JournalArticle Archives - Page 12 of 15 - Neuromechanics & Mobility Lab

BR Shuman, M Goudriaan, L Bar-On, MH Schwartz, K Desloovere, KM Steele (2016) “Repeatability of muscle synergies within and between days for typically developing children and children with cerebral palsy.” Gait & Posture.

Dr. Steele JournalArticle, MotorControl, Projects, Publications January 28, 2016October 12, 2021Cerebral Palsy, EMG, Gillette, Leuven, Synergy

Journal article in Gait and Posture:

Filtering parameters impact the results from muscle synergy analyses.

Abstract: Muscle synergies are typically calculated from electromyographic (EMG) signals using nonnegative matrix factorization. Synergies identify weighted groups of muscles that are commonly activated together during a task, such as walking. Synergy analysis has become an emerging tool to evaluate neuromuscular control; however, the repeatability of synergies between trials and days has not been evaluated. The goal of this study was to evaluate the repeatability of synergy complexity and structure in unimpaired individuals and individuals with cerebral palsy (CP). EMG data were collected from eight lower-limb muscles during gait for six typically developing (TD) children and five children with CP on two separate days, over three walking speeds. To evaluate synergy complexity, we calculated the total variance accounted for by one synergy (tVAF1). On a given day, the average range in tVAF1 between gait cycles was 18.2% for TD and 19.1% for CP. The average standard deviation in tVAF1 between gait cycles was 4.9% for TD and 5.0% for CP. Average tVAF1 calculated across gait cycles was not significantly different between days for TD or CP participants. Comparing synergy structure, the average (standard deviation) within day correlation coefficients of synergy weights for two or more synergies were 0.89 (0.15) for TD and 0.88 (0.15) for CP. Between days, the average correlation coefficient of synergy weights for two or more synergies was greater than 0.89 for TD and 0.74 for CP. These results demonstrate that synergy complexity and structure averaged over multiple gait cycles are repeatable between days in both TD and CP groups.

SSM Lee, D Gaebler-Spira, LQ Zhang, WZ Rymer, KM Steele, (2016) “Use of shear wave ultrasound elastography to quantify muscle properties in cerebral palsy.” Clinical Biomechanics

Dr. Steele JournalArticle, MotorControl, UbiquitousRehabilitation November 6, 2015October 12, 2021Cerebral Palsy, Muscle, Ultrasonography

Sample ultrasound images from gastrocnemius and tibialis anterior showing greater shear wave velocity on more affected limb.

Journal article in Clinical Biomechanics:

Kat Steele partnered with Sabrina Lee from Northwestern University and the Rehabilitation Institute of Chicago to investigate shearwave ultrasound elastography as a new tool to quantify changes in muscle properties in cerebral palsy.

Abstract: Individuals with cerebral palsy tend to have altered muscle architecture and composition, but little is known about the muscle material properties, specifically stiffness. Shear wave ultrasound elastography allows shear wave speed, which is related to stiffness, to be measured in vivo in individual muscles. Our aim was to evaluate the material properties, specifically stiffness, as measured by shear wave speed of the medial gastrocnemius and tibialis anterior muscles in children with hemiplegic cerebral palsy across a range of ankle torques and positions, and fascicle strains. Shear wave speed was measured bilaterally in the medial gastrocnemius and tibialis anterior over a range of ankle positions and torques using shear wave ultrasound elastography in eight individuals with hemiplegic cerebral palsy. B-mode ultrasound was used to measure muscle thickness and fascicle strain. Shear waves traveled faster in the medial gastrocnemius and tibialis anterior of the more-affected limb by 14% (P = 0.024) and 20% (P = 0.03), respectively, when the ankle was at 90°. Shear wave speed in the medial gastrocnemius increased as the ankle moved from plantarflexion to dorsiflexion (less affected: r² = 0.82, P < 0.001; more-affected: r² = 0.69, P < 0.001) and as ankle torque increased (less affected: r² = 0.56,P < 0.001; more-affected: r² = 0.45, P < 0.001). In addition, shear wave speed was strongly correlated with fascicle strain (less affected: r² = 0.63, P < 0.001; more-affected: r² = 0.53, P < 0.001). The higher shear wave speed in the more-affected limb of individuals with cerebral palsy indicates greater muscle stiffness, and demonstrates the clinical potential of shear wave elastography as a non-invasive tool for investigating mechanisms of altered muscle properties and informing diagnosis and treatment.

KM Steele, A Rozumalski, MH Schwartz (2015) “Muscle synergies and complexity of neuromuscular control during gait in cerebral palsy.” Developmental Medicine & Child Neurology

Dr. Steele JournalArticle, MotorControl July 23, 2015October 12, 2021Cerebral Palsy, Control, DMC, Synergy

WalkDMC decreased with GMFCS level among individuals with cerebral palsy.

Journal article accepted in Developmental Medicine & Child Neurology:

Kat Steele partnered with Mike Schwartz and Adam Rozumalski of Gillette Children’s Specialty Healthcare to complete one of the largest studies to date of individuals with cerebral palsy. They quantified how neuromuscular control is altered among individuals with cerebral palsy and how this altered control can contribute to impaired function.

Abstract: Individuals with cerebral palsy (CP) have impaired movement due to a brain injury near birth. Understanding how neuromuscular control is altered in CP can provide insight into pathological movement. We sought to determine if individuals with CP demonstrate reduced complexity of neuromuscular control during gait compared with unimpaired individuals and if changes in control are related to functional ability. Muscle synergies during gait were retrospectively analyzed for 633 individuals (age range 3.9–70y): 549 with CP (hemiplegia, n=122; diplegia, n=266; triplegia, n=73; quadriplegia, n=88) and 84 unimpaired individuals. Synergies were calculated using non-negative matrix factorization from surface electromyography collected during previous clinical gait analyses. Synergy complexity during gait was compared with diagnosis subtype, functional ability, and clinical examination measures. Fewer synergies were required to describe muscle activity during gait in individuals with CP compared with unimpaired individuals. Changes in synergies were related to functional impairment and clinical examination measures including selective motor control, strength, and spasticity. Interpretation: Individuals with CP use a simplified control strategy during gait compared with unimpaired individuals. These results were similar to synergies during walking among adult stroke survivors, suggesting similar neuromuscular control strategies between these clinical populations. PDF

Also, make sure you look at the commentary from Diane Damiano. She provides perspective about the utility of synergies for evaluating neuromuscular control in children with cerebral palsy and future challenges.

B Blaser, S Burgstahler, KM Steele, (2015) “Including universal design in engineering courses to attract diverse students.” Proceedings of the American Society for Engineering Education

Dr. Steele AccessEngineering, JournalArticle June 17, 2015October 12, 2021Accessibility, Universal Design

Paper at American Society of Engineering Education

Brianna Blaser and Kat Steele presented their paper, “Including universal design in engineering courses to attract diverse students” at the American Society for Engineering Education annual conference in Seattle, WA on June 17, 2015. This paper reported the results of a survey to current students with disabilities about their experiences in engineering classes and how accessibility and universal design may be incorporated into the engineering curriculum.

Abstract:

Research has shown that members of some groups, including women and people with disabilities, are particularly interested in how their fields of study, such as engineering, can improve the world around them. Teaching students about universal design (UD) and how it benefits individuals with disabilities has the potential to attract these students to engineering and encourage them to create products and environments that are accessible to and usable by individuals with a broad range of characteristics. In this paper, we present findings from an online discussion and site visits to engineering labs with students with disabilities. Based on these findings, we identify opportunities for including disability and UD topics in engineering curricula. Capstone or cornerstone engineering design classes are a natural fit for incorporating these concepts, but other engineering course can be enhanced with disability and UD content as well. We also present suggestions for applying UD to instruction in order to ensure that engineering courses are accessible to the widest audience possible. This investigation provides a foundation for using UD to broaden participation in engineering and training engineers who can design products and environments that address the diverse needs of society.

PDF

KM Steele, MC Tresch, EJ Perreault (2015) “Consequences of biomechanically constrained tasks in the design and interpretation of synergy analyses.” Journal of Neurophysiology

Dr. Steele JournalArticle, MotorControl January 10, 2015October 12, 2021Control, Simulation

Synergy similarity is reduced with musculoskeletal constraints.

Journal article in Journal of Neurophysiology:

Consequences of biomechanically constrained tasks in the design and interpretation of synergy analyses

Matrix factorization algorithms are commonly used to analyze muscle activity and provide insight into neuromuscular control. These algorithms identify low-dimensional subspaces, commonly referred to as synergies, which can describe variation in muscle activity during a task. Synergies are often interpreted as reflecting underlying neural control; however, it is unclear how these analyses are influenced by biomechanical and task constraints, which can also lead to low-dimensional patterns of muscle activation. The aim of this study was to evaluate whether commonly used algorithms and experimental methods can accurately identify synergy-based control strategies. This was accomplished by evaluating synergies from five common matrix factorization algorithms using muscle activations calculated from 1) a biomechanically constrained task using a musculoskeletal model and 2) without task constraints using random synergy activations. Algorithm performance was assessed by calculating the similarity between estimated synergies and those imposed during the simulations; similarities ranged from 0 (random chance) to 1 (perfect similarity). Although some of the algorithms could accurately estimate specified synergies without biomechanical or task constraints (similarity >0.7), with these constraints the similarity of estimated synergies decreased significantly (0.3-0.4). The ability of these algorithms to accurately identify synergies was negatively impacted by correlation of synergy activations, which are increased when substantial biomechanical or task constraints are present. Increased variability in synergy activations, which can be captured using robust experimental paradigms that include natural variability in motor activation patterns, improved identification accuracy but did not completely overcome effects of biomechanical and task constraints. These results demonstrate that a biomechanically constrained task can reduce the accuracy of estimated synergies and highlight the importance of using experimental protocols with physiological variability to improve synergy analyses. PDF