# Metabolomics Approach for Sweat Mapping the Performance of Soccer Players in Pretoria, South Africa
## 4 Discussion
It should be noted that niacin is an essential nutrient, meaning the body cannot produce it on its own and it must be obtained fromfood [29, 30], suggesting that the soccer players during-exercise mainly relied on niacin for energy supply, through food and dietary supplementation. This experiment found that the differential metabolites produced by sweat samples of soccer players post-exercise mainly included derivatives of pyroglutamate, meso-Erythiritol, Benzimidazo[2,1-a]isoquinoline, Glycerol, Methylmalonic acid, and several amino acids (L-Serine, L-Valine, L-Aspartic acid, L-Isoleucine, L-Alanine and L-Clutamic acid), among which the metabolism of Alanine, aspartate and glutamate, Valine, leucine and isoleucine, Pantothenate and CoA biosynthesis and Galactose metabolism suggest a close relationship between energy metabolism and fatigue. It is well known that the represented alanine, aspartate, and glutamate metabolic pathways play a significant role in amino acid and energy production [31]. During energy production, glucose is restored in the muscle during the conversion of alanine to pyruvate and the transferal between the liver and skeletal muscle satisfies the energy expenditure due to vigorous exercise [32]. Valine, leucine, and isoleucine, recognized as branched-chain amino acids, also play a significant role in energy homeostasis since they serve as energy substrates [33]. Moreover, Pantothenate (vitamin B5) is an essential component implied in the synthesis of coenzyme A (CoA), which is required for energy metabolism [34]. Galactose can be broken down and transformed into glucose then metabolized to produce ATP for energy delivery during muscular contraction [35]. Moreover, this study also highlights the potential of the approach used to successfully identify low-abundant metabolites, which are challenging to detect in other biofluids due to matrix effects, e.g., ephedrine (Table S1, Supplementary Materials), which warrant further studies. Currently, the detection of ephedrine is centered on the analysis of urine, with a set threshold of 10 \(\mathrm{\SIUnitSymbolMicro g}/\mathrm{mL}\)[36]. Sweat samples may be an appropriate and non-invasive approach for constant monitoring of ephedrine residues which may be utilized as soccer players' energy enhancers. This study also enlightens the fact that lipids are not the only metabolites altered after exercise, but also metabolites related to lipid metabolism, including niacin, which consists of lipid-lowering effects [18]. However, this investigation has certain limitations that warrant consideration. The limitation due to the small sample size and the lack of more diverse cohorts could affect the generalizability and reliability of the findings. The small sample size could reduce statistical power which can lead to false negatives, while the lack of diverse cohorts could limit the ability to generalize findings to different populations [37]. Thus, our study further highlights the need to consider larger and more diverse cohorts in future studies to improve the generalizability and validity of the findings for the enhancement of biomarker discovery. Moreover, after FDR correction was applied, most metabolite findings lost significance after adjustment. The non-significant findings after FDR correction provided valuable insights, but it still warrants further investigation.