Ankle-foot-orthoses (AFOs) are commonly prescribed to treat foot drop and enhance walking in fall-prone individuals (e.g. stroke). AFOs improve static balance but AFO-users are still at high fall risk. To our knowledge, no one has studied the biomechanical effect of AFO-use on the compensatory stepping response required to avoid falling during dynamic conditions such as trip, the leading cause of falls. The objective of this study is to evaluate the impact of a semi-rigid thermoplastic AFO on the compensatory stepping response in young healthy individuals following trip-like treadmill perturbations. We found that the AFO on the stepping leg (AFO-step) decreased trunk stability (increased trunk angle and angular velocity), shortened the compensatory step length, and reduced dynamic stability (smaller COM-BOS). AFO on the support leg (AFO-support) was only marginally different from the No-AFO condition. Detrimental changes in compensatory stepping response (e.g. decreased trunk stability) were linearly correlated to diminished propulsive impulse of the step. In summary, AFO-use on the stepping leg is associated with impaired compensatory stepping response (e.g. reduced trunk stability) and decreased propulsive impulse in young adults. It is important to note that AFO-use enhances static stability and decreases the probability of a trip/stumble occurring indicating they are important for fall prevention. Still, our results suggest that AFO-use may impair the compensatory stepping response after a trip/stumble has occurred and may suggest that preserving plantarflexion function may support the compensatory stepping response. Further study of these devices and their impact on compensatory stepping response in fall-prone individuals is warranted.

踝足矫形器 (AFO) 通常用于治疗足下垂和增强易跌倒个体（例如中风）的行走能力。AFO 改善了静态平衡，但 AFO 使用者仍然处于高跌倒风险中。据我们所知，没有人研究过使用 AFO 对避免在动态条件下跌倒所需的补偿性步进响应的生物力学影响，例如绊倒，跌倒的主要原因。本研究的目的是评估半刚性热塑性 AFO 对年轻健康个体在类似跑步机扰动后的代偿性步进反应的影响。我们发现踏步腿上的 AFO（AFO-step）降低了躯干稳定性（增加了躯干角度和角速度），缩短了代偿步长，并降低了动态稳定性（较小的 COM-BOS）。支撑腿上的 AFO（AFO-support）与无 AFO 条件仅略有不同。代偿性踏步反应的有害变化（例如躯干稳定性下降）与踏步推进脉冲的减少呈线性相关。总之，在踏步腿上使用 AFO 与代偿性踏步反应受损（例如躯干稳定性降低）和年轻成人的推进冲动降低有关。需要注意的是，使用 AFO 可增强静态稳定性并降低发生绊倒/绊倒的可能性，这表明它们对于预防跌倒很重要。尽管如此，我们的结果表明，使用 AFO 可能会在发生绊倒/绊倒后损害代偿性步进反应，并可能表明保留跖屈功能可能支持代偿性步进反应。