Cool guys, yeh i knew about the lactic acid watever it is, but you get that when you train your legs even SLIGHTLY so mayb ebcause the arms are smaller u need to give it that extra shock sometimes, Normally guys my routine comprises of 6-10reps. i start on 10 and as i go heavier 8 then 6 but i wanted to get the shock to my BICEP, becuase Kllerduck, you have a point there.. but i think Muscles work by INTENSITY over TIME
Intensity x Time, your muscle doesnt know what its doing how long, it only feels the amount of stress over time

if you think of it that way, but yeh otherwise ive always been doing 6-8reps for heavier weights and 10 for medium weight