Doctoral Dissertation Improvement: Pelvic Shape and Locomotor Cost: an Empirical Test of Biomechanical Models of the Hip

采用惯常的两足运动需要人类骨盆形状的重大改变，这些变化在至少340万年前的化石记录中非常明显。然而，已经灭绝的古人类物种之间骨盆宽度的变化，以及现代人类性别二态性的形式，导致了骨盆宽导致运动效率低或效果差的假设。这一假设基于生物力学模型，该模型表明，更宽的骨盆减少了髋关节稳定肌（髋关节外展肌）的机械优势，从而增加了肌肉力量的产生，增加了步行和跑步的代谢成本。然而，这个模型从未在运动过程中进行过测试。本研究将测试骨盆宽度的骨骼测量是否与运动过程中的相关机械尺寸相关，并确定髋关节外展肌与运动成本的具体关系。将收集30名患者的运动学、动力学和耗氧量数据以及磁共振成像，以确定与髋外展肌激活相关的机械优势、肌肉力量和能量消耗。一旦建立了这些关系，它们就可以用来解决现存人类骨盆形状变化的能量后果，并对已灭绝的人族分类群的运动效率进行推断。对早期古人类运动成本的精确重建将有助于检验有关两足动物进化的选择压力的假设。此外，量化骨骼形态和运动成本之间的关系，有助于理解脑和身体大小的重大变化所需要的能量调节，以及在人属进化过程中所看到的范围和饮食模式的改变。与人类大脑和身体尺寸增加相关的分娩变化的运动后果也可以解决。此外，建立一个新的经验验证的运动过程中的髋关节生物力学模型在矫形外科中具有重要的应用，在矫形外科中，确定对髋关节发育不良和骨关节炎等疾病的适当治疗需要准确评估髋关节应力、地面和肌肉力。

The adoption of habitual bipedal locomotion required major alterations in the pelvic shape of hominins, changes which are clearly evident in the fossil record by at least 3.4 million years ago. However, variation in pelvic width both between extinct hominin species, and in the form of sexual dimorphism among modern humans, has led to the hypothesis that wider pelves result in less efficient or less effective locomotion. This hypothesis is based on biomechanical models which suggest that wider pelves diminish the mechanical advantage of the hip stabilizer muscles (hip abductors) thereby increasing muscle force production and increasing the metabolic cost of walking and running. However, this model has never been tested during locomotion. This study will test whether skeletal measures of pelvic width are correlated with relevant mechanical dimensions during locomotion, and determine how the hip abductors are specifically related to locomotor cost. Kinematics, kinetics, and oxygen consumption data will be collected on 30 individuals along with magnetic resonance imaging to determine the mechanical advantage, muscle force, and energetic cost associated with activation of the hip abductors. Once these relationships are established, they can be used to address the energetic consequences of variation in pelvic shape between living humans and make inferences about locomotor efficiency in extinct hominin taxa. Accurate reconstructions of locomotor cost in early hominins will aid in testing hypotheses about the selective pressures responsible for the evolution of bipedalism. Furthermore, quantifying the relationship between skeletal morphology and locomotor cost is relevant to understanding the energetic accommodations required by the major changes in brain and body size, and alterations in ranging and dietary patterns seen with the evolution of the genus Homo. The locomotor consequences of changes in parturition related to these increases in brain and body size in Homo can also be addressed. Additionally, establishing a new empirically tested biomechanical model of the hip during locomotion has important applications in orthopedics, where determining proper treatment for conditions such as hip dysplasia and osteoarthritis require accurate assessment of hip joint stresses, and ground and muscle forces.