The growth of poultry production has led to an increase in the incidence of internal defects in chicken and turkey broilers, such as Deep Pectoral Myopathy (DPM). DPM is an ischemic hemorrhage or necrosis caused by the inadequate blood supply of Pectoralis minor and major muscles. Currently, visual appearance is the only parameter used to categorize the damage level. The aim of this research was to develop a scientific methodology to determine the level of damage in poultry breast tenders affected by this myopathy. For this purpose, microstructure, pH, protein and ion contents, and color were studied. Results allowed identifying three damage levels: normal, hemorrhagic samples with hematomas and blood clots, and necrotic tissues, based on significant variables (p <.05) measured in Pectoralis minor (pH, L* and a*), where muscles with myopathy presented L* values lower than 47, and necrotic muscles presented pH values higher than 6.05. Practical applications: The appearance of defects in chicken meat is a growing problem due to the intensive genetic selection and the fast growth rate that the poultry industry demands. This research provides a scientific methodology, based on biochemical and physicochemical parameters of muscle tissue metabolism, and develops and validates a categorization for deep pectoral myopathy in broilers based on the level of muscle damage. This work, provides an objective and scientific methodology, and coupled with the work published in Traffano-Schiffo et al. (2018) and patented, will allow detecting, identifying, and characterizing chickens that have suffered deep pectoral myopathy and the degree of damage.