Blog/How to Interpret Your ACTN3 Result in Your Training Plan

How to Interpret Your ACTN3 Result in Your Training Plan

Published: October 6, 2026 · Author: Hub Gen (corporate content)

ACTN3 is one of the most studied genes in sports genetics and appears frequently in genetic reports. In this article, we explain what your ACTN3 result means, what research shows, and within which limits you can use this information in your training plan.

What is ACTN3?

The ACTN3 gene provides the instructions for making a protein called alpha-actinin-3. This protein is found only in fast-twitch (type II) muscle fibres. These fibres come to the fore in movements that require high force over a short time, such as sprinting and jumping.

The gene has a common variant known as R577X (rs1815739). The X allele causes the protein to be cut short. People who carry two copies of the X allele (XX) produce no alpha-actinin-3 at all. This is not a disease. A similar protein, alpha-actinin-2, largely compensates for the deficiency. In one population studied, about 18% of healthy individuals were reported to have the XX genotype.

What do RR, RX and XX mean?

  • RR: Two copies of the R allele. Alpha-actinin-3 is produced. In research, the R allele has been seen more often in power- and sprint-oriented athletes.
  • RX: One R and one X allele. Alpha-actinin-3 is produced.
  • XX: Two copies of the X allele. Alpha-actinin-3 is not produced. The XX genotype has been seen less often among elite sprinters. However, there are also athletes with the XX genotype who show top-level power and sprint performance.

What does research show?

Studies of elite athletes. In a study published in 2003, the R allele was found more often in both female and male elite sprinters than in the control group.

Meta-analysis. In a systematic review and meta-analysis published in 2013, no significant association was found between the RR genotype and performance when all sports were assessed together (odds ratio 1.03). The association was significant, and small, only when limited to power-oriented sports (odds ratio 1.21). In other words, ACTN3 is associated with only a small part of the differences in performance.

Link with muscle fibres. In a study of 90 young men, participants with RR who underwent a muscle biopsy had a higher proportion of fast-twitch type IIx fibres than those with XX. This suggests that the effect of ACTN3 may be linked to muscle fibre distribution. However, the way to measure fibre proportion is a muscle biopsy. A genetic test does not measure your fibre proportion; it only shows an associated variant.

Training adaptation and recovery. A review of 19 studies noted a "cautious consensus" that the R allele may be associated with greater strength gains and with protection against muscle damage from eccentric exercise. The same review also stresses that study results and participant groups differ widely from one another.

What does ACTN3 not tell you?

  • It does not tell you which sport you should do. The consensus statement of sports genetics researchers states that genetic tests have no role in talent selection or in personalised training prescriptions aimed at maximising performance.
  • On its own, it does not tell you how much you will respond to training. Large individual differences have been reported in the response to a standard endurance programme (increase in VO₂max), and the heritability of this response has been estimated at about 47%. This heritability is the sum of many genes and familial factors, not a single gene.
  • It does not measure your muscle fibre proportion. As noted above, fibre proportion can only be measured by biopsy.
  • It does not replace your training history, technique and consistent work. For most people, these factors are more decisive than genotype.

Using it cautiously in your training plan

The best way to use your ACTN3 result is as a starting hypothesis, which you can then test against your own data:

  1. Start from your goal. Your goal, not your genotype, determines the content of your training. Someone preparing for a running race trains endurance; someone with a strength goal trains strength.
  2. Use the result for fine-tuning. For example, someone with an RR or RX result might consider keeping short strength blocks during an endurance-focused phase. Someone with an XX result might monitor their recovery more closely after intense eccentric work (e.g. downhill running, heavy negative reps). These are suggestions for observation, not requirements.
  3. Measure and compare. Over periods of a few weeks, keep notes on performance tests, muscle soreness and recovery. If your data do not match the genetic prediction, trust your data.
  4. Share it with your coach. The result is useful as information that complements your coach's observations.

ACTN3 in the Hub Genetik report

The ACTN3 finding appears in the Sports & Fitness Genetics package, under the heading of muscle structure and power–endurance tendency, together with its evidence level and an actionable recommendation. The same headings are also included in the Sports & Health Analysis Package and the Sports & Skin Analysis Package. You can see what the card looks like in the sample report. How evidence levels are assigned is explained on the Science & Safety page.

References

  1. North KN, Yang N, Wattanasirichaigoon D, et al. A common nonsense mutation results in alpha-actinin-3 deficiency in the general population. Nat Genet. 1999;21(4):353-4. PMID: 10192379. doi:10.1038/7675
  2. Yang N, MacArthur DG, Gulbin JP, et al. ACTN3 genotype is associated with human elite athletic performance. Am J Hum Genet. 2003;73(3):627-31. PMID: 12879365. doi:10.1086/377590
  3. Ma F, Yang Y, Li X, et al. The association of sport performance with ACE and ACTN3 genetic polymorphisms: a systematic review and meta-analysis. PLoS One. 2013;8(1):e54685. PMID: 23358679. doi:10.1371/journal.pone.0054685
  4. Vincent B, De Bock K, Ramaekers M, et al. ACTN3 (R577X) genotype is associated with fiber type distribution. Physiol Genomics. 2007;32(1):58-63. PMID: 17848603. doi:10.1152/physiolgenomics.00173.2007
  5. Pickering C, Kiely J. ACTN3: More than Just a Gene for Speed. Front Physiol. 2017;8:1080. PMID: 29326606. doi:10.3389/fphys.2017.01080
  6. Bouchard C, An P, Rice T, et al. Familial aggregation of VO(2max) response to exercise training: results from the HERITAGE Family Study. J Appl Physiol. 1999;87(3):1003-8. PMID: 10484570. doi:10.1152/jappl.1999.87.3.1003
  7. Webborn N, Williams A, McNamee M, et al. Direct-to-consumer genetic testing for predicting sports performance and talent identification: Consensus statement. Br J Sports Med. 2015;49(23):1486-91. PMID: 26582191. doi:10.1136/bjsports-2015-095343
This article is for general information only; it is not a medical diagnosis or treatment recommendation.
‹ All articlesFind My Test