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Hypothermia and Hyperthermia (Part 1)

Hypothermia and Hyperthermia (Part 1)


Last updated: 28-Jun-16

By Ian Corless

They sound the same don’t they? But don’t be confused. In the following two articles we will clearly explain the differences and do our best to inform you how to avoid it and what to do should it happen.

This article will be about Hypothermia but before we begin, let’s provide an initial explanation to avoid confusion.

Hypothermia - Refers to the cooling of the human body which in severe cases can result in death.

Hyperthermia - Refers to the elevated temperature of the human body due to a failure of thermoregulation and in severe cases can result in death.

The body’s core temperature is normally around 37 ºC. When the core temperature drops, Hypothermia starts to set in. A drop of 34-35 ºC signifies mild conditions whereas anything below 33 ºC is considered severe.

Let’s be clear here, conditions on the trail, fell or mountain don’t necessarily need to be bad for Hypothermia to set in. Running and moving fast creates heat and a runner can generate a great deal of heat in a short space of time. Imagine a scenario where you are moving fast and you have been travelling this way for say 2-hours. You are warm, no hot! You are a little fatigued, hungry, a little dehydrated and then disaster happens… you fall and twist an ankle.

Suddenly moving becomes impossible and you start to cool.

I probably don’t need to elaborate too much here as it’s very easy to see and visualize the scenario that follows.

Low blood sugar, low energy, a cooling body and mild Hypothermia starts to set in. I need to be clear, conditions do not need to be bad or inclement for this to happen! However, imagine the scenario where conditions are bad - rain, wind, snow, ice, wind-chill and so on. The Hypothermia process is then escalated and speeded up rapidly requiring much faster action.

As the body cools, certain things start to happen and in mountain running we always warn runners of the possible signs of Hypothermia – Mumbles, Grumbles and Stumbles.

Look out for:

  • An inability to make decisions
  • Shivering
  • Confusion
  • A reduction of consciousness
  • Slurred words
  • Odd behaviour and so on

In severe cases any shivering may well stop and you will see visual signs of change such as blue lips.


  • Speed is of the essence with Hypothermia as mild conditions can spread to severe and critical quite quickly.
  • Assuming that you have additional clothing (you should have) put as many layers on as possible including hat, gloves, warm base layer and windproof. If you or the person are wet from rain, ideally you would remove wet layers and replace with dry.
  • Ideally eat sweet foods. Avoid coffee, tea and alcohol but it is possible to drink warm or hot water for example if this is an option.
  • If possible, get off the mountain and to safety as soon as possible. If this is not possible, try to find shelter. If you are unable to move add as many layers as possible and seek assistance from the emergency services.
  • Try to keep awake and keep a potential Hypothermia case awake if you are looking after someone.

Of course, the above is not a comprehensive and fool-proof guide as mountain conditions and the condition of the casualty should indicate what action to take.

Do not try to evacuate a severe or unconscious casualty. Seek the services of the professionals with an emergency call.

All of the above can be avoided with good mountain practice and skills.

The recent trends and desires to move fast and light are all well and good when you can move fast. However, when you can’t move fast, that is when problems arise. This is why many races have mandatory kit. A race takes it upon itself to protect you, from yourself.

This mandatory kit should be something that you take with you on all your mountain journeys, be that in training or racing. The more extreme the terrain, conditions or risk of adversity, the more equipment you should take.

As a minimum carry with you:

  • A pack that can carry at least 1ltr of liquid with capacity for mandatory kit
  • A waterproof jacket and trousers to protect from the elements
  • A base layer
  • A down or Primaloft© jacket
  • Hat
  • Gloves
  • Buff
  • Space Blanket
  • Compass (know how to use it)
  • Map (know how to read it)
  • Whistle
  • Mobile phone
  • Spare food

For more extreme conditions, consider the following:

  • Bivouac bag
  • Sleeping bag
  • Spot tracker or similar
  • Stove such as a Jetboil©
  • Dehydrated meal

The above to some of you may sound extreme, believe me, when you need the above, you will really need them and you will be more than thankful that you have them with you.

Good Practice

Ideally always go to the mountains or remote challenging locations with company - buddy up!
Check the weather and make a sensible decision based on you, your ability, your objectives and skill level.

Know the route that you are taking and tell a friend or family member where you are going, when you are going and when you anticipate to return.

Have a contingency plan with options to shorten or abort a route.

Have a mobile phone that is charged and contains relevant contact numbers - 112 is Mountain Rescue (GSM standard, EU and other countries) or phone 999 (UK and other non-European nations) if that fails.

Can you read a map, take a bearing or do you have a phone or GPS device that will give you a location? This will be essential when requiring help. If you can provide a grid reference you will be rescued far quicker than a rescue party that needs to search for you.

Look after each other and look after others on the mountain.

Know whistle signals - six blasts every minute signifies an emergency.

Hypothermia can happen to anyone, even the most experienced runners or mountaineers. However, if you are sensible, have the necessary equipment and understand your ability and the ability of those around you, the risk of Hypothermia should be reduced greatly.

In the next article we will look at Hyperthermia.

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