## 4 Discussion  
The purpose of the present study was to investigate the feasibility and effectiveness of a pseudo-weight resistance training program using an MR Glass (HoloLens) device on shoulder muscle activation in healthy adults. Our results show that training with a pseudo-weight while wearing the MR Glasses effectively affected the activity of some muscles tested. Although an increase in muscle activation was observed in the anterior deltoid, middle deltoid, and supraspinatus, mean muscle activation was comparatively lower than in the control group. Additionally, while no statistically significant difference was observed between the MR group and the control group, training using a pseudo-weight with the MR Glasses produced less muscle activation both before and after the training compared with their baseline MVIC. In our experiment, participants repeated various shoulder movements, including flexion, extension, adduction, and abduction in a rhythmic and steady sequence. Thus, we can postulate that participants' motivation and degree of immersion during the performance of the exercises were greater in the MR group compared with the exercise performed using physical weights in the control group. However, our findings showed that all muscle activities in the MR group were lower than those in the control group. This can be explained by the fact that using the pseudo-weight with the avatar in some way reduced the haptic sense of weight, and the amount of muscle activity became lower due to the lack of physical contact with the real world. Additionally, low muscle activation in the MR group in the present study may be due to limited realistic weight recognition, as this completely relied on visual perception of the weighted dumbbells. This explanation is supported by a previous study conducted by [PERSON] et al. [27] who affirmed that weight recognition during exergames in VR or AR environments is an essential factor that contributes to a more realistic interaction with virtual objects, which may directly influence muscle activation. Contrary to previous studies that used the vibration of electric muscle stimulators or controllers [28; 29], our approach used visual information and a hand-tracking algorithm to manipulate weighted dumbbells. In terms of resistance exercise, it has been reported that physiological responses to resistance appear generally in the nervous system, which plays a crucial role in the initial contraction and adaptation of muscles [30; 31]. It is possible to increase muscle activation using physical weights without visible changes in the muscle, placing emphasis on the haptic effect of weight resistance. Although using MR Glasses with pseudo-weights provides a realistic effect of weight exercise, its impact on weight perception and neuronal activity may be limited without real haptic perception. In a previous study, [PERSON] et al. [32] affirmed that when resistance was maintained steadily and then increased during the training period, it resulted in muscle adaptation and high potential action in the motor unit. In our study, we used a steady resistance load for both the MR group and the control group. However, the force of the hand grip at the \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Questions**} & \multicolumn{2}{c}{**Answers**} \\ \cline{2-3}  & **Yes** & **No** \\ \hline Did you feel any pain while using MR Glass? & 0 & 16 \\ Did you feel any pain after using MR Glass? & 0 & 16 \\ Did you feel any visual fatigue while using MR Glass? & 3 & 13 \\ Did you feel any visual fatigue after using MR Glass? & 4 & 12 \\ Do you think the MR Glass is comfortable? & 10 & 6 \\ Did you feel and autonomous? & 12 & 4 \\ Do you think MR Glass can be used for training programs? & 14 & 2 \\ Did you lose balance while using MR Glass? & 3 & 13 \\ Did you feel the real environment while using MR Glass? & 9 & 7 \\ Did you feel lost in the notion of time with MR Glass? & 0 & 16 \\ \hline \hline \end{tabular} Values are reported as the number of answers.  
\end{table}