## 3 Results  
### Functional Profile Distribution in Youth Soccer Players  
Thirty-seven male youth soccer players (mean age 13.3 \(\pm\) 1.6 years; full demographics in Table S1) were classified into four functional profiles using the expert rule-based system (Figure 1; Table 1); 8 players (21.6%) were categorized as _Functionally Weak_, 5 (13.5%) as _Strength-Deficient_, 6 (16.2%) as _Stability-Deficient_, and 18 (48.6%) as having _No Clear Dysfunction_. All _Functionally Weak_ players had FMS scores \(\leq\) 14, whereas the other groups had higher scores (median = 17, range = 15-21). The _Strength-Deficient_ group exhibited the lowest mean normalized strength values (0.45 \(\pm\) 0.03% BW), and the _Stability-Deficient_ group showed the lowest YBT performance (84.34 \(\pm\) 0.61). Athletes classified as _No Clear Dysfunction_ had superior results across most metrics, with strength (0.59 \(\pm\) 0.12), YBT (89.63 \(\pm\) 5.11), and FMS scores (18.00 \(\pm\) 1.97) exceeding those of all deficit groups. Flag categorization revealed 1 Red flag case (2.7%, 3 deficits), 8 Yellow (21.6%, 2 deficits), and 28 Green (75.7%, 0-1 deficit). A comparative radar plot of all functional profile groups is presented in Figure 2.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Profile** & **Strength** & **YBT** & **FMS** & **Flags** \\  & **(Z-Score)** & **(Z-Score)** & **(Category)** & **Flags** \\ \hline Functionally Weak & & & & \\ (\(n\) = 8) & & & & \\  & 0.56 \(\pm\) 0.09 & 88.96 \(\pm\) 4.28 & 13.38 \(\pm\) 0.74 & R = 0 \\  & (\(-\)0.15 \(\pm\) 0.79) & (\(-\)0.04 \(\pm\) 0.91) & (Low) & G = 4 \\ Strength-Deficient & & & & \\ (\(n\) = 5) & & & & \\  & 0.45 \(\pm\) 0.03 & 93.45 \(\pm\) 1.09 & 16.40 \(\pm\) 1.14 & R = 0 \\  & (\(-\)1.13 \(\pm\) 0.24) & (0.92 \(\pm\) 0.23) & (Medium) & Y = 1 \\ Stability-Deficient & & & & \\ (\(n\) = 6) & & & & \\  & 0.65 \(\pm\) 0.08 & 84.34 \(\pm\) 0.61 & 18.67 \(\pm\) 1.03 & R = 0 \\  & (0.66 \(\pm\) 0.67) & (\(-\)1.02 \(\pm\) 0.13) & (Medium) & Y = 0 \\ No clear dysfunction & & & & G = 6 \\ (\(n\) = 18) & & & & \\  & 0.59 \(\pm\) 0.12 & 89.63 \(\pm\) 5.11 & 18.00 \(\pm\) 1.97 & R = 1 \\  & (0.16 \(\pm\) 1.10) & (0.10 \(\pm\) 1.09) & (Medium) & Y = 3 \\  & & & & G = 14 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Performance metrics and flag distribution across functional profiles.  
Statistical comparisons confirmed that the profiles differed significantly in the domain defining variables. Kruskal-Wallis tests were significant for FMS (H = 21.4, \(\eta^{2}\) = 0.56, \(p\) < 0.0001), strength (H = 10.8, \(\eta^{2}\) = 0.24, \(p\) = 0.012), and YBT (H = 12.9, \(\eta^{2}\) = 0.30 \(p\) = 0.0049) across the four profiles. Bonferroni-adjusted post hoc Dunn tests (Figure 3) revealed that Functionally Weak players had significantly lower FMS scores than some other groups (\(p\) < 0.0001 vs. no-dysfunction; \(p\) = 0.001 vs. Stability-Deficient) but no vs. the Strength-Deficient group (\(p\) = 0.345). Strength-Deficient players had lower strength values than no-dysfunction players (\(p\) = 0.044) and Stability-Deficient players (\(p\) = 0.011) but did not differ in YBT scores from them (\(p\) = 0.481). Conversely, the Stability-Deficient group did not have a significantly lower YBT than the no-dysfunction (\(p\) = 0.065) and Functionally Weak (\(p\) = 0.267) groups, but this metric was different than that in the Strength-Deficient group (\(p\) = 0.002). The Bonferroni-adjusted Dunn test heatmaps with \(p\)-values for strength, Y-Balance, and FMS across functional profiles are presented Figure S1.  
Figure 2: Radar plot comparing motor test results across functional profiles.  
No statistically significant differences were found between clinical profiles in BMI (\(p\) = 0.280). Chronological age showed a near-significant trend (\(p\) = 0.061), with \"Stability-Deficient\" athletes being younger (12.1 years) and \"Strength-Deficient\" being the oldest (14.8 years).