What Does Running Do To Your Butt? The Full Explanation

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There are many positive things running does for your body: It strengthens your heart and lungs, it helps tone your legs and sculpt your calves, and it can tighten and tone your core. But what does running do to your butt?

Although it can be a funny question to look up online, many people want to know how running affects the butt. Does running make your butt bigger? Does running shrink your bum? Can running give you a peachy bum? What does running do to your butt?

In this guide, we will look at the effect of running on the butt and hopefully answer the popular question, “What does running do to your butt?” After all, there’s nothing wrong with wanting to turn heads as you walk by in your favorite pair of jeans!

We will look at: 

  • What Does Running Do To Your Butt?
  • Does Running Make Your Butt Bigger
  • Does Running Make Your Butt Smaller?
  • How The Type of Running You Do Affects Your Butt
  • How Does Running Change Your Butt?
  • The Takeaway: What Does Running Do To Your Butt?

Let’s get started!

A close up of a person's glutes in running lights.

What Does Running Do To Your Butt?

So, what does running do to your butt? The short answer is: it depends. Running has the potential to make your butt bigger and it has the potential to flatten your butt or make your butt smaller.

In either case, when we are talking about what running does to your butt, we are essentially referring to two aspects of the butt: the muscles known as the glutes (gluteus maximus, gluteus medius, and gluteus minimus) and body fat.

Running can affect the size of your glutes, the amount of subcutaneous body fat stored in your butt, and the relative ratio of muscle mass to fat in your butt, all of which together can affect the size, shape, and firmness of your butt.

Does Running Make Your Butt Bigger or Does Running Make Your Butt Smaller?

Whether running makes your butt bigger or smaller primarily depends on two things: the type of training or running you’re doing and your overall diet.

Let’s cover the diet first since it’s a little easier to understand.

An array of different meals in aluminum containers with a nutrition plan in the middle.

Gaining weight, whether building muscle mass or gaining body fat, is a matter of a caloric imbalance between how many calories or how much energy you are eating and how much energy or how many calories you are expending.

When you are consuming more calories than you are expending, you will gain weight. The converse is also true: when you are burning more calories than you are consuming, you will lose weight.

With that basic principle in mind, running, which factors into the energy expenditure side of the equation, has the potential to build muscle and increase the size of your glutes, and thus make your butt bigger. 

This is possible when specific training is done in the context of adequate protein intake and a small caloric surplus, enabling muscle growth. 

Similarly, when combined with a healthy diet that provides a moderate, sustained caloric deficit, running will help you lose body fat.  

So, does running shrink your bum?

If your body shape has a fair amount of body fat stored in the hips and butt, running can make your butt smaller.

A person running uphill.

You have to create a caloric deficit of about 3,500 calories to lose one pound of stored body fat.

For this reason, the more you run, or the higher your overall training volume, the more calories you will burn. And, if you don’t make compensatory adjustments in your diet by increasing your food intake, the more calories you burn, the more weight you will lose.

In these cases, running more will gradually decrease the size of your butt, as you lose body fat.

How The Type of Running You Do Affects Your Butt

Now let’s get into the nitty gritty of the way in which the type of running you do factors into whether running makes your butt bigger or smaller.

Running utilizes most of the major muscles in your body, particularly those in the lower body like your glutes, hamstrings, quadriceps, and calves. Thus, consistent training can increase the strength of your glutes.

However, not all runs are created equal when it comes to building the size and strength of your glutes.

A person sprinting. What does running do to your butt if you sprint?

Our skeletal muscles are composed of a couple 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 this is somewhat of an overt simplification, there are two primary types of muscle fibers that runners should be familiar with:

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 in which they can contract is 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 person sprinting.

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 and the type of training you do. 

Longer, slower runs will increase the percentage of Type I muscle fibers in your glutes whereas sprinting and speed workouts increase the proportion of Type II muscle fibers.

Moreover, as mentioned, when supported by adequate protein intake and a moderate caloric surplus (usually at least 10% above caloric balance), running can build muscle mass by adding new muscle fibers.

A person sprinting through sand.

Because Type II muscle fibers are larger and also more prone to grow in size, running fast, sprinting, speed workouts, and running uphill are especially effective ways in which running can increase the size of your glutes and make your butt bigger.

High-intensity exercise like sprinting and running fast also affects your hormonal profile, increasing the levels of anabolic hormones, which support hypertrophy, or muscle growth.

Therefore, running fast has the potential to make your butt bigger, and having a bigger butt might just mean that you run all that much faster. Studies show that the size (overall volume) of the gluteus maximus, the largest and most powerful glute muscle, is significantly larger in elite sprinters. 

Moreover, between elite and sub-elite sprinters, the difference in volume of the gluteus maximus accounts for 34%–44% of the difference in season best performance time in the 100-meter race. In simplified terms, in general, the larger the glutes, the faster the sprinter.

These findings were confirmed in another study, which again demonstrated the association between larger glutes and better sprint performance.

A person sprinting on a track.

How Does Running Change Your Butt?

According to EMG and kinematic analyses, the major functions of the gluteus maximus during running are to keep the torso upright when you land, to control the swing of the airborne leg, to control the flexion of the hip upon impact, and to extend the thigh out for each stride. 

The faster you run, the greater the involvement of the glutes, and the steeper the incline, the greater the hip extension workload that falls on the glutes.

Additionally, there is evidence demonstrating that initially, when you accelerate from an easy jog to a faster run and even a relatively fast sprinting speed, the increase in speed is mostly achieved by increasing your stride length. 

However, as you approach your maximal sprinting speed, increases in speed are accomplished primarily by increasing stride rate, or running cadence.

This is achieved by the hip extensors—the gluteus maximus and the hamstrings—and the hip flexors—accelerating the hip and knee joints more vigorously while the legs are in the swing phase (not on the ground). 

Again, this points to the fact that the faster you run, the more you are relying on your glutes.

A person running uphill.

The Takeaway: What Does Running Do To Your Butt?

In general, sprinting and uphill running can make your butt bigger when your protein and caloric intake are sufficient to support muscle growth. Distance running can make your butt smaller if you’re in a caloric deficit. 

Why should you care?

Strong glutes are associated with decreased risk of patellofemoral knee pain, or runner’s knee, and can make you a faster runner.

To keep those glutes strong, check out our glute activation guide for distance runners!

A person doing a resistance band squat.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. 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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