An Interrupted Time Series Analysis Reveals Effects of Mechanical Perturbations on Gait Variability
Presenter Type
UNO Graduate Student (Masters)
Major/Field of Study
Biomechanics
Other
Biomechanics
Author ORCID Identifier
0000-0001-5630-2305
Advisor Information
alikens@unomaha.edu
Location
MBSC306 - G (Masters)
Presentation Type
Oral Presentation
Start Date
24-3-2023 2:30 PM
End Date
24-3-2023 3:45 PM
Abstract
Improving gait control and preventing falls in various clinical populations demands accessible and user-friendly technology. A promising candidate are metronomes used to pace human gait. By varying the interbeat intervals between two metronome beats, their statistical properties can be aligned with the inherent variability in young healthy gait. Gait events produce a property called pink noise—events related to one another over time—that reflect adaptability and resilience to perturbations. Age and disease diminish in correlation among gait events, tending towards randomness (white noise). Most studies rely on isochronous metronomes with equally spaced cues. That practice is questionable because such metronomes contradict fundamental features of healthy human movement variability. In contrast, research using pink noise metronomes shows that gait variability can be restored in clinical populations. An open question remains on whether walking with pink noise has the capacity to better adapt to perturbations as well. We investigate this hypothesis by enforcing subjects to walk to auditory cues of variable metronomes and assessing the relative resilience to a perturbation. 30 young healthy adults performed 2 walking trials on a split-belt treadmill. After a 25-minute baseline walk, they completed 1 of 4 walking conditions, lasting 45 minutes: No metronome, Isochronous, Pink Noise, Random. Participants were instructed to coordinate their steps to the metronome. At minute 25, the treadmill belt of the dominant leg was halted to introduce an unexpected perturbation. Whole-body kinematics were captured with a Vicon Nexus motion capture system (Sampling Rate = 100Hz). We extracted the dominant leg stride interval time series for each trial and computed the Hurst exponent (a measure of temporal correlation) in windows of 167 s for each trial. Then, we performed an interrupted time series analysis to understand how the Hurst exponent (a measure of temporal correlation) changed throughout the trial, with particular focus on the perturbation period. Our preliminary analysis revealed several trends. First, we replicated known trends in the literature where Pink Noise produced a larger Hurst exponent than all other conditions. Second, we found that, regardless of condition, the perturbation increased the Hurst exponent (p < .001). Lastly, we found that while prior to perturbation, the Hurst exponent was relatively constant, the Hurst exponent tended to decrease after perturbation, regardless of condition (p
Scheduling
9:15-10:30 a.m., 10:45 a.m.-Noon, 1-2:15 p.m., 2:30 -3:45 p.m.
An Interrupted Time Series Analysis Reveals Effects of Mechanical Perturbations on Gait Variability
MBSC306 - G (Masters)
Improving gait control and preventing falls in various clinical populations demands accessible and user-friendly technology. A promising candidate are metronomes used to pace human gait. By varying the interbeat intervals between two metronome beats, their statistical properties can be aligned with the inherent variability in young healthy gait. Gait events produce a property called pink noise—events related to one another over time—that reflect adaptability and resilience to perturbations. Age and disease diminish in correlation among gait events, tending towards randomness (white noise). Most studies rely on isochronous metronomes with equally spaced cues. That practice is questionable because such metronomes contradict fundamental features of healthy human movement variability. In contrast, research using pink noise metronomes shows that gait variability can be restored in clinical populations. An open question remains on whether walking with pink noise has the capacity to better adapt to perturbations as well. We investigate this hypothesis by enforcing subjects to walk to auditory cues of variable metronomes and assessing the relative resilience to a perturbation. 30 young healthy adults performed 2 walking trials on a split-belt treadmill. After a 25-minute baseline walk, they completed 1 of 4 walking conditions, lasting 45 minutes: No metronome, Isochronous, Pink Noise, Random. Participants were instructed to coordinate their steps to the metronome. At minute 25, the treadmill belt of the dominant leg was halted to introduce an unexpected perturbation. Whole-body kinematics were captured with a Vicon Nexus motion capture system (Sampling Rate = 100Hz). We extracted the dominant leg stride interval time series for each trial and computed the Hurst exponent (a measure of temporal correlation) in windows of 167 s for each trial. Then, we performed an interrupted time series analysis to understand how the Hurst exponent (a measure of temporal correlation) changed throughout the trial, with particular focus on the perturbation period. Our preliminary analysis revealed several trends. First, we replicated known trends in the literature where Pink Noise produced a larger Hurst exponent than all other conditions. Second, we found that, regardless of condition, the perturbation increased the Hurst exponent (p < .001). Lastly, we found that while prior to perturbation, the Hurst exponent was relatively constant, the Hurst exponent tended to decrease after perturbation, regardless of condition (p