Welcome to the Science of Sport, where we bring you the second, third, and fourth level of analysis you will not find anywhere else.

Be it doping in sport, hot topics like Caster Semenya or Oscar Pistorius, or the dehydration myth, we try to translate the science behind sports and sports performance.

Consider a donation if you like what you see here!

Did you know?
We published The Runner's Body in May 2009. With an average 4.4/5 stars on Amazon.com, it has been receiving positive reviews from runners and non-runners alike.

Available for the Kindle and also in the traditional paper back. It will make a great gift for the runners you know, and helps support our work here on The Science of Sport.

Thursday, August 11, 2011

Training, talent, 10000 hours and the genes

Genes and performances: Why some are more equal than others

The genetic influence on exercise performance is dizzyingly complex.  So complex that my best efforts to explain how genes may impact on the science of performance will fail to capture just how enormously complex the various interactions are.  It is so complex that despite the best efforts of scientists to find "the performance genes", they have failed.  This has been interpreted in some quarters to mean that these genes don't exist, that genes are unimportant and that training counts for all - nothing could be further from the truth.  The reality is simply that they're too numerous, with too small an influence, and too complex to find...for now.

However, having previously discussed the 'holes' in the theory that success in sport can be explained by deliberate practice, it's important to consider the genetic component.  When I presented evidence that showed, for example, that only 28% of variance in darts performance could be explained by 15 years of practice time, then it begs the question of where the remaining 72% lies?  When you consider that some athletes are able to become world-class within 12 months of taking up a sport, whereas others slog for a lifetime to stay mediocre, part of the reason may lie in the genes.

And of course, this is enormously complex.  So let me say this upfront today:  The science of success is about the coming together of dozens, perhaps hundreds of factors.  Practice, quality coaching and time spent learning are clearly key factors - this is why you get "hot-beds" of performance, exceptional athletes from anywhere that opportunities exist - the impact of training on performance is large enough that it can help to offset potential differences in innate abilities.  Can it turn anyone into a world-beater?  My opinion is no, but this doesn't decrease the value of the training.

Equally valuable, I believe (and some of the early evidence is below) are genes or innate ability, and this is what has been downplayed in the popular media.  It is not wrong to suggest that practice is crucial and that elite performers do many hours of training. But it is incomplete. And sometimes, incorrect, when you promote one at the expense of the other - training and genes are additive, not exclusive.  So when Ericsson writes in his 2009 paper that:
"distinctive characteristics of exceptional performers are the result of adaptations to extended and intense practice activities that selectively activate dormant genes that are contained within all healthy individuals’ DNA” (Ericsson et al 2009)
it must be challenged on the basis that the science may not necessarily support this.

And to help complete the picture, we look at genes - that is the context of this post.

As mentioned, I have recently written two review articles on this subject - one will be published in Dialogues in Cardiovascular Medicine to co-incide with next year's London Olympic Games, the other will hopefully be published in 2012.  My co-author, Prof Malcolm Collins, is a geneticist, and I owe a debt of gratitude to him for some of the genetic concepts I explain in this post.  So let's look at genes and performance.

The most powerful genetic influence of performance is...

At the risk of starting with the blindingly obvious, the first key point to make is that the single biggest impact made by any factor on sports performance is genetic, and it is biological sex.  Before people react negatively to that statement, please don't view it is a statement of superiority or inferiority - it is simply a fact, and is the very reason we recognize (and embrace) separate categories for competition.  Ask the following question:  If we did NOT recognize that men and women should compete in separate categories in most sports, how many women would be competitive?

Take marathon running - Paula Radcliffe holds one of the most respected records in athletics with her marathon world record.  That performance, easily the best ever by a woman, would have ranked her 473rd in an "open" world list in 2009 alone.  That is, 472 men were faster than this time in a single year.  In history, the time was ranked 3,205th, and that was in 2009 - it's now probably close to 4000th.

This gap exists in all athletic disciplines ranging from 100m to 100km - a 10 to 15% difference between the best men and women is seen across the board.  Of course, the differences may be smaller in other sports - skill-based activities that are not heavily influenced by size, strength, heart or lung volume, hemoglobin content etc may be more competitive.  But the difference still exists (would you back Serena or Venus Williams against Federer or Nadal?), and the result is that if we competed in only one category, no major sporting prize would ever be won by a female competitor.

This is the very reason that we recognize separate competitions - they enable competitiveness.  And the point is that this characteristic, biological sex, is entirely genetically determined.  There are of course cases where the neat binary system we create is skewed by intersex conditions, and we debate and discuss cases like Caster Semenya's endlessly.  In those instances, there is a mismatch between genetic and anatomical sex, such that the chromosomes no longer determine the biology.  However, genetics is entirely responsible for male and female characteristics, and this has an enormous impact on performance.

The question is, if genes exert such an enormous impact on the entire organism, are there similar genetic differences within each grouping, and do these affect various systems (muscle, heart, physiology) in the same way?

Genetic complexity - height as an example of complexity

The next illustration is height.  It's well established that height is a highly heritable characteristic. In fact, 80% of height has been linked to a number of genes (it's called a polygenic trait because many genes influence it), with the remaining 20% being down to environment and diet.

The key about height is that as "simple" a characteristic as it is, it is still impossible to identify all the specific genes and the contributions they make to it, how they interact.  And here, it's important to understand the approaches to the problem.  One can look for single genes - they are called "candidate genes" - that account for the biggest impact in height.  But because even something as relatively simple as height is polygenic, there is no single candidate gene.

There is not even a group of genes.  In fact, if you really want to get down to it, you have to do what are called Genome Wide Association Studies, where you look at the entire genome at once and look for how variations from one person to the next might account for different traits, like performance (or disease, for example).

And when you do this, the numbers become staggering.  Most recently, a paper in Nature Genetics found that you could explain 45% of the variance in height by using 3,925 unrelated people, and a staggering 294,831 different SNPs.  A SNP (pronounced snip), just to explain, is a DNA sequence variation, where for example Andrew might have a gene with a certain sequence, whereas Matthew has the same gene, but with a single change, a single 'different letter', that alters the function or effect of that gene.

In other words, it's not even as simple as having a gene or not, it now becomes a question of which variant in the gene you have!  If this is getting complicated, don't panic - it's because it is complicated!  The bottom line is that there is no such thing as a single gene that makes one person tall and another short.  There are hundreds of thousands of different gene variants, and these variations change the phenotype (the effect of the gene) so that you and a friend may have the same gene but because your SNPs differ, you have different traits or characteristics.

Let's just go back to that height finding, which bears repeating:  Height is almost certainly simpler than something as complex as human athletic performance, yet it requires almost 300,000 different genetic variants, and that helps us explain only 45% of it.  How many more SNPs or genes or DNA sequence variations might it take to explain sprint or endurance performance?  And this is why when you read that the latest studies have failed to find a gene that explains why Jamaicans are so fast, you should interpret it with the right insight because:
  • they are often looking for a 'candidate gene' (or small collection of genes), which is a huge oversimplification of performance as a polygenic trait, and;
  • there are simply not enough elite athletes in the world to be able to do the study that finds significant associations between that many SNPs and performance.  If it takes 4,000 people to explain less than half of height, then how many more may be required to explain sprint performance, of which height is only a small contributor?
This is also why those genetic tests that supposedly tell eager parents whether little Tim is going to be a sprinter or a distance runner are so over-rated.  These tests screen for several genes, including perhaps the most "famous" performance gene ACTN3, which is supposedly linked to elite sprinting performance.

The problem is, the studies comparing Jamaican sprinters and east African distance runners find no differences for that particular gene.  I hope I've shown you why this may be the case.  In the words of Prof Stephen Roth, one of the world's leading experts on genes and performance "It looks like the gene does contribute something, but only a very small amount at the very, very elite levels".  "Several genes" will sadly explain very little, except in rare cases.  And performance is not one of them.

So there is no single genetic predictor of success (or even of height), but this does not mean that genetics don't count towards success.  We are limited by our capacity to measure how these many thousands of gene variants interact, as the next study of training responses shows.

Genes and training responses:  Responders and non-responders

The next level of our genetic journey is to ask how genes impact on our ability to adapt to training?  This is clearly vital for aspirant elite athletes - whether or not you still believe in 10,000 hours, it's quite clear that some people adapt faster to training than others, or are able to more rapidly acquire skills than others.

The study that is needed to answer this question is to take a large, random group of people and expose them to training, and then to measure how much they improve.  And this has been done.  There are four studies, summarized in the figure below, where big groups have been put through a supervised training programme, and their VO2max measured as an index of fitness.

So, on average, VO2max will improve by 15% as a result of training.  In some studies, it's been as high as 19%, in others, 9%.  This may be due to differences in the training programme, or the people involved.  However, what you should be asking, especially given our look at Ericsson's violin study and the chess paper, is "What are the individual differences that make up that 15%, and what is the genetic impact in these studies?"

And for this, a paper by Claude Bouchard earlier this year.  In this study, 470 untrained volunteers were put through five months of training, and their fitness levels measured before and after.  The figure below shows the result:

As you might expect, most people improve by average amounts - 38% of the volunteers improved by between 300 and 500 ml/min (shown by they yellow and green bars in the breakdown of responders section).  But either side of these "typical responses", you see the extremes - the "low responders" shown in reds and oranges, and the "high responders" shown in blues and purples.  4% of the volunteers improved by 800ml/min or more, whereas 7% improved by less than 100ml/min.

Overall, there was a range of changes in VO2max all the way from 100ml/min (basically no improvement) to over 1000ml/min.  That's a 10-fold difference.  You may recall that yesterday, we saw how chess expertise showed an 8-fold difference between the fastest and slowest to succeed at reaching Master level.  It seems that a similar range of responses occurs for physiology.

The end result is that the bottom 5% of the sample, those who responded the least, improved their VO2max by less than 4%.  On the other end, the high responders, the top 5%, improved by 40%.  That is an astonishing difference, and the simple, and obvious question is where are you most likely to find an endurance athlete in this sample?  The answer is on the far right - the individual who shows large adaptations to training, improves quickly and then reaches a higher ceiling.  I am sure that every one of you reading this knows one of each of these people, perhaps you are one of them!

Note that this study does not take into account that ceiling, and nor does it account for the starting point.  Both of these may be influenced separately, and ideally what you need is a person who starts high, shows this kind of high response, and they are most likely to be the endurance achievers.

In terms of the genes, where's the link?  Well, Bouchard performed a genome-wide association study and was able to identify 21 of those previously mentioned SNPs (genetic DNA variations) that accounted for 49% of the difference in the training response.  As we saw for height, 49% is pretty solid, especially with only 21 SNPs - it suggests that height is not so simple...!

One of those SNPs was in fact responsible for about 6% of the training response, and as far as a single SNP goes, that's a pretty powerful association.  The figure below shows the association between SNPs and training response:

It turned out that the non-responders were people who had fewer of these SNPs than the responders.  If a person carried 9 or fewer of the identified SNPs, they improved by an average of 9% (about half the average), whereas individuals who had 19 or more of the 21 SNPs improved by 26% (almost double the average).  The three-fold difference between the responders and non-responders could thus be attributed to the presence of these sequence variations.  Not the genes - I can't stress enough that the search for a single gene is futile because performance is just too complex.  But rather individual variants that make up the response of VO2 to training.

And again, this is just one component of performance - think of the hundreds of other physiological attributes that make up an elite athlete.  The reality is that our failure to find a performance gene may be more a reflection on our capacity to understand the complexity of physiology and genes than it is an indication that genes don't make a significant impact.

The key genetic question: Same training, different responses?

The most powerful question, then, in my opinion, based on the above study, is the following thought-experiment:

If you took 470 volunteers from Kenya, and gave them the same training as was given to the 470 in the Bouchard study above, would you find the same range of non-responders to responders? Would you find that 7% of Kenyans improve their VO2max by less than 100ml/min?  And would you find that 4% improve by 800ml/min or more?

I would hypothesize that the whole curve would be shifted way over to the right - there would of course be low and high responders.  But the lower responders in the Kenyan sample, would, I suspect, be fewer and perhaps would improve by 200ml/min, not 100ml/min.  As for high responders, instead of finding only a few who improve by 40%, you may find many more.  This would be the indication of a genetic advantage - not that every single person is superior, but that within a given population (470 people in this case), you are more likely to find the physiological characteristics of a champion athlete in one group than in another.

And as soon as you super-impose the opportunity, the competitive environment, the altitude, the diet, the psychology, the culture and belief, the lifestyle, then you have the recipe for a distance champion - Kenya succeeds not because they have these factors, but because they apply these factors to an exceptional genetic pool.

Jamaica has the same scenario for speed, I would hypothesize:  a concentrated group of individuals who possess the necessary physiological attributes to run fast, and to respond enormously to power and sprint training.  Then onto that, you add the history, the role-models like Usain Bolt, the school competition, the excellent coaching, the culture of the island, and the result is the perfect mix to produce athletes who may well go on to win half a dozen Olympic gold medals.

No alchemy in elite sport - start with the right materials

But it all starts with the genetic potential.  In high performance sport, there is no such thing as alchemy - you do not make gold out of other metals.  If you want to produce a champion, a gold medal, then you must start out with the right raw materials.  Everyone will improve as a result of training.  Some, the lucky few, will start out at a level that is higher than the rest, and will improve more rapidly through training.  That this is linked to genes is, in my reading of the evidence, unquestionable.

There are other arguments, of course.  Some are obvious - your body size is strongly influenced by genes, and it limits the sports available to you.  For example, if you're 1.70m tall and weigh 70kg, you won't be playing high level rugby or American Football.  And definitely not basketball.  If you are 2.00m tall and weight 110 kg, then basketball or rugby are options, whereas long distance running probably isn't.  But these are almost absurd illustrations of how genes, which clearly determine these aspects of our physical makeup, influence performance.  But if this is true of these traits, then would it not be the case for something like hemoglobin, muscle enzyme activity/content, plasticity of the nervous system and motor skills?

Rate of performance improvement - a key symptom of innate ability

Last example - I was asked yesterday in a presentation on this subject whether a parent should try to 'diagnose' their child's potential using the genetic tests.  I explained above that these tests have very limited potential to do this, to the point of being useless.  It did get me thinking though about what we look for to detect whether those genes are present.  How does one know that a person has innate ability over and above the typical ability to learn any activity?  And I believe the key, as illustrated by Bouchard's study, is the responsiveness to training.

Of course, the starting point is also crucial, especially for sports that are "physiologically limited" (like running, cycling, swimming, triathlon, where muscles, heart, lungs and brain provide a ceiling for ability).  But for skill-based sport, where training time does matter, the key is how quickly the skill or ability can be acquired - this is the symptom of the innate ability.  I was asked about the Polgar sisters, for example - these are three Hungarian sisters who were taught by their father to play chess to prove that "genius are made, not born".

The coaching of their father, along with professional chess players who were employed to teach the three girls the game,  produced outstanding chess players.  Two became grandmasters, one an international master. Judit Polgar is the most accomplished female chess player ever.  Their story is often cited as a nurture over nature example.

But there are problems with that theory.  First, the fact that they were all family doesn't allow you to exclude genes.  But more than this, when you read the story and start to see not only what they achieved, but when it was achieved, it's difficult to make the case for many hours of training being the secret of their success.

For example, Judit Polgar, at the age of five, defeated a family friend (an adult) without looking at the board.  She defeats her father (a decent level chess playing adult) at five, and beats a Master level player at seven, playing blindfolded!  Remember that yesterday we saw that on average, it takes 11,000 hours of practice to become a master, and you realize how exceptionally talented Judit was.  She then beats an international master player at 10, and a Grandmaster at 11.  These are accomplishments that precede "many hours" of training.

Her sister Susan wins a local chess competition for Under 11s at the age of 4.  Within the first year of their exposure to the activity, they demonstrate exceptional ability, long before the 10,000 hours, long before the deliberate practice can explain their obvious ability.  What makes these sisters exceptional is not simply that they accumulate hours of training, it is that their ability to learn the skills is astonishing - defeating a Master at 7, while blindfolded, given that at most, you've done maybe 3,000 hours of training, is just a staggering illustration of superior ability, developed through training, certainly, but not a performance that you'll find in most people.

Sure, in order to continue to the Grandmaster level, to become the best in the world, it required more training.  But the trajectory was clearly there early, it was a symptom of innate ability, and so this is an argument for genes just as much as it is deliberate practice.

The Polgar sisters, to sum up, are the sporting equivalents of Missy Franklin or Michael Phelps - precocious talents who achieve within the first few years what others take a lifetime to do, and will often fail.  That is as much an argument for innate ability as it is for deliberate practice.  The only experiment that proves nurture over nature is if you can take 100 children, unrelated, and train them all to reach the same level of performance.  The simple fact is that this doesn't happen, and the reason is, at least in part, innate ability.

Conclusion: Two valuable frameworks, both absolutely necessary

I don't think it's revolutionary to suggest that BOTH genes and opportunity are needed.  In the scientific community, you'd be laughed at for suggesting this.  Most people believe that it's a combination of both, and that's why the current models, the best models for performance, integrate all these factors.  One such model is shown to the right - it's a framework for talent ID and development from a 2008 Sports Medicine paper by Vaeyens (click to enlarge).  It clearly includes natural abilities, catalysts, environmental factors and even chance.  These are the basis for current sports science beliefs, and the theories put forward in the popular media, and by Anders Ericsson, unnecessarily and incorrectly oversimplify this.

I can appreciate the value of the deliberate practice framework proposed by Anders Ericsson, popularized by Gladwell, Syed, Coyle etc.  It reinforces that we must better manage our entire sports environment to ensure that more potentially successful athletes are exposed to good coaching, good diet, competition etc.  This has implications all the way up to government level, where policies around sport are determined.  For example, in South Africa, sport is less accessible than it should be, partly because of the removal of sport from our school curriculum.  We also have a dearth of coaches, and few facilities - these factors combine to greatly reduce the chance that we'll produce a Phelps, Franklin, or even a great distance runner, regardless of the talent we have.

But equally, the realization that certain individuals have innate abilities that will help them achieve elite levels is crucial.  It influences where money is spent, how young athletes are steered, how athletes are encouraged to transfer from one sport to another (think of the lifesavers and sprinters who were given a shot at the Olympics and skeleton because of the Australian Talent transfer).  This too has implications for policy, and even for parenthood, in terms of understanding whether a child should specialize early or be encouraged to be as diverse as possible with their sport choices.

All in all, it's a fascinating debate, and thank you for your inputs and contributions to the debate so far.  As always, my aim is to have the first word in a debate, not the last, so I welcome more inputs.  In this post, I've proposed my theory, based on the early gene studies that are associating exercise performance with genes.  I've tried to highlight the complexity, and to illustrate that all is not as it seems.

The rest is for future studies, but I'll leave it with my ultimate conclusion.  To become an Olympic champion, the very best of the best, you need to tick the boxes.  Genes is without a doubt one of those boxes.  But so too are opportunities.  And so is success genetics or training?  It's both.  In fact, it's 100% genetic, and 100% training.