Study of human motor control and task performance with circular constraints

Abstract

This thesis aims to investigate human motor control strategies. Curved constraints offer a unique opportunity to exploit forces of contact. A circular crank experiment using the MIT MANUS robot was designed in order to test how well subjects can follow a set of simple instructions to rotate the crank at various constant speeds. 10 subjects volunteered to participate in this experiment. Velocity, force, and EMG data were collected during four tasks: turning the crank at the subject's preferred or comfortable speed, turning the crank at a constant preferred speed, turning the crank at a constant preferred speed with a visual feedback display, and rotating the crank at three instructed speeds (slow, medium, and fast) with visual feedback. The coefficient of variation (CV) of the velocity for each trial was computed as a measure of performance. Statistical analysis showed that speed significantly affected CV but the direction of turning the crank, clockwise or counterclockwise, did not. The observation that CV increased as speed decreased, despite visual feedback, confirms previous studies showing that human motor control is more imprecise at slower speeds.