Gait speed and gender effects on center of pressure progression during normal walking.

The COP progression is the trajectory of the center of foot pressure. Thirty healthy young adults were recruited to participate in this study. All subjects were asked to walk randomly at four different speeds (3km/h, preferred walking speed, 4km/h and 5km/h). A foot pressure measurement system (RS-scan(®) system) was used to collect the center of pressure (COP) coordinates, COP progression angle and the COP velocity. Four sub-phases of the stance phase were calculated. The initial contact (ICP) and forefoot contact phase (FFCP) corresponded to the loading response. The foot flat phase (FFP) coincided with the mid-stance. The forefoot push-off phase (FFPOP) corresponded to the terminal stance and pre-swing phases. The results of this study indicate that the percentage of time (% time) of COP progression on the ICP, FFCP, FFP and FFPOP were approximately 7.0%, 4.8%, 48.8% and 39.4%, respectively. The COP progression angle was 4.1 (SD=1.6)° with an inward curve and the average COP velocity was 31.6cm/s (SD=5.3). The walking speed influenced the % time in the FFP and FFPOP. As the walking speed increased, the % time of COP progression decreased in mid-stance and increased in the terminal and pre-swing stances. Moreover, gender affected the COP progression angle. Men had a significantly larger deviating angle than women during FFCP, FFP and FFPOP. The COP characteristics can offer useful information for clinical rehabilitation in foot functional and structural evaluation.