## 3 Results
### Characteristics of the Study Group
In the presented study, the group of men was too small for detailed cross-gender analyses within the young and old groups. In the next stage of the analysis, interarea differences in rSO\({}_{2}\) values were assessed. It was observed that almost all assessed ROIs differed significantly in mean rSO\({}_{2}\) values, both in the entire study group and in the younger and older groups analyzed separately. The detailed results of the interarea analysis are presented in Table 5 for the entire group and the younger and older groups, respectively. The mean rSO\({}_{2}\) value in the forehead was 67.90 \(\pm\) 6.67 and was significantly lower only in comparison to the middle neck and tibialalis anterior. Simultaneously, the mean value of rSO\({}_{2}\) in the forehead was significantly higher compared to all analyzed ROIs on the back (C-Th, Th-L, L-S) and in the limbs (carpal tunnel, femoral triangle, rectus femoris, ankle joint, biceps femoris, poplitcal fossa gastrocnemius, Achilles tendon, plantar fascia) (\(p\) < 0.05) (Table 5). Similar results were obtained when comparing the forehead to other ROIs performed with a division into the younger and older groups. In both the younger and older groups, the rSO\({}_{2}\) value in the forehead area is lower than in the middle neck and tibialalis anterior but higher for the following ROIs: C-Th, carpal tunnel, rectus femoris, ankle joint, popliteal fossa, Achilles tendon and plantar fascia. Higher values for the forehead were also confirmed for the ROIs Th-L and femoral triangle in the older group and for the ROIs L-S, wrist extensors, cubital fossa, biceps femoris and gastrocnemius in the younger group. \begin{table}
\begin{tabular}{c c c c c c c c} \hline  & & \multicolumn{2}{c}{**Women**} & \multicolumn{2}{c}{**Men**} & \multicolumn{2}{c}{**t-Test**} \\ \cline{3-8}  & & \multicolumn{2}{c}{**n = 51**} & \multicolumn{2}{c}{**n = 19**} & \multicolumn{2}{c}{**t = Test**} \\ \cline{3-8}  & & **Mean [\%]** & \(\pm\)**SD** & **Mean [\%]** & \(\pm\)**SD** & **t** & \(\boldsymbol{p}\) \\ \hline Head & Forehead & 66.75 & 6.48 & 70.33 & 5.39 & \(-\)2.15 & 0.035 \\ \hline Neck & Middle neck & 68.76 & 5.98 & 72.89 & 5.30 & \(-\)2.65 & 0.010 \\ \hline \multirow{4}{*}{Trunk} & Trapezius & 68.91 & 6.40 & 70.58 & 6.20 & \(-\)0.98 & 0.332 \\ \cline{2-8}  & C-Th & 62.77 & 8.29 & 65.05 & 5.86 & \(-\)1.10 & 0.276 \\ \cline{2-8}  & Th-L & 65.09 & 8.33 & 67.47 & 5.80 & \(-\)1.15 & 0.256 \\ \cline{2-8}  & L-S & 65.31 & 5.99 & 68.24 & 7.22 & \(-\)1.72 & 0.091 \\ \hline \multirow{4}{*}{Upper limb} & Wrist extensors & 65.15 & 7.63 & 69.24 & 6.20 & \(-\)2.09 & 0.040 \\ \cline{2-8}  & Cubital fossa & 66.22 & 6.38 & 66.61 & 6.16 & \(-\)0.23 & 0.819 \\ \cline{2-8}  & Carpal tunnel & 55.54 & 9.93 & 58.97 & 8.81 & \(-\)1.33 & 0.190 \\ \hline \multirow{4}{*}{Lower limb} & Femoral triangle & 63.25 & 9.95 & 66.61 & 8.95 & \(-\)1.29 & 0.202 \\ \cline{2-8}  & Rectus femoris & 61.55 & 7.72 & 69.26 & 8.59 & \(-\)3.61 & 0.001 \\ \cline{2-8}  & Tibialis anterior & 69.56 & 6.42 & 70.95 & 8.25 & \(-\)0.75 & 0.460 \\ \cline{2-8}  & Ankle joint & 50.92 & 12.53 & 46.84 & 13.25 & 1.19 & 0.239 \\ \cline{2-8}  & Biceps femoris & 62.85 & 7.17 & 66.71 & 7.98 & \(-\)1.95 & 0.056 \\ \cline{2-8}  & Popitleal fossa & 59.38 & 9.27 & 65.68 & 7.04 & \(-\)2.69 & 0.009 \\ \cline{2-8}  & Gastrocnemius & 64.10 & 8.23 & 66.68 & 9.50 & \(-\)1.13 & 0.266 \\ \cline{2-8}  & Achilles tendon & 44.16 & 15.56 & 30.11 & 19.23 & 3.15 & 0.002 \\ \cline{2-8}  & Plantar fascia & 60.21 & 11.74 & 58.39 & 12.53 & 0.57 & 0.575 \\ \hline \end{tabular}
\end{table} 
Table 4: Gender differences in the study groups.