The Speedy Secret in Your DNA

If you've ever marveled at the incredible speed of Olympic sprinters like Usain Bolt, you might wonder what gives them their exceptional abilities. While rigorous training, diet, mental toughness, and access to top-notch facilities all play significant roles, the answer might also lie within their DNA. Our DNA contains genes, which are like instructions for our bodies, telling them how to grow, develop, and function. Think of genes as tiny recipe cards inside each cell that guide everything from eye color to how our muscles work.

One gene in particular, the alpha-actinin- 3 (ACTN3) gene, often dubbed the "gene for speed," has a significant influence on muscle performance and athletic capability. However, understanding the interactions between genetics and athletic performance is a complex task. It's not just a single gene that dictates one's ability to run fast or sustain endurance but a combination of genetic predispositions and environmental factors. However, the ACTN3 gene stands out for its substantial influence on muscle function and athletic capability, offering insights into the biology of speed (Berman & North, 2010).

The Role of Genes in SPEEDY Muscle Performance

Genes contain the information that allows our cells to manufacture proteins, which are the building blocks of muscle skeleton. The ACTN3 gene gives instructions on how to make the protein alpha-actinin-3. This protein is found in fast-twitch skeletal muscle fibers, special muscles that help us move quickly and powerfully. Alpha-actinin-3 helps these fast-twitch muscles by holding onto another protein called actin. Imagine actin as one side of Velcro and myosin as the other. When they stick together, your muscles contract or tighten, which makes you move. Alpha-actinin-3 makes sure that actin and myosin stick together extraordinarily well, allowing your muscles to contract more quickly and more powerfully (Eynon et al., 2012).

It's important to note that it's not just the presence of the ACTN3 gene that matters but the amount of alpha-actinin-3 protein it produces. Most of us, around 85%, have at least one R allele, meaning we can make some functional alpha-actinin-3 protein. However, the more alpha-actinin-3 you have, the better your muscles can perform quick, powerful movements. In summary, having more of this protein can help you be a better athlete, especially in activities that require speed and power (Berman & North, 2010).

What Are Genotypes?

Now, let's look at how genotypes affect alpha-actinin-3 levels. A genotype is a combination of different versions of a gene that you get from your parents. For the ACTN3 gene, there are three possible genotypes: RR, RX, and XX.

• RR Genotype: You get an R version from each parent and make a lot of alpha-actinin-3.

• RX Genotype: You get an R version from one parent and an X version from the other, so you make some alpha-actinin-3.

• XX Genotype: You get an X version from both parents and don't make any alpha-actinin-3.

Let's take a closer look at alpha-actinin 3 and why some athletes are better at sprinting and others at endurance sports. Imagine your muscles are like different types of engines in cars. Fast-twitch muscle fibers are like sports car engines that can go really fast but use a lot of fuel quickly. Alpha-actinin-3 is like a special turbocharger that makes these engines (muscles) even faster and more powerful. If you have the RR or RX genotype and thus make alpha-actinin-3, as mentioned before, your muscles are like sports cars with turbochargers, helping you run really fast for a short time, as sprinters do. Alpha-actinin-3 is primarily found in these fast-twitch muscle fibers responsible for quick, powerful movements. These fast-twitch fibers are great for sprinting because they contract quickly and forcefully (Coso et al., 2018).

Looking back, fast-twitch muscle fibers also tire out quickly. So, on the other hand, slow-twitch muscle fibers are like the engines in hybrid cars. They don't go as fast but can run long without getting tired. Slow-twitch fibers are more efficient at using energy over long periods, which makes them ideal for endurance activities like marathon running. Without alpha-actinin-3, fast-twitch muscle fibers are less effective at producing quick, powerful movements and still tire out quickly. On the other hand, slow-twitch muscle fibers, which are naturally better at endurance, don't rely on alpha-actinin-3 to the same extent and remain efficient for long-duration activities regardless of the presence of this protein (Broos et al., 2016). Thus, athletes with the RR or RX genotypes excel in sports requiring quick bursts of power, while those with the XX genotype, who lack alpha-actinin-3, are better suited for endurance sports (Eynon et al., 2012).

Training, Recovery, and Injury Risk

The ACTN3 gene doesn’t just influence our speed; it also affects how well muscles respond to training and recover after exercise. Athletes with the RR or RX genotypes who make alpha-actinin-3 often find their muscles getting stronger and more powerful with training than those without alpha-actinin-3. This is likely because alpha-actinin-3 helps protect fast-twitch muscle fibers from getting damaged during intense exercise. When you exercise, your muscles work very hard and can get tiny tears or damage. Alpha-actinin-3 helps make the muscles stronger by providing structural integrity, helping them withstand the stress of intense physical activity, and reducing muscle wear and damage. This means that people with alpha-actinin-3 can train harder, and their muscles can recover and get stronger more quickly (Guth & Roth, 2013). On the other hand, athletes with the XX genotype, who don't make alpha-actinin-3, might need to be more careful. Their muscles can get damaged more easily during hard workouts and take longer to heal. This means they might need to spend more time resting and doing exercises that help prevent injuries (Berman & North, 2010).

From Mice to Medalists: Research Insights

In a fascinating study, researchers used genetically modified mice to delve deeper into the effects of the ACTN3 gene. Mice lacking alpha-actinin-3 exhibited a shift toward using more energy-efficient muscle processes, enhancing their endurance capacity. However, this increased endurance came at the cost of reduced sprinting capabilities, suggesting that the absence of alpha-actinin-3 might provide an endurance advantage while compromising explosive power (Berman & North, 2010).

Human studies have also explored the relationship between the ACTN3 gene and athletic performance. For instance, a study involving elite European athletes, including many Olympic medalists, found that sprinters were significantly less likely to have the XX genotype compared to the general population. This data suggests a possible correlation between the presence of the R allele (RR or RX genotype) and enhanced power and speed events performance. The under-representation of the XX genotype in elite sprinters highlights the potential importance of alpha-actinin-3 in athletic performance (Eynon et al., 2013).

The Marathoner and the Sprinter

To put this into perspective, consider two famous athletes: Usain Bolt and Kelvin Kiptum. Usain Bolt is known for his incredible sprinting speed and holds the world record for 100 meters. Kelvin Kiptum is a legendary long-distance runner and the current world record holder in the marathon. Bolt, with his explosive speed and power, likely benefits from having the R version of the ACTN3 gene, making his muscles more efficient for quick, powerful movements. On the other hand, Kiptum excels in long-distance running, suggesting he might have the XX genotype, which favors endurance. Understanding these differences helps explain why they are so good at their respective sports.

Conclusion

The ACTN3 gene plays a significant role in athletic performance, especially in speed and power activities. Knowing your ACTN3 genotype can provide valuable insights for creating personalized training plans that match your genetic predispositions. This can enhance performance and reduce the risk of injuries. However, genes are just one piece of the puzzle. Training, diet, mental toughness, and access to quality coaching and facilities are also crucial for success.

So, the next time you're thinking about picking up that hobby of becoming a competitive runner, consider checking your genotype and alpha-actinin-3 protein levels. Understanding your protein levels can help you choose the right events and training routines, preventing burnout and injuries. This personalized approach to training can optimize your performance and keep you healthy. And if you're not destined to be the next Usain Bolt, don't worry! Even the fastest runners started by learning to walk, so lace up those shoes, hit the track, and have fun! Who knows? You might just discover your hidden speed superpower!

Written by Jacob Tuazon and edited by Aldrin V. Gomes, PhD

 

References:

Berman, Yemima, and Kathryn N. North. “A Gene for Speed: The Emerging Role of α-Actinin-3 in Muscle Metabolism | Physiology.” American Physiology Association, 1 Aug. 2010, 25:4, 250-259. https://journals.physiology.org/doi/full/10.1152/physiol.00008.2010

Broos, Siacia, et al. “Evidence for ACTN3 as a Speed Gene in Isolated Human Muscle Fibers.” PloS One, 2016; 11(3): e0150594. www.ncbi.nlm.nih.gov/pmc/articles/PMC4773019/

Coso, Juan Del, et al. More than a ‘Speed Gene’: ACTN3 R577X Genotype, Trainability, Muscle Damage, and the Risk for Injuries. European Journal of Applied Physiology. 2019. 119: 49-60. https://link.springer.com/article/10.1007/s00421-018-4010-0

Eynon, Nir, Erik D. Hanson, et al. Genes for Elite Power and Sprint Performance: ACTN3 Leads the Way - Sports Medicine. 2013, 43(9), 803–817. https://pubmed.ncbi.nlm.nih.gov/23681449/

Eynon, Nir, Jonatan R. Ruiz, et al. “The ACTN3 R577X Polymorphism across Three Groups of Elite Male European Athletes.” PLOS One, 2012, 9(3): e93165. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0043132

Guth, Lisa M., and Stephen M. Roth. Genetic Influence on Athletic Performance. Current Opinion in Pediatrics. 2013, 25(6): 653-658. https://journals.lww.com/co-pediatrics/fulltext/2013/12000/genetic_influence_on_athletic_performance.4.aspx