Admittedly, I am not the person to come to for expert advice on curls.
But I was reading this article on Art of Manliness about curls..
Here at AoM, we’re big proponents of doing strength exercises that give you the most bang for your buck. That means we advocate for compound barbell lifts that allow you to work the most muscles possible, lift the most amount of weight, and get all-around strong. We’re talking deadlifts, squats...
www.artofmanliness.com
...and it had this picture....
So when you're curling in (your own) squat rack, is the bar supposed to come all the way up to your eyes?
Because I can't go that high without getting my delts involved, too.
The text says:
"Bringing the bar to eye level will ensure you
also work the top part of the bicep near your shoulder."
Something smells anatomically / biomechanically incorrect about this -- I thought the bicep only had 2 (bi) head, short and long heads, not top and bottom heads.