13 Ultramarathon Race Day Ailments & Injuries: Prevention, Treatment, & When to Push Through

Last Updated on January 17, 2024 by Heather Hart, ACSM EP, CSCS

As a coach I often tell my athletes “the longer the race, the more opportunities there are for things to go wrong“. It sounds like a sarcastic quip from a seasoned and surly ultra runner (which, to be fair, I am) but it’s true: ultramarathons leave a lot of room for unexpected ailments and injuries to pop up.

A small hot spot that you might be able to ignore during a half marathon may turn into a raging, half dollar sized blister over the course of 50 miles. The nutrition strategy that never lets you down on a 20 mile long run may leave you puking in the bushes after 100K.

Runners often dedicate months and months of their time and energy training for an ultramarathon, and no one wants their finish line thwarted by something unexpected such as painful buttcrack chafing or corneal edema.

But as with most things in life, knowledge is power. Knowing what sort of ultramarathon race day ailments and injuries you might be up against, knowing how to prevent them, and knowing what to do if you experience them, are all critical components in helping you reach that finish line.

In writing this post I consulted with Lauren Klein, MS, LAT,ATC, CES. Lauren is an athletic trainer and ultrarunning coach who has worked as medical staff at a number of ultramarathons, including the Western States Endurance Run 100, Tahoe 200 Endurance Run, and more.

Together, we’ve come up with a list of 13 common ultramarathon race day ailments & injuries that may get in the way of your finish line. Some you’ve likely heard of, others may be new to you. And while we genuinely hope you experience NONE of these ailments, our goal is leave you feeling prepared to deal with them if they do occur.

(And, for what it’s worth, I promise to keep the gross feet pictures to a minimum. )

Blisters

I’m fairly certain there isn’t a runner out there who hasn’t experienced a blister at some point in their running career. But in the off chance you aren’t aware: a blister is a small fluid-filled sac that forms under the epidermis, or the outermost layer of skin. It forms when friction repeatedly rubs or stretches the skin, creating a tear between skin layers, which fills with fluid.

Runners most often experience blisters on their feet, but blisters can occur elsewhere on the body. Blisters can range from mildly annoying to excruciatingly painful, and if left untreated, have absolutely caused athletes to DNF races.

How to Prevent Race Day Blisters:

• Wear appropriately fitting shoes. Make sure your shoes have enough room for toe splay, but not so much that your feet are sliding around creating friction. Ideally you wear the same sneakers that you have trained in, so you are already aware of any hot spots that may cause irritation.
• Wear moisture wicking socks. Avoid wearing cotton socks, opt for something more moisture-wicking that will pull the sweat away from your skin. Bring extra dry socks to change into if/when feet get too wet.
• Lube your Feet. Prevent friction damage to your skin by covering your toes or other hot spots that may blister in anti chafing cream. Some of our favorites include RunGoo, Squirrels Nut Butter, and the OG in the “anti chafed runner” industry, Body Glide.
• KT tape as prevention. If you are prone to blistering in certain spots, using kinesio tape (KT tape) may help prevent friction. According to Klein: “the tape plays well with water, moves with the skin, and has a low risk of restricting blood flow.”
• Manage hot spots immediately. “Hot spots should be managed when they form, to avoid them turning into blisters” says Klein. “If there’s a rock in your shoe and you’re in between aid stations, you’re better off taking them time to get it out on the trail as to avoid it causing issues later on.”

What to Do if You Blister Mid-Race:

“Blisters and toenails are handled on a case by case basis” says Klein. “Some blisters are better popped, some are better left alone.”

Popping a blister does indeed often relieve the pain of the blister, however, it opens the skin up to possible infection…and potentially even more pain. When in doubt: ask the medical volunteers or staff.

“Do NOT be shy to ask aid station medical to assist with any of these things!” says Klein. “If these people were afraid of gnarly feet, they wouldn’t be here. They know what they signed up for. I personally feel incredible pride after tending to someone’s feet blisters for 20 minutes at mile 177. I might not remember the names of everyone whose feet I have cared for, but I remember the conversations we had and the bonds we formed in that time.”

Corneal Edema

Corneal Edema is inflammation (or swelling) of the cornea, the outermost layer of the eye. While this phenomenon is rare, ultramarathon-associated corneal edema is not unheard of.

“Without knowing what corneal inflammation is,” says Klein “the symptoms are very freaky – it basically leaves you feeling blind. It is not associated with pain, but vision can become progressively blurrier until you can’t see out of your eye. This is especially dangerous when running at night and on technical terrain. “

During longer races, the corneal epithelium must endure wind, temperature changes and enhanced ultraviolet (UV) light exposure, and cope with decreased oxygen tension at higher elevations (Moshirfar et al).

Further, studies show that ultrarunners actually have a decreased rate of blinking. Sounds wild, but it’s true. According to a case report published in the Ophthalmology and Therapy Journal: “Unlike track runners, who anticipate no obstacles ahead, ultramarathon runners must constantly use their eyes to select the best path. This visual attention reduces the spontaneous blink rate, which intensifies the physical challenge to the corneal epithelium.”

How to Prevent Corneal Edema During an Ultramarathon

• Wear sunglasses. Eye protection is the most effective method for preventing corneal edema during long-endurance sports, since it provides shielding from wind and UV light.
• Use eye drops. Help keep your eyes moist by using eyedrops. “You ever see Courtney Dauwalter put in eye drops at an aid station? This is why!” says Klein
• Stay hydrated. Researchers propose that accumulation of lactate caused by increased production and decreased excretion is one of the underlying mechanisms of the acute corneal edema induced by ultramarathon running. Since dehydration can further increase the blood lactate level, adequate hydration is advised.

What to Do if You Experience Ultramarathon Induced Corneal Edema:

“From the minimal research that is out there on this, cases of corneal edema typically resolve within a few hours, some taking as long as 48 hours.” says Klein. Nevertheless, this is an instance where a visit to the race medical staff may be warranted.

Things that may help ease the effects of corneal edema include:

• Administration of topical 5% hypertonic sodium chloride can enhance corneal clarity in the event of corneal edema.
• Rest or closure of the eyes. A little downtime mid race may help ensure you reach the finish line.

Gastrointestinal Distress

Gastrointestinal distress during a race can lead to anything from mild nausea and bloating, to a runner riddled with diarrhea, spending more time in a port-a-potty than on the race course. While it’s not at all uncommon to experience GI distress during a race, it’s something that most runners try to avoid.

Typical causes of GI distress during an ultra include:

• Under-fueling
• Dehydration
• Improper timing with fueling (not fueling early or often enough)
• Heat
• Intensity

How to Prevent Gastrointestinal Distress During an Ultramarathon:

• Practice your race day nutrition. “The best way to avoid GI issues happening is to TRAIN with nutrition” says Klein. “Fluid and food intake have to be practiced to train your gut just as well as running is training heart, legs and lungs. Find out the recipes that work for you. Take note if you’re a heavy sweater and factor that in. “
• Fuel early and often. Have a fueling strategy ready, and stick to it, even when you don’t want to.
• Stay hydrated – but avoid overhydrating (more on this below).

Upset Stomach? What to do Next:

While there is no one “cure all” for gastrointestinal distress during an ultra, one of the tips I give my athletes is to have multiple backup plans for their nutrition. If what you are currently fueling with is upsetting your stomach, try a different approach.

Switching from liquids to solids (or vice versa) or switching from sweet to savory (or vice versa) may be the trick to calming your digestive system down.

For more on this topic, visit the post: “Top 9 Causes Of Nausea In Ultrarunning (& How To Avoid Runner’s Stomach Issues)“

Bruised Toenails

Bruised toenails – or subungual haematomas – are caused by either one single major trauma to the nail bed (such as stubbing your toe hard on a rock), or chronic minor trauma (such as repeatedly hitting your toenail on the front of your shoe while running downhill).

Bruised toenails may be mild and pain free, but other times may result in throbbing pain under the nail.

How to Prevent Bruised / Black Toenails

• Wear properly fitting shoes. Again, make sure your shoes have enough room for toe splay, but not so much that your feet are sliding around and bumping against the front of your shoes.
• Wear properly fitting socks. Socks that are too tight may restrict blood flow and cause unnecessary pressure on the toenail bed.
• Check your running form. If black or bruised toenails are chronic problem, a sports podiatrist could help you determine if toe-lifting and toegripping from tight shins or calf muscles are to blame. In these cases, physical therapy and/or corrective orthotics may help.
• Keep your toenails short to help prevent them from hitting the end of your shoe and causing more friction.

What to Do if You have a Painful Bruised Toenail During a Race:

If a bruised toenail is unbearable, seek medical attention. A professional may be able to perform a procedure called a Nail Trephination, where a small hole is drilled directly into the nail plate. This allows blood to drain the from under the nail, which can instantly relieve pain and pressure.

Environmentally Induced Breathing Issues

Breathing issues during an ultramarathon are not limited to those with pre-existing conditions, such as asthma or those suffering from a respiratory illness. “At the Tahoe 200 specifically, a bunch of runners experience a nasty ‘trail cough’.” says Klein “This is a result of spending literal days on end on the trail and constantly breathing in the dirt and dust.”

Breathing issues can also stem from other environmental factors such as extreme cold or heat, smoke, pollen, or altitude.

How to Prevent Breathing Issues during an Ultramarathon:

The most widely agreed upon way to avoid environmentally triggered breathing issues during an ultramarathon is to wear some sort of face covering.

“Wearing a buff or some sort or a hat with flaps that fasten around your face, or any sort of barrier will help filter out dust particles from the air you are breathing.” says Klein.

In extreme cold weather, a heat/moisture exchanger mask such as the Vapro Airtrim Cold Air Breathing Mask, will help protect lung tissue and function by warming the air you breathe.

Breathing Issues During an Ultra? Seek Medical Care

If you are experiencing breathing issues during an ultra, seek medical care immediately. A medical professional will be able to asses your condition, and help determine if you are having breathing issues due to something mildly obnoxious but likely not immediately threatening (such as irritation from dust and dirt) or something more serious such as Exercise-induced laryngeal obstruction, anaphylaxis, or something else that may require immediate attention.

Maceration (Trench Foot)

Maceration is the softening and breaking down of skin resulting from prolonged exposure to moisture.  It can range from mild cracking to extreme cases of pitting and peeled skin (commonly referred to as “trench foot”).

“Trench foot can get super gnarly if not handled appropriately. It can lead to infection, tissue necrosis, and could result in loss of the foot.” says Klein.

How to Prevent Trench Foot:

• Wear moisture wicking socks
• Change your socks often if they become wet.
• Use moisture absorbing powder, such as Anti-Monkey Butt, on your feet before putting on your socks

What to Do if You Experience Trench Foot:

Typical treatments for maceration of the feet include warming the feet, moisture-absorbing powder, dry socks, allowing the feet exposure to air to dry, and time.

Whatever you do: don’t ignore it. Maceration/trench foot will only get worse if unattended.

Musculoskeletal Injuries

When talking about muscle, bone, or joint injuries during an ultramarathon, we have two different types of injuries to discuss: acute or chronic.

An acute injury occurs due to something unexpected and traumatic happens, such as tripping over a root and spraining your ankle or breaking a toe.

A chronic injury is caused by the overuse of bones, muscles, or tendons that have not adapted to the specific demands of a given activity. In ultrarunning, chronic injuries are often seen in those who train and race far too much without adequate recovery, as well as those who do not train well enough (or at all), and attempt a race or distance their body is unprepared for.

How to Prevent Musculoskeletal Injuries During an Ultra:

• Train for the race. The biggest piece of advice I can give when it comes to preventing injuries to your bones or muscles during an ultra is to adequately and properly train for the race. This will strengthen your musculoskeletal system to withstand the repetitive demands of ultrarunning, while helping ensure you are not overtraining.
• Fuel your training. While this is a big picture suggestion, proper fueling throughout your training cycle will help ensure your musculoskeletal system is strong and healing adequately from training.
• Don’t fall. I know, easier said than done.

If You Suspect a Musculoskeletal Injury Mid Race…

Consult a medical professional. Not every injury requires you to stop your race, and an assessment by a professional will help you understand and weigh the risks and benefits of continuing on.

“Nobody wants anyone to DNF” says Klein. “A LOT of things are able to pushed through, and some are not. These are a case by case basis for a lot of things, and also depends on the mental state and grit of the person going through it.”

Chafing

Chafing is one of the more benign ailments that can happen during an ultramarathon, but it’s also one of the more painful and obnoxious things ultrarunners may experience.

Chafing is irritation of the skin that can occur in numerous places on a runner, typically anywhere that continuous rubbing of clothing, accessories, or even skin to skin contact occurs. Common sites of chaffing include between the thighs, on the shoulders under sports bra straps, or in the armpits.

How to Prevent Chafing During an Ultramarathon

To prevent chaffing, first ensure that you are wearing dry-wicking, technical fabric. Avoid cotton, as it is more likely to absorb sweat and irritate the skin. Second, generously apply an anti-chafing lubricant, such as Vaseline, or a sport specific product such as Body Glide to the areas that are most prone to chaffing. 

To avoid any surprise hot spots, race in clothing that you have previously trained in and haven’t experienced any issues with.

Already Chafing? What to do Next:

• Put a preventative layer of lubricant over the skin experiencing friction.
• Try to eliminate the source of friction, if all possible. If it’s a piece of clothing causing the irritation, change that clothing. If it’s something like a hydration pack strap, try placing a piece of KT tape over the skin to create a protective barrier.

Hypothermia

Hypothermia occurs when your body loses heat faster than it can produce heat, which results in lowering of the body’s internal core temperature several degrees below its normal 98.6 degree.  This is considered a medical emergency, and if left untreated, can result in death.

While many think of hypothermia that happens only in extreme conditions, the reality is that hypothermia deaths can occur with temperatures upwards of 50 degrees °F (10°C) 

Signs of hypothermia include:

• Shivering
• Slurred speech or mumbling
• Slow, shallow breathing
• Weak pulse
• Clumsiness or lack of coordination
• Drowsiness or very low energy
• Confusion or memory loss
• Loss of consciousness

How to prevent hypothermia during an ultra:

• Dress appropriately for the weather. Remember that in ultras – especially in later stages of the race – you may be moving much slower than you expect. You also may be covering more exposed and cooler terrain, such as hilltops and mountain peaks that experience more extreme temperature shifts. Be prepared.
• Wear layers – including moisture wicking layers closest to your body to help keep you dry and warm.
• Fuel adequately. High carbohydrate foods are easy for your body to digest and convert into energy. Body heat is a by-product of the metabolism of food. Therefore, fueling frequently and adequately with high carbohydrate foods can help sustain your body temperature.

What to do if you suspect hypothermia during an ultra:

Typically, those with hypothermia will be unaware of their dire situation as it’s happening, so it’s important to recognize these symptoms in other athletes or those you may be pacing/crewing, and immediately seek medical help.

Get the person warm and dry, while getting help as soon as possible.

Heat Stroke

On the opposite end of the extreme temperature spectrum, we have heat stroke. Heat stroke occurs when the body can no longer control its temperature: the body’s temperature rises rapidly, the sweating mechanism fails, and the body is unable to cool down. Heat stroke is also considered a medical emergency, and if left untreated, can result in death.

Signs of heat stroke include:

• Dark-colored urine or cessation of urinating
• Confusion
• Dizziness
•  Fainting
• Fatigue
• Headache
• Muscle or abdominal cramps
• Nausea, vomiting, or diarrhea
• Profuse sweating
• Chills
• Pale skin

How to prevent Heat Stroke during an ultra:

• Run in as little clothing as possible
• Wear sweat wicking clothing – evaporation of sweat off of your skin helps cool your body.
• Use ice or cold water in bandanas or buffs on your head or neck
• Slow your pace
• Utilize walk breaks
• Take breaks in the shade or cooler areas if possible.

What to do if you suspect heat stroke during an ultra:

If you experience any of these signs or symptoms while running in the heat, stop immediately, and seek help.

Related post: Summer Running Survival Guide: 10 Tips For Running In Heat & Humidity

Muscle Cramps

Another ailment that likely every single runner on earth has experienced at one point or another: muscle cramps. A muscle cramp is a sudden, unexpected tightening of one or more muscles. It can range from a dull ache to an overwhelming pain that will bring you to your knees.

Muscle cramps happen for a number of reasons, but the main causes associated with ultrarunning include fatigue of the muscle itself, electrolyte imbalance, and poor fueling.

How to prevent Cramping during an Ultramarathon:

• Adequately train for the race. Muscles that have trained to withstand the rigors of an ultramarathon will be able to run longer before experiencing fatigue.
  
  A study comparing athletes who suffered from cramps versus those who did not during a 161km ultramarathon suggests that those who experience cramps were placing greater demands on their muscles during the race relative to their current state of training (Hoffman et al).
• Properly fuel and hydrate. This seems to be recurring theme in this post!

Hyponatremia & Hypernatremia

Most people are familiar with the concept of dehydration. This occurs when inadequate amounts of water are consumed to compensate for fluids lost through normal bodily functions (urine, sweat, etc.) It can result in a condition known as hypernatremia, or when the sodium level in the blood becomes abnormally high because water loss exceeds sodium loss. 

But, equally as important is hyponatremia. Hyponatremia is a condition in which sodium (salt) levels in the blood become abnormally low. In the case of running, this can often happen because over overhydration, when a runner consumed too much water. While hypernatremia can be dangerous, hyponatremia has the potential to be deadly. 

When there is an electrolyte imbalance (from both over or under hydration), your body can experience a slew of negative side effects, from irregular or fast heart rate, to muscle cramping, nausea/vomiting, muscle weakness, irritability, headaches, confusion, and even convulsions or seizures that can lead to death.

Common symptoms of electrolyte imbalance include:

• Muscle cramping
• Headaches
• Muscle weakness
• Unexpected fatigue/lethargy
• Nausea/upset stomach
• Irregular heartbeat
• Rapid heart rate
• Dizziness/confusion

How to prevent hyponatremia & hypernatremia during an ultramarathon:

Similar to practicing your race day nutrition, it’s important to practice your race day hydration, in various potential race day scenarios. Know what your fluid and electrolyte needs are in different temperatures, at different distances, and while you are running at different intensities.

If you believe you are suffering from hypo/hypernatremia:

Stop running, and immediately seek medical care.

For more information on electrolytes while running, visit the post: Electrolyte Needs & Supplementation In Running Explained

Final thoughts:

If you’re not sure what to do, Klein says the most important thing you can do is tell someone, and let them help you figure it out. “Volunteers never want anyone to DNF, everyone has the same goal, which is to get each and every runner safely across the finish line. Do not be afraid to tell the Aid Station if something is going on.”

Klein says that certain medical emergencies, such as heat stroke, hyperthermia, acute fractures, or anything that requires an IV, are cause for stopping your race right then or there. But other ailments and injuries are typically left up to the athlete, and they are encouraged to get off the cot and keep going.

“I have seen nausea, chills, shivers, fatigue, be able to be managed and continue on after deemed safe to do so. Volunteers have your best interests in mind, don’t keep secrets from them.”

Resources:

• Hoffman, M. D., & Stuempfle, K. J. (2015). Muscle Cramping During a 161-km Ultramarathon: Comparison of Characteristics of Those With and Without Cramping. Sports medicine – open, 1(1), 24. https://doi.org/10.1186/s40798-015-0019-7
• Moshirfar, M., Ding, Y., Ronquillo, Y., Birdsong, O. C., & Murri, M. S. (2018). Ultramarathon-Induced Bilateral Corneal Edema: A Case Report and a Review of the Literature. Ophthalmology and therapy, 7(1), 197–202. https://doi.org/10.1007/s40123-018-0125-y