Genes determine almost nothing, but they condition almost everything. Your observable abilities and traits are influenced by the genetic legacy of your ancestors, from your intelligence to your political inclinations ( article , study ).

Some time ago we saw that knowing our genome can help us customize our diet ( article ). Today we will perform the same analysis in the sports field. Using my own genes as an example, we will explore the impact of our genetic code on performance, but also on the risk of injury and supplementation strategies.


Multiple aspects influence your predisposition to perform better in explosive tests of short duration or in long aerobic activities such as a marathon.

In this regard, the famous ACTN3 gene , which expresses its protein in fast muscle fibers (or type II), enhances its capacity for transmitting force ( meta-analysis , study , study , study ). Depending on your specific polymorphism , you may have inherited two active copies (one from your father and one from your mother), one active and one inactive or both of you silenced.

The vast majority of the great explosive athletes, from weightlifters to sprinters, have the active version, giving it the colloquial name  of the speed gene .

The inactive version (silenced copies of the father and the mother) favors, on the contrary, the performance in resistance tests , and it seems that this variant evolved especially in areas with less food ( study ), where energy efficiency was more relevant to cover greater distances Looking for food.

Of course it takes much more to be a speed champion than a good version of this gene . Many other genes and factors influence your strength / endurance profile ( study , study , study ), placing you at some point in a broad spectrum .

In my case, I have for example the “explosive” version of the ACTN3 gene, being closer to the Strength / Power end. It is no surprise. I always had good vertical jump and I was good at speed , while I hated long distance.

They also influence many other anatomical factors (also inherited in part), such as knees and symmetrical ankles ( study , study ) or percentage of muscle fibers that you have of each type, which we explore below.


Slow fibers (type I or red): Your favorite fuel is fatty acids, which oxidize easily thanks to their high mitochondrial density . They are very resistant to fatigue but take their time to produce energy, hence they have little explosive capacity.

Fast Fibers (type II or white): They mainly use glycogen and phosphocreatine , fuel that is not very energy efficient but capable of producing strength quickly. The price of this explosiveness is that they tire easily.

We have a combination of slow and fast fibers in all muscles, but there is great individual variability. Marathoners have many more slow fibers than sprinters.

Although the genetic factor is the most important ( detail ), the type of training you do determines in part the resulting fiber distribution ( study , study ). Long-term aerobic training favors slow fibers, and fast-strength ones. If you want the body of a sprinter, you must train like a sprinter .

The athlete on the left only runs a long distance. The one on the right makes heptathlon: 200 and 800 m races and 100 m hurdles, high and long jump, shot put and javelin.


Rapid fibers have a greater potential for hypertrophy , but muscle gain depends on many other genetic factors, for example related to the activation capacity of satellite cells.

In my case, the muscle gain potential is moderate, and it also fits with my experience. I only had good results when I started to program well and prioritize the right exercises.


Dozens of genes are known that influence the risk of different lesions ( study , study ), highlighting those related to the production of collagen , the main protein of bones and connective tissue.

For example, the COL1A1 gene is one of those responsible for the synthesis and structure of collagen, and the combination TT (a T allele inherited from the father and another from the mother) is associated with a lower risk of anterior cruciate ligament injuries .

Luckily, I have this combination, and maybe in part because of this I have never suffered this injury. I touch wood. This variant also seems to protect from Achilles tendon ruptures and dislocations.

Another interesting gene is Col5A1 , where the CC combination is associated with better flexibility and lower risk of tendon injury . In this case I have not been so lucky (I am CT), and in fact flexibility has never been my specialty.

Although to a lesser extent, another protein is also relevant:  elastin, which gives elasticity to the hard collagen fibers . Elastic ligaments are more resilient than rigid ones, reducing the risk of injury. The AA version is associated with an increased risk of injury and GG with less. Mine is AG, conferring a medium risk ( study ).

Although muscle injuries are usually less severe than joint injuries, there are also multiple variants associated with different risks ( study ,  study , study ), such as these two:


I have spoken on multiple occasions of the most effective supplements, such as creatine and caffeine . But again your genes influence its effect ( detail ).

People with less fast fibers will experience less benefits of creatine at the muscle level ( study ), and this depends in part on the active version of the sprinter gene (ACTN3).

On the other hand, the CYP1A2 gene determines the capacity to metabolize caffeine, and the rapid metabolizers (genotype AA) obtain benefits not available for the rest ( study ).


This is the one million question. It is one thing to find correlations between genes and different aspects of performance, and quite another to be able to take advantage of that information to effectively perform better . In this area, the evidence is still very scarce.

A good example of the future potential of this technology is a  recent study , which used fifteen genes to determine the profile of each athlete (strength / power or endurance), then evaluated their response to two training approaches: high intensity and low intensity.

Both groups (genetic profile of strength / power and endurance), completed the training sequentially, evaluating the final improvements in various performance metrics.

The final conclusion is that the groups improved more when they were assigned to the training that corresponded to their original genetics.

Although it is an interesting and well controlled study (it used randomization and double blind), its practical application is limited . In addition, they did not evaluate  strength gains or muscle mass , a relevant aspect for many.


If you have been training for a while, surely a genetic test will only confirm your intuitions. Even if you get some surprise, it’s difficult to give you something practical:

Even if you have a resistance profile, you will benefit from training strength and power .

Even if your risk of injury is lower, you should continue improving your mobility  and paying attention to the technique.

Whatever your muscular potential, you must apply the same rules to develop it .

Even if you do not respond muscularly to creatine, it may benefit you in other ways .

Also,  for each supposed genetic rule,  you will always find some exception . Do you remember the famous explosivity gene? As a Spanish athlete jumped 8.23m without him ( detail ).

Genes are very relevant, but we are far from deciphering their mysteries. We ignore many complex relationships, both between the genes themselves and between them and the environment in which they develop. Today, we know much better the impact of our actions, and we must focus our efforts on making better decisions.

Note: If you also want to explore your DNA, there are multiple options. I did the initial test with 23andMe , and then I used the sports analysis of DNAactive .


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