Powered prostheses are capable of providing net positive work to amputees and have advanced in the past two decades. However, reducing amputee metabolic cost of walking remains an open problem. The Law of Intersegmental Coordination (ISC) has been observed across gaits and has been previously implicated in energy expenditure of walking, yet it has rarely been analyzed or applied within the context of lower-limb amputee gait. This law states that the elevation angles of the thigh, shank and foot over the gait cycle are not independent. In this work, we developed a method to analyze intersegmental coordination for lower-limb 3D kinematic data, to simplify ISC analysis. Moreover, inspired by motor control, biomechanics and robotics literature, we used our method to broaden ISC toward a new law of coordination of moments. We find these Elevation Space Moments (ESM), and present results showing a moment-based coordination for able bodied gait. We also analyzed ISC for amputee gait walking with powered and passive prosthesis, and found that while elevation angles remained planar, the ESM showed less coordination. We use ISC as a constraint to predict the shank angles/moments that would compensate for alterations due to a passive foot so as to mimic a healthy thigh angle/moment profile. This may have implications for improving powered prosthetic control. We developed the ISC3d toolbox that is freely available online, which may be used to compute kinematic and kinetic ISC in 3D. This provides a means to further study the role of coordination in gait and may help address fundamental questions of the neural control of human movement.

翻译：动力假肢能够为截肢者提供净正功，在过去二十年中取得了显著进展。然而，降低截肢者行走代谢成本仍是一个悬而未决的问题。节段间协调定律（ISC）已在多种步态中被观察到，且先前研究认为其与行走能量消耗相关，但该定律在下肢截肢者步态中的分析与应用仍较为罕见。该定律指出，大腿、小腿和足部在步态周期中的抬升角度并非相互独立。本研究开发了一种分析下肢三维运动学数据节段间协调的方法，以简化ISC分析。此外，受运动控制、生物力学和机器人学文献的启发，我们运用该方法将ISC拓展为新的力矩协调定律。我们发现了这些抬升空间力矩（ESM），并展示了健全步态中基于力矩的协调性结果。我们还分析了截肢者使用动力与被动假肢行走时的ISC，发现虽然抬升角度仍保持平面性，但ESM显示出较低的协调性。我们以ISC作为约束条件，预测能够补偿因被动足部导致的变化的小腿角度/力矩，从而模拟健康大腿角度/力矩曲线。这可能对改进动力假肢控制具有重要意义。我们开发了可在线免费获取的ISC3d工具箱，可用于计算三维空间中的运动学与动力学ISC。这为深入研究协调性在步态中的作用提供了工具，并可能有助于回答人类运动神经控制的基础性问题。