Publications

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

Keshia MotorControl, News, Orthoses, Presentation, Projects, Publications

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:

Daniel fields a question from a member of the University of Washington community during his poster session at Mary Gates Hall. Claire researched how varying muscles impact synergy outcomes:

 

Claire Mitchell presents her poster at the Center for Sensorimotor Neural Engineering

 

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

Wing-Sum presents her research during a poster session

Lab members present at the 2017 American Society of Biomechanics

Keshia News, Presentation, Publications

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!

Ben Shuman discusses his poster Michael Rosenberg walks through the results section of his poster with a fellow ASB member.

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

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Top: Ankle, knee and hip kinematics for gait in TD children and children with crouch gait. TD children walked with less ankle dorsiflexion and knee flexion during stance than those with crouch gait. Bottom: Ankle, knee and hip moments for gait in TD children and crouch gait. TD children generated larger peak plantarflexor moments and smaller peak knee extensor moments compared to crouch gait. Knee extensor moments increased with increasing crouch severity.

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

Top: Ankle, knee and hip kinematics for gait in TD children and children with crouch gait. TD children walked with less ankle dorsiflexion and knee flexion during stance than those with crouch gait. Bottom: Ankle, knee and hip moments for gait in TD children and crouch gait. TD children generated larger peak plantarflexor moments and smaller peak knee extensor moments compared to crouch gait. Knee extensor moments increased with increasing crouch severity.

KM Steele, BR Shuman, MH Schwartz (2017) “Crouch severity is a poor predictor of elevated oxygen consumption in cerebral palsy.” Journal of Biomechanics

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Scatter plot illustrating that there is not a significant correlation between minimum knee flexion angle during stance and oxygen consumption.

Journal article in Journal of Biomechanics:

Does energy consumption during walking increase with crouch severity among children with cerebral palsy?

Scatter plot illustrating that there is not a significant correlation between minimum knee flexion angle during stance and oxygen consumption.Abstract: Children with cerebral palsy (CP) expend more energy to walk compared to typically-developing peers. One of the most prevalent gait patterns among children with CP, crouch gait, is often singled out as especially exhausting. The dynamics of crouch gait increase external flexion moments and the demand on extensor muscles. This elevated demand is thought to dramatically increase energy expenditure. However, the impact of crouch severity on energy expenditure has not been investigated among children with CP. We evaluated oxygen consumption and gait kinematics for 573 children with bilateral CP. The average net nondimensional oxygen consumption during gait of the children with CP (0.18 ± 0.06) was 2.9 times that of speed-matched typically-developing peers. Crouch severity was only modestly related to oxygen consumption, with measures of knee flexion angle during gait explaining only 5–20% of the variability in oxygen consumption. While knee moment and muscle activity were moderately to strongly correlated with crouch severity (r2 = 0.13–0.73), these variables were only weakly correlated with oxygen consumption (r2 = 0.02–0.04). Thus, although the dynamics of crouch gait increased muscle demand, these effects did not directly result in elevated energy expenditure. In clinical gait analysis, assumptions about an individual’s energy expenditure should not be based upon kinematics or kinetics alone. Identifying patient-specific factors that contribute to increased energy expenditure may provide new pathways to improve gait for children with CP.