Nice that’s a good amount to pull. I’m also curious how much of a factor heavier weight is as opposed to grip. I’ve known people to tear biceps on preacher curls (with light weight) and on a yoke carry. When its time to go it goes there’s not much that can be done to prevent it, from what I am told.
I can speak in regard to heavier weight, that the underhand grip in one hand and overhand grip in the other keeps the bar from wanting to roll out of one's hand like when only one grip is used.
There is a counter rotation effect on the bar with each hand having a differing grip, so based upon that a person theoretically could probably do a little more weight or more reps, since the feeling of the bar torquing/rolling/twisting in a under OR overhand grip, can make a person give into the weight because it feels like the bar is prying the hands open like a clam at a seafood restaurant.
As I approached the 500 pound mark and felt that tight pull on my biceps I said OH, NO!!!... the first thing I thought of was these WSM athletes who torn their biceps doing such movements as the ATLAS STONE (and this dead lift in this video) and did not want that to happen, so I went back to my overhand grip and straps and was fine.
So far as people tearing their biceps... or any muscle, at a relatively light weight.. I think that is due to neurological misfiring, where the neurotransmitter signal doesn't fire for enough muscle fibers at one time to engage and over-stresses those reacting fibers, which begin to tear across like Velcro, and rips across the muscle with a devastating end.
In the case of a tendon/ligament rupture I wonder if it is due to a nutritional/mineral deficiency due to all of the dieting/stress that over time results in weakened connective tissue?
I say that, because once these connective tissues begin tearing it seems that the tears continue all over the body like Dorian Yates, Branch Warren etc who eventually had to stop the heavy workouts because of the injuries.
More Collagen foods?, More Vitamin C, More rest? Less steroids?.... Not sure, but some investigations are needed.