Co-Contraction and Passive Forces Facilitate Load Compensation of Aimed Limb Movements
Co-Contraction and Passive Forces Facilitate Load Compensation of Aimed Limb Movements
复制标题
共同收缩和被动力促进目标肢体运动的负载补偿
DOI：
10.1523/jneurosci.0161-06.2006
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
V. Dürr
中科院分区：
文献类型：
--
作者：
J. Zakotnik;T. Matheson;V. Dürr
脊椎动物和节肢动物都能够在有针对性的肢体运动过程中进行负载补偿，例如伸展和梳理。我们测量的运动学和活动的个别运动神经元在加载和卸载的腿部运动的昆虫。为了评估主动和被动肌肉骨骼特性在瞄准和负载补偿中的作用，我们使用了股骨-胫骨关节的神经力学模型，该模型将测量的伸肌和屈肌运动神经元尖峰转换为关节运动学。该模型包括三个步骤：第一，确定等距力的时间过程的激活动力学模块;第二，确定关节扭矩的一对拮抗肌模型;以及第三，计算肢体运动的前向动力学模拟。肌肉建模为五种变体，不同之处在于收缩元件、平行被动弹性元件和被动关节阻尼的力-长度-速度特征的存在或不存在。每个变体都经过优化，以产生对测量行为的最佳模拟。被动肌肉力量和粘性关节阻尼是足够的和必要的，以模拟所观察到的运动。主动收缩元件的弹性或阻尼特性不能代替被动元件。被动弹性力的大小与肌肉收缩引起的主动力相似，产生大量的关节僵硬。拮抗肌肉共收缩，虽然没有运动神经元共激活，因为肌肉激活的动力学缓慢。我们量化了共同收缩如何简化负荷补偿，证明了运动神经元输入的小变化会导致关节扭矩的大变化。
Vertebrates and arthropods are both capable of load compensation during aimed limb movements, such as reaching and grooming. We measured the kinematics and activity of individual motoneurons in loaded and unloaded leg movements in an insect. To evaluate the role of active and passive musculoskeletal properties in aiming and load compensation, we used a neuromechanical model of the femur–tibia joint that transformed measured extensor and flexor motoneuron spikes into joint kinematics. The model comprises three steps: first, an activation dynamics module that determines the time course of isometric force; second, a pair of antagonistic muscle models that determine the joint torque; and third, a forward dynamics simulation that calculates the movement of the limb. The muscles were modeled in five variants, differing in the presence or absence of force–length–velocity characteristics of the contractile element, a parallel passive elastic element, and passive joint damping. Each variant was optimized to yield the best simulation of measured behavior. Passive muscle force and viscous joint damping were sufficient and necessary to simulate the observed movements. Elastic or damping properties of the active contractile element could not replace passive elements. Passive elastic forces were similar in magnitude to active forces caused by muscle contraction, generating substantial joint stiffness. Antagonistic muscles co-contract, although there was no motoneuronal coactivation, because of slow dynamics of muscle activation. We quantified how co-contraction simplified load compensation by demonstrating that a small variation of the motoneuronal input caused a large change in joint torque.
影响因子：
2.4
作者：
F. Zajac
通讯作者：
F. Zajac
影响因子：
--
作者：
F. Zajac
通讯作者：
F. Zajac
影响因子：
2.5
作者：
Brezina, V;Orekhova, IV;Weiss, KR
通讯作者：
Weiss, KR