## 4 Discussion
### Experimental Results
Based on inverse dynamics, taking the propulsive force generated by the swimmers, their swimming velocity, and their FSA variation, it was possible to calculate the \(\mathrm{C_{Da}}\) in each section. Overall, it can be stated that the increase in swimming velocity between sections (although not significant) may be related to the increase in propulsive force concurrently with the decrease observed in the dv and \(\mathrm{C_{Da}}\). Hierarchical linear modeling was used to identify the determinants of swimming velocity. As male and female swimmers were tested together and repeated measurements were performed, the effects of gender and time were tested, respectively. Gender and time revealed a non-significant effect. This indicates that men and women can be grouped together to identify the determinants of swimming velocity. Moreover, a significant time effect for the swimming velocity test was not identified. This indicates that swimming velocity did not change significantly between sections (as previously tested). Thus, it can be stated that recreational swimmers do not have a profile similar to high-level swimmers, where a significant decrease in swimming velocity is observed between sections in a maximal trial or sprinting event [23]. The final model revealed SL, \(\mathrm{F_{mean\_right}}\), \(\mathrm{F_{mean\_left}}\), and \(\mathrm{C_{Da}}\) as significant determinants of swimming velocity. Regarding SL, current data indicate that swimmers who were able to cover a greater distance per stroke are more likely to achieve faster swimming velocities, which is a well-known fact in swimming [14; 20]. Regarding propulsive force, theoretical models based on numerical studies indicated that greater levels of propulsive force led to faster swimming velocities [46; 47]. More recently, experimental studies have demonstrated this phenomenon, finding that higher values of propulsive force led to faster swimming velocities [16; 17]. Here, it could even be argued that a greater propulsive force might also allow for a larger SL and, hence, a faster swimming velocity. Indeed, it has been argued that propulsive force may play a key role in the SF-SL interaction to increase swimming velocity [18]. The \(\mathrm{C_{Da}}\) was also kept as a significant determinant of swimming velocity. The literature is committed to showing that hydrodynamics plays a fundamental role in the swimmers' performance, where swimmers who present smaller values are more likely to present better performances [13; 48]. In the past, due to equipment constraints, it was more difficult to measure propulsive force directly and, hence, test it as a determinant of swimming velocity. The data of the current study indicates that swimming velocity was determined by the interaction of kinematics (SL) and kinetics (propulsive force and \(\mathrm{C_{Da}}\), i.e., hydrodynamics). This is in line with the literature, which highlights swimming as a holistic phenomenon. Notwithstanding, it should be mentioned that swimmers can achieve faster swimming velocities by generating propulsive forces while reducing resistive forces [12]. These findings reveal that both propulsion and \(\mathrm{C_{Da}}\) are significant determinants of swimming velocity. Recently, it has been reported that swimmers can experience misalignments when producing propulsive force, which will lead them to have a larger FSA area and, therefore, a greater resistive force [27]. Consequently, they can be under a higher resistive force immediately after they generate propulsive force, promoting a decrease in their swimming velocity. Therefore, it can be suggested that there is no point in generating greater levels of propulsive force if immediately afterward one does not adopt a position that is as hydrodynamic as possible, i.e., decreases the water resistance.