Functional Electrical Stimulation (FES) may be used in rehabilitation and assistance of people with Spinal Cord Injury (SCI). One significant application is facilitating physical exercise, mainly when combining FES with mechanical platforms, such as tricycles. However, there are still technical challenges in FES cycling protocols, such as improving control and cycling performance. Here we show how passive elements in knee orthoses during FES cycling could increase the average cadence, taking advantage of the cycling movement. Our approach is twofold. First, we simulated the forward dynamics of a detailed musculoskeletal model with passive elements over the knees. Simulations showed that specific spring stiffness ranges increased the crankset speed during cycling by more than 50%. Using parameters found in simulations, we built a pair of passive orthoses and performed experiments with one individual with SCI. During two days, the volunteer cycled with similar stimulation magnitude with and without the passive elements. We observed that the average crankset speed was higher by more than 10% when the springs were attached to the passive orthoses. These results show the potential of using passive elements to increase cycling speed for FES cycling with similar or even lower stimulation magnitude, leading to longer exercise duration.

中文翻译：

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被动膝关节矫形器协助脊髓损伤患者进行功能性电刺激循环


功能性电刺激 (FES) 可用于脊髓损伤 (SCI) 患者的康复和帮助。一项重要的应用是促进体育锻炼，主要是将 FES 与机械平台（例如三轮车）结合起来。然而，FES 骑行协议仍然存在技术挑战，例如提高控制和骑行性能。在这里，我们展示了 FES 骑行期间膝关节矫形器中的被动元件如何利用骑行运动来提高平均步频。我们的方法是双重的。首先，我们模拟了膝盖上带有被动元件的详细肌肉骨骼模型的前向动力学。模拟表明，特定的弹簧刚度范围可将骑行期间的牙盘速度提高 50% 以上。利用模拟中发现的参数，我们制作了一副被动矫形器，并对一名 SCI 患者进行了实验。在两天的时间里，志愿者在使用和不使用被动元件的情况下以相似的刺激强度骑自行车。我们观察到，当弹簧连接到被动矫形器时，平均牙盘速度提高了 10% 以上。这些结果表明，使用被动元件可以在类似甚至更低的刺激强度下提高 FES 骑行的骑行速度，从而延长运动持续时间。