Aging is associated with progressive declines in skeletal muscle mass, strength, and mitochondrial function, contributing to sarcopenia and physical frailty. Increasing evidence suggests that the gut microbiota may influence musculoskeletal aging through its regulation of metabolic homeostasis, inflammation, and anabolic signaling. The gut–muscle–mitochondria axis has emerged as a conceptual framework linking microbial-derived metabolites to skeletal muscle physiology and cellular energy metabolism. Within this framework, microbial metabolites such as short chain fatty acids may influence muscle protein turnover, mitochondrial biogenesis, and systemic metabolic regulation. Exercise, the most effective intervention for preserving muscle function in older adults, has been shown to modulate gut microbiota composition, enhancing short-chain fatty acid production and promoting mitochondrial adaptations. Exercise-induced shifts in microbial diversity may also support anti-inflammatory pathways and improve gut barrier integrity. These mechanisms may contribute to improved insulin sensitivity, anabolic signaling, and muscle metabolic efficiency, thereby supporting muscle maintenance during aging. Despite promising mechanistic insights, most available evidence derives from animal or observational studies, and causal relationships in humans remain to be established. Further longitudinal and interventional research is required to clarify the clinical relevance of microbiota modulation as a complementary strategy for promoting healthy musculoskeletal aging and preventing age-related functional decline.