External Perturbations and Internal Mechanisms of Locomotor Performance

本研究的具体目标包括：1）确定鞋类弯曲刚度和缓冲如何影响内部肌肉骨骼特性和下肢关节运动; 2）确定鞋类修改导致的内部肌肉骨骼特性变化如何影响运动性能。 ** 该研究计划将包括一系列使用人类受试者的项目，以更好地了解外部扰动的影响，即鞋类性能的变化，内部肌肉骨骼性能和最终性能。将研究的鞋类性能是缓冲和纵向弯曲刚度。最近的研究表明，鞋类缓冲和前足弯曲刚度可以影响跑步性能，但是，影响这些性能改善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，但迄今为止尚未进行。** 对于每种性能（缓冲和弯曲刚度），将进行三次运行研究。在一系列研究中，受试者将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跑步，这些鞋具有不同的前足弯曲刚度。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，仪器跑步机来量化跑步动力学，代谢推车来量化跑步经济性2）便携式超声系统来量化跟腱应变和相应的能量储存和返回，以及3）双重荧光透视来确定足部和踝关节骨的内在运动。除了跑步测试外，运动员还将在Biodex上进行一系列的力量测量，以提供每个受试者特定的扭矩-角度-角速度关系。这些信息将用于确定肌肉收缩特性是否可以通过跑步鞋的操作来优化。**了解当鞋子变软或变硬时实际发生的肌肉骨骼变化提供了直接实施鞋类设计以影响性能的机会。此外，通过了解外部扰动如何影响运动性能的内部机制，结果可能对辅助和支持人类运动（最普遍意义上的人类性能）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).