EMG

Engineering Discovery Days 2024

Katie Landwehr News, Outreach , , , ,

The University of Washington College of Engineering re-launched Engineering Discovery Days this spring. Discovery Days has been a signature outreach event for over 100 years, providing fun and enriching hands-on experiences for students, teachers, and families from across the state. Discovery Days is also an opportunity for our community of UW Engineering students, staff, and faculty to share their passion for engineering with the next generation of innovators.

The UW Biomechanics Faculty put together an exhibit titled “Biomechanics Assemble! From Exoskeletons to Cytoskeletons” with the goal of demonstrating how we study movement and forces in humans and cells at UW.

Two people stand outside, one with a robotic leg, holding a sign reading, "The Human Body: The Ultimate Machine." Both wear "Engineering" shirts. Trees and an event tent are in the background.
A person wearing an exoskeleton suit stands facing a small group of people in a room with various individuals and equipment.
Two people engaged in a discussion while one is wearing a 3D printed prosthetic hand.
Two people fist bumping. One person is wearing a 3D printed prosthetic hand.
A person in a lab wearing an exoskeleton, ready to teach students about biomechanics research.
A woman instructing a child how to use a 3D printed prosthetic hand to pick up a small bottle
A group of students standing around while one is wearing a 3D printed prosthetic hand
A group of students standing around while one is wearing a 3D printed prosthetic hand

The Steele Lab along with the Ingraham Lab hosted two booths. Each booth featured hand-on activities and games for students to engage with.

The first booth features an ensemble of exoskeletons and assistive devices, including the Biomotum Spark and 3D printed prosthetic hands.

The second booth featured two games for students to engage with, including “Myodino” using Delsys EMG sensors, and “UltraLeap Ring Sorting” VR game using the UltraLeap hand tracking technology.

In this lab, we think the human body is “The Ultimate Machine” and we were so excited to share HOW we study the human body at Discovery Days 2024.

A woman showing a young student how to play the game "MyoDino" by activating forearm muscles
A man placing an EMG sensor on the forearm of a young student
A small group of people standing around watching a student play MyoDino on a laptop
A small group of students standing around looking at a laptop as a woman explains how to play the "UltraLeap Ring Sorting"
A small group of students standing a laptop while a student plays the "UltraLeap Ring Sorting"
A small group of students standing a laptop while a person wearing an exoskeleton plays the "UltraLeap Ring Sorting"

AM Spomer, BC Conner, MH Schwartz, ZF Lerner, KM Steele (2023) “Audiovisual biofeedback amplifies plantarflexor adaptation during walking among children with cerebral palsy”

Katie Landwehr JournalArticle, MotorControl, News, Publications , , , , , ,

Journal Article in Journal of NeuroEngineering and Rehabilitation

Biofeedback is a promising noninvasive strategy to enhance gait training among individuals with cerebral palsy (CP). Commonly, biofeedback systems are designed to guide movement correction using audio, visual, or sensorimotor (i.e., tactile or proprioceptive) cues, each of which has demonstrated measurable success in CP.

Figure 1. Experimental Protocol. Audiovisual (AV) biofeedback on soleus activity was provided for the more-affected limb alongside an auto-adjusting target score. Sensorimotor (SM) biofeedback was provided for the more-affected limb using an untethered ankle exoskeleton designed to impart a resistive ankle torque through stance, proportional to baseline values. Participants completed three data collection visits (pre-acclimation, post-acclimation, and follow-up), during which they walked with both biofeedback systems independently and in combination. Trials were pseudo-randomized within and between visits to ensure that feedback modalities were presented to each participant in a different order and control for fatigue and learning effects. Each trial was 10 min long and separated into baseline, feedback, and washout phases. All data analysis was performed for early (strides 1–30), mid (strides 91–110), and late (strides 181–210) feedback phases and washout (strides 1–30). Mean soleus activity for individual strides (purple dots) was normalized to baseline activity. Between the pre-acclimation and post-acclimation visits, participants completed four, 20-min acclimation sessions where they received additional practice with both systems

Aim: The aim of this study is to evaluate how the modality of biofeedback may influence user response which has significant implications if systems are to be consistently adopted into clinical care.

Method: In this study, we evaluated the extent to which adolescents with CP (7M/1F; 14 [12.5,15.5] years) adapted their gait patterns during treadmill walking (6 min/modality) with audiovisual (AV), sensorimotor (SM), and combined AV + SM biofeedback before and after four acclimation sessions (20 min/session) and at a two-week follow-up. Both biofeedback systems were designed to target plantarflexor activity on the more-affected limb, as these muscles are commonly impaired in CP and impact walking function. SM biofeedback was administered using a resistive ankle exoskeleton and AV biofeedback displayed soleus activity from electromyography recordings during gait. At every visit, we measured the time-course response to each biofeedback modality to understand how the rate and magnitude of gait adaptation differed between modalities and following acclimation.

Results: Participants significantly increased soleus activity from baseline using AV + SM (42.8% [15.1, 59.6]), AV (28.5% [19.2, 58.5]), and SM (10.3% [3.2, 15.2]) biofeedback, but the rate of soleus adaptation was faster using AV + SM biofeedback than either modality alone. Further, SM-only biofeedback produced small initial increases in plantarflexor activity, but these responses were transient within and across sessions (p > 0.11). Following multi-session acclimation and at the two-week follow-up, responses to AV and AV + SM biofeedback were maintained.

Interpretation: This study demonstrated that AV biofeedback was critical to increase plantarflexor engagement during walking, but that combining AV and SM modalities further amplified the rate of gait adaptation. Beyond improving our understanding of how individuals may differentially prioritize distinct forms of afferent information, outcomes from this study may inform the design and selection of biofeedback systems for use in clinical care.

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 Landwehr JournalArticle, MotorControl, News, Projects, Publications , , , , , ,

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.

Schematic of the custom biofeedback system. A) Motor control biofeedback used to encourage pattern exploration. B) Individuals significantly modified motor control complexity using biofeedback. C) Distal gait mechanics were associated with changes in control complexity.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 Landwehr JournalArticle, MotorControl, News, Publications , , , , , ,

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.

FIGURE 1 Directed Acyclic Graph (DAG) describing the assumed causal relationships between SEMLS (exposure) and 1GDI (outcome). The causal relationship between SEMLS and 1GDI is mediated by changes in impairments (1Imp). Baseline GDI (GDIpre) and 1GDI are related by measurement methods and other, unmeasured factors. Baseline impairment (Imppre), surgical history (Hx), and Age are also included as causal factors. The DAG also includes unmeasured factors related to general CP severity, which impact baseline impairment and surgical history. The step-by-step process and rationale for this DAG are available in the Supplementary Material and an interactive version is available on dagitty (http://dagitty.net/mUCSPWo).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.

Steele Lab members present their research to Seattle Young Adult Stroke Survivors (YASS)

Nicole News, UbiquitousRehabilitation ,

Steele Lab members – Kat, Christina, Nick, and Momona – were invited to present their research about wearable sensors for stroke recovery and device control to the Seattle Young Adult Stroke Survivors (YASS). YASS is a support group for individuals who have experienced a stroke and creates a community to learn, listen, share, and more. Steele lab was one of the first research groups to come and share our work with them. 

Young Adult Stroke Survivors logo. Light green writing on a dark green background with a silhouette of a person climbing up boulders.

Our presentation began with background information regarding neurophysiological changes after stroke to provide insight into upper extremity functional impairments – including weakness, loss of dexterity, and abnormal tone. Wearable sensors, such as electromyography (EMG), can provide information regarding muscle function. Many of the listeners were surprised to hear that their own smartphones or watches can act as wearable sensors!

A focus of our research is detecting muscle activity early after stroke using EMG. One member recalled thinking their muscle was firing during their acute recovery but could not see any physical movement.  EMG allows us to capture that type of activity and any functional changes throughout recovery, empowering patients and clinicians to track their recovery and adjust their therapy regimen. The crowd was interested in using EMG to evaluate their own muscles, identify which were firing, and guide their rehabilitation. 

EMG not only helps us track recovery, but can be paired with consumer technology. Nick demonstrated how using muscle activity from the affected limb can incorporate rehabilitation into daily computer use. EMG signals can simulate pressing keys on a keyboard or moving a mouse cursor, making it easier for people with limited mobility to use technology. YASS members expressed enthusiasm about the increasing commercial availability of such devices so they can buy them and give them a try.

It was a great opportunity to connect with stroke survivors and hear their thoughts on wearable sensors. Thank you to YASS for having us come in and share our research!