Reliability of center of pressure excursion measurements in subjects with dissimiliar leg preference

Purpose. The purpose of this study was to determine the response stability of measurements used in the assessment of center of pressure excursion (COPe) during step initiation. A NeuroCom� Balance Master� was used to collect data relating to subjects center of pressure movements. With repeated trials, the variables of interest were compared, and the stability of these variables was assessed. The variables were also analyzed to assess the effects of foot dominance, height, and body weight on the response stability of repeated measurements of COPe. Subjects involved in this study were first tested to establish foot preference. Subjects. Seventeen volunteers, all "normal" adult university students aged 20-40, and displaying "strong" left or right foot preference on initial tests were divided into Group "L" (n=6) and Group "R" (n=11) respectively. Methods. Data were collected "during balanced stance" and during step initiation. Repeated trials were performed and the subjects' COPe was measured while stepping forward with both the dominant and the non-dominant foot. Numerous variables were used to measure and quantitatively describe the center of pressure excursion during step initiation. ANOVA was used to determine response stability of the COPe measurements for each subject, as well as between the two groups. Results. No significant within-subject variability was noted for all measurements of COPe that were examined in this study, suggesting that all measurements of COPe used demonstrated response stability and were not affected by repeated trials. There were few significant effects of foot dominance on the COP excursion measurements between subjects with dissimilar foot preferences. Results also revealed a significant effect of weight on only three, and height on only five measurements of COPe. Discussion. Based on the consistency and high degree of response stability of repeated measures, the investigators recommend the following three measurements of COPe for future studies: the greatest excursion of the COP laterally, the greatest excursion of the COP in the anteroposterior direction, and the angle (in degrees) from the x-axis at the (x,y)coordinate point with the greatest distance from the y-axis in the quadrant of interest. Conclusion. The most stable variables could provide a more empirical way of assessing center of pressure excursions during step initiation. Insights gained could serve as a reference when attempting to identify and overcome step initiation problems. Establishment of the most reliable COPe measurements may provide future studies the tools needed to empirically analyze differences in COPe during step initiation. A larger study sample needs to be done in order to confirm this pilot study.