Optimization of the visco-elastic parameters describing the heel-region of a prosthesis

Johnston, Thomas R.; Hubbard, Mont

doi:10.1016/j.jtbi.2012.06.023

Cited by 4 publications

(2 citation statements)

References 44 publications

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“…Perhaps a relatively short effective foot length [50] limits the elastic benefits. Other possibilities include insufficient energy return due to hysteresis [49], [51] or viscoelastic properties of the prosthetic heel [52], or compensations due to imperfect socket interfaces [53]. In particular, the interface between a mechanical device and the deformable human body can present a number of challenges.…”

Section: Discussionmentioning

confidence: 99%

The role of series ankle elasticity in bipedal walking

Zelik

Huang

Adamczyk

et al. 2014

Journal of Theoretical Biology

121

111

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The elastic stretch-shortening cycle of the Achilles tendon during walking can reduce the active work demands on the plantarflexor muscles in series. However, this does not explain why or when this ankle work, whether by muscle or tendon, needs to be performed during gait. We therefore employ a simple bipedal walking model to investigate how ankle work and series elasticity impact economical locomotion. Our model shows that ankle elasticity can use passive dynamics to aid push-off late in single support, redirecting the body's center-of-mass (COM) motion upward. An appropriately timed, elastic push-off helps to reduce dissipative collision losses at contralateral heelstrike, and therefore the positive work needed to offset those losses and power steady walking. Thus, the model demonstrates how elastic ankle work can reduce the total energetic demands of walking, including work required from more proximal knee and hip muscles. We found that the key requirement for using ankle elasticity to achieve economical gait is the proper ratio of ankle stiffness to foot length. Optimal combination of these parameters ensures proper timing of elastic energy release prior to contralateral heelstrike, and sufficient energy storage to redirect the COM velocity. In fact, there exist parameter combinations that theoretically yield collision-free walking, thus requiring zero active work, albeit with relatively high ankle torques. Ankle elasticity also allows the hip to power economical walking by contributing indirectly to push-off. Whether walking is powered by the ankle or hip, ankle elasticity may aid walking economy by reducing collision losses.

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Section: Discussionmentioning

confidence: 99%

The role of series ankle elasticity in bipedal walking

Zelik

Huang

Adamczyk

et al. 2014

Journal of Theoretical Biology

121

111

View full text Add to dashboard Cite

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“…This system walks down a shallow slope without an actuator or controller; it does this by balancing the energy dissipation due to foot contact with the energy generation due to the gravitational potential energy. This walking behavior has various similarities to that of humans, and thus it has been a useful tool for elucidating the body's mechanical functions that produce energy-efficient walking [15][16][17][18][19][20][21][22][23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Formation mechanism of a basin of attraction for passive dynamic walking induced by intrinsic hyperbolicity

et al. 2016

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Passive dynamic walking is a useful model for investigating the mechanical functions of the body that produce energy-efficient walking. The basin of attraction is very small and thin, and it has a fractal-like shape; this explains the difficulty in producing stable passive dynamic walking. The underlying mechanism that produces these geometric characteristics was not known. In this paper, we consider this from the viewpoint of dynamical systems theory, and we use the simplest walking model to clarify the mechanism that forms the basin of attraction for passive dynamic walking. We show that the intrinsic saddle-type hyperbolicity of the upright equilibrium point in the governing dynamics plays an important role in the geometrical characteristics of the basin of attraction; this contributes to our understanding of the stability mechanism of bipedal walking.

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