## 4 Discussion
In addition, we provide new quantitative data describing the influence of familiarization during RFD assessment [9], with some variables reaching sufficient reliability since the first session and the others requiring just a single previous session (Table 2). Of final note is that important inter-limb asymmetries were identified, with non-dominant limbs describing lower records and larger variations during rapid force assessment. Although these differences could be anticipated [30], it seems to be the first time presenting data about asymmetries and RFD performance during a ballistic knee extension test in athletes. According to our findings, this test would allow to identify severe asymmetries >15% but requiring a previous familiarization. All in all, given that improvements in RFD can be expected within the first \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Test-Retest**} & \multicolumn{4}{c}{**Dominant Leg**} & \multicolumn{4}{c}{**Non-Dominant Leg**} \\ \cline{2-11}  & **CV** & **SEM** & **ICC** & **\%Diff** & **\(p\)** & **ES** & **CV** & **SEM** & **ICC** & **\%Diff** & \(p\)** & **ES** \\ \hline
**Raw** & & & & & & & & & & & & \\ MVC (_N_) & 5.7\% & 38.0 & 0.948 & +2.5\% & 0.290 & 0.14 & 5.4\% & 33.4 & 0.939 & +2.7\% & 0.248 & 0.17 \\ Impulse\({}_{0-10}\) (_N_+) & 19.7\% & 1.8 & 0.801 & +1.1\% & 0.882 & 0.03 & 24.1\% & 1.9 & 0.713 & -19.6\% & 0.075 & 0.50 \\ Impulse\({}_{0-150}\) (_N_+) & 100.5 & 5.4 & 0.988 & -0.6\% & 0.981 & 0.02 & 14.1\% & 5.9 & 0.958 & -5.6\% & 0.154 & 0.26 \\ Impulse\({}_{0-250}\) (_N_+) & 9.2\% & 10.0 & 0.904 & -0.1\% & 0.941 & 0.24 & 7.5\% & 0.929 & -3.5\% & 0.265 & 0.17 \\ RFD\({}_{0-10}\) (_N_+1_) & 15.6\% & 86.8 & 0.848 & -1.1\% & 0.870 & 0.04 & 23.7\% & 1184 & 0.72\% & -7.6\% & 0.497 & 0.19 \\ RFD\({}_{0-150}\) (_N_+1_) & 8.7\% & 283 & 0.914 & -0.1\% & 0.980 & 0.01 & 10.4\% & 31.3\% & 0.840 & +2.9\% & 0.530 & 0.14 \\ RFD\({}_{2-30}\) (_N_+1_) & 7.3\% & 16.9\% & 0.983 & -0.5\% & 0.918 & 0.24 & 5.7\% & 120 & 0.920 & -11.0 & 0.982 & 0.01 \\ RFD\({}_{0-15}\) (_N_+1_) & 17.2\% & 134 & 0.799 & -0.8\% & 0.918 & 0.03 & 22.0\% & 1668 & 0.212 & +14.5\% & 0.095 & 0.67 \\ \hline
**Fitted** & & & & & & & & & & & & \\ MVC (_N_) & 6.1\% & 40.0 & 0.938 & +2.4\% & 0.306 & 0.13 & 5.0\% & 30.2 & 0.947 & +2.5\% & 0.261 & 0.15 \\ Impulse\({}_{0-50}\) (_N_+1_) & 133.3 & 1.2 & 0.901 & -0.5\% & 0.932 & 0.02 & 17.1\% & 1.4 & 0.810 & -16.4\% & 0.00 & 0.49 \\ Impulse\({}_{0-150}\) (_N_+1_) & 15.5\% & 5.6 & 0.900 & -0.4\% & 0.937 & 0.01 & 10.5\% & 0.53 & 0.53 & -7.0\% & 0.146 & 0.28 \\ Impulse\({}_{0-250}\) (_N_+1_) & 9.1\% & 10.1 & 0.904 & -0.3\% & 0.942 & 0.01 & 7.5\% & 7.7 & 0.925 & -3.5\% & 0.311 & 0.16 \\ RFD\({}_{0-10}\) (_N_+1_) & 12.4\% & 77.8 & 0.988 & -0.6\% & 0.960 & 0.02 & 14.8\% & 84.8\% & 0.823 & -10.5\% & 0.115 & 0.38 \\ RFD\({}_{0-150}\) (_N_+1_) & 8.9\% & 31.3 & 0.907 & -0.4\% & 0.932 & 0.02 & 6.9\% & 218 & 0.900 & -2.6\% & 0.411 & 0.21 \\ RFD\({}_{0-150}\) (_N_+1_) & 7.1\% & 173 & 0.930 & +0.3\% & 0.925 & 0.01 & 4.8\% & 102 & 0.967 & -0.1\% & 0.958 & 0.01 \\ RFD\({}_{0-150}\) (_N_+1_) & 16.9\% & 154.8 & 0.891 & -0.2\% & 0.975 & 0.01 & 22.9\% & 1864 & 0.727 & -17.3\% & 0.106 & 0.45 \\ \hline \hline \end{tabular} SEM: standard error of measurement, CV: SEM expressed as a coefficient of variation, ICC: intraclass correlation coefficient, Diff: percentage of change between the average records of each session, \(p\)-value: \(t\)-test significance, ES: Hedge\({}^{\circ}\)s \(g\) effect size.  
\end{table} 
Table 3: Test-retest reliability (values of the highest trial conducted in Sessions 1 and 2) in maximal voluntary contraction force (MVC), rate of force development (RFD) and impulse variables for original (raw) and filtered (fitted) data. weeks of training [6], and the benefits of a previous familiarization, it is advisable to evaluate the rapid isometric contraction of the knee extensors since initial stages of the season and conducted frequent monitoring to verify short-term progresses.