You are viewing Brian Gallagher's 23andMe Wellness report.

Muscle Composition

Sprinters and endurance athletes differ in the composition and the capabilities of their muscles. These differences may be influenced by both training decisions and genetic factors.

Your Wellness Result

Brian, your genetic muscle composition is common in elite power athletes.

Studies have found that almost all elite power athletes (including sprinters, throwers, and jumpers) have a specific genetic variant in a gene related to muscle composition. You have the same genetic variant as these elite athletes.

What this means for you

For most people, lifestyle and training factors drive athletic performance. At the national and international levels of competition, the genetic variant in this report seems to make a difference in athletic success, but its role for non-elite athletes isn't completely understood.

Genetics and Muscle Composition

What's in a muscle?

Our muscles are made up of two main types of fibers, called slow-twitch and fast-twitch. Fast-twitch fibers allow rapid, forceful muscle contraction — the sort of contraction required for sprinting. Slow-twitch fibers contract more slowly, but they also tire less easily. Endurance athletes tend to have more slow-twitch fibers, while power athletes (including sprinters, throwers, and jumpers) tend to have more fast-twitch fibers — a difference that may reflect both their genetics and their training habits.

Muscles and genetics

This report is based on a genetic marker in the ACTN3 gene. This marker controls whether muscle cells produce a protein (called alpha-actinin-3) that's found in fast-twitch muscle fibers. While some people don't produce this protein at all, almost all of the elite power athletes who have been studied have a genetic variant that allows them to produce the protein. This suggests that the protein may be beneficial at least at the highest levels of power-based athletic competition.
  Genetic result What it means
CC
Common result for elite power athletes
You
CT
Common result for elite power athletes
TT
Uncommon result for elite power athletes
See the percentage of customers with these results
Genetic results of 23andMe customers by ancestry
Genetic result European African East Asian Latino South Asian
CC

Common result for elite power athletes

31.2% 61.5% 30.2% 24.0% 15.8%
CT

Common result for elite power athletes

49.3% 33.7% 49.3% 49.0% 47.6%
TT

Uncommon result for elite power athletes

19.4% 4.8% 20.5% 27.0% 36.6%
CC

Common result for elite power athletes

European African East Asian Latino South Asian
31.2% 61.5% 30.2% 24.0% 15.8%
CT

Common result for elite power athletes

European African East Asian Latino South Asian
49.3% 33.7% 49.3% 49.0% 47.6%
TT

Uncommon result for elite power athletes

European African East Asian Latino South Asian
19.4% 4.8% 20.5% 27.0% 36.6%

About endurance athletes

Most of the elite power athletes who have been studied have a genetic variant that allows them to produce the alpha-actinin-3 protein in their muscles. Does that mean that people who don't produce this protein are more likely to be endurance athletes? Studies in mice suggest that the answer may be yes: young mice who don't make any of this protein are able to run farther without getting tired. But studies in humans have not consistently shown an endurance advantage for people who don't produce the alpha-actinin-3 protein.

Genetics isn't everything

Differences in the genetic marker used in this report may only explain about 2-3% of the difference in muscle performance between different people. In elite athletes who work intensely to reach the upper limits of their potential, that 2-3% may mean the difference between qualifying for the Olympics and missing the cut. But for the rest of us, the choices we make about how to train will far outweigh the contribution of our genetic result at this marker.
This report does not diagnose any health conditions or provide medical advice. Consult with a healthcare professional before making any major lifestyle changes or if you have any other concerns about your results.
Read Scientific Details

Muscle composition is influenced by a genetic marker in the ACTN3 gene.

The ACTN3 gene contains instructions for making alpha-actinin-3, a protein found in certain types of fast-twitch muscle fibers. Some people have a non-functional variant of the ACTN3 gene and do not produce the alpha-actinin-3 protein. However, most of the elite power athletes who have been studied (including sprinters, throwers, and jumpers) have the functional ACTN3 variant and do produce this protein.

Chromosome 11
Gene: ACTN3

You have one copy of the C variant and one copy of the T variant.

Variants Detected
View All Tested Markers
Marker Tested
Genotype*
Additional Information

R577X

Gene: ACTN3
Marker: rs1815739

C

Typical copy from one of your parents

T

Variant copy from your other parent
See all information
See all information
Marker Tested
Your Genotype*

  • Biological explanation
    The marker we tested comes in two different forms: C and T. The T version is non-functional, which means the ACTN3 gene can't produce the alpha-actinin-3 protein. This marker has been studied the most in individuals of European descent.

  • Typical vs. variant DNA sequence(s)

    C

    Typical Sequence
    Substitution

    T

    Variant Sequence

  • Percent of 23andMe customers with variant
    Variant: T
    European 68.7%
    African American 38.5%
    Ashkenazi Jewish 69.0%
    East Asian 69.8%
    Hispanic or Latino 76.0%
    South Asian 84.2%
    Middle Eastern 70.2%

  • References [ 1, 3, 4, 7, 11, 15 ] ClinVar
View All Tested Markers
Marker Tested
Your Genotype*
Additional Information

R577X

Gene: ACTN3
Marker: rs1815739

C

Typical copy from one of your parents

T

Variant copy from your other parent
See all information
See all information
Marker Tested
Your Genotype*

  • Biological explanation
    The marker we tested comes in two different forms: C and T. The T version is non-functional, which means the ACTN3 gene can't produce the alpha-actinin-3 protein. This marker has been studied the most in individuals of European descent.

  • Typical vs. variant DNA sequence(s)

    C

    Typical Sequence
    Substitution

    T

    Variant Sequence

  • Percent of 23andMe customers with variant
    Variant: T
    European 68.7%
    African American 38.5%
    Ashkenazi Jewish 69.0%
    East Asian 69.8%
    Hispanic or Latino 76.0%
    South Asian 84.2%
    Middle Eastern 70.2%

  • References [ 1, 3, 4, 7, 11, 15 ] ClinVar

*This test cannot distinguish which copy you received from which parent. This test also cannot determine whether multiple variants, if detected, were inherited from only one parent or from both parents. This may impact how these variants are passed down.

23andMe always reports genotypes based on the 'positive' strand of the human genome reference sequence (build 37). Other sources sometimes report genotypes using the opposite strand.

References

  1. Alfred T et al. (2011). "ACTN3 genotype, athletic status, and life course physical capability: meta-analysis of the published literature and findings from nine studies." Hum Mutat. 32(9):1008-18.
  2. Berman Y and North KN. (2010). "A gene for speed: the emerging role of alpha-actinin-3 in muscle metabolism." Physiology (Bethesda). 25(4):250-9.
  3. Druzhevskaya AM et al. (2008). "Association of the ACTN3 R577X polymorphism with power athlete status in Russians." Eur J Appl Physiol. 103(6):631-4.
  4. Eynon N et al. (2013). "Genes for elite power and sprint performance: ACTN3 leads the way." Sports Med. 43(9):803-17.
  5. Guth LM and Roth SM. (2013). "Genetic influence on athletic performance." Curr Opin Pediatr. 25(6):653-8.
  6. Lee FX et al. (2016). "How does α-actinin-3 deficiency alter muscle function? Mechanistic insights into ACTN3, the 'gene for speed'." Biochim Biophys Acta. 1863(4):686-93.
  7. Ma F et al. (2013). "The association of sport performance with ACE and ACTN3 genetic polymorphisms: a systematic review and meta-analysis." PLoS One. 8(1):e54685.
  8. MacArthur DG et al. (2007). "Loss of ACTN3 gene function alters mouse muscle metabolism and shows evidence of positive selection in humans." Nat Genet. 39(10):1261-5.
  9. MacArthur DG et al. (2008). "An Actn3 knockout mouse provides mechanistic insights into the association between alpha-actinin-3 deficiency and human athletic performance." Hum Mol Genet. 17(8):1076-86.
  10. Moran CN et al. (2007). "Association analysis of the ACTN3 R577X polymorphism and complex quantitative body composition and performance phenotypes in adolescent Greeks." Eur J Hum Genet. 15(1):88-93.
  11. See all references

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