Try running a Google search. There has been some academically sound discussion on this subject on various forums, along with a lot of more-or-less wild-eyed speculation and outright fantasy/fraud.
The existence of NA wrestling sports is pretty well documented and it's very likely that various tribes did develop close-combat weapon skills to a high level, but records seem to be very sparse as to how they went about it (training, etc.) The consensus seems to be that NA cultures probably didn't support the highly codified or ritualized type of training that you see in many Asian and European cultures. Training was more likely something that was integrated into daily life, starting out with sparring games etc. as kids, gradually refining combat skills over years of informal practice.
If these skills have survived to the present day, they've been kept very well hidden.