Is it that there is no development or simply their genetics dont cause their bi's to stand up? If they are moving big weights with strict form they have good bicep development its just their genetics hides that fact. I have decent sized arms, but they sure dont look like it(well not to me anyways). My bi's are very long and go solidly from elbow to shoulder so it appears i have a very flat arm. That doesnt mean I dont have decent bi's, its just my genetics dont make them as appealing as someone whose bi's attach further from the joint.