Ballistic muscle mechanisms determined using an EMG-driven model.

Abstract

The purpose of this study was to determine the mechanisms responsible for improving ballistic elbow extension. In doing so, an electromyography (EMG)-driven model was developed to predict the actual triceps torque so that the model parameters between subjects could be compared. Thirty-two subjects performed maximum isometric trials at 60 degrees , 90 degrees and 120 degrees of elbow extension to determine torque-angle relations. Dynamic elbow extension trials were then performed against relative loads of 0%, 20%, 40%, 60% and 80% and absolute loads of 1.1 and 2.2 kg. These trials were used to determine the torque-angular velocity relation for each subject. The model predicted the triceps torque during the unloaded, 1.1 and 2.2 kg trials with an average r = 0.964 and an average root mean square error of 4.34 Nm. As a result of the good predictions, a forward dynamics approach was used to substitute different neuro-muscular mechanisms of a poor performance with those from an individual that displayed a superior performance. Performance was shown to improve when these modifications were made. Therefore, the EMG-driven model was capable of modeling the actual muscle torque which allowed for the identification of areas of weakness of a poor performance. A prescription for improvement was identified, albeit artificially, on an individual basis. The next stage is to determine which specific interventions can accomplish those theoretically proposed.