# Analysis of Surface EMG Parameters in the Overhead Deep Squat Performance
## 3 Results  
The determined normalized excitation values taken into account in the analysis of selected muscles for individual groups 1-3 are shown in Figure 10.  
In the first step of the statistical analysis, the assumptions concerning normal distribution and homogeneity of variance for all examined parameters of individual muscles were verified. According to the Shapiro-Wilk test (for normality) and the Levene test (for homogeneity of variance), we had to reject the null hypothesis of a normal distribution of %MVC, \(MF\), \(MDF\), and \(kurt\) for most (except for the rectus femoris) of the muscles considered, as well as the null hypothesis of equality of means of %MVC, \(MF\), \(MDF\), and \(kurt\) for muscles taken into account. Since the conditions regarding normal distribution and homogeneity of variance were not met, and additionally due to the small sample size, the nonparametric Kruskal-Wallis ANOVA test (based on ranks) was applied for further analysis. The statistical relationship between selected parameters (% MVC, \(MF\), \(MDF\), and \(kurt\)) and the quality of deep squat technique was tested for muscles in the upper (deltoid and latissimus dorsi) and lower (gluteus muscle, rectus femoris, vastus medialis, and biceps femoris) parts of the body. The most interesting results (significant statistical differences) were obtained for %MVC and \(MDF\), so in further analysis, we focus on these parameters. We present the accurate results of %MVC analysis as well as the summarized (Table 8) results for \(MDF\). In the Kruskal-Wallis test performed for the rectus femoris, vastus medialis, biceps femoris, and gluteus muscles, without division into groups and with a variable grouping of the muscles, there appeared a statistically significant (\(p<0.00001\)) difference in %MVC for the tested muscles. In the next step, the analysis was performed on groups 1-3 (group 1 (23-54%) of correctness exercises, group 2 (62-77%), and group 3 (85-92%)). The higher the group index, the better the deep squat was performed. Further analysis for individual groups 1-3 confirmed a significant difference in %MVC for muscles tested in individual groups for group 1 (\(p=0.0021\)), group 2 (\(p<0.00001\)), and group 3 (\(p=0.0001\)) with the large effect size in each group (Table 3). The question arises as to which muscle excitation level in particular groups results in the emergence of statistically significant differences in these groups. Multiple comparison post hoc tests were performed to answer the question of which of the pairs of the compared muscles were responsible for rejecting the null hypothesis: n independent samples come from the same population (distribution) or the population with the same median. The results obtained by the post hoc [PERSON]'s tests with Bonferroni correction are presented in Tables 4-6. In the presented \(p\)-values, the correction for the number of comparisons was taken into account to simplify the comparison with the assumed \(\alpha\)-significance level. The statistically significant differences between muscle excitation are highlighted in red in Tables 4-6. The same analysis was performed for upper body muscles, in our case the deltoid and latissimus. For the same reasons as for the muscles of the lower part of body, that is, lack of normality and homogeneity of variance, as well as a small sample size, the Mann-Whitney U test was performed to verify the null hypothesis that the two random chosen samples come from the same population or, more precisely, from the population with