## 4 Discussion  
The aim of this study was to conduct an updated parallel analysis of endurance freestyle swimming events of different durations to inquire whether decision-making on pacing strategy in swimming is dependent on the length of the competition despite their  
Figure 5: Splits times of swimmers performing at 100–105% (**a**) and 105–112% (**b**) of world records. *: \(p<0.05\) for the difference between 800 and 1500 m swimming. comparable energy properties. To this purpose, all the elite and junior 2022-2023 world championships finalists in the 1500 and 800 m freestyle competitions were analysed as a whole and differed by sex, age, and performance level. To assess the performance level, the final time of each athlete was calculated as a percentage of the respective record time so that swimmers were divided as lower level, those closest to their record time (100-105% of WR), and higher level, those farther from their record time (105-112% of WR). The key findings of the study highlighted that the swimmers taken into consideration in the study did not match or break the corresponding world record in either the 800 or 1500 m races of any of the world championships. In both the 800 or 1500 m competitions, swimmers followed the parabolic U-shaped pace but presented significant differences between the two distances in terms of the frequency and duration of speed changes. The number of sequences maintaining an acceleration of the same sign occurred significantly more frequently, and the maximal length of sequences resulted significantly longer in the 800 than in the 1500 m for all groups of swimmers. All the 1500 m competitions were characterised by \"true\" time series, while the 800 m competitions presented at least one swimmer that did not uphold a time series for the whole competition. The difference between sexes showed that females significantly lowered their normalised velocity in the central part of the competition in both distances with respect to males. In the 800 m competition, females presented a significantly faster start and males a faster end spurt. Swimmers who reached better performances tended to maintain more constant speeds with smoother pacing patterns. Performance Level and Records--No significant differences were found in the performance level with respect to world records between the two distances except for males, elite, and 100-105% swimmers that reached times significantly closer to the respective records in the 1500 m than in the 800 m competition. The swimmers did not equate or overtake the respective world records in the 800 m and 1500 m competitions of all world championships considered in the study. All final times resulted within 101% and 112% of world records. It appears that the level of swimmers' performances notably decreased. Pacing Strategy--Swimmers included in the present study followed the well-established parabolic U-shaped pace for the 800 and 1500 m freestyle competitions. Their coefficient of variation in velocity (CV%) along the race presented no significant differences between the two distances. However, there were significant differences between the two distances in terms of the frequency and duration of speed changes. Sequence Analysis--The number of sequences holding an acceleration of the same negative or positive sign (Sequences Number%) occurred significantly more frequently in the 800 than in the 1500 m competitions for swimmers of all sex, age, and performance level. Also, the maximal length of sequences representing a positive or a negative variation of speed (Maximal length of sequences%) were significantly longer in the 800 m competitions for the whole group of swimmers and for the junior, medallists, and 105-112% groups. This suggests that shorter races involve more frequent adjustments in speed. Time Series Analysis--All the 1500 m competitions represented \"true\" time series as given by the value 1.