Generalizability of Center of Pressure measurements across age populations

Abstract

The reliability of common Center of Pressure (COP) measurements was systematically investigated. Studies on the control of posture during quiet standing using force platform data lack standardization in measurement protocols (especially trial length and number). Guidelines for methodology that met acceptable reliability levels were established in both normal and altered visual conditions (Studies 1 and 2) and across multiple age populations (Study 3). The tools of Generalizability Theory (G-Theory) were used to thoroughly examine the reliability of both summary and time-varying measurements of COP. G-Theory is a powerful reliability analysis tool that permits the systematic inspection of identified components of variance (i.e. length of trial and number of trials) and subsequently provides feedback on establishing protocols meeting acceptable levels of reliability. The results of all three studies indicate that, when investigating quiet standing using COP measurements from a force platform, a minimum of 5 trials should be completed at 60 seconds in length. Most measurements included in these studies reached acceptable levels of reliability at or before this point. Reliability is a critical component of research design and the guidelines established in these studies can be used when designing future studies.