Why Is My Chicken Breast Tough?First decide whether the meat is tough and dry or tough but still moist. Dry, fibrous chicken that cooked unevenly or spent too long at high internal temperature points to ordinary overcooking. Tough, rubbery chicken that is still moist — especially from a raw fillet that felt unusually hard, rigid or bulging — can point to woody breast myopathy, a quality defect that cooking technique does not create or fix. If the meat is actually mushy, spongy or falling into loose stringy bundles, that is a different myopathy called spaghetti meat, not overcooking. Do not keep lowering your cooking target to chase a texture problem that may have started before the chicken reached your kitchen; for home cooking, USDA FSIS recommends 165°F for poultry.