Locomotor Dynamics of Muscle Function

描述（由申请人提供）：拟议的研究解决了在运动活动的动态条件下肌肉如何功能的核心问题。它是在肌肉功能如何调节与肌肉结构和纤维组成有关的背景下进行的，以适应运动需求的变化。这些问题将通过对两种动物模型（四足山羊和两足珍珠鸡）的主要肢体肌肉的力（肌腱扣传感器）、长度变化（声速测量法）和神经激活（肌电图）的体内记录来解决。将对在跑步机上以不同步态和坡度（水平、倾斜、下降）在一定速度范围内训练的动物进行测量，以解决以下假设：(i)在具有局点骨骼附着物的肌肉中，区域激活和部分长度变化沿束轴和不同束带区域是均匀的，但在附着物更广泛和结构更复杂的肌肉中可能会有所不同；因此，（ii）在执行给定运动任务的肌肉中，激活的肌束的时间和张力是均匀的；（iii）具有长纤维的近端肌肉占机械功调节的大部分；而远端短纤维肌肉与长肌腱等距收缩更经济的力量生产和肌腱弹性节约。机械功率与运动等级的差异将与观察到的关键肢体肌肉在体内力长度行为的变化有关。当动物从休息加速时所做的记录将为评估与肌肉结构相关的工作调节提供第二个背景。地面反作用力平台和高速视频记录也将进行，以整合在体内的力，长度和肌电测量单个肌肉的全肢力学。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元组织（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意义。在这一领域的先前工作受到更多准稳定运动范围下的运动功能研究和/或间接评估肌肉长度变化和力量发展的限制。虽然总体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，但动物研究允许直接实验方法来评估可能适用于人类的运动功能动力学。因此，拟议的研究将对发展更有效的物理、职业和康复疗法，以及运动和运动训练以及假肢设计具有价值。

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.