## 4 Discussion
This lack of BG response could be explained by the low-impact activity performed; in fact, during moderate-intensity exercise in healthy subjects (i.e., without diabetes), increased glucose uptake by muscles is balanced by an equal rise in hepatic glucose production, and blood glucose levels remain unchanged [21; 22]. Nonetheless, increased BG levels could be observed after longer padel matches since catecholamines stimulate glucose production only during moderate-intensity exercise greater than 2 h of duration [23]. On the other hand, TGs levels measured after padel matches showed a non-significant decrease in both female and male players but also in the total group. These results are similar to those previously described by [PERSON] et al. [9] and also seem to be consistent with the energy requirements of 80 min of moderate intensity exercise (e.g., padel match play) [24]. As it is well-known, during moderate intensity exercise roughly half of the energy is derived from fatty acids. However, to ensure the supply of fatty acids it is necessary that LPL hydrolyze TGs molecules. In our study, a significant increase in blood LPL concentration was found after padel matches, which could explain the TGs-lowering effect. On the other hand, it is generally accepted that widespread alterations in metabolite levels are known to occur when a biological system is in a dysregulated or exacerbated state (e.g., during exercise). Accordingly, changes in different metabolites induced by moderate or intense exercise regimes have been noted for many decades [25]. In our study, Cr and urea were assessed as energy-related metabolites. As expected, circulating Cr and urea levels significantly increased after padel matches in both male and female players (and also in the total group), although sex-related differences in both pre- and post-exercise were found. Previous studies have concluded that light to moderate exercise results in an increase in net protein catabolism and an increase in Cr [26]. Moreover, and considering that the origin of Cr from creatine, which is stored mainly in muscle tissue, it seems reasonable that male Cr concentrations were higher than those measured in female players [27]. Nevertheless, the increases in Cr observed after exercise were moderate, not exceeding the reference range established for healthy adults [28]. Blood urea concentrations measured in both male and female players showed significant increases after padel competition. These increases were also found in the total group which could be explained by an enhanced protein catabolism due to the energy requirements of padel match play. Very similar results were reported by [PERSON] et al. [9], who also observed sex-related differences in urea responses after padel competition. Although our results did not show such differences, pre- and post-exercise urea concentrations were slightly higher in males than in females. Nevertheless, it is important to note that pre-exercise blood urea levels found in our study were close to the upper limit of the reference values which is consistent with previous studies that showed high resting urea concentration because of the continual stress of training and sports competition [28]. Exercise-induced muscle damage is a well-documented phenomenon particularly resulting from vigorous exercise which results in muscle micro-injuries and, consequently, in a loss of muscle function due to overexertion. CK, an intracellular enzyme present in greatest amounts in skeletal muscle, is typically used as a marker of muscle damage [29]. In our study, blood CK levels showed a huge increase from pre- to post-exercise evaluation in male and female groups (also in the total group). However, sex-related differences were also found since circulating CK concentrations were higher in male than female players in both assessment time points. These results are in line with those reported from studies in which serum CK levels increased significantly after simulated padel competition and sex differences were also found [9].