Congratulation to Jessica Zistatsis who has been invited to present PlayGait at the Technology Transfer Session of the 2017 AOPA World Congress in Las Vegas, NV. Click here to read more on the AOPA conference.
Publications
KM Steele, BR Shuman, MH Schwartz (2017) “Crouch severity is a poor predictor of elevated oxygen consumption in cerebral palsy.” Journal of Biomechanics
Journal article in Journal of Biomechanics:
Does energy consumption during walking increase with crouch severity among children with cerebral palsy?
Abstract: Children with cerebral palsy (CP) expend more energy to walk compared to typically-developing peers. One of the most prevalent gait patterns among children with CP, crouch gait, is often singled out as especially exhausting. The dynamics of crouch gait increase external flexion moments and the demand on extensor muscles. This elevated demand is thought to dramatically increase energy expenditure. However, the impact of crouch severity on energy expenditure has not been investigated among children with CP. We evaluated oxygen consumption and gait kinematics for 573 children with bilateral CP. The average net nondimensional oxygen consumption during gait of the children with CP (0.18 ± 0.06) was 2.9 times that of speed-matched typically-developing peers. Crouch severity was only modestly related to oxygen consumption, with measures of knee flexion angle during gait explaining only 5–20% of the variability in oxygen consumption. While knee moment and muscle activity were moderately to strongly correlated with crouch severity (r2 = 0.13–0.73), these variables were only weakly correlated with oxygen consumption (r2 = 0.02–0.04). Thus, although the dynamics of crouch gait increased muscle demand, these effects did not directly result in elevated energy expenditure. In clinical gait analysis, assumptions about an individual’s energy expenditure should not be based upon kinematics or kinetics alone. Identifying patient-specific factors that contribute to increased energy expenditure may provide new pathways to improve gait for children with CP.
Students Present at NWBS 2017 and Michael Rosenberg named top PhD Presentation
Ben Shuman, Brianna Goodwin, Michael Rosenberg, and Jessica Zistatsis all presented at this year’s Northwest Biomechanics Symposium in Eugene, OR.
A special congratulations to Michael Rosenberg who won the award for the top PhD presentation at NWBS! 
Praise for our undergraduates at the Mary Gates Undergraduate Research Symposium
Congratulations to our undergraduates on their stellar poster session presentations at the Mary Gates Undergraduate Research Symposium! Karley Benoff and Jessy Ha can be seen here sharing their team’s latest design of their elbow-driven orthosis. This project, spearheaded by fellow mechanical engineering undergraduate, Bradley Watcher (not pictured), was inspired to augment the motor function of a young woman who suffers from neurological impairment.
Michael McConnell, one of the lab’s graduating seniors, can be seen here sharing his work with an interested student. Michael’s project investigated the effect of color and temperature on the material properties of PLA, the base material widely used in 3-D printing projects. Michael’s research suggests each color of PLA achieves its maximal tensile strength after being heated to a distinct “critical” temperature.
BR Shuman, MH Schwartz, KM Steele (2017) “Electromyography Data Processing Impacts Muscle Synergies during Gait for Unimpaired Children and Children with Cerebral Palsy.” Frontiers in Computational Neuroscience
Journal article in Frontiers in Computational Neuroscience:
Filtering parameters impact the results from muscle synergy analyses.
A
bstract: Muscle synergies calculated from electromyography (EMG) data identify weighted groups of muscles activated together during functional tasks. Research has shown that fewer synergies are required to describe EMG data of individuals with neurologic impairments. When considering potential clinical applications of synergies, understanding how EMG data processing impacts results and clinical interpretation is important. The aim of this study was to evaluate how EMG signal processing impacts synergy outputs during gait. We evaluated the impacts of two common processing steps for synergy analyses: low pass (LP) filtering and unit variance scaling. We evaluated EMG data collected during barefoot walking from five muscles of 113 children with cerebral palsy (CP) and 73 typically-developing (TD) children. We applied LP filters to the EMG data with cutoff frequencies ranging from 4 to 40 Hz (reflecting the range reported in prior synergy research). We also evaluated the impact of normalizing EMG amplitude by unit variance. We found that the total variance accounted for (tVAF) by a given number of synergies was sensitive to LP filter choice and decreased in both TD and CP groups with increasing LP cutoff frequency (e.g., 9.3 percentage points change for one synergy between 4 and 40 Hz). This change in tVAF can alter the number of synergies selected for further analyses. Normalizing tVAF to a z-score (e.g., dynamic motor control index during walking, walk-DMC) reduced sensitivity to LP cutoff. Unit variance scaling caused comparatively small changes in tVAF. Synergy weights and activations were impacted less than tVAF by LP filter choice and unit variance normalization. These results demonstrate that EMG signal processing methods impact outputs of synergy analysis and z-score based measures can assist in reporting and comparing results across studies and clinical centers.