Has anyone done curls for the purpose of PLing and found that they helped on any lift? Personally, the only way that curling effected my results was that I could no longer fit into my bench shirt. But I see so many pl'ers doing them, I'm curious as to why.
I do hammer curls mostly to protect against the possibility of biceps tears during deadlifting. So curls are more for pre-hab in PL'ing.
That and leverage. The more mass under the bar, the better. I think it is better to bench off of car jacks than it is toothpicks. Thats about it.
The biceps are stabilizers in the BP as well. I add some form once a week.
My elbows used to ache like a motherfucker after shirt work and adding in some biceps work made it stop so I still do it.
As was alluded, the biceps are an important stabilizer of the elbow. As to whether specific bicep work is required... I'd rather see rows/chins used for the additional back development and weighted pronations/supinations used on off days or training periods focusing on foundational training.
Biceps are generally neglected by the big 3, for that reason alone I think it is useful to do them for better balance and to prevent injury/increase stability as others have said. But beyond that stronger bis usually leads to stronger lats and stronger lats can lead to a stronger bench, so in a "6 Degrees to Kevin Bacon" sort of way they are useful for PLing.
I find that doing heavy curls allow me to lower heavier weights during the bench. For the longest time I trained strictly Westside. As my bench reached the high 500's I couldn't bring the bar down under control. I do heavy straight bar curls once a month and it has helped enormously.
Hammmer curls are great for elbow pains, with thumbs on top they really help your grip on benching.(when trying to "pull the bar apart" - a la Louis Simons) Not so much on deadlifting. Regular biceps work ... like curls ... not so much useful in increasing your lifts ... essential for strongman events though.(cheat curling, curl grip cleans, etc)