Date of Award
Doctor of Philosophy
Analysis of the relationship between movement kinematics and muscle activity is a widely used approach for understanding how the nervous system formulates motor commands to produce movements. In planar single joint movements, phasic muscle activity is highly correlated with specific kinematic variables. Such correlations have not proven to be as direct in complex movements. The rules used by the nervous system in movement coordination are thus poorly understood. The purpose of this study was first, to examine kinematics, dynamics and electromyographic (EMG) activity during single and two-joint arm movements to discern the common planning strategies between these movements; and second, to gain insight into the variables used in planning complex movements.;In single joint movements made in the vertical plane, all movements were characterized by time symmetric velocity profiles. Gravitational loading directly influenced muscle activity. This suggests that basic patterns of muscle activation are modulated in relation to external forces. In two-joint planar movements involving the wrist and elbow joints, the selection of muscle activation patterns at the wrist was dependent on the relative magnitude and direction of elbow reaction torques, in relation to wrist motion. Elbow joint movement is therefore an important consideration in planning wrist movement. The details of the actual wrist trajectory may not be specifically planned, but emerges from the integration of basic patterns of activity with the dynamic interaction between joints.;The influence of visual feedback information on movement coordination was also examined. Visual feedback of the endpoint targets as well as the subject's endpoint limb position, were presented in a range of concrete to abstract representations. Changes were observed in the timing relationship between the two joints, and in the EMG patterns, in relation to visual feedback conditions.;Thus, in selecting the level and pattern of muscle activity of the distal joint during a two-joint movement, the nervous system requires information about the amplitude of the desired distal movement, and the magnitude and direction of acceleration of the proximal joint. Inter-joint coordination will further be influenced by the nature of visual feedback information.
Virji-Babul, Naznin, "Programming Of Muscle Activity In Arm Movements In Relation To Force Requirements" (1995). Digitized Theses. 2581.