Curls are the classic gym bro exercise, and a bicep flex is the most iconic way to, literally, flex on someone. But does it ...

Senior Personal Trainer at Ultimate Performance ... "The long head is responsible for the muscle ‘peak’ when you flex your biceps – in other words, the ‘vanity muscle’ of your biceps!

It doesn’t matter whether you’re a weekend warrior, a die-hard gym bro, or a seasoned bodybuilder, every man and his dog ...