## 4 Discussion
According to the data presented by [PERSON] and [PERSON] [4], during a 100-m race, an athlete draws 59% of energy from anaerobic sources (including 20% phosphagenic) and 41% from oxygen, while in the 200-m race, these proportions are almost the opposite--42% anaerobic (including 13% phosphagenic) and 58% aerobic. Of course, it should be emphasized that the above-mentioned data relate to the top-level competitors for whom the duration of these races is shorter. In the case of younger swimmers, representing a lower sports level, the duration of the 100- and 200-m races is longer, thus, the aerobic component contribution may be greater [5]. This does not change the fact that, with regard to the 200-m competition, the SAST does not seem to be a sufficient tool for diagnosing the body's training status. For this reason, for swimmers specialising in middle-distance swimming, tests aimed at assessing aerobic capacity and power should be sought. It should also be mentioned that the differences in the values ofkinematic indices from the 100- and 200-m freestyle races may also be the result of different swimming strategies employed in these events. The swimmers start the 100-m race at almost maximum speed, which results in a 12% longer time to cover the second half of the distance [25]. This strategy is referred to as 'positive splitting' [26]. In the case of the 200-m distance, the intensity of the effort during the first 50 m is lower, which means that the increase in the time of completing subsequent sections is only 6-8% [25]. At this distance, most of the competitors also use the 'positive splitting' strategy, although some prefer 'even splitting' of pace, in which the time to complete following sections is similar [26]. In this study, no significant differences were found for stroke index measured during the initial and final sections of the SAST as well as the 100- and 200-m freestyle races (\(\text{SI}_{\text{S}}\)\(\text{SI}_{\text{F}}\), respectively). It was also noticed that other test variables such as speed, stroke length, or stroke rate differed much more in relation to these two distances. This means that they are modified to a greater extent depending on the duration of the effort (100 m and 200 m). At the same time, an exceptionally strong correlation was observed between the stroke index in the initial and final repetitions of the SAST and their 100-m equivalents (\(r=0.92\) for both \(\text{SI}_{\text{S}}\) and \(\text{SI}_{\text{S}}\)) and the 200-m freestyle (\(r=0.89\) for \(\text{SI}_{\text{S}}\) and \(r=0.78\) for \(\text{SI}_{\text{S}}\)). This indicates that the stroke index, in its assumptions reflecting technical efficiency [27, 28], is characteristic of each athlete and is characterised by little variability depending on the conditions (e.g., distance length). This means that the stroke index indicators from the SAST can be used to assess the technical efficiency of athletes--both within the context of short and middle distances. Improving sports results in many disciplines is possible by increasing the ability to continue exercise despite extreme neuromuscular fatigue [28, 29]. Fatigue is associated with a decrease in the capacity to develop a force of an expected value [5], which in swimming, is mainly manifested by a reduction in speed during the final parts of a race [30, 31]. Some authors also note a decrease in stroke length with increasing fatigue [30, 31, 32]. Conclusions from research concerning the influence of fatigue on stroke rate are not unequivocal. [PERSON] et al. [30], [PERSON] et al. [33] and [PERSON] et al. [34] showed that in such conditions, stroke rate decreases; however, in other studies [31, 35], an increase in the value of this index has been noticed. The presented lack of clarity in the given sources may be the result of the selection of groups--in the research by [PERSON] et al. [30], the participants were world-class competitors, while [PERSON] et al. [30] made observations in a group of swimmers clearly representing a lower level (semi-competitive).