Coordination of push-off and collision determine the mechanical work of step-to-step transitions when isolated from human walking
Coordination of push-off and collision determine the mechanical work of step-to-step transitions when isolated from human walking
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DOI：
10.1016/j.gaitpost.2011.09.102
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发表时间：
2012-02-01
期刊：
影响因子：
2.4
通讯作者：
Donelan, J. Maxwell
中科院分区：
文献类型：
--
作者：
Soo, Caroline H.;Donelan, J. Maxwell
在人类行走中，每次转换到新的站姿肢体都需要将重心(COM)速度从一个倒立摆圆弧重定向到下一个圆弧。虽然这可以通过前肢的负碰撞功、后肢的正推力功或两者的某种组合来实现，但基于物理的步进式转变模型预测，当推力功和碰撞功的大小相等时，总的正功最小。在这里，我们测试了推力和碰撞功的协调在确定过渡功时的重要性，使用脚踝和膝关节支撑来限制腿对身体执行正功的能力。为了将过渡与行走机械的其他贡献者隔离开来，参与者被指示从一条腿到另一条腿来回摇摆，将运动限制在矢状面，消除了摆动腿的需要。我们发现，减少的推出功增加了在每个转变期间完成COM速度重定向所需的碰撞功。当摇摆偏离预测的步到步过渡的最佳协调时，需要更多的总机械功，在这种情况下，推离功和碰撞功的大小相等。我们的研究发现，如果一条腿或两条腿没有以最佳的协调性推开，转换功就会增加，这可能有助于解释病理性步态的代谢成本增加，而不考虑病因。(C)2011爱思唯尔B.V.保留所有权利。
In human walking, each transition to a new stance limb requires redirection of the center of mass (COM) velocity from one inverted pendulum arc to the next. While this can be accomplished with either negative collision work by the leading limb, positive push-off work by the trailing limb, or some combination of the two, physics-based models of step-to-step transitions predict that total positive work is minimized when the push-off and collision work are equal in magnitude. Here, we tested the importance of the coordination of push-off and collision work in determining transition work using ankle and knee joint braces to limit the ability of a leg to perform positive work on the body. To isolate transitions from other contributors to walking mechanics, participants were instructed to rock back and forth from one leg to the other, restricting motion to the sagittal plane and eliminating the need to swing the legs. We found that reduced push-off work increased the collision work required to complete the redirection of the COM velocity during each transition. A greater amount of total mechanical work was required when rocking departed from the predicted optimal coordination of step-to-step transitions, in which push-off and collision work are equal in magnitude. Our finding that transition work increases if one or both legs do not push-off with the optimal coordination may help explain the elevated metabolic cost of pathological gait irrespective of etiology. (C) 2011 Elsevier B.V. All rights reserved.