Nutrigenomics
What ACTN3 and ACE are linked with, how small those links are for one person, what studies say about injury, and what a fitness DNA test can’t do.
By the GeneMatrix editorial teamUpdated 5 min read
In short
ACTN3 and ACE are the best-studied exercise genes. Some of their versions turn up a little more often in elite sprint or endurance athletes than in other people, but the links are small and don’t always repeat. No gene result can pick your sport, measure your ability or predict an injury. It’s something to talk over with your coach, not a training plan.
On this page
What are fitness genes?
Athletic performance depends on many traits, such as muscle strength, the mix of fiber types in your muscles and how much oxygen your body can use. Both your genes and your surroundings shape them.[1]
Muscles have two main kinds of fiber. Slow-twitch fibers contract slowly but can keep going for a long time. Fast-twitch fibers contract quickly but tire fast.[1] The two best-studied fitness genes, ACTN3 and ACE, are both linked with that split between speed and endurance.
What is the ACTN3 gene?
A common variant called R577X leads to a short version of the protein that is quickly broken down. People with two copies of the X version, the XX pattern, make no alpha-actinin-3 at all.[1] In one study, about 18% of healthy white people had this pattern. A related protein, alpha-actinin-2, is thought to fill in for it.[2]
| Pattern | What it means | What studies have found |
|---|---|---|
| RR | Two copies of the R version. Your muscles make alpha-actinin-3. | Seen more often in athletes who rely on speed or power, such as sprinters.[1] Elite sprinters carry the R version more often than non-athletes.[2] |
| RX | One copy of each version. | Mixed. In one study, female sprinters had more RX and female endurance athletes fewer than expected, with no such pattern in men.[2] |
| XX | Two copies of the X version. No alpha-actinin-3 is made.[1] | More common in endurance athletes in some studies, but not in others.[1] |
Our nutrition, supplement, athletic and wellbeing reports are for general wellness and information. The evidence behind these associations is less established than for our clinical panels, and these reports are not intended to diagnose, treat, cure or prevent any disease.
What does the ACE gene do?
ACE makes angiotensin-converting enzyme, which turns a hormone called angiotensin I into angiotensin II.[1] A common variant is a short stretch of DNA that is either there (I, for insertion) or missing (D, for deletion). That gives three patterns: II, ID and DD.[1]
The D version is linked with higher enzyme activity and with sprint and power events, and the I version with endurance.[1][3] In a 2013 pooled analysis of 25 studies, athletes in endurance events had about 1.35 times the odds of the II pattern compared with non-athletes, but results varied from study to study.[3]
How much do these genes matter for one person?
Family studies suggest that genes account for somewhere between 30 and 80 percent of the differences between people in traits related to athletic performance. That share is spread across a large number of genes, each making only a small contribution.[1]
More than 150 variants have been linked with athletic performance, but most have been found in only one or a few studies, and what most of them do isn’t yet known.[1]
The links that do repeat mostly come from comparing elite athletes with non-athletes. They describe groups, not what you can do. Plenty outside your genes matters too, from support from family and coaches to money, access to facilities and even how old you are compared with others in your age group.[1]
A gene that turns up a little more often in elite sprinters can’t tell you how fast you’ll be.
Can genes predict sports injuries?
Not today. Researchers have studied genes involved in collagen, the protein that gives tendons and ligaments their strength, such as COL1A1 and COL5A1, along with genes like MMP3 that help remodel tissue. Some studies link certain variants with ligament tears, tendon problems or stress fractures in athletes and other active people.[4]
The evidence is early. A 2026 review of 26 studies, with more than 7,000 people in all, found that most studies were small and mostly of people of European ancestry, and concluded that larger, more diverse studies are needed before these links can be used.[4] A gene result can’t tell you whether you’ll get injured.
What do sports scientists say about DNA fitness tests?
In a 2015 consensus statement, sport and exercise genetics researchers wrote that genetic tests have no role in picking out talented athletes or in tailoring training to maximize performance. They added that no child or young athlete should have a direct-to-consumer genetic test to shape their training or to spot talent.[5]
That is how we treat a fitness trait report: something to read with curiosity and talk over with your coach, not a way to choose a sport or write a training plan.
What a fitness gene result can’t tell you
- It can’t pick your sport or measure your ability. The links come from groups of athletes, and they are small.[3]
- It can’t predict an injury. The research on injury genes still needs confirming in larger studies.[4]
- It isn’t a training plan. Sport genetics researchers say genetic tests have no role in tailoring training.[5]
- Findings can differ by ancestry. Studies of ACTN3 in Asian and African athletes haven’t always matched those in European athletes.[3]
- Genotyping reads selected variants. A genotyping test checks variants chosen in advance, so it can miss others.
How GeneCore reads fitness traits
- Fitness sits beside diet and everyday health. GeneCore reads these traits from one saliva sample and sets them side by side in one report.
- The fitness part. Selected variants studied in training response, recovery and soft-tissue injury.
- Your result and what research links it to. In plain language, for general wellness and information. It won’t tell you how to train.
- Fitness only? GeneSport reads the fitness area on its own. Every one of our DNA nutrition and fitness tests is on one page.
Our nutrition, supplement, athletic and wellbeing reports are for general wellness and information. The evidence behind these associations is less established than for our clinical panels, and these reports are not intended to diagnose, treat, cure or prevent any disease.
What to do next
Curious about your traits? Read what nutrigenomics is, see what your DNA can say about food, or find the test that fits you.
Sources
- [1]Is athletic performance determined by genetics?. MedlinePlus Genetics, U.S. National Library of Medicine. Accessed .
- [2]ACTN3 genotype is associated with human elite athletic performance. American Journal of Human Genetics, 2003. Accessed .
- [3]The association of sport performance with ACE and ACTN3 genetic polymorphisms: a systematic review and meta-analysis. PLoS ONE, 2013. Accessed .
- [4]The role of COL1A1, COL5A1, ACTN3, MMP3, and GDF5 gene variants in common sports injuries: systematic review of ACL rupture, Achilles tendinopathy, and stress fractures. Genes, 2026. Accessed .
- [5]Direct-to-consumer genetic testing for predicting sports performance and talent identification: consensus statement. British Journal of Sports Medicine, 2015. Accessed .
How we write and source these pieces: our editorial policy.
Related reading
- Is there a DNA test for weight loss? What trials found, and what a DNA diet test can describeIs there a DNA test for weight loss? What the trials found.Updated October 1, 2026
- What is nutrigenomics? A plain-English guide to your genes and foodHow differences in your genes relate to the way your body handles food, and where the evidence stops.Updated October 1, 2026
