## 4 Discussion  
The purpose of the present study was to examine differences in biomechanical parameters during aerobic-dominated swimming training sets performed either following a preceding sprint set or as the initial component of a training session. The findings indicated that swimming speed and biomechanical variables during the LT (8 \(\times\) 200 m) training set were similar between the sessions; however, notable alterations in SR and SL were observed during the MAS (8 \(\times\) 100 m) training set when it was implemented after repeated sprints. Additionally, BL was higher in the SPR-LT and SPR-MAS sessions compared to the LT and MAS sessions, respectively. Moreover, a relationship between BL and SR was observed in the SPR-LT session. Focusing on biomechanical parameters, the results indicate that SR increased while SL decreased in the SPR-MAS (8 \(\times\) 25 m and 8 \(\times\) 100 m) condition compared to the MAS (8 \(\times\) 100 m) condition. It is well established that implementing a sprint training set may result in the deterioration of biomechanical parameters [32], along with increased metabolic responses due to greater reliance on anaerobic metabolism [33]. Therefore, the recovery period of about 10 min, as implemented by the swimmers in the present study, may not be sufficient to fully restore physiological homeostasis before the next training set. This is supported by the higher BL observed at the start of the MAS set when it was preceded by a SPR set (see Table 1). This potential metabolic perturbation could affect swimmers' technique during subsequent training sets. Increased SR and decreased SL during swimming are associated with an increased energetic cost [34]. In our study, these changes occurred while the swimmers managed to maintain their SI during 8 \(\times\) 100 m in both conditions. In this case, the swimmers in the current study may have adjusted their underwater movement, allowing them to maintain an efficient arm stroke by applying less force (lower SL). In this scenario, the swimmers may adjust their coordination pattern to maintain speed during 8 \(\times\) 100 m [35]. However, the biomechanical parameters did not differ between the SPR-LT and LT sessions. Swimming intensity, rather than repetition distance, may be related to changes in biomechanical variables. Lactate threshold intensity represents the upper limit at which lactate production and removal are in equilibrium, reflecting a moderate ATP turnover primarily provided through aerobic metabolism [11]. Highly trained swimmers in this study (specializing in middle-distance events such as the 200 m race distance) may have developed aerobic capacity. Such an intensity (LT) can be achieved without modifications in SR and SL despite the higher BL observed at the start of the 8 \(\times\) 200 m when applied after repeated sprints. BL should not be considered a fatigue agent but rather as an energy substrate [36] that can be utilized by swimmers to maintain efficiency. A likely high aerobic capacity could enhance BL clearance, allowing the swimmers to perform well without needing to adjust their biomechanical parameters in the subsequent set. Indeed, during the LT set (8 \(\times\) 200 m), there was a downward trend in lactate, while during the MAS set (8 \(\times\) 100 m), it was maintained at high levels (higher than the LT set), indicating that LT corresponded to a tolerable intensity. However, in the MAS set, lactate levels remained high, suggesting a need for increased energy turnover and adjustments to biomechanical parameters to maintain performance. Moreover, a correlation between BL and SR was observed during the SPR-LT session. This positive relationship may reflect a higher effort of swimmers to maintain the required speed in the LT set during the SPR-LT session compared to the LT session.