What Happens to Your Body on a Long-Distance Run

Jason Fitzgerald
by Jason Fitzgerald
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What Happens to Your Body on a Long-Distance Run

Marathon running did not have an auspicious beginning. Legend has it that Pheidippides ran about 25 miles to Athens to announce the Greek victory in the Battle of Marathon and then died abruptly. While history has shown there were likely other circumstances around his death (and the runner may not have even been Pheidippides), concerns around long-distance running have continued to increase as the sport has become more popular.

When the running boom began in the 1970s, less than 25,000 runners finished a marathon in the United States each year. In recent years, that number has jumped to more than half a million. Running 26.2 miles (or more) has an impact on all runners, from novice to elite. Whether it’s your first or 50th, the marathon can be a humbling experience.

From your feet to your brain, you will feel residual effects in the hours and days that follow. The good news is that, for the vast majority of us, these impacts are benign and short lived and running regularly is far more likely to improve your health and longevity than hurt it.


Here’s how running distance can affect different parts of your body in different ways:

The average runner takes more than 40,000 steps over the course of a marathon, which means your feet bear a lot of repetitive impact. Some general soreness is normal, and if your shoes are a little snug or your toes bump up against the top of the shoes, you may find yourself losing one or more toenails as well. Hot or wet conditions can exacerbate chafing and make you more prone to blisters.

Even the most well-trained runners experience muscle soreness in their legs, since they perform the bulk of the work on race day. Muscle damage in the form of micro tears can take a day or two to settle in, and as the body works to repair them, you may find yourself with a case of DOMS (delayed onset muscle soreness). Hilly courses, particularly those with downhills like the Boston Marathon, can leave your quads feeling particularly beat up.

Even the most comfortable clothing can cause chafing, given the amount of time you’ll be running. Lubricants can help prevent the painful soreness of post-run chafe, so protect delicate areas in advance.

Some nausea is common either during or after a marathon, as blood is diverted from your gut to more essential functions. Practice fueling with sources your stomach can tolerate in the conditions you’ll face on race day to help minimize gastrointestinal distress.

Mild dehydration is common during a long race, as it’s nearly impossible to replace all the fluids you lose. While this places temporary stress on your kidneys, it is minimal if you hydrate properly during and after your race. To avoid further stress, don’t take unnecessary medications like NSAIDS that are processed by the kidneys, as this can make their workload much more overwhelming.

There’s varying evidence about how long-term, long-distance running impacts your heart. In general, training causes some changes in your heart, which is a muscle, and it gets stronger with continued training. There may be a slight risk of increased plaque formation or atrial fibrillation with long-term, long-distance running, but it’s unlikely one marathon will have a significant impact. Some temporary changes in biomarkers may show increased stress to the heart after a marathon, but they return to normal after recovery. If heart disease runs in your family, always get clearance from your doctor. Proper training should prevent the excessive overexertion that can be particularly hard on your heart on race day.

Exercise-induced rhinitis, leading to a runny nose during exercise, is exceedingly common in runners. This typically stops once you finish your run but can require some attention mid-run to avoid irritation under your nose.

This is a real thing! Running increases levels of endorphins that naturally boost your mood and increase feelings of well-being and calmness — aka the runner’s high. Don’t be surprised if you suddenly forget about all the pain in time to sign up for your next marathon.


When properly prepared, your body is remarkably ready to handle the marathon distance. Be smart with your training, seek medical advice when needed and expect some soreness in a variety of areas post-race. But most of all, enjoy the experience and be in awe of what your body can do for you.

About the Author

Jason Fitzgerald
Jason Fitzgerald

Jason is the founder of Strength Running, a USA Track & Field certified running coach and 2017’s Men’s Running’s Influencer of the Year. Learn more about how he can help you run faster.


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