Relationship between Pushing Force and Improvement in Total Active Motion in Training with Finger Extensor Facilitation Training Device “iPARKO-2”

The recovery of hand function in chronic stroke survivors is challenging because of finger complexity and post-stroke spasticity. This study developed iPARKO-2, a novel device that simulates the manual finger extensor facilitation technique while overcoming the limitations of the original device. iPARKO-2 enables the simultaneous fixation of the index through the little fingers and applies resistance from the proximal phalanges, allowing training in patients with strong fingertip spasticity. This study is a pilot study aimed at technical validation and feasibility. Five participants underwent training at three distinct target-pushing force levels. Concurrently, their active range of motion and extensor muscle activity were measured. The results show a direct correlation between the increased pushing force and the improvement in total active motion. Furthermore, the level of muscle activity exhibited a positive correlation with the extent of the observed improvement. iPARKO-2 also reduced the fixation time and enhanced usability. These findings suggest that iPARKO-2 effectively enhances voluntary hand movements and that pushing force is a key factor in determining training efficacy.