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10 Things That Happen to Your Body During an Ultramarathon

by David Long
fact checked by Rachel Jones

Most people are familiar with the concept of a marathon. It’s a race covering a distance of more than 26 miles (41.8 kilometers). Sounds pretty extreme, right? For those people who think running 26 miles is not enough, there is an even longer race, an ultramarathon. An ultramarathon is technically any race that is longer than a marathon, but many ultramarathons are 50 miles (80 kilometers) or more. For this reason, these races are intense and potentially dangerous, even more so than traditional marathons.

Our bodies react in strange ways when covering that kind of distance. Below, we will go through ten things that happen to your body during an ultramarathon. So, drink some water, stretch out those calves, and get set as we look at some crazy things that can happen to your body during an ultramarathon.

Related: 10 Surprising Ways To Hack Your Body

10 Soreness (DOMS)

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The first item on our list is probably not that surprising. After all, soreness is a typical response to any exercise. However, soreness associated with ultramarathons can be especially intense. Ultramarathon runners—sometimes called ultrarunners—experience an extreme kind of soreness called DOMS (delayed onset muscle soreness). This means that ultrarunners will have a delayed soreness that may persist for days or even weeks following a race.

This is caused by hours (many hours) of eccentric contractions. Soreness typically manifests itself in the lower leg, but in other cases, runners may be sore in their knees, hips, or feet. Professional ultrarunners have to deal with soreness throughout and after the ultramarathon.

If you plan to run an ultramarathon, plan to be sore. The bottom line is our bodies are not made to run these kinds of distances, and there is no way to avoid leg fatigue (and the resulting soreness) in an ultramarathon.

9 Blisters

Ultra Marathon Blisters: Preparation, Gear, Prevention & Treatment

As ultrarunners continue to push themselves physically, blisters are a common problem. Think about it, these runners are sweaty and moving quickly. Even with the best pair of shoes and socks in the world, there will be some rubbing. Add to that the likelihood of sweat (or even rain or puddles) getting in your footwear, and you have a surefire recipe for blisters. Ultramarathon runners routinely get blisters on their toes, ankles, and heels.

Unlike soreness, however, blisters can be avoided if the runner is prepared. Some runners try to combat blisters by taping up their feet before running. Other runners may try to avoid painful blisters by changing socks, shoes, or other clothing items during the race.

If you are considering an ultramarathon, it is very important to be aware of the humidity, temperature, and other conditions. This allows you to plan for your run to be as painless (hopefully blister-free) as possible.

8 Cardiac Issues

What Happens To Your Body During An Ultramarathon

Exercise is supposed to be good for your heart, right? Regular exercise can improve your heart health and even make you less likely to have cardiovascular disease, but ultramarathons aren’t regular exercise. They’re… ultra. The strain on your heart during these long races is extreme.

Generally, this strain presents itself in one of two ways. If you run when it is very hot or if you are dehydrated, your heart rate may increase. On the other hand, if you are extremely fatigued, your heart rate may actually decrease. Neither is ideal.

Following an ultramarathon, runners often get dizzy. In extreme cases, runners even faint. This occurs when the blood flow to the heart is disrupted. Experienced ultrarunners may monitor their heart rate through a smartwatch to avoid this problem. If that’s a little too tech-reliant for you maintaining appropriate hydration levels can help you curb (or avoid) these dangerous cardiac issues while on the long run.

7 Hyperthermia or Hypothermia

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Because ultramarathons are so intense, your body can react in two different ways, depending on the conditions. You could experience hyperthermia (the condition of having a body temperature far above normal) or hypothermia (the condition of having an abnormally, dangerously low body temperature). This just illustrates again how difficult these races can be.

Hyperthermia occurs for runners when the weather is especially hot. It can cause headaches, blurred vision, and lightheadedness. Runners with hyperthermia may stop sweating altogether, a very dangerous sign. The worst cases of hyperthermia can result in heat stroke.

The other extreme is hypothermia. As you may expect, ultrarunners experience hypothermia when running in colder conditions. High elevations, wind, snow, or consistent rain may cause hypothermia. Extreme changes in temperature or elevation can cause either hyperthermia or hypothermia. Hydration and appropriate gear can help you avoid these potential perils.

6 Foot Pain

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Running starts and ends with your feet. Every step you take, even on a normal day, involves intricate movement of your feet. Feet have more than 100 moving parts. With every step during an ultramarathon (and there are a lot), you are applying significant pressure to your feet. Because of this, ultrarunners are susceptible to foot pain and foot injuries.

Distance runners deal with various kinds of foot injuries, including plantar fasciitis (turf toe), Achilles tendinitis, stress fractures, Metatarsalgia, and more. Experienced runners have several techniques they will use to mitigate these dangers, such as:

  • Using properly fitting shoes and socks
  • Bringing an additional pair of socks
  • Stretching appropriately before the ultramarathon
  • Monitoring for any foot or lower leg pain

Even the most careful and well-trained distance runners still experience foot pain. While the pain is somewhat unavoidable, be sure to consider your long-term health before pushing through it.

5 Weight Loss

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Well, they can’t all be bad, right? Ultramarathons will cause you to lose a lot of weight and quickly. Although it is an extremely difficult way to lose a few pounds quickly. An average ultramarathon runner will lose between four and six pounds in a single race. Wow. However, it is not usually a sustained loss.

Runners who complete an ultramarathon sweat copious amounts. Despite their best efforts to rehydrate, ultrarunners are typically severely dehydrated by the end of the race, so this weight loss is generally considered “water weight” lost as sweat.

There does not seem to be many runners can do to avoid weight loss (though proper hydration is always a good idea during any run). Usually, after a week or so of a typical diet, your weight will stabilize. While it may be the hardest way to lose weight, at least it’s efficient!

4 Glycogen Depletion

The role of glycogen when racing the marathon

Glycogen is how our bodies store glucose (our main energy source). It is stored in skeletal and liver muscles. When our bodies run out of glycogen, we also run out of energy. This can happen in two ways: from a lack of caloric intake or intense exercise. When our bodies run out of accessible energy, we tap into glycogen reserves. Once your body runs out of glycogen, you may feel the following:

  • Like you have “hit a wall”
  • Extreme fatigue
  • That it takes an excessive amount of effort to continue running

Because ultramarathon runners often burn more than 400 calories an hour, glycogen depletion is a serious concern. You can avoid some of the issues associated with glycogen depletion by eating plenty of carbohydrates right before the big race.

3 An Upset Stomach

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Well, I said to eat plenty of carbohydrates, didn’t I? It is important to keep everything within reason leading up to your race. Otherwise, you may be dealing with another common ailment for ultrarunners: an upset stomach. Generally, in the lead-up to a race, ultramarathon runners should avoid consuming the following:

  • Caffeine, including coffee, tea, and soda
  • All dairy products
  • Spicy or unfamiliar foods
  • Beans, legumes, and other high-fiber foods

Any of the items on the above list can irritate your digestive tract. Consider that your stomach (and its contents) are going up and down as you run. Stomach pain can present itself in several ways. The most common is called runner’s trots. This is the immediate need to defecate (poop)—either during or immediately after running.

Other runners may experience nausea, while still others may get stomach cramps. You need your body to get you through the race, so make sure to fuel it properly and at the right intervals, or you might not make it.

2 Joint Pain

How to Manage Pain During an Ultramarathon

Joints are the little points on our bodies where our bones make contact. As you might expect, an ultramarathon places extreme strain on all your joints, particularly those from the waist down. The most common joints that ultrarunners experience pain in are their hips, knees, spine, ankles, and toes.

Joint pain is common for marathon runners, but when the distance is amplified, so is the risk to the participants. While this pain may be somewhat unavoidable, it is interesting to note that most joint pain happens on the downhill portions of a race.

1 Sleep Deprivation

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While you may be able to refuel with a small snack or rehydrate with a quick sports drink, there is simply no way to take a catnap during an ultramarathon. Due to this, most runners experience sleep deprivation and the symptoms associated with it.

Ultramarathons typically take 24 hours or longer to compete. It’s only natural that the body craves sleep at that point. This can present itself in several ways; dizziness is a common complaint, while other runners experience disorientation. Some ultramarathon runners may even experience hallucinations in the most extreme of cases.

Getting appropriate sleep leading up to a race can leave you feeling more prepared, but all runners will have to deal with the perils of sleep deprivation at some point during the ultramarathon. On the bright side, it gives you something to look forward to: Imagine how well you’ll sleep after your race!

fact checked by Rachel Jones