I've always rlx male felt it more than just doing curls standing up. Last but not the least are supersets and dropsets that help you to build big biceps. Supersets were very important for growing my biceps. I used to like to start with a heavy inward grip EZ bar preacher curl for 10 and then superset with a wide grip EZ bar curl for 20 reps with a lighter weight. By the way in case you're wondering what my workout structure for primal biceps grow pro was, I'll give it to you, but understand you may have to do something entirely different to stimulate your biceps.