Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany.
Computational Biophysics and Biorobotics, University of Stuttgart, Stuttgart, Germany.
Sci Rep. 2023 Nov 9;13(1):19575. doi: 10.1038/s41598-023-45821-w.
In legged locomotion, muscles undergo damped oscillations in response to the leg contacting the ground (an impact). How muscle oscillates varies depending on the impact situation. We used a custom-made frame in which we clamped an isolated rat muscle (M. gastrocnemius medialis and lateralis: GAS) and dropped it from three different heights and onto two different ground materials. In fully activated GAS, the dominant eigenfrequencies were 163 Hz, 265 Hz, and 399 Hz, which were signficantly higher (p < 0.05) compared to the dominant eigenfrequencies in passive GAS: 139 Hz, 215 Hz, and 286 Hz. In general, neither changing the falling height nor ground material led to any significant eigenfrequency changes in active nor passive GAS, respectively. To trace the eigenfrequency values back to GAS stiffness values, we developed a 3DoF model. The model-predicted GAS muscle eigenfrequencies matched well with the experimental values and deviated by - 3.8%, 9.0%, and 4.3% from the passive GAS eigenfrequencies and by - 1.8%, 13.3%, and - 1.5% from the active GAS eigenfrequencies. Differences between the frequencies found for active and passive muscle impact situations are dominantly due to the attachment of myosin heads to actin.
在腿部运动中，肌肉会因腿部与地面接触（冲击）而产生阻尼振荡。肌肉的振荡方式因冲击情况而异。我们使用了一个定制的框架，将一个分离的大鼠肌肉（M. gastrocnemius medialis 和 lateralis：GAS）夹在其中，并从三个不同的高度将其放下到两种不同的地面材料上。在完全激活的 GAS 中，主导本征频率为 163 Hz、265 Hz 和 399 Hz，与被动 GAS 的主导本征频率（139 Hz、215 Hz 和 286 Hz）相比显著更高（p < 0.05）。一般来说，无论是改变下落高度还是地面材料，都不会导致主动或被动 GAS 的本征频率发生任何显著变化。为了将本征频率值追溯到 GAS 刚度值，我们开发了一个 3DoF 模型。该模型预测的 GAS 肌肉本征频率与实验值吻合较好，与被动 GAS 本征频率相比偏差分别为 -3.8%、9.0%和 4.3%，与主动 GAS 本征频率相比偏差分别为 -1.8%、13.3%和 -1.5%。主动和被动肌肉冲击情况之间发现的频率差异主要归因于肌球蛋白头部与肌动蛋白的结合。
