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Specialist Advice — 5 minutes

Untangling the DNA of sports

Michel Cameron, PhD
Michel Cameron, PhD
Pharmacogenomics Director

Every so often, an athlete comes along and completely shatters a world record, raising the bar yet again. But is it dedication and hard work that push the greatest through these barriers, or is it a matter of genetics?

The fastest man on earth, the charismatic Usain Bolt, currently holds the 100m world record, set in 2009 at 9:58, breaking the previous record of 9:74. Another extraordinary example is Michael Phelps, who, during his career, won 28 Olympic medals (23 gold) and set 39 world records, six of which still stand today. Of course, essential to every elite athlete is a commitment to their sport that is difficult to find, as well as the resources and coaching required for optimal training. But there’s another inevitable question: given similar work ethics and support, is there something in the DNA of people like Bolt and Phelps that enables them to destroy the competition?

Our scientific understanding of this question is still somewhat limited. Due to the complexity of sports genetics, we cannot determine what genetic factors help someone become a world-record holder. However, scientists have begun to understand how some genetic factors can influence certain sporting traits.

We know that a single gene does not determine a person’s overall athletic ability—it is the result of many different factors. Cardiorespiratory fitness and response to training are two very important aspects of sports performance but, like peeling an onion, studying either of these aspects will reveal multiple underlying layers of complexity. For example, measuring cardiorespiratory fitness could include maximal oxygen uptake (VO2 max), blood volume, capillary density, or mitochondrial efficiency.

Two of the most studied genes associated with athletic performance are ACTN3 and ACE. Both of them can affect the way muscles are built. ACTN3 provides instructions to build a protein, alpha-actinin-3, that is very abundant in fast-twitch muscle fibers[1]. These fibers provide quick bursts in strength, useful in activities like sprinting over 100 meters. Genetic has found that certain versions of the ACTN3 gene are common in athletes who rely on strength and speed[2]. Other versions of the gene, such as the R577X variant, leads to a complete absence of the alpha-actinin-3 protein, which appears to reduce the proportion of fast-twitch muscle fibers and increase the proportion of slow-twitch fibers[3]. Interestingly, some studies have found that this latter version is common in endurance athletes, such as long-distance runners and cyclists[4]. Similarly, different versions of the ACE gene have been linked to the amount of fast-twitch muscle fibers and greater speed[5].

These examples highlight how genetics can influence physiological traits that are important for athletic performance. However, the genetic impact of other factors important for sports performance, like personality traits and intellectual ability, is largely unknown. While the challenge is significant, new discoveries will emerge as technology advances and interest in this field continues to grow. As each contributing genetic factor becomes understood, the difficult task of integrating them into an indicator of sports performance will begin. Whether or not this ambitious goal is achievable, how this information will be used by scouters in the future, or not, will inevitably be controversial.

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  1. Del Coso et al. (2019) More than a ‘speed gene’: ACTN3 R577X genotype, trainability, muscle damage, and the risk for injuries. Eur J Appl Phys 119: 49-60.
  2. Berman and North (2010) A gene for speed: the emerging role of alpha-actinin-3 in muscle metabolism. Physiology 25: 250-9.
  3. Miyamoto et al. (2018) Association analysis of the ACTN3 R577X polymorphism with passive muscle stiffness and muscle strain injury. Scand J Med Sci Sports 28: 1209-14.
  4. Grealy et al. (2013) The genetics of endurance: frequency of the ACTN3 R577X variant in Ironman World Championship athletes. J Sci Med Sport 16: 365-71.
  5. Loos et al. (2015) Advances in exercise, fitness, and performance genomics in 2014. Med Sci Sports Exerc 47: 1105-12.