  Estimating the position of the whole-body centre of mass (CoM) based on skin
markers and anthropometric tables requires tracking the pelvis and lower body,
which is impossible for wheelchair users due to occlusion. In this work, we
present a method to track the user's whole-body CoM using visible markers
affixed to the user and wheelchair where the user remains seated in their
wheelchair, by expressing the pelvis and lower body segments in wheelchair
coordinates. The accuracy of this method was evaluated on the
anterior-posterior (AP) and medial-lateral (ML) axes by comparing the projected
CoM to the centre of pressure measured by four force plates, for 11 able-bodied
participants adopting 9 static postures that include extreme reaching postures.
The estimation accuracy was within 33 mm (AP) and 9 mm (ML), with a precision
within 23 mm (AP) and 12 mm (ML). Tracking the whole-body CoM during wheelchair
propulsion will allow researchers to better understand the dynamics of
propulsion, which may help devise new approaches to increase the energy
transfer from the arms to the ground and reduce the risks of developing
musculoskeletal disorders.
