## 4 Discussion
This indicates that in middle-distance and long-distance events lasting 2 min or more, jump height and the combination of force and velocity are not as determinant as other measurements like the rate of force development or reactive strength index. These measurements, which provide different information about force and power characteristics, have been found to be correlated to RE and time trial running tests [41; 42]. Regarding the data obtained on the optimal F-V profile, we did not find that the profile of one group is more optimized than the other, nor that the degree of imbalance from the optimal profile is related to performance. Although there are various studies showing that having an optimized F-V profile is strongly related to performance in jumping or sprinting [14], the value of this tool is also questioned [20]. One of the criticisms of [PERSON]'s model [43] is that it assumes the average velocity of the jump to be a constant derived from the take-off velocity divided by two. The amount of effective work produced during a lower limb extension depends less on the average velocity and more on the time-history of the velocity throughout the jump [44]. In any case, 69.23% of middle-distance athletes and 72% of long-distance athletes showed a strength deficit. The same is observed when looking at the proportion by sex; 65% of women and 72.2% of men, respectively, showed a force deficit. This would indicate that the population of athletes exhibits a force deficit and should undergo more strength training through high-load exercises. However, in our study, FVimb was not related to physiological determinants in endurance running performance such as RE or VO2 max. Therefore, the use of the F-V profile in long-distance runners does not seem to be very useful in improving the orientation of strength training in this population. It has been demonstrated that changes in biomechanical factors such as step frequency and step length affect RE, and therefore, overall running performance [45]. These biomechanical alterations are influenced by lower limb strength training. Stride length is highly individual, with each subject adapting their stride to achieve a more economical running style, often by reducing it [44]. However, in our study, we found a significant and moderate positive correlation between step length and Pmax and a large positive correlation with jump height (Table 3). Contrary to what might be expected, this correlation was stronger at lower speeds than at higher speeds, even though step length increases with speed. Understanding the F-V profile of an athlete is crucial to determining whether their sport demands more high-speed exercises, such as pylemetric training, or heavy-load exercises that target maximal strength. Coaches should assess this profile in their athletes to identify whether they exhibit a strength deficit or a velocity deficit, allowing them to tailor the training plan accordingly. Similarly, knowing which types of exercises are associated with physiological factors that directly impact performance helps coaches select the most effective exercises for strength training. However, there are some limitations in the present study that should be taken into consideration. Some of the participants were familiar with the squat-jump exercise, as they regularly included it in their strength training sessions. Nevertheless, this was not the case for all participants, as some, despite undergoing the familiarization session, did not exhibit the same ease in performing the exercise, which could influence the results. The sample size could be considered small, but it represents a very specific population of well-trained middle- and long-distance athletes (mean over 800 WA points and a VO2 max greater than 52 mL/kg/min in women and 64 mL/kg/min in men), in addition to including a similar number of men and women.