Juiced-up athletes kicked off the first-ever Enhanced Games on Sunday in Las Vegas, where competitors are allowed to use performance-enhancing drugs.Around 40 sprinters, swimmers and weight lifters took part in the event which has sparked health concerns.The majority have taken combinations of testosterone, human growth hormone, peptides, anabolic steroids and other substances banned by events like the Olympics.Swimmers are also allowed to wear the types of 'supersuits' that led to many world records falling around the 2008 Beijing Olympics, but were subsequently prohibited. 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, included Olympic medalist swimmers James Magnussen, Cody Miller and Ben Proud, who have all taken drugs.Although co-founder Max Martin predicted 'quite a few' world records will be 'beaten,' only one was surpassed.The only athlete to win the $1 million bonus for going faster than the world record was Kristian Gkolomeev from Greece, who closed the night by swimming the 50-meter free in 20.81 seconds. Maximilian Martin, Co-Founder & CEO or Enhanced Games (L) and Kristian Gkolomeev (R), winner of the men's 50m free, are seen during the Enhanced Games Not all athletes at the event are opting to dope, however, with US sprinter Fred Kerley (pictured), who publicly vowed to compete clean, running 100 meters in a modest 9.97 seconds Among those who made runs at world marks was Ben Proud, the British Olympic silver medalist, who finished .05 off the 50-meter fly mark of 22.27The 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.Billionaire Peter Thiel and Donald Trump Jr. are amongst the investors of the event, which is a marriage of sports, biohacking, politics and entertainment.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. He 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 said, 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.Not all athletes at the event are opting to dope, however, with US sprinter Fred Kerley, who publicly vowed to compete clean, running 100 meters in a modest 9.97 seconds to secure a victory at the inaugural Enhanced Games. The chaotic race saw the sprinters placed in the starting blocks four times because of false starts and untied shoes.Kerley, who predicted Usain Bolt's world record of 9.58 seconds would get 'destroyed,' ran a time that would have placed him last at the Paris Olympics two years ago, where he ran 9.81 and won bronze.However, he still pocketed $250,000 - the first-place prize for all the events. Jasmine Abrams, Shania Collins, Tristan Evelyn, Shockoria Wallace, Taylor Anderson and Denae McFarlane compete during the Enhanced Games The Enhanced Games are taking place at a purpose-built $50 million arena in a Las Vegas casino parking lot The event is not open to the public, with a carefully curated crowd of about 2,500 people invited to attend Beatriz Piron reportedly surpassed a world record in training, but narrowly failed the same feat in the very first eventMost athletes are making money they could only dream of in mainstream Olympic sports. The real stakes, however, could be for the investors in the company that brought the world the Enhanced Games with the idea of turning it into a new-age online pharmacy that peddles performance enhancers under medical supervision.'It's just the beginning,' CEO Max Martin said in front of a specially curated crowd of around 2,500.Among those who made runs at world marks was Ben Proud, the British Olympic silver medalist, who finished .05 off the 50-meter fly mark of 22.27.'I think I am,' he said when asked if he was happy after winning $250K. 'But I think we all know what we came here for, and that's a world record.'Others included weightlifter Beatriz Piron, who reportedly surpassed a world record in training, but narrowly failed the same feat in the very first event.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.