## 4 Discussion
In relation to Dm in our study, in BF, this decreased more in the EG than in the CG, which hardly changed (CG pre: 4.23 \(\pm\) 2.29 mm, post: 4.15 \(\pm\) 1.68 mm, and the EG pre: 5.35 \(\pm\) 1.79 mm, post: 4.79 \(\pm\) 1.91 mm). This can be interpreted as meaning that the individualised programme based on the TMG values improved the muscle tone of the bicep femoris, which is similar to the findings of the [PERSON] et al. [35] study with Brazilian football players (pre-test: 4.48 \(\pm\) 1.9 mm, post-test: 3.04 \(\pm\) 2.18 mm), in which the BF muscle tone also improved. Regarding ST, both groups, EG and CG, showed improved Dm, and therefore improved their muscle tone. However, the EG has a much greater improvement (CG pre: 7.80 \(\pm\) 2.11 mm, post: 5.88 \(\pm\) 2.28 mm, and the EG pre: 9.30 \(\pm\) 2.81 mm, 6.24 \(\pm\) 2.96 mm). Many of the exercises prescribed to the EG were aimed at this muscle, as the ST was the muscle with the worst values in the initial measurement. We have not found any studies that analyse pre and post by measuring the ST. In fact, there are few studies that measure the ST either in experimental or descriptive research, nor is this muscle usually measured in practice, which is very striking given its importance and its relationship with the BF. To date, there are two studies in which this muscle is measured at two different times of the season [37]. In a previous study by [PERSON] et al. (2022), the Dm of the ST worsened during the season, increasing in both the right and left leg (right leg 8.72 \(\pm\) 2.21 mm vs. 8.91 \(\pm\) 2.08 mm; left leg 8.41 \(\pm\) 2.21 mm vs. 10.09 \(\pm\) 2.95 mm), which means that as the season progressed, the muscle tone of the ST worsened [38]. The same outcome was observed in the study by [PERSON] et al. [37]. Although this was performed in futsal, the Dm of the ST also worsened during the season (9.7 \(\pm\) 2.0 mm vs. 10.6 \(\pm\) 2.0 mm). It seems that the ST is less activated than the BF during sprinting [39; 32], with especially less eccentric activation [40]. This seems to be the explanation for why, as the season progresses and the sprinting frequency increases, the ST data worsen, and the BF improves. Therefore, our study, which implements specific work to improve ST, is an interesting solution to prevent the worsening of ST per se during competition. With regard to the ST contraction time, this decreases in both groups and therefore improves explosiveness. However, the CG is the one that improved this variable more (CG pre: 48.27 \(\pm\) 6.65 ms, post: 30.42 \(\pm\) 10.39 ms, EG pre: 47.42 \(\pm\) 9.05 ms, post: 44.43 \(\pm\) 11.36 ms). This may be due to the age of the players, who are younger in the CG, as explosiveness is lost as we get older [41]. Age is strongly associated with a decline of physical capacities, and poorer sprint mechanical output values were observed among male players over 28 years old than for the other male age categories [42]. According to [PERSON] et al. [43], age-related sprint performance decline is mainly explained by the reduction in the size of fast fibres, and a lower maximum shortening velocity of type I myosin heavy-chain fibres. While mean peak performance in elite sprint specialists is achieved at 25-26 years of age [44], previous cross-sectional studies indicate that sprint capacities in football players peaks several years earlier [3; 45]. Regarding the 90\({}^{\circ}\) COD test, although there were no statistically significant differences, it was observed that the CG worsened its COD test values on both sides, and the EG maintained its results for the left side 90\({}^{\circ}\) COD test and improved the right side 90\({}^{\circ}\) COD test (left 90\({}^{\circ}\) COD CF pre: 2.25 \(\pm\) 0.08 s, post: 2.31 \(\pm\) 0.10 s, EG pre: 2.43 \(\pm\) 0.08 s, post: 2.43 \(\pm\) 0.08 s; right 90\({}^{\circ}\) COD CG pre: 2.30 \(\pm\) 0.11 s, post: 2.34 \(\pm\) 0.09 s, EG pre: 2.45 \(\pm\) 0.09 s, post 2.44 \(\pm\) 0.09 s).