Whether you are good at sprinting or are better at long-distance running is partly down to which version of a gene called ACTN3 you inherit, Australian scientists reported last week. They found that world class sprinters are more likely to have at least one copy of the 'R' version of the gene, which makes alpha-actinin-3 - a protein that enables muscles to contract more quickly and powerfully. In contrast, top endurance athletes are more likely to possess just the 'X' version of the gene, which does not make any alpha-actinin-3 protein. The researchers, based at the Institute of Neuromuscular Research in Sydney, published their results in the American Journal of Human Genetics.
The team studied DNA samples taken from over 300 athletes, 50 of whom had represented Australia at international level. They found that 95 per cent of top sprinters had inherited at least one copy of the R version of the gene, while 50 per cent had inherited two copies. But only 76 per cent of elite endurance athletes inherited an R variant, with 31 per cent inheriting two copies. And out of 400 control samples taken from the general population, 82 per cent had one R variant and 30 per cent had two copies.
When the scientists looked at the distribution of the X version of the gene, they found that just 5 per cent of sprinters had two copies, compared to 18 per cent of the controls and 24 per cent of the endurance runners. Team leader Kathryn North said that she thought that the absence of any alpha-actinin-3 protein means that a person's muscles are more 'slow' in character, and better suited to endurance activities. The group now intends to carry out animal studies to pinpoint the exact role of the protein in muscle fibres.
The ACTN3 study joins the previously-reported ACE (Angiotensin Converting Enzyme) gene findings as evidence for the influence of genetics on athletic ability. Variations in the ACE gene, which makes a protein called angiotensin-converting enzyme, affect how efficiently muscles burn oxygen, and also the rate at which some muscles grow. Hugh Montgomery, who led the team at University College London which carried out the ACE gene study, says he also has unpublished results for a third gene that predisposes for athleticism. But he dismissed the idea that future top athletes could be identified by genetic screening, saying that that many factors influence sporting success, including body size, lung volume and psychological make-up.