EFFECT OF VISION AND STANCE WIDTH ON HUMAN-BODY MOTION WHEN STANDING - IMPLICATIONS FOR AFFERENT CONTROL OF LATERAL SWAY
EFFECT OF VISION AND STANCE WIDTH ON HUMAN-BODY MOTION WHEN STANDING - IMPLICATIONS FOR AFFERENT CONTROL OF LATERAL SWAY
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DOI：
10.1113/jphysiol.1993.sp019824
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发表时间：
1993-09-01
影响因子：
5.5
通讯作者：
MARSDEN, CD
中科院分区：
文献类型：
--
作者：
DAY, BL;STEIGER, MJ;MARSDEN, CD
1.本文对35名男性受试者在不同站姿宽度、闭眼或睁眼条件下的直立运动进行了三维测量。身体运动是从固定在身体上从肩膀到脚踝的特定部位的八个标记的运动推断出来的。这些标记的运动与地面反作用力合力作用点（压力中心）的运动一起记录下来。通过闭上眼睛或缩小站立宽度，身体的速度（8个地点的平均值）增加，这两个因素之间存在相互作用，当脚靠得更近时，视觉更有效地降低身体速度。虽然站立宽度对横向速度分量的影响更大，但在额状面和矢状面的速度分量之间存在相似的关系.身体位置的波动也会因眼睛闭合或站立宽度变窄而增加。同样，站立宽度的影响是更有力的横向比前后运动。与速度测量相反，视力和站立宽度之间没有相互作用。有一个渐进的位置和速度波动的幅度从标记放置在身体上更高。压力中心位置的波动幅度与放置在髋关节附近的标记相似。然而，压力中心的速度波动大于身体上的任何部位。通过对标记点相邻直线段间角运动幅度的分析表明，倒立摆人体摇摆模型是不完整的。踝关节运动仅在额面侧位运动中占主导地位，且站立宽度较窄（< 8 cm）。对于所有其他条件下，大多数角运动发生在躯干和腿之间。随着站立宽度的增加，横向身体运动的大幅减少主要是由于脚踝和脚的角运动不成比例地减少。骨骼结构的数学模型已经构建，它为关节运动的这种特定减少提供了一些解释。该模型表明，当膝盖被锁定的踝关节和髋关节成为耦合在一起，使运动的一个是伴随着其他的运动。这种耦合的强度随着站立宽度而增加。因此，腿部骨盆结构的刚度通过增加站立宽度而被动地增加。髋关节和踝关节的耦合也预示着随着站立宽度的增加，本体感受对踝关节侧向运动的敏感性增加，这可能是导致观察到的侧向运动减少的一个因素。与此同时，该模型预测，来自头部（视觉和前庭）受体的信息随着站立宽度的增加而在检测脚踝的横向运动时变得不那么敏感。这可能解释了为什么视觉在降低具有较大站立宽度的身体的横向速度方面不太有效。
1. Measurements of human upright body movements in three dimensions have been made on thirty-five male subjects attempting to stand still with various stance widths and with eyes closed or open. Body motion was inferred from movements of eight markers fixed to specific sites on the body from the shoulders to the ankles. Motion of these markers was recorded together with motion of the point of application of the resultant of the ground reaction forces (centre of pressure).2. The speed of the body (average from eight sites) was increased by closing the eyes or narrowing the stance width and there was an interaction between these two factors such that vision reduced body speed more effectively when the feet were closer together. Similar relationships were found for components of velocity both in the frontal and sagittal planes although stance width exerted a much greater influence on the lateral velocity component.3. Fluctuations in position of the body were also increased by eye closure or narrowing of stance width. Again, the effect of stance width was more potent for lateral than for anteroposterior movements. In contrast to the velocity measurements, there was no interaction between vision and stance width.4. There was a progressive increase in the amplitude of position and velocity fluctuations from markers placed higher on the body. The fluctuations in the position of the centre of pressure were similar in magnitude to those of the markers placed near the hip. The fluctuations in velocity of centre of pressure, however, were greater than of any site on the body.5. Analysis of the amplitude of angular motion between adjacent straight line segments joining the markers suggests that the inverted pendulum model of body sway is incomplete. Motion about the ankle joint was dominant only for lateral movement in the frontal plane with narrow stance widths (< 8 cm). For all other conditions most angular motion occurred between the trunk and leg.6. The large reduction in lateral body motion with increasing stance width was mainly due to a disproportionate reduction in the angular motion about the ankles and feet. A mathematical model of the skeletal structure has been constructed which offers some explanation for this specific reduction in joint motion.7. The model demonstrates that when the knees are locked the joints of the ankles and hips become coupled together so that movement of one is accompanied by movement of the others. The strength of this coupling increases with stance width. The stiffness of the legs-pelvic structure is therefore passively increased by increasing stance width.8. Coupling of the hips and ankles also predicts an increase in proprioceptive sensitivity to lateral motion about the ankles with increasing stance width, a factor which may contribute to the observed reduction in lateral motion. At the same time the model predicts that information from receptors in the head (visual and vestibular) become less sensitive in the detection of lateral motion about the ankles with increasing stance width. This may explain why vision was less effective in reducing lateral velocity of the body with greater stance widths.