How Does DNA Affect Athletic Performance?

What does a genetic sports test actually look at?

A sports genetic test reads a small number of known variations in your DNA. These are spots where people commonly differ by a single letter or a small insertion or deletion. Researchers have studied whether those variations turn up more often in certain groups of athletes.

Most tests group their results into a few areas:

• Power and speed, for example ACTN3
• Endurance and oxygen delivery, for example ACE
• Connective tissue and injury tendency, for example COL5A1
• Recovery and muscle damage after hard exercise

Your result is a set of tendencies across these areas. It is not a score of how talented you are.

What is ACTN3, the so-called speed gene?

ACTN3 makes a protein called alpha-actinin-3, found only in fast-twitch muscle fibres, the ones used for sprinting and jumping. A common version of the gene, called X, stops the protein being made. People with two copies (XX) have none of it in their muscle, and that is completely normal. Around 18% of people of European descent and about 25% of people of Asian descent carry XX. ¹

In a 2024 meta-analysis of 25 studies and 14,541 people, power athletes were about 1.48 times more likely than non-athletes to carry the RR version, the one with two working copies. ² That is a real but modest association.

Some studies also link the XX version to more muscle damage after exercise that involves lengthening contractions, such as downhill running, though the evidence here is limited and the largest study found no link. ¹

What does the ACE gene have to do with endurance?

ACE is part of the system that helps regulate blood pressure and blood flow. It comes in an insertion (I) and a deletion (D) version. Research over more than a decade has linked the I version with endurance events and the D version with strength and power, though some findings conflict. ³

A meta-analysis found the II genotype was associated with endurance athletes, with an odds ratio of about 1.35. ⁴ In plain terms, II was somewhat more common among endurance athletes, not a requirement for being one. The review authors describe ACE as an important but limited factor in performance. ³

Can your genes affect injury risk?

This is one of the more practical areas of sports genetics. COL5A1 helps build a type of collagen found in tendons and ligaments. Variants in COL5A1 have been associated with chronic Achilles tendinopathy in two separate populations, in Australia and South Africa. ⁵

That does not mean a particular result will cause an injury. Tendon problems depend far more on training load, how quickly you build up, previous injuries and recovery. A collagen result is best read as a reason to be patient with progression, not a reason to worry.

What can the evidence tell you, and what can it not?

The honest answer is that sports genetics is good at describing groups and weak at predicting individuals.

What it can tell you

• Some variants are more common in elite power or endurance athletes than in the general population. ^{2 4}
• Certain variants are associated with tissue traits, such as tendon injury tendency or muscle damage after exercise. ^{1 5}
• Your result can add context to what you already notice in training, such as recovering slowly from eccentric work.

What it cannot tell you

• Whether you will become an elite athlete
• Which sport you should choose
• Exactly how you should train or eat
• Whether you will or will not get injured

Effect sizes for single genes are small, and athletic ability comes from many genes interacting with training, sleep, nutrition and opportunity. Plenty of elite sprinters carry the "wrong" ACTN3 version.

What do experts say about direct-to-consumer sports DNA tests?

In 2015, a group of leading sport and exercise genetics researchers published a consensus statement in the British Journal of Sports Medicine. ⁶ Their main conclusions were clear:

• Genetic tests have no role in talent identification or in prescribing individualised training to maximise performance.
• No child or young athlete should take these tests to shape their training or to select gifted young people.
• They raised concerns about some companies overstating the science, being unclear about which variants they test, offering little or no genetic counselling, and inconsistent quality control.

A later consensus update from the International Federation of Sports Medicine (FIMS) also stressed that genetic data in sport must be handled with strong ethics and data protection, to protect athletes' privacy. ⁷

These points are worth taking seriously when you choose a test and when you read your results.

How should you use your results sensibly?

Think of a genetic result as background biology. It can help explain what you see, but your actual performance data should lead your decisions.

• Pair it with real-world testing. A sprint, a jump or an aerobic test tells you where you are now. Your genes add the "why" behind it.
• Use injury-related results as a nudge, not a verdict. Build load gradually, warm up properly and take niggles seriously.
• Use recovery-related results to watch yourself more closely. If you seem to recover slowly, track sleep, soreness and session quality rather than assuming.
• Do not narrow your training. Work on your weaker areas as well as your strengths.
• Never use results to choose a sport for a child.
• Choose a provider that tells you exactly which variants it tests, how your data is stored, and how to get questions answered.

→ How to Train Smarter for Your Body
→ Why Recovery Matters for Performance

What can you do next?

If you are curious about the biology behind your training, a genetic test can add useful context, as long as you read it as tendencies rather than destiny. The Phenome Sports Performance Test looks at genes linked to power and endurance, oxygen delivery, recovery and connective tissue, so you can understand your body alongside the training data you already collect.

→ Explore the Sports Performance Test

For the wider debate on genetics and talent, and for practical training advice, read the articles below.

→ Are Athletes Born or Made? What the Science Says
→ How to Train Smarter for Your Body