Biomechanics and neuromuscular control of maneuvering flight

动物的机动能力可以决定它是否能成功地躲避捕食者、捕捉食物，以及其他决定生死的基本行为。大多数关于动物运动的生物力学研究都涉及弹道运动、短暂运动或稳态运动的开始或维持，因为这些可以在实验室中最容易地进行研究。因此，机动性是动物运动中最重要但却最不为人所知的方面之一。以前的研究主要沿着两个独立的方向发展：1)动物形态学的研究解释了身体和四肢的大小和形状如何影响机动的效率和动力学。神经肌肉生理学的研究揭示了动物为特定动作提供动力的机制。然而，有能力产生大量肌肉力量的动物，例如那些悬停或缓慢飞行的动物，可能能够克服由次优形态带来的效率成本，从而产生快速但低效的动作。提出的工作将检验一个假设，即当肌肉产生能量的能力较低时，由形态施加的限制是最强的。研究将集中在蜂鸟非凡的机动飞行上，因为这些动物生活在广阔的海拔范围内，这为不同的肌肉力量能力提供了自然实验。将采用两种实验方法。第一种是利用大视场跟踪系统研究无约束飞行轨迹。计算机视觉技术将用于将这些复杂的运动分解为称为运动基元的基本单位。作为一个粗略的类比，这些元素的功能就像古典芭蕾中所表演的动作，如旋转或转体舞，它们串在一起形成一个完整的舞蹈。因此，运动原语为描述动物运动的复杂性提供了重点。第二种方法将检查运动原语背后的生物力学和神经生理学。这两种方法相互提供信息，并将允许对可操作性进行定量描述，并对其局限性进行机械理解。

The ability of an animal to maneuver can determine its success at avoiding predators, catching food, and other fundamental behaviors that define the margin between life and death. Most research on the biomechanics of animal motion has concerned the initiation or maintenance of ballistic, brief, or steady state movements because these can be studied most readily in the laboratory. Maneuverability is therefore one of the most important but least understood aspects of animal locomotion. Previous research has progressed along two independent tracks: 1) Studies of animal morphology have explained how the size and shape of the body and the limbs influence the efficiency and dynamics of maneuvering. 2) Studies of neuromuscular physiology have revealed the mechanisms that animals use to power particular maneuvers. However, animals with the ability to generate substantial muscle power, such as those that hover or fly slowly, may be able to overcome efficiency costs imposed by suboptimal morphology to generate rapid but inefficient maneuvers. The proposed work will test the hypothesis that the limitations imposed by morphology are strongest when muscle power-generating capacity is low. Research will focus on the remarkable maneuvering flight of hummingbirds because these animals inhabit broad elevational ranges, which provide natural experiments for varying muscle power capacity. Two experimental approaches will be employed. The first is to use a wide field tracking system to study unconstrained flight trajectories. Techniques in computer vision will be used to decompose these complex movements into fundamental units called motion primitives. As a coarse analogy, these elements function like the movements performed in classical ballet such as pirouettes or entrechats, which are strung together to form a complete dance. Motion primitives therefore provide focus for describing the complexities of animal motion. The second approach will examine the biomechanics and neurophysiology underlying the motion primitives. The two approaches are reciprocally informative and will allow for a quantitative description of maneuverability and a mechanistic understanding of its limits.