Biomechanics, Control, and Energetics of Human Locomotion in the Real World

在现实世界中，人类要面对各种各样的行走表面，包括未铺砌的地面、路边石和不完美的人行道。然而，大部分关于运动的生物力学、控制和能量学的知识都局限于平坦和水平的表面。但在现实世界中，如果没有良好控制的实验室条件，也很难获得定量的生物力学数据。这些差距需要通过结合专门为现实世界设计的新技术来解决，这些新技术可以应用于控制良好的实验室研究，更好地模拟这样的环境，也可以应用于现实世界的研究，更好地量化人类如何适应不同的地面。******这个项目从两个方向架起了桥梁：实验室和现实世界。在实验室，我们将进行研究，使传统的生物力学技术适应不平坦的地形。这将通过新的方法和实验来实现。例如，我们将使用一个仪器化的跑步机（测量每条腿下的地面反作用力），它可以适应不同的表面，如不平坦的地形，变化幅度或顺应性。结合动作捕捉，这将使地形振幅对整体稳态步态、步态变异性和能量消耗的影响的完整生物力学特征成为可能。我们还将测试生物力学任务需求如何随地形变化，并检查代谢成本增加的机制基础。******我们还将检查运动在各种现实世界的环境，使用改进的生物力学捕获方法。大多数可穿戴传感器提供相对简单的措施，如步长定时，但无法获得在实验室中获得的细粒度信息。我们开发了新的算法，使用鞋装惯性测量单元来重建每只脚在空间中的轨迹，从中可以获得步幅和可变性或脚的抬起等测量，其精度可与实验室相媲美。这些方法将描述人类如何适应具有挑战性的表面，如松散的砾石或倾斜的沙子。我们还将结合这些生物力学测量与氧呼吸测量来评估代谢成本。在不平坦地形的能量成本预测中，最先进的方法是使用回归方程来考虑步行速度、负重和地形难度的粗略主观指标。通过更好地理解机械变量和代谢变量如何共同变化，将有可能更客观地表征地形难度，并更好地预测能量成本。我们还将探索长距离步态的变化，以确定疲劳对平衡和经济性的影响。这些研究将提高研究运动的能力，以及对人类在不平坦地形上的适应的理解。

Humans contend with a variety of walking surfaces in the real world, including unpaved ground, street curbs, and imperfect sidewalks. However, much of what is known about the biomechanics, control, and energetics of locomotion is confined to flat and level surfaces. But in real-world terrain, it is also difficult to gain quantitative, biomechanical data without the well-controlled conditions of the laboratory. These gaps need to be addressed through a combination of new techniques expressly designed for the real world, to be applied to well-controlled laboratory studies that better model such environments, and to real-world studies that better quantify how humans actually adapt to different ground surfaces. ******This program bridges the gap from both directions: the laboratory and the real world. In the laboratory, we will conduct studies adapting conventional biomechanics techniques to uneven terrain. This will be enabled by new methods and experiments. For example, we will use an instrumented treadmill (measuring ground reaction forces under each leg), adapted to allow for changeable surfaces such as uneven terrain, varying in amplitude or compliance. In conjunction with motion capture, this will enable full biomechanical characterization of the effect of terrain amplitude on overall steady-state gait, gait variability, and energetic cost. We will also test how biomechanical task demands vary with terrain, and examine the mechanistic basis for increased metabolic cost. ******We will also examine locomotion in a variety of real-world environments, using improved biomechanical capture methods. Most wearable sensors provide relatively simple measures such as step timing, but cannot obtain the fine-grained information obtained in the laboratory. We have developed new algorithms to use shoe-mounted inertial measurement units to reconstruct each foot's trajectory in space, from which measures such as stride length and variability, or lifting of the foot, can be obtained with accuracy comparable to laboratory. These methods will characterize how humans adapt their gait to challenging surfaces such as loose gravel or sand on an incline. We will also couple these biomechanical measures with oxygen respirometry to assess metabolic cost. The state of the art in energy cost predictions for uneven terrain is to use regression equations factoring in walking speed, load carriage, and a crude and subjective index of terrain difficulty. With better understanding of how mechanical and metabolic variables co-vary, it will be possible to characterize terrain difficulty more objectively and with better predictability for energy cost. We will also explore how gait changes over long distances, to determine how balance and economy are affected by fatigue. These studies will improve both the capabilities for studying locomotion, as well as understanding of the human adaptations on uneven terrain.