Genes – Key to Success

Genes – the Key to Success

Talent and training are all very well. However, for many athletes, that step onto the rostrum is thanks in no small part to their genetic make-up. Researchers have already found dozens of “athlete genes” and developed corresponding tests. Their goal: to find tomorrow’s stars.

By Sascha Karberg

They call him "Ox“, and actually, Matt Orford’s build and the fierce expression on his face really is reminiscent of a bull. He is strong, fast and nimble with the egg-shaped ball, and has enough endurance for two hard halftimes. A while back his coach, Des Hasler, made him team captain. It is possible that this decision was influenced by the genetic profile of the athlete, but the coach of Sydney’s Sea Eagles rugby club does not discuss this publicly. The Australian club is on rocky terrain here since all 24 players were asked to undergo a genetic check-up. “We tested them for the genes that are important for athletic performance”, says Steve Dank, physiologist of the Sea Eagles. “The result should give us information about the physiological characteristics of our athletes.” Coach Des Hasler does not believe that matches can be won just by doing this, but he says: “We can get an edge in some areas, for instance, in optimizing training."

Up until now only talent and hard practice – and sometimes doping – were considered a guarantee for an improvement of athletic performance. Today, it has dawned on researchers and trainers that all efforts may have been for naught, if a person’s genetic make-up limits his/her desire to win. It is now known that the ability of endurance athletes to move large amounts of oxygen in the blood to the muscles is up to 50 percent dependent on certain genetic mutations. The strength of fast muscle fibers, an important requirement for sprinters, depends up to two-thirds on genes. This was shown in performance tests on identical twins.

“It is undisputed that genetics have an impact on physical abilities”, says Bernd Wolfarth from the Polyclinic for Preventative and Rehabilitational Sports Medicine at the Technical University of Munich. Together with Claude Bouchard of the Pennington Biomedical Research Center of Louisiana State University and other researchers, the specialist in sports medicine has collected approximately 150 genes. The hereditary genetic characteristics determine how strong the muscles are, how many blood cells pulse through the veins and how efficient the athlete’s metabolism is.

That parentage influences physical abilities is obvious even to non-specialists. For more than a quarter of a century no Caucasian sprinter has won Olympic gold in the 100 meter sprint event; in this discipline runners with West African roots lead world ranking lists. Runners of East African descent in turn hold most records in long-distance running. Geneticists surmise that genotype variations that boost sprinting abilities are predominant among the West African population, whereas among East Africans the predominant genotype variations are those that develop muscle fibers to be optimized for endurance activities. Among Europeans and Asians such specific characteristics are rarely found.

Even in earlier decades, athletes with exceptional gene variants made it to the top of the rostrum. One of the rare cases in which this has become public knowledge was the cross- country skier Eero Mäntyranta. In spite of his relatively modest height for this discipline of barely 1.70 meters, the Finn outclassed all of his competitors in the 1960s. In a subsequent test it was found that, due to a genetic mutation, Mäntyranta’s organism reacted very strongly to small amounts of his body's own hormone erythropoetin (epo); his body produced an enormous amount of red blood cells that transported oxygen and thus

increased his endurance performance. “Mäntyranta constantly engaged in a form of natural doping", says sports medicine specialist Wolfarth. The athlete had always more than 200 grams per liter of blood of the blood pigment hemoglobin in his veins. Today, for example, cross-country skiers without such a genetic mutation are excluded from competing if they show a value above 170 grams; not least in order to protect them from dangerous consequences such as clogged blood vessels and heart attacks, but primarily because such a ratio raises suspicions of doping. Mäntyranta’s body, however, was optimally adjusted to such viscous blood.

With such examples in mind, Jason Gulbin, coordinator of the state-run Australian “Talent Search" program, wants to take a look at the genes of young athletes in the future. Gulbin is working with the research team of Kathryn North at the Institute for Neuromuscular Research of the Children’s Hospital in Westmead in Australia. The researchers compared the genetic make-up of 107 sprinters and weightlifters, 194 endurance athletes and a control group consisting of 436 people who were not very athletic. Their focus was on a gene called Alpha-Actinin-3 (ACTN3) that seems to be especially important for top sprinters. ACTN3 is active in a type of especially fast-twitching muscle fiber, but is often inactive due to a mutation. The basic muscle function does not suffer from this inactivity because a similarly working gene, ACTN2, takes over. In the marathon runners' group as well as the "no sports" fraction, the active and the inactive ACTN3 variants were evenly distributed. In two-thirds of the sprinters, however, the active variant predominated. The researchers concluded that athletes with an active ACTN3 gene have an above-average chance of becoming top sprinters.

Thus genetic research provided an explanation for a phenomenon that coaches have always observed: a long distance runner will never make a good sprinter and vice versa. This either/or relationship can also be found with the ACE gene that produces a specific enzyme. Researchers suspect that the variant I of the gene reduces the activity of the enzyme, which keeps blood vessels enlarged and ensures better oxygen supply to the muscles. Variant D produces the opposite reaction. Accordingly, variant I is found very often in endurance athletes. Hugh Montgomery of the Rayne Institute in London discovered that variant I is found twice as often compared to the normal population in mountain climbers who can climb above 7000 meters without an oxygen mask. Variant D predominates in sprinters and seems to be essential for the growth of fast-twitching muscle fibers.

Now even hobby athletes can take a look into the genetic crystal ball. For about 60 Euro, the Australian company Genetic Technologies offers an “ACTN3 sports gene test”. According to the company, customers can test whether they are “naturally more suited to sprinting and strength-related sports activities or endurance-related sports activities.” The test apparently helps "to maximize your natural performance potential – regardless of whether you are already an experienced athlete or just at the beginning of a sports career." Genetic Technologies also claims that the test can help with the structuring of sports training to achieve optimal results – but also warns against planning a child's sports career on the basis of the test results.

Sports medicine specialist Wolfarth thinks that such tests are "charlatanry". Athletic success cannot be reduced to the workings of a single genetic mutation. In fact, numerous genes would need to cooperate to make one athlete more predestined for endurance-related sports activities than for strength-related ones. In the future, a test could at best point towards the general limits of an athlete’s performance abilities or help with the direction towards a specific discipline. “However, it will never be possible to predict whether a talented athlete will be able to run 100 meters in 9.6 or in 9.8 seconds”, says Wolfarth. It should not be forgotten that genetic characteristics have only between 25% and 40%

influence on the variability of physical performance. In addition, environmental influences are very important. This can also be seen in Eero Mäntyranta’s case: He was the only successful athlete in his family, although 25 of 97 examined Mäntyrantas had the same genetic mutation. It was his interest in cross-country skiing, his application, and his immense will that made him into an exceptional athlete.

Nonetheless, coaches like Des Hasler hope that, with the help of test results, it will be possible to understand how the body functions in high performance situations and which physiological processes need to be stimulated to improve performance. In the case of the rugby players at least eleven genes were studied that are important for oxygen and lactic acid content as well as for muscle growth. Taking the test results into consideration, the coach put together an individual practice program for every player. “We do not want someone running 100 kilometers per week, if his genes say that 50 kilometers and strength training would have more of an impact", says Eagles' physiologist Dank.

“We do not have any hard data that proves the practical usefulness of such tests”, admits geneticist Claude Bouchard. This is mainly due to the fact that the classic athletic gene examples of ACE or ACTN3 resulted from so-called case comparative studies. In these only the frequency distribution of one gene in different populations is studied. Ultimately, such a purely statistical relationship cannot be considered conclusive evidence. To get conclusive evidence researchers have to prove that a gene variant actually does influence a certain performance. This can be easily proven using lab animals such as mice or flies: the specific gene just needs to be switched off and it is possible to observe whether the performance changes accordingly. It is more complicated to find such a direct causal relationship in humans. Bouchard’s HERITAGE study shows this. Approximately 650 test subjects were trained for 20 weeks following a standard schedule. Participation was open to entire families; the researchers’ only condition was that the test subjects did not engage in any sports activities within six months before the start of the study. As expected, the test subjects reacted very differently to the training schedule. Some people made rapid progress while others barely showed any changes. The researchers were also able to observe these differences between families; some mastered performance tests better overall than other families whose genetic make-up possessed predominantly the less advantageous genetic variants.

Jason Gulbin of the Australian “Talent Search” program was electrified by these study results. However, he was recently forced to put his cooperation with genetic research specialists on ice – under government pressure. There were “misgivings that people might misunderstand what we are doing here”, said Gulbin. The public had gotten the impression that a type of genetically engineered athlete generation was to be bred – although there was never even any thought of manipulating the genetic make-up. There are solid bio-ethical questions that would need complete clarification; how to deal with results in which the athlete gets to see not only his/her performance potential, but also the risk of certain illnesses? It is known, for instance, that a variant of the ApoE4-gene increases the risk for boxers to suffer brain damage after being hit on the head.

There is already a precedent among U.S.-basketball players: Eddy Curry of the Chicago Bulls was asked by his club to take a gene test after doctors had diagnosed the 24-year-old with cardiac arrhythmia. They wanted to find out whether there was a genetic risk for a sudden cardiac arrest during a game. Curry refused to take the test. A positive result would have raised doubts about his athletic fitness and would have ended his career. Half a year later, the Bulls sold Curry to the New York Knicks who let him play again – without genetic testing. 

Geo Wissen