Mechanics of In Vivo Muscle Function During Locomotion

本研究的主要目的是直接记录动物在运动过程中肢体肌肉的功能。尽管对脊椎动物骨骼肌的生理、生物化学和力学特性进行了大量的研究，但关于正常运动活动中肌肉功能的体内力学的直接数据很少。特别是，对人体肢体肌肉的研究必然依赖于对肌肉力量和延长的间接评估。通过直接在体内测量不同动物种类的肌肉所施加的力和长度变化，我们可以更好地理解肌肉是如何动态地支持和驱动动物的运动的。肌肉力的测量将通过使用植入式肌腱力传感器或在骨骼上的肌肉附着部位进行力校准的体内骨骼应变记录来完成。肌肉纤维长度变化的体内测量将使用植入肌肉内的超声发射测声电极进行。在本提案中，我们将研究两种陆生和两种飞行物种的肌肉在体内的表现。在对小袋鼠踝关节伸肌的研究中，这些测量将使我们能够探索肌肉-肌腱“弹簧”中弹性能量储存的要求，以保存能量消耗，如何影响神经系统激活这些肌肉的动力跳跃，以及动物加速和改变方向的需要。在对白来角鸡内侧（MG）和外侧（LG）腓肠肌的研究中，我们将研究在行走和跑步过程中肌肉力量产生的增加与缩短的关系。这两种肌肉的不同纤维特性（LG：主要是快的，MG：主要是慢的），结合力输出的独立记录，提供了一个独特的机会来研究单个肌肉内的再循环。在第三组实验中，我们将直接测量鸽子和乌鸦在飞行过程中胸肌的力量产生和纤维缩短。这些测量将提供第一个直接测量肌肉机械动力，以及整个动物动力，在一个脊椎动物物种的运动过程中。这些研究将扩展我们之前的工作，该工作开发了骨骼应变方法，以测量椋鸟和鸽子飞行时胸肌直接产生的体内力。总之，大多数骨骼肌力学的研究要么依赖于实验控制的模拟，在准静态条件下，孤立的整个肌肉或肌肉纤维束的缩短和力的发展，不太可能适用于进行正常运动的肌肉。因此，从拟议的研究中获得的结果将提供有关正常功能条件下肌肉动态力-速度特性的有价值的信息。从这些研究中获得的结果将有助于更好地建立动物运动中肌肉功能的一般原理，以及与运动控制和机器人研究相关。＊＊＊

9306793 Biewener The main objective of this research is to record directly how limb muscles function during the locomotion of animals. Despite the considerable interest and extensive research that has been carried out on the physiology, biochemistry and mechanical properties of vertebrate skeletal muscles, little direct data exist concerning the in vivo mechanics of muscle of function during normal locomotor activity. In particular, studies of human limb muscles necessarily rely on the indirect assessments of muscle force and lengthening . By making direct in vivo measurements of the forces exerted by select muscles and length changes that they undergone different animal species, we can better understand how muscles function dynamically to support and power the movement of an animal. Measurements of muscle force will be made by using either implanted tendon force tranducers or by making force-calibrated in vivo skeletal strain recordings at the muscle's attachment site on the bone. In vivo measurements of muscle fiber length change will be made using ultrasound emitting sonomicrometry electrodes implanted within the muscle. In this proposal, we will examine the in vivo performance of muscles in two terrestrial and two flying species. In studies of ankle extensor muscles of wallabies, these measurements will enable us to explore how requirements for elastic energy storage in muscle-tendon 'springs' to conserve energy expenditure affect how the nervous system activates these muscles to power hopping versus the animal's need to accelerate and change direction. In studies of the medial(MG) and lateral(LG) gastrocnemius muscles in white leghorn chickens, we will study the recruitment of muscle force generation in relation to shortening during walking and running. The differing fiber characteristics of these two muscles (LG: mainly fast and MG: mainly slow), combined with independent recordings of force output, provides a unique opportunity to study recr uitment within a single muscle. I a third set of experiments we will obtain direct measurements of force generation and fiber shortening in the pectoralis muscle of pigeons and crows during flight. These measurements will provide the first direct measurement of muscle mechanical power, as well as whole animal power, during locomotion in a vertebrate species. These studies will extend our previous work, which developed the skeletal strain approach to measure in vivo force generation directly by the pectoralis during flight i starlings and pigeons. In summary, most studies of skeletal muscle mechanics have relied either on experimentally controlled simulations of shortening and force development isolated whole muscles or muscle fiber bundles under quasi-static conditions that are unlikely to apply to muscles performing normal movements. The results obtained from the proposed studies, therefore, will provide valuable information concerning the dynamic force-velocity properties of muscles under normal functional conditions. The results obtained from these studies will help to better establish general principles underlying muscle function in animal locomotion, as well as have relevance for motor control and robotics research. ***