The purpose of this study was to investigate whether adaptive responses to error-augmentation force fields, would decrease the trajectory errors in hand-reaching movements in multiple directions in healthy individuals. The study was conducted, as a randomized controlled trial, in 41 healthy subjects. The study group trained on a 3D robotic system, applying error-augmenting forces on the hand during the execution of tasks. The control group carried out the same protocol in null-field conditions. A mixed-model ANOVA was implemented to investigate the interaction between groups and time, and changes in outcome measures within groups. The findings were that there was a significant interaction effect for group × time in terms of the magnitude of movement errors across game-sets. The trajectory error of the study group significantly decreased from 0.035 ± 0.013 m at baseline to 0.029 ± 0.011 m at a follow-up, which amounted to a 14.8% improvement. The degree of movement errors were not significantly changed within a game-set. We conclude that practicing hand-reaching movement in multiple random directions, using the error-augmentation technique, decreases the deviation of the hand trajectory from a straight line. However, this type of training prevents the generalizability of adaptation between consecutive reaching movements. Further studies should investigate the feasibility of this training method for rehabilitation of post-stroke individuals.
Keywords: Adaptation; Brain model; Error-augmentation; Force-field; Hand reaching; Hand trajectory.