For an instant guide to how fast a woman can run, take a look at her hands. Women whose ring fingers are longer than their index fingers are quicker on their feet, offering a simple way of predicting who will win a race, researchers have found.

The discovery could be a boon for parents wondering whether to shell out large sums on coaching - by providing an indication of their daughter's chances of turning into a sports star.

Unlike men, most women have ring fingers that are shorter or the same length as their index fingers. Only a few have longer ring fingers.

The finding adds to evidence that the ratio between the two fingers - not the length itself but their length relative to each other - is associated with a number of different personality traits, which include sexuality, fertility, intelligence, aggressiveness and musical ability. The difference is believed to be linked to the level of the male hormone testosterone, to which the foetus is exposed in the womb. Scientists have suggested that the higher the level of testosterone, the more masculine the resulting foetus is likely to be, with its associated traits of strength, fertility and mathematical ability.

Unfortunately, while a longer ring finger is associated with some desirable traits, such as musical skill, a longer index finger is associated with others, such as intelligence, past research has shown.

Professor Tim Spector, of the twin research and genetic epidemiology unit at St Thomas's Hospital in London, who conducted the latest study, said he had been sceptical about the claims.

"I didn't believe this stuff. Most of the studies were based on small numbers and the findings could easily be spurious," he said.

Professor Spector decided to test the claims because he had access to a large database of twins, on whom he has been conducting research for 20 years. He examined X-rays of the hands of 607 female twins aged between 25 and 79, and compared the lengths of their index and ring fingers. The women also ranked their highest level of sports achievement.

The results, which are published in the British Journal of Sports Medicine, showed that women with longer ring fingers were significantly better at most sports, especially those involving running, such as football and tennis.

Professor Spector said: "I was quite surprised to find something. The idea is that it is due to the hormone levels [of testosterone] in the womb. The longer the ring finger, then the more butch you are. But also you are more likely to die from heart disease.

"However, no one has detected these hormonal differences. We published a paper a few months ago which showed that 70 per cent of the effect was due to genes." Professor Spector said it was unlikely that a long ring finger conferred only good traits: "I would postulate that there is likely to be a downside too, such as people with longer ring fingers are likely to die sooner. If it conferred an evolutionary advantage, then everyone would have them."