Variable gearing at the ankle during walking in adults and young children: implications for foot development and evolution

IF 4.6 Q2 MATERIALS SCIENCE, BIOMATERIALS
A. Zeininger, Daniel Schmitt, Jody L. Jensen, Liza J. Shapiro
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Abstract

Introduction: The human foot has evolved over the past seven million years from a relatively mobile, grasping appendage to a highly derived structure with a heel pad and longitudinal arch that can absorb shock at heel strike and weight-bearing yet also function as a powerful lever at toe-off. It has been proposed that the modern human foot evolved to allow our species to use “variable gearing” during walking and running. In this model, the gears of the human foot are defined relative to the ankle center of rotation as R, the distance from the ground reaction resultant vector, and r, the distance from the calf muscle vector. The gear ratio defines the torque generated to propel the body or stretch the triceps surae muscles. We test the hypothesis that variable gearing is associated with modern human pedal anatomy and a heel-to-toe rollover that allows a shift from “low gear” to “high gear” during stance.Methods: Using force plate and video analysis, we examined variable gearing in adults and children engaging in adult heel strike (AHS = 35), flat foot contact (FFC = 39), or initial heel contact (IHC = 26).Results and Discussion: Our hypothesis was partly supported. Although variable gearing was observed in IHC steps and was greater than in FFC steps, it was not as developed as in AHS steps. This may be related to anatomical and motor control differences between juvenile and adult feet, suggesting that adult anatomy, including a high arch, and neural control are critical for full use of variable gearing and that this feature would have evolved in later hominins around two million years ago with the appearance of a fully modern foot.
成人和幼儿行走时踝关节的齿轮变化:对足部发育和进化的影响
导言:在过去的七百万年里,人类的足部从一个相对移动的抓握附属物进化成了一个具有跟垫和纵向足弓的高度衍生结构,可以在脚跟着地和负重时吸收冲击力,也可以在脚趾着地时发挥强大的杠杆作用。有人提出,现代人足的进化是为了让我们这个物种在行走和奔跑时使用 "可变齿轮"。在这个模型中,人脚的齿轮相对于脚踝旋转中心定义为 R(与地面反应结果矢量的距离)和 r(与小腿肌肉矢量的距离)。齿轮比决定了推动身体或拉伸肱三头肌所产生的扭矩。我们测试的假设是,可变齿轮与现代人的脚蹬解剖结构和脚跟到脚趾的翻转有关,这种翻转允许在站立过程中从 "低速档 "转换到 "高速档":通过力板和视频分析,我们研究了成人和儿童在成人脚跟着地(AHS = 35)、平足接触(FFC = 39)或初始脚跟接触(IHC = 26)时的可变齿轮:我们的假设得到了部分支持。虽然在 IHC 步中观察到了可变齿轮,而且比在 FFC 步中观察到的更大,但其发展程度不如在 AHS 步中。这可能与幼年足和成年足在解剖学和运动控制方面的差异有关,表明成年足的解剖学(包括高足弓)和神经控制是充分利用可变齿轮的关键,而且这一特征应该是在大约200万年前随着完全现代足的出现而在后来的类人猿中进化出来的。
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来源期刊
ACS Applied Bio Materials
ACS Applied Bio Materials Chemistry-Chemistry (all)
CiteScore
9.40
自引率
2.10%
发文量
464
期刊介绍: ACS Applied Bio Materials is an interdisciplinary journal publishing original research covering all aspects of biomaterials and biointerfaces including and beyond the traditional biosensing, biomedical and therapeutic applications. The journal is devoted to reports of new and original experimental and theoretical research of an applied nature that integrates knowledge in the areas of materials, engineering, physics, bioscience, and chemistry into important bio applications. The journal is specifically interested in work that addresses the relationship between structure and function and assesses the stability and degradation of materials under relevant environmental and biological conditions.
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