A comparison of two techniques for center of pressure measurements

Introduction: Force platforms and pressure-measuring insoles are the most common tools used for measuring center of pressure. Earlier studies to assess these instruments suffered from limited sample sizes or an inadequate range of participant foot sizes. The purpose of this study was to propose new methods to extract and calculate comparably accurate center of pressure for the Kistler (R) force platform and Medilogic (R) insoles. Methods: Center of pressure data were collected from 65 participants wearing pressure-measuring insoles (six different sizes). Participants walked over consecutive force platforms for three trials while wearing pressure-measuring insoles within socks. Onset force thresholds and center of pressure segment length thresholds were used to determine accurate center of pressure path length and width. A single step for each foot and trial was extracted from both instruments. Results: A strong correlation was observed between instruments in center of pressure length (4.12 +/- 6.72% difference, r = 0.74). Center of pressure width varied and was weakly correlated (-7.04 +/- 4.48% difference, r = 0.11). Conclusions: The results indicate that both instruments can measure center of pressure path length consistently and with comparable accuracy (differences < 10%). There were differences between instruments in measuring center of pressure path width, which were attributed to the limited number of sensors across the width of the insoles.