Can you outwork the genius?

bxgenetics
Jun 12
3 min read

BY JOANNA XU

Endurance performance in athletes is shaped by both environmental and genetic factors. Among the most studied genes in this context are ACTN3 and ACE, which influence muscle function and cardiovascular efficiency, respectively. The ACTN3 gene contains a common R577X polymorphism: individuals with the XX genotype lack the fast-twitch muscle protein α-actinin-3, which is associated with better endurance capacity. A study by Yang et al. (2003) found that 35% of elite endurance athletes had the XX genotype, compared to just 5% of elite sprinters.

The ACE gene, which affects blood pressure and oxygen delivery, has an I/D polymorphism. The II genotype is more prevalent in endurance athletes, as shown in a meta-analysis by Ma et al. (2013), which reported that it increased the odds of being an elite endurance performer by 35%.

While these genetic traits can offer physiological advantages, they do not solely determine success. Environmental factors, training, and determination play significant roles. Genetics may help identify natural predispositions, but they should not be used to define limitations. As genetic research advances, ethical considerations will be vital in applying this knowledge responsibly in sports science.

3.1 ACTN3 Distribution Among Athletes

Group	RR (%)	RX (%)	XX (%)
Elite sprinters	45	50	5
Elite endurance	20	45	35
General population	30	50	20

Source: Yang et al., Nature Genetics (2003)

The data show that XX genotypes are significantly more common in elite endurance athletes, while rare in sprinters.

3.2 ACE Genotype and Endurance

A meta-analysis by Ma et al. (2013) in PLOS ONE reviewed over 30 studies involving elite athletes:

II genotype showed a 1.35x increased odds of being found in endurance athletes compared to non-athletes.
Distribution in endurance runners:
- II: 40%
- ID: 45%
- DD: 15%

Discussion

These genetic differences contribute to physiological traits such as:

ACTN3 XX: More slow-twitch muscle fibers, fatigue resistance.
ACE II: Lower ACE activity, better vasodilation, oxygen delivery.

However, while the correlations are strong at population levels, they do not guarantee success. For example, many elite performers have “non-ideal” genotypes, emphasizing that training and environment still dominate in importance.

Implications

Personalized training: Genetic testing could guide athletes to sports they’re genetically suited for.
Ethical concerns: Genetic profiling for talent identification raises issues of equity and determinism.
Future research: Large-scale genome-wide association studies (GWAS) can further identify gene clusters affecting performance.

Conclusion

Genetic factors, especially variations in ACTN3 and ACE, play a measurable role in endurance capacity. While these traits offer a biological advantage, they are just one component of athletic achievement. Integrating genetic data into training must be done cautiously and ethically, emphasizing potential rather than limitation.

Yang, N. et al. (2003). ACTN3 genotype is associated with human elite athletic performance. Nature Genetics, 34(2), 168–170.

Ma, F. et al. (2013). The ACE gene polymorphism and athletic performance: A meta-analysis. PLOS ONE, 8(1), e54685.

Pickering, C. & Kiely, J. (2017). ACTN3: More than just a gene for speed. Frontiers in Physiology, 8, 1080.

Jones, A., & Montgomery, H. (2002). ACE genotype and human performance: A story of evidence and evolution. Medicine & Science in Sports & Exercise, 34(5), 868–872.

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