Publications Archives - Page 16 of 32 - Neuromechanics & Mobility Lab

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 October 3, 2017October 12, 20213D-printed, AFO, Cerebral Palsy, Exoskeleton, Orthosis, Simulation

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 September 3, 2017October 12, 2021Control, DMC, Pediatric, Synergy, Walk-DMC

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.

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.

Daniel Ballesteros, Wing-Sum Law, and Claire Mitchell Present

Keshia MotorControl, News, Orthoses, Presentation, Projects, Publications August 16, 2017October 12, 2021

Congratulations to Daniel, Wing-Sum and Claire for their excellent work this summer. We had the privilege of hosting three undergraduate students through the Summer Scholars program through Co-Motion and the Center for Sensorimotor Neural Engineering here at the University of Washington.

Daniel presented in Mary Gates Hall on his research involving the implementation of a pediatric exoskeleton into low-resource countries:

Claire researched how varying muscles impact synergy outcomes:

Wing-Sum assessed the impact of an ankle foot orthosis on muscle demands in children with cerebral palsy and typically developing peers:

Lab members present at the 2017 American Society of Biomechanics

Keshia News, Presentation, Publications August 16, 2017October 12, 2021

Ben Shuman, Michael Rosenberg, Keshia Peters, and Kat Steele all presented posters during the 2017 American Society of Biomechanics conference in Boulder, CO.

Dr. Steele also presented during a session which encompassed ASB and the Gait and Clinical Movement Analysis Society to invoke discussion about technical challenges in clinical motion analysis.

Great work, everyone!

M Rosenberg, KM Steele (2017) “Simulated impacts of ankle foot orthoses on muscle demand and recruitment in typically-developing children and children with cerebral palsy and crouch gait.” PLoS ONE

Keshia JournalArticle, Orthoses, Projects, Publications July 13, 2017October 12, 2021Cerebral Palsy, Orthoses

Journal article in PLOS ONE:

Michael Rosenberg and Kat Steele investigate the impacts of ankle foot orthoses on children with cerebral palsy and typically-developing peers through simulation.

Background

Passive ankle foot orthoses (AFOs) are often prescribed for children with cerebral palsy (CP) to assist locomotion, but predicting how specific device designs will impact energetic demand during gait remains challenging. Powered AFOs have been shown to reduce energy costs of walking in unimpaired adults more than passive AFOs, but have not been tested in children with CP.

Aim

The goal of this study was to investigate the potential impact of powered and passive AFOs on muscle demand and recruitment in children with CP and crouch gait.

Method

We simulated gait for nine children with crouch gait and three typically-developing children with powered and passive AFOs. For each AFO design, we computed reductions in muscle demand compared to unassisted gait.

Results

Powered AFOs reduced muscle demand 15–44% compared to unassisted walking, 1–14% more than passive AFOs. A slower walking speed was associated with smaller reductions in absolute muscle demand for all AFOs (r² = 0.60–0.70). However, reductions in muscle demand were only moderately correlated with crouch severity (r² = 0.40–0.43). The ankle plantarflexor muscles were most heavily impacted by the AFOs, with gastrocnemius recruitment decreasing 13–73% and correlating with increasing knee flexor moments (r² = 0.29–0.91).

Interpretation

These findings support the potential use of powered AFOs for children with crouch gait, and highlight how subject-specific kinematics and kinetics may influence muscle demand and recruitment to inform AFO design. PDF