What Are Calf Muscle Genetics? Good Vs Bad Calf Genetics

Have you ever stood at the starting line of a race and among the sea of bare legs, you spot beautifully-sculpted calves? Or perhaps you see guys or gals at your gym with calves that seem to pop out or bulge from the leg like when someone flexes their biceps.

For some people, it seems like no matter how much they run or workout, or how many heel raises they do, their calf muscles remain small and flat, while other people get big, defined calves with seemingly little effort.

What’s going on here? Are big calves genetic? What are calf muscle genetics? What are good calf muscle genetics? What are bad calf muscle genetics? Are bad calves genetic or can you get bigger calves if you work at them? 

In this guide, we will try to suss out fact from fiction with calf muscle genetics and good vs. bad calf genetics.

We will look at: 

  • What Are The Calf Muscles?
  • What Are Calf Muscle Genetics?
  • How Do Genetics Influence Calf Muscles?
  • Good Vs. Bad Calf Genetics
  • What Are Bad Calf Genetics?
  • What Are Good Calf Genetics?
  • What If I Have Bad Calf Muscle Genetics?

Let’s get started!

A close-up of calf muscles.

What Are the Calf Muscles?

The calf muscles, or calves, are technically called the gastrocnemius muscles. These muscles are found behind the lower leg, running from the back of the knee down to where they taper and connect to the heel in the Achilles’ tendon.

There are two distinct muscles that form what we typically refer to as the calves. The two-headed gastrocnemius, which is the larger muscle, and the soleus.

The gastrocnemius helps flex the knee and point the toe so that you can stand on tiptoes. It is involved in activities such as walking, running, and jumping.

The soleus is a smaller, thinner muscle that lies underneath the calf. It helps plantarflex the foot, and is involved in standing, walking, and running. 

What Are Calf Muscle Genetics?

Calf muscle genetics refers to the notion that your genetics at least partially influences the size and shape of your calf muscles. 

A close-up of calf muscles while running.

In other words, some people think that if you have small calves, it’s because of your genetics and no amount of training will really change that. Similarly, if you have big calf muscles, it’s because of your genetics, not your training. So, are big calves genetic or not?

There is limited scientific evidence to back the idea of calf muscle genetics. This theory is mostly based on our understanding of how genetics influence muscle growth in general and anecdotal and observational evidence of similar calf structures in family members.

How Do Genetics Influence Calf Muscles?

While “calf muscle genetics” may not be a valid concept per se, there is evidence to suggest that our genetics do influence muscle growth and size.

Muscle growth also referred to as hypertrophy, depends on numerous factors such as your hormonal profile, diet and nutrient availability, training stimulus, muscle fiber types, and muscle belly size.

Some of these factors are influenced by genetics, namely muscle fiber types, muscle belly size, and hormones to a lesser degree. 

Let’s look at muscle fiber type and muscle belly size as they pertain to muscle growth and potential calf muscle genetics.

Two people doing calf raises.

Muscle Fiber Type

Our skeletal muscles, such as the gastrocnemius and soleus, are composed of a couple of different types of muscle fibers, characterized by differences in properties such as muscle fiber size, mitochondrial density, the primary way in which the muscle fiber uses energy, and the type of contraction the fiber is capable of.

Although somewhat of an oversimplification, there are two primary types of muscle fibers in the calf muscles:

Type I Muscle Fibers

These can be thought of as endurance muscle fibers. They are smaller, contain many mitochondria, and generate energy aerobically (in the presence of oxygen). 

Type I muscle fibers are relatively fatigue resistant, so they can contract and power long-distance running, though their peak force output and the speed at which they can contract are lower and slower than Type II fibers.

Owing to the fact that Type I muscle fibers contract more slowly after receiving a neuromuscular impulse, they are referred to as “slow-twitch” muscle fibers. 

Type I muscle fibers are recruited during sustained exercise like marathon running and distance running in general.

A close-up of calf muscles while running.

Type II Muscle Fibers

Type II muscle fibers are known as “fast-twitch” muscle fibers. In contrast to Type I muscle fibers, Type II muscle fibers contract much faster and more forcefully. They are powerful but fatigue rapidly. 

Therefore, Type II muscle fibers are recruited for sprinting and high-speed, high-power activities like jumping and running uphill.

These muscle fibers are larger, contain very few mitochondria, and primarily generate energy through anaerobic (without oxygen) metabolism.

Nearly all of our muscles contain some of each type of muscle fiber, but the relative percentage of the fiber types that constitute the muscle varies based on factors such as your genetics, the muscle’s function, and the type of training you do. 

The soleus is an endurance muscle, so it is composed of nearly all Type I muscle fibers whereas the gastrocnemius is composed of a mix of both fiber types. Although training can influence the percentage of each fiber type, genetics also plays a significant role.

Type II muscle fibers are larger and more responsive to hypertrophy. Therefore, the higher the percentage of Type II muscle fibers you have, the greater your potential for visible muscle growth.

A close-up of calf muscles while running.

Muscle Belly Size

The muscle belly is the meaty portion of the muscle between its tapered tendinous attachments. The size of a muscle is somewhat limited by the size of the muscle belly. Muscles have a defined shape; they don’t just grow fibers in any direction.

Our genetics influences the size and shape of our muscle bellies. Those who have larger muscle bellies in the calves will have larger calf muscles whereas someone with calf muscles with a small muscle belly will have limited growth potential.

The size and shape of the calf muscles are also affected by the bone structure of the leg. If you have a long shin, the same muscle belly of the calf muscle will be stretched over a longer distance, making for a leaner look.

Alternatively, some people have shorter legs, or a wider muscle belly shape, leading to a more condensed, bulging muscle.

Two people running uphill.

Good vs. Bad Calf Muscle Genetics

When people talk about good vs. bad calf muscle genetics, they are essentially saying that their particular genetic makeup has pre-determined their calf muscles to be small or large

Again, while there is little evidence to definitely state that your genetics determine how your calf muscles look, there is a genetic contribution to muscle growth and shape.

What Are Bad Calf Genetics?

Because most people want big, sculpted calf muscles, bad calf muscle genetics refers to a genetic predisposition to a higher percentage of Type I muscle fibers and small muscle bellies.

What Are Good Calf Genetics?

With good calf muscle genetics, the proportion of Type II to Type I muscle fibers in your gastrocnemius is high, meaning the size and strength of your calf muscles is highly responsive to training. 

Good calf muscle genetics also includes a large muscle belly and desirable muscle shape. The muscle belly gives you a good base and the fiber type ratio gives you growth potential.

A person doing calf raises on a machine.

What If I Have Bad Calf Muscle Genetics?

The good news is that even if it seems like the cards are stacked against you with calf muscle genetics, you can still maximize your calf muscle potential with training. 

Exercises like running, jumping rope, and incline walking, as well as resistance training exercises like heel raises, are a great way to strengthen your calves.

There is some evidence to suggest that eccentric exercise (standing on tiptoe and then dropping your heels) can be a great way to stimulate muscle growth.

And finally, even if your calves remain small and flat, you’re in the company of some of the best distance runners.

If you are looking to begin a strength training program to improve your running performance and hope to increase muscle mass, take a look at our Strength Training For Runners Guide.

A person doing calf raises.
Amber Sayer

Amber Sayer

Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, and contributes to several fitness, health, and running websites and publications. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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