Well I'd honestly say GSP is more of a wrestler at this point who uses more of a boxing approach than a kyokushinkai approach for his striking these days. Machida uses Shotokan as his primary approach. Jon Jones uses boxing. Josh Barnett is a Catch Wrestler (yeah yeah I know submission wrestling is submission wrestling and more differences are individual style choices, there are some differences though from typical no-gi BJJ and he was trained by the likes of Billy Robinson, Antonio Inoki, Funaki, Erik Paulson and others who had Catch wreestling/Shooto roots). Fedor uses Sambo.
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Member of DaJoGen MMA school under Dave Hagen and Team Chaos fight team under Denver Mangiyatan and Chris Toquero, ran out of Zanshin Martial Arts in Salem Oregon: http://www.zanshinarts.org/Home.aspx,