Genetics, Genes, And Exercise Are The Blueprints For Building Muscle Strength And Size


Building muscle is a goal for many fitness enthusiasts and athletes. However, have you ever wondered why some people gain muscle more quickly than others? The answer may lie deep in our cells in the complex world of genetics. This article will explore the role of genetics in muscle building and unravel how our DNA can influence our physical fitness.

The genetic blueprint for muscle building

Genetics is the blueprint of every individual, dictating various aspects of our bodies, including muscle composition and potency for growth. Our genetic makeup influences two main types of muscle fibers: Type I and Type II. Type I fibers are endurance-oriented, while Type II fibers are more prominent, which gives muscles power and strength. Your genetic inclination towards one type over the other can significantly impact how your body responds to different types of training (Kraemer & Ratamess, 2004).

The role of myostatin

A key player in muscle growth is a protein called myostatin. This protein is involved in muscle growth and regulation of its size. Gene variations in myostatin can lead to differences in muscle size and strength. For instance, Schuelke et al. (2004) found that mutations resulting in lesser expression of myostatin cause significantly increased muscle mass.

Testosterone and genetics

Testosterone, the hormone well-known for its role in muscle building, is also influenced by genetics. Genes determine the quantity of testosterone produced and the muscles’ response to the hormone. This genetic variation explains why two individuals with similar training routines can still have different muscle growth rates (Kadi, 2008).

Testosterone molecule skeletal, Credit: Wikimedia/Jynto

The actn3 gene

Alpha-actinin-3 (ACTN3) is a gene expressed only in type II or fast-twitch muscle fibers, which are crucial for explosive strength. Some people have a variant of this gene that enhances their performance in power-based activities, while others do not (Yang et al., 2003).

Genetics vs. Environment

While genetics play a crucial role, it is essential to remember the influence of environmental factors like diet and exercise. No gene can magically build muscle without the proper training and nutrition. A balanced approach, recognizing the interplay between genetics and lifestyle, is vital to effective muscle building.

Genetic testing for fitness

With advancements in science, genetic testing for fitness is becoming more accessible. These tests provide insights into your muscle fiber composition and how you might respond to different types of exercise. However, taking these results as part of a larger picture, including personal goals and preferences, is essential (Pickering & Kiely, 2017).

A diagram of a human body
Central (cardiovascular) and peripheral (skeletal muscle) adaptations to exercise training, Credit; Wikimedia/John A. Hawley, Michael J. Joyner, Daniel J. Green

Limitations of current research

It is crucial to acknowledge the limitations of current research on the genetics of muscle building. Much of the research is in infancy, and our understanding of how multiple genes interact to influence muscle growth is limited. Future research promises to provide a more comprehensive picture.

Beyond genetics: the power of perseverance

While genetics play a significant role in muscle building, they are not the sole determinant. Hard work, consistency, and a well-structured training program can overcome genetic limitations. The power of perseverance and dedication will help in the quest for physical fitness.


The role of genetics in muscle building is a complex and fascinating topic. While our genes provide a framework for muscle power, they do not dictate its destiny. Understanding the genetic factors can help customize a more effective workout regime, but commitment and effort remain vital to achieving fitness goals. As we continue to unravel the mysteries of our DNA, the future of personalized fitness looks promising.


  • Smore Science Staff
  • Sai Sudha, Ph.D.
    Dr. Sudha Purushothaman with a Ph.D. in Biochemistry has been fascinated by writing for a long, long time. She researches metabolism and its role in pluripotency. Her commitment to research kept her away from writing. Finally, during the pandemic she became a full-time science writer. She strongly believes that curiosity-driven learning harnesses the cognitive skills. She considers that writing is a way of leaving your fossil behind. She enjoys creativity in writing and believes that every article must have a storyboard. She needs her daily dose of yoga and recommends yoga and meditation for neural connectivity. The prime attraction in writing and editing for Smore is the target audience, youngsters who need to be inspired to seek STEM as their career.

Copyright @smorescience. All rights reserved. Do not copy, cite, publish, or distribute this content without permission.

Join 20,000+ parents and educators
To get the FREE science newsletter in your inbox!