lots of people seem to have forearm pain doing straight bar curls, and the instant tip is to switch to the ezcurl.
but some people either do not have an ezcurl, or simply want to hit the biceps while fully supinated.
a trick to avoid forearm pain, when you are finished your set, don't simply drop the bar and have your wrists slingshot back from a tight supination, set the bar down with your forearms tight in the position, then ease your hands off the bar, still with tight supination, then slowly pronate your forearms.
it takes 3 extra seconds but i am experiencing no pain whatsoever.
try this tip it might help some people, but not everyone