2007 Volume 19 Issue 1 Pages 57-63
The purpose of this study was to determine and verify a measuring and modeling technique for the center of gravity during manual wheelchair propulsion. Eight non-wheelchair users propelled themselves on linear flat floor and a slope (1/12) in four axle conditions. A three dimensional motion capture system and the force plates recorded static and dynamic trials of propulsion performance. Positions of the combined center of gravity of a wheelchair and the human body were calculated using a kinematic model. The positions of the center of gravity had a highly significant correlation with the positions of the center of pressure obtained from the force plate data in the anterior-posterior direction in static trials (r=0.99, p<.05), giving an average error (RMSE approximately 1.0). The minimal distance between the center of gravity and axle positions significantly decreased with axle position forwarded in propulsion on the floor (p<.05). Propulsion on the slope, however, demonstrated less significant differences of the distance between the center of gravity and axle positions. It implies that more dynamic activities lead to a variety of changes in the center of gravity. This method for determination of the center of gravity can be considered valid in static trials for wheelchair sitting and in dynamic trials on level ground during manual wheelchair propulsion.
