# Detection of Movement Intention for Operating Methods of Serious Games
## 4 Discussion  
Most of the post-stroke patients with hemiplegia have dysfunction of the upper extremity. The usage of an assistive trainer capable of bilateral exercise to help these patients exercise is an effective rehabilitation strategy [26]. Moreover, studies using serious games to reduce the rejection and boredom of patients toward treatment and induce voluntary participation have been actively ongoing in recent years [27]. In the present study, we developed a novel balance handle as a symmetric upper extremity trainer capable of extension, flexion, pronation, and supination of the upper extremity. We collected the sEMG signal data while the subjects were playing a serious game and recorded the EEG signal data while the subjects were performing basic movements with the balance handle, to analyze the effectiveness of the device as an assistive tool for rehabilitation. In particular, the effectiveness test using the EEG signals was conducted to compare the movement intention with the balance handle to the movement intention in other types of operational methods (hand gripping and gamepad operation) via analysis of the ERD and ERS values. Normality tests were also conducted, and two-way ANOVA and post-hoc analyses were performed for comparative studies. The triceps brachii were activated during the extension movements, whereas the biceps brachii and deltoid muscles were activated during the flexion movements. The deltoid muscles on the opposite side were activated during the tilting of the balance handle to the left or to the right. This ensured that the extensor and flexor muscle activities, essential for increasing the hand and foot functions while moving the balance handle, were properly executed, demonstrating similar sEMG characteristics to other upper extremity trainers [28]. With the balance handle, the ERD peak values were relatively lower while showing higher ERS peak values compared to other types of operating methods. It was noteworthy that the task of pressing the balance handle button revealed a decrease in the ERD peak compared to the task of hand gripping and gamepad operation, which did not show much difference in exercise volume. The lower the ERD peak was, the higher the movement intention was; therefore, it can be inferred that a higher level of movement intention was expressed in the task of utilizing the balance handle [29]. However, for the ERS peak, the higher values reflected more short-term states of inhibiting movement, which corresponds to a previous study that the ERS phenomenon was not necessarily associated with muscle activation in motor cortical networks [30]. As there were some outliers found and data normality was not achieved, detailed classification of the frequency bands needs to be further conducted to reduce individual differences related to motor functions. Most of the previous studies have demonstrated the prediction of movement intention for only a single type of upper extremity movement or either left or right side of the body movement using ERD analysis [31,32]. By contrast, the present study derived movement intention while users operated the balance handle, and showed a considerable difference compared to the other types of operational methods. These data demonstrated the potential for various applications using the upper extremity trainer to bring out an excellent rehabilitative effect, not only through muscle growth but also via identification of large movement intentions inducing brain activation. To develop specific applications to robot rehabilitation or nerve control using brain-computer interface (BCI) technologies, further studies are required to achieve consistent outcomes in securing and comparing the movement intention patterns; for example, by improving the signal processing methods. **Author Contributions:** Conceptualization, S.-T.C. ; methodology, J.-H.P. ; formal analysis, J.-H.P. and H.-S.M. ; investigation, J.-H.P., H.-S.M., H.K. and S.-T.C. ; resources, S.-T.C. ; writing--original draft preparation, J.-H.P. and H.-S.M.