Walsh L D, Allen T J, Gandevia S C, Proske U
Department of Physiology, Monash University, Clayton, Victoria 3800, Australia.
J Appl Physiol (1985). 2006 Apr;100(4):1109-16. doi: 10.1152/japplphysiol.01303.2005. Epub 2005 Dec 22.
This is a study of the ability of blindfolded human subjects to match the position of their forearms before and after eccentric exercise. The hypothesis tested was that the sense of effort contributed to forearm position sense. The fall in force after the exercise was predicted to alter the relationship between effort and force and thereby induce position errors. In the arms-in-front posture, subjects had their unsupported reference arm set to one of two angles from the horizontal, 30 or 60 degrees , and they matched its position by voluntary placement of their other arm. Matching errors were compared with a task where the arms were counterweighted, so could be moved in the vertical plane with minimal effort, and where the arms were moved in the horizontal plane. In these latter two tasks, the intention was to test whether removal of an effort sensation from holding the arm against gravity influenced matching performance. It was found that, although absolute errors for counterweighted and horizontal matching were no larger than for unsupported matching, their standard deviations, 6.1 and 6.8 degrees , respectively, were significantly greater than for unsupported matching (4.6 degrees ), indicating more erratic matching. The eccentric exercise led, the next day, to a fall in maximum voluntary muscle torque of >or=15%. This was accompanied by a significant increase in matching errors for the unsupported matching task from 2.7 +/- 0.5 to 0.8 +/- 0.7 degrees but not for counterweighted (1.4 +/- 0.2 to -0.2 degrees +/- 1.1 degrees ) or horizontal matching (-1.3 +/- 0.7 degrees to -1.8 +/- 0.7 degrees ). This, it is postulated, is because the reduced voluntary torque after exercise was accompanied by a greater effort required to support the arms, leading to larger matching errors. However, effort is only able to provide positional information for unsupported matching where gravity plays a role. In gravity-neutral tasks like counterweighted or horizontal matching, a change in the effort-force relationship after exercise leaves matching accuracy unaffected.
这是一项关于蒙眼人类受试者在离心运动前后匹配其前臂位置能力的研究。所检验的假设是努力感有助于前臂位置感。预计运动后力量的下降会改变努力与力量之间的关系，从而导致位置误差。在手臂前伸姿势下，受试者将其无支撑的参考手臂设置为与水平方向成30度或60度这两个角度之一，然后通过自主放置另一只手臂来匹配其位置。将匹配误差与手臂有配重的任务进行比较，在该任务中手臂可以在垂直平面内以最小的努力移动，以及与手臂在水平平面内移动的任务进行比较。在后两项任务中，目的是测试消除对抗重力支撑手臂的努力感是否会影响匹配表现。结果发现，尽管有配重和水平匹配的绝对误差不大于无支撑匹配的绝对误差，但其标准差分别为6.1度和6.8度，显著大于无支撑匹配的标准差（4.6度），表明匹配更不稳定。离心运动在第二天导致最大自主肌肉扭矩下降≥15%。这伴随着无支撑匹配任务的匹配误差从2.7±0.5度显著增加到0.8±0.7度，但有配重匹配任务（从1.4±0.2度到 -0.2±1.1度）和水平匹配任务（从 -1.3±0.7度到 -1.8±0.7度）的匹配误差没有增加。据推测，这是因为运动后自主扭矩降低的同时，支撑手臂需要更大的努力，导致更大的匹配误差。然而，努力仅能为重力起作用的无支撑匹配提供位置信息。在诸如配重或水平匹配等重力中性任务中，运动后努力 - 力关系的变化对匹配精度没有影响。
