Steer anatomy and cuts of beef. The shoulder, arm, and leg do most of the work of supporting the animal. They therefore contain a large proportion of reinforcing connective tissue, are tough, and best cooked thoroughly for an hour or more to dissolve the connective-tissue collagen into gelatin. The rib, short loin, and sirloin do less work, are generally the tenderest cuts, and are tender even when cooked briefly to a medium doneness.