CAREER: The Musculoskeletal Biomechanics and Control of Limbless Locomotion

该项目使用蛇的横向波动运动作为模型系统，研究动物如何满足和优先考虑机械和控制需求，特别是当这些需求受到限制或冲突时。陆地无肢运动，尽管被近20%的陆地脊椎动物使用，但仍未得到充分研究。在无肢运动的最普遍和最常见的横向波动模式中，弯曲的波浪向下传递，压迫环境中的结构（如植物、岩石），推动蛇前进。横向波动同时带来了几个挑战，包括满足机械动力需求，克服摩擦力，以及控制多个不断变化的接触点的力。这些要求可能相互冲突；例如，从接触点产生最有效推进力的身体姿势可能会减少肌肉力量或功率输出。该项目通过在施加不同机械和控制要求的环境中测试动物，研究蛇如何处理这种冲突，并调查是否存在减轻或避免潜在权衡的机制。这项研究将提供关于动物在运动过程中如何管理竞争需求的一般见解，特别是同时满足机械和控制需求的需求。了解无肢运动也有利于蛇仿生机器人，这是仿生机器人的目标，因为蛇具有在复杂、杂乱和狭窄的空间中移动的特殊能力。与阿克伦大学野外站合作，该项目还通过利用基于定格动画的新型基于反馈的机器人编程，消除了学生学习如何编写代码的需要，为附近的高中提供了一个独特的生物机器人推广机会，为贫困青年提供服务。生物力学的核心挑战是理解肌肉的生理特性如何影响动物的运动，通常在专门的系统中进行检查，以最大化特定的度量（例如，功率或周期频率）。然而，大多数动物必须同时满足许多独立的机械和控制需求，并且可以通过多种方式调节它们的运动来实现这一目标。本项目使用蛇的陆地横向波动作为模型系统，以了解动物如何满足这些需求，特别是当需求冲突时。地面无肢运动以摩擦为主导的力学对机械力和功率输出提出了直接的要求，这些要求将直接从仪器化的测试场所测量出来。蛇运动中线弯曲的高度可变模式表明相应地可变的肌肉拉伤轨迹，这将通过荧光显微法测量。多重推进反作用力取决于每个接触位置的局部姿态。如果肌肉的机械输出和控制都是由身体运动学决定的，那么这两个目标之间就有可能发生冲突：反作用力方向的控制可能会损害肌肉的机械输出，反之亦然。这个项目涉及到一个新颖的推广项目，使用活体动物演示和机器人技术相结合，为学生提供生物启发的机器人设计体验，他们观察蛇的运动，假设机制，并使用蛇启发的机器人测试这些机制。两名博士后研究员和一名研究生将参与研究，从而受益于跨学科的培训和指导。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project uses locomotion by lateral undulation in snakes as a model system for investigating how animals meet and prioritize mechanical and control demands, especially when these demands are constrained or conflicting. Terrestrial limbless locomotion, despite being used by almost 20% of terrestrial vertebrates, remains understudied. In lateral undulation, the most widespread and common mode of limbless locomotion, waves of bending pass down the body, pressing against structures in the environment (e.g. plants, rocks) to propel the snake forward. Lateral undulation poses several simultaneous challenges, including meeting mechanical power demands, overcoming the force of friction, and controlling forces at multiple, constantly shifting contact points. These demands may conflict; for example, the body posture that generates the most effective propulsive force from a contact point might reduce muscular force or power output. This project addresses how snakes handle this conflict and investigates whether mechanisms exist to mitigate or avoid potential tradeoffs, by testing animals in environments that impose different mechanical and control demands. This research will provide general insights into how animals manage competing demands during locomotion, particularly the need to simultaneously meet mechanical and control demands. Understanding limbless locomotion can also benefit snake-inspired robots, a target of bio-inspired robotics due to the exceptional ability of snakes to move through complex, cluttered, and confined spaces. In partnership with the University of Akron field station, the project also provides a unique outreach opportunity in bio-inspired robotics to nearby high schools serving economically disadvantaged youth, by leveraging a new type of feedback-based robotic programming based on stop-motion animation to eliminate the need for students to learn how to write code.A central challenge of biomechanics is understanding how the physiological properties of muscle influence the movements of animals, often examined in specialized systems adapted to maximize a particular metric (e.g., power or cycle frequency). However, most animals must meet numerous independent mechanical and control demands simultaneously and can modulate their movements in a wide variety of ways to accomplish this. This project uses terrestrial lateral undulation in snakes as a model system to understand how animals meet these demands, particularly when the demands conflict. The friction-dominated mechanics of terrestrial limbless locomotion impose straightforward demands on mechanical force and power output, which will be directly measured from instrumented test arenas. The highly variable patterns of midline bending in snake locomotion suggest correspondingly variable muscle strain trajectories, which will be measured via fluoromicrometry. The multiple propulsive reaction forces depend upon local posture at each contact location. If both muscle mechanical output and control are determined by body kinematics, there is potential for conflict between these goals: control of reaction force orientation may compromise muscle mechanical outputs, and vice versa. This project involves a novel outreach program using a combination of live-animal demonstrations and robotics to provide students with a bio-inspired robotics design experience in which they observe a snake’s movements, hypothesize mechanisms, and test those mechanisms using snake-inspired robots. Two post-doctoral fellows and a graduate student will contribute to the research, thereby benefitting from interdisciplinary training and mentoring.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.