Locomotor Dynamics of Muscle Function

描述(由申请人提供)：这项拟议的研究解决了肌肉在运动活动的动态条件下如何发挥作用的中心问题。它是在这样的背景下进行的，即肌肉功能是如何与肌肉结构和纤维组成相关的来适应运动需求的变化的。这些问题将通过在体内记录两种动物模型：四足山羊和两足珍珠鸡的关键肢体肌肉的力(肌腱扣传感器)、长度变化(声学显微镜)和神经激活(肌电图)来解决。将从受训在跑步机上以不同步态和等级(水平、倾斜和下降)以不同速度范围移动的动物身上获得测量，以解决以下假设：(I)局部骨骼附着的肌肉内的区域激活和部分长度变化沿肌束轴和在不同的肌束区域之间是一致的，但在具有更广泛的附着和更复杂的结构的肌肉中可能不同；结果是，(Ii)在执行特定运动任务的肌肉中，激活的肌束的时间和应变是均匀的；以及(Iii)具有长纤维的近端肌肉占机械工作调制的大部分；而远端短纤维肌肉与长肌腱等长收缩，以更经济的力量产生和肌腱弹性节省。不同运动等级的机械作业率的差异将与观察到的关键肢体肌肉在体内的力量-长度行为的变化有关。当动物从休息中加速时所做的记录将提供第二个背景来评估与肌肉结构相关的工作调节。还将进行地面反作用力平台和高速录像，将活体肌肉的力、长度和肌电测量整合到整个肢体力学中。这些研究对于理解与运动策略相关的运动招募模式，以及运动单位组织(和纤维类型)的区域差异如何影响运动的神经控制具有重要的意义。以前在这一领域的工作受到更多准稳定运动范围下的运动功能的研究和/或肌肉长度变化和力量发展的间接评估的限制。虽然最主要的目标是了解影响人类运动功能正常和年龄相关变化的因素，但动物研究允许使用直接的实验方法来评估可能适用于人类的运动功能的动力学。因此，拟议的研究将对开发更有效的物理、职业和康复疗法，以及运动和运动训练，以及假体设计具有价值。

DESCRIPTION (provided by applicant): The proposed research addresses the central question of how muscles function under dynamic conditions of locomotor activity. It does so in the context of how muscle function is modulated in relation to muscle architecture and fiber composition to accommodate changes in locomotor requirement. These questions will be addressed by making in vivo recordings of force (tendon buckle transducers), length change (sonomicrometry) and neural activation (electromyography) of key limb muscles in two animal models: quadrupedal goats and bipedal guinea fowl. Measurements will be obtained from animals trained to move over a range of speeds on a treadmill at different gaits and grades (level vs incline vs decline) to address the following hypotheses: (i) regional activation and fractional length change within muscles that have focal skeletal attachments is uniform both along a fascicle axis and between differing fascicle regions, but may vary in muscles with broader attachments and more complex architectures; as a result, (ii) the timing and strain of activated fascicles are homogeneous within a muscle performing a given motor task; and (iii) proximal muscles with long fibers account for the majority of mechanical work modulation; whereas distal short-fibered muscles with long tendons contract isometrically for more economical force production and tendon elastic savings. Differences in mechanical work rate with locomotor grade will be related to observed changes in the in vivo force-length behavior of key limb muscles. Recordings made while animals accelerate from rest will provide a second context to evaluate work modulation in relation to muscle architecture. Ground reaction force-platform and high-speed video recordings will also be carried out to integrate the in vivo force, length and EMG measurements of individual muscles into whole-limb mechanics. These studies have important consequences for understanding patterns of motor recruitment in relation to locomotor strategy and how regional differences in motor unit organization (and fiber type) may influence the neural control of movement. Prior work in this area has been limited by studies of motor function under more quasi-steady ranges of movement and/or indirect assessment of muscle length change and force development. Although an overarching goal is to understand factors that influence normal and age-related changes in human motor function, animal studies allow direct experimental approaches for assessing the dynamics of motor function that are likely to apply to humans. Consequently, the proposed studies will have value for developing more effective physical, occupational and rehabilitative therapies, as well as for sports and exercise training, and prosthetics design.