Ritzmann Ramona, Lee Kyungsoo, Krause Anne, Gollhofer Albert, Freyler Kathrin
Department of Sport and Sport Science, University of Freiburg, Freiburg, Germany.
Institute of Training and Computer Science, German Sport University Cologne, Cologne, Germany.
Front Integr Neurosci. 2018 Dec 19;12:62. doi: 10.3389/fnint.2018.00062. eCollection 2018.
Anticipation determines the timing and efficiency of human motor performance. This study aimed to evaluate the effect of stimulus anticipation on proactive (prior to the event) and reactive (after the event) postural adjustments in response to perturbations. Postural set was manipulated by providing either (i) predictable, (ii) unpredictable, or (iii) cheated perturbations which require balance corrections to maintain postural stability. In 29 subjects, a protocol of anterior and posterior perturbations was applied for the conditions (i-iii). Center of pressure (COP) displacement, ankle, knee, and hip joint kinematics and electromyographic activity (EMG) of the soleus (SOL) and tibialis anterior (TA) muscles were recorded prior (PRE) and after posterior perturbations. SOL H-reflexes at the peak of the short-, medium- ,and long-latency responses (SLR, MLR, LLR) were assessed. For conditions (i to iii) EMG activity and COP differed prior to perturbation onset ( < 0.05). After perturbation, results demonstrated a progressively increased H-reflex amplitude in the MLR and LLR ( < 0.05), delayed muscle activities ( < 0.05), and shifted activation patterns, with muscles of the proximal segment being more involved in the compensatory postural response ( < 0.05). COP displacements and ankle, knee, and hip joint deflections progressively increased ( < 0.05). Neuromechanical coupling showed positive correlations for the anticipation-induced changes in EMG activity and H-reflex amplitude with that of COP displacement ( < 0.05). In conclusion, proactive and reactive postural responses indicated setting dependent modulations of segmental and phasic muscle activation. A shift to proximal muscle groups and facilitated late reflex responses compensating for cheated or unpredicted perturbations was found to recover a safe body equilibrium. In consideration of the phase-specific adaptation and its interrelationship to the kinematics, it suggested that changes in stimulus prediction challenged the central nervous system to appropriately counteract the higher postural challenges. The outcomes of this experiment are of functional relevance for experimental and training settings involving perturbation stimuli. These findings provide fundamental information of the mechanisms underlying postural adjustments in response to external perturbations.
预期决定了人类运动表现的时机和效率。本研究旨在评估刺激预期对响应扰动时的主动（事件发生前）和反应性（事件发生后）姿势调整的影响。通过提供以下三种情况来操纵姿势设定：（i）可预测的、（ii）不可预测的或（iii）欺骗性扰动，这些扰动需要进行平衡校正以维持姿势稳定性。对29名受试者，针对上述三种情况施加前后向扰动方案。记录后向扰动之前（PRE）和之后的压力中心（COP）位移、踝关节、膝关节和髋关节的运动学以及比目鱼肌（SOL）和胫骨前肌（TA）的肌电图活动（EMG）。评估短潜伏期、中潜伏期和长潜伏期反应（SLR、MLR、LLR）峰值时的SOL H反射。对于上述三种情况，扰动开始前的EMG活动和COP存在差异（P<0.05）。扰动后，结果显示MLR和LLR中的H反射幅度逐渐增加（P<0.05），肌肉活动延迟（P<0.05），且激活模式发生改变，近端节段的肌肉更多地参与到代偿性姿势反应中（P<0.05）。COP位移以及踝关节、膝关节和髋关节的偏移逐渐增加（P<0.05）。神经机械耦合显示，预期引起的EMG活动和H反射幅度变化与COP位移变化呈正相关（P<0.05）。总之，主动和反应性姿势反应表明了节段性和阶段性肌肉激活的设定依赖性调制。发现向近端肌肉群的转变以及促进晚期反射反应以补偿欺骗性或不可预测的扰动，有助于恢复安全的身体平衡。考虑到阶段特异性适应及其与运动学的相互关系，提示刺激预测的变化挑战了中枢神经系统以适当应对更高的姿势挑战。本实验的结果对于涉及扰动刺激的实验和训练设置具有功能相关性。这些发现提供了响应外部扰动时姿势调整潜在机制的基本信息。
