## 3 Results
### Muscle Activation  
The within-group comparisons for muscle activation showed statistically significant differences in some muscles in both groups. First, in the MR group, the paired-sample \(t\)-test showed a statistically significant difference between the pre-test and post-test in the middle deltoid (\(p=0.024\)), upper trapezius (\(p=0.013\)), and supraspinatus (\(p=0.011\)). Despite an increase in mean value from the pre-test to the post-test in the anterior deltoid, posterior deltoid, and infraspinatus, no statistically significant difference was observed (\(p>0.05\)). In the control group, there were statistically significant differences in the anterior deltoid (\(p=0.014\)), middle deltoid (\(p=0.014\)), upper trapezius (\(p=0.023\)), and supraspinatus \begin{table}
\begin{tabular}{c c c} \hline \hline Anterior deltoid & Elbow flexed at 90\({}^{\circ}\) with shoulder in neutral position. Resistance was applied at the proximal elbow in a backward direction \\ \hline Middle deltoid & Elbow flexed at 90\({}^{\circ}\) with shoulder in 80\({}^{\circ}\) abduction. Resistance was applied at the proximal elbow in a medial–downward direction \\ \hline Posterior deltoid & Elbow flexed at 90\({}^{\circ}\) with shoulder in neutral position. Resistance was applied at the proximal elbow in a forward direction \\ \hline Upper trapezius & Elbow fully extended with shoulder abducted at 90\({}^{\circ}\). Resistance was applied at the proximal elbow in a downward direction \\ \hline Infraspinatus & Elbow flexed at 90\({}^{\circ}\) with shoulder in neutral position. Resistance was applied proximal to the wrist in a medial direction \\ \hline Supraspinatus & Elbow flexed at 90\({}^{\circ}\) with shoulder in 70\({}^{\circ}\) abduction. Resistance was applied proximal to the wrist in a medial direction \\ \hline Adapted from [PERSON] et al. [26]. & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Maximal voluntary isometric contraction measurement settings. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Value** & **MR Group (n = 16)** & **Control Group (n = 16)** & \(p\) \\ \hline Age (year) & 25.50 \(\pm\) 1.54 & 25.25 \(\pm\) 1.61 & 0.658 \\ Height (cm) & 169.50 \(\pm\) 5.12 & 168.81 \(\pm\) 5.20 & 0.709 \\ Weight (kg) & 66.63 \(\pm\) 4.14 & 66.44 \(\pm\) 5.52 & 0.914 \\ BMI (kg/m\({}^{2}\)) & 21.20 \(\pm\) 1.38 & 20.80 \(\pm\) 1.31 & 0.699 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: General characteristics of the participants and baseline muscle activation. (\(p\) = 0.021). However, the posterior deltoid and infraspinatus did not show a significant difference (\(p\) > 0.05), although an increase in mean value was observed between the pre-test and post-test. Second, the independent-sample \(t\)-test used to compare the differences between the two groups showed no statistical difference in muscle activation for any of the six muscles (\(p\) > 0.05). The mean and standard deviation differences for the within-group comparison (pre-test and post-test comparison) are presented in Table 4, and the between-group comparison values are presented in Table 5. The baseline MVIC values are displayed as a reference for participants' muscle contraction but were not used in the analysis of the muscle activity changes in either group since the measurement method was different. Finally, regarding the survey, only participants in the MR group were asked to complete it and the results are presented in Table 6. Although all participants reported no pain during or after the use of the MR Glasses, some reported having visual fatigue during and after wearing the device. Ten of the sixteen participants affirmed that the device was comfortable, and fourteen of them were favorable to using it for long-term training programs. In addition, the majority of participants reported no loss of balance, and no loss of the notion of time was observed in any participants. Some of them reported not to have felt the real environment surrounding them while wearing the MR Glasses. However, no accident, injury, or adverse effect was noticed.