Changed visuomotor transformations during and after prolonged microgravity

A series of step-tracking experiments was conducted before, during, and aft er a 3-week space mission to assess the effects of prolonged microgravity o n a non-postural motor-control task. In- and post-flight accuracy was affec ted only marginally. However, kinematic analyses revealed a considerable ch ange in the underlying movement dynamics: too-small force and, thus, too-lo w velocity in the first part of the movements was mainly compensated by len gthening the deceleration phase of the primary movement, so that accuracy w as regained at its end. The observed in-flight decrements in peak velocity and peak acceleration point to an underestimation of mass, in agreement wit h the re-interpretation hypothesis of Sock et. al. Post-flight no reversals of the in-flight changes (negative aftereffects) were found. Instead, ther e was a general slowing down, which could be due to postflight physical exh austion.