The role of genetics on sport performance

Did you know that the human DNA is over 95% similar to monkeys and 99,9% identical across the human population (Francis, Collins, & Mansoura, 2001). Yet, we are so different, we don't look the same and one seems to gain muscle mass quicker than others, despite same training program. Let's explore the topic of sports genomics. The sports genomics is a relatively new field of science which investigates genetic influence on human performance (Ahmentov, & Fedotovskaya, 2015; Ahmetov et al. 2016; Bouchard, & Hoffman, 2010). The early days of sports genomic science were seeking to discover if elite athletes were genetically different compared to the standard population. In contrast, the modern science of sports genomics has agreed that sports genomics does exist. Therefore, the current question is, what are the sports genes and how do they physiologically affect our performance (Lippi, Longo, & Maffuli, 2010). Interestingly, it has been speculated that muscle mass may be up to 40 % due to our genetics and anaerobic power up to 70% due to our genetics (Issurin, 2017). The purpose of this article is to scratch the surface on current knowledge about sports genomics and discuss its potential impact on athlete performance. Due to the complexity of genetics, the primary drive to this article is to illustrate some base knowledge of sports genomics, which may explain a small part of the phenomenal performances seen in the world of sports. Lastly, the author of this article is not an expert in genetics.

Ahmetov et al. (2016) reviewed that the literature has shown in the last two decades, up to 150 genetic markers that have been linked with an elite athlete status. However, the thorough understanding of how the genes and their variants relate to human performance is unclear. It should also be noted, that the literature is not all consistent with genetic findings (Eynon et al. 2013; Mattsson et al. 2013; Meckel et al. 2012). Nevertheless, a few genes and their variants are consistently popping out in the literature as sports genes such as AMPD1, ACTN1 and ACE (Ahmetov et al. 2016; Dias et al. 2007; Eynon et al. 2013; Harvey et al. 2019). Interestingly so, it’s been speculated that the gene presence alone may not alter the performance. Rather the epistatic interaction, which is the interaction on how genes function as a unit (Ahmetov et al. 2016).

Therefore, it may be worthwhile to take a step back and re-visit the basics, such as what is a DNA (deoxyribonucleic acid) and what do we know about our genes. To explain the complex biology of genes in simplified language. In normal cases each human has two sets of chromosomes (chromosome 46 from mother and 23 from father) in each cell nucleus. The chromosomes are very tightly packed double stranded DNA which contains our genetic code. Our body needs protein for example building muscles, repairing injuries and function properly. A recipe for those proteins and its subtypes is in our genes. Firstly, the DNA is transcribed to RNA (ribonucleic acid) and then RNA is translated to protein. (Cooper, 2000; Musunuru et al. 2015). Interestingly so, the human DNA is over 95% similar to monkeys and 99,9% identical across the human population (Francis, Collins, & Mansoura, 2001). The difference that makes eye colour different from another is the gene variants (Cooper, 2000; Musunuru et al. 2015). Humans have approximately 20 000 – 25 000 genes, but one gene can have a large number of variants. For instance, ACE gene has variants that are linked to sport performance (Ahmetov, 2016; Cooper, 2000; Francis, Collins, & Mansoura, 2001). Gene variants can be explained as if they were like cooking books, where every recipe contains same ingredients, however, in some of the books, the same recipe uses pink salt instead of normal salt or the amount of sugar in one recipe is one gram instead of two. That can be due to multiple reasons, such as gene mutations. In genetics, that would mean that one gene variant may lead to higher enzyme activity or concentration between two humans. Theoretically this may explain why one athlete with one gene variant responses to stimulus inversely compared to another athlete with another variant. For instance, excessive activity of angiotensin-converting enzyme has been linked with decreased vascular resistance, which can be a substantial performance-related factor in cardiovascular and energy metabolism system.

One ACE gene variant is classified as one of the endurance performance gene and another variant of ACE is classified as strength and power gene (Ahmetov, 2016). The ACE gene is a structure of 26 exons and 25 introns. The exons are the coding sequences of the DNA, and the introns are intragenic regions inside the gene (Mugandani, 2019). It is believed that the endurance variant of ACE gene regulates vascular flow by decreasing the vascular resistance. That may facilitate a higher cardiac output and increase the flow of oxygen and metabolic substrates (Lucia et al., 2005; Lucía et al., 2010; Scanavini et al., 2002). In contrast, the strength and power variant of ACE gene has been linked with the higher muscular volume and with the number of fast-twitch fibres (Ahmetov, 2016). Another sports gene and relatively well-studied gene is Adenosine monophosphate deaminase (AMPD1). Adenosine monophosphate deaminase has an important role on energy metabolism in the muscle. It transforms adenosine monophosphate (AMP) into inosine monophosphate (IMP) that is in the chain process of ATP production (Ahmetov, & Fedotovskaya, 2012; Ahmetov, 2016, Dias et al. 2007). The AMPD1 gene has 16 exons and 15 introns and the gene has several variances. One variant of AMPD1 have been linked with increased sprint and strength performance, which might be due to higher activity of adenosine monophosphate deaminase (Mugandani, 2019). However, the precise function of AMPD1 and its link to the sports performance is yet to be fully understood. The list of sport performance associated genes and their variants are a broad list and beyond the purpose of this article. However, even the exact understanding of a gene interaction to sports performance is unclear. The current findings have somewhat promising evidence that genetics may have a substantial role in how our bodies regulate and respond to a stimulus. Therefore, it is worthwhile to raise a question if genetic differences is the thing we often call being talent.

Indeed, it could be argued that talent and genetics are difficult to disassociate totally from each other. On the other hand, the definition of talent is mighty challenging due to the fact that it is likely partly learnt, taught and in our DNA. Secondly, the talent can be seen as a multifactorial entity. As an example, a recent study by Tomita et al. (2020) found that the ratio of the tibial length to femoral length correlated significantly with the IAAF score in 400-m sprinters, which is anthropometrically a talent factor. Although, the same study found no correlation across the 100 m sprinters. Therefore, the theory is only speculative. Another example was demonstrated by Kohn, Essen-Gustavsson, & Myburgh (2007) where they found that South African endurance runners had more intermediate fast-twitch muscle fibres and fewer slow-twitch muscle fibres compared to their fellow Caucasian runners. A higher ratio of intermediate fast-twitch muscle fibers might indicate a higher degree of speed and power development potential compared slow-twitch dominant athletes. An additional talent dimension is genetics and the behavioral science. Temperament and behavior have been found to be partly genetical and partly nurtured through environmental factors (Bratko, Butkovic, & Hlupic, 2017). Anyhow, although the multifactorial nature of talent and its identification is an interesting area, however, it is also beyond the scope of this article and therefore will not be discussed in detail.

In summary, whereas a hard work ethic of an athlete and smart coaching are vital elements of the performance, there is some evidence that all the factors that lead to success may not be in our hands. On the other hand, the findings aren’t all straightforward and consistent, and therefore it is interesting to see what the future holds in the field of sports genomics. Secondly, it seems that a single gene may not be the gold medal-winning recipe, but instead the gene interaction and genotype variances among the population, which was also noted by Ahmetov et al. (2016). Lastly, some food for thought, the field of elite sports discusses broadly about the individualistic approach from an athlete and planning point of view. On the other hand, human DNA is 99,9 % identical; thus, it could be questioned how individually tailored the training plan should be, 0,1 % or 50 %. That is obviously black and white thinking and should not be read literally, due to the fact that the sport-specific needs, age related factors are the base foundation of any training plan and make a substantial difference on why a distance runner is trained differently compared to an ice hockey player. Last but not least, it should be noted that the author of the article is not an expert in the field of gene biology, which should be taken into account when drawing conclusions. The main purpose of this article was just to scratch the surface of complex gene biology and translate it into simplified language.

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