera- 

 tive' character of these 'instinctive reactions," which 

 are stereotypes embedded in the heritage of the 

 species and associated with the most habitual modes 

 of utilization of the organ of movement concerned. 

 We may cite as an example the synergic action of 



the fixing muscles of the proximal articulations of 

 the limbs, without the firmness of this rigid prop, the 

 delicate adjustments of the distal articulations could 

 not be efficiently effected. Clinical experience re- 

 veals that simple paralysis of the radial muscles 

 which contribute to the fixation of the wrist is suffi- 

 cient to interfere with the prehensile activity of the 

 fingers. 



The first electromyographic recordings were made 

 in the course of the investigations of Wachholder 

 (124) and of Altenburger (6). These workers have 

 made available a more refined method of analysis of 

 muscle patterning. Wachholder (124) insisted upon 

 rhythmic alternation of the activity of the antag- 

 onists as being, under optimal conditions, the most 

 economical form of activity. Altenburger has pro- 

 vided experiment.tl support for the hypothesis that 

 there is a preformed central structuring of the pattern 

 ol sy nergic activity . The quasisimultaneity of innerva- 

 tion of the diverse muscular groups would appear 

 to exclude the existence ol .1 reflex regulation origi- 

 nating in the contraction of the muscle moving 

 first (6 



The polygraphic electrophysiological methods 

 now available are well adapted to the study of the 

 patterns of muscular activity. They have revealed 

 tin- astonishing complexity of the organization of the 

 most simple acts. This is illustrated by the very 

 accurate work ol Tourn.n \ Fessard ni| at the 

 level of the motor unit which shows the extreme 

 subtlety of these synergic innervation patterns (see 

 figs 3, 4). To patterning of spatial distribution which 

 determines the participation and the degree of in- 

 tervention of the diverse muscles implicated in the 

 action is added an extremely complex patterning of 

 temporal succession. The kinetic melody' is organized 

 according to the sequences required by a most 

 precise orchestration which defines the participation 

 of each performer (see fig. 4). 



We must note here the necessity of avoiding the 

 common confusion of the prime mover, in the sense 

 used by Beevor (the 'principal moteur' of Winslow), 

 with the muscle moving first in the beginning of an 

 action. The analysis clearly reveals that the excita- 

 tion of a cooperating part often precedes in time the 

 excitation of the muscle primarily responsible for 

 the movement. 



The most significant fact revealed by this type of 

 analysis of muscular activity is the extreme fluidity 

 of the patterning of action, depending on the initial 

 posture of the segments and on the nature of the 

 resisting forces. The same final effect can be attained 



