BACKGROUND The above-knee amputation of a lower limb is a severe impairment that affects significantly the ability to walk; considering this, a complex adaptation strategy at the neuromuscular level is needed in order to be able to move safely with a prosthetic knee. In literature, it has been demonstrated that muscle activity during walking can be described via the activation of a small set of muscle synergies. The analysis of the composition and the time activation profiles of such synergies have been found to be a valid tool for the description of the motor control schemes in pathological subjects. METHODS In this study, we used muscle synergy analysis techniques to characterize the differences in the modular motor control schemes between a population of 14 people with trans-femoral amputation and 12 healthy subjects walking at two different (slow and normal self-selected) speeds. Muscle synergies were extracted from a 12 lower-limb muscles sEMG recording via non-negative matrix factorization. Equivalence of the synergy vectors was quantified by a cross-validation procedure, while differences in terms of time activation coefficients were evaluated through the analysis of the activity in the different gait sub-phases. RESULTS Four synergies were able to reconstruct the muscle activity in all subjects. The spatial component of the synergy vectors did not change in all the analysed populations, while differences were present in the activity during the sound limb's stance phase. Main features of people with trans-femoral amputation's muscle synergy recruitment are a prolonged activation of the module composed of calf muscles and an additional activity of the hamstrings' module before and after the prosthetic heel strike. CONCLUSIONS Synergy-based results highlight how, although the complexity and the spatial organization of motor control schemes are the same found in healthy subjects, substantial differences are present in the synergies' recruitment of people with trans femoral amputation. In particular, the most critical task during the gait cycle is the weight transfer from the sound limb to the prosthetic one. Future studies will integrate these results with the dynamics of movement, aiming to a complete neuro-mechanical characterization of people with trans-femoral amputation's walking strategies that can be used to improve the rehabilitation therapies.

中文翻译：

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跨股截肢患者步态的声音肢体模块化运动控制。

背景技术下肢的膝盖以上截肢是一种严重的损伤，会严重影响步行能力。考虑到这一点，需要一种在神经肌肉水平上的复杂适应策略，以便能够通过假肢安全地运动。在文献中，已经证明步行期间的肌肉活动可以通过激活一小部分肌肉协同作用来描述。已经发现，这种协同作用的组成和时间激活曲线的分析是用于描述病理学对象中的运动控制方案的有效工具。方法在这项研究中，我们使用了肌肉协同分析技术来表征14名经股骨截肢的人与12名健康受试者以两种不同（缓慢和正常的自我选择）速度行走之间的模块化运动控制方案之间的差异。通过非负矩阵分解从12条下肢肌肉sEMG记录中提取肌肉协同作用。通过交叉验证程序对协同矢量的等效性进行定量，同时通过分析不同步态亚相中的活性来评估时间激​​活系数方面的差异。结果四种协同作用能够重建所有受试者的肌肉活动。在所有分析的群体中，协同矢量的空间成分均未改变，而在肢体站立阶段的活动中存在差异。经股截肢术的肌肉协同增招患者的主要特征是，由小腿肌肉组成的模块的激活时间延长，以及在假肢脚跟打击前后腿筋模块的额外活动。结论基于协同作用的结果强调了尽管运动控制方案的复杂性和空间组织在健康受试者中是相同的，但在协同经股截肢患者的协同招募中却存在实质性差异。特别是，步态周期中最关键的任务是将重量从健全肢体转移到假肢。未来的研究将把这些结果与运动的动力学结合起来，