# Comparison of Countermovement and Preferred-Style Jump Biomechanics in Male Basketball Players
## 4 Discussion  
The purpose of this study was to investigate and compare the biomechanics of CMJ and preferred-style (Pref) jumps in a group of male collegiate basketball players. We hypothesized that (1) athletes would jump higher and exhibit greater joint-level kinetics using PrefJ than CMJ, and that (2) PrefJ than CMJ would only exhibit partial similarities between jump height and joint-level kinetics. The results of the current study supported our hypotheses in that jump height and joint-level kinetics were greater during the PrefJ than during the CMJ, and that only a limited number of joint-level variables were correlated between the two types of jumps. From a biomechanical perspective, the CMJ does not appear to reflect global maxima of either whole-body or joint-level neuromuscular capacity or represent athlete's preferred movement patterns during a more sport relevant jumping task. These findings may have practical implications for settings where the CMJ is used to assess and monitor maximal neuromuscular performance of basketball players. A major finding of the current study was that the PrefJ were characterized by greater jump heights and GRF, shorter ground contact times, smaller COM displacement during the lowering phase, and larger COM velocities than the CMJ. It is worthwhile to briefly consider these findings together with respect to the impulse-momentum theorem. The magnitude of mechanical impulse that is produced and applied to the COM during jumping tasks is directly related to the velocity and jump height of the COM [21]. Given that mechanical impulse is dependent on the magnitude of force and the duration of force application, differences in either of these variables can affect COM velocity and jump height. It is therefore interesting to note that even though the PrefJ exhibited smaller ground contact times and less COM displacement during the lowering phase, the substantially larger GRF during the PrefJ were enough to offset the shorter duration of force application and still produce significantly larger COM velocities and jump heights than during the CMJ [22]. Thus, compared to the CMJ, the biomechanics during the PrefJ are characterized by high-force and short-duration behavior. In addition to the differences in peak COM parameters identified by the pair-wise comparisons, the statistical analysis also showed that peak \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Lead Leg**} & \multicolumn{2}{c}{**Trail Leg**} \\ \cline{2-5}  & \(\mathbf{r}\) & \(\mathbf{p}\)**-Value** & \(\mathbf{r}\) & \(\mathbf{p}\)**-Value** \\ \hline Peak extension NJM & & & & \\ Hip & 0.232 & 0.581 & \(-\)0.155 & 0.715 \\ Knee & 0.363 & 0.376 & 0.531 & 0.175 \\ Ankle & 0.025 & 0.952 & \(-\)0.345 & 0.403 \\ \hline Peak positive NJP & & & & \\ Hip & \(-\)0.415 & 0.306 & 0.366 & 0.373 \\ Knee & 0.548 & 0.160 & 0.684 & 0.061 \\ Ankle & 0.920 & **0.001** & \(-\)0.162 & 0.702 \\ \hline Positive NJW & & & & \\ Hip & 0.067 & 0.875 & 0.318 & 0.443 \\ Knee & 0.541 & 0.166 & 0.613 & 0.106 \\ Ankle & 0.756 & **0.030** & 0.327 & 0.429 \\ \hline Negative NJW & & & & \\ Hip & 0.435 & 0.282 & \(-\)0.469 & 0.241 \\ Knee & 0.362 & 0.378 & \(-\)0.174 & 0.680 \\ Ankle & 0.640 & 0.087 & \(-\)0.127 & 0.764 \\ \hline \hline \end{tabular} Note: significant \(p\)-values are shown in **bold**. NJM—net joint moment; NJP—net joint power; NJW—net joint work.  
\end{table} 
Table 3: Correlations between joint-level biomechanical parameters of the countermovement jump and the lead and trail legs of the preferred-style jump. GRF, ground contact times, and COM velocities of the Pref] and CMJ were not strongly correlated. While the participants in the current study may have performed the CMJ with maximal intended effort, the lack of correlations between peak whole-body biomechanical parameters may suggest that the CMJ may only provide limited information about the type of jump a basketball player prefers to use when trying to maximize jumping performance, which is presumably more similar to in-game scenarios.