Effects of the performance parameters of a wheelchair on the changes in the position of the centre of gravity of the human body in dynamic condition.

The research carried out shows that the inclination angle of the wheelchair has the greatest influence on position of the ellipse describing the position of the centre of gravity of the human body. By controlling the change in the inclination angle value in the range from 0° to 5.4°, the standard deviation of the length of the horizontal half-axis of the ellipse (SD a) equal to 31.2 mm was obtained. For comparison, by changing the frequency of pushes (40 to 50 pushes per minute) of the wheelchair at a constant inclination angle, the standard deviation of the horizontal half-axis length (SD a) equal to 8 mm was recorded. The results of the study show a change in the position of the centre of gravity of the human body in dynamic conditions. They are relative to the contact points of the wheelchair wheels with the ground. Using the dimensions of the plotted ellipses, one can determine the values of pressure that affect the wheelchair's individual wheels. Conclusions-Increasing the value of each aforementioned parameter resulted in the increase of strength required by the operator to propel the wheelchair. It directly influenced the position of the centre of gravity during the test.