Speed-accuracy trade-off of grasping movements during microgravity

Background Earthbound studies have shown that for pointing movements there is a specific relationship between movement speed, amplitude, and accuracy that is known as Fitts' law. We investigated the validity of Fitts' law for grasping movements in normal and microgravity. Method. Subjects performed grasping movements toward virtual targets under three different time constraint conditions before and during exposure to microgravity in parabolic flights. Results: The "speed-accuracy trade-off" phenomenon was observed for the grasp component of prehension movements. The results were quantitatively similar in normal and microgravity such that increasing the speed resulted in a diminished accuracy. Conclusions: Fitts' lava is partially valid for grasping movements toward virtual targets without visual feedback of the hand in normal gravity. In a microgravity environment, performance of grasping movements also follows some of the predictions of Fitts' law.