This version, called the R allele, makes a substance called actinin, which lets muscles work more quickly and powerfully.
Ninety five per cent of the sprinters they tested had this gene, compared to 72% of normal people.
Another version of the gene, called the X allele, is very common in long distance runners.
More than one reason
But the scientists don't think that this discovery will lead to future athletics stars being identified from one gene.
Most experts think that a large number of genes, as well as hard work and healthy eating, make people good athletes.
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