Appendix e-4
Methods
Total Overflow – Goniometer Analysis
The goniometers were positioned to only measure angular deviations of the metacarpophalangeal (MCP) joint of the index and rings fingers and were secured by adhesive tape and a Velcro strap around the wrist. Special care was taken to ensure each subject’s finger movements faced minimal resistance from the equipment. For each subject, the goniometers were calibrated at 0 and 45 degrees. Subjects placed each hand on the flat surface of a wooden block to calibrate at zero degrees. They then placed each hand on an edge of the wooden block cut at a 45 degree angle such that their fingers made a 45 degree angle about the MCP joint.
The data were amplified (Biopac MP100 system) and sampled at 100 Hz. During acquisition, the data were viewed using Biopac AcqKnowledge software 3.9.1v (Biopac Systems Inc., Goleta, CA). Total overflow was calculated off line as the total angular finger displacement from the baseline readings of the non-tapping hand.The data file for each block of finger-tappinghad four signal channels representing the angular position in degrees of the left and right index and ring fingers about the MCP joint.
Each data file was manually synchronized with the corresponding video clip in AcqKnowledge by time shifting the video clip such that the first finger-tap (index-thumb) in the video corresponded to the peak of the first tap in the index finger channel recording. Using the synchronized video as a reference, the time corresponding to the movement-free baseline data recording, the time of the first tap, and the time of completion of 40 taps in the data and video files were noted. A fixed number of 40 taps on video and goniometer was used; some subjects double-tapped some fingers or missed some fingers in the fixed sequence.
To remove high-frequency artifacts, the data was initially smoothed in AcqKnowledge using a built-in function that estimated each data point as the mean value of a 10 point moving window. Further analysis was performed using MATLAB (The Mathworks, Inc., Natick, Massachusetts). The mean of the baseline data corresponding to the index and ring fingers of the non-tapping hand were calculated. The baseline mean values were subtracted from data recorded during the 40-tap time interval. To equally account for finger flexions (positive deflections) and extensions (negative deflections), the absolute values were used. These values were summed resulting in total displacement values corresponding to the ring and the index fingers.