Gradual mechanics-dependent adaptation of medial gastrocnemius activity during human walking.
Gradual mechanics-dependent adaptation of medial gastrocnemius activity during human walking.
复制标题
人类行走过程中腓肠肌内侧活动的逐渐力学依赖性适应。
DOI：
10.1152/jn.00251.2013
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发表时间：
2014
影响因子：
2.5
通讯作者：
Dean,JesseC
中科院分区：
文献类型：
--
作者：
Wellinghoff,MollyA;Bunchman,AlisonM;Dean,JesseC
在执行简单的弹跳任务时，人类会根据系统力学的变化来修改他们喜欢的运动周期和跖屈肌活动模式。随着时间的推移，首选的运动模式逐渐适应共振频率。本实验的目的是确定人类是否会经历类似的过程，即在行走时机械需求发生变化后逐渐适应其步幅周期和跖屈肌活动。参与者在跑步机上行走，同时我们测量步幅时间和跖屈肌活动（内侧腓肠肌和比目鱼肌）。根据先前已证明跟腱存储和返回机械能的时间，站立期间的跖屈肌活动分为存储阶段（30-65% 站立）和返回阶段（65-100% 站立）。参与者要么在恒定坡度（0%、1%、5%、9%）上行走，要么在可变坡度（0-1%）上行走，他们不知道坡度的变化。对于可变倾斜试验，参与者在单任务和双任务条件下行走，以改变认知负荷。步幅时间和跖屈肌活动随着坡度的增大而增加。在单任务步行过程中，倾斜度发生微小变化后，存储阶段腓肠肌内侧肌活动逐渐适应。然而，这种适应在双任务行走期间并不存在，这表明一定程度的认知参与。观察到的适应可能是使用传入反馈的结果，以优化站立阶段跖屈肌的收缩条件。这种适应可以有助于改善代谢经济，但在本体感觉受损的临床人群中可能受到限制。
While performing a simple bouncing task, humans modify their preferred movement period and pattern of plantarflexor activity in response to changes in system mechanics. Over time, the preferred movement pattern gradually adapts toward the resonant frequency. The purpose of the present experiments was to determine whether humans undergo a similar process of gradually adapting their stride period and plantarflexor activity after a change in mechanical demand while walking. Participants walked on a treadmill while we measured stride period and plantarflexor activity (medial gastrocnemius and soleus). Plantarflexor activity during stance was divided into a storage phase (30–65% stance) and a return phase (65–100% stance) based on when the Achilles tendon has previously been shown to store and return mechanical energy. Participants walked either on constant inclines (0%, 1%, 5%, 9%) or on a variable incline (0–1%) for which they were unaware of the incline changes. For variable-incline trials, participants walked under both single-task and dual-task conditions in order to vary the cognitive load. Both stride period and plantarflexor activity increased at steeper inclines. During single-task walking, small changes in incline were followed by gradual adaptation of storage-phase medial gastrocnemius activity. However, this adaptation was not present during dual-task walking, indicating some level of cognitive involvement. The observed adaptation may be the result of using afferent feedback in order to optimize the contractile conditions of the plantarflexors during the stance phase. Such adaptation could serve to improve metabolic economy but may be limited in clinical populations with disrupted proprioception.