Figure 4.

Visualization of the coordinate system associated with the right shoulder used to normalize the parameters of the ellipse circumscribed on the trajectory of the right wrist from a 30 s observation. The unit of the system is the length of the analyzed limb, whereas the sense of the horizontal axis is oriented towards the body axis. The blue circle shows the possible range of motion used to normalize the value of the area of the ellipse circumscribed on the trajectory (orange). Minor and major axes are marked inside the ellipse.