Chronic stroke survivors often suffer from gait impairment resistant to intervention. Recent rehabilitation strategies based on gait training with powered exoskeletons appear promising, but whether chronic survivors may benefit from them remains controversial. We evaluated the potential of exoskeletal gait training in restoring normal motor outputs in chronic survivors (N = 10) by recording electromyographic signals (EMGs, 28 muscles both legs) as they adapted to exoskeletal perturbations, and examined whether any EMG alterations after adaptation were underpinned by closer-to-normal muscle synergies. A unilateral ankle-foot orthosis that produced dorsiflexor torque on the paretic leg during swing was tested. Over a single session, subjects walked overground without exoskeleton (FREE), then with the unpowered exoskeleton (OFF), and finally with the powered exoskeleton (ON). Muscle synergies were identified from EMGs using non-negative matrix factorization. During adaptation to OFF, some paretic-side synergies became more dissimilar to their nonparetic-side counterparts. During adaptation to ON, in half of the subjects some paretic-side synergies became closer to their nonparetic references relative to their similarity at FREE as these paretic-side synergies became sparser in muscle components. Across subjects, level of inter-side similarity increase correlated negatively with the degree of gait temporal asymmetry at FREE. Our results demonstrate the possibility that for some survivors, exoskeletal training may promote closer-to-normal muscle synergies. But to fully achieve this, the active force must trigger adaptive processes that offset any undesired synergy changes arising from adaptation to the device’s mechanical properties while also fostering the reemergence of the normal synergies.

中文翻译：

---

通过改变慢性中风幸存者的肌肉协同作用适应外骨骼的机械特性和主动力

慢性中风幸存者经常遭受步态障碍，难以干预。基于以动力性外骨骼进行步态训练的近期康复策略似乎很有希望，但是长期幸存者是否可以从中受益仍然存在争议。我们通过记录肌电信号（EMG，双腿28条肌肉）适应骨骼外摄动的情况，评估了骨骼肌步态训练在恢复慢性幸存者（N = 10）正常运动输出方面的潜力，并检查了适应后是否存在任何肌电图改变通过接近正常的肌肉协同作用。测试了单侧踝足矫形器，该矫形器在挥杆过程中对顶腿产生背屈扭矩。在一个会话中，受试者在没有外骨骼的情况下自由行走（免费），然后在没有动力的外骨骼情况下（OFF）行走，最后是动力外骨骼（ON）。使用非负矩阵分解从肌电图中确定了肌肉协同作用。在适应OFF的过程中，某些Paretic方面的协同作用变得与非Paretic方面的协同作用更加不同。在适应ON的过程中，一半受试者在自由时的相似性方面，一些paretic-side协同作用变得更接近其非paretic参照，因为这些parite-side协同作用在肌肉成分中变得稀疏。在受试者之间，相似度的增加水平与自由时步态时间不对称程度呈负相关。我们的结果表明，对于某些幸存者而言，骨骼外训练可能会促进更接近正常的肌肉协同作用。但是要完全实现这一点，