## 4 Discussion  
The objective of this study was to evaluate the effect of carbohydrate supplementation (glucose:fructose 1:2) on fatigue in young super-sprint triathletes. To achieve this, a double-blind, randomised trial was conducted, in which each athlete performed two super-sprint triathlons separated by 90 min of recovery in which they ingested 45 g of the product, as well as a 20 min regeneration protocol on a roller at 40-50% of VO2 max immediately after the first triathlon. Before discussing the results, it should be noted that for years, pre- and intra-exercise carbohydrate supplementation in endurance sports has been proven to be a reliable and safe tool for improving athletic performance [33]. Among the various strategies and dosing regimens for carbohydrate administration, 45 g/h has been reported to be an effective and safe amount for improving endurance [1]. In recent years, research in the field of sports nutrition has been investigating the effects of combined fructose and glucose intake compared to the intake of glucose or polymers derived from it alone [34]. In this regard, it has been proven that the combination of glucose and fructose during exercise can induce favourable responses in metabolism, substrate utilisation, and gastrointestinal symptoms [35]. Thus, the biochemical and nutritional characteristics of fructose, as well as its obligatory passage through the liver, seem to exert positive responses on the glycaemic response, which, in combination with glucose intake, can favour performance in endurance modalities [34]. It should also be considered that to maximise these nutritional properties, the typology, nature, and intensity of the sports modality play a key role, as the metabolism of carbohydrates during exercise is directly dependent on them. In the case of super-sprints, it is a modality that has a total duration of 25-35 min in well-trained athletes [36], with the men's world records being around 23 min. The men's events consist of 300 m of swimming, 8-10 km of cycling, and 2.5 km of running. Regarding supplementation, a total of 45 g was ingested in a single dose between both super-sprint trials. The 45 g had a 2:1 ratio of fructose to glucose, so each participant ingested a total of 30 g of fructose and 15 g of glucose. In this respect, the amount ingested by the participants is slightly lower than the amounts advised and reported in the literature [37,38] and, additionally, it was ingested in the post-recovery period after the first effort and not during athletes performance. In this study, the times recorded by the participants were similar to those reported in the literature (PG: 22.69 \(\pm\) 1.75 min; SG: 22.51 \(\pm\) 1.51), and no improvements were observed in the total times with carbohydrate supplementation either in the total time or in the time of the different segments or partials of the trial. These results were supported by the observations related to blood glucose, which was not affected by supplementation, although a slight positive trend was observed in blood glucose values in the SG (Figure 3). The only differences observed were in the RPE derived from the water segment, which increased after supplementation in the SG but without any effects on any other parameter evaluated. Considering that there were no effects on external load parameters, the increase in RPE could have been due to a greater accumulation of lactate because of the supplementation, as the duration of the segment in the SG was 3.58 \(\pm\) 0.29 min, coinciding with durations of effort with a greater involvement of anaerobic glycolytic processes. In this regard, it has been reported that the duration of the super-sprint modality is much shorter than that recorded in Olympic triathlons, with a significantly higher intensity where the anaerobic threshold is exceeded in some phases of the test involving anaerobic metabolism [36].