## 4 Discussion  
This study suggests that 3 DSC contributes to reducing muscle activity in upper limb muscles and increasing total scores in 'WST Performance 4.2' and 'QUEST 2.0'. In both men and women, the 3 DSC users' muscle activities were generally lower than those of the CSC users. There was no significant difference between the groups, both men and women, in the activity of the upper trapezius. The reason for this is probably that the use of 3 DSC or CSC is related to the activity of the upper trapezius [17], however, the degree of impact is weak. Moreover, subjects will be able to grasp custom 3 DSC more easily than CSC. In this process, 3 DSC recruit less motor units than CSC, reducing muscle fatigue [18], and this will allow more delicate and accurate control of 3 DSC.  
Wheelchair driving has been reported to differ greatly from gender, even if it is an use in affected side of upper extremities [6]. Since the strength, overall height and body size of male are higher than female, these aspects also affect wheelchair driving. In this study, the results of sEMG showed that men had differences in muscle activation in deltoid middle parts, biceps bracii, triceps bracii, and extensor carpi radialis longus compared to women. For those reasons, there were similar reports of working with ordinary male on wheelchair-guided outdoor driving capabilities compared with elite female individuals [19]. In this research, stroke male showed overwhelming differences in ability to maintain position the body shaking, arm and hand coordination, which was occurred when climbing bumps, turns, curves and slopes. We assumed this disparity would affect the results and other unexpected portion.  
Reflecting on the benefits of this 3 DSC, the WST performance score is statistically significantly higher than CSC for both males and females. The reason for this is probably that 3 DSC is more manipulative and demonstrates better task performance than CSC. It is assumed that 3 DSC users scored better than CSC users in most of the WST performance [20]. It is also assumed that WST Performance is related to user satisfaction, such as QUEST 2.0 scores. This is because QUEST 2.0 scores in 3 DSC were significantly higher than CSC in most categories. Interestingly, it is thought that muscle activation and WST performance and user satisfaction will be closely related [21]. In other words, the low muscle activity of the upper limb muscle allows the user to operate the wheelchair well, and the user's product satisfaction increases when the wheelchair is handled well [22]. This is clinically important because when a wheelchair user can handle a wheelchair well with less muscle strength, this ensures patient satisfaction as well as safety during travel [17; 23].  
The large number of experimental participants are required for a detailed study that conforms to the subject and content of this study however, the number of samples of subjects was no longer available and could not be prevented from dropping outs due to ethical problems. Moreover, kinetic design, such as three-dimensional motion analysis, might be required, but it was not done in this study remains challenges. This study is a RCT and we were concerned that the massive gap between men and women in wheelchair operation would be so severe that it would have a significant impact on the overall data synthesis process.  
We anticipate, based on this result, clinicians may have a basis for prior learning about the issues of clinically applying a new technology called 3D printing, which helped in the clinical decision-making process. Subsequent studies require a more significant larger number of samples and a wider variety of clinical assessment measures to be conducted.