Obviously creatine isn't any form of doping. It's a supplement. All amateur bodybuilder's federations accept this specific (I'm not talking about pros like IFBB because they do tests only against diuretics). I ate few packets myself - it isn't any secret weapon or something... I'm sure all top rikishi use real stuff like our good old polish Omnadren, Metanabol or even Anapolon (Anadrol 50 equivalent). You can't regenerate quickly without steroids. Injuries are part of sumo... Enough said.