Integrative Primate Gait Dynamics

直到最近，对动物运动的机械学研究经常记录下稳态的、线性的过程，通常是在高度人工的底物上(例如跑步机)。在它们的自然栖息地，动物们停下来，上下移动，使用各种底物，并改变方向。灵长类运动技能的特点当然是巨大的变异性。由于树上的辐射，所有灵长类动物至少会在树上呆一段时间。在这里，他们面临着不连续和不稳定的衬底，需要不断地调整和频繁的旋转。因此，几乎可以肯定，现实世界中的步态机制与步态实验室中通常研究的步态机制是不同的。在这个项目中，Demes将解决步态可变性的两个方面：(1)肢体骨骼负荷的可变性，和(2)步态力学对树栖底物的响应的调节。(1)四肢骨骼负荷通常被描述为刻板印象，但这种描述是基于对动物以稳定速度线性移动的研究。在这项研究中，灵长类动物在跨过力传感器时将执行各种运动任务(线性前进和方向变化，地面和模拟的分支)。Demes将结合肢体位置数据(通过视频获得)来评估作用在他们肢体上的反作用力，从而间接测试肢体骨骼暴露在弯曲状态下的变化。反过来，这些对于理解长骨横截面中的形状变化是重要的。除了测试一系列的运动模式外，树栖物种和陆地物种都将参与这项研究。这将测试与树栖运动相关的可变载荷制度和圆形骨骼横截面的概念，以及与陆地运动相关的刻板载荷和椭圆形骨骼横截面的概念。(2)已经证明，灵长类，特别是树栖灵长类，使用顺从(而不是僵硬)的步态，使在薄而不稳定的基质上旅行更安全。这种步态减少了身体重心的垂直波动。然而，这些波动是节能摆和弹簧机构所必需的。Demes将通过跟踪树栖和陆地灵长类动物在地面和模拟树枝上移动时质心的波动，来分析是否在顺从步态的优势和能源效率之间存在权衡。位于石溪的灵长类运动实验室是一个独特的设施，在过去的30年里对灵长类功能形态领域做出了重大贡献。许多学生和博士后研究员在这里接受过培训，他们现在是实验研究的领导者。该项目为研究生提供了进一步培训的机会。这项研究涉及的两个方面是灵长类功能形态的基础：一是测试功能形态的范式，以此为基础解释化石长骨骨干形状；另一方面是解决灵长类步态专门化的潜在适应性权衡。

Until recently, mechanistic studies of animal locomotion have routinely recorded steady-state, linear progression, often on highly artificial substrates (e.g., treadmills). In their natural habitats, animals stop and go, move up and down, use a variety of substrates, and change direction. Great variability certainly characterizes primate locomotor repertoires. Being an arboreal radiation, all primates spend at least some time in trees. Here they are faced with discontinuous and unsteady substrates that require constant adjustments and frequent turns. Gait mechanics in the real world is therefore almost certainly different from that typically studied in a gait lab. Demes will address two aspects of gait variability in this project: (1) the variability of limb bone loading, and (2) the modulation of gait mechanics in response to arboreal substrates. (1) Limb bone loading is often described as stereotypic, but this characterization is based on studies of animals moving linearly at steady state speed. The primates in this study will perform a variety of motor tasks (linear progression and directional changes, overground and on simulated branches) while crossing force transducers. Demes will evaluate the reaction forces acting on their limbs in conjunction with limb position data (obtained via video), thus indirectly testing the variation in bending regimes that the limb bones are exposed to. These, in turn, are important to understand shape variation in long bone cross sections. Aside from testing a range of locomotor modalities, both an arboreal and a terrestrial species will be enrolled in this research. This will put to test notions of variable loading regimes and circular bone cross sections being associated with arboreal locomotion, and stereotypic loading and elliptical bone cross sections with terrestrial locomotion.(2) It has been demonstrated that primates, and in particular arboreal primates, use compliant (as opposed to stiff) gaits that make travel on thin and unstable substrates safer. Such gaits reduce the vertical fluctuations of the center of mass of the body. However, these fluctuations are requisite for energy-saving pendulum and spring mechanisms. Demes will analyze whether there is a tradeoff between the advantages of compliant gaits and energy efficiency by tracking the fluctuations of the center of mass of both arboreal and terrestrial primates, while they are moving overground as well as on simulated branches. The Primate Locomotion Laboratory at Stony Brook is a unique facility that has produced major contributions to the field of primate functional morphology over the last 30 years. Numerous students and postdoctoral fellows have trained here that are now leaders in experimental research. This project offers further training opportunities for graduate students. The two aspects being addressed in this research are fundamental to primate functional morphology: One tests a paradigm in functional morphology upon which interpretations of fossil long bone diaphyseal shapes are based; the other addresses potential adaptive tradeoffs of primate gait specializations.