# Analysis of Surface EMG Parameters in the Overhead Deep Squat Performance
## 3 Results
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multicolumn{5}{c}{**Percentage of Maximum Voluntary Contraction (\%MVC)**} \\ \hline \hline \multicolumn{5}{c}{Group 3—correctness of deep squat 85-92\%} \\ \hline \multirow{5}{*}{} & \multicolumn{3}{c}{Lower part body} & \multicolumn{3}{c}{Upper part body} \\  & \multicolumn{3}{c}{Post hoc Dunn’s Tests} & \multicolumn{3}{c}{Mann-Whitney U Test} \\  & \multicolumn{3}{c}{Significant differences} & \multicolumn{3}{c}{Significant differences} \\  & \multicolumn{3}{c}{\(p\)-value} & \multicolumn{3}{c}{effect size (r)} & \multicolumn{3}{c}{between} & \multicolumn{3}{c}{\(p\)-value} \\ \hline \multirow{2}{*}{**\{**\{** \{** \{** \{ \} \} \ \} \  
The average co-activation indexes calculated based on %MVC for selected muscle pairs and individual groups 1-3 are presented in Table 9.  
The average co-activation index (\(CAI\)) with classification range calculated based on %MVC. Figure 11: Box plots for %MVC with division into groups of deep squat level performance: (**a**) group 1—correctness level 23–54%, (**b**) group 2—correctness level 62–77%, group (**c**) 3—correctness level 85–92% for the muscles of lower part of body (rectus femoris, vastus medialis, biceps femoris, and glutetus muscle) as well as for upper part of body (deltoid and latissimus). \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multicolumn{6}{c}{**Median Frequency (_MDF_)**} \\ \hline \multicolumn{6}{c}{Group 3—correctness of deep squat 85-92\%} \\ \hline \multicolumn{6}{c}{Lower part body} \\ \multicolumn{6}{c}{Post hoc Dunn’s Tests} \\ \multicolumn{6}{c}{Significant differences} \\ \multicolumn{6}{c}{between} \\ \multicolumn{6}{c}{\(p\)-value} \\ \multicolumn{6}{c}{effect size (\(r\))} \\ \hline \{ \multirow{2}{*}{} & RF \& BF & 0.0039 & 0.6030 \\ \cline{2-6}  & RF \& GM & 0.0261 & 0.5041 \\ \hline \multicolumn{6}{c}{Group 2—correctness of deep squat 62-77\%} \\ \hline \{ \multirow{2}{*}{} & RF \& GM & 0.0000 & 0.7461 \\ \cline{2-6}  & VM \& GM & 0.0248 & 0.3057 \\ \cline{2-6}  & RF \& BF & 0.0000 & 0.5020 \\ \cline{2-6}  & RF \& VM & 0.0002 & 0.4403 \\ \hline \hline \multicolumn{6}{c}{Group 1—correctness of deep squat 23–54\%} \\ \hline \{ \multirow{2}{*}{} & RF \& BF & 0.0471 & 0.4204 \\ \cline{2-6}  & RF \& GM & 0.0117 & 0.4899 \\ \cline{2-6}  & RF \& GM & 0.0011 & 0.5897 \\ \hline \hline \end{tabular}  
* \(\overline{\{\}}\)retus femoris, VM—vastus medialis, BF—biceps femoris, GM—glutetus muscle, D—deltoid, L—latisimus, \(p\)-value (the level of probability \(p\)), the smallest level of significance for which the calculated value of testing statistic leads to rejection of null hypothesis after taking into account the correction for the number of comparisons, \(r\in(0.0,1)\)—very small effect size, \(r\in(0.1,0.29)\)—small effect size, \(r\in(0.3,0.49)\)—moderate effect size, \(r>0.5\)—large effect size [38].  
\end{table} 
Table 8: Summary list of statistically significant differences between muscle _MDF_ in individual groups 1–3 confirmed by Kruskal–Wallis and Mann–Whitney U tests for the muscles of the lower (glutetus muscle (GM), rectus femoris (RF), vastus medialis (VM), and biceps femoris (BF)) and upper (deltoid (D), latissimus (L)) parts of body, respectively. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multicolumn{1}{c}{**Group**} & **RF and BF** & **VM and BF** & **D and L** & **CAI** & **CAI** \\ \multicolumn{6}{c}{**(evaluation)**} \\ \hline Group 1 (23–54\%) & 0.26 & 0.23 & 0.32 & 0.26–0.32 (0.06) & Low \\ Group 2 (62–77\%) & 0.27 & 0.23 & 0.34 & 0.27–0.34 (0.07) & Low or Moderate \\ Group 3 (85–92\%) & 0.32 & 0.32 & 0.40 & 0.32–0.40 (0.08) & Moderate \\ \hline \hline \end{tabular}  
* RF and BF: co-activation of the extensors (RF) and flexors (BF) of the knee joint. VM and BF: co-activation of the (VM) and (BF—caput longum), one of the thigh flexors. D and L: co-activation of the muscles stabilizing the shoulder girdle and trunk.  
\end{table} 
Table 9: Average co-activation index (\(CAI\)) with classification range calculated based on %MVC.