Electromyography Archives - Page 2 of 3 - Neuromechanics & Mobility Lab

AM Spomer, RZ Yan, MH Schwartz, KM Steele (2023) “Motor control complexity can be dynamically simplified during gait pattern exploration using motor control-based biofeedback”

Katie JournalArticle, MotorControl, News, Projects, Publications April 18, 2023June 12, 2024Bayesian additive regression trees, Biofeedback, Electromyography, EMG, Machine Learning, Motor Control, Muscle synergy

Journal Article in Journal of Neurophysiology

Understanding how the central nervous system coordinates diverse motor outputs has been a topic of extensive investigation. Although it is generally accepted that a small set of synergies underlies many common activities, such as walking, whether synergies are equally robust across a broader array of gait patterns or can be flexibly modified remains unclear.

Aim: The aim of this study was to characterize the robustness of synergies to changing biomechanical constraints during walking. Specifically, we evaluated the extent to which nondisabled individuals could modulate both synergy structure and complexity while using motor control biofeedback to drive broad gait pattern exploration.

Methods: We evaluated the extent to which synergies changed as nondisabled adults (n = 14) explored gait patterns using custom biofeedback. Secondarily, we used Bayesian additive regression trees to identify factors that were associated with synergy modulation.

Results: Participants explored 41.1 ± 8.0 gait patterns using biofeedback, during which synergy recruitment changed depending on the type and magnitude of gait pattern modification. Specifically, a consistent set of synergies was recruited to accommodate small deviations from baseline, but additional synergies emerged for larger gait changes. Synergy complexity was similarly modulated; complexity decreased for 82.6% of the attempted gait patterns, but distal gait mechanics were strongly associated with these changes. In particular, greater ankle dorsiflexion moments and knee flexion through stance, as well as greater knee extension moments at initial contact, corresponded to a reduction in synergy complexity.

Interpretation: Taken together, these results suggest that the central nervous system preferentially adopts a low-dimensional, largely invariant control strategy but can modify that strategy to produce diverse gait patterns. Beyond improving understanding of how synergies are recruited during gait, study outcomes may also help identify parameters that can be targeted with interventions to alter synergies and improve motor control after neurological injury.

New & Noteworthy: We used a motor control-based biofeedback system and machine learning to characterize the extent to which nondisabled adults can modulate synergies during gait pattern exploration. Results revealed that a small library of synergies underlies an array of gait patterns but that recruitment from this library changes as a function of the imposed biomechanical constraints. Our findings enhance understanding of the neural control of gait and may inform biofeedback strategies to improve synergy recruitment after neurological injury.

KM Steele, MH Schwartz (2022) “Causal Effects of Motor Control on Gait Kinematics After Orthopedic Surgery in Cerebral Palsy: A Machine-Learning Approach”

Katie JournalArticle, MotorControl, News, Publications June 3, 2022June 11, 2024Cerebral Palsy, Electromyography, EMG, Gait, Machine Learning, Motor Control, Spasticity

Journal Article in Frontiers in Human Neuroscience

Altered motor control is common in cerebral palsy (CP). Understanding how altered motor control affects movement and treatment outcomes is important but challenging due to complex interactions with other neuromuscular impairments. While regression can be used to examine associations between impairments and movement, causal modeling provides a mathematical framework to specify assumed causal relationships, identify covariates that may introduce bias, and test model plausibility.

Aim: The goal of this research was to quantify the causal effects of altered motor control and other impairments on gait, before and after single-event multi-level orthopedic surgery (SEMLS).

Methods: We evaluated the impact of SEMLS on change in Gait Deviation Index (ΔGDI) between gait analyses. We constructed our causal model with a Directed Acyclic Graph that included the assumed causal relationships between SEMLS, ΔGDI, baseline GDI (GDIpre), baseline neurologic and orthopedic impairments (Imppre), age, and surgical history. We identified the adjustment set to evaluate the causal effect of SEMLS on ΔGDI and the impact of Imppre on ΔGDI and GDIpre. We used Bayesian Additive Regression Trees (BART) and accumulated local effects to assess relative effects.

Results: We prospectively recruited a cohort of children with bilateral CP undergoing SEMLS (N = 55, 35 males, age: 10.5 ± 3.1 years) and identified a control cohort with bilateral CP who did not undergo SEMLS (N = 55, 30 males, age: 10.0 ± 3.4 years). There was a small positive causal effect of SEMLS on ΔGDI (1.70 GDI points). Altered motor control (i.e., dynamic and static motor control) and strength had strong effects on GDIpre, but minimal effects on ΔGDI. Spasticity and orthopedic impairments had minimal effects on GDIpre or ΔGDI.

Interpretation: Altered motor control did have a strong effect on GDIpre, indicating that these impairments do have a causal effect on a child’s gait pattern, but minimal effect on expected changes in GDI after SEMLS. Heterogeneity in outcomes suggests there are other factors contributing to changes in gait. Identifying these factors and employing causal methods to examine the complex relationships between impairments and movement will be required to advance our understanding and care of children with CP.

M Yamagami, KM Steele, SA Burden (2020) “Decoding Intent With Control Theory: Comparing Muscle Versus Manual Interface Performance”

Elijah JournalArticle, Media, News, Presentation, Publications, UbiquitousRehabilitation May 7, 2020October 12, 2021AccessEngineering, Accessibility, conference, Control, Electromyography

Journal Article in ACM Conference on Human Factors in Computing Systems (CHI) 2020 Preceedings:

These results suggest that control theory modeling can provide a platform to successfully quantify device performance in the absence of errors arising from motor impairments

Photo (top and bottom) of a user using a slider (top) and muscles (bottom) to control a cursor on the screen.
(Top image) Side image of user. User rests their elbow and pinches the slider and moves the slider towards and away from their body to control the cursor.
(Bottom image) Side image of user. User is strapped to a rigid device holding a bar with hands supinated towards the ceiling, with the forearms at a 90 degree angle from the upper arms.
Electrodes are placed on the biceps and triceps and labelled. Arrows pointing up and down indicate that users move their arm up and down to control the cursor.

Background: Manual device interaction requires precise coordination which may be difficult for users with motor impairments. Muscle interfaces provide alternative interaction methods that may enhance performance, but have not yet been evaluated for simple (eg. mouse tracking) and complex (eg. driving) continuous tasks. Control theory enables us to probe continuous task performance by separating user input into intent and error correction to quantify how motor impairments impact device interaction

Aim: Propose and extend an experimental and analytical method to guide future development of accessible interfaces like muscle interfaces using control theory

Method: We compared the effectiveness of a manual versus a muscle interface for eleven users without and three users with motor impairments performing continuous tasks.

Results: Both user groups preferred and performed better with the muscle versus the manual interface for the complex continuous task.

Interpretation: Results suggest muscle interfaces and algorithms that can detect and augment user intent may be especially useful for future design of interfaces for continuous tasks.

Momona also gave a phenomenal talk on this paper last week in the University of Washington’s ‘DUB Shorts’ series (video posted below). Nice job Momona!

HA Feldner, D Howell, VE Kelly, S Westcott McCoy, KM Steele (2019) “‘Look, Your Muscles Are Firing!’: A Qualitative Study of Clinician Perspectives on the Use of Surface Electromyography in Neurorehabilitation.” Archives of Physical Medicine and Rehabilitation

Nicole JournalArticle, Projects, Publications, UbiquitousRehabilitation April 4, 2019October 12, 2021Electromyography

Journal Article in Archives of Physical Medicine and Rehabilitation:

We collaborated with rehabilitation clinicians across the Seattle region to understand the barriers and facilitators of using wireless electromyography sensors to track motor recovery in the clinic and community

Objective: To examine the perceived value, benefits, drawbacks, and ideas for technology development and implementation of surface electromyography recordings in neurologic rehabilitation practice from clinical stakeholder perspectives.

Design: A qualitative, phenomenological study was conducted. In-depth, semistructured interviews and focus groups were completed. Sessions included questions about clinician perspectives and demonstrations of surface electromyography systems to garner perceptions of specific system features.

Setting: The study was conducted at hospital systems in a large metropolitan area.

Participants: Adult and pediatric physical therapists, occupational therapists, and physiatrists from inpatient, outpatient, and research settings (N=22) took part in the study.

Interventions: Not applicable.

Main Outcome Measures: Interviews and focus groups were audio-recorded, transcribed verbatim, then coded for analysis into themes.

Results: Four major themes emerged: (1) low-tech clinical practice and future directions for rehabilitation; (2) barriers to surface electromyography uptake and potential solutions; (3) benefits of surface electromyography for targeted populations; and (4) essential features of surface electromyography systems.

Conclusions: Surface electromyography systems were not routinely utilized for assessment or intervention following neurologic injury. Despite recognition of potential clinical benefits of surface electromyography use, clinicians identified limited time and resources as key barriers to implementation. Perspectives on design and surface electromyography system features indicated the need for streamlined, intuitive, and clinically effective applications. Further research is needed to determine feasibility and clinical relevance of surface electromyography in rehabilitation intervention.

BR Shuman, M Goudriaan, K Desloovere, MH Schwartz, KM Steele (2019) “Muscle synergies demonstrate only minimal changes after treatment in cerebral palsy.” Journal of NeuroEngineering and Rehabilitation

Nicole JournalArticle, MotorControl, Projects, Publications March 29, 2019October 12, 2021CP (cerebral palsy), Electromyography, Gait, Motor Control, Motor disorders, Muscle synergy, Neurological rehabilitation, Synergy plasticity

Journal Article in Journal of NeuroEngineering and Rehabilitation:

In collaboration with University Hospital Pellenberg we examined whether muscle synergies change following common treatments in CP.

Background: Children with cerebral palsy (CP) have altered synergies compared to typically-developing peers, reflecting different neuromuscular control strategies used to move. While these children receive a variety of treatments to improve gait, whether synergies change after treatment, or are associated with treatment outcomes, remains unknown.

Methods: We evaluated synergies for 147 children with CP before and after three common treatments: botulinum toxin type-A injection (n = 52), selective dorsal rhizotomy (n = 38), and multi-level orthopaedic surgery (n = 57). Changes in synergy complexity were measured by the number of synergies required to explain > 90% of the total variance in electromyography data and total variance accounted for by one synergy. Synergy weights and activations before and after treatment were compared using the cosine similarity relative to average synergies of 31 typically-developing (TD) peers.

Results: There were minimal changes in synergies after treatment despite changes in walking patterns. Number of synergies did not change significantly for any treatment group. Total variance accounted for by one synergy increased (i.e., moved further from TD peers) after botulinum toxin type-A injection (1.3%) and selective dorsal rhizotomy (1.9%), but the change was small. Synergy weights did not change for any treatment group (average 0.001 ± 0.10), but synergy activations after selective dorsal rhizotomy did change and were less similar to TD peers (− 0.03 ± 0.07). Only changes in synergy activations were associated with changes in gait kinematics or walking speed after treatment. Children with synergy activations more similar to TD peers after treatment had greater improvements in gait.

Conclusions: While many of these children received significant surgical procedures and prolonged rehabilitation, the minimal changes in synergies after treatment highlight the challenges in altering neuromuscular control in CP. Development of treatment strategies that directly target impaired control or are optimized to an individual’s unique control may be required to improve walking function.