Unification of the PFA and COP for wheelchair propulsion

The interface between the hand and pushrim may have considerable effect on many of the models related to wheelchair propulsion biomechanics. This has led to investigation of the center of pressure (COP), and the development of a new metric called the point of force application (PFA). The center of pressure is a virtual point of forces application which accounts for the measured forces and moments at the sensor. The point of force application (PFA) represents the weighted geometric mean of the distributed force. This simple proof shows that the PFA is equivalent to the COP in the sagittal plane, provided that the assumptions are valid. This case may be described as the “force platform equivalent” COP as the PFA makes the same assumptions and the resultant equations are of the same form