Figure 3. Quantification of muscle activity patterns.

i–iii: Example of individually filtered, rectified and scaled EMG data (m. extensor carpi ulnaris (m. ECU), blue =  clockwise (CW), red =  counter clockwise (CCW); the scaled EMG data is indicated along the 75 degree axis. iv–v: Scaled EMG power was fitted to an ellipse (resulting in ‘EMG ellipse’); vi: By transforming the coordinates (X,Y) of the center of the EMG ellipse to polar coordinates, the parameters differentiated muscle activity (DiffAct) and angle at maximum activity were obtained (Angle_max). DiffAct and Angle_max were used to compare differentiated muscle use between groups, muscles and direction.