posted on 2010-01-28, 10:29authored byMickael Begon, Pierre-Brice Wieber, Fred Yeadon
To reduce the effects of skin movement artefacts and apparent joint dislocations in the kinematics
of whole body movement derived from marker locations, global optimisation procedures with a chain
model have been developed. These procedures can also be used to reduce the number of markers when
self-occlusions are hard to avoid. This paper assesses the kinematics precision of three marker sets:
16, 11 and 7 markers, for movements on high bar with straddled piked posture. A three-dimensional
person-specific chain model was defined with 9 parameters and 12 degrees of freedom and an iterative
procedure optimised the gymnast posture for each frame of the three marker sets. The time histories
of joint angles obtained from the reduced marker sets were compared with those from the 16 marker
set by means of a root mean square difference measure. Occlusions of medial markers fixed on the
lower limb occurred when the legs were together and the pelvis markers disappeared primarily during
the piked posture. Despite these occlusions, reconstruction was possible with 16, 11 and 7 markers.
The time histories of joint angles were similar; the main differences were for the thigh mediolateral
rotation and the knee flexion because the knee was close to full extension. When five markers were
removed, the average angles difference was about 3◦. This difference increased to 9◦ for the seven
marker set. It is concluded that kinematics of sports movement can be reconstructed using a chain
model and a global optimisation procedure for a reduced number of markers.
History
School
Sport, Exercise and Health Sciences
Citation
BEGON, M., WIEBER, P.B. and YEADON, M.R., 2008. Kinematics estimation of straddled movements on high bar from a limited number of skin markers using a chain model. Journal of Biomechanics, 41 (3), pp. 581-586.