The ACE gene’s I/D polymorphism is one of the most replicated findings in sport genetics — separating endurance-optimized physiology (I allele) from power-optimized physiology (D allele) through cardiovascular architecture rather than fiber structure alone. The Precision Peptide Genetic Test analyzes ACE as one of 15 Muscle Growth insights across 14 pathways, 49 peptides, and 150+ genetic insights.