Guys i think the thing you have to think about with forearms, those muscles are designed to be able to cope with constant pressure applied on them, becuase any hand movement will use the forearms in one way or the other, i play myself the Accordion and ive been doing that waybefore ive started training 1yr ago, playing the Accordion 10yrs, and that gave me monster forearms just from playing it, and NO i was never sore the next day, but while practising you can get the forearm to BURN like no tomorow, and i think that is what develops it. Not post soreness with the forearms specifically