But tenderness is not guaranteed by price. There will be tough meat cuts in every grade. Tough meat cannot be recognised by eye when you are buying at the supermarket. Many lean carcasses that testing has showed were tender have received lower grades because that don't have enough visible fat marbling to be classified as 'USDA choice' or higher. And yet marbling is a very poor predictor of tenderness .
Scientists measure the force needed to shear muscles.
The more force needed, the tougher the meat is. This is known as the 'Warner-Bratzler shear force test'. It's units of measurement are kilograms of force needed to shear a 1 cubic centimeter muscle sample. Obviously, the 'best cuts' are the most tender. But even meat that should have been tender can be made tough by stress just prior to slaughter.