LOAD COMPENSATION IN HUMAN GOAL-DIRECTED ARM MOVEMENTS
LOAD COMPENSATION IN HUMAN GOAL-DIRECTED ARM MOVEMENTS
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DOI：
10.1016/0166-4328(90)90106-o
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发表时间：
1990-12-21
影响因子：
2.7
通讯作者：
BOCK, O
中科院分区：
文献类型：
--
作者：
BOCK, O
我们分析了当重量或弹簧载荷施加到指点手上时，人类多关节指点运动的执行情况。手臂和手位置的视觉反馈被排除在外。运动路径、最终位置和归一化速度分布被发现是与载荷无关的，除了载荷变化后的第一个运动。随着负重大小的增加，速度减小，运动持续时间以相同的因子增加，即速度剖面在大小和时间上重新标度。相反，在弹簧负载下，运动速度和持续时间与无负载对照组没有区别。这些发现导致我们提出了一个新的假说，即由电机系统进行负载补偿。我们认为，一个重要的受控变量是一个虚构的作用于手的力，该力中与惯性和重力相关的分量分别进行控制；然后，通过对与惯性相关的分量进行时间缩放和对与重力相关的分量进行幅度缩放来补偿载荷。关于重量和弹簧载荷下的运动路径和速度的这一假说的预测与我们的实验数据有很好的定量一致性。当被特别要求这样做时，我们的受试者能够在重量负荷下产生与在无负荷条件下没有区别的速度分布，这表明当需要时可以使用其他控制策略。
We analysed the execution of multijoint pointing movements in humans while weight or spring loads were applied to the pointing hand. Visual feedback on arm and hand position was excluded. Movement paths, final positions, and normalized velocity profiles were found to be load-independent, except for the very first movement after a load change. With increasing size of weight load velocity decreased, movement duration increased by the same factor, i.e., the velocity profiles were rescaled in magnitude and time. In contrast, under a spring load movement velocity and duration were not different from no-load controls. These findings led us to propose a new hypothesis on load compensation by the motor system. We suggest that an important controlled variable is a fictional force acting externally on the hand, and that the inertia- and gravity-related components of this force are controlled separately; then, loads are compensated by time scaling of the inertia-related, and magnitude scaling of the gravity-related component. The predictions of this hypothesis regarding movement paths and velocities under weight and spring loads are in good quantitative agreement with our experimental data. When specifically asked to do so, our subjects were able to generate velocity profiles under a weight load that were not different from those under no-load conditions, which suggests that alternative control strategies are available when needed.