How Compliance of Surfaces Affects Ankle Moment and Stiffness Regulation During Walking.

Kaifan Xie,Yueling Lyu,Rong Song,Xianyi Zhang

doi:10.3389/fbioe.2021.726051

Kaifan Xie, Yueling Lyu + Show 2 more

Open Access

https://doi.org/10.3389/fbioe.2021.726051

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Abstract

Humans can regulate ankle moment and stiffness to cope with various surfaces during walking, while the effect of surfaces compliance on ankle moment and stiffness regulations remains unclear. In order to find the underlying mechanism, ten healthy subjects were recruited to walk across surfaces with different levels of compliance. Electromyography (EMG), ground reaction forces (GRFs), and three-dimensional reflective marker trajectories were recorded synchronously. Ankle moment and stiffness were estimated using an EMG-driven musculoskeletal model. Our results showed that the compliance of surfaces can affect both ankle moment and stiffness regulations during walking. When the compliance of surfaces increased, the ankle moment increased to prevent lower limb collapse and the ankle stiffness increased to maintain stability during the mid-stance phase of gait. Our work improved the understanding of gait biomechanics and might be instructive to sports surface design and passive multibody model development.

Highlights

The ankle joint plays several important roles such as shock absorption, stability, and propulsion in different subphases of the gait cycle, which can be realized by the regulations of ankle biomechanics (Robertson and Winter, 1980; Neptune et al, 2001)
During the 60–91% of stance phase, vertical ground reaction forces (GRFs) decreased as compliance of surfaces increased within the force plate, ethylene–vinyl acetate copolymer (EVA), and expandable polyethylene (EPE) surfaces (p < 0.001, effect size f: 0.42–0.59)
As almost no difference in the vertical and anterior–posterior GRFs among surfaces was found during this subphase, the larger ankle plantar flexion moment observed on surfaces with increased compliance might be due to larger moment arms

Summary

Introduction

The ankle joint plays several important roles such as shock absorption, stability, and propulsion in different subphases of the gait cycle, which can be realized by the regulations of ankle biomechanics (Robertson and Winter, 1980; Neptune et al, 2001). The ankle joint adapts its biomechanical properties (Winter, 1995; Bayram and Bayram, 2018). These adaptions include the regulations of ankle moment and stiffness (Kepple et al, 1997; Whitmore et al, 2019). Ankle moment and stiffness are both regulated primarily by ankle muscles and can be regulated at different levels by co-activation of the agonist and antagonist muscles. An inverse dynamics approach has been used to estimate ankle moment by solving for the unknowns in the algebraic equations which take segmental anthropometry, lever arms, and movements measured as input (Vaughan and Christopher, 1996). Ankle stiffness is an important component of ankle impedance and can be estimated from the isolated angle and torque response to the perturbation applied to the ankle

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