ACTN3 is the world’s most famous ‘gene for speed’. This gene encodes for α-actinin-3, a protein that has been linked to greater baseline strength, a protective effect against muscle damage, and an increase in fast-twitch muscle fibres. One particular version of ACTN3 has been found in almost every Olympic sprinter ever tested. Your FitnessGenes result will tell you if you carry the ‘sprinter’ version, the version linked to endurance or both.


There are two different versions of the ACTN3 gene that we analyse for you: the R version and the X version.

Associated with greater muscle strength and power, one particular version of this gene — the R version — has been found in almost every single Olympic 100m runner ever tested. An association has also been observed between the XX genotype and endurance capability, although this link does not appear to be as strong.

Global population distribution:

Source: 1000 Genome Project.  Global averages for both sexes

ACTN3: RR

38%

ACTN3: RX

44%

ACTN3: XX

18%

Need help choosing a plan?

Use our Plan Advisor to determine which genetically tailored diet and exercise program best fits your needs.

Find out