Hill muscle model errors during movement are greatest within the physiologically relevant range of motor unit firing rates
Hill muscle model errors during movement are greatest within the physiologically relevant range of motor unit firing rates
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DOI：
10.1016/s0021-9290(02)00332-9
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发表时间：
2003-02-01
影响因子：
2.4
通讯作者：
Sandercock, TG
中科院分区：
文献类型：
--
作者：
Perreault, EJ;Heckman, CJ;Sandercock, TG
这项研究评估了 Hill 型肌肉模型在运动过程中的准确性。山型模型在生物力学模拟中无处不在。它们之所以有吸引力，是因为它们的计算简单且与常用测量的实验变量密切相关，但令人惊讶的是，在功能相关条件下，这些模型的实验验证很少。我们的假设是，运动过程中的模型误差在与正常运动条件最相关的低运动单位放电率下最大。这一假设在通过生理速率的电刺激或通过交叉伸展反射（CXR）激活的猫比目鱼肌中进行了评估，从而获得了运动单位募集和速率调节的正常模式。这些激活范例在与运动长度变化大致匹配的连续运动期间应用。使用常见的希尔模型对所得肌肉力进行建模，该模型结合了独立激活、强直长度张力和强直力-速度特性。对于大约 10-20 Hz 之间的刺激率，该模型的误差最大。对于通过 CXR 激活的肌肉来说，误差尤其大，大多数运动单位似乎都在此范围内放电。对于大的肌肉偏移，例如在正常运动期间看到的那些，自然激活的肌肉的误差通常超过 50%，支持我们的假设并表明 Hill 模型不适合这些条件。随后的分析表明，模型错误是由于常见的希尔模型无法解释肌肉激活和力-速度特性之间的耦合，这种耦合在与正常激活相关的低运动单位放电率下最为普遍。 (C) 2002 Elsevier Science Ltd. 保留所有权利。
This study evaluated the accuracy of Hill-type muscle models during movement. Hill-type models are ubiquitous in biomechanical simulations. They are attractive because of their computational simplicity and close relation to commonly measured experimental variables, but there have been surprisingly few experimental validations of these models during functionally relevant conditions. Our hypothesis was that model errors during movement are largest at the low motor unit firing rates most relevant to normal movement conditions. This hypothesis was evaluated in the cat soleus muscle activated either by electrical stimulation at physiological rates or via the crossed-extension reflex (CXR) thereby obtaining normal patterns of motor unit recruitment and rate modulation. These activation paradigms were applied during continuous movements approximately matched to locomotor length changes. The resulting muscle force was modeled using a common Hill model incorporating independent activation, tetanic length tension and tetanic force-velocity properties. Errors for this model were greatest for stimulation rates between approximately 10-20 Hz. Errors were especially large for muscles activated via the CXR, where most motor units appear to fire within this range. For large muscle excursions, such as those seen during normal locomotion, the errors for naturally activated muscle typically exceeded 50%, supporting our hypothesis and indicating that the Hill model is not appropriate for these conditions. Subsequent analysis suggested that model errors were due to the common Hill model's inability to account for the coupling between muscle activation and force-velocity properties that is most prevalent at the low motor unit firing rates relevant to normal activation. (C) 2002 Elsevier Science Ltd. All rights reserved.