Abstract
Swing-phase dorsiflexion assistance with robotic ankle–foot orthosis could improve toe clearance and limb shortening such that compensatory movements are suppressed. However, facilitating voluntary effort under assistance remains a challenge. In our previous study, we examined assistance effects of swing-phase dorsiflexion with different delay times after toe-off on a dorsiflexion-restricted gait with a high-dorsiflexion assistive system. Results showed that later dorsiflexion assistance could lead to an increase in the tibialis anterior’s surface electromyography but could also deteriorate compensatory movement. Thus, we concluded that there is a suitable assistance timing to simultaneously achieve voluntary effort and optimal gait. In the present research, we derived a method to identify a suitable dorsiflexion assistance delay time via a multiple linear regression analysis on ankle data of stroke patients with a pathological gait with insufficient dorsiflexion. With the identification method, an experiment was conducted on six healthy participants with restricted dorsiflexion. Results showed that the identified assistance timing improved the amplitude of the tibialis anterior’s surface electromyography while also suppressing limb shortening during circumduction and hip hiking. Although a practical study of stroke survivors is required, observations from this research indicate the potential to successfully induce voluntary efforts with the identified dorsiflexion assistance timing.
Highlights
Stroke is presently one of the most prevalent cardiovascular diseases
The results show that longer assistance delay times had moderate to strong positive correlations with surface electromyography of the tibialis anterior, indicating that delayed assistance could increase the extent of voluntary dorsiflexion movement
SEMG amplitudes in AST1.5y conditions are all significantly higher than those in AST0 conditions. This suggests that voluntary ankle dorsiflexion movement was induced with dorsiflexion assistance delay time equal to or larger than y ms, which successfully identifies an optimal assistance timing
Summary
Stroke is presently one of the most prevalent cardiovascular diseases. According to the World Health Organization, it is estimated that 15 million people worldwide suffer a stroke annually, 10 million of whom survive with disabilities [1]. For a stroke hemiplegic patient, his or her ankle forces or movement controls may be too weak to perform sufficient dorsiflexion and drop foot could result [7] This toe-down posture decreases toe clearance and could lead to stumbling or toe dragging while walking [8]. To increase minimum toe clearance (MTC) in the swing phase, stroke survivors tend to perform compensatory movements such as circumduction and hip hiking [9,10]. Such compensatory movements during gait rehabilitation could affect optimal gait learning
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