A complementary amino acid formulation enhances exercise-induced skeletal muscle remodeling during resistance training

[Purpose] This study investigated whether a five-amino-acid formulation integrating complementary anabolic, metabolic, and redox-supporting functions enhances skeletal muscle remodeling during resistance training.[Methods] Male C57BL/6N mice were assigned to eight groups receiving vehicle, leucine (300 mg/kg), or amino acid formulation (150-1,500 mg/kg). All mice completed four weeks of ladder resistance training, while the assigned supplements were administered orally once daily. Muscle function, body composition, gastrocnemius fiber cross-sectional area (CSA), anabolic and metabolic signaling proteins, the muscular NAD+/NADH ratio, and circulating markers of muscle damage, inflammation, and glutathione status were assessed.[Results] The formulation improved grip strength at doses of 600-1,500 mg/kg and increased gastrocnemius fiber CSA at 1,200 and 1,500 mg/kg compared with vehicle (p < 0.05), without affecting body weight, food intake, body composition, or absolute muscle mass. It also enhanced AKT-related signaling and increased the expression of PGC-1α, citrate synthase, and UCP3. Several anabolic and mitochondrial protein responses exceeded those observed with leucine alone. The NAD+/NADH ratio increased at doses of 150, 900, and 1,200 mg/kg, with the greatest response observed at 900 mg/kg. The formulation reduced circulating TNF-α at a dose of 1,200 mg/kg, produced a dose-related decrease in CKM that approached statistical significance at 1,500 mg/kg, and most prominently increased total and reduced glutathione levels at 900 mg/kg.[Conclusion] The complementary amino acid formulation enhanced functional, structural, anabolic, metabolic, and redox adaptations during resistance training. These coordinated effects support its potential as a nutritional strategy for improving skeletal muscle quality during chronic resistance exercise.