Using Simultaneous Confidence Bands to Calculate the Margin of Error in Estimating Typical Biomechanical Waveforms

in Journal of Applied Biomechanics

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William Anderst Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA

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Shaquille Charles Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA
School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA

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Milad Zarei Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA

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Ashika Mani Department of Biostatistics, University of Pittsburgh, Pittsburgh, PA, USA

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Naomi Frankston Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA

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Elliott Hammersley Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA

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Gehui Zhang Department of Biostatistics, University of Pittsburgh, Pittsburgh, PA, USA

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MaCalus Hogan Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA
Foot and Ankle Injury Research (F.A.I.R.) Group, Pittsburgh, PA, USA

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Robert T. Krafty Department of Biostatistics and Bioinformatics, Emory University, Atlanta, GA, USA

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DOI:
https://doi.org/10.1123/jab.2021-0326
Keywords:
human movement variability; number of trials; reproducibility; reliability
First Published Online:
06 Jul 2022
In Print:
Volume 38: Issue 4
Page Range:
232–236
Restricted access

Studies of human movement usually collect data from multiple repetitions of a task and use the average of all movement trials to approximate the typical kinematics or kinetics pattern for each individual. Few studies report the expected accuracy of these estimated mean kinematics or kinetics waveforms for each individual. The purpose of this study is to demonstrate how simultaneous confidence bands, which is an approach to quantify uncertainty across an entire waveform based on limited data, can be used to calculate margin of error (MOE) for waveforms. Bilateral plantar pressure data were collected from 70 participants as they walked over 4 surfaces for an average of at least 300 steps per surface. The relationship between MOE and the number of steps included in the analysis was calculated using simultaneous confidence bands, and 3 methods commonly used for pointwise estimates: intraclass correlation, sequential averaging, and T-based MOE. The conventional pointwise approaches underestimated the number of trials required to estimate biomechanical waveforms within a desired MOE. Simultaneous confidence bands are an objective approach to more accurately estimate the relationship between the number of trials collected and the MOE in estimating typical biomechanical waveforms.

Anderst (anderst@pitt.edu) is corresponding author.

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