Running stability is enhanced by a proximo-distal gradient in joint neuromechanical control
Running stability is enhanced by a proximo-distal gradient in joint neuromechanical control
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DOI：
10.1242/jeb.02668
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发表时间：
2007-02-01
影响因子：
2.8
通讯作者：
Biewener, A. A.
中科院分区：
文献类型：
--
作者：
Daley, M. A.;Felix, G.;Biewener, A. A.
目前，我们对动物在不平坦和不可预测的地形（通常是其自然环境的特征）上奔跑时如何实现动态稳定性知之甚少。在这里，我们研究了鸟类两足动物（头盔珍珠鸡 Numida meleagris）的肢体和关节力学如何对跑步过程中意外的地形下降做出反应。特别是，我们讨论如何协调关节力学以实现整个肢体的动力学。基于肌肉肌腱结构和之前对稳定和倾斜运动的研究，我们假设关节神经力学控制中存在近远端梯度。在这种运动控制策略中，（1）髋关节和膝关节的近端肌肉主要以前馈方式控制，并表现出对负载不敏感的机械性能，（2）由于内在的机械效应和快速、更高增益的本体感觉反馈，踝关节和跗跖趾（TMP）关节的远端肌肉对负载高度敏感。意外扰动期间的肢体运动学和动力学表明，尽管肢体负荷发生了变化，但主要由髋部控制的肢体回缩在整个扰动步骤中仍然与水平跑步相似。各个关节在水平跑步和扰动跑步期间都会产生或吸收能量，因此肢体净做功取决于关节之间的能量平衡。无论肢体负载如何，髋部都保持相同的机械作用，而踝关节和 TMP 根据地面接触时的肢体姿势在弹簧或阻尼功能之间切换。最初的膝盖角度决定了肢体姿势并改变关节之间的工作平衡，尽管膝盖本身贡献很少。关节功能的这种分布导致肢体工作性能发生姿势相关的变化，从而使珍珠鸡能够快速产生或吸收能量以响应扰动。结果支持了肢体神经肌肉性能和运动控制中存在近远端梯度的假设。这种控制策略允许肢体循环保持恒定，而肢体姿势、负荷和能量表现是相互依赖的。我们认为，这种控制策略提供了简单、快速的机制，用于在崎岖地形上行驶时管理能量和控制速度。
We currently know little about how animals achieve dynamic stability when running over uneven and unpredictable terrain, often characteristic of their natural environment. Here we investigate how limb and joint mechanics of an avian biped, the helmeted guinea fowl Numida meleagris, respond to an unexpected drop in terrain during running. In particular, we address how joint mechanics are coordinated to achieve whole limb dynamics. Based on muscle-tendon architecture and previous studies of steady and incline locomotion, we hypothesize a proximo-distal gradient in joint neuromechanical control. In this motor control strategy, (1) proximal muscles at the hip and knee joints are controlled primarily in a feedforward manner and exhibit load-insensitive mechanical performance, and (2) distal muscles at the ankle and tarsometatarso-phalangeal (TMP) joints are highly load-sensitive, due to intrinsic mechanical effects and rapid, higher gain proprioceptive feedback. Limb kinematics and kinetics during the unexpected perturbation reveal that limb retraction, controlled largely by the hip, remains similar to level running throughout the perturbed step, despite altered limb loading. Individual joints produce or absorb energy during both level and perturbed running steps, such that the net limb work depends on the balance of energy among the joints. The hip maintains the same mechanical role regardless of limb loading, whereas the ankle and TMP switch between spring-like or damping function depending on limb posture at ground contact. Initial knee angle sets limb posture and alters the balance of work among the joints, although the knee contributes little work itself. This distribution of joint function results in posture-dependent changes in work performance of the limb, which allow guinea fowl to rapidly produce or absorb energy in response to the perturbation. The results support the hypothesis that a proximo-distal gradient exists in limb neuromuscular performance and motor control. This control strategy allows limb cycling to remain constant, whereas limb posture, loading and energy performance are interdependent. We propose that this control strategy provides simple, rapid mechanisms for managing energy and controlling velocity when running over rough terrain.