Haptic training of lower extremities enhanced by visual modality

We investigated the effects of combining the visual and haptic modalities on the adaptation capabilities of healthy subjects to the virtual environment. The haptic feedback was provided by the actuated gait orthosis Lokomat programmed with stepping movements employing an impedance control algorithm. The visual cueing (only the reference motion is presented) and visual feedback (the reference motion as well as the current tracking deviation are presented) were provided by a real-time visualization of a virtual teacher and a virtual self-avatar. The subjects had to track the virtual teacher during stepping-in-place movements shown on screen while being assisted by the Lokomat. The stepping task was performed by engaging three different combinations of haptic and visual modalities. The ^{statistical analysis} showed that (1) haptic feedback and visual feedback combined yielded better tracking than haptic feedback alone, and (2) haptic feedback combined with visual cueing did not improve tracking performance compared to haptic feedback alone. We concluded that in general the haptic training can be effectively enhanced by the visual modality if the latter features visual feedback rather than just cueing.