What Does Running Do To Your Body? 5 Amazing Benefits

Given the wide range of benefits of running, runners take up the sport for a variety of reasons.

They might be primarily motivated to run to improve cardiovascular health and reduce the risk of lifestyle diseases like obesity, type 2 diabetes, heart disease, and hypertension.

Many runners adopt the sport to primarily enjoy the mental health benefits of running, such as decreasing stress, improving mood, and increasing energy and focus, or they may love how running can get you outside in the fresh air away from technology and screens.

Other runners enjoy the metabolic benefits of running and use the sport as a way to help them lose weight or maintain a healthy weight.

But what does running do to your body, exactly? What do legs before and after running look like? What kind of running body transformation can you expect?

In this article, we will discuss the expected changes in a runner’s body and answer the question, what does running do to your body?

Let’s get started!

Two people running in an industrial area.

What Does Running Do to Your Body?

Here are some of the top things that running does to your body:

#1: Running Strengthens Your Heart and Lungs

Running is a fantastic form of aerobic exercise, which means that it increases your heart rate and respiration rate.

In this way, cardio exercise like running strengthens the heart and lungs and induces other favorable changes to the cardiovascular system, such as increasing the elasticity and vasodilatory properties of the blood vessels and increasing the density of capillaries in the skeletal muscles so that more oxygen can be efficiently delivered.

These adaptations help increase your stamina or aerobic endurance.

Furthermore, having a healthier cardiovascular system can increase your lifespan. 

Research has found that runners have about a 25-30% lower risk of all-cause mortality, and consistent running has been found to increase your life expectancy by at least three years.

In fact, a study that examined the disease and mortality risk of 13,000 runners over nearly 15 years found that running as little as six miles per week—or roughly 52 minutes total—effectively decreased the risk of all-cause and CVD mortality by 30% and 45%, respectively, relative to non-runners. 

Moreover, even runners who ran this little had an average increase in survival over non-runners of 3.0 and 4.1 years for all-cause and CVD-related survival, respectively.

A person smiling and running outside.

#2: Running Improves Markers of Health

Running has been shown to cause positive changes to markers and risk factors of common diseases.  

For example, one massive study that followed 19,000 adults over the course of six years found that runners had a 72% lower rate of developing diabetes compared to non-runners.

Furthermore, there is evidence to suggest that aerobic exercise, such as running, can be as effective at lowering blood pressure as anti-hypertensive medications.

Finally, according to research, running has been shown to help reduce the risk of 26 different cancers, independent of other risk factors.

A person flexing showing what running does to their body.

#3: Running Strengthens Your Legs

If you are a beginner runner but have taken a look at the legs of a friend or neighbor who runs regularly, you have likely noticed prominent calf muscles, enviable quads with a tear-shaped definition above the knee, and overall strong, muscular legs.

One of the main things that running does to your body is strengthen, tone, and help define your leg muscles. New runners are often ecstatic about the changes in their legs before and after running for several months.

Although improvement in muscle tone and definition in the calves, quads, hamstrings, and glutes from running can take time, most runners find that the miles of training help sculpt muscular, yet lean legs.

The degree of muscle “tone” for muscle definition you will get from running depends largely on your body fat percentage, which is influenced not only by how much you run and what types of workouts you do but also by your diet.

A person running in the rain.

If you have excess body weight, you’ll see less muscle definition, even with a high-volume training program. 

With that said, even if you can’t see defined striations in your leg muscles from running, you should still notice more shapeliness to your legs through your running body transformation.

Running can add shape and size to legs that are thin and “stickly,” giving you curves in the back where your calves are, a rounder and bigger butt, and fuller, meatier thighs due to muscle growth in your quads and hamstrings.

On the other end of the spectrum, if you live in a large body with lots of excess fat that normally gives you amorphous legs with little definitive shape, your running body transformation will likely be marked by more shapeliness as well. 

Your calves will become more sculpted, and your butt and thighs will become firmer, slimmer, and more svelte.

A person running in the grass.

Keep in mind that even if you don’t see massive differences in the physical appearance of your legs before and after running, you should be proud of the fact that running is indeed strengthening your entire lower body.

Having stronger legs has numerous benefits.

For example, if you strengthen for quads, glutes, hamstrings, and calves through running, you will enjoy improved performance not only with running itself but also when performing other athletic activities such as cycling, hiking, rowing, squats, lunges, or any other type of physical activity that uses your legs.

Stronger legs also facilitate improved function during everyday activities like climbing the stairs, getting into and out of a car, walking, etc.

There are also metabolic benefits of building muscle through running. 

Muscle is a metabolically active tissue, meaning that your muscles require more energy during rest and physical activity. 

Therefore, as you increase lean body mass through running, you will enjoy a higher basal metabolic rate (BMR) and will burn more calories during your workouts. This can help support even further body composition changes because the more calories you burn in a day, the easier it will be to create a caloric deficit and lose body fat.

A runner flexing.

#4: Running Strengthens Your Bones and Joints

Running is a high-impact activity, so it is one of the most effective forms of exercise for increasing bone density

Bones respond to the stressors placed upon them and adapt accordingly. Because your body is subjected to forces that are equivalent to approximately 2 to 3 times your body weight with each step, running helps stimulate bone mineralization, fortifying your bones to be stronger and more resilient. 

This can reduce the risk of osteoporosis and fractures, particularly later in life.

In addition to improving bone health, running can also improve the health of your joints and decrease the risk of arthritis.

Studies have found that running can improve the health of the spine, while other research has shown that marathoners and long-distance runners may have healthier knees than sedentary age-matched peers.

A person running in the park.

#5: Running Can Reduce Your Body Fat Percentage

Most people who are interested in the ways in which running changes the body or running body transformations are keen to learn about body composition changes and fat loss by running.

Running has the ability to help you lose body fat because it is a vigorous, total-body workout, making it an efficient way to burn a lot of calories

It’s important to note that running will not help you lose weight if you are in a caloric surplus, which means that you are consuming more calories per day than you are burning.

However, if you use running to help you generate a moderate caloric deficit, with or without accompanying dietary changes, running can decrease body fat percentage.

In order to lose one pound of stored body fat, you need to create a caloric deficit of 3500 calories.

A person running on a track.

This energy deficit can be generated slowly through increasing physical activity (running more), decreasing your caloric intake, or a combination of both (which is usually the recommended approach to healthy, sustainable weight loss).

As you lose body fat by running, you will notice that not only will the weight on the scale begin to decrease, but your clothes should start to fit looser, and you might go down a couple of sizes. 

Body fat is a voluminous tissue because it is not particularly dense, meaning that it takes up more space in your body to store a pound of body fat versus a pound of muscle or lean tissue. 

This is why you might start to slim down as you begin running, even if your weight is not changing appreciably on the scale. If you are building muscle and losing body fat, your body weight will remain stagnant, but your body recomposition will result in a slimmer, trimmer, firmer (and healthier!) body.

The aforementioned positive benefits of what running does to your body only scratches the surface of the physical health benefits of running. But in addition to asking what does running do to your body, you can also ask, what does running do to your mind?

There are fantastic things that running does to your mind and your mental health. For more information, check out our article: Running and Mental Health, The Remarkable Benefits of Running.

A runner with their arms crossed.
Photo of author
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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