A sports expert has warned that with the rise in serious injuries and even deaths from fitness fanatics pushing themselves too far, they should have to qualify for ultra endurance events such as the London Marathon.
According to Professor Greg Whyte, who trained Little Britain comedian David Walliams to swim the Channel earlier this year, says exercise can increase ill health and death rates if approached in the wrong way.
Professor Whyte is a professor of sport and exercise science at Liverpool John Moores University and has examined the negative impact of chronic training on health and mortality which includes the harmful effects of chronic exercise on the body including skeletal, cardiovascular, respiratory, immune and hormonal systems.
Prof Whyte said: "I know that I am being extremely contentious by concentrating on the negative consequences of exercise but the research that has been done provides some startling findings.
"From club level to elite athletes, there are a lot of incidents to suggest that sport is very dangerous. You only have to go down to your local A&E to see the place packed out with 'weekend warriors' who are suffering breaks, joint injuries and trauma injuries to their head and face.
"If exercise is taken to extremes by people then exercise can do more harm than good, in particular the chronic, high-level exercise that elite athletes undertake.
"The bottom line is that moderate physical activity is good for you but exercise of the kind done by elite sportsmen and women can be detrimental to your health."
Prof Whyte added, : "There is no doubt that moderate physical exercise can be beneficial and not doing any is detrimental to health.
"But there is a cohort of individuals from these 'weekend warriors' to elite athletes who are going too far. The London Marathon for instance used to be the panacea of ultra-endurance but now it seems anyone feels they can do it.
"It is very difficult to gatekeep an event with up to 35,000 people participating but you should at least have been able to complete a half marathon before being allowed to join the runners.
"And for a half marathon you should have been able to finish a 10 kilometre run."
Prof Whyte said that Walliams needed about eleven months of hard training before he was able to swim the Channel. He said: "We did it in little stages so he did not do too much too soon and it paid off. But that is the sort of commitment you need.
"The success rate for swimming the Channel used to be about 10 per cent because so many people attempted it who did not have a realistic chance.
"But since the Channel Swimming Association decided you had to have completed a six hour open water qualifying swim before taking on the task the rate has shot up to 40 per cent.
"I myself have attempted it but had to give up two miles from the end - but at least I got relatively close."
Prof Whyte is also the director of science and research at the English Institute of Sport and he plans to discuss the issue at the British Association of Sport and Exercise Sciences' (BASES) conference at Wolverhampton University next week where he is an honorary research fellow.