Mechanics and energetics of stable bipedal locomotion in uneven terrain: Does a trade-off exist between economy and stability?

对人类和鸟类行走和跑步的研究表明，尽管腿部解剖结构不同，但所有两足动物（两足动物）在平地上的移动方式相似。这一发现为经济行走和经济奔跑提供了优雅简单的理论模型。这些模型激发了技术进步，比如最快的跑道、最经济的两足机器人和简单的假肢设备，包括田径运动员奥斯卡·皮斯托瑞斯（Oscar Pistorious）穿的猎豹柔性脚（Cheetah Flex-Foot）。尽管取得了这些进步，但在不平坦的地形上，如何设计既稳定又经济的假肢仍然是一个挑战。在自然地形上行走和跑步需要经常调整颠簸、台阶、洞和障碍物。然而，目前用于人类运动的假肢设备在不平坦的地形上表现不佳。虽然奥斯卡·皮斯托瑞斯戴的屈脚假肢提供了很高的经济性，使他能够跑很远的距离，但它不能根据路缘或楼梯等地形的变化进行调整。像电动假肢装置这样的进步可以提高在不平坦地形上的机动性，但目前使用有限，因为它们消耗太多能量，电池电量很快就会耗尽。新的义肢和其他在各种地形上表现良好的行动辅助工具可以极大地改善行动不便者的生活质量，包括截肢者和有跌倒风险的老年人。与这些技术相比，人类和鸟类在各种地形中实现了卓越的稳定性和运动经济性。然而，我们对它们是如何做到这一点知之甚少。目前的步行和跑步模型主要是基于在完全光滑、均匀的地形（如跑道或跑步机）上的运动研究，这种情况在自然界中很少存在。长期以来，人们一直认为在运动的经济性和稳定性之间存在着一种权衡。这个想法从未被验证过，因为关于走路和跑步稳定性的研究太少了。这个项目将通过比较六种地面鸟类的稳定策略和运动的能量成本来解决这个问题。我们将测量鸟类在不平坦的地形条件下行走和奔跑时的力学、稳定性和能量消耗。这将揭示两足动物如何根据地形条件、速度和步态选择不同的运动策略。地面鸟类是这项研究的理想研究动物，因为它们是多种两足运动员，生活在广泛的栖息地，跨度很大：从100克以下的鹌鹑到100公斤以上的鸵鸟。通过对地面鸟类的研究，该项目将开发出适用于各种动物和地形条件的稳定双足运动的简单模型。这些模型将揭示稳定性和经济性的基本原理，这可能直接影响假肢、矫形器和有腿机器人的设计。一个重要的观察结果是，小鸟走路和跑步时都是蹲着、弯曲腿的姿势，而大鸟移动时则是相对直腿的姿势。腿部姿势和解剖结构的差异可能反映了小型鸟类对稳定性和大型鸟类对经济性的更大适应。对于在同一地形中移动的小型和大型动物，地形高度的任何变化都会对小型动物的腿长产生较大的影响。因此，对于小动物来说，世界是一个相对“粗糙”的地方，需要强大的稳定性。该项目将比较小型和大型鸟类使用的稳定策略，并确定小型鸟类是否更稳定。这项研究将揭示两足动物如何在不平坦的地形上行走和奔跑而不摔倒或受伤。没有跌倒和受伤的活动对老年人和步态障碍者的健康尤为重要。这些发现可能在这些领域产生重大影响，激发人类跌倒预防、步态康复以及假肢、矫形器和其他活动辅助设备设计方面的创新。

Studies of walking and running in humans and birds have revealed that all two legged animals (bipeds) move in similar ways over level ground, despite differences in leg anatomy. This finding has led to elegantly simple theoretical models for economic walking and running. These models have inspired technological advances such as the fastest running tracks, the most economic bipedal robots, and simple prosthetics devices, including the Cheetah Flex-Foot worn by track athlete Oscar Pistorious. Despite these advances, the design of prosthetics that can move with both stability and economy over uneven terrain remains a challenge. Walking and running in natural terrain requires frequent adjustment for bumps, steps, holes and obstacles. Yet, current prosthetic devices for human locomotion perform poorly over uneven terrain. Although the flex-foot prosthetic worn by Oscar Pistorious provides high economy, allowing him to run long distances, it does not adjust for variations in terrain such as kerbs or stairs. Advances such as motorised prosthetic devices can improve mobility in uneven terrain, but currently have limited use because they consume too much energy and run out of battery power quickly. New prosthetics and other mobility aids that perform well in varied terrain could vastly improve quality of life for those with limited mobility, including amputees and ageing individuals at risk for falls. In comparison to these technologies, humans and birds achieve remarkable stability and economy of movement in varied terrain. However, we understand very little about how they accomplish this. Current models of walking and running are based mostly on studies of movement over completely smooth, uniform terrain (such as a track or treadmill), which rarely exist in nature. It has long been supposed that a trade-off exists between economy and stability of locomotion. This idea has never been tested because so little research exists on stability of walking and running. This project will address this problem by by comparing stabilising strategies and energy cost of locomotion among six species of ground birds. We will measure mechanics, stability and energetic cost as birds walk and run over uneven terrain conditions. This will reveal how bipeds choose among different movement strategies depending on terrain condition, speed and gait. Ground birds are ideal study animals for this research because they are diverse bipedal athletes, live in broad range of habitats, and span a large size range: from quail under 100 grams to ostrich over 100 kilograms. Through study of ground birds, this project will develop simple models for stable bipedal locomotion that apply to a broad range of animals and terrain conditions. The models will reveal basic principles for stability and economy that could directly impact upon the design of prosthetics, orthotics and legged robots. One important observation is that small birds walk and run with a crouched, bent-leg posture, and large birds move with a relatively straight-leg posture. The difference in leg posture and anatomy likely reflects greater adaptation for stability in small birds and economy in large birds. For small and large animals moving in the same terrain, any change in terrain height will be a larger fraction of a small animal's leg length. Consequently, the world is a relatively 'rough' place for small animals, requiring robust stability. This project will compare stability strategies used by small and large birds and determine whether small birds are more stable. This research will reveal how bipeds walk and run over uneven terrain without falls or injury. Mobility without falls and injury is particularly important for the wellbeing of ageing and gait impaired individuals. The findings are likely to have high impact in these areas, inspiring innovation in human fall prevention, gait rehabilitation, and the design of prosthetics, orthotics and other mobility assistance devices.