The practice of rugby league players inhaling an artificial oxygen mixture to help overcome injury could be banned by the end of the year.
Three Wests Tigers players, Keith Galloway, skipper Robbie Farah and veteran prop John Skandalis , were seen using the aids at training yesterday.
The Sydney Morning Herald says although the practice is not banned by the Australian Sports Anti-Doping Authority, the World Anti-Doping Agency's code says "artificially enhancing the uptake, transport or delivery of oxygen is banned".
An NRL spokesman says the technique - known as hypo-oxygenation - involves diluting the amount of oxygen, which he believes is not covered by the rules.
The spokesman says world anti-doping rules apply to increasing oxygen, not decreasing it, although there could be changes next year.