## 4 Discussion  
The aim of the present study was to investigate the relationship between the mechanical parameters of the Hzt FV profile, obtained from sprint running, and the COD performance in professional soccer players from different categories. As expected in the initial hypothesis, the main findings from this work showed that higher levels of F\({}_{0}\) and P\({}_{\max}\) were directly related to better performance in the M505 test, while higher levels of V\({}_{0}\) were associated with superior performance in the 505 test. Therefore, the results obtained in this study using horizontal component variables to evaluate force levels are consistent with those obtained in previous studies that used vertical component variables, supporting the suggestion that stronger and more powerful soccer players (i.e., higher F\({}_{0}\) and P\({}_{\max}\), respectively) showed higher CODD [5; 27; 32]. Given the characteristics of the 505 test, which includes a 10-m linear sprint before the start of the timed section (5 m), the player spends most of the time running linearly (69%) and a smaller part of the time changing direction (31%) [17; 18]. However, the M505 test is focused exclusively on the ability to accelerate and change direction consecutively over a very short distance (5 m) [16; 36]. As the results show (Figure 1), depending on force application demands in each test, it can be noted that in a context where there is a prior entry velocity (as in the 505 test), V\({}_{0}\) becomes more important, due to the need to apply force at high velocity. As hypothesized, the mechanical parameters of the Hzt FV profile were related to the performance in COD during the 505 test and M505 test. More specifically, F\({}_{0}\) showed a large inverse relationship with the M505 test [Professional (r\({}_{\mathrm{s}}=-0.468\), \(p<0.05\)); Amateurs (r\({}_{\mathrm{s}}=-0.690\), \(p<0.01\)); U18 DH (r\({}_{\mathrm{s}}=-0.642\), \(p<0.01\)); U18 LN (r\({}_{\mathrm{s}}=-0.658\), \(p<0.01\))] due to the higher need to apply horizontal force in this test [16; 35] when starting from a stationary position, while V0 showed a large inverse relationship [Professional (r\({}_{\mathrm{s}}=-0.682\), \(p<0.01\)); Amateurs (r\({}_{\mathrm{s}}=-0.721\), \(p<0.01\)); U18 DH (r\({}_{\mathrm{s}}=-0.736\), \(p<0.01\)); U18 LN (r\({}_{\mathrm{s}}=-0.569\), \(p<0.01\))] with the 505 test, where the subject starts the test with a previous speed (different from 0) acquired over an approach distance of 10 m, as the predominant force application demands change from horizontal to vertical force production [30]. The obtained results are in accordance with previous studies, such as that of [PERSON] et al. [17], in which a strong relationship was shown between the performance in the 505 test and 10-m sprint time (as a measure of acceleration) and 30-m sprint time (as a measure of maximum speed). In this case, acceleration (F\({}_{0}\)) and maximum speed (V\({}_{0}\)) variables were obtained directly from sprints through the Hzt FV profile parameters instead of using performance times in linear sprint as representations of acceleration and maximum speed capacities [17; 18; 25]. For this reason, in accordance with [PERSON] et al. [29; 32], the mechanical parameters of the Hzt FV profile could contribute to better understanding of these relationships by directly analyzing the influence of acceleration (F\({}_{0}\)) and maximum velocity (V\({}_{0}\)) on COD performance. It is widely known that P\({}_{\max}\) is a highly influential variable in sprint performance [37]. In this case, P\({}_{\max}\) had a good relationship with performance in both tests (as shown in Figure 1) because this variable takes into consideration the better relationship from both F\({}_{0}\) and V\({}_{0}\)[38]. However, while for the M505 test the variable with the highest relationship was P\({}_{\max}\) (due to the need to generate high amounts of force and velocity over a very short distance), for the 505 test, the variable with the greatest relationship was V\({}_{0}\).