MODIFICATION OF POSTURAL RESPONSES AND STEP INITIATION - EVIDENCE FOR GOAL-DIRECTED POSTURAL INTERACTIONS
MODIFICATION OF POSTURAL RESPONSES AND STEP INITIATION - EVIDENCE FOR GOAL-DIRECTED POSTURAL INTERACTIONS
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DOI：
10.1152/jn.1994.72.6.2892
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发表时间：
1994-12-01
影响因子：
2.5
通讯作者：
MALOUIN, F
中科院分区：
文献类型：
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作者：
BURLEIGH, AL;HORAK, FB;MALOUIN, F
1.在这项研究中，预期的姿势调整步骤启动和自动姿势反应外部扰动之间的相互作用进行了研究，有科目启动一个自愿向前的一步，而由一个向后的表面平移，这导致身体向前摇摆扰动。步伐起始的姿势调整作用于向前移动身体质心（COM），而自动姿势响应作用于向后移动COM以恢复站立平衡。由于姿势行为是相反的，我们问是否存在一个时间层次，其中执行自动姿势反应以恢复平衡，然后进行刻板的姿势调整，以启动步骤，或者这两个姿势行为之间的相互作用是否更动态。记录了10名受试者在三种情况下的下肢肌电图（EMG）、地面反作用力和运动学：为了量化受试者在开始迈步时的预期姿势调整，受试者一感觉到本体感受提示就向前迈步;为了量化受试者对扰动的自动姿势反应，受试者在双脚下向后平移时保持站立平衡;为了量化随意迈步的姿势调整和对扰动的自动反应之间的相互作用，受试者被暴露于向后的表面平移，并被指示在他们感觉到平台开始移动时立即向前迈步。步启动的预期调整包括胫骨肌激活[站立肢体= 163 +/-28（SE）ms;摆动肢体= 173 +/-33 ms]和比目鱼肌抑制，导致足部压力中心（COP）向后和侧向移动到摆动肢体，以推动COM在站立肢体上向前。随后，摆动肢体腓肠肌的激活导致脚跟离地。相反，在向后表面平移期间用于维持站立平衡的自动姿势调整包括比目鱼肌和腓肠肌的激活（分别为104 +/-23 ms和115 +/-14 ms），导致COP的对称向前位移，将COM移回其相对于足部的原始位置。当一个向前的一步开始响应的翻译，自动姿势反应的幅度减少，双边在比目鱼肌和站立肢体腓肠肌。当存在时，姿势反应发生在相同的潜伏期时，目标是启动一个步骤，当目标是保持站立。摆动肢体腓肠肌的幅度受影响较小，表明姿势反应的减少是特定于肢体在即将到来的步骤中的作用。即使胫骨肌的起始步启动时是不变的，当一个步骤开始响应的翻译，而不是响应于本体感受的线索，持续时间的姿势调整步启动缩短和肌肉激活模式进行了修改相对于被动向前位移的身体COM。与胫骨肌的固定起始点不同，COP的侧向偏移开始得更早，即当响应于平移而启动步进时（150 +/-27 ms）而不是本体感受线索（204 +/-40 ms），这表明在扰动条件下需要更快地减轻摆动肢体的重量，因为COM在扰动条件下向前移动得更快，条件6.这些结果表明，平台平移的自动姿势反应和步骤启动的姿势调整都被修改，身体位置的变化和预期的运动目标的变化。这表明，下降的中央电机程序的步骤启动和上升的信息与平台的翻译互动，即使自愿的反应时间为步骤启动是相当长的起始潜伏期的自动姿势反应。这些结果与姿势组织的时间层次不一致。相反，有一个动态的相互作用之间的自动姿势响应外部扰动和预期的姿势调整目标导向的运动。
1. In this study, the interaction between anticipatory postural adjustments for step initiation and automatic postural responses to an external perturbation were investigated by having subjects initiate a voluntary forward step while perturbed by a backward surface translation, which caused forward sway of the body. The postural adjustments for step initiation act to move the body center of mass (COM) forward, whereas the automatic postural responses act to move the COM backward to restore stance equilibrium. Because the postural behaviors are in opposition, we asked whether a temporal hierarchy exists in which automatic postural responses are executed to restore equilibrium and followed by stereotypic postural adjustments for step initiation, or whether the interaction between these two postural behaviors is more dynamic.2. Lower extremity electromyographs (EMGs), ground reaction forces, and kinematics were recorded from 10 subjects during three conditions: to quantify the anticipatory postural adjustments for step initiation, subjects stepped forward as soon as they felt a proprioceptive cue; to quantify the automatic postural responses to perturbation, subjects maintained stance equilibrium in response to a backward surface translation under both feet; and to quantify the interaction between the postural adjustments for the voluntary step and the automatic responses to the perturbation, subjects were exposed to a backward surface translation and instructed to step forward as soon as they felt the platform begin to move.3. The anticipatory adjustments for step initiation included tibialis activation [stance limb = 163 +/- 28 (SE) ms; swing limb = 173 +/- 33 ms] and soleus inhibition resulting in center of foot pressure (COP) moving backward and lateral toward the swing limb to propel the COM forward over the stance limb. Subsequently, activation of the swing limb gastrocnemius resulted in heel-off. In contrast, the automatic postural adjustments for maintenance of stance equilibrium during a backward surface translation included activation of soleus and gastrocnemius (104 +/- 23 ms and 115 +/- 14 ms, respectively) resulting in a symmetrical forward displacement of the COP that moved the COM back to its original position with respect to the feet.4. When a forward step was initiated in response to the translation, the automatic postural responses were reduced in amplitude bilaterally in soleus and in the stance limb gastrocnemius. When present the postural response occurred at the same latency when the goal was to initiate a step as when the goal was to maintain standing. The amplitude of the swing limb gastrocnemius was less affected, suggesting that reduction of the postural response was specific to the role of the limbs in the impending step.5. Even though the onset of tibialis for step initiation was unchanged when a step was initiated in response to the translation rather than in response to a proprioceptive cue, the duration of the postural adjustments for step initiation were shortened and the muscle-activation patterns were modified with respect to the passive forward displacement of the body COM. In contrast to the fixed onset of the tibialis, the lateral excursion of the COP began earlier when the step was initiated in response to the translation (150 +/- 27 ms) rather than the proprioceptive cue (204 +/- 40 ms), suggesting that a more rapid unweighting of the swing limb was required in the perturbed condition because the COM was displaced further forward and faster in the perturbed condition.6. These results demonstrate that both the automatic postural responses to platform translation and the postural adjustments for step initiation were modified, both by changes in body position and by changes in the intended movement goal. This suggests that the descending central motor program for step initiation and the ascending information associated with the platform translation interacted even though the voluntary reaction time for step initiation was considerably longer than the onset latency of the automatic postural response. These results are not consistent with a temporal hierarchy for postural organization. Rather, there is a dynamic interaction between the automatic postural responses to an external perturbation and anticipatory postural adjustments for goal-directed movements.