Muscle hypertrophy relies on efficient protein synthesis, modulated by amino acid availability and signalling pathways such as mTOR, which activate muscle growth at a cellular level (Kimball et al., 2002). This study investigates the role of essential amino acids, particularly leucine and branched-chain amino acids (BCAAs), in promoting protein synthesis during resistance training. Using stable isotope labelling and molecular assays, protein synthesis rates were analysed in muscle biopsies post-intervention (Atherton & Smith, 2012). mTOR and associated pathways (e.g., S6K1) were assessed via Western blotting and RT-qPCR to quantify pathway activation (Drummond et al., 2009). Findings show a direct relationship between amino acid levels and increased anabolic signalling, providing data-driven insights into molecular responses essential for muscle adaptation (Phillips et al., 2005). This research underscores targeted amino acid supplementation as a potential strategy to enhance hypertrophic outcomes in resistance training (Tipton et al., 2001).