Perturbed Point-to-Point Reaching Tasks in a 3D Environment Using a Portable Haptic Device

In this paper, we propose a new protocol, integrating Virtual Reality with the Novint Falcon, to evaluate motion performance during perturbed 3D reaching tasks. The protocol consists of six 3D point-to-point reaching tasks, performed using Falcon with six opposing force fields. Twenty subjects were enrolled in the study. During each task, subjects reached 80 targets and the protocol was repeated over three different days. The trajectories of the end-effector were recorded to calculate: duration of movement, length ratio, lateral deviation, aiming angle, speed metric, and normalized jerk. The coefficient of variation was calculated to study the intra-subject variability and the intra-class correlation coefficient to assess the reliability of the indices. Two-way repeated measurement ANOVA tests were performed for all indices in order to ascertain the effects of force and direction on the trajectories. Duration of movement, length ratio and speed metric have proven to be the most repeatable and reliable indices. Considering the force fields, subjects were able to optimize the trajectory in terms of duration and accuracy but not in terms of smoothness. Considering the directions, the best motor performance occurred when the trajectories were performed in the upper quadrant compared to those performed in the lower quadrant.