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Is athletic performance determined by genetics?
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Traits

Is athletic performance determined by genetics?

Athletic performance is a complex trait influenced by a combination of genetic factors and environmental circumstances.

Overview

Athletic performance is a multifaceted trait shaped by both genetic and environmental influences. Physical ability is primarily determined by the strength of muscles used for movement and the predominant type of fibers that compose them. Skeletal muscles consist of two primary types of fibers:

  • Slow-twitch fibers: These contract slowly but can function for extended periods without tiring, making them ideal for endurance activities like long-distance running.
  • Fast-twitch fibers: These contract quickly but tire rapidly, providing the power and strength required for sprinting and explosive movements.

Other key traits contributing to athleticism include aerobic capacity (the maximum amount of oxygen the body can deliver to tissues), muscle mass, height, flexibility, coordination, intellectual ability, and personality.

The Role of Genetics

Research involving families and twins suggests that genetic factors underlie 30 to 80 percent of the differences in traits related to athletic performance. While many genes have been studied, the most prominent are ACTN3 and ACE.

ACTN3 Gene

The ACTN3 gene provides instructions for the protein alpha (α)-actinin-3, found primarily in fast-twitch muscle fibers. A variant known as R577X results in an abnormally short protein that is quickly broken down. Individuals with the 577XX genotype lack this protein entirely, which appears to increase the proportion of slow-twitch fibers. Conversely, the 577RR genotype is associated with a higher proportion of fast-twitch fibers, often seen in athletes who rely on speed and strength.

ACE Gene

The ACE gene produces angiotensin-converting enzyme, which regulates blood pressure and may influence skeletal muscle function. The ACE I/D polymorphism results in three patterns: II, ID, and DD. The DD pattern is associated with the highest levels of the enzyme and is linked to a higher proportion of fast-twitch muscle fibers and greater speed.

Genome-Wide Research

Beyond specific genes, researchers use genome-wide association studies (GWAS) to identify variations across the entire genome. While more than 150 variations have been linked to athletic performance, most have only been identified in a limited number of studies. It is likely that a vast number of genes contribute, each providing only a small influence on overall athletic ability.

Environmental Influence

Athletic excellence is also strongly shaped by the environment. Key factors include:

  • Support from family and coaches.
  • Economic circumstances and access to resources.
  • Relative age compared to peers.

Because genes and environment interact, it is often difficult to distinguish their individual effects. For example, when a parent and child both excel at a sport, it is likely due to a combination of inherited genetic factors and shared environmental influences.

Frequently Asked Questions

Research indicates that genetic factors account for approximately 30 to 80 percent of the variation in traits related to athletic performance, such as aerobic capacity and muscle fiber type. This means that while your genes set the baseline for your potential, the remaining 20 to 70 percent is influenced by environmental factors, primarily your training regimen, nutrition, sleep, and recovery. This highlights that while you may have a genetic ceiling, consistent and optimized training is the primary driver of your actual performance levels.
No, having the 577XX genotype, which is associated with a higher proportion of slow-twitch fibers, does not mean you should avoid strength training. It suggests you may have a natural advantage in endurance activities where efficiency and fatigue resistance are key. However, slow-twitch fibers still respond to resistance training, and you can build significant strength and muscle mass. The key is to tailor your training volume and recovery periods to match your physiological profile, potentially prioritizing higher-repetition, lower-weight exercises for hypertrophy and endurance, while still incorporating heavy lifts for functional strength.
While genetic tests can identify variants in genes like ACTN3 and ACE that influence muscle fiber composition, they cannot definitively predict your athletic potential. These genetic markers are only one piece of the puzzle; your actual performance depends heavily on training history, nutrition, cardiovascular health, and psychological factors. A test showing a high proportion of fast-twitch fibers suggests a physiological advantage for explosive power, but it does not guarantee elite-level success without dedicated, structured training.
No, identical twins do not always have the same athletic abilities or preferences. While they share the same DNA, which provides a similar physiological baseline, differences in their individual training histories, injuries, nutrition, and psychological motivations can lead to significant variations in their performance. For example, one twin might excel in a sport requiring endurance while the other excels in a sport requiring power, even if their genetic profiles are identical.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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