Il Nuovo Postiglione - Drug-fueled Enhanced Games begin in Las Vegas

Around 40 sprinters, swimmers and weightlifters are taking part. The majority have taken combinations of testosterone, human growth hormone, peptides, anabolic steroids and other substances banned by events like the Olympics.

The event has been denounced by athletics governing bodies and anti-doping agencies as dangerous and against the spirit of sport.

But participants, lured by prize money of up to $1 million for beating world records, will include Olympic medallist swimmers James Magnussen, Cody Miller and Ben Proud, who have all taken drugs.

Co-founder Max Martin has predicted "quite a few" world records will be "beaten," though the feats would not be officially recognized.

Weightlifter Beatriz Piron, who reportedly surpassed a world record in training, attempted to get the Games off with a bang with the same feat in the very first event -- but narrowly failed.

Swimmers will also be allowed to wear the types of "supersuits" that led to many world records falling around the 2008 Beijing Olympics, but were subsequently prohibited.

Chief sporting officer Rick Adams said that he respects that "specific international organizations" will not accept any records set on Sunday, even if they are broken by clean athletes like Kerley.

"But it is uncontroverted that if one of our 50m freestyle... moves through that water in less than 20.88 seconds, they have moved through that water faster than any other human being in history," he said, referring to Cam McEvoy's official record.

- 'Reasonably confident' -

The Enhanced Games are taking place at a purpose-built $50 million arena in a Las Vegas casino parking lot, a structure to be dismantled hours after the final race.

In a marriage of sports, biohacking, politics and entertainment, investors including billionaire Peter Thiel are rumored to be attending, while rock band The Killers will play a closing set. Donald Trump Jr is among the event's investors.

Health experts warn that several of the substances could risk "life-shortening and fatal consequences," including heart, liver and kidney issues, as so little is known about their long-term effects.

But Enhanced Games officials say all medications are approved by the US Food and Drug Administration, and no expense had been spared on hiring top medical experts.

Emergency officials will be standing by in case something goes wrong.

"I'm reasonably confident nothing will happen," said chief medical officer Guido Pieles.

Pieles described the risk of the medications as "clearly there" but "really manageable."

His team has published the percentage of athletes taking each substance, with Martin vowing that "transparency is core to our DNA."

Yet athletes said that they are not able to disclose the specific combinations each has taken.

"The reason for that is because actually it doesn't matter," Martin told AFP, noting that combinations are tailored to each athlete.

Also, parent company Enhanced -- which sells many of the substances being taken by its athletes to the public -- does not want to "advertise for certain protocols to create imitation potential," said Martin.

T.Cusumano--INP