Olympic cyclists put themselves in near-death situation — study

“If you don’t have enough oxygen in your blood, you produce lactic acid and their blood acid levels, or their Ph, drops to levels that would have intensive care specialists running about thinking the person is going to die.”

He said in a hospital situation, specialists would bring their best to reverse the condition urgently “because you can’t live for more than a few hours at that level”.

Norton said the biochemical changes observed were highly unusual in a healthy person.

“It’s not a lasting problem but it’s a big physiological and biochemical change that occurs for a few minutes,” he said.

“They’re pushing themselves to the limits, to what in other situations would be extremely dangerous changes.

“Under any circumstances in hospital that would be life threatening.”

Other studies had found similar changes in elite triathletes, he added.

“What’s really occurring is that when you reach the elite levels like these athletes, the muscles are so highly tuned, their heart and circulation is so well developed, that the last thing that limits their performance other than psychology and motivation is the lungs and the ability to breathe.”

Norton said the only way to reverse the changes would be for a cyclist to use oxygen during a race which was illegal.