i get the same thing when im doing heavy curls on a preacher bench. i just rub the area between sets and it helps out a little bit. one time i think i saw gloves online that actually hold the bar in place but i think thats mostly for pressing motions not just for keeping the bar in place, make sure your doing the movements right to (your placing the bar correctly and keeping your wrist in the proper area not bent back) or it could be maybe me and u are just to hardcore and the human body isnt designed for people like us jk