Luis Israel, Afschrift Maarten, Gutierrez-Farewik Elena M
KTH MoveAbility, Department of Engineering Mechanics, KTH Royal Institute of Technology, Stockholm, Sweden.
Faculty of Behavioural and Movement Sciences, VU Amsterdam, Amsterdam, The Netherlands.
PLoS Comput Biol. 2024 Sep 4;20(9):e1011837. doi: 10.1371/journal.pcbi.1011837. eCollection 2024 Sep.
Recent years have witnessed breakthroughs in assistive exoskeletons; both passive and active devices have reduced metabolic costs near preferred walking speed by assisting muscle actions. Metabolic reductions at multiple speeds should thus also be attainable. Musculoskeletal simulation can potentially predict the interaction between assistive moments, muscle-tendon mechanics, and walking energetics. In this study, we simulated devices' optimal assistive moments based on minimal muscle activations during walking with prescribed kinematics and dynamics. We used a generic musculoskeletal model with tuned muscle-tendon parameters and computed metabolic rates from muscle actions. We then simulated walking across multiple speeds and with two ideal actuation modes-motor-based and spring-based-to assist ankle plantarflexion, knee extension, hip flexion, and hip abduction and compared computed metabolic rates. We found that both actuation modes considerably reduced physiological joint moments but did not always reduce metabolic rates. Compared to unassisted conditions, motor-based ankle plantarflexion and hip flexion assistance reduced metabolic rates, and this effect was more pronounced as walking speed increased. Spring-based hip flexion and abduction assistance increased metabolic rates at some walking speeds despite a moderate decrease in some muscle activations. Both modes of knee extension assistance reduced metabolic rates to a small extent, even though the actuation contributed with practically the entire net knee extension moment during stance. Motor-based hip abduction assistance reduced metabolic rates more than spring-based assistance, though this reduction was relatively small. Our study also suggests that an assistive strategy based on minimal muscle activations might result in a suboptimal reduction of metabolic rates. Future work should experimentally validate the effects of assistive moments and refine modeling assumptions accordingly. Our computational workflow is freely available online.
近年来，辅助外骨骼取得了突破；被动和主动设备都通过辅助肌肉动作降低了接近首选步行速度时的代谢成本。因此，在多种速度下降低代谢率也应该是可以实现的。肌肉骨骼模拟有可能预测辅助力矩、肌腱力学和步行能量学之间的相互作用。在本研究中，我们根据规定运动学和动力学条件下步行时的最小肌肉激活量，模拟了设备的最佳辅助力矩。我们使用了一个具有调整后肌腱参数的通用肌肉骨骼模型，并根据肌肉动作计算代谢率。然后，我们模拟了在多种速度下行走，并采用两种理想的驱动模式——基于电机的和基于弹簧的——来辅助踝关节跖屈、膝关节伸展、髋关节屈曲和髋关节外展，并比较了计算出的代谢率。我们发现，两种驱动模式都显著降低了生理关节力矩，但并不总是能降低代谢率。与无辅助条件相比，基于电机的踝关节跖屈和髋关节屈曲辅助降低了代谢率，并且随着步行速度的增加，这种效果更加明显。尽管某些肌肉激活量适度降低，但基于弹簧的髋关节屈曲和外展辅助在某些步行速度下增加了代谢率。两种膝关节伸展辅助模式都在一定程度上降低了代谢率，尽管在站立阶段驱动几乎贡献了整个净膝关节伸展力矩。基于电机的髋关节外展辅助比基于弹簧的辅助降低代谢率的幅度更大，尽管这种降低相对较小。我们的研究还表明，基于最小肌肉激活量的辅助策略可能会导致代谢率的次优降低。未来的工作应该通过实验验证辅助力矩的效果，并相应地完善建模假设。我们的计算工作流程可在网上免费获取。
