Your genes rather than rigorous training may determine whether you will complete a marathon in a good time, according to a new study.
Scientists have also developed a new genetic test that can reveal those among the runners who are more likely to complete a marathon in a good time.
Researchers found that to run a marathon in a good time requires the right combination of genes.
For runners with the right genes, it means their bodies can quickly adapt to carry large amounts of oxygen to their muscles, allowing them to run faster and for longer.
Those who lack these genes, however, will never improve, no matter how much they train, and their performance may even get worse the harder they push themselves, The Telegraph reported.
A new DNA test developed by the researchers behind the study could now help tell anyone hoping to achieve a decent marathon finishing time whether their efforts will be worthwhile.
Professor Jamie Timmons, head of systems biology at Loughborough University, has found more than 100 genes responsible for determining how the human body responds to stamina training.
He and his colleagues have found they can use 30 of these key genes to predict whether someone is capable of running a marathon well.
"If someone's ambition is to do a marathon in a decent manner, we can tell them if they can based on their baseline fitness and their potential for responding to training," Timmons said.
"From our work, we know that 20 per cent of people do not respond at all to training and in fact can get worse. They push themselves as hard as everyone else, but their muscles do not extract the same amount of oxygen," Timmons said.
"About 15 per cent have the genes that mean they will respond highly to training. But of that number, only those with a good inherited baseline fitness and good resistance to injury will ever become elite marathon runners, so that is an even smaller percentage," Timmons said.
The test works by looking at genes that are responsible for remodelling muscle fibres to allow small blood vessels to grow in between. These help to carry as much oxygen as possible to the muscles during exercise.
Those that have the right mix of these genes can grow new blood vessels and remodel their muscles effectively in response to regular intense aerobic exercise such as long distance running.
Timmons has now set up a company with his colleagues at Pennington Biomedical Research Centre in Louisiana and the Medical Prognosis Institute in Copenhagen to offer runners the chance to have their DNA tested.
They hope the test, called XRPredict+, will help people decide how hard to push themselves when training.
