## 4 Discussion  
### Main Finding  
Specific activation patterns were identified in the three neck/shoulder muscles that were studied, in accordance with the hypothesis exercise type. Interestingly, the simple exercises, SH and RF, elicited muscle activities of \(>\)60% MVE in mUNE as well as in mUTR. The more advanced exercise, CE, showed \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Muscle**} & \multirow{2}{*}{**Exercise**} & \multirow{2}{*}{**Fatigue** **Development**} & \multicolumn{2}{c}{**20 RM**} & \multicolumn{2}{c}{**12 RM**} \\ \cline{3-8}  & & & **Rep 3.** & **Rep 19.** & \(p\)**-Values** & **Rep 3.** & **Rep 11.** & \(p\)**-Values** \\ \hline mUTR & SH & \%MVC & \(81.2\pm 27.1\) & \(95.6\pm 25.6\) & 0.001 & \(94.3\pm 31.4\) & \(114.1\pm 30.2\) & \(<\)0.001 \\  & & MPF & \(78.5\pm 5.9\) & \(69.8\pm 8.2\) & \(<\)0.001 & \(80.3\pm 12.0\) & \(71.6\pm 10.2\) & \(<\)0.001 \\ \hline mUNE & CE & \%MVC & \(50.7\pm 26.2\) & \(67.5\pm 33.7\) & 0.006 & \(64.5\pm 28.7\) & \(82.4\pm 33.7\) & 0.010 \\  & & MPF & \(66.0\pm 7.6\) & \(57.2\pm 8.9\) & 0.004 & \(63.6\pm 9.4\) & \(57.6\pm 10.6\) & 0.005 \\ \hline mSCM & CF & \%MVC & \(43.9\pm 17.4\) & \(53.5\pm 20.7\) & 0.016 & \(51.4\pm 17.1\) & \(65.0\pm 21.5\) & 0.027 \\  & & MPF & \(104\pm 14.4\) & \(95.2\pm 14.4\) & 0.005 & \(104.0\pm 13.4\) & \(99.1\pm 12.7\) & 0.012 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The fatigue development of mean muscle activity (%MVE) and mean power frequency (MPF) for the upper trapezius muscle (mUTR), upper neck extensors muscles (mUNE), and sternocleidomastoideus muscles mSCM at intensities of 12 and 20 RM. #Values are presented as mean \(\pm\) SD for the exercises shrups (SH), cervical extension (CE), and cervical extension (CF) that resulted in the highest activation of each muscle. Figure 4: The muscle activity (%MVE) of the upper trapezius muscle (mUTR), upper neck extensors muscles (mUNE), and sternocleidomastoideus muscles (mSCM) in the concentric phase (CON) and eccentric phase (ECC) during shugs (SH), cervical extension (CE), and cervical flexion (CF), respectively. * Indicates significant difference between CON and ECC within exercise. numerically slightly higher--but not significantly--activation of mUNE, and CF produced the highest activity in mSCM, but this did not attain >60% MVE neither during 20 RM nor 12 RM and can therefore, not be recommend in case of mSCM insufficiencies. The two muscle groups most often attracting work related pain are mUTR and mUNE [1; 3; 4; 5]. It is therefore interesting that both muscles can be intensively activated by two simple exercises (SH and RF), as this might potentially counteract the work related pain. The CL and CR, which are the most difficult exercises to perform correctly, did not elicit significantly higher percentages of muscle activation than any of the other exercises and can therefore be disregarded, unless for extra training variation. Thereby, our main hypothesis was rejected. Earlier studies have reported significantly higher activation levels of mUTR during SH than RF [17; 28], but this was not the case in the present study. The similar activation levels of mUTR during SH and RF may have great clinical importance due to the difference in force resistance that is required for performing the exercises. When performing the SH exercise for all subjects, a combination of three high resistance elastic bands were needed, whereas only one low resistance elastic band was used during RF. Thus, the SH exercise requires significant grip strength and core stability, which might be challenging for some populations. The mUTRs role as a scapula up- and outward rotator in combination with the significant external moment arm during the RF exercise may explain the high muscle activation in spite of low external resistance. Therefore, the RF exercise might, for some populations, be a more appropriate choice of exercise as compared to the SH. The activity of mUNE was not significantly higher in CE compared to SH and RF.