The color spectrum of noble gas Xenon in a gas discharge tube. Photo: Wikipedia, Alchemist-hp (talk) (www.pse-mendelejew.de)
The Economist in detail:
Xenon works its magic by activating production of a protein called Hif-1 alpha. This acts as a transcription factor: a chemical switch that turns on production of a variety of other proteins, one of which is EPO. Artificially raising levels of EPO, by injecting synthetic versions of the hormone or by taking so-called Hif stabilisers (drugs that discourage the breakdown of Hif-1 alpha), is illegal under the rules of the World Anti-Doping Agency (WADA). Other methods of boosting the hormone, however, are permissible—and that fact has not gone unnoticed by the Russian sports authorities. Athletes are allowed to live or train at altitude, or sleep in a low-oxygen tent, in order to stimulate red-cell production. If xenon treatment is merely replicating low-oxygen environments by replacing oxygen with xenon, then its use to enhance athletic performance is permissible.The use of xenon by athletes certainly has government blessing. A document produced in 2010 by the State Research Institute of the Ministry of Defence sets out guidelines for the administration of the gas to athletes. It advises using it before competitions to correct listlessness and sleep disruption, and afterwards to improve physical recovery. The recommended dose is a 50:50 mixture of xenon and oxygen, inhaled for a few minutes, ideally before going to bed. The gas’s action, the manual states, continues for 48-72 hours, so repeating every few days is a good idea. And for last-minute jitters, a quick hit an hour before the starting gun can help. [...]
And the gas appears to have been used in past Olympics. The website of Atom Medical Centre, a Russian medical-xenon producer, cites national honours the company received for its efforts in preparing athletes for the 2004 summer Olympics and the 2006 winter games.
Update 25. FEB 2014: Journalist Jens Weinreich uploaded some of the original documents and some numbers of past Olympic games.