## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Variables** & **B** & \(\mathbf{SE}\) & **Beta** & **T** & **Sig** & **Lower** & **Upper** \\ \hline \begin{tabular}{c} Fascicle \\ length \\ ILP-PF \\ Thickness \\ \end{tabular} & 76.654 & 76.987 & 0.204 & 0.996 & 0.335 & \(-\)87.349 & 240.748 \\ \begin{tabular}{c} ILP-PF \\ 460.320 \\ \end{tabular} & 0.121 & 0.061 & 0.389 & 1.993 & 0.065 & \(-\)0.008 & 0.250 \\ \begin{tabular}{c} Thickness \\ \end{tabular} & 460.320 & 260.931 & 0.354 & 1.764 & 0.098 & \(-\)95.841 & 1016.481 \\ \hline \
\begin{tabular}{c} ILP-PF \\ Thickness \\ \end{tabular} & 0.141 & 0.774 & 0.454 & 2.475 & 0.025 & 0.20 & 0.263 \\
\begin{tabular}{c} Thickness \\ \end{tabular} & 564.804 & 238.836 & 0.434 & 2.365 & 0.031 & 58.495 & 1071.112 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Results of the stepwise regression analysis using ILP-PF, fascicle length and muscle thickness as predictors of CMJ power. cicle length in female athletes. Along this line, it was also found that ILP-PF and muscle thickness were important predictors of CMJ power in female athletes. The results of this study also indicated that VL muscle thickness was associated with CMJ height. In line with this result, [PERSON] et al. (2015) also identified strong associations between VL thickness and jump height in elite male surfers (43) and [PERSON] et al. (2009) reported significant correlations between VL thickness and CMJ height in males and females (47). Although, some previous studies failed to detect associations between VL muscle morphology and jumping height (50,51), the results of this study are in line with the findings of a recent meta-analysis on the association between CMJ height and VL muscle thickness (52). Fascicle length was significantly associated with all the ILP-RFD epochs (0-50, 0-100, 0-150, 0-200 and 0-250 ms), in the absence of associations with VL pennation angle and thickness. Although performance of rapid contractions is determined by neural and muscular factors (34) the relative contribution of muscle structure in the early or late RFD is poorly understood. In agreement with the results of the present study, [PERSON] et al. (2020) reported a significant association between VL fascicle length and RFD epochs (100-250 ms) in knee extension (90\({}^{\circ}\)) in males (8). The correlations between VL fascicle length and RFD epochs found in this study may be associated with the intention of the individuals to produce force rapidly. Such a focus may increase the rate of muscle activation by the central nervous system, thus, leading to faster muscular force production for which fascicle length is an important determinant (25). This association between fascicle length and RFD epochs may have direct relevance to sport activities in female athletes. Interestingly, the association between VL muscle thickness and fascicle length and isometric RFD has also been confirmed in previous studies in youth physically active and clinical population (53). However, no correlation was observed between fascicle length and any of the RFD epochs in CMJ. A possible explanation of this result is that RFD during CMJ is assessed in the eccentric (braking) phase where the body drops into the squat position. During this eccentric phase a lengthening of muscles (54) is observed, and elastic energy is stored in the passive elements of the muscles involved, possibly modifying the role of contractile elements in force production (55). In contrast, RFD in ILP is evaluated from the start of a forceful isometric contraction. Furthermore, contribution of different muscle groups may differ between jumping and ILP performance, with VL playing a more important role in force production during isometric exercise (56). Interestingly, no association was found in this study between RFD epochs and pennation angle.