INFLUENCE OF DIRECTION ON RAPIDITY OF BILATERAL ARM MOVEMENTS

An experimental study of the influence of direction on the rapidity of repetitive bilateral arm movements was undertaken in 20 healthy right-handed subjects. The test situation required the subjects to tap alternately with a metal stylus held in each hand. The results confirm previous observations indicating that repetitive movements of the right arm are faster than those of the left. They also show that the direction in which the movements are made influences the rapidity of performance with the left but not with the right arm, left arm movements being faster in the antero-posterior than in the latero-medial plane. The findings further reveal that bilateral movements performed with the two arms together are significantly slower than the same movements performed by either arm alone, the extent of this slowing depending upon the direction in which the bilateral movements are made. Thus, the reduction in the rapidity of movement is least with identical antero-posterior movements, followed by latero-medial movements directed towards and away from the midline of the body. Left-right latero-medial movements, and alternating antero-posterior movements, are associated with the maximum reduction in the rapidity of movement. Some theoretical interpretations of the findings are discussed. © 1969.