Fadillioglu Cagla, Kanus Lisa, Möhler Felix, Ringhof Steffen, Hellmann Daniel, Stein Thorsten
BioMotion Center, Institute of Sports and Sports Science, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany.
Department of Prosthodontics, University of Würzburg, Würzburg, Germany.
Front Neurol. 2023 Jun 23;14:1140712. doi: 10.3389/fneur.2023.1140712. eCollection 2023.
Good balance is essential for human daily life as it may help to improve the quality of life and reduce the risk of falls and associated injuries. The influence of jaw clenching on balance control has been shown under static and dynamic conditions. Nevertheless, it has not yet been investigated whether the effects are mainly associated with the dual-task situation or are caused by jaw clenching itself. Therefore, this study investigated the effects of jaw clenching on dynamic reactive balance task performance prior to and after 1 week of jaw clenching training. It was hypothesized that jaw clenching has stabilizing effects resulting in a better dynamic reactive balance performance, and these effects are not related to dual-task benefits.
A total of 48 physically active and healthy adults (20 women and 28 men) were distributed into three groups, one habitual control group (HAB) and two jaw clenching groups (JAW and INT) that had to clench their jaws during the balance tasks at T1 and T2. One of those two groups, the INT group, additionally practiced the jaw clenching task for 1 week, making it familiar and implicit at T2. The HAB group did not receive any instruction regarding jaw clenching condition. Dynamic reactive balance was assessed using an oscillating platform perturbed in one of four directions in a randomized order. Kinematic and electromyographic (EMG) data were collected using a 3D motion capture system and a wireless EMG system, respectively. Dynamic reactive balance was operationalized by the damping ratio. Furthermore, the range of motion of the center of mass (CoM) in perturbation direction (RoM or RoM), as well as the velocity of CoM () in 3D, were analyzed. The mean activity of the muscles relevant to the perturbation direction was calculated to investigate reflex activities.
The results revealed that jaw clenching had no significant effects on dynamic reactive balance performance or CoM kinematics in any of these three groups, and the automation of jaw clenching in the INT group did not result in a significant change either. However, high learning effects, as revealed by the higher damping ratio values and lower at T2, were detected for the dynamic reactive balance task even without any deliberate balance training in the intervention phase. In the case of backward perturbation of the platform, the soleus activity in a short latency response phase increased for the JAW group, whereas it decreased for HAB and INT after the intervention. In the case of forward acceleration of the platform, JAW and INT showed a higher tibialis anterior muscle activity level in the medium latency response phase compared to HAB at T1.
Based on these findings, it can be suggested that jaw clenching may lead to some changes in reflex activities. However, the effects are limited to anterior-posterior perturbations of the platform. Nevertheless, high learning effects may have overall overweighed the effects related to jaw clenching. Further studies with balance tasks leading to less learning effects are needed to understand the altered adaptations to a dynamic reactive balance task related to simultaneous jaw clenching. Analysis of muscle coordination (e.g., muscle synergies), instead of individual muscles, as well as other experimental designs in which the information from other sources are reduced (e.g., closed eyes), may also help to reveal jaw clenching effects.
良好的平衡能力对人类日常生活至关重要，因为它有助于提高生活质量，降低跌倒及相关损伤的风险。在静态和动态条件下，已证实咬紧牙关对平衡控制有影响。然而，尚未研究这些影响主要是与双重任务情境相关，还是由咬紧牙关本身引起。因此，本研究调查了在进行1周的咬紧牙关训练前后，咬紧牙关对动态反应平衡任务表现的影响。研究假设为，咬紧牙关具有稳定作用，能带来更好的动态反应平衡表现，且这些影响与双重任务益处无关。
总共48名身体活跃的健康成年人（20名女性和28名男性）被分为三组，一组为习惯对照组（HAB），两组为咬紧牙关组（JAW和INT），这两组在T1和T2的平衡任务期间必须咬紧牙关。这两组中的一组，即INT组，额外进行了1周的咬紧牙关任务练习，使其在T2时变得熟悉且下意识。HAB组未收到任何关于咬紧牙关情况的指示。使用在四个方向之一随机扰动的振荡平台评估动态反应平衡。分别使用3D运动捕捉系统和无线肌电图（EMG）系统收集运动学和肌电图数据。动态反应平衡通过阻尼比来衡量。此外，还分析了质心（CoM）在扰动方向上的运动范围（RoM或RoM）以及3D中的CoM速度（）。计算与扰动方向相关的肌肉的平均活动，以研究反射活动。
结果显示，在这三组中，咬紧牙关对动态反应平衡表现或CoM运动学均无显著影响，INT组咬紧牙关的自动化也未导致显著变化。然而，即使在干预阶段没有进行任何刻意的平衡训练，动态反应平衡任务在T2时也呈现出较高的学习效果，表现为更高的阻尼比值和更低的。在平台向后扰动的情况下，JAW组在短潜伏期反应阶段比目鱼肌活动增加，而干预后HAB组和INT组则减少。在平台向前加速的情况下，与T1时的HAB组相比，JAW组和INT组在中潜伏期反应阶段胫骨前肌活动水平更高。
基于这些发现，可以认为咬紧牙关可能会导致反射活动发生一些变化。然而，这些影响仅限于平台的前后扰动。尽管如此，较高的学习效果可能总体上超过了与咬紧牙关相关的影响。需要进行更多导致学习效果较小的平衡任务研究，以了解与同时咬紧牙关相关的动态反应平衡任务的适应性变化。分析肌肉协调性（例如肌肉协同作用）而非单个肌肉，以及减少来自其他来源信息的其他实验设计（例如闭眼），也可能有助于揭示咬紧牙关的影响。
