Laboratory of Motor Behavior and Adapted Physical Activity, School of Physical Education and Sport Science, Aristotle University of Thessaloniki, Greece.
Laboratory of Neuromechanics, School of Physical Education and Sport Science at Serres, Aristotle University of Thessaloniki, Greece.
Neurosci Lett. 2021 Aug 10;759:135995. doi: 10.1016/j.neulet.2021.135995. Epub 2021 May 28.
To investigate the link between the triceps surae and the intrinsic muscles of the foot, often underestimated in posture maintenance, we asked how Achilles' tendon vibration modulates the EMG activity of the soleus and flexor digitorum brevis (FDB) muscles during different postural tasks: sitting, standing and forward leaning. Young healthy participants (n = 19, age = 24 ± 7.4 years) stood for 60 s in three visually controlled postures, while vibration (1.5-1.8 mm, 80 Hz) was bilaterally applied over the Achilles' tendon during the middle 20 s. Center of Pressure (CoP) and EMG activity of the soleus and FDB muscle were summarized in 5 s epochs and compared across time (before, during and after vibration) and postural tasks. Achilles' tendon vibration shifted the CoP position forward in sitting and backward in standing and leaning and increased the root mean square of the CoP velocity to a greater extent in standing and leaning compared to sitting. Soleus and FDB EMG amplitude also increased in response to vibration. These responses were posture dependent, being greater in standing (soleus: 57 %, FDB: 67 % relative to pre-vibration) compared to sitting (soleus: 36 %, FDB: 27 % relative to pre-vibration) and leaning (soleus: 26 %, FDB: 8% relative to pre-vibration). After vibration offset, both soleus and FDB showed sustained activation across all three postures. Results highlight the presence of Ia afferent projections from the soleus to the α motor neurons of the FDB muscle triggered by Achilles' tendon vibration. This link is posture dependent serving a functional role in standing and forward leaning in the presence of externally applied perturbations.
为了研究在姿势维持中经常被低估的小腿三头肌和足部内在肌肉之间的联系，我们研究了在不同姿势任务（坐、站和前倾）下，跟腱振动如何调节比目鱼肌和趾短屈肌（FDB）的肌电图（EMG）活动。年轻健康的参与者（n = 19，年龄 = 24 ± 7.4 岁）在三种视觉控制的姿势下站立 60 秒，同时在中间 20 秒双侧应用 1.5-1.8 毫米、80 赫兹的跟腱振动。在整个振动过程中，比较了中心压力（CoP）和比目鱼肌和 FDB 肌肉的 EMG 活动，并在时间（振动前、振动中和振动后）和姿势任务之间进行了比较。跟腱振动使 CoP 在坐姿中向前移动，在站姿和前倾中向后移动，并使 CoP 速度的均方根在站姿和前倾中比坐姿中增加得更大。比目鱼肌和 FDB 的 EMG 幅度也随振动而增加。这些反应与姿势有关，在站姿（比目鱼肌：57%，FDB：67%相对于振动前）比坐姿（比目鱼肌：36%，FDB：27%相对于振动前）和前倾（比目鱼肌：26%，FDB：8%相对于振动前）更大。振动结束后，比目鱼肌和 FDB 在所有三种姿势下都保持持续激活。结果表明，跟腱振动触发了来自比目鱼肌的 Ia 传入投射到 FDB 肌肉的α运动神经元。这种联系与姿势有关，在存在外部施加的扰动时，它在站立和前倾中起作用。
