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

Koltermann, Jan Jens; Gerber, Martin; Beck, Heidrun; Beck, Michael

doi:10.3390/technologies7040068

Cited by 4 publications

(2 citation statements)

References 16 publications

(39 reference statements)

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“…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.…”

Section: Discussionsupporting

confidence: 82%

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

Kaminishi

Takakusaki³

et al. 2021

Front. Hum. Neurosci.

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Post-stroke complications are the second most frequent cause of death and the third leading cause of disability worldwide. The motor function of post-stroke patients is often assessed by measuring the postural sway in the patients during quiet standing, based on sway measures, such as sway area and velocity, which are obtained from temporal variations of the center of pressure. However, such approaches to establish a relationship between the sway measures and patients' demographic factors have hardly been successful (e.g., days after onset). This study instead evaluates the postural sway features of post-stroke patients using the clustering method of machine learning. First, we collected the stroke patients' multi-variable motion-capture standing-posture data and processed them into t s long data slots. Then, we clustered the t-s data slots into K cluster groups using the dynamic-time-warping partition-around-medoid (DTW-PAM) method. The DTW measures the similarity between two temporal sequences that may vary in speed, whereas PAM identifies the centroids for the DTW clustering method. Finally, we used a post-hoc test and found that the sway amplitudes of markers in the shoulder, hip, knee, and center-of-mass are more important than their sway frequencies. We separately plotted the marker amplitudes and frequencies in the medial-lateral direction during a 5-s data slot and found that the post-stroke patients' postural sway frequency lay within the bandwidth of 0.5–1.5 Hz. Additionally, with an increase in the onset days, the cluster index of cerebral hemorrhage patients gradually transits in a four-cluster solution. However, the cerebral infarction patients did not exhibit such pronounced transitions over time. Moreover, we found that the postural-sway amplitude increased in clusters 1, 3, and 4. However, the amplitude of cluster 2 did not follow this pattern, owing to age effects related to the postural sway changes with age. A rehabilitation doctor can utilize these findings as guidelines to direct the post-stroke patient training.

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Section: Discussionsupporting

confidence: 82%

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

Kaminishi

Takakusaki³

et al. 2021

Front. Hum. Neurosci.

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“…The data was filtered with a Butterworth filter of the 3rd order with a cut-off frequency of 14.3 Hz. The filter was designed according to Koltermann et al, 2019 [17].…”

Section: Statisticmentioning

confidence: 99%

Quantification of the Dependence of the Measurement Error on the Quantization of the A/D Converter for Center of Pressure Measurements

Koltermann

Gerber²

2022

Biomechanics

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In this scientific study, the question of the influence of the quantization error on the CoP measurement is be clarified. For this purpose, the quantization error is investigated in two scenarios, first with the technical/physical reproduction of the CoP, and then with test persons. From the results, a model is derived with which a technical and economic optimum between resolution and error can be generated for an individual case. The study was carried out with 170 healthy volunteers, aged 20–30 years. The test persons stood in a bipedal position for 15 s on a Kislter force plate (type 9260AA). In the investigation, it was shown that, for the measurement of center of pressure (CoP), signals to mostly 16-bit analog/digital converters are suitable but not, per se, the most economical variant. With the introduction of a quality criterion, a reasonable design for the planned test case can be made.

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

Cited by 4 publications

References 16 publications

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

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

Quantification of the Dependence of the Measurement Error on the Quantization of the A/D Converter for Center of Pressure Measurements

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