School of Human Movement and Nutrition Sciences, University of Queensland, St Lucia, Queensland, Australia.
Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK.
J R Soc Interface. 2021 Mar;18(176):20210061. doi: 10.1098/rsif.2021.0061. Epub 2021 Mar 10.
Unanticipated variations in terrain can destabilize the body. The foot is the primary interface with the ground and we know that cutaneous reflexes provide important sensory feedback. However, little is known about the contribution of stretch reflexes from the muscles within the foot to upright stability. We used intramuscular electromyography measurements of the foot muscles flexor digitorum brevis (FDB) and abductor hallucis (AH) to show for the first time how their short-latency stretch reflex response (SLR) may play an important role in responding to stepping perturbations. The SLR of FDB and AH was highest for downwards steps and lowest for upwards steps, with the response amplitude for level and compliant steps in between. When the type of terrain was unknown or unexpected to the participant, the SLR of AH and the ankle muscle soleus tended to decrease. We found significant relationships between the contact kinematics and forces of the leg and the SLR, but a person's expectation still had significant effects even after accounting for these relationships. Motor control models of short-latency body stabilization should not only include local muscle dynamics, but also predictions of terrain based on higher level information such as from vision or memory.
地形的意外变化会使身体失去平衡。脚是与地面的主要接触点，我们知道皮肤反射为重要的感觉反馈提供了支持。然而，对于足部肌肉伸展反射对直立稳定性的贡献，我们知之甚少。我们使用足底内肌的肌内电图测量技术，研究了足趾短屈肌（FDB）和外展肌（AH）的短潜伏期伸展反射反应（SLR），首次展示了它们如何在应对跨步干扰中发挥重要作用。FDB 和 AH 的 SLR 在向下跨步时最高，向上跨步时最低，水平和顺应性跨步时的响应幅度介于两者之间。当参与者对地形的类型未知或出乎意料时，AH 和小腿肌肉比目鱼肌的 SLR 往往会降低。我们发现腿部的接触运动学和力与 SLR 之间存在显著关系，但即使考虑到这些关系，人的预期仍然有显著的影响。短潜伏期身体稳定的运动控制模型不仅应包括局部肌肉动力学，还应包括基于高级信息（如视觉或记忆）的地形预测。
