Does a two-element muscle model offer advantages when estimating ankle plantar flexor forces during human cycling?
Does a two-element muscle model offer advantages when estimating ankle plantar flexor forces during human cycling?
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DOI：
10.1016/j.jbiomech.2017.12.018
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发表时间：
2018-02-08
影响因子：
2.4
通讯作者：
Wakeling JM
中科院分区：
文献类型：
--
作者：
Lai AKM;Arnold AS;Biewener AA;Dick TJM;Wakeling JM
使用高质量实验数据进行参数化的传统希尔型肌肉模型通常“太弱”，无法重现健康成年人在快速、高强度任务中产生的关节扭矩。这项研究调查了这些模型未能解释不同类型的运动单位是否导致了这种明显的弱点；如果是这样，肌肉驱动的模拟可能依赖于过高的肌肉兴奋来产生给定的力。我们进行了一系列正向模拟，再现了以 60-140 RPM 的五种踏频骑行时测得的脚踝力学情况。我们生成了“标称”模拟和“测试”模拟，其中抽象踝关节模型由具有单个收缩元件 (CE) 的 1 元件 Hill 型跖屈肌驱动，而“测试”模拟则由具有两个 CE 的 2 元件跖屈肌驱动，这两个 CE 考虑了较慢和较快运动单元的力生成特性。我们将施加到 2 元件跖屈肌的总激励在每次标称模拟激励的 60-105% 之间变化，并将分配给每个 CE 的量在总量的 0-100% 之间变化。在这个测试空间中，我们确定了每个节奏下的激励水平和分布，最好地再现了标称模拟中产生的跖屈肌力。我们的比较表明，2 元件模型需要比 1 元件模型少得多的总激励来产生类似的力，尤其是在较高的踏频下。例如，在 140 RPM 时，所需的激励减少了 23%。这些结果表明，二元模型（其中收缩特性被“调整”以代表较慢和较快的运动单位）可以增加表观强度，并可能提高具有不同机械需求的任务模拟的保真度。
Traditional Hill-type muscle models, parameterized using high-quality experimental data, are often “too weak” to reproduce the joint torques generated by healthy adults during rapid, high force tasks. This study investigated whether the failure of these models to account for different types of motor units contributes to this apparent weakness; if so, muscle-driven simulations may rely on excessively high muscle excitations to generate a given force. We ran a series of forward simulations that reproduced measured ankle mechanics during cycling at five cadences ranging from 60–140 RPM. We generated both “nominal” simulations, in which an abstract ankle model was actuated by a 1-element Hill-type plantar flexor with a single contractile element (CE), and “test” simulations, in which the same model was actuated by a 2-element plantar flexor with two CEs that accounted for the force-generating properties of slower and faster motor units. We varied the total excitation applied to the 2-element plantar flexor between 60–105% of the excitation from each nominal simulation, and we varied the amount distributed to each CE between 0–100% of the total. Within this test space, we identified the excitation level and distribution, at each cadence, that best reproduced the plantar flexor forces generated in the nominal simulations. Our comparisons revealed that the 2-element model required substantially less total excitation than the 1-element model to generate comparable forces, especially at higher cadences. For instance, at 140 RPM, the required excitation was reduced by 23%. These results suggest that a 2-element model, in which contractile properties are “tuned” to represent slower and faster motor units, can increase the apparent strength and perhaps improve the fidelity of simulations of tasks with varying mechanical demands.
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影响因子：
2.4
作者：
Lee, Sabrina S. M.;Arnold, Allison S.;Miara, Maria de Boef;Biewener, Andrew A.;Wakeling, James M.
通讯作者：
Wakeling, James M.
跑步过程中肌肉对推进和支撑的贡献。
影响因子：
2.4
作者：
Hamner, Samuel R.;Seth, Ajay;Delp, Scott L.
通讯作者：
Delp, Scott L.
影响因子：
2.4
作者：
Lu, TW;O'Connor, JJ
通讯作者：
O'Connor, JJ
影响因子：
2.4
作者：
Blemker, Silvia S.;Delp, Scott L.
通讯作者：
Delp, Scott L.
影响因子：
4.6
作者：
Falisse, Antoine;Van Rossom, Sam;De Groote, Friedl
通讯作者：
De Groote, Friedl