## 3 Results  
### Identification of Key Parameters  
The analysis of kinematic parameters on flat terrain, as detailed in Table 2, revealed that both the cycle length and the vertical displacement of the CoM during the poling phase had a more significant impact on skiing speed compared to angular kinematics. Furthermore, gender was identified as a major determinant affecting skiing speed, underscoring its substantial influence on performance. The results of the importance analysis of kinematic parameters on uphill terrain are presented in Table 3. Similar to flat terrain, cycle length and vertical displacement of the CoM during the poling phase were major contributors to skiing speed. Moreover, the influence of gender on skiing speed was found to be more pronounced on uphill terrain compared to flat terrain. Building on the initial findings, a deeper examination of parameter significance was conducted using random forest analysis, as detailed in Table 4. Among kinematic factors, cycle length and the vertical displacement of the CoM during the poling phase were reaffirmed as pivotal influences on skiing speed. Regarding physiological parameters, those related to metabolic capabilities--like VO\({}_{2}\)max and 30 s anaerobic capacity--alongside measures of physical fitness, such as performance in the standing long jump and pull-ups, were identified as having considerable effects on skiing speed. Interestingly, the \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Parameter** & **Relative Importance** \\ \hline Angular kinematic parameters & ROM of elbow extension during the poling phase & \textless{}0.01 \\  & ROM of elbow flexion during the poling phase & \textless{}0.01 \\  & ROM of hip extension during the swing phase & \textless{}0.019 \\  & ROM of hip flexion during the swing phase & \textless{}0.012 \\  & ROM of knee extension during the swing phase & \textless{}0.01 \\  & ROM of knee flexion during the poling phase & \textless{}0.01 \\  & ROM of forward flexion of the trunk during the swing phase & \textless{}0.022 \\  & ROM of forward flexion of the trunk during the poling phase & \textless{}0.035 \\  & ROM of pole inclination during the poling phase & \textless{}0.01 \\  & ROM of pole inclination during the swing phase & \textless{}0.01 \\  & Mean angular velocity of elbow flexion during the poling phase & \textless{}0.022 \\  & Mean angular velocity of elbow extension during the poling phase & \textless{}0.055 \\  & Mean angular velocity of hip flexion during the poling phase & \textless{}0.01 \\  & Mean angular velocity of knee flexion during the poling phase & \textless{}0.01 \\  & Mean angular velocity of knee flexion during the swing phase & \textless{}0.01 \\  & Mean angular velocity of knee flexion during the swing phase & \textless{}0.01 \\  & Cycle length & \textless{}0.175 \\  & Cycle rate & \textless{}0.01 \\ Kinematics of the CoM & Vertical displacement during the poling phase & \textless{}0.386 \\  & Vertical displacement during the swing phase & \textless{}0.01 \\ Categorical variables & Sex & 0.268 \\ \hline  & ROM, range of motion. & \\ \end{tabular}
\end{table} 
Table 2: The relative importance of kinematic parameters for skiing speed on flat terrain.