## 3 Results  
The accuracy results--mean radial error--of each of the training groups--usual, specific, and induced variability--are shown in Table 3 and Figure 2. The values recorded in the pre-test, post-test, and re-test are included.  
The accuracy data presented through the median, as well as the dispersion data, represented by the standard error and the difference between the maximum and minimum accuracy, reflected by the range, are included in Table 3. It can be observed that the usual training group obtained values of 206.63 cm in the pre-test, 95.58 cm in the post-test, and 180.09 cm in the re-test. In this same group, the dispersion data regarding the achieved accuracy, represented through the standard error, reflect values of 11.45 cm in the pre-test, 7.00 cm in the post-test, and 13.98 cm in the re-test. Regarding the differences between the  
Figure 1: Experimental setup.  
maximum and minimum values achieved in accuracy, the ranges show values of 116.44 cm in the pre-test, 72.69 cm in the post-test, and 125.30 cm in the re-test.  
The specific training group obtained median values of 231.54 cm in the pre-test, 97.92 cm in the post-test, and 2236.44 cm in the re-test. In this same group, the standard error data reflect dispersion values of 16.15 cm in the pre-test, 7.06 cm in the post-test, and 13.76 cm in the re-test. The differences between the maximum and minimum accuracy  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & **Usual** & **Specific** & **Variability** \\ \hline \multirow{4}{*}{**Radial Error**} & Mean & 206.97 & 230.77 & 232.94 \\  & Standard deviation & 36.21 & 48.45 & 30.69 \\  & Median & 203.63 & 231.54 & 235.76 \\
**Pre-test** & Variance & 1311.03 & 2347.14 & 942.13 \\  & Standard error & 11.45 & 16.15 & 9.71 \\  & Range & 116.44 & 161.50 & 95.15 \\  & \(N\) & 10 & 9 & 10 \\ \hline \multirow{4}{*}{**Radial Error**} & Mean & 100.42 & 98.18 & 165.75 \\  & Standard deviation & 22.14 & 22.34 & 111.42 \\  & Median & 95.58 & 97.92 & 110.22 \\  & Variance & 490.20 & 498.93 & 12414.71 \\
**Post-test** & Standard error & 7.00 & 7.06 & 35.23 \\  & Range & 72.69 & 68.02 & 316.12 \\  & \(N\) & 10 & 10 & 10 \\ \hline \multirow{4}{*}{**Radial Error**} & Mean & 201.85 & 241.69 & 192.60 \\  & Standard deviation & 44.22 & 43.50 & 46.23 \\
**Radial Error** & Median & 180.09 & 236.44 & 180.46 \\  & Variance & 1955.62 & 1892.41 & 2137.61 \\
**Re-test** & Standard error & 13.98 & 13.76 & 14.62 \\  & Range & 125.30 & 120.63 & 133.15 \\  & \(N\) & 10 & 10 & 10 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Descriptive values (cm) by groups and practice schedules.  
Figure 2: Evolution of the accuracy achieved by the players in each practice condition from the pre-test to the retention test. The bars show the standard deviation. * \(p\) = 0.041; \(ES\) = 0.51; significant differences between the specificity and variability groups in the retention test can be seen.  
values show ranges of 161.50 cm in the pre-test, 68.02 cm in the post-test, and 120.63 cm in the re-test.  
The training group, through induced variability, obtained median values of 235.76 cm in the pre-test, 110.22 cm in the post-test, and 180.46 cm in the re-test. In this same group, standard error values reflect dispersion values of 9.71 cm in the pre-test, 35.23 cm in the post-test, and 14.62 cm in the re-test. Regarding the differences between the maximum and minimum accuracy values achieved, the ranges show values of 95.15 cm in the pre-test, 316.12 cm in the post-test, and 133.15 cm in the re-test.  
As reflected, participation was maintained in the three groups in the tests developed (\(N=10\)). Only the experimental 'dropout' of one of the tennis players from the specific practice group was noted, who could not perform the pre-test (\(N=9\)). However, this player continued participating in subsequent training and tests (Table 3).