The Sports Gene by Sports Illustrated journalist

I am very enthusiastic about this book and mentioned it at the Swim Ireland Performance Advisory Group earlier this year. National Performance Director, John Rudd, asked that I write this review, largely for coaches. What resulted (see below) should be of more general interest to all of those interested in competitive sport. I submitted the finished review to John Leonard of the American Swimming Coaches Association and he agreed to publish it in their Newsletter.

I strongly recommend this book for your Christmas reading. It is even reported that Barrack Obama was seen buying a copy!

Review of The Sports Gene: talent, practice and the truth about success.

By David Epstein, 2013. Yellow Jersey Press, London.

(Published in the American Swimming Coaches Association Newsletter, November 2018)

The Sports Gene by Sports Illustrated journalist, science graduate and middle distance runner David Epstein is an intriguing, widely researched and informative book. It should be required reading for all those interested in competitive sport. Perhaps this reviewer, being both a professional geneticist and swimming coach, is biased, but the way Epstein presents things, using a mixture of stories about individual athletes and modern research concepts, should appeal to a very wide audience.

    Though the title suggests that this book is all about genetics and how genetic principles apply to sport, it is in fact much wider than that. The broader question is whether elite sporting prowess is a consequence of genetics (“nature”) or the environment (“nurture”) or some mixture of both. Despite favouring one or the other in different sections of the book, Epstein concludes, in a more recent afterword to the Paperback edition, that obviously both are involved. Regardless of genetically-based aptitude for a particular sport (the “nature” part), a person will not perform optimally, particularly in endurance sports like most competitive swimming, without a huge amount of training (conditioning or “physiological adaptation”) augmented by technique optimisation, and accompanied by additional elements like nutrition and positive psychology-the “nurture” part. The book makes little reference to competitive swimming, concentrating instead on track and field athletics (the author’s specialisation), baseball and basketball, but most of these examples have general sports science relevance.

    The Introduction identifies individuals with exceptional sporting talent and frames the nature vs nurture question. Epstein then describes the Human Genome Project which was completed in 2003 and shows how this led to a series of experiments which attempted to relate single genes to variation in performance. However we know that for the majority of traits (the so-called phenotype i.e. the trait that can be observed and measured), multiple genes plus the environment are involved, greatly adding to the complexity of detection. (Think human height, where so many genes are involved that inheritance is described as omnigenic and where there is also obvious environmental influence, e.g. nutrition, health etc.). Several individuals can undertake the same training regime and yet perform very differently in races so the must be a major genetic component to performance. In contrast, Chapter one entitled “Beat by an Underhand Girl” describes a situation where experience rather than genetics is paramount. The softball pitcher Jeannie Finch was able to beat professional baseball players because they were unfamiliar with her technique and therefore could not “read” the direction of flight of the ball from her wind up. It seems that what is involved here is not lightning fast reactions, though these are endemic in top softball and baseball players, but lack of familiarity with either’s technique. The chapter then goes on to describe how experts (e.g. chess grand masters) vary from “just” good players by their ability to read the game and “chunk” information into packages, which, of course, brings us back to genetics. In the conclusion of this chapter and into the next, a variety of slightly confusing but intriguing case studies are presented. The 10,000 hour rule is discussed. This is the idea that 10,000 hours of practice are required for a person to reach their full potential in a specific activity, be it a sport or in orchestral music. (This idea was proposed by a psychologist working with young elite musicians but was leapt on by the popular press as an invariant “rule”.) A description is given of a golfer who is half way through that number of hours of practice and hopes to reach the top ranks. Frustratingly, the final outcome is not described but it turns out that 10,000 hours is an average figure with a wide variance, and, in any case, is influenced by innate ability. It is also interesting that in longitudinal studies (looking at the same individual over time) future elite performers often do less practice in a specific sport or other activity initially, than less able performers. They only start to put in longer hours in response to progress to elite level, perhaps arguing against early specialisation in a particular sport.

    A mixture of relevant topics is then presented. Two world class high jumpers are discussed, one of whom had particularly stiff Achilles tendons enabling greater spring, but then also practised intensively, and another with amazing natural ability. Visual acuity as an asset within a sport like baseball or tennis (but not between sports as mentioned above) is then presented. This is followed by something rather different-the difference between male and female performance. Sex testing at top International level was originally based on sex chromosomes, but testosterone level is now the approved measure. The latter can of course be influenced by ingestion of anabolic steroids (banned substances), which result in females getting closer to male performance and accentuation of male performance.

    The chapter entitled “The talent of trainability” is perhaps the most relevant and important for swimming coaches. It begins by describing the incredible improvement of the World Record mile runner Jim Ryun; showing a high level of innate ability and then great improvement on one of the heaviest training regimes then extant. The scientific basis is demonstrated in the HERITAGE study by Claude Bouchard and colleagues. When they tested the aerobic improvement, expressed as improvements of V0₂max, of a large number of college students it was shown that while the majority showed average improvement, a minority improved very little (termed low responders) and another small group improved greatly (the high responders). Similar results were found in the GEAR study and more recently in a study in Nottingham University in England. These results held regardless of initial level. Obviously, for endurance sports, high responders have an advantage. Further molecular work has isolated 29 genes, each of which occurs in two alternative forms, which act as predictors of this talent. There is a strong association between individuals which have the “beneficial” form in a majority of these gene markers and great response to aerobic training.

    In this and the next chapter the theme of muscle fibre composition is explored. Human and other vertebrate animal skeletal muscles consist of fibres of two distinct types-white fast twitch explosive largely anaerobic fibres and red slow twitch aerobic “endurance” fibres. The proportion of these fibres is genetically determined-nature again; as proven by identical twin studies where the twins have been trained in completely different ways. Among elite runners those excelling in sprints have high proportions of fast twitch fibres (>75%) with middle distance specialists (and much of humanity) at 50:50 and long distance types having a preponderance of slow twitch fibres (up to 80%), as demonstrated by calf muscle biopsy. Improvements in strength again have a major genetic component with individuals gaining from 0 to 250% improvement with training in leg and chest presses in trials. Variants of certain well-characterised genes such as IGF-2 and myostatin are involved here. Matching muscle composition to event has been particularly successful for example in moving a Danish kayaker from short to long events resulting in Olympic qualification and World Class performances.

    The next chapter describes how body types in specific sports have morphed from what was considered a single ideal “sporting” body type in the early 20th century to the present situation where there are highly specific body types in most sporting events. This is followed by a detailed consideration of extreme height in professional basketball players. All of this implies extreme selection of those that can excel in many sporting events today. There follows a chapter on human evolution and the so-called “Out of Africa” hypothesis of modern humans. This subject has been described in far more detail elsewhere and is perhaps less relevant to the main theme of the present book. Jamaican sprinters are then considered, focussing particularly on the part of the island where Usain Bolt was born. Again, while it is not specifically stated, the mixture of genetics (nature) indicated by a high preponderance of explosive fast twitch fibres and the environment (nurture), since sprinting in Jamaica is regarded as the most important National sporting activity, is evident. This high proportion of fast twitch muscle fibres in individuals whose ancestors were brought forcibly to the Americas from West Africa is considered by some scientists to be a response to natural selection caused by malarial infection in ancestral regions of Africa.

    The focus then switches to distance running and the supremacy of the Kenyan Kalenjin in this sport. Here both the environment (nurture-running long distances in daily activities and the high altitude of their natal area) and genetics (nature) underlying body type are important. Most top Kalenjin runners have proportionately long legs with narrow light extremities, enabling a highly efficient running style. The physiological characteristics produced by being born and growing up at altitude are obviously beneficial for distance runners, but it is also interesting to learn that different physiological adaptations occur in East Africa, Nepal and the Andes. As an aside, the subject of high altitude training for sea level athletes is evolving all the time, though of course no direct genetic correlation is suggested here.

    Themes like the breeding of Alaskan sled dogs for long distance races and genes that have detrimental effects in exercising humans (for example those genes involved with cardiac myopathy) are then introduced. The final descriptive chapter deals with a single gene mutation in a Finnish cross country skier. This very rare variant involving the haemoglobin gene resulted in the individual having significantly more circulating red blood cells than normal, catapulting him to world class. However, it is interesting to observe that his lifestyle involved a huge amount of skiing as a youngster and later as a border patrol agent, providing the perfect combination of nature and nurture. The Sports Gene concludes with an Epilogue called The Perfect Athlete, which again reiterates that having the ”right” genetics for a particular sport ( and there may be several varieties of “right”) certainly helps, but this is useless without many years of dedicated practice. And genetics is not sufficiently developed to do more than help in the effort to develop more proficient athletes!

Relevance to competitive swimming: So what does all this mean for developing elite competitive swimmers? In the first place genetics of traits for athleticism are not sufficiently understood to recommend any form of early testing of individuals i.e. testing 8 to 10 year olds and on the basis of results saying that the potential is there to reach the top after several years of optimal training, or at the other extreme-“you are wasting your time in this sport”. A big problem is to define natural (=genetic) ability. Which trait are we seeking? Is it the ability to learn to swim quickly; to optimise techniques such as starts, turns, finishes and underwater and surface strokes, pacing and other racing techniques; to improve rapidly through the stages of the competitive programme; to appear at one with the water in terms of feel of strokes and streamlining; superior ability in speed or endurance; ability to train and compete hard over many years; to avoid chronic illness and recover from injury, or some other trait? All of these traits are likely to have a genetic basis, and in all probability a somewhat different suite of genes will be involved in each. It is also likely that each of these traits are influenced by multiple genes (what geneticists refer to as polygenic inheritance), where each gene has a small cumulative effect. Traits influenced by single genes in humans or other animals (what geneticists refer to as monogenic inheritance), are extremely rare. Think of the cross country skier referred to above who seems to be the only individual amongst millions of humans having this specific mutation. Thus the search for the Olympic champion single gene is likely to be illusionary, and even if detected, genetic technology is not sufficiently advanced to allow safe manipulation. Given these considerations, what might be usefully done with genetic testing?

    Testing takes two overlapping forms-tests which provide information which do not allow manipulation (measuring height in fully grown individuals) and the more useful measurements where some action can be taken (like measuring VO₂max regularly as the season progresses). Two recommended “genetic” tests, given the current state of knowledge, are muscle fibre proportion and trainability. In the case of muscle composition, while the “gold” standard is muscle biopsy, a simple vertical jump test (see Maglischo and other earlier swimming literature for details) gives a good measure of muscle fibre composition. The result when applying the vertical jump test to a large number of performance pathway swimmers will be a normal distribution (a bell-shaped curve where the majority will be 50:50 in terms of fast and slow twitch fibres), but a minority of individuals will be high in explosive fast twitch fibres (sprinters) or slow twitch fibres (800, 1,500 and open water specialists). Even though this is a test of phenotype (phenotype = genotype plus environment; termed G + E), it gives a good measure of genetic differences, because most of good competitors within a geographic region will be experiencing a similar environment. We have tested this with high school students in a PE class and found excellent correlation with running sprint speed (unpublished results). It may be that we are trying to train athletes in the wrong events because muscle fibre proportion is an innate trait influenced very little by conditioning i.e. one cannot make a sprinter great at 1,500m or vice versa for a distance type in the 50m, and the optimal training regimes are very different.

    Another trait which can be measured in trainability. Of course, this can be measured empirically i.e. how do elite swimmers respond to say 12 weeks of a good training regime in terms of VO₂max. However, as mentioned above there is a significant positive correlation with having a majority of certain variants at 29 designated gene marker SNPs (single nucleotide polymorphisms) and high levels of trainability. An inexpensive and rapid molecular genetic test will determine genotype at these 29 genes. If for example a swimmer scores low on the trait of endurance trainability, one may be dealing with a potential sprinter (as a simultaneous muscle fibre composition test should show) and/or the swimmer might be encouraged to make additional efforts in technique development. Similar tests of potential strength acquisition are available and more tests will become available as the rapidly advancing genetic field progresses. It is not suggested that genetic testing should supersede other physiological, anatomical, biochemical, nutritional, biometric, hydrodynamic (video) and psychological tests; but they should form part of the “toolbox”, when more efficiently attempting to produce faster competitive swimmers.

Tom Cross