Figure 4. Hand Placement and Grip Force Measurement.

For each subject, the metacarpophalangeal joints were aligned with the vertical gap between the proximal instrumented beam and the reference beam on the handle to ensure consistent hand placement for calculation of vertical centres of pressure. Components of grip force are measured by proximal and distal instrumented beams (Step 1). Grip force is calculated after a series of vector additions (Steps 2-4). The origin of the force is located at the center of the instrumented (fingers) and reference (thumb) beams.