Are elite cyclists born or bred?

have to thank my parents for giving me good genes, and also my father for teaching me what I call good intentions. He always told me whichever race you’re going to do, race as well as you can, and you can say afterwards, whether you won or not, you gave your best.’

So said Marcel Kittel when Cyclist spoke to him in Antwerp last year. In one Germanic soundbite, the 26-year-old Giant-alpecin rider encapsulated the centuries-old ‘nature versus nurture’ debate. Is Kittel’s performance, and that of his elite brethren, predominantly down to genetics, or environmental factors such as training, nutrition and family set-up?

‘Genetic providence creates opportunities to become an elite athlete and contributes as much as 90% of how good you can be,’ says Ken Matheson, former coach at British Cycling. ‘Sadly, you can’t be whatever you want to be.’

Matheson’s thoughts are nothing new. Charles Darwin’s cousin, Francis Galton, is regarded as the original geneticist. In his 1869 book Hereditary Genius, Galton proclaimed, ‘There’s a definite limit to the muscular powers of every man, which he cannot by any education or exertion overpass.’

Genotype meet phenotype

On a basic level you can see where Galton is coming from. Nairo Quintana stands only 1.67m tall and weighs 58kg. His featherweight stature means he can float up mountains, but it also means he lacks the muscle mass to contend for sprints that require a power output of 1,600 watts. Lotto-soudal’s André Greipel, on the other hand, measures 1.84m and weighs 80kg. That natural load is detrimental on the climbs but pays off handsomely on the flats. So that’s it, then? It’s all down to your genes.

‘Not quite,’ says Ian Craig, leading exercise physiologist at DNAFIT. ‘Genes – which lie in long strands of DNA called chromosomes – lay the foundations for many characteristics, but your phenotype is who you are as a person. It’s where your genes interact with the environment. You might be the most genetically gifted person but be rubbish at sport because you grew up in a non-sporty family, “enjoyed” a bad diet and lacked sleep.’

In recent times, the nature-versus-nurture debate has intensified because of books such as David Epstein’s The Sports Gene and Malcolm Gladwell’s Outliers. The latter proposed that the route to becoming an expert at almost anything is to log 10,000 hours of practice, starting when you’re young. Epstein’s book, by contrast, suggests that not everyone can reach the top with sufficient practice, and that sporting success is often dictated by hereditary factors.

‘For each gene there are two letters [alleles] associated with it,’ says Craig. ‘They’re called base pairs within the DNA helix, and they’re essentially one letter each from your mum and dad. These dictate your physical, biological and psychological characteristics. I’ll give you an example: the ACE gene [angiotensinconverting enzyme] is involved in controlling blood pressure. For ACE, you inherit either an I or a D allele so the potential combinations are II, DD or ID. For ACE, II’S been strongly linked with endurance capabilities. DD’S been linked with power. DI is a mix of the two.’

So if both your parents’ ACE gene comprised II alleles, your sole permutation is II, meaning you’d exhibit endurance tendencies. It’s why thoroughbreds go to stud – and why superhorse Frankel’s semen is worth £125,000 a pop.

Some say performance on the bike is dependent on your genes. Others say it’s all about your upbringing. Let’s examine the science

Runners and riders

Yet still uncertainty derives from a horse comprising 20-25,000 genes – a similar number to humans. According to Yannis Pitsiladis, professor of sport and exercise science at Brighton University, in a review of 133 studies published during 1997-2012, only 59 genetic markers were associated with endurance and 20 with strength.

‘Sporting performance is a complex phenotype,’ he says. ‘To become an elite athlete, a synergy of physiological, behavioural and environmental factors is required.’

Pitsiladis is an expert on the subject. His work has taken him to Kenya in search of the