Publications

EC Kuska, N Mehrabi, MH Schwartz, KM Steele (2022) “Number of synergies impacts sensitivity of gait to weakness and contracture”

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

Journal Article in Journal of Biomechanics

Muscle activity during gait can be described by a small set of synergies, weighted groups of muscles, that are theorized to reflect underlying neural control. For people with neurologic injuries, like cerebral palsy or stroke, even fewer synergies are required to explain muscle activity during gait. This reduction in synergies is thought to reflect altered control and is associated with impairment severity and treatment outcomes. Individuals with neurologic injuries also develop secondary musculoskeletal impairments, like weakness or contracture, that can impact gait. Yet, the combined impacts of altered control and musculoskeletal impairments on gait remains unclear.

A two-dimensional sagittal plane musculoskeletal model and synergy simulation framework tracked unimpaired gait kinematics. The model had nine degrees of freedom, including right and left leg hip, knee, and ankle flexion, actuated by eight muscles per leg. Fixed sets of synergies constrained control, forcing the direct collocation algorithm to solve for synergy activations. The objective function minimized deviations from unimpaired kinematics and the sum of muscle activations squared (neural demand). Weakness, simulated by a reduction in maximum isometric force, and contracture, simulated by a reduction in tendon slack length, were progressively increased for each muscle or muscle group until the simulation failed to replicate unimpaired gait. Kinematic deviations and convergence determined the success of the simulation. The primary outcomes were (1) musculoskeletal impairment thresholds, defined by the amount of weakness or contracture before failure, and (2) neural demand of each gait cycle.Aim: In this study, we use a two-dimensional musculoskeletal model constrained to synergy control to simulate unimpaired gait.

Methods: We vary the number of synergies, while simulating muscle weakness and contracture to examine how altered control impacts sensitivity to musculoskeletal impairment while tracking unimpaired gait.

Results: Results demonstrate that reducing the number of synergies increases sensitivity to weakness and contracture for specific muscle groups. For example, simulations using five-synergy control tolerated 40% and 51% more knee extensor weakness than those using four- or three-synergy control, respectively. Furthermore, when constrained to four- or three-synergy control, the model was increasingly sensitive to contracture and weakness of proximal muscles, such as the hamstring and hip flexors. Contrastingly, neither the amount of generalized nor plantarflexor weakness tolerated was affected by the number of synergies.

Interpretation: These findings highlight the interactions between altered control and musculoskeletal impairments, emphasizing the importance of measuring and incorporating both in future simulation and experimental studies.

NSF Convergence Accelerator | Living Better through Rehabilitation & Assistive Technology

Dr. Steele AccessEngineering, Outreach, Presentation , , , ,

A second NSF Convergence Accelerator focused on increasing access and inclusion. The LIBERATE workshop is focused on Living Better through Rehabilitation & Assistive Technology.

title slide of Dr. Steele's presentation on a purple background with text Liberate 2021 NSF convergence accelerator

As an NSF Convergence Accelerator, participants will seek to identify pathways that could be  pursued by multidisciplinary teams to get solutions at least to a prototype stage in 3-5 years. The long-term goal from this workshop is to kickstart the next wave of technologies that will empower people with disabilities.

Dr. Steele will be participating and presenting some kernels of ideas for inclusion, especially highlighting recent work from CREATE.

Slides

Download PDF of slides.

Email Dr. Steele (kmsteele – at – uw – dot – edu) with questions, comments, or suggestions.

NSF Convergence Accelerator | Inclusion in the Workplace

Dr. Steele AccessEngineering, Presentation , , , ,

The NSF Convergence Accelerator on Accelerating Disability Inclusion in Workplaces through Technology starts on May 20th.


Title slide of Dr. Steele's talk "Ideas for Inclusion" on a purple background.

 

The goals for this workshop are to identify pathways for technology to solve or mitigate accessibility and inclusion challenges in current and emerging workplaces. As an NSF Convergence Accelerator, participants will seek to identify pathways that could be  pursued by multidisciplinary teams to get solutions at least to a prototype stage in 3-5 years. The long-term goals from this workshop are to set in motion paradigm shifts that brings the percentage of individuals with disabilities participating in the workforce closer to the general population.

Dr. Steele will be presenting some ideas on inclusion in the workplace – from work environments to transportation to workforce development.

Slides

Download PDF of slides.

Email Dr. Steele (kmsteele – at – uw – dot – edu) with questions, comments, or suggestions.

HA Feldner, C Papazian, KM Peters, CJ Cruetzfeldt, KM Steele (2021) “Clinical Use of Surface Electromyography to Track Acute Upper Extremity Muscle Recovery after Stroke: A Descriptive Case Study of a Single Patient”

Elijah JournalArticle, News, Publications , , , ,

Journal Article in Applied System Innovation:

This work highlights the potential of wearable technologoies to monitor muscle activity changes during stroke recovery in acute clinical settings and their importance for motivation and understanding of progression from the survivor’s point of view: ‘I was hopeful that it would show signs of things that are occurring when I couldn’t physically feel it…if you had other scientific evidence that things were happening, even beyond their notion that it would, it gives you a lot of hope. You just have to be patient, and it’s harder to take when someone tells you, but easier to understand if someone actually shows you’.

Left image depicts arm with pads placed over muscle with right pictures depicting similar image

Aim: Describe the use of wireless sEMG sensors to examine changes in muscle activity during acute and subacute phases of stroke recovery, and understand the participant’s perceptions of sEMG monitoring.

Method: Muscle activity was tracked by five wireless sEMG sensors beginning three days post-stroke and continued through discharge from inpatient rehabilitation. Activity logs were completed each session, and a semi-structured interview occurred at the final session with three- and eight-month follow-up sessions.

Results: The longitudinal monitoring of muscle and movement recovery in the clinic and community was feasible using sEMG sensors. The participant and medical team felt monitoring was unobtrusive, interesting, and motivating for recovery, but desired greater in-session feedback to inform rehabilitation.

Interpretation: This work highlights that barriers in equipment and signal quality still exist, but capitalizing on wearable sensing technology in the clinic holds promise for enabling personalized stroke recovery.