Publications

M Goudriaan, BR Shuman, KM Steele, M Van den Hauwe, N Goemans, G Molenaers, K Desloovere (2018) “Non-neural Muscle Weakness Has Limited Influence on Complexity of Motor Control during Gait.” Frontiers in Human Neuroscience

Nicole JournalArticle, MotorControl, Projects, Publications , , , , ,

Journal Article in Frontiers in Human Neuroscience:

Despite significant differences in kinematics children with Duchenne muscular dystrophy have similar control complexity to typically developing children.

Abstract: Cerebral palsy (CP) and Duchenne muscular dystrophy (DMD) are neuromuscular disorders characterized by muscle weakness. Weakness in CP has neural and non-neural components, whereas in DMD, weakness can be considered as a predominantly non-neural problem. Despite the different underlying causes, weakness is a constraint for the central nervous system when controlling gait. CP demonstrates decreased complexity of motor control during gait from muscle synergy analysis, which is reflected by a higher total variance accounted for by one synergy (tVAF1). However, it remains unclear if weakness directly contributes to higher tVAF1 in CP, or whether altered tVAF1 reflects mainly neural impairments. If muscle weakness directly contributes to higher tVAF1, then tVAF1 should also be increased in DMD. To examine the etiology of increased tVAF1, muscle activity data of gluteus medius, rectus femoris, medial hamstrings, medial gastrocnemius, and tibialis anterior were measured at self-selected walking speed, and strength data from knee extensors, knee flexors, dorsiflexors and plantar flexors, were analyzed in 15 children with CP [median (IQR) age: 8.9 (2.2)], 15 boys with DMD [8.7 (3.1)], and 15 typical developing (TD) children [8.6 (2.7)]. We computed tVAF1 from 10 concatenated steps with non-negative matrix factorization, and compared tVAF1between the three groups with a Mann-Whiney U-test. Spearman’s rank correlation coefficients were used to determine if weakness in specific muscle groups contributed to altered tVAF1. No significant differences in tVAF1 were found between DMD [tVAF1: 0.60 (0.07)] and TD children [0.65 (0.07)], while tVAF1 was significantly higher in CP [(0.74 (0.09)] than in the other groups (both p < 0.005). In CP, weakness in the plantar flexors was related to higher tVAF1 (r = −0.72). In DMD, knee extensor weakness related to increased tVAF1 (r = −0.50). These results suggest that the non-neural weakness in DMD had limited influence on complexity of motor control during gait and that the higher tVAF1 in children with CP is mainly related to neural impairments caused by the brain lesion.

KM Peters, VE Kelly, T Chang, MC Weismann, S Westcott McCoy, KM Steele (2018) “Muscle recruitment and coordination during upper-extremity functional tests.” Journal of Electromyography and Kinesiology

Keshia JournalArticle, Publications ,

Journal article in Journal of Electromyography and Kinesiology:

In collaboration with Rehabilitation Medicine here at the University of Washington, we evaluated muscle use of 20 unimpaired participants during three upper-extremity functional tests. An interactive supplement can be found HERE.

Recruitment and cocontration plots of eight upper-extremity muscles during the Jebsen Taylor Hand Function Test.Background: Performance-based tests, such as the Jebsen Taylor Hand Function Test or Chedoke Arm and Hand Activity Inventory, are commonly used to assess functional performance after neurologic injury. However, the muscle activity required to execute these tasks is not well understood, even for unimpaired individuals. The purpose of this study was to evaluate unimpaired muscle recruitment and coordination of the dominant and non-dominant limbs during common clinical tests.

Methods: Electromyography (EMG) recordings from eight arm muscles were monitored bilaterally for twenty unimpaired participants while completing these tests. Average signal magnitudes, activation times, and cocontraction levels were calculated from the filtered EMG data, normalized by maximum voluntary isometric contractions (MVICs).

Results: Overall, performance of these functional tests required low levels of muscle activity, with average EMG magnitudes less than 6.5% MVIC for all tests and muscles, except the extensor digitorum, which had higher activations across all tasks (11.7 ± 2.7% MVIC, dominant arm). When averaged across participants, cocontraction was between 25 and 62% for all tests and muscle pairs.

Conclusion: Tasks evaluated by speed of completion, rather than functional quality of movement demonstrated higher levels of muscle recruitment. These results provide baseline measurements that can be used to evaluate muscle-specific deficits after neurologic injury and track recovery using common clinical tests.

 

 

Lab members attend the Society of Women Engineers 2017 Conference

Dr. Steele HuskyADAPT, News, Presentation, Projects, Publications

Momona Yamagami and Karley Benoff attended the Society of Women Engineers (SWE) 2017 conference in Austin, TX. Momona presented on her work with assessing a flexible electrode for long-term electromyography measurements and placed among the top 10 finalists in the graduate research poster competition for SWE. Congratulations Momona!

Momona Yamagami presents her research during a poster session

 

Karley said that SWE 17 was an incredible experience filled with opportunities for professional growth and networking. Here are some of her impressions:

“My favorite guest talk was titled “TECHing While Women and with Disability” where five panelists shared their experiences navigating the engineering world with a disability and/or as an advocate for those with disabilities. Dr. Richard Ladner of the University or Washington CSE department (pictured with Karley below) was one of the panelists. His research on accessible technology, especially technology for the blind, deaf, deaf-blind, and hard-of-hearing, was truly inspiring. The panelists’ presentations provided a unique perspective for approaching user-centered design. I hope to use the lessons learned from the panelists, as well as from all of the SWE 17 attendees I met, to better inform the development of my orthosis project this year. By targeting accessibility and user-centered design, I aspire to develop a universal elbow-driven orthosis that will improve function for users with a wide variety of abilities.

The panelist idea is something HuskyADAPT wants to organize for its club members. Since I am an officer in the club, we are currently trying to plan such an event to better inform design teams and members alike about peoples’ experiences living with disabilities. By understanding what each individual needs, we can better design devices and technology to address what the user wants.”

Karley Benoff with one of the panelists Dr. Richard Ladner of the University or Washington CSE department

 

H Choi, KM Peters, M MacConnell, K Ly, E Eckert, KM Steele (2017) “Impact of ankle foot orthosis stiffness on Achilles tendon and gastrocnemius function during unimpaired gait.” Journal of Biomechanics

Dr. Steele JournalArticle, Orthoses, Publications , , , , ,

Journal article in Journal of Biomechanics:

How does the stiffness of an AFO impact the muscultendon dynamics of the gastrocnemius?

Abstract

Method combining ultrasound and musculoskeletal modeling to evaluate changes in muscle and tendon length.

Ankle foot orthoses (AFOs) are designed to improve gait for individuals with neuromuscular conditions and have also been used to reduce energy costs of walking for unimpaired individuals. AFOs influence joint motion and metabolic cost, but how they impact muscle function remains unclear. This study investigated the impact of different stiffness ankle foot orthoses (AFOs) on medial gastrocnemius muscle (MG) and Achilles tendon (AT) function during two different walking speeds. We performed gait analyses for eight unimpaired individuals. Each individual walked at slow and very slow speeds with a 3D printed AFO with no resistance (free hinge condition) and four levels of ankle dorsiflexion stiffness: 0.25 Nm / °, 1 Nm / °, 2 Nm / °, and 3.7 Nm / °. Motion capture, ultrasound, and musculoskeletal modeling were used to quantify MG and AT lengths with each AFO condition. Increasing AFO stiffness increased peak AFO dorsiflexion moment with decreased peak knee extension and peak ankle dorsiflexion angles. Overall musculotendon length and peak AT length decreased, while peak MG length increased with increasing AFO stiffness. Peak MG activity, length, and velocity significantly decreased with slower walking speed. This study provides experimental evidence of the impact of AFO stiffness and walking speed on joint kinematics and musculotendon function. These methods can provide insight to improve AFO designs and optimize musculotendon function for rehabilitation, performance, or other goals.

 

 

A Rozumalski, KM Steele, MH Schwartz (2017) “Muscle synergies are similar when typically developing children walk on a treadmill at different speeds and slopes.” Journal of Biomechanics

Dr. Steele JournalArticle, MotorControl , , , ,
There were minimal changes in EMG signals with walking speed and slope.

Journal article in Journal of Biomechanics:

In collaboration with Gillette Children’s Specialty Healthcare, we evaluated whether muscle synergies change when unimpaired individuals walk at different speeds and slopes.

There were minimal changes in EMG signals with walking speed and slope.Background: The aim of this study was to determine whether changes in synergies relate to changes in gait while walking on a treadmill at multiple speeds and slopes. The hypothesis was that significant changes in movement pattern would not be accompanied by significant changes in synergies, suggesting that synergies are not dependent on the mechanical constraints but are instead neurological in origin.

Methods: Sixteen typically developing children walked on a treadmill for nine combinations (stages) of different speeds and slopes while simultaneously collecting kinematics, kinetics, and surface electromyography (EMG) data. The kinematics for each stride were summarized using a modified version of the Gait Deviation Index that only includes the sagittal plane. The kinetics for each stride were summarized using a modified version of the Gait Deviation Index – Kinetic which includes sagittal plane moments and powers. Within each synergy group, the correlations of the synergies were calculated between the treadmill stages.

Results: While kinematics and kinetics were significantly altered at the highest slope compared to level ground when walking on a treadmill, synergies were similar across stages.

Conclusions: The high correlations between synergies across stages indicate that neuromuscular control strategies do not change as children walk at different speeds and slopes on a treadmill. However, the multiple significant differences in kinematics and kinetics between stages indicate real differences in movement pattern. This supports the theory that synergies are neurological in origin and not simply a response to the biomechanical task constraints.