Hrmm guess you can scratch my last post.
"He broke a branch and formed a sword with it and pondered, “The heavy iron sword is around seventy jin in weight, there are only two possibilities on how to overcome it with such a light and fragile wooden sword. One is through ingenuity of the sword strokes, using speed to overcome the slow; the other is through overbearing internal energy, using strength to subdue the weak.”
Yang Guo just chose to go the second route, but failed. Maybe he should have went the first way.