I know every muscle is key for BJJ but are there key ones? I've heard so many different opinions. Helio said his forearms is his key. An arguement can be true towards Eddie's 10th planet camp and BJ Penn that it's all about flexiable legs. I've also heard about the major importance of your core ab muscles. I'm trying to be a well rounded @ 175 or 150lb. I gotta work on my legs more Rubber guard no-gi looks amazing. Plus I gotta work on HIIT. I'm gassing way too fast.