Abstract

This thesis provides an in-depth exploration of skeletal muscle complexity, highlighting its remarkable plasticity and the precise regulation of muscle mass and function through metabolic and transcriptional mechanisms. It details the diversity of muscle fibers, both typological and metabolic, and presents key signaling pathways modulating protein synthesis and degradation, muscle regeneration via satellite cells, and the interplay between mechanical and biochemical factors. A special focus is placed on the transcription factor SIX1, which influences the specialization of fast glycolytic fibers and their metabolism, promoting the Warburg effect and intensive glycolysis. The thesis also covers muscle adaptations to different exercise types (endurance and resistance) and introduces innovative methodologies such as the FLASH technique for simultaneous contractile and metabolic fiber typing analysis. These findings provide a comprehensive framework to understand the molecular and functional determinants of muscle plasticity, with potential implications for managing muscle diseases and optimizing therapeutic and athletic interventions.