Measurement and Analyses of Force Plate Accuracy and Noise for a Computer Assisted Rehabilitation Environment (CAREN)

Abstract : Naval Health Research Center (NHRC) in San Diego houses a Computer Assisted Rehabilitation Environment (CAREN) used for rehabilitation and research of the warfighter. The CAREN system, equipped with a Forcelink treadmill and force plates, experiences variable force plate noise that can change between days and with a slight dependence on the weight placed on the device. The noise affects various applications and prevents consistent controls and accurate data recording. In order to understand the effect that noise has on the system and in CAREN applications, various weights were placed on the platform in multiple 3-second-long trials. The resulting force, center of pressure, and marker data were compared across several weights over multiple days. These data were also compared with another CAREN located at Walter Reed National Military Medical Center (WRNMMC) and with standard in-ground AMTI force plates at Naval Medical Center San Diego (NMCSD) to determine if the noise is only a local effect on the NHRC CAREN. It was determined that the NHRC CAREN and the WRNMMC CAREN experience the same amount of noise, which is much higher than the noise experienced by standard in-ground AMTI force plates such as those at NMCSD. It is recommended that all force and center of pressure data used by CAREN applications be first run through a filter before being used in a task, and that using low-force recordings be used cautiously or avoided entirely.