Hase K, Stein R B
Division of Neuroscience, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
J Neurophysiol. 1998 Jul;80(1):255-61. doi: 10.1152/jn.1998.80.1.255.
The mechanisms involved in rapidly terminating human gait were studied. Subjects were asked to walk at a comfortable speed and to stop walking as soon as they felt an electrical stimulus to the superficial peroneal nerve. This simulated hitting an obstacle with the top of the foot. Stimuli were presented repeatedly at random during a 20-min period of walking. Electromyograms and joint angular movements of the right leg and forces under both feet were recorded. The step cycle was divided into 16 parts, and the responses to stimuli in each part were analyzed separately. Subjects generally stopped with the right foot in front of the left or vice-versa, depending on when the stimulus was applied in the step cycle. There was also a transition region in which subjects would rise up on their toes and either back down or take one more quick, short forward step. Three different mechanisms were used to produce a stop. 1) An extension synergy in the swing leg was initiated just before this leg hit the ground to brake the forward momentum of the body. 2) The push-off phase of the stance leg was inhibited to reduce the forward thrust and maintain the stance leg on the ground behind the body. 3) If these mechanisms were insufficient, the body rose up onto the toes of the extended forward leg and thereby converted more kinetic energy to potential energy. A decision to take an additional step depends on whether the momentum of the body is sufficient to carry the center of mass in front of its support on the forward leg. If so, an additional step is taken. Despite the complexity of the decisions that must be made, changes in electromyographic activity are seen throughout the legs and trunk in 150-200 ms.
对快速终止人类步态所涉及的机制进行了研究。受试者被要求以舒适的速度行走，并在感到腓浅神经受到电刺激时立即停止行走。这模拟了用脚尖踢到障碍物的情况。在20分钟的行走过程中，随机反复施加刺激。记录了右腿的肌电图、关节角运动以及双脚下方的力。将步周期分为16个部分，并分别分析每个部分对刺激的反应。受试者通常会根据刺激在步周期中施加的时间，使右脚停在左脚前方或反之亦然。还有一个过渡区域，在这个区域中，受试者会踮起脚尖，然后要么再落下来，要么再快速向前迈出一小步。使用了三种不同的机制来实现停止。1）在摆动腿着地之前启动摆动腿的伸展协同作用，以制动身体的向前动量。2）抑制支撑腿的蹬地阶段，以减少向前推力并使支撑腿保持在身体后方的地面上。3）如果这些机制不够充分，身体会上升到伸展的前腿的脚尖上，从而将更多的动能转化为势能。决定是否再迈出一步取决于身体的动量是否足以将重心带到前腿支撑点的前方。如果是这样，就会再迈出一步。尽管必须做出的决策很复杂，但在150 - 200毫秒内，整个腿部和躯干的肌电活动都有变化。
