External Perturbations and Internal Mechanisms of Locomotor Performance

这项研究将解决的具体目标包括：1)确定鞋类弯曲硬度和缓冲如何影响内部肌肉骨骼特性和腿部关节运动，以及2)确定鞋类改进导致的内部肌肉骨骼特性变化如何影响运动性能。这项研究计划将包括一系列项目，利用人类受试者更好地了解外部扰动的影响，即鞋类特性的变化，对内部肌肉骨骼特性和最终性能的影响。将要研究的鞋类特性是缓冲和纵向弯曲硬度。最近的研究表明，鞋垫和前脚弯曲刚度都会影响跑步成绩，但影响这些成绩提高的潜在机制尚未得到解释。为了正确识别导致这些增强的肌肉骨骼变化，需要进行内部测量，但到目前为止还没有进行过测量。对于每种性能(缓冲和弯曲刚度)，将进行三项连续研究。在一系列研究中，受试者穿着两双不同的鞋子跑步，鞋子的缓冲程度不同。在另一系列研究中，受试者将穿着两双不同的鞋子跑步，它们的前脚弯曲硬度不同。跑步研究将在跑步机上进行，并将利用：1)运动捕捉来量化跑步运动学，仪表化跑步机来量化跑步动力学，代谢车来量化跑步经济性，2)便携式超声波系统来量化跟腱拉伤和相应的能量储存和返回，以及3)双透视来确定脚部和脚踝骨骼的内在运动。除了跑步测试，运动员还将在Biodex上接受一系列力量测量，以提供每个受试者特定的扭矩-角度-角速度关系。这些信息将被用来确定是否可以通过跑鞋的手法来优化肌肉收缩特性。了解当鞋子变软或变硬时，肌肉骨骼实际会发生什么变化，这为直接实施鞋类设计来影响性能提供了机会。此外，通过了解外部扰动如何影响运动性能的内部机制，结果可能会对帮助和支持人类运动(最一般意义上的人类性能)的潜在方法产生重大影响。

The specific objectives that will be addressed by this research include: 1) to determine how footwear bending stiffness and cushioning influences internal musculoskeletal properties and lower extremity joint movements and 2) to determine how changes in internal musculoskeletal properties that result from footwear modifications influence locomotor performance. This research program will include a series of projects using human subjects to better understand the influence of external perturbations, namely changes in footwear properties, to internal musculoskeletal properties and ultimately performance. The footwear properties that will be investigated are cushioning and longitudinal bending stiffness. Recent research has shown that both footwear cushioning and forefoot bending stiffness can influence running performance, however, the underlying mechanisms affecting these performance improvements have not been explained. To properly identify the musculoskeletal changes that lead to these enhancements, internal measurements are required but to date have not been performed. For each property (cushioning and bending stiffness), three running studies will be undertaken. In one series of studies, subjects will run while wearing two different pairs of shoes with varying levels of cushioning. In another series of studies, subjects will run with two different pairs of shoes with varying forefoot bending stiffness. The running studies will be performed on a treadmill and will utilize: 1) motion capture to quantify running kinematics, an instrumented treadmill to quantify running kinetics and a metabolic cart to quantify running economy 2) a portable ultrasound system to quantify Achilles tendon strain and corresponding energy storage and return and 3) dual fluoroscopy to determine intrinsic movements of the foot and ankle bones. In addition to the running trials, athletes will undergo a series of strength measurements on a Biodex to provide each subject's specific torque-angle-angular velocity relationship. This information will be used to determine if muscle contractile properties can be optimized through manipulations in running footwear. Developing an understanding of what musculoskeletal changes actually occur when a shoe is softer or stiffer provides an opportunity to directly implement footwear designs to affect performance. Furthermore, by understanding how external perturbations affect internal mechanisms of locomotor performance, the results could have large ramifications on potential methods for assisting and supporting human locomotion (human performance in the most general sense).