Validation of Different Filters for Center of Pressure Measurements by a Cross-Section Study

Abstract

The measurement of the center of pressure (CoP) is one of the most frequently used quantitative methods for quantifying postural performance. Due to the complexity and the high biological variability of the postural control loop, a large number of different methods and parameters have been established to describe the CoP process. Furthermore, the methodological conditions such as the foot position, visual condition, sampling duration, and the data processing also have a relevant influence on the measurement results. In addition, there are various methods for recording the pressure curve, which differ in particular with regard to the filters used, the frequencies, and measurement times. The aim of the present study was the methodical comparison between different digital filters, measurement frequencies and times, and their effects on the CoP process based on a healthy reference group. The data acquisition was done with LabVIEW and the data storage was organized in a subject oriented data structure. Based on the presented results it could be seen that with a different dominant frequency in the spectrum of the group of test persons, certain filter types are required for the processing of CoP data. In the sampling range from 300 Hz to 1 kHz in the bipedal stand and 600 Hz to 1 kHz in the monopedal stand, the choice of measurement frequency had no influence on the filter result.

Evaluation of Postural Sway in Post-stroke Patients by Dynamic Time Warping Clustering

“…Frequency was not significantly different in the post-hoc test, but we found that the frequency of postural sway fell in 0.5–1.5 Hz for COM, and from cluster 3, CH subjects of lower age and lower days after onset kept their sway frequencies within 0.6–0.7 Hz. A previous researcher found that frequency of body sway fell in the range of 0.1–0.2 Hz (Koltermann et al, 2019 ), and because they also found that post-stroke increases sway frequency (Mizrahi et al, 1989 ), our finding was found to be reasonable.…”

The Influence of Anthropometric Variables and Filtering Frequency on Center of Pressure Data

“…The cut-off frequency for the Butterworth filter was calculated according to Koltermann et al ( 2019) [18]. To determine the cut-off frequency, an averaged PSD spectrum was calculated from all measurements.…”

Portable electronic device to assess the human balance using a minimum number of sensors

“…Thus, this work demonstrate how is possible to assess the CoP using only two low cost and widely available sensors. As a result from above, the values obtained using the presented system could not be directly compared with valued obtained using force platforms, however, actually the indexes values of balance are quite variable among subjects, so there not exist a common range of values widely accepted by the community as the standard values (Koltermann et al 2019), instead, the balance tests are carried out testing the subject under different conditions and evaluating the difference. Thus, the proposed system allows, due to the portability and low cost, to be implemented and used in small clinics, rehabilitation offices or places were the patients usually develop their life, without the necessity to move to a specialized laboratories with force platforms or stabilometers.…”

“…Due to the high variability inter and intra subject, as well as the variability on the devices used to measure the CoP and the lack of standards on the test conditions (Tamburella et al 2014), it has been not possible to reach an agreement on the standardization for the values of the indexes (Cornilleau-Pérès et al 2005)), (van der Kooij et al 2011), (Janusz et al 2016) (Koltermann et al 2019). For this reason, is not possible to compare the values obtained by a given subject to a universal standard.…”