The gut microbiome influences endurance sports through multiple biochemical and signaling pathways that affect energy availability, inflammation, and recovery. Emerging evidence links metabolites produced by gut bacteria — notably short-chain fatty acids (SCFAs), lactate-derived propionate, and microbially mediated amino acid and bile acid metabolism — to physiological processes relevant for prolonged exercise. SCFAs such as acetate, propionate and butyrate arise from the fermentation of dietary fibers and serve local and systemic roles. Locally, butyrate is a primary fuel for colonocytes and supports gut barrier integrity; systemically, SCFAs can modulate inflammation and influence substrate utilization. For endurance athletes, improved mitochondrial efficiency and lower exercise-induced inflammation associated with SCFA production may support sustained performance and faster recovery. Specific taxa also appear to interact directly with exercise metabolites. For example, Veillonella species metabolize lactate into propionate; studies observing increased Veillonella abundance after prolonged runs hypothesize that this conversion helps clear lactate and provides an additional energetic substrate. While promising, these findings are preliminary and require replication across larger, mechanistic studies before generalizing to training recommendations. Gut microbes also contribute to amino acid turnover and synthesis, including branched-chain amino acids (BCAAs) that are important for muscle protein synthesis and energy metabolism during prolonged exertion. Meanwhile, microbial modification of bile acids can alter lipid absorption and serve as signaling molecules that affect metabolic and inflammatory pathways relevant to endurance. Quantifying the exact magnitude of microbiome effects on performance is challenging. Individual variability in microbial composition, diet, training status, genetics, and environment all interact, and interventional trials with well-controlled designs are still limited. Nonetheless, mechanistic links—SCFA production, lactate metabolism, amino acid and bile acid pathways—provide plausible routes by which the microbiome can modulate stamina, fatigue resistance, and recovery kinetics. Practical, evidence-informed strategies to support a resilient microbiome include dietary diversity with fiber-rich whole foods and fermented items, targeted use of prebiotics and probiotics where evidence supports strain-specific benefits, and maintenance of regular training, sleep, and stress-management practices that collectively stabilize microbial communities. For deeper context on large-scale research efforts and foundational concepts, see the EU Nutriome project summary: EU Nutriome project: transforming health, and a primer on gut microbiota fundamentals: What is gut microbiota and why it matters. For those considering assessment options, commercial microbiome testing is available as a tool to explore microbial composition: InnerBuddies microbiome test. This discussion synthesizes current understanding without overstating effects: microbiome pathways plausibly contribute to endurance physiology, but individual responses vary and more targeted human trials are needed. For a focused review and application to endurance athletes, consult the InnerBuddies overview: [Gut Microbiome & Endurance Sports: The Hidden Key to Stamina, Recovery & Peak Performance](https://www.innerbuddies.com/blogs/gut-health/gut-microbiome-endurance-sports-the-hidden-key-to-stamina-recovery-peak-performance).