The Path of Center of Pressure(COP) of the Foot during Walking

Paik, Nam Jong; Im, Min Sik

Abstract

Variations in the distribution and the magnitude of the forces in the foot may reflect painful conditions and abnormalities of structure or function. By tracking the path of the instantaneous COP(center of pressure) during stance phase, the balance and pattern of progression can be determined, but parameters on COP have not been standardized nor widely applied to clinical settings yet. To quantify the COP parameters and to evaluate the clinical applicability of COP, within subject experimental design was used. Twenty six subjects with age of sixties who had no history of foot problems were recruited. Foot contact and COP parameters were measured and compared between flat foot, low heel and high heel shod walking. 1) Gait cycle parameters, 2) foot contact parameters such as total contact area, contact length, contact width, and 3) COP parameters such as initial contact COP, mean COP, anteroposterior and mediolateral displacement of COP, slope of COP, velocity of COP during each functional rocker were measured with F-scan pressure sensitive insole system. In normal flat foot walking, COP of initial contact and mean COP were anatomically correspond to the center of the heel and to the center of the sole respectively. COP displacements corresponded to 83% of foot contact length anteroposteriorly and 18% of forefoot contact width mediolaterally. Slope of COP was about 6 degrees inwardly directed. Velocities of the COP during each functional rocker action were even and about 22-27 cm/sec around. In high heel shod walking, COP of initial contact was displaced 1.73 cm anteriorly and mean COP was displaced 0.31 cm medially and 1.89 cm anteriorly. Anteroposterior displacement of COP was also reduced. Velocity of the COP during heel rocker was faster and velocity during ankle rocker was slower compared to flat foot walking, which suggests excessive heel rocker and reduced ankle rocker action in high heel shod walking. In conclusion, COP parameters measured by pressure sensitive insole system may reflect the biomechanical alteration of the foot quantitatively and may be useful in assessing the biomechanical function of the foot.