Nearly everyone at my gym (and every other gym I've ever been to) who does preacher curls goes from the top of the motion to halfway down and then back up. Now, the angle of a preacher curl bench makes it so the bottom half of the motion is difficult. In fact, at the top of the movement when your forearms are perpendicular to the ground, it requires absolutely no biceps involvement to keep them there because of the structure of your upper arms and the bench. So why do people only do the easiest part of the movement? Is it like people who do 1/4 squats so they can use more weight? And the other thing that pisses me off is that all these people have bigger arms than me, but yet I do my preacher curls with a full ROM (and pullups, too; I even posted a vid on that one). This brings me to another thread I'm going to start when I get time to discuss why every single person I've seen with big muscles has shitty form and doesn't use a full ROM.