A unified perspective on ankle push-off in human walking

Zelik, Karl E.; Adamczyk, Peter G.

doi:10.1242/jeb.140376

Cited by 127 publications

(99 citation statements)

References 84 publications

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“…The pendular transduction analysis performed in this study could not shed any light on the relation between mechanical external work and metabolic energy expenditure (for a discussion of this issue, see [ 5 , 6 , 23 , 25 ]). However, external work does not represent the total work done, which also includes (among others) the internal work done to move limbs relative to the COM [ 16 , 23 , 53 – 55 ] and the work done by the trailing limb against the leading limb during double support [ 35 , 56 ]. Unfortunately, the method used here does not allow measuring individual limbs GRF .…”

Section: Discussionmentioning

confidence: 99%

Pendular energy transduction within the step during human walking on slopes at different speeds

et al. 2017

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When ascending (descending) a slope, positive (negative) work must be performed to overcome changes in gravitational potential energy at the center of body mass (COM). This modifies the pendulum-like behavior of walking. The aim of this study is to analyze how energy exchange and mechanical work done vary within a step across slopes and speeds. Ten subjects walked on an instrumented treadmill at different slopes (from -9° to 9°), and speeds (between 0.56 and 2.22 m s-1). From the ground reaction forces, we evaluated energy of the COM, recovery (i.e. the potential-kinetic energy transduction) and pendular energy savings (i.e. the theoretical reduction in work due to this recovered energy) throughout the step. When walking uphill as compared to level, pendular energy savings increase during the first part of stance (when the COM is lifted) and decreases during the second part. Conversely in downhill walking, pendular energy savings decrease during the first part of stance and increase during the second part (when the COM is lowered). In uphill and downhill walking, the main phase of external work occurs around double support. Uphill, the positive work phase is extended during the beginning of single support to raise the body. Downhill, the negative work phase starts before double support, slowing the downward velocity of the body. Changes of the pendulum-like behavior as a function of slope can be illustrated by tilting the 'classical compass model' backwards (uphill) or forwards (downhill).

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Section: Discussionmentioning

confidence: 99%

Pendular energy transduction within the step during human walking on slopes at different speeds

et al. 2017

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“…We use this Review to interpret new data from experimental studies of great ape foot biomechanics, then apply these insights to the hominin fossil record to evaluate the selective forces that shaped human foot anatomy, and more broadly the evolution of bipedalism. Because we focus on the foot, we do not directly cover the ankle (talocrural and subtalar joints), but we refer readers to Pontzer et al (2014), O'Neill et al (2015 and Zelik and Adamczyk (2016) for overviews of comparative ankle biomechanics in humans and great apes. Additionally, we restrict our review to studies of terrestrial locomotion, but recommend Cartmill (1985), Richmond (2007), DeSilva (2009), Venkataraman et al (2013), Holowka et al (2017a) and Wunderlich and Ischinger (2017) for discussions of primate foot biomechanics and pedal grasping during arboreal locomotion.…”

Section: Windlass Mechanismmentioning

confidence: 99%

Rethinking the evolution of the human foot: insights from experimental research

Holowka

Lieberman

2018

Journal of Experimental Biology

109

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Adaptive explanations for modern human foot anatomy have long fascinated evolutionary biologists because of the dramatic differences between our feet and those of our closest living relatives, the great apes. Morphological features, including hallucal opposability, toe length and the longitudinal arch, have traditionally been used to dichotomize human and great ape feet as being adapted for bipedal walking and arboreal locomotion, respectively. However, recent biomechanical models of human foot function and experimental investigations of great ape locomotion have undermined this simple dichotomy. Here, we review this research, focusing on the biomechanics of foot strike, push-off and elastic energy storage in the foot, and show that humans and great apes share some underappreciated, surprising similarities in foot function, such as use of plantigrady and ability to stiffen the midfoot. We also show that several unique features of the human foot, including a spring-like longitudinal arch and short toes, are likely adaptations to long distance running. We use this framework to interpret the fossil record and argue that the human foot passed through three evolutionary stages: first, a great ape-like foot adapted for arboreal locomotion but with some adaptations for bipedal walking; second, a foot adapted for effective bipedal walking but retaining some arboreal grasping adaptations; and third, a human-like foot adapted for enhanced economy during long-distance walking and running that had lost its prehensility. Based on this scenario, we suggest that selection for bipedal running played a major role in the loss of arboreal adaptations.

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“…Although COM power may be changed through various biomechanical mechanisms, it has been demonstrated that during the step-to-step transition, the ankle generates the largest power across all the lower extremity joints of the trailing limb in both healthy (Zelik and Adamczyk, 2016) and post-stroke populations. Motivated by this biomechanical understanding of COM power generation and its previously defined relationship to metabolic power demands during walking, this investigation focused on evaluating the effects of exosuit assistance of paretic ankle function on the COM power and individual joint power generated by the paretic and non-paretic trailing limbs.…”

Section: Introductionmentioning

confidence: 99%

Biomechanical mechanisms underlying exosuit-induced improvements in walking economy after stroke

Bae

Awad

Long

et al. 2018

Journal of Experimental Biology

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Stroke-induced hemiparetic gait is characteristically asymmetric and metabolically expensive. Weakness and impaired control of the paretic ankle contribute to reduced forward propulsion and ground clearance - walking subtasks critical for safe and efficient locomotion. Targeted gait interventions that improve paretic ankle function after stroke are therefore warranted. We have developed textile-based, soft wearable robots that transmit mechanical power generated by off-board or body-worn actuators to the paretic ankle using Bowden cables (soft exosuits) and have demonstrated the exosuits can overcome deficits in paretic limb forward propulsion and ground clearance, ultimately reducing the metabolic cost of hemiparetic walking. This study elucidates the biomechanical mechanisms underlying exosuit-induced reductions in metabolic power. We evaluated the relationships between exosuit-induced changes in the body center of mass (COM) power generated by each limb, individual joint power and metabolic power. Compared with walking with an exosuit unpowered, exosuit assistance produced more symmetrical COM power generation during the critical period of the step-to-step transition (22.4±6.4% more symmetric). Changes in individual limb COM power were related to changes in paretic (=0.83, 0.004) and non-paretic (0.73, 0.014) ankle power. Interestingly, despite the exosuit providing direct assistance to only the paretic limb, changes in metabolic power were related to changes in non-paretic limb COM power (=0.80, 0.007), not paretic limb COM power (0.05). These findings contribute to a fundamental understanding of how individuals post-stroke interact with an exosuit to reduce the metabolic cost of hemiparetic walking.

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A unified perspective on ankle push-off in human walking

Cited by 127 publications

References 84 publications

Pendular energy transduction within the step during human walking on slopes at different speeds

Pendular energy transduction within the step during human walking on slopes at different speeds

Rethinking the evolution of the human foot: insights from experimental research

Biomechanical mechanisms underlying exosuit-induced improvements in walking economy after stroke

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