Goosey
.
I have no doubt it works the arms, just don't understand why people sway towards a close underhand grip to target the biceps rather than a wide overhand grip. Is it because the exercise is a lot more difficult to perform?
Place your arms beside you as if you're typeing on your computer Palms down
with one hand, feel your bicep.
now, suppinate the hand and then feel the bicep.
tell me what you note.