Individual Differences in the Programming of Rapid Bimanual Movements: Are Two Modes Better Than One?

International Journal of Exercise Science 9(3): 347-358, 2016. One of the challenges in performing simultaneous bimanual movements is to prevent interference from one limb to the other, thereby maintaining spatial accuracy in both limbs. Prior research has shown that when a longer distance movement is performed with a shorter movement, the shorter movement overshoots its target and the longer movement undershoots its target relative to control conditions where two shorter or two longer movements are made. The current experiment investigated the motor control strategies used by participants when performing simultaneous aiming movements combining both different and same distances. Participants (N = 20) made rapid lever-positioning movements (goal time to reversal was 350 ms) in the sagittal plane to 2 different spatial targets (20° and 60°) or the same targets (either 20° or 60°). Feedback about spatial accuracy was provided immediately after each trial. Constant error (CE) was measured for each distance based on 20 practice trials per condition. The CE from the same- and different-distance conditions were compared with separate one-way ANOVAs with repeated measures. Overshooting was shown of the 20° target and undershooting of the 60° target when the two distances were performed together. However, the movement amplitudes were positively correlated over trials in both the same- and different-distance conditions. A trial-by-trial analysis of the CE scores revealed both compensatory and non-compensatory strategies. The results suggest individual differences in how amplitude parameters are chosen for use with the generalized motor program in the control of bimanual aiming movements