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The Surprising Science Behind Why Marathon Runners Have Smaller Muscles

why do people who participate in marathons tend to have smaller muscles?

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In this article, we will examine the question ‘why do people who participate in marathons tend to have smaller muscles?’.

This is a common question among fitness enthusiasts who engage in endurance activities such as long-distance running, cycling, and swimming. Many people wonder why these activities result in smaller muscles compared to other forms of exercise such as weightlifting.

Understanding Muscle Growth

The first thing you need to know is that resistance exercise is what actually stimulates muscular growth. By using weights or your own body weight, resistance training forces your muscles to grow and adapt.

This type of exercise causes small micro-tears in the muscle fibers, which are then repaired and rebuilt stronger and larger during rest and recovery periods.

Muscle Adaptation in Endurance Exercise

Why Do People Who Participate in Marathons Tend to Have Smaller Muscles? Why Do Marathon Runners Have Smaller Muscles?
Why Do People Who Participate in Marathons Tend to Have Smaller Muscles?

Endurance activities, such as marathon running, require a different sort of muscular response. The basic purpose of endurance training is to improve the body’s ability to maintain activity for extended periods of time. This adaptation is accomplished by increasing the quantity and efficiency of mitochondria, which produce energy in the muscles.

As a result, endurance exercise does not exert the same amount of stress on the muscles as resistance training and hence does not promote quite so much muscular growth. Additionally, endurance sports demand that the body be as efficient as possible in terms of energy expenditure. Bigger muscles demand more energy to move, which might be negative in tasks requiring long-term endurance.

The Appearance of Smaller Muscles

Why Do Marathon Runners Have Smaller Muscles?

It is important to note, however, that this does not imply that marathon runners have no muscular mass at all. Although endurance sports do not result in significant muscle growth, they do require the muscles to operate for extended periods of time, which can result in enhanced muscle endurance and tone.

Marathon runners typically have low body fat percentages, making their muscles appear smaller. This is due to the fact that muscle size is sometimes disguised by a layer of fat. Because of the enormous caloric burn of running, marathon runners’ muscles may appear smaller than those of those with higher body fat percentages.

Genetics and Diet

Aside from the type of exercise, genetics play an important role in muscle size and development. Some people are genetically predisposed to have larger and better-developed muscles, whereas others may find it difficult to gain muscle even with resistance training.

Additionally, food is very important in muscle development. Even with endurance training, a diet high in protein and other nutrients required for muscle building can assist increase muscle development.

Consuming enough calories to sustain endurance activity while also taking enough protein to support muscle building is critical.

If I Start Doing Cardio Will I Lose Muscle?

marathon runner 5

You are not alone if you are concerned about losing muscle while performing cardio exercises. Many people are concerned that cardio will cause them to lose muscle mass, but this is dependent on a number of factors.

While cardio can be an efficient technique to burn calories and lose weight, if not done properly, it can also result in muscle loss.

The primary reason that cardio might cause muscle loss is that it stimulates the muscles. While you do exercise, your body requires energy to keep moving, which comes from glycogen stored in your muscles. This can cause muscular tissue breakdown over time, resulting in muscle mass loss.

The extent to which cardio causes muscle loss, however, is determined by a number of factors, including the intensity and length of the activity, as well as your diet and overall lifestyle habits.

Maintaining Muscle While Doing Cardio

Maintaining Muscle While Doing Cardio
Maintaining Muscle While Doing Cardio

If you’re worried about losing muscle while performing cardio, there are a few things you can do to reduce muscle loss and retain muscle mass.

To begin, you must integrate strength training into your fitness programme.

Lifting weights or completing bodyweight exercises that challenge your muscles to grow and adapt is what strength training involves. This sort of training promotes muscular growth, which can help offset muscle loss caused by cardio.

It is also critical to ensure that you are getting adequate protein and calories to assist muscle growth and repair. Protein is required for the construction and maintenance of muscle tissue, therefore consuming enough of it to support your exercise and recovery is critical.

Finally, striking a balance between cardio and strength training is important. While cardio can be a great strategy to burn calories and enhance your overall health, challenging your muscles through resistance training is vital for muscle mass gain and development.

You can find a balance that supports both your weight reduction and muscle growth goals by including both types of exercise in your regimen.


Marathon runners have smaller muscles because endurance exercise does not encourage muscular growth in the same way that resistance training does.

Endurance training, on the other hand, develops muscle endurance and tone while enhancing the body’s ability to sustain activity for extended periods of time.

Muscle development and size are also influenced by genetics and food.

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