When watching the Olympic Games this summer, you are going to see athletes at the top of their game pulling off some incredible performances. As you're watching these athletes create history, part of you may be asking – are these athletes actually human? Fundamentally, you want to know this: if you trained like an Olympic athlete, would you be equally successful, or just one of the number of athletes unable to qualify for the biggest sporting event on Earth?
The truth is quite complex. If athletes are different to the mere mortals watching them on TV, there may be differences in their genes that make them so. We do know that some gene variants are more common in athletes than non-athletes. Perhaps the most well known of these is ACTN3, often called the 'speed gene'. This gene creates a protein that is found in fast-twitch muscle fibres, which release energy for rapid activity. About 18 percent of people lack the ability to produce this protein as they have two copies of the recessive, non-coding allele of ACTN3 – the XX genotype. A multitude of studies has found the XX genotype in anywhere from 0–6 percent of elite speed-power athletes, which is significantly less than the normal population frequency of 18 percent. So it appears that the presence of the dominant, coding 'R' allele of ACTN3 might enhance elite sprint performance. In some populations, the XX genotype is even rarer; in African-Americans and Jamaicans it is present in as little as two percent of the population. Is it a coincidence that all but two athletes who have broken the 10-second barrier over 100m are of African descent?
But if genes do create world-class athletes, we don't know enough about them yet to make predictions. While studies about ACTN3 might appear promising, it's worth pointing out that roughly six billion people on the planet possess the R allele, and very few of them are elite athletes. There still are elite sprint athletes who have the XX genotype – they're just very rare. So while the R allele might be useful for athletes, it isn't essential. Currently, we know of about 120 genes that have at least one study suggesting they influence elite performance. This is insufficient to identify prospective athletes via genetic testing. Even if we take the 23 genes most strongly linked to endurance performance, there is only a 0.0005 percent chance of a single person having the 'best' versions of all of them. In reality, all athletes likely possess a combination of 'favourable' and 'unfavourable' genes related to sporting performance, and the vast majority of these genes are not yet identified.
And even if an athlete were to have the 'perfect' genes, they would still have to train in order to reach their potential. This involves having the right coach, the right training plan, and the right nutrition. It also requires a great deal of luck – staying injury-free, and the performance of your peers. Where you're born also has a significant effect; if you're born into a supportive family and have access to good sporting facilities, your chances of being an elite athlete are higher than if you're born into poverty.
But our genes can also influence how well we respond to training. It's been known since the mid-1990s that some people respond very well to aerobic training while others respond poorly. Different athletes could benefit greatly from different training programmes, even if their goals are the same.
In essence then, the athletes you will see winning gold medals this summer have a combination of favourable genes and favourable environment. The athlete with the 'best' genes won't always win, especially if that athlete doesn't train to the required level. On the other hand, an athlete who has the best training environment possible may be disadvantaged if they don’t possess any favourable genes. We should understand that the successful athletes will be the ones who have best maximised their genetics through the correct application of training, in addition to likely being dealt a better hand in life than many others.