Walking with increased ankle pushoff decreases hip muscle moments

Lewis, Cara L.; Ferris, Daniel P.

doi:10.1016/j.jbiomech.2008.05.013

Cited by 157 publications

(118 citation statements)

References 26 publications

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“…Likewise, increased hip powering (pulling the limb into swing) may reduce ankle push-off demands. There is empirical evidence in support of both of these contentions: increased ankle push-off reducing hip work (Caputo and Collins, 2014;Koller et al, 2015;Lewis and Ferris, 2008) and increased hip powering reducing ankle push-off (Lenzi et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

A unified perspective on ankle push-off in human walking

Zelik

Adamczyk

2016

Journal of Experimental Biology

122

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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: Discussionmentioning

confidence: 99%

A unified perspective on ankle push-off in human walking

Zelik

Adamczyk

2016

Journal of Experimental Biology

122

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“…When humans walk at a comfortable speed (1.3 m s −1 ), maximum power output of the extending ankle joint during push-off P max,Ank is ~180 W (Donelan et al, 2002b;Lewis and Ferris, 2008;Silverman et al, 2008;Lipfert, 2010). Thus, higher power output than the muscle fibers of the ankle extensors are capable of seems to be needed for this observed ankle extension.…”

Section: Pmax Maxmentioning

confidence: 99%

Impulsive ankle push-off powers leg swing in human walking

Lipfert¹,

Günther

Renjewski

et al. 2013

Journal of Experimental Biology

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Rapid unloading and a peak in power output of the ankle joint have been widely observed during push-off in human walking. Modelbased studies hypothesize that this push-off causes redirection of the body center of mass just before touch-down of the leading leg. Other research suggests that work done by the ankle extensors provides kinetic energy for the initiation of swing. Also, muscle work is suggested to power a catapult-like action in late stance of human walking. However, there is a lack of knowledge about the biomechanical process leading to this widely observed high power output of the ankle extensors. In our study, we use kinematic and dynamic data of human walking collected at speeds between 0.5 and 2.5 m s −1 for a comprehensive analysis of push-off mechanics. We identify two distinct phases, which divide the push-off: first, starting with positive ankle power output, an alleviation phase, where the trailing leg is alleviated from supporting the body mass, and second, a launching phase, where stored energy in the ankle joint is released. Our results show a release of just a small part of the energy stored in the ankle joint during the alleviation phase. A larger impulse for the trailing leg than for the remaining body is observed during the launching phase. Here, the buckling knee joint inhibits transfer of power from the ankle to the remaining body. It appears that swing initiation profits from an impulsive ankle push-off resulting from a catapult without escapement.

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“…Although the majority of AFO research is conducted using populations with myelomeningocele, spastic diplegia, hemiparesis, and multiple sclerosis, a common feature of AFO use in these populations and those with limb salvage is plantarflexor weakness. Gait is hindered by limited plantarflexor power [26,27] for which the hip generally compensates [24,26]. The resulting gait is mechanically inefficient [8,22] and leads to elevated energy cost [29,39].…”

Section: Introductionmentioning

confidence: 99%

How Does Ankle-foot Orthosis Stiffness Affect Gait in Patients With Lower Limb Salvage?

Esposito

Blanck

Harper

et al. 2014

Clinical Orthopaedics &Amp; Related Research

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Background Ankle-foot orthoses (AFOs) are commonly prescribed during rehabilitation after limb salvage. AFO stiffness is selected to help mitigate gait deficiencies. A new custom dynamic AFO, the Intrepid Dynamic Exoskeletal Orthosis (IDEO), is available to injured service members but prescription guidelines are limited. Questions/purposes In this study we ask (1) does dynamic AFO stiffness affect gait parameters such as joint angles, moments, and powers; and (2) can a given dynamic AFO stiffness normalize gait mechanics to noninjured control subjects? Methods Thirteen patients with lower limb salvage (ankle arthrodesis, neuropathy, foot/ankle reconstruction, etc) after major lower extremity trauma and 13 control subjects who had no lower extremity trauma and wore no orthosis underwent gait analysis at a standardized speed. Patients wore their custom IDEO with posterior struts of three different stiffnesses: nominal (clinically prescribed stiffness), compliant (20% less stiff), and stiff (20% stiffer). Joint angles, moments, powers, and ground reaction forces were compared across the varying stiffnesses of the orthoses tested and between the patient and control groups. Results An increase in AFO compliance resulted in 20% to 26% less knee flexion relative to the nominal (p = 0.003) and stiff (p = 0.001) conditions, respectively. Ankle range of motion and power generation were, on average, 56% (p \ 0.001) and 63% (p \ 0.001), respectively, less than controls as a result of the relatively fixed ankle position. Conclusions Patients with limb salvage readily adapted to different dynamic AFO stiffnesses and demonstrated few Support was provided by

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Walking with increased ankle pushoff decreases hip muscle moments

Cited by 157 publications

References 26 publications

A unified perspective on ankle push-off in human walking

A unified perspective on ankle push-off in human walking

Impulsive ankle push-off powers leg swing in human walking

How Does Ankle-foot Orthosis Stiffness Affect Gait in Patients With Lower Limb Salvage?

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