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首页> 外文期刊>Journal of applied physiology >Robust passive dynamics of the musculoskeletal system compensate for unexpected surface changes during human hopping.
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Robust passive dynamics of the musculoskeletal system compensate for unexpected surface changes during human hopping.

机译：健壮的骨骼肌肉系统被动动力学可以补偿人体跳跃过程中意外的表面变化。

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When human hoppers are surprised by a change in surface stiffness, they adapt almost instantly by changing leg stiffness, implying that neural feedback is not necessary. The goal of this simulation study was first to investigate whether leg stiffness can change without neural control adjustment when landing on an unexpected hard or unexpected compliant (soft) surface, and second to determine what underlying mechanisms are responsible for this change in leg stiffness. The muscle stimulation pattern of a forward dynamic musculoskeletal model was optimized to make the model match experimental hopping kinematics on hard and soft surfaces. Next, only surface stiffness was changed to determine how the mechanical interaction of the musculoskeletal model with the unexpected surface affected leg stiffness. It was found that leg stiffness adapted passively to both unexpected surfaces. On the unexpected hard surface, leg stiffness was lower than on the soft surface, resulting in close-to-normal center of mass displacement. This reduction in leg stiffness was a result of reduced joint stiffness caused by lower effective muscle stiffness. Faster flexion of the joints due to the interaction with the hard surface led to larger changes in muscle length, while the prescribed increase in active state and resulting muscle force remained nearly constant in time. Opposite effects were found on the unexpected soft surface, demonstrating the bidirectional stabilizing properties of passive dynamics. These passive adaptations to unexpected surfaces may be critical when negotiating disturbances during locomotion across variable terrain.
机译：当人料斗对表面刚度的变化感到惊讶时，它们几乎可以通过改变腿的刚度来立即适应，这意味着不需要神经反馈。这项模拟研究的目的是首先调查当着陆在意外的坚硬或意外的顺应性（软）表面上时，如果没有神经控制调整，腿部僵硬度是否可以改变，其次是确定导致这种腿部僵硬度变化的根本机制。优化了前向动态肌肉骨骼模型的肌肉刺激模式，以使该模型与在硬和软表面上的实验跳跃运动学匹配。接下来，仅更改表面刚度以确定肌肉骨骼模型与意外表面的机械相互作用如何影响腿部刚度。发现腿部刚度被动地适应了两个意外表面。在出乎意料的坚硬表面上，腿部刚度低于柔软表面，导致质心位移接近法线中心。腿部僵硬的减少是由于较低的有效肌肉僵硬导致的关节僵硬减少的结果。由于与硬质表面的相互作用，关节的更快弯曲导致肌肉长度的较大变化，而规定的活动状态增加和所产生的肌肉力量在时间上几乎保持恒定。在意外的软表面上发现了相反的效果，表明了被动动力学的双向稳定特性。在跨可变地形的移动过程中协商干扰时，这些对意外表面的被动适应可能至关重要。

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