Neuromechanical adaptations in joint stiffness when hopping with a SL-AFO

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Please use this identifier to cite or link to this item: http://hdl.handle.net/1853/14745

Title:	Neuromechanical adaptations in joint stiffness when hopping with a SL-AFO
Author:	Roiz, Ronald A.
Abstract:	Humans hopping on different elastic surfaces in series adjust leg stiffness to maintain system stiffness primarily by modulating ankle joint stiffness. When a parallel elastic element is applied at the ankle to assist plantar flexion, leg stiffness and total ankle joint stiffness is conserved. Moreover, biological ankle joint stiffness decreases to offset the added stiffness of the spring. We studied the effects of adding a resistive plantarflexion torque in parallel with the ankle. We hypothesized leg stiffness and total ankle joint stiffness would remain invariant and that biological ankle joint stiffness would increase to compensate. We ran a repeated measures study on 10 subjects hopping in place under three conditions: AFO (control), Plantarflexion Assist Spring-Loaded AFO (PA-SLAFO), and Plantarflexion Resist Spring-Loaded AFO (PR-SLAFO). We collected kinematic, kinetic, and EMG data at each condition for three frequencies. We analyzed statistics using a Three-Way ANOVA (subject, condition, frequency) with a Bonferroni Post-Hoc test. Different AFO conditions had no effect on leg stiffness. Total ankle joint stiffness was maintained for PA-SLAFO, with biological ankle joint stiffness decreasing to perfectly compensate. In the PR-SLAFO condition, total ankle joint stiffness was greater than expected. Biological ankle joint stiffness increased with PR SL-AFO, but was unable to completely compensate for the added resistance. This implies that despite adequate global compensation to maintain leg stiffness, subjects could not completely compensate for added resistive torque solely at the ankle and had to enlist a multi-joint compensation strategy. We are currently investigating these multi-joint compensation strategies.
Description:	Presented at a Special Seminar: MSPO Student Presentations on April 11, 2007 at the Coon Building, Room 115 Slow Hopping Video Runtime: 00:19 seconds Video of Presentation Runtime: 20:29 minutes Hopping Video Runtime: 00:10 seconds Slow Hopping Video Runtime: 00:05 seconds
Type:	Masters Project Video
URI:	http://hdl.handle.net/1853/14745
Date:	2007-04-11
Contributor:	Georgia Institute of Technology. School of Applied Physiology
Publisher:	Georgia Institute of Technology
Subject:	Spring-loaded ankle-foot orthosis Hopping Prosthetic foot stiffness Torque Compensation
Advisor:	Research conducted by: Ronald A. Roiz, Arick Auyang, and Dr. Y. H. Chang.

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Files	Size	Format	View	Description
presentation_roiz.mp4	51.99Mb	MPEG-4 video	View/ Open	Video of Presentation
presentation_roiz.pdf	721.3Kb	PDF	View/ Open	Power Point Presentation
hopping.mp4	633.5Kb	MPEG-4 video	View/ Open	Hopping Video
hopping_spring_slow.mp4	123.5Kb	MPEG-4 video	View/ Open	Hopping Spring Video
slow_hopping.mp4	1.053Mb	MPEG-4 video	View/ Open	Slow Hopping Video
handout.pdf	107.0Kb	PDF	View/ Open	Handout
hopping_spring_slow_streaming.html	931bytes	HTML	View/ Open	Streaming Hopping Spring Video
hopping_streaming.html	919bytes	HTML	View/ Open	Streaming Hopping Video
presentation_roiz_streaming.html	929bytes	HTML	View/ Open	Streaming Video of Presentation
slow_hopping_streaming.html	924bytes	HTML	View/ Open	Streaming Slow Hopping Video

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Master of Science in Prosthetics and Orthotics Presentations of Projects [43]

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