Effective rocker shapes used by able-bodied persons for walking and fore-aft swaying: Implications for design of ankle–foot prostheses

Hansen, Alvin H.; Wang, Charles C.

doi:10.1016/j.gaitpost.2010.04.014

Cited by 41 publications

(47 citation statements)

References 16 publications

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“…These interpretations are essentially kinematic, and they represent early efforts to describe the complex interplay between foot geometry and limb dynamics. Ankle-foot interplay is not yet fully understood (Zelik et al, 2015b), but is the subject of active research in theoretical biomechanics (Adamczyk and Kuo, 2013;Adamczyk et al, 2006;Hansen and Wang, 2010;Hansen et al, 2004;Ruina et al, 2005;Srinivasan et al, 2009), as well as in applied domains such as prosthetics (Barocio et al, 2014;Boone et al, 2013;Curtze et al, 2011;Hansen and Childress, 2010;Hansen et al, 2006) and orthotics (Fatone and Hansen, 2007;Fatone et al, 2009;Vanderpool et al, 2008). Because the aforementioned kinematic perspectives do not directly address the question of what happens to the large burst of ankle push-off power, they are not amenable to the energy/work analysis and interpretation provided here.…”

Section: Alternative Perspectives On Ankle Push-offmentioning

confidence: 99%

A unified perspective on ankle push-off in human walking

Zelik

Adamczyk

2016

Journal of Experimental Biology

116

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Muscle-tendon units about the ankle joint generate a burst of positive power during the step-to-step transition in human walking, termed ankle push-off, but there is no scientific consensus on its functional role. A central question embodied in the biomechanics literature is: does ankle push-off primarily contribute to leg swing, or to center of mass (COM) acceleration? This question has been debated in various forms for decades. However, it actually presents a false dichotomy, as these two possibilities are not mutually exclusive. If we ask either question independently, the answer is the same: yes! (1) Does ankle push-off primarily contribute to leg swing acceleration? Yes. (2) Does ankle push-off primarily contribute to COM acceleration? Yes. Here, we summarize the historical debate, then synthesize the seemingly polarized perspectives and demonstrate that both descriptions are valid. The principal means by which ankle push-off affects COM mechanics is by a localized action that increases the speed and kinetic energy of the trailing push-off limb. Because the limb is included in body COM computations, this localized segmental acceleration also accelerates the COM, and most of the segmental energy change also appears as COM energy change. Interpretation of ankle mechanics should abandon an either/ or contrast of leg swing versus COM acceleration. Instead, ankle push-off should be interpreted in light of both mutually consistent effects. This unified perspective informs our fundamental understanding of the role of ankle push-off, and has important implications for the design of clinical interventions (e.g. prostheses, orthoses) intended to restore locomotor function to individuals with disabilities.

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Section: Alternative Perspectives On Ankle Push-offmentioning

confidence: 99%

A unified perspective on ankle push-off in human walking

Zelik

Adamczyk

2016

Journal of Experimental Biology

116

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“…Applications of a kinetic shape range from rehabilitation devices [16] to the design of roll over shapes for prosthetics [17,18].…”

Section: The Kinetic Shapementioning

confidence: 99%

The musical kinetic shape: A variable tension string instrument

Handžić

Reed

2014

Applied Acoustics

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In this article we present a novel variable tension string instrument which relies on a kinetic shape to actively alter the tension of a fixed length taut string. We derived a mathematical model that relates the two-dimensional kinetic shape equation to the string's physical and dynamic parameters. With this model we designed and constructed an automated instrument that is able to play frequencies within predicted and recognizable frequencies. This prototype instrument is also able to play programmed melodies.

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“…Other work has shown that the physiologic ankle-foot system conforms to a much flatter effective rocker shape during standing and fore-aft swaying (radius ~2 times leg length) [8]. The radii of the effective ankle-foot rocker shapes during walking and standing/ swaying are interesting when considered in a rocker inverted pendulum model of the human body, such as the one proposed by Gard and Childress [9].…”

Section: Introductionmentioning

confidence: 99%

“…An analysis by Hansen and Wang found that a passive prosthetic ankle would require dramatically different torsional stiffness to mimic the effective rocker shapes achieved by neural control of the nondisabled ankle-foot system for walking and standing tasks [8]. This behavior would be difficult to achieve in a passive mechanical prosthesis.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the purpose of this Rocker inverted pendulum models of (a) walking, (b) standing, and (c) prosthetic foot representing compromise between biomimetic walking and standing/swaying shapes (this study). Radius of effective ankle-foot rocker shape for walking (R walk ) is approximately 1/3 of leg length, and radius for standing/swaying (R sway ) is about 2 times leg length [8]. In this study, we examined prosthetic feet with effective rocker shapes having different flat regions representing compromises between biomimetic walking and standing/swaying shapes.…”

Section: Introductionmentioning

confidence: 99%

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Effects of flat prosthetic foot rocker section on balance and mobility

Hansen¹,

Nickel²,

Medvec³

et al. 2014

J Rehabil Res Dev

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Abstract-Previous studies have shown that the effective rocker shape of the physiologic ankle-foot system during standing and fore-aft swaying is much flatter than that used during walking, which indicates a more stable base of support for the standing/ swaying activity. Previous work suggests that flat regions within the effective rocker shapes of prosthetic ankle-foot systems could provide enhanced stability for standing balance tasks. An experimental prosthetic foot was altered to provide three different flat region lengths within its effective rocker shape. It was hypothesized that longer flat regions of the effective rocker shape would lead to improved standing balance outcomes and reduced walking performance for unilateral transtibial prosthesis users. However, no significant changes were seen in the balance and mobility outcomes of 12 unilateral transtibial prosthesis users when using the three prosthetic foot conditions. Subjects in the study significantly preferred prosthetic feet with relatively low to moderate flat regions over those with long flat regions. All the subjects without loss of light touch or vibratory sensation selected the prosthetic foot with the shortest flat region. More work is needed to investigate the effects of prosthetic foot properties on balance and mobility of prosthesis users.

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Effective rocker shapes used by able-bodied persons for walking and fore-aft swaying: Implications for design of ankle–foot prostheses

Cited by 41 publications

References 16 publications

A unified perspective on ankle push-off in human walking

A unified perspective on ankle push-off in human walking

The musical kinetic shape: A variable tension string instrument

Effects of flat prosthetic foot rocker section on balance and mobility

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