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发挥作用的核心问题。它是在肌肉功能如何与肌肉结构和纤维组成相关地调节以适应运动需求的变化的背景下这样做的。这些问题将通过在体内记录力（肌腱扣传感器），长度变化（sonomicrometry）和神经激活（肌电图）的关键肢体肌肉在两个动物模型：四足山羊和双足珍珠鸡。将从训练在跑步机上以不同步态和等级以一定速度移动的动物中获得测量结果（水平vs倾斜vs下降），以解决以下假设：（i）具有局灶性骨骼附着的肌肉内的区域激活和分数长度变化在沿着肌束轴和不同肌束区域之间是均匀的，但是在具有更宽的附着和更复杂的结构的肌肉中可能不同;结果，（ii）在执行给定运动任务的肌肉内，激活的神经束的定时和应变是均匀的;和（iii）具有长纤维的近端肌肉占机械功调制的大部分;而具有长肌腱的远端短纤维肌肉等距收缩以获得更经济的力产生和肌腱弹性节省。机械工作率与运动等级的差异将与观察到的关键肢体肌肉的体内力-长度行为的变化有关。当动物从休息加速时所做的记录将提供第二个背景来评估与肌肉结构有关的工作调制。地面反作用力平台和高速视频记录也将被进行，以将个体肌肉的活体力、长度和EMG测量整合到整个肢体力学中。这些研究对于理解运动策略相关的运动募集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意义。在此领域的先前工作已被限制在运动的更准稳定范围内的运动功能的研究和/或肌肉长度的变化和力的发展的间接评估。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的实验方法来评估可能适用于人类的运动功能动态。因此，拟议的研究将对开发更有效的物理、职业和康复治疗以及体育和锻炼训练和假肢设计具有价值。

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.