Kinematic Trajectories in Response to Speed Perturbations in Walking Suggest Modular Task-Level Control of Leg Angle and Length
Kinematic Trajectories in Response to Speed Perturbations in Walking Suggest Modular Task-Level Control of Leg Angle and Length
复制标题
响应步行速度扰动的运动轨迹建议对腿部角度和长度进行模块化任务级控制
DOI：
10.1093/icb/icac057
复制
发表时间：
2022
影响因子：
2.6
通讯作者：
Daley, M. A.
中科院分区：
文献类型：
--
作者：
Schwaner, M. J.;Nishikawa, K. C.;Daley, M. A.
在复杂地形中导航需要基质、肌肉骨骼和感觉运动系统之间的动态相互作用。目前的扰动研究大多使用可见的地形高度扰动，这不允许我们区分前馈控制、反馈介导和机械扰动响应的神经力学贡献。在这里，我们使用跑步机皮带速度扰动来仅对脚速产生有针对性的扰动，而不会在站立开始时引起关节姿势和腿部负载的地形引起的变化。基于之前的研究表明神经力学控制中存在近远端梯度，我们假设与近端关节相比，远端关节在关节运动学方面会表现出更大的变化。此外，我们期望鸟类使用前馈策略来提高步态的内在稳定性。为了检验这些假设，在稳定和扰动试验中，对七只成年珍珠鸡在电动跑步机上行走时进行了视频记录。扰动包括反复暴露于跑步机带速度的减速和加速。令人惊讶的是，我们发现尽管跑步机带对足部速度产生了很大的扰动，但关节角轨迹和质心波动仍然非常相似。髋关节角度轨迹表现出最大的变化，鸟类在所有扰动的步幅中都采取稍微更弯曲的位置。此外，我们观察到所有步幅的步幅持续时间都增加了，这与控制策略中的前馈变化一致。速度扰动主要影响站立和摆动的时间，减速后的步幅运动学变化最大。我们的研究结果不支持关节控制中近远端梯度的一般假设，因为远端关节运动学基本上保持不变。相反，我们发现腿部角轨迹以及站立和摆动的时间对这种特定的扰动最敏感，并且腿部长度驱动基本上保持不变。我们的结果与腿部长度和腿部角度驱动的模块化任务级控制一致，每种驱动模式具有不同的神经机械控制和扰动灵敏度。远端关节似乎对垂直载荷的变化敏感，但对足部前后速度的变化不敏感。未来的方向应包括肌肉激活和力长度动力学的体内研究，以提供更直接的证据来证明感觉运动控制策略的稳定性，以响应带速扰动。
Navigating complex terrains requires dynamic interactions between the substrate, musculoskeletal, and sensorimotor systems. Current perturbation studies have mostly used visible terrain height perturbations, which do not allow us to distinguish among the neuromechanical contributions of feedforward control, feedback-mediated, and mechanical perturbation responses. Here, we use treadmill-belt speed perturbations to induce a targeted perturbation to foot speed only, and without terrain-induced changes in joint posture and leg loading at stance onset. Based on previous studies suggesting a proximo-distal gradient in neuromechanical control, we hypothesized that distal joints would exhibit larger changes in joint kinematics, compared to proximal joints. Additionally, we expected birds to use feedforward strategies to increase the intrinsic stability of gait. To test these hypotheses, seven adult guinea fowl were video recorded while walking on a motorized treadmill, during both steady and perturbed trials. Perturbations consisted of repeated exposures to a deceleration and acceleration of the treadmill-belt speed. Surprisingly, we found that joint angular trajectories and center of mass fluctuations remain very similar, despite substantial perturbation of foot velocity by the treadmill belt. Hip joint angular trajectories exhibit the largest changes, with the birds adopting a slightly more flexed position across all perturbed strides. Additionally, we observed increased stride duration across all strides, consistent with feedforward changes in the control strategy. The speed perturbations mainly influenced the timing of stance and swing, with the largest kinematic changes in the strides directly following a deceleration. Our findings do not support the general hypothesis of a proximo-distal gradient in joint control, as distal joint kinematics remain largely unchanged. Instead, we find that leg angular trajectory and the timing of stance and swing are most sensitive to this specific perturbation, and leg length actuation remains largely unchanged. Our results are consistent with modular task-level control of leg length and leg angle actuation, with different neuromechanical control and perturbation sensitivity in each actuation mode. Distal joints appear to be sensitive to changes in vertical loading but not foot fore-aft velocity. Future directions should includein vivostudies of muscle activation and force–length dynamics to provide more direct evidence of the sensorimotor control strategies for stability in response to belt-speed perturbations.