Originally Posted by
Brandon Mccaghren
As a beginner you learn the rules. Always do this. Never do this. To borrow from Josh Waitzkin in The Art Of Learning we "learn form."
As your knowledge, experience, timing, and most importantly your sensitivity develops you begin to understand that there are gray areas, and that perhaps "never" and "always" were simply learning tools placed there to help you develop. We "learn form to leave form." I have instructed my 5 year old daughter to "never cross the road by herself." That doesn't mean that it's wrong for her to cross the road or that one day she won't be able to cross the road all by herself. But for now, it's something I don't want her to branch out into.
It is "safer" and easier to begin your understanding of arm bars with the legs crossed. As you develop and mature as a grappler, you will find moments when it is not only acceptable to uncross your legs, but more efficient and technically superior.