On Conditions Affecting the Maximal Rate of Voluntary Extensor and Flexor Movements of the Right Arm

Abstract

Experiments on the maximal rate of extensor and flexor movements of both arms in various classes of persons have been for some time in progress at the Laboratory of Psychology of the University of Pennsylvania. The results of this investigation, when published, will contribute material bearing on differences in maximal rate of movement for race, sex, for the right and left arms, and for extension and flexion. In the course of this enquiry several factors have appeared to exert a determining influence upon the rate of these movements. Not only are such general factors as practice and fatigue effective in modifying the rate but the position of the subject with reference to the instruments, his mental attitude toward the investigation, the stimulation which he receives from the directions of the experimenter, the direction of his attention to the various parts of the movement; all these and other factors from time to time are observed to affect the rate of movement of some or all subjects. This monograph proposes to subject to the analysis of the experimental method certain of these factors that determine the maximal rate of voluntary movement. Its scope is restricted to an examination of certain conditions affecting the initial and preparatory stage of movements of maximal rate, i. e., those in which the volitional element is at a maximum. For the purposes of this investigation I have employed extensor and flexor movements of the right arm. It would be imposible within the limits of an inquiry of moderate proportions even to begin an examination of all the influences that probably have a share in the production of these movements. The factors with which I shall be concerned in this monograph are: I. Various extents of running start; 2. The mean variations of the average rate of movement; 3. The back pressure or the backward start, i. e., a pressure of variable amount exerted by the hand and arm against the post from which the movement is started; 4. The duration of the back pressure or backward start; JOURNAL-7