New "iPARKO" finger extensor facilitation training device for chronic hemiplegic hand after stroke: Development and verification of its effectiveness in healthy individuals

Abstract After stroke, hemiplegic individuals have difficulty opening their hands by themselves due to paralysis. A finger extensor facilitation technique was therefore developed to increase the activity of the extensor muscle in hemiplegic individuals who cannot open their paralyzed hands by themselves. In our previous study, we created a training device prototype called the "PARKO", that imitates the finger extensor facilitation technique; however, the activity of the extensor muscle using the device was much smaller than that of the finger extensor facilitation technique. In this study, we developed a new finger extensor facilitation training device, the "iPARKO", to increase the activity of the extensor muscle during active training. We thus improved the structure of the PARKO device—including a modified method to apply force to the fingertips—and attached force sensors to the device to monitor these forces. To verify the effectiveness of the iPARKO device, we conducted active training using the device in healthy individuals. Comparing the results of the muscle activities between the PARKO and iPARKO devices among three healthy subjects demonstrated that the iPARKO device increased the mean activity of the extensor muscle by 43.8%, and decreased the mean activity of the flexor muscle by 33.7% when compared with the PARKO device. Additionally, when the iPARKO device was used to apply force to the fingertips, the fingertip forces and normalized values for maximum voluntary contraction of the extensor muscle were revealed in two healthy subjects. In conclusion, the iPARKO device improved the accuracy of imitating manual therapy compared with the PARKO device.