Pendulum model to compare center of pressure data between different force plates.

Background: Force plates are used to measure postural control. However, force plates differ with regard to the type of sensors and the position of the sensors. The purpose of the study was to introduce a method for testing the comparability of two force plates with different force transducers regarding their center of pressure (CoP) capturing.

Methods: Two portable force plates (Kistler Model 9260AA vs. AMTI AccuSway-Optimized ACS-O) were compared. To produce repeatable, close to identical CoP data, a two-point suspension pendulum was used. The deflection angle of the pendulum was kept constant as well as the time of capturing the swing (30 s) and the frequency of capturing the data (1000 Hz). To test for comparability, the captured data was z-transformed and superimposed. Furthermore, interclass correlation coefficient (ICC) estimates, and their 95 % confidence intervals (CI) were calculated.

Results And Significance: The ICC for the two tested force plates were "excellent" (x-axis: ICC = 0.990 (95 % CI [0.990-0.990]), y-axis: ICC = 0.987 (95 % CI [0.987-0.988])). Thus, the presented method with the two-point suspension pendulum generated repeatable and almost identical oscillations in the x- and y-axis to calculate the CoP.

Data Availability: Data will be made available on request.