## 3 Results
### CART Model
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Variables** & **Total** & **ITBS+** & **ITBS\(-\)** & **Mean Difference** & & \\
**(N = 60)** & **(N = 30)** & **(N = 30)** & **(95\% CI)** & & \\ \hline \hline \multicolumn{1}{c}{Ground Reaction Force} & & & & \\ Impulses, & & & & & \\ BW*s & & & & & \\ Vertical & 0.36 (0.02) & 0.36 (0.01) & 0.36 (0.02) & 0 (\(-\)0.009 to 0.013) & 0.836 & - \\ Anterior & 0.015 (0.002) & 0.014 (0.002) & 0.015 (0.001) & \(-\)0.001 (\(-\)0.001 to 0.001) & 0.303 & 0.50 \\ Posterior & 0.017 (0.002) & 0.016 (0.002) & 0.017 (0.002) & \(-\)0.001 (\(-\)0.002 to \(-\)0.001) & 0.049 * & 0.50 \\ Medial & 0.009 (0.004) & 0.009 (0.004) & 0.009 (0.003) & 0 (\(-\)0.002 to 0.002) & 0.858 & - \\ Lateral & 0.002 (0.001) & 0.002 (0.002) & 0.001 (0.001) & 0.001 (\(-\)0.001 to 0.001) & 0.086 & 0.63 \\ Instantaneous Loading Rates & & & & & & \\ Peaks, BW/s & & & & & \\ Vertical & 67.78 (21.72) & 70.35 (19.35) & 65.20 (23.91) & 5.15 (\(-\)6.08 to 16.39) & 0.363 & 0.20 \\ Posterior & 9.81 (3.27) & 9.51 (2.95) & 10.11 (3.59) & \(-\)0.60 (\(-\)2.29 to 1.10) & 0.359 & 0.18 \\ Medial & 7.86 (3.64) & 7.59 (3.37) & 8.12 (3.93) & \(-\)0.53 (\(-\)2.42 to 1.36) & 0.756 & 0.14 \\ Lateral & 8.24 (4.20) & 8.34 (3.76) & 8.14 (4.66) & 0.20 (\(-\)1.98 to 2.39) & 0.564 & 0.05 \\ Ground Reaction Force Peaks, & & & & & \\ BW & & & & & \\ Vertical & 2.26 (0.20) & 2.25 (0.21) & 2.27 (0.20) & \(-\)0.02 (\(-\)0.13 to 0.08) & 0.658 & 0.10 \\ Anterior & 0.19 (0.03) & 0.19 (0.04) & 0.20 (0.03) & \(-\)0.01 (\(-\)0.02 to 0.01) & 0.627 & 0.28 \\ Posterior & 0.25 (0.05) & 0.24 (0.05) & 0.26 (0.05) & \(-\)0.02 (\(-\)0.04 to 0.01) & 0.168 & 0.40 \\ Medial & 0.09 (0.03) & 0.09 (0.02) & 0.10 (0.03) & \(-\)0.01 (\had a higher chance of being in the ITBS group (node 3: risk profile--proportion of participants with ITBS = 100%; proportion of participants without ITBS = 0%). In runners with AGRFI higher than 0.012 BW*s, the AGRFP entered the model with 0.22 BW as the cut-off. Those with PGRFI less than or equal to 0.019 BW*s, AGRFI higher than 0.012 BW*s, and AGRFP higher than 0.22 BW had a higher chance of being in the ITBS group (node 6: risk profile--proportion of participants with ITBS = 84.6%; proportion of participants without ITBS = 15.4%). In runners with AGRFP less than or equal to 0.22 BW, the VSIL entered the model with 76.97 kN/m as the cut-off. Those with PGRFI less than or equal to 0.019 BW*s, AGRFI higher than 0.012 BW*s, AGRFP less than or equal to 0.22 BW, and VSIL less than or equal to 76.97 kN/m had a lower chance of being in the ITBS group (node 7: protective profile--proportion of participants with ITBS = 16.7%; proportion of participants without ITBS = 83.3%), while those with VSIL higher than 76.97 kN/m had a higher chance of being in the ITBS group (node 8: risk profile--proportion of participants with ITBS = 66.7%; proportion of participants without ITBS = 33.3%) (Figure 1). The resulting model, using PGRFI, AGRFI, AGRFP, and VSIL cut-offs to define nodes, correctly classified 25 runners with ITBS and 25 runners without ITBS, with a total correct classification of 83.3%. The area under the ROC curve (accuracy) was 0.87 (95% CI, 0.77-0.96; SE, 0.04; \(p<0.001\)) (Figure 2). Table 3 shows the risk (nodes 3, 6, and 8) or protective (nodes 2 and 7) profiles with their respective prevalence ratios and confidence intervals. A statistically different proportion of runners with and without ITBS were found for nodes 2, 6, and 7 (\(p<0.05\)). Figure 1: Classification and regression tree model for liiotibial band syndrome. ITBS, liiotibial band syndrome; PGRFI, posterior ground reaction force impulse; AGRFI, anterior ground reaction force impulse; AGRFP, anterior ground reaction force peak; VSIL, vertical stiffness at initial loading. Classification profiles for runners with ITBS. Node 3: PGRFI <= 0.019 BW*s, AGRFI <= 0.012 BW*s. Node 6: PGRFI <= 0.019 BW*s, AGRFI > 0.012 BW*s, AGRFP > 0.22 BW. Node 8: PGRFI <= 0.019 BW*s, AGRFI > 0.012 BW*s, AGRFP <= 0.22 BW, VSIL > 76.97 kN/m.