Taking care: Trench foot, frostbite, and hypothermia

Note: This post is not to be construed as medical advice. The information contained herein is intended as a basic primer to a few limited conditions, and further information may be obtained by consulting with a qualified medical professional.


With prolonged exposure to cold temperatures comes the potential for a wide array of maladies, from the inconvenient to the life-threatening. Understanding this spectrum of danger is critical to your health and safety in a winter ultra.

In this post, we’ll cover three predictable and avoidable issues: trench foot, frostbite, and hypothermia. These conditions may not be a huge concern over the duration of a short race like the St Croix 40, but educating yourself about them must be a part of training for any winter ultra.

Trench foot

Trench foot is a condition that can arise from prolonged exposure to wet, cold environs (up to 60°F). Named for the WWI trenches in which this condition flourished, it’s a condition that’s easy to prevent and treat. Left unnoticed or untreated over long periods of time, it can lead to necrosis – tissue death – that may lead to the loss of toes or the onset of life-threatening infection.

When skin and tissue is submerged or wet, it becomes macerated – squishy, wrinkly, and prone to breakdown. Wet feet are likely to blister, and the skin will tear more easily. Add cold temperatures to this, and you have the added risk of capillary death. Not only will there be injury to the skin and surface tissues, but there will be reduced blood flow to those damaged tissues. No blood flow, no healing.

Because of the wet submersion factor, runners and hikers are more likely to suffer from trench foot than bikers.

Keeping the feet warm and dry is the recipe for prevention. In damp conditions, such as heavy slush or puddles, a vapor barrier – some kind of plastic or other latex/rubberized barrier – may be a good idea. A strategy as simple as a thin sock, covered by a cheap plastic bag, covered by a thicker sock could be useful for some participants.

Depending on conditions and the length of the race, participants may also wish to consider bringing a change of socks – or several.

Another common recommendation from seasoned veterans is to apply some sort of moisture-controlling agent. This could be talcum powder or a cream like Desitin. Both tactics have been used to good effect by long-distance, multi-day competitors.

This condition typically requires multiple days to set in, but good foot care should begin from square one. Know what your feet look like and practice checking them after each excursion.


Frostbite is a preventable condition that results from exposure to freezing conditions. Unlike trench foot, it doesn’t require the presence of moisture in order to set in. Exposed skin will be most at-risk, such as the nose and cheeks, but even gloved fingers and booted toes may suffer from frostbite.

When skin gets cold, it will first turn pink or red. As it begins to freeze, it will turn white and begin to feel warm. Catching frostbite at this early stage will likely lead to a quick – though uncomfortable – recovery. Once it progresses beyond this stage, deeper layers of skin and tissue will begin to freeze. Skin will continue to turn white or grey, and extremities will become numb. Joints may no longer bend. In this severe stage, the skin and extremities may turn black.

Left unnoticed or untreated, frostbite can lead to amputation of extremities.

If frostbite sets in, warming is critical. No participant of any winter race should be allowed to continue after severe frostbite has been warmed. Re-freezing of frostbite regions must not be allowed, or they will be permanently, irreparably damaged.

The prevention of frostbite is all about warmth. Keeping your body parts warm, covered, and moving is of the utmost importance. For the face, this may involve wearing goggles in windy weather, or using an anti-freeze, kinesiology, or medical tape on the cheeks and nose. For hands and feet, participants should develop their own layering strategy. Some conditions may warrant a single pair of gloves, while other conditions may call for bulky mittens or pogies.

Wet socks or mittens may accelerate heat loss, leading to frostbite.

Additionally, the onset of frostbite may be accelerated by stationary body parts; if your toes and fingers aren’t moving, blood flow will be reduced. Therefore, bikers may be more at risk for frostbite than runners or hikers, especially on their feet. Make sure your boots aren’t too tight and keep your toes moving.

To reiterate: Do not continue in your winter excursion if you have warmed frostbitten extremities. It is dangerous. Seek medical attention.

As with trench foot, vigilance will lead to success. Good foot care should begin from square one. Know what your hands and feet look like and practice checking them after each excursion.


Hypothermia is a condition that results from your body’s inability to generate heat faster than it is lost. Once the internal body temperature dips to 95°F, hypothermia has set in. Hypothermia is a preventable condition that, when left unrescued and untreated, can result in death.

When hypothermia sets in, shivering will usually be one of the first symptoms. (Note that this isn’t merely the feeling of being cold; you can feel cold for quite some time before hypothermia sets in.) Shivering should be addressed immediately, as it’s a sign that your clothing isn’t enough to keep your body warm. If unaddressed, shivering may lead to other symptoms such as slurred speech, lack of coordination, and confusion.

It is vital that you take action or reach out to fellow competitors if these first symptoms are noticed. Make a friend and stick together until you are able to seek help from a volunteer.

Confusion and memory loss have led winter ultra participants to abandon their gear, remove clothing, and wander off-trail into the wilderness. Hypothermic individuals are no longer able to make good choices or care for themselves. Eventually, severe hypothermia will lead to loss of consciousness.

Hypothermia can be prevented by dressing appropriately for the weather conditions. Layering will be your best possible choice; maintaining a warm base layer and bringing a variety of layers allows you to customize what you need at any given moment. Good ideas include a windbreaker, down jacket, a variety of hats and gloves, face masks, and snow pants.

Bringing too many layers is far preferable to bringing too few. Dragging an extra few pounds in your sled because you didn’t need your heaviest down layer will always be better than risking hypothermia on the trail.

Take note: Just as under-dressing can expose you unduly to the cold, over-dressing and working up a sweat can also contribute to the possibility of hypothermia. If you become too warm, either through over-dressing or over-exertion (or both), it’s a good idea to remove layers incrementally and keep them handy. Once you cool down and your sweat begins to dry, you’ll likely become very cold, very quickly. Be prepared to layer back up.

This balance of layers and effort is a personal one, and participants should always experiment before race day.

Of the three issues listed here, hypothermia is the most frightening. It’s why gear requirements for winter ultras are stringent, and it’s why you must know how to use your safety equipment. Having an insufficient bivy setup will expose you to the elements and leave you vulnerable. It isn’t worth the risk.

As you consider stepping into longer, more challenging efforts, please take these safety risks seriously. The 2018 Yukon Arctic Ultra had two participants suffer amputations due to frostbite. The 2018 Iditarod Trail Invitational nearly lost a participant to hypothermia. Winter ultras are survivalist races and deserve the utmost respect for their difficulty.

Watch out for your fellow competitors. Pay attention, talk to them. If someone is behaving oddly, travel with them or seek help. 

At gear check, you may be asked a question or two from this information. A packet of this information will be kept at the Trail Center, and if you’re unable to answer the general questions asked, you will need to look over the packet before being allowed to participate.


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