Head Stabilization in Running

最近有人假设，人体解剖学的许多新方面反映了对耐力跑的适应。但是，作为两足动物，人类在对抗跑步过程中头部向前倾斜的倾向方面存在特殊问题，特别是当脚后跟接触地面时(脚后跟着地)。这里测试的假设是，人类已经进化出一种新的机制，部分收敛于四足跑步动物的机制，用于抵消头部在中等耐力速度下以弹性跑步步态时倾斜的倾向。因此，该项目将研究人类在行走和跑步过程中如何稳定头部，并将其中一些机制与四足哺乳动物进行比较。该项目的关键组成部分是一个生物力学和解剖学模型，该模型结合了行走和跑步的摆动和质量弹簧力学之间的差异。虽然人类的脖子是垂直的，头部的运动范围有限，但人类头部和肩膀之间的肌肉连接大多是分离的，主要的例外是斜方肌的一小部分(斜方肌，CCT)。人类也有项韧带，这是一种类似肌腱的结构，在类人猿中没有，但在其他哺乳动物中存在。人的颈项韧带与CCT相连，并插入头部后部。因此，当CCT收缩时，假设它将手臂的质量与头部的质量联系起来。具体地说，当手臂和肩带在后跟着地时下落时，手臂的惯性力可能会在头部倾向于向前倾斜时被动地伸展。从该模型得出的假说将在人和羊身上进行实验测试，分别在跑步机和测力板上以不同的速度和不同的任务步行和跑步，同时观察焦点。各种传感器将被用来收集关于头部、肩膀和手臂的位置、加速度和位移的数据。此外，肌电(EMG)数据将从参与头部伸展的主要肌肉中获得。就科学价值而言，这些实验的结果将有助于我们更好地理解人类在跑步时如何稳定头部的问题，这是一个研究较少的课题。虽然已经有很多关于行走的功能形态的研究，但关于跑步的研究还很少。这些结果尤其与构建和检验耐力跑在人类进化中发挥关键作用的假设有关。就更广泛的影响而言，这里计划的实验将发表在人类学和生物学杂志上，帮助整合这些相关领域的实验和进化研究，并通过皮博迪博物馆在网上发布，作为人类进化新展览的一部分。这些实验将为学生以及博士后职位提供研究机会和培训。这些结果也将对更多对跑步感兴趣的人有所帮助。

It has recently been hypothesized that many novel aspects of human anatomy reflect adaptations for endurance running. But humans, as bipeds, have special problems counteracting the tendency of the head to pitch forward during running, especially when the heel strikes the ground (heelstrike). The hypothesis tested here is that humans have evolved a novel mechanism, partially convergent with that of quadrupedal running animals, for counteracting the tendency of the head to pitch during bouncy running gaits at moderate, endurance speeds. Therefore, the project will study how humans stabilize the head during walking and running, and compare some of these mechanisms with a quadrupedal mammal.The key component of this project is a biomechanical and anatomical model that incorporates differences between the pendular and mass-spring mechanics of walking versus running. Although humans have vertically-oriented necks with restricted ranges of head movement, the muscular connections between the head and the shoulder are mostly de-coupled in humans, with the primary exception of the a small portion of the trapezius muscle (the cliedocranial trapezius, CCT). Humans also have a nuchal ligament, a tendon-like structure absent in great apes but present in other mammals. The human nuchal ligament connects with the CCT and inserts on the back of the head. Thus when the CCT contracts, it is hypothesized to link the mass of the arm with the mass of the head. Specifically, as the arm and shoulder girdle fall at heelstrike, inertial forces of the arm may passively extend the head just when it tends to pitch forward. Hypotheses derived from the model will be tested experimentally in humans and sheep during walking and running on a treadmill and force plate at a variety of speeds and with different tasks while looking at a focal point. Various sensors will be used to collect data on positions, accelerations and displacements of the head, shoulder and arms. In addition, electromyography (EMG) data will be obtained from the major muscles involved in head extension.In terms of scientific merit, the results of these experiments will help improve our understanding of the how humans stabilize their heads during running, a poorly studied subject. While there has been much research on the functional morphology of walking, less is known about running. The results are especially relevant to framing and testing the hypothesis that endurance running played a key role in human evolution. In terms of broader impact, the experiments planned here will be published in anthropology and biology journals, helping to integrate experimental and evolutionary research in these related fields, and on the web via the Peabody Museum as part of a new exhibit on human evolution. The experiments will provide research opportunities and training for students, as well as for a post-doctoral position. The results will also be useful to the wider audience of people interested in running.