## 4 Discussion  
The main purpose of this study was to compare the validity of the TOV method using a FP versus the FT method using a FP and a smartphone application to measure jumping performance or neuromuscular fatigue-overload in professional female soccer players. The major findings were the lack of reliability and validity between JH measured with the FP through the TOV and JH measured through the FT either by the FP (r = 0.028, \(p\) > 0.84, ICC = -0.026 (-0.276-0.24)) or the APP (r = 0.116, \(p\) > 0.43, ICC = -0.094 (-0.314-0.157)). To our knowledge, this is the first study that has researched the JH of SJ and CMJ together (SJ + CMJ) with these technologies: FP trough the TOV and trough FT, and APP through FT. Two previous studies [20; 31] have analyzed the SJ, CMJ and CMJ with arms (CMJA), together comparing JH with FP vs. contact mat (both through FT method) [20], and with FP (TOV and FT methods) vs. contact mat (FT method) [31]. This latter study [31] concluded that the TOV must be used instead of the FT as a more valid and accurate way to calculate the VJ performance. It provides a more sensitive approach to scientifically establishing jump determinants, greater sensitivity in analyzing changes in performance factors after training (i.e., overcompensation, overload), and greater accuracy in monitoring performance within the session (i.e., fatigue) [18; 19]. Further, the mean comparison shows a significant difference between the JH measured with the FP through the TOV versus the APP (\(p\) = 0.002), and a trend versus the FP through the FT (\(p\) = 0.052). To our knowledge, there is only one previous study that researched the differences between the FP through the TOV versus a smartphone application (FT method) [19], and it showed near perfect correlations (ICC = 0.996; \(p\) < 0.001). These differences with our results may be explain by some reasons: 1) In our study the subjects performed three different CMJs and SJs, while in the previous study the subjects performed five CMJs [19]; (2) The distance between the researcher and the subject was of 1 m in the previous study [19], while in our study it was of 1.5 m; (3) In addition, rest \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Mean \(\pm\) SD** & **Mean \(\pm\) SD** & \(p\) **Value** \\ \hline FP-TOV & 35.21 \(\pm\) 4.22 & FP–FT & 33.36 \(\pm\) 3.48 & 0.052 \\ FP–TOV & 35.21 \(\pm\) 4.22 & APP & 32.43 \(\pm\) 3.77 & 0.002 * \\ FP–FT & 33.36 \(\pm\) 3.48 & APP & 32.43 \(\pm\) 3.77 & 0.457 \\ \hline \hline \end{tabular} Data are presented as mean \(\pm\) standard deviation. FP–TOV: Force Platform–Take-Off Velocity; FP–FT: Force Platform–Flight Time; APP: My Jump Application (flight time). * Significant difference.  
\end{table} 
Table 1: Values of the different methods for measuring jump height combining CMJ and SJ. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Mean \(\pm\) SD** & **Mean \(\pm\) SD** & \(p\) **Value** \\ \hline FP–TOV & 37.23 \(\pm\) 4.68 & FP–FT & 31.53 \(\pm\) 3.09 & 0.000 * \\ FP–TOV & 37.23 \(\pm\) 4.68 & APP & 30.89 \(\pm\) 3.33 & 0.000 * \\ FP–FT & 31.53 \(\pm\) 3.09 & APP & 30.89 \(\pm\) 3.33 & 0.826 \\ \hline \hline \end{tabular} Data are presented as mean \(\pm\) standard deviation. FP–TOV: Force Platform–Take-Off Velocity; FP–FT: Force Platform–Flight Time; APP: My Jump Application (flight time); SJ: squat jump. * Significant difference.  
\end{table} 
Table 2: Values of the different methods for measuring SJ jump height. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Mean \(\pm\) SD** & **Mean \(\pm\) SD** & \(p\) **Value** \\ \hline FP–TOV & 33.18 \(\pm\) 2.44 & FP–FT & 35.19 \(\pm\) 2.87 & 0.060 \\ FP–TOV & 33.18 \(\pm\) 2.44 & APP & 33.96 \(\pm\) 3.60 & 0.644 \\ FP–FT & 35.19 \(\pm\) 2.87 & APP & 33.96 \(\pm\) 3.60 & 0.336 \\ \hline \hline \end{tabular} Data are presented as mean \(\pm\) standard deviation. FP–TOV: Force Platform–Take-Off Velocity; FP–FT: Force Platform–Flight Time; APP: My Jump Application (flight time); CMJ; countermovement jump.  
\end{table}