Is Running A Marathon Bad For You? 5 Negative Effects Of Running 26.2 Miles

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With most inherently healthy things, the natural inclination is to think that more of a good thing is even better. For example, if you should be having 5 to 6 servings of vegetables per day, 7 to 8 servings would be even better. 

With the physical activity guidelines for adults set forth by the Centers for Disease Control and Prevention and the British Heart Foundation, the baseline recommendations are to accumulate either 150 minutes of moderate-intensity aerobic exercise or 75 minutes of vigorous-intensity cardio exercise per week but getting more is better.

But can you take things too far? Can you run too much? While running a 5k, 10k, or maybe even half marathon is great for your health, is running a marathon bad for you?

In this article, we will discuss the potential physical consequences or downsides of running a marathon as we aim to answer the controversial question: Is running a marathon bad for you?

We will cover: 

  • Is Running a Marathon Bad for You?
  • 5 Potential Negative Effects of Running a Marathon

Let’s jump in.

People running a marathon and passing in a blur.

Is Running a Marathon Bad for You?

Perhaps there is no question more polarizing between the running community and non-runners than, “Is running a marathon bad for you?”

After all, runners will defend the innumerous benefits of running tooth and nail against anyone who raises questions about the essential risks of running.

It’s most important to establish right off the bat that we believe that, by and large, running is absolutely one of the best things that most people can do for their body, mind, and overall health unless you have certain pre-existing conditions that otherwise make running unsafe.

With that said, trying to approach the research about the safety of marathon running with an unbiased opinion and open mind brings us to consider the potential risks that can be involved with putting your body through running a full 26.2 miles.

Ultimately, what differentiates running a marathon from running in general or focusing on shorter distances, whether recreationally or competitively, is indeed the long distance of a marathon itself. 

When you are discussing the benefits of running in a broad sense, the term “running“ can encompass just about anything.

Two people running down the street.

From a very low-intensity walk/jog method to jogging 30 minutes a day most days of the week to satisfy the physical activity guidelines, to training for and competing in high-level 5k races, to running on the trails with your dog, to training for one marathon after the next, it’s all considered running.

Along the very broad continuum of how people might participate in the sport of running, certain engagement levels may or may not be more appropriate or healthy for the body than others, depending on your overall health, fitness level, and the amount of running itself you are doing.

For example, running a marathon might be perfectly healthy and reasonable for someone who is of good health and takes plenty of time to train, gradually increasing distance, listening to their body, feeling well, recovering adequately, and making any adjustments to training when they need to back off for one reason or another.

On the other hand, running a marathon might be a bad idea for someone who has virtually no experience and wants to do a “crash course“ in preparing for the marathon, running way harder than their body is ready to endure, ignoring all pain or signals that they need to back off, and placing the importance on training above all else in regards to their health.

Additionally, someone with a known heart condition and who has been advised against taxing their heart during longer workouts would also not be a good candidate to safely run a marathon unless otherwise cleared by their cardiologist.

As we explore the potential risks of running a marathon and ways that running a marathon can be bad for your body, it’s important to bear in mind that this doesn’t necessarily mean that running itself is bad or that running a marathon is inherently bad for everyone

A person holding their chest in pain.

Potential Negative Effects of Running a Marathon

So, is running a marathon bad for you? Here are some of the potential concerns and risks of running a marathon:

#1: Cardiac Events

The most concerning and frequently cited reason that running a marathon is bad for your body is the potential risk of sudden cardiac death or serious adverse or irreversible damage to your heart.

There have certainly been some very tragic losses of seemingly young and healthy marathon runners during a race, as well as older runners, due to sudden cardiac arrest or serious cardiac events that occur while running a marathon.

These unfortunate events resulted in death shortly thereafter, as either medical personnel were not able to step in quickly enough to restore proper heart function, or the cardiac abnormalities were too severe.

For example, studies looking at sudden cardiac death in young (age 12-35) seemingly healthy individuals is about 2.5 times higher in athletes participating in vigorous exercise compared to age-matched non-athletes, and some of these deaths occur when not engaging in exercise at the moment.

A person holding their chest, perhaps having a heart attack.

Studies have found that marathon running may increase the risk of myocardial fibrosis, and a large review found that marathon running is associated with a low risk of sudden cardiac death that is transient in nature. 

Data from the review found that the risk of cardiac events while running a marathon is even lower in women and independent of the marathon experience. Moreover, most deaths due to sudden cardiac arrest during marathon running are due to underlying coronary artery disease. 

For example, research has found that about 73 percent of the sudden cardiac deaths experienced by older joggers and marathon runners are attributable to underlying coronary artery disease.

Proper screening and the availability of trained medical personnel with automatic external defibrillators can play a significant role in preventing sudden cardiac death while running a marathon.

A person speaking with his doctor.

Even in the absence of fatal cardiac issues during marathon running, studies have found that marathon runners rather frequently display cardiac biochemical and functional abnormalities following the completion of a marathon.

However, these cardiac abnormalities seem to be transient and resolve on their own in most cases, though one study found that adverse changes may persist for up to three months in novice marathoners.

Furthermore, even the researchers in this literature review noted that sudden cardiac deaths associated with marathon running are “exceedingly rare events.” 

Ultimately, they suggest that most sudden cardiac death events among marathon runners occur in those with known, pre-existing cardiac conditions, so prevention is possible.

The overall conclusion is that the “robust association of endurance running with improved quality of life and longevity underscores the importance of putting risks into perspective with other well-established health benefits of regular vigorous exercise.”

In other words, the potential cardiac risks of running a marathon are so slight and likely preventable that it often does not warrant reconsideration of the overall benefits of marathon running and endurance running.

A runner cradling their knee with their hands.

#2: Increased Risk of Injuries

Running is a high-impact, repetitive activity, so runners are prone to various musculoskeletal injuries. This risk is heightened with training for a marathon due to the necessary mileage and pounding on the body.

A large review looked at all of the potential health implications of distance running, with races ranging from the 10k to ultramarathon. 

Unsurprisingly, marathon running was associated with an increased risk of running-induced injuries, such as knee pain and stress fractures, with approximately half of the active runners reporting having more than one injury per year.

Risk factors identified with a greater chance of experiencing a running injury were excess body weight, higher weekly mileage, and marathon or ultramarathon running as opposed to 10k or half marathon running. 

In other words, there’s a greater risk of getting injured training for a marathon than when running shorter distances.

A person holding their back in kidney pain.

#3: Kidney Damage

There is some evidence to suggest that marathon running can stress the kidneys, even when hydration is optimal. Though this is typically an acute kidney injury that impacts the ability to filter waste for just a couple of days, it’s possible that habitual marathon racing could lead to chronic kidney issues.

#4: DNA and Muscle Damage

Some studies have found that marathon running can cause damage to DNA and muscle tissue.

#5: Biochemical Changes

A large review noted that marathon running can cause an increase in acute phase proteins, cortisol (stress hormone), liver proteins, red cell breakdown, skeletal muscle cell damage, and blood in the urine and a decrease in testosterone and bone mass.

We want you to walk away from this discussion not feeling dissuaded or disheartened by your aspirations to run a marathon but instead informed of the potential downsides of running a marathon that you may want to discuss with your own healthcare provider in regard to your personal health status.

Why don’t we take a look at the other side of the coin and discuss the great physical and mental health benefits of running? Check out our article, the 26 Awesome Benefits of Running, for more information!

A person running and smiling.
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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