That last one you could actually see when the tendon/muscle snap.
Yes, that one convinced me.
It usually occurs when the athlete bends the underhand arm (unintentionally) ever so slightly at either the start of the pull or on putting the final rep down.
But that last one, the arm looks to be straight.
So I'm going double-overhand today.
WSM - these guys are still using alternate grip
Oli Thompson - his biceps look normal at this years WSM, will look more closely.
Your SHOCK-TACTIC worked IRONSLAVE
As a former powerlifter i'd have to disagree I've seen men dead 800 lbs. using the alt. grip style. It is actually very safe however like all excersises it has form to it.
Many people in a attempt to get the weight up with unknowingly curl it an inch or two up using their bicep. You have to train to completely relax your biceps during the deadlifting period.
In fact during early training in powerlifting and powersports deadlifting take about a month to teach properly and years to master. But alt. grip is an safe as hang clings or clean and jerks but they can be dangerous if you don't know wtf you are doing.