Fast runners seem to have a natural advantage for their talent, believe scientists at Pennsylvania State University. Longer toes and shorter legs boosts their speed.
During the study, the researchers found that sprinters had 12 per cent longer toes - around half an inch on average - than their slower counterparts of the same height.
However, they found that the lower legs of speedy runners were shorter - about six per cent shorter on average - than more sluggish members of the public.
Dr Stephen Piazza, an expert in kinesiology, the study of human movement, said that computer models suggested longer toes provided more grip and shorter legs more power.
"It is all about the start of the sprint. It is then that the race is usually won or lost. Very long toes allow the power from the legs to be transferred to the ground and so increasing acceleration," the Telegraph quoted him as saying.
For the study, Piazza and his colleagues recruited 10 sprinters from the university as well as 10 more lay people of the same height and weight.
They measured various proportions of their legs to see what made people more likely to be a fast runner.
They found that the sprinters had big toes - measured from their metatarsal to the end of the nail - on average 3.22 inches (82.cm) long compared with 2.8 inches (7.3cm) in non-sprinters - an increase on average of 0.4 inches (1 cm).
Sprinters" lower legs - measured from knee to ankle - were on average an inch shorter than non-sprinters - around 16inches(41cm) long compared to 17.3inches(44 cm).
Piazza said that while the differences were small they were important.
"Not only could the sprinter generate more force while accelerating, but their longer toes allowed them to remain in contact with the ground longer during each stride, giving them longer to push against the surface and out perform slower sprinters," he said.
"It's important to acknowledge that there are many factors that contribute to sprinting performance," he added.
The researchers also found that the distance between the ankle ball and the Achilles tendon also played a part. The distance was 25 per cent shorter in sprinters.
The findings were published in the Journal of Experimental Biology.