Reliability and validity of the protokinetics movement analysis software in measuring center of pressure during walking

Abstract

Our purpose was to determine the validity and test-retest reliability of the Protokinetics Movement Analysis Software (PKMAS) in measuring center of pressure (COP) during walking as compared to a force plate gold standard. Twenty-five healthy participants (14 females, 11 males; age 20.0±1.5years) completed 2 testing sessions approximately 5days apart (mean=5.5±1.1 days). In each session, participants completed 16 total trials across a 6m walkway: 8 trials walking on a ProtoKinetics Zeno Walkway using PKMAS and 8 trials walking over 2 force plates arranged in an offset tandem pattern. COP path length (cm) and speed (cm/s) were calculated from data averaged across the 8 trials on a given device for a given foot. Intraclass correlation coefficients (ICC 2, k) were computed to determine between session reliability. Pearson correlation coefficients (r) and Bland-Altman plots were produced between the PKMAS and force plate outcomes for session 1 to determine validity. The PKMAS demonstrated excellent reliability (ICC 2, k≥0.962) for all COP measures. Pearson correlation coefficients between PKMAS and force plates were ≥0.75 for all outcome variables. Bland-Altman plots and 95% levels of agreement revealed a bias where the PKMAS appeared to underestimate COP path length and speed by approximately 4cm and 6cm/s, respectively. After correcting for bias, our findings suggest the PKMAS is a reliable tool to measure COP in healthy people during gait. Using the PKMAS with the ProtoKinetics Zeno Walkway may allow for more efficient investigation of dynamic balance variables during functional movement tasks.