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

Abstract

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.

A scoping review of human skeletal kinematics research using biplane radiography

“…These goals call for fewer trials and activities to be collected for each study participant. On the other hand, the need to characterize the typical movement pattern of an individual 52 (as opposed to the movement during a single trial), the desire to ensure capture of the full movement, and the desire to characterize movement under different loading conditions or activities of daily living may require several trials and activities to be collected. A consensus is needed regarding the optimal number of trials and activities to balance radiation exposure and data processing time versus data robustness and completeness.…”

Bone morphology features associated with knee kinematics may not be predictive of ACL elongation during high‐demand activities

“…Instead, the study focused on morphologic features commonly cited in the literature as associated with ACL injury risk. Third, Finally, the study evaluated the relationships between bone morphology and ACL elongation (or kinematics) at speciic instants of each movement, cautioning against extrapolation to other instants that were not statistically evaluated [1].…”

“…However, the values of LPTS in this study closely aligned with the previous reports on individuals with ACL injuries [17, 24, 27], suggesting a reasonable representation of the ACL elongation and LPTS association. Finally, the study evaluated the relationships between bone morphology and ACL elongation (or kinematics) at specific instants of each movement, cautioning against extrapolation to other instants that were not statistically evaluated [1].…”

How Many Trials Are Needed to Estimate Typical Lumbar Movement Patterns During Dynamic X-Ray Imaging?

“…In conclusion, this study applies a recently described methodology [32,33] to quantify intrasubject variability in intervertebral kinematics waveforms while performing functional lumbar movements. The simple yet comprehensive parameter of margin of uncertainty (MOU), as obtained with the Simultaneous Confidence Bands technique, provides the researcher an objective metric to determine the relationship between the number of trials collected and the accuracy of the typical waveform estimate, and to balance the need for minimizing radiation exposure from the data acquisition process with a requirement for meaningful, clinically relevant datasets.…”

“…The approach quantifies uncertainty in the estimate of the typical waveform based on limited trial data to enable simultaneous inferences on the whole waveform. The ability to assess a margin of uncertainty (MOU) for a typical waveform estimate with this approach, and a comparison to conventional pointwise approaches, was recently demonstrated for continuous time-series data involving plantar pressure during gait [33].…”