Guanidinopropionic Acid (GPA) is a creatine analog that has been primarily used in scientific research to study muscle metabolism and energy systems. GPA acts as a competitive inhibitor of creatine uptake, thereby lowering phosphocreatine availability in muscle cells. This decreased availability triggers compensatory metabolic adaptations, such as increased mitochondrial biogenesis and upregulation of AMP-activated protein kinase (AMPK) activity. Animal studies, especially in rodents, have demonstrated that GPA supplementation can induce adaptations in skeletal muscle similar to those seen with endurance training, including enhanced oxidative capacity and increased fatigue resistance (Oudman et al., 2013).

However, human data are lacking, and GPA is not used as a dietary supplement for muscle support in clinical or sports nutrition practice. Moreover, GPA may actually impair muscle strength and short-term performance due to its interference with the creatine-phosphocreatine energy shuttle, which is crucial for quick, high-intensity muscular contractions. Thus, while there is scientific interest in GPA for understanding muscle energetics, there is currently little evidence to support its use as a muscle-supporting supplement in humans. Its use remains confined to laboratory settings, and possible negative effects on muscle power limit its practical application.