Human postural sway results from frequent, ballistic bias impulses by soleus and gastrocnemius
Human postural sway results from frequent, ballistic bias impulses by soleus and gastrocnemius
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DOI：
10.1113/jphysiol.2004.076307
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发表时间：
2005-04-01
影响因子：
5.5
通讯作者：
Lakie, M
中科院分区：
文献类型：
--
作者：
Loram, ID;Maganaris, CN;Lakie, M
近一个世纪以来，人们普遍认为姿势肌肉以类似弹簧的方式运作，肌肉长度表示关节角度（机械反射机制）。在这里，我们采用超声图像的自动分析来解决站立受试者小腿肌肉（比目鱼肌和腓肠肌）长度小至晚上10点的变化。在此之前，我们使用了一个真正的倒立摆的平衡来预测人类的站立状态。在这里，我们在10个安静地站着的实验对象身上测试并证实了这些预测。我们的研究表明，小腿肌肉平均每秒主动调整2.6次，身体重心（CoM）单向摆动时主动调整2.8次。这些交替的、小的（30-300 μ m）运动提供了CoM运动的脉冲、弹道调节。这些调整的时间和模式与有关CoM运动的所有信息的多感官整合、模式识别、使用内部模型的预测和计划一致，而与仅通过局部反射控制不一致。因为系统是不稳定的，稳定中的误差提供了一个扰动，它发展成一种摇摆，必须作出反应和纠正。矢状面摆动是由这种对小腿肌肉活动的冲动控制造成的，而不是由内部因素（如心脏、呼吸）造成的。这一过程与机械反射范式截然不同。我们认为站立是一种熟练的、反复试验的活动，随着经验的增加而提高，并且是自动化的（可能是小脑的）。这些结果补充并扩展了我们最近的论证，即矛盾的肌肉运动是人类站立的常态。
It has been widely assumed for nearly a century, that postural muscles operate in a spring-like manner and that muscle length signals joint angle (the mechano-reflex mechanism). Here we employ automated analysis of ultrasound images to resolve calf muscle (soleus and gastrocnemius) length changes as small as 10 pm in standing subjects. Previously, we have used balancing of a real inverted pendulum to make predictions about human standing. Here we test and confirm these predictions on 10 subjects standing quietly. We show that on average the calf muscles are actively adjusted 2.6 times per second and 2.8 times per unidirectional sway of the body centre of mass (CoM). These alternating, small (30-300 mu m) movements provide impulsive, ballistic regulation of CoM movement. The timing and pattern of these adjustments are consistent with multisensory integration of all information regarding motion of the CoM, pattern recognition, prediction and planning using internal models and are not consistent with control solely by local reflexes. Because the system is unstable, errors in stabilization provide a perturbation which grows into a sway which has to be reacted to and corrected. Sagittal sway results from this impulsive control of calf muscle activity rather than internal sources (e.g. the heart, breathing). This process is quite unlike the mechano-reflex paradigm. We suggest that standing is a skilled, trial and error activity that improves with experience and is automated (possibly by the cerebellum). These results complement and extend our recent demonstration that paradoxical muscle movements are the norm in human standing.