Sunday, January 27, 2013

Can a Single Gene Predict Performance?

There is no doubt that genetics play a role in athletic performance. Few would deny that some athletes are more “gifted” than others. Over the past 10 years, researchers have identified specific genes and may predispose a player as a sprint/power or endurance athlete. Today, several companies offer genetic testing for budding athletes. For $100-$150, these companies will determine of players have the right genes for success in a particular sport. They argue that it’s best to know early on if you have the “sprint/power gene” or the “endurance gene”. However, within the research community, there is ongoing debate over how much influence a specific gene has on performance, especially in sports that require multiple traits. Researchers from Spain suggest that the link between single genes and performance in many sports is difficult to determine. This is especially true for swimming and soccer where performance requires a blend of power and endurance.

The ACTN3 gene has been linked to both sprint, power and endurance performance. In humans, it has three “genotypes”. A genotype is a subtitle difference in the structure and function of the gene. The proteins made from these genotypes also have differences that can change how they function in skeletal muscle. For the ACTN3 gene, the RR genotype is thought to be associated with sprint/power performance; the XX genotype with endurance performance and the RX genotype is somewhat of a cross between the two. For this reason, the researcher thought that the RX genotype would be associated with swimming performance.

In this study, Spanish researchers performed genetic tests on 707 individuals, looking for the ACTN3 genotype. They tested 119 power athletes (sprinters, jumpers, volleyball players), 154 endurance athletes (runners, cyclists, rowers) and 340 healthy non-athletes. They also tested 88 elite swimmers. All of the athletes tested were high level, competing for Spain’s national teams in veracious events including the Olympics.

The genetic analyses showed very little difference in the genotypes between the groups of athletes and control subjects. For example, the 31% of the control subjects had the RR or power gene, as did 27% of endurance athletes, 31% of power athletes and 35% of the swimmers. On the other hand 18% of the control subjects had the XX or endurance gene, as did 26% of endurance athletes, 13% of power athletes and 17% of the swimmers. Nearly half of the subjects, regardless of the group, had the RX gene. As can be seen, there is a great deal of overlap between groups and no clear-cut indication that a particular ACTN3 genotype predominates in one type of athlete or another.

The authors of the study raise two important points about tying a single gene to performance in swimming. They note that they did not find a significant relationship between the type of sport and the ACTN3 gene. They do acknowledge that there may be a “trade-off” between sprint/power and endurance genotypes such that an athlete may be more predisposed to one sport or another. However, they also emphasize that many sports, such as swimming require both power and endurance to be successful. For example, in events ranging from the 50 to 400 meter freestyle, top times vary from 30 sec to 5 min – a blend of power and endurance. Thus, the researchers argue that it is not surprising that the ACTN3 gene could not distinguish swimmers from other athletes and non-athlete.

Like swimming, soccer requires power and endurance traits. Players are asked to sprint, jump and change direction, activities that require high power output. They are also expected to run 5-7 miles per match, and endurance component. Add to that, technical requirements and decision-making and peak performance becomes a complex interaction of many characteristics.

Given this, it’s not surprising that previous studies show that soccer players have, on average, the RR or power ACTN-3 genotype. However, compared to endurance and non-athletes, the increase is small and the association with performance on the field is not high. As with the swimmers, it is difficult to argue that a single gene determines a prospective players fate.

There is no doubt that some players are more talented than others, that some players have genetic gifts that influence performance. However, it is unlikely that testing athletes for a single gene (or small group of genes) will shed much light on his or her potential as a successful soccer player. Performance is far more complex than that. Instead, attention should be paid on training, diet and, most importantly, developing a love of the game.

Reference

Ruiz JR, Santiago C, Yvert T, Muniesa C, Diaz-Urena G, Bekendam N, Fiuza-Luces C, Gomez-Gallegro F, Femia P, Lucia A (2013) ACTN3 genotype in Spanish elite swimmers: No “heterozygous advantage”, Scandinavian Journal of Medicine and Science in Sports, doi: 10.1111/sms.12045.

Other Studies

Massidda M, Corrias L, Ibba G, Scorcu M, Vona G, Calò CM (2012) Genetic markers and explosive leg-muscle strength in elite Italian soccer players, Journal of Sports Medicine and Physical Fitness, 52: 328-334.

Santiago C, González-Freire M, Serratosa L, Morate FJ, Meyer T, Gómez-Gallego F, Lucia A (2008) ACTN3 genotype in professional soccer players, British Journal of Sports Medicine, 42: 71-73.

Williams JH (2008) Genetic testing of young athletes? The Science of Soccer Online, Dec 21, 2008 (LINK).