## 2 Materials and Methods
### Evaluation of Muscle Force

Table 9: Statistical description of muscle force parameters. With regard to maximal force, left and right symmetry shows a dominance of the left-hand side and a difference of 3.12% for knee extensors. For knee flexors the same parameter has a dominance on the right-hand side, and symmetry is 2.25%. In this case, the symmetry is close between knee extensors and knee flexors. Left and right symmetry for duration of maintained maximal force shows a dominance of the left hand, and the value is 2.02% for knee extensors. For knee flexors, the same parameter has a dominance for the left-hand side, and symmetry is 4.29% (see Table 10). With regard to this parameter, we see a left/right symmetry that is also close between knee extensors and knee flexors. A statistical analysis of muscle parameters was made using the _Student t-test_ (\(p=0.06\)) and shows that there are no significant statistical differences between the left- and right-hand sides, as shown in Table 11.  
About agonist and antagonist muscle symmetry we observe that there is a significant statistical difference regarding muscle force, but there is no significant statistical difference regarding duration of maintained maximal muscle force, as can be seen in Table 12. \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Subject Code**} & **EG Medium of** & **EG Maximal** & **EG Duration** & **FG Medium of** & **FG Maximal** & **FG Duration of** \\  & **Maximal Force** & **Force** & **Maximal Force** & **Maximal Force** & **Force** & **Maintained** \\  & **Difference** & **Difference** & **Difference** & **Difference** & **Difference** \\  & **Left/Right (\%)** & **Left/Right (\%)** & **Left/Right (\%)** & **Left/Right (\%)** & **Left/Right (\%)** & **Left/Right (\%)** \\ \hline
1 & 6.25 & 2.87 & 27.92 & \(-44.74\) & \(-16.49\) & 12.50 \\
2 & \(-22.12\) & \(-2.09\) & 39.31 & \(-17.18\) & \(-2.71\) & 0.69 \\
3 & \(-3.30\) & 1.45 & 18.75 & \(-22.39\) & \(-17.04\) & 34.18 \\
4 & \(-11.52\) & \(-2.72\) & 5.88 & \(-83.61\) & \(-0.39\) & \(-17.43\) \\
5 & \(-9.92\) & \(-5.46\) & \(-77.78\) & 10.62 & \(-6.95\) & \(-57.63\) \\
6 & \(-2.17\) & 6.74 & 46.03 & \(-3.34\) & \(-2.62\) & 35.54 \\
7 & 0.51 & 9.91 & \(-33.80\) & 50.34 & 15.98 & 40.23 \\
8 & 0.59 & 12.46 & 26.11 & \(-7.24\) & \(-9.76\) & \(-165.38\) \\
9 & \(-9.38\) & \(-0.24\) & 25.00 & \(-10.56\) & 5.15 & 24.14 \\
10 & 15.71 & \(-8.73\) & 45.30 & 4.94 & 13.04 & \(-50.00\) \\
11 & \(-11.56\) & 19.14 & 2.04 & \(-28.79\) & \(-22.18\) & 39.11 \\
12 & 14.01 & 13.59 & \(-26.67\) & 15.88 & 7.61 & \(-3.64\) \\
13 & \(-9.51\) & 0.30 & \(-36.00\) & 20.23 & 10.94 & 11.64 \\
14 & \(-11.93\) & \(-8.19\) & 14.49 & 27.52 & \(-0.38\) & 41.54 \\
15 & \(-12.00\) & \(-17.82\) & 13.66 & \(-4.07\) & 2.60 & 22.22 \\
16 & \(-15.70\) & 9.85 & \(-32.92\) & 3.97 & 11.55 & 45.00 \\
17 & 44.93 & 20.34 & 56.64 & \(-29.28\) & \(-13.69\) & 74.54 \\
18 & 7.60 & 4.67 & \(-77.57\) & \(-18.74\) & \(-15.13\) & \(-10.00\) \\ \hline
**Average value** & \(\mathbf{-1.64}\) & **3.12** & **2.02** & \(\mathbf{-7.58}\) & \(\mathbf{-2.25}\) & **4.29** \\ \hline \end{tabular}
\end{table} 
Table 11: Statistical results, left- and right-hand sides. Because the duration of maintained maximal muscle force is one of the elements that could indicate muscle fatigue and also the decrease in muscle performance, we consider that is important to analyse whether or not there is a correlation between the average values of SQS, CASQ scores, and the average duration of maximal muscle force for knee extensors and flexors, left and right sides. The results are presented in Tables 13 and 14. An analysis of the results shows us that the lowest SQS score is correlated with an increase in the average duration of maintained maximal muscle force, in the case of knee extensors and flexors. With regard to the relationship between this parameter and the sleep scales (SQS and CASQ) score evaluation, we can see that there is no relationship and that sleep quality and/or sleepiness do not influence muscle fatigue.