Congratulations to Keshia Peters for receiving the College of Engineering’s Professional Staff Award!

Darrin Howell Awards, News

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Congratulations to Keshia Peters for receiving the College of Engineering’s Professional staff award! Keshia’s dedication to excellence and her commitment to seeing the goals of this lab realized are evident in the ways in which she both diligently leads her own projects and supports the research efforts of all of the other teams of the lab.

Here are just a few of the ways in which Keshia has and is making in impact in the Ability and Innovation Lab:
coordinating with collaborators at Gillette Children’s Specialty Healthcare (St. Pual, MN) and KU Leuven (Leuven, Belgium) to facilitate collaboration and improve data collection and management procedures; mentoring teams of undergraduate students on capstone and research projects; managing day-to-day lab activities and providing research support as a technician and IRB guru; playing a major role in the setup of our new collaborative lab space (AMP Lab); conducting her own research projects (to be presented at the 2017 ASB Conference in August!); acting as a first contact to introduce interested school and community groups to the work ongoing in our lab.
 
Thanks again for all that you do for us, Keshia. Your recognition is well deserved!

Praise for our undergraduates at the Mary Gates Undergraduate Research Symposium

Darrin Howell News, Presentation, Publications

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.

 

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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

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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.

AExample data from a representative TD participant. Left: EMG data processed with varying LP filter cutoffs. Center: Synergy weights and activations. Right: Total variance accounted for by n synergies. Total variance accounted for 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.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.

KM Steele, RW Jackson, BR Shuman, SH Collins (2017) “Muscle recruitment and coordination with an ankle exoskeleton.” Journal of Biomechanics

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KM Steele, RW Jackson, BR Shuman, SH Collins (2017) “Muscle recruitment and coordination with an ankle exoskeleton.” Journal of Biomechanics

Journal article in Journal of Biomechanics:

How do muscle activations and synergies change when an individual wears an ankle exoskeleton during gait?

Abstract: Exoskeletons have the potential to assist and augment human performance. Understanding how users adapt their movement and neuromuscular control in response to external assistance is important to inform the design of these devices. The aim of this research was to evaluate changes in muscle recruitment and coordination for ten unimpaired individuals walking with an ankle exoskeleton. We evaluated changes in the activity of individual muscles, cocontraction levels, and synergistic patterns of muscle coordination with increasing exoskeleton work and torque. Participants were able to selectively reduce activity of the ankle plantarflexors with increasing exoskeleton assistance. Increasing exoskeleton net work resulted in greater reductions in muscle activity than increasing exoskeleton torque. Patterns of muscle coordination were not restricted or constrained to synergistic patterns observed during unassisted walking. While three synergies could describe nearly 95% of the variance in electromyography data during unassisted walking, these same synergies could describe only 85–90% of the variance in muscle activity while walking with the exoskeleton. Synergies calculated with the exoskeleton demonstrated greater changes in synergy weights with increasing exoskeleton work versus greater changes in synergy activations with increasing exoskeleton torque. These results support the theory that unimpaired individuals do not exclusively use central pattern generators or other low-level building blocks to coordinate muscle activity, especially when learning a new task or adapting to external assistance, and demonstrate the potential for using exoskeletons to modulate muscle recruitment and coordination patterns for rehabilitation or performance.Synergy structure and activations had minimal changes with increasing exoskeleton torque.