Motor skills under varied gravitoinertial force in parabolic flight.

Parabolic flight produces brief alternating periods of high and low gravitoinertial force. Subjects were tested on various paper-and-pencil aiming and tapping task during both normal and varied gravity in flight. It was found that changes in g level caused directional errors in the z body axis (the gravity axis), the arm aiming too high under 0 g and too low under 2 g. The standard deviation also increased for both vertical and lateral movements in the mid-frontal plane. Both variable and directional errors were greater under 0g than 2g. In an unpaced reciprocal tapping task subjects tended to increase their error rate rather than their movement time, but showed a non-significant trend towards slower speeds under 0g for all movement orientations. Larger variable errors or slower speeds were probably due to the difficulty of re-organising a motor skill in an unfamiliar force environment, combined with anchorage difficulties under 0g.