## 4 Discussion  
The main findings of this study show that the SRM enables intensive and repetitive lower extremity strengthening in post-stroke patients with cognitive impairment and that the SRM is feasible and safe as part of an inpatient rehabilitation program. This study indicates that the functional improvement is the result of many factors such as spontaneous recovery, conventional treatment, and the SRM. Therefore, the SRM's effect on functional recovery cannot be known exactly. Although this study does not provide an exact conclusion about the effect of SRM training regarding recovery rate or final outcome as compared to other conventional programs, our findings suggest a positive effect on that aspect and may guide further research. In conventional training, a tilt table, robot-assisted training [24], body-weight-supported treadmill training [25], therapist-assisted training, and braces are used to achieve upright standing and to compensate for lower extremity and trunk weakness. The degree of neurological deficit due to stroke is very diverse, and the application of conventional training and active participation are limited for post-stroke patients with cognitive impairment due to stroke cognitive decline [26]. Therefore, it is difficult to apply robot-assisted and task-performing training, which has become popular in recent years [27; 28]. On the contrary, exercise using the SRM is a very simple movement that flexes and extends the lower extremities and allows the patient to instinctively learn the training method with a few repetitions in a short time. Moreover, SRM training can be easily applied to patients at a relatively low cost. \begin{table}
\begin{tabular}{c c} \hline \hline
**Reasons** & \\ \hline Knee pain & 5 \\ Sleep disturbance or depression & 7 \\ Schedule error & 3 \\ Dizziness & 3 \\ Total & 18 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Reasons for absence from the training. This study was the first to apply SRM training to post-stroke patients with severe cognitive impairment. The patient participation rate was 98.9%, and there were no serious side effects, only minor and transient side effects such as local knee pain or dizziness and nausea. However, whether dizziness and nausea are side effects from SRM training or may have been influenced by the overall condition of the patient is still unclear. We have observed changes and improvements over a wide functional area of post-stroke patients with severely cognitive impairment in this study (Table 2). Patients who have had a stroke with severe cognitive dysfunction usually receive manual therapy with hand guidance, physical therapy using a tilt table or automatic bicycle, but voluntary muscle movements are limited using these therapies. With the SRM, patients can participate actively in the supervision and instructions from the physical therapist before and after the training. In addition, the SRM training system is a machine that physical therapist can use effectively for rehabilitation because it requires less time and effort to compare traditional gait training. Various effects can be expected from the SRM training. First, if the patient is unable to stand independently, they can gradually strengthen their leg muscles by adjusting the SRM inclination, which reduces the load. By unloading a part of the body, the patient can perform a resistive closed kinetic exercise and improve leg muscle strength by repeating knee extension and flexion voluntarily. Previous studies have shown that weight bearing and stepping significantly improve locomotor capacity, which in turn supports the effect of the SRM [29; 30]. Second, by reducing the influence of gravity and the patient's weight, a patient's range of motion can be easily controlled. This may lead to an increase in the patient's self-perceived performance and reduce anxiety and muscle guarding during the exercise through lower extremity flexion. Even post-stroke patients with cognitive decline can be actively involved.