Impulse and movement space-time variability

In 3 experiments, the authors examined movement space-time variability as a function of the force-time properties of the initial impulse in a movement timing task. In the range of motion and movement time task conditions, pea k force, initial rate of force, and force duration were manipulated either independently or in combination across a range of parameter values. The fin dings showed that (a) impulse variability is predicted well by the elaborat ion of the isometric force variability scaling functions of L,. G. Carlton, K. Il. Kim, Y. T. Liu, and K. M. Newell (1993) to movement, and Co) the mo vement spatial and temporal outcome variability are complementary and well predicted by an equation treating the variance of force and time in Newton' s 2nd law as independent random variables. Collectively, the findings sugge st that movement outcome variability is the product of a coherent space-tim e function that is driven by the nonlinear scaling of the force-time proper ties of the initial impulse.