History-dependent perturbation response in limb muscle

Muscle mediates movement but movement is typically unsteady and perturbed. Muscle is known to behave non-linearly and with history dependent properties during steady locomotion, but the importance of history dependence in mediating muscles function during perturbations remains less clear. To explore muscle's capacity to mitigate perturbations during locomotion, we constructed a series of perturbations that varied only in kinematic history, keeping instantaneous position, velocity and time from stimulation constant. We find that muscle's perturbation response is profoundly history dependent, varying by four fold as baseline frequency changes, and dissipating energy equivalent to  ~6 times the kinetic energy of all the limbs in 5 ms (nearly 2400 W Kg-1). Muscle's energy dissipation during a perturbation is predicted primarily by the force at the onset of the perturbation. This relationship holds across different frequencies and timings of stimulation. This history dependence behaves like ...

肌肉介导运动，但运动通常并不稳定，且易受扰动（perturbation）。已知肌肉在稳定运动过程中表现出非线性特性且具有历史依赖性，但在扰动过程中，历史依赖性对肌肉功能的调控作用仍不甚明确。为探究肌肉在运动过程中缓解扰动的能力，我们设计了一系列仅运动学历史（kinematic history）存在差异的扰动实验，同时保持瞬时位置、速度以及刺激（stimulation）后的时长恒定。我们发现，肌肉对扰动的响应具有极强的历史依赖性：随着基础频率变化，响应强度可相差四倍，且在5毫秒内可耗散相当于所有肢体总动能约6倍的能量（近2400 W·kg⁻¹）。肌肉在扰动过程中的能量耗散主要可由扰动起始时刻的肌力进行预测。该关系在不同刺激频率与刺激时机下均成立。这种历史依赖性的表现类似于……