Difference between revisions of "Hypothermia"

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[[File:2014Graveyard100.jpeg|right|thumb|500px|The Graveyard 100, taken by [http://www.flickr.com/photos/triple_f/ Frank Lilley], used with permission.]]
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Hypothermia can occur in surprisingly warm conditions. In fact, hypothermia occurs as often in summer as it does in winter and the belief that hypothermia is related to cold weather can leave runners unprepared and vulnerable.  
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With the kinder weather in 2014, the graveyard 100 went well for me. I started at a gentle pace, and was in 10th place by the first aid station at mile 21. By this point I knew that two of the top runners in the race were way ahead of me, so I continued on at a conservative pace. By the second aid station at mile 42, I was in fifth place and feeling strong, but the leader was now nearly an hour ahead. What the half-way point my pace started to slow a little and while I was feeling strong, I didn't have the ability to speed up. The second half of the race is generally made up of long, featureless, barren and inhospitable stretches of straight road. I generally love the solitude of ultrarunning, but these sections will mentally corrosive and deeply lonely. In many ways this part of the race was remarkably like treadmill running, with no sense of progress or change. I was still in fifth place at the fourth aid station, but I unknowingly passed the fourth-place male, Jan-Erick Olson, in the fifth aid station at Cape Hatteras lighthouse. I learned later that he was [[Hypothermia| hypothermic]], though I don't know if this was because he'd slowed up and become chilled, or if he'd overdressed, becoming chilled when he sweated through the extra clothing. I passed the lead female, Connie Gardner, in the last few miles. I finished in fourth place in 16:48:30, which was okay, though I was two hours behind the winner!
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==The first casualty==
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=What Worked and What Failed=
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One thing that makes hypothermia particularly dangerous for a runner is captured in the saying "The first casualty of hypothermia is good judgment." If you are hypothermic your decision making is likely to be impaired, which leads to further dangers. 20-50% of deaths due to hypothermia involve the victim undressing, a symptom related to severe hypothermia. Poor decision making when running can be extremely dangerous, such as when crossing the road or navigating in the back country.  
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As always, I like to document the successes and failures of each major race. This time around I am combining the successes and failures into a single list, as there were no major problems, just a few caveats to the successes.
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==Risk Factors==
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* '''Pace'''. Overall I think I paced the race reasonably well, and finished strong. The first third of the race was run at an effortless pace; almost of the same effort level is sitting on the couch. It is possible that a more aggressive start would have given me a better overall time, but it's also possible that it would have cause a meltdown and a much poorer time.
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There are a number of risk factors for hypothermia in runners.  
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* '''Fuel'''. For this race I used [http://www.amazon.com/Ensure-Complete-Balanced-Nutrition-Chocolate/dp/B000ARTNJW Ensure Plus] as my primary source of calories rather than my usual [[Fellrnr's Go Juice| Go Juice]]. This was partly to experiment with a higher fat intake, and partly to reduce the stress on my wife who was crewing. Mixing the drinks is a real pain for the crew, and the Ensure Plus seemed to work quite well. I ended up drinking more than I expected, getting through 16 bottles, which gave me 5,600 Calories, 176g fat, 800g carbs, and 208g protein. The Ensure Plus remained palatable right to the end, and I might have had more of them if I brought a sufficient supply. Other than the Ensure Plus, I had a couple of soft, chewy cookies, but nothing else solid. I did fill a cup with Coke at aid station 3 (65 miles) and found myself cradling the bottle like a mother with a newborn baby, repeated filling and emptying the cup until I'd consumed a good portion of the 2 liters.  
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* '''Air Temperature''' This is the obvious factor, but it is the most deceiving. Hypothermia is likely at 50f, and can occur at much warmer conditions.  
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* '''Fluid'''. I drank nearly 2 gallons of my [[DIY Electrolyte Drink]], and this kept the well hydrated.
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* '''Wet''' As the water evaporates, it cools your body making the effective temperature much colder. Wet clothes also have far less insulation value, though wool and good synthetic fabrics are better than cotton. When running in cool conditions, it is important not to overdress and sweat through your clothing. Instead, try to carry excess clothing, or wear clothing that can be adjusted by opening zippers.  
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* '''Morton Stretch'''. The [[Morton Stretch]] worked amazingly well, and every time I did it, I felt stronger and smoother afterwards.
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* '''Wind''' The movement of air will suck the heat from your body, and if you are wet, it will increase the evaporative cooling. Remember that running in still conditions will create air movement over your body.  
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* '''Downhill Training'''. It may seem bizarre to do [[Downhill Running| Downhill Training]] to prepare for a completely flat race, but I'm convinced that this is the reason why my quads remained stronger and pain-free throughout the race. In fact I had no quad pain or [[Delayed Onset Muscle Soreness]] after the race. [[Downhill Running| Downhill Training]] is so effective for a flat race because it builds up resistance to the eccentric stresses involved in the running, even running on the flat course.
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* '''Rain''' Rain will obviously make you wet, but heavy rain will directly chill you and torrential rain can rapidly trigger hypothermia. I've had moderate hypothermia hiking on a 95f day when a summer storm occurred, soaking me cold rain.  
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* '''Mental tricks'''. 100 mile race is always an immense mental challenge, and the longer barren stretches of the graveyard exacerbate this. I found a number of mental tricks that I've used on other races became particularly valuable.
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* '''Exhaustion''' If your body as low energy, you will struggle to keep warm in conditions where you would otherwise be comfortable. This means longer runs and races increase the risk for hypothermia.  
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** To overcome the sense of not making progress, I would pick a landmark and run to it, then pick the next landmark. Sometimes these landmarks would be anything from a sign to a piece of trash by the road. This worked most of the time, but some stretches are so desolate that there is nothing to fix your eyes on other than the horizon. At these points in the race, all you can do is keep your head down and avoid looking at how far you have to go.
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* '''Slowing up''' Running generates a lot of heat, and generally makes the perceived temperature 20f warmer than the actual temperature. This means that slowing up or stopping can cause you to become chilled, especially if you've been running at a faster pace. I have been comfortable while running in cool rain, and become mildly hypothermic within a couple of minutes of stopping, then moderately hypothermic within 10 minutes.  
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** Like any ultra, I find it's important not to think about the overall distance, but to run to the next aid station/crew access point.
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* '''Sun down''' The risk of hypothermia increases when the sun goes down, partly because the heat from the sun is lost, but also this is the time that the temperature drops the fastest. In a long race, this is often a psychological and physiological low point, creating a perfect storm.
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** I usually listen to music when I run, but on this ultra I found myself focusing more on the music and really listening to it.
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** Having read books on willpower, I was more aware on this race of conserving my mental energy. While I normally do most of my creative thinking while running, on this ultra I focused more on [[Stillness in Motion]], I'm letting my mind rest.
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==Symptoms==
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* '''Digestion'''. I had no digestive problems on this race at all, which with my history of nausea was truly pleasant.
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* If you are with someone in potentially hypothermic conditions, the first symptoms may be the "umbles" – stumbles, grumbles, mumbles, fumbles. Remember that you may be doing fine when your companion is suffering. Beware doing anything that puts you at risk from hypothermia when helping someone else; never create a second victim. You can’t help someone if you are also impaired.  
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* '''Mood state'''. Early on in the race I was chatting to another runner and joking about that point in an ultra where you start longing for a broken leg so you'd have a good excuse to stop. Although I did encounter some mild depression midway through the race, it was nowhere near as bad as I've had on other longer races. To my surprise, I didn't even have the usual angst that occurs as it gets dark and deep instinct cuts in that tells you that you should be safely indoors instead of out running.
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* If you are shivering, but can stop if you make an effort, you are suffering from mild hypothermia (core 96-98f). This will reduce your coordination, which could be a problem on technical trails. The biggest problem is that mild hypothermia will make you mildly stupid, and less lightly to make good decisions. It is important at this stage to correct the problem as soon as possible.
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* '''Sunburn'''. In last year's race I sunburned my arms rather badly, so this year I wore my long sleeved [[UnderArmour HeatGear Top]]. This thin white top protected me from the sun and helped keep my temperature stable. In addition to the well-known long-term health risks and short term pain of sunburn, there are more immediate consequences for a runner. The redness of sunburn prevent your body from conserving heat when it's cold, and the skin damage limits sweating when it's hot. This means that sunburn makes it much harder to control your body's temperature. Sadly, I didn't think to put on my sun cap that would have shaded my neck and face, so these areas did get sunburned.
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* If you are shivering and cannot stop even if you try, you have moderate hypothermia (core 91 - 95). Coordination is likely to be obviously impaired and your skin is likely to be pale, possibly with blue lips, ears and fingers. This is a dangerous condition; you need to get warm and dry urgently.
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* '''Heart Rate Monitoring'''. I think I finally cracked the problem of my heart rate monitor strapped chafing during longer ultras, so it was nice to be able to have that information available. Sadly my, and Garmin 310XT ran out of power about mile 95, probably because I've not been using it for the last few months as I've been testing other devices. This meant that for the last hour of the race my subconscious was continually asking "are we nearly there yet", which was like running with an attention deficit three-year-old in your head.
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* If the shivering comes in waves, this is probably severe hypothermia. Other symptoms include difficulty speaking, very poor coordination and inability to use the hands. Collapse is likely at this stage and the victim may appear to be dead. (If you pull the victims arm away from their body and it curls back up, they are still alive.)
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=Course Overview=
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* There is some evidence that hypothermia may increase the oxygen consumption for a given exercise load<ref name="Campbell-1991"/>, as well as dramatically reduce muscular endurance<ref name="SustCold"/>, muscular force<ref name="Sargeant1987"/>, and muscular power<ref name="Sargeant1987"/>.
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For those of you who are thinking about running the graveyard 100 I thought I'd include my perspective on the course.
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==Prevention==
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* '''Currituck to Southern Shores''' (0-21 miles). This is some of the most pleasant on the graveyard 100, running through the lovely town of Duck, with low trees some sidewalks to get you away from traffic (most of the course is on the shoulder of the road).
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To avoid hypothermia it is important to be able to adjust your clothing to stay warm.
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* '''Southern Shores to South Nags Head''' (21-42 miles). This section with runs through an unending sequence of beach houses, and seems interminable at the time. However, you look back with fondness at this section when you're going through the later sections.
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* A hat can be tucked into your waist band and carried easily
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* '''South Nags Head''' '''to Hatteras Lighthouse''' (42-87 miles). Mostly this is empty and barren, with long straight, featureless straights, and more exposed to the wind than other sections. There are a few small towns you go through, but mostly it's empty. There is also one long bridge where you run on a narrow shoulder, but the race has a police car warning drivers approaching the bridge and all the vehicles a saw were gracious, polite and gave me lots of room. For the last 6 miles before the lighthouse, you can see the flashing beacon, so it's easy to feel like you're not making progress. This is made worse when you take the turn to go on the out and back to the lighthouse, which is much longer than you'd expect and feels like it's going the wrong way.  
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* A light waterproof jacket can be wrapped around your waist and it will boost the insulation value of your other clothing dramatically. This is particularly valuable if heavy summer storms are possible.  
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* '''Hatteras Lighthouse''' '''to Hatteras''' (87-100 miles). After the wilderness, this section seemed relatively friendly, with only a few stretches of emptiness. Even in the dark, the sight of houses and trees seemed a welcoming sight.  
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* Zippers on tops allows for quick and easy adjustment.
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[[File:Graveyard 100 Route.jpg|none|thumb|500px| The route of the Graveyard 100, starting near Corolla in the north and finishing in Hatteras in the south.]]
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==Dealing with Hypothermia==
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=The Graveyard Challenge=
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If in doubt, seek shelter, get warm and dry quickly. A delay is likely to result in impaired judgment, further increasing your risk. If you are with someone, especially if you are pacing them on a long race, monitor them for symptoms of hypothermia. Medical help is required for the more significant levels of hypothermia. Remember the saying "You're not dead until you're warm and dead". Even if someone appears to be dead, seek medical help as revival may be possible.  
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As with many ultras the weather is a variable that can make the race easier or tougher. However, the Outer Banks is notorious for changeable, violent weather, especially at this time of the year. I feel it's worth enumerating the issues you may face with the weather on this race, as they are more significant than other events.  
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==See also==
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* '''Wind'''. The wind is the most obvious factor, and a mild tailwind can make the race far easier. On the other hand, you could easily face strong headwinds that could make running hard or even impossible. Wind speeds of 20-30 MPH are common, and the difficulty of running into a headwind generally varies with the square of the wind speed. It is possible that the headwinds could dramatically reduce the amount of running that a participant could manage, requiring a lot more walking than anticipated.  
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* [[Running in the Cold]]
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* '''Cold & Rain'''. The day before the 2014 race had high winds and near freezing rain that felt viciously cold. Running the full race under these conditions would create a high risk of [[Hypothermia]], especially for anyone who is running and has to slow to a walk, when their temperature could plummet.
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==References==
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* '''Sand'''. The Outer Banks is sandy, and the high wind can create a sandstorm that would make the race tremendously unpleasant, both for the runner and the crew. Sand also becomes an issue as an abrasive, getting into shoes and clothing.  
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<references>
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* '''Flooding'''. The rain and storms can create flooding, and the 2013 race had to be an out and back due to the resulting road closure. Even minor flooding can make progress harder, especially when the flooding involves deeper water over thick sand. Trying to make progress over deep sand is tough, especially as you can't see what you're stepping on. Also, small areas of flooding that cover part of the road will create a one way area for cars, and the runners have to contend for that narrow area.  
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<ref name="Campbell-1991">AP. Campbell, BD. Sykes, Effects of internal motions on the development of the two-dimensional transferred nuclear Overhauser effect., J Biomol NMR, volume 1, issue 4, pages 391-402, Nov 1991, PMID [http://www.ncbi.nlm.nih.gov/pubmed/1841707 1841707]</ref>
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* '''Heat'''. You are unlikely to face hot temperatures at the Graveyard, but a mild tailwind and full sun means the perceived temperature is higher. In 2014 there were times when the tailwind was about the same as my running pace, so I was travelling in a small pocket of stagnant, warm air.
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<ref name="SustCold">The duration of sustained contractions of the human forearm at different muscle temperatures http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1356726/ </ref>
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* '''Sun'''. Because the temperatures are generally cool it's easy to forget how strong the Carolina sun is this time of the year. Sunburn creates the immediate damage to the skin that limits sweating in the heat and reddening that can cause excessive heat loss in cold conditions. There are also the longer term problems of the pain and possible cancer.
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<ref name="Sargeant1987">Anthony J. Sargeant, Effect of muscle temperature on leg extension force and short-term power output in humans, European Journal of Applied Physiology and Occupational Physiology, volume 56, issue 6, 1987, pages 693–698, ISSN [http://www.worldcat.org/issn/0301-5548 0301-5548], doi [http://dx.doi.org/10.1007/BF00424812 10.1007/BF00424812]</ref>
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</references>

Latest revision as of 16:17, 10 March 2014

Hypothermia can occur in surprisingly warm conditions. In fact, hypothermia occurs as often in summer as it does in winter and the belief that hypothermia is related to cold weather can leave runners unprepared and vulnerable.

1 The first casualty

One thing that makes hypothermia particularly dangerous for a runner is captured in the saying "The first casualty of hypothermia is good judgment." If you are hypothermic your decision making is likely to be impaired, which leads to further dangers. 20-50% of deaths due to hypothermia involve the victim undressing, a symptom related to severe hypothermia. Poor decision making when running can be extremely dangerous, such as when crossing the road or navigating in the back country.

2 Risk Factors

There are a number of risk factors for hypothermia in runners.

  • Air Temperature This is the obvious factor, but it is the most deceiving. Hypothermia is likely at 50f, and can occur at much warmer conditions.
  • Wet As the water evaporates, it cools your body making the effective temperature much colder. Wet clothes also have far less insulation value, though wool and good synthetic fabrics are better than cotton. When running in cool conditions, it is important not to overdress and sweat through your clothing. Instead, try to carry excess clothing, or wear clothing that can be adjusted by opening zippers.
  • Wind The movement of air will suck the heat from your body, and if you are wet, it will increase the evaporative cooling. Remember that running in still conditions will create air movement over your body.
  • Rain Rain will obviously make you wet, but heavy rain will directly chill you and torrential rain can rapidly trigger hypothermia. I've had moderate hypothermia hiking on a 95f day when a summer storm occurred, soaking me cold rain.
  • Exhaustion If your body as low energy, you will struggle to keep warm in conditions where you would otherwise be comfortable. This means longer runs and races increase the risk for hypothermia.
  • Slowing up Running generates a lot of heat, and generally makes the perceived temperature 20f warmer than the actual temperature. This means that slowing up or stopping can cause you to become chilled, especially if you've been running at a faster pace. I have been comfortable while running in cool rain, and become mildly hypothermic within a couple of minutes of stopping, then moderately hypothermic within 10 minutes.
  • Sun down The risk of hypothermia increases when the sun goes down, partly because the heat from the sun is lost, but also this is the time that the temperature drops the fastest. In a long race, this is often a psychological and physiological low point, creating a perfect storm.

3 Symptoms

  • If you are with someone in potentially hypothermic conditions, the first symptoms may be the "umbles" – stumbles, grumbles, mumbles, fumbles. Remember that you may be doing fine when your companion is suffering. Beware doing anything that puts you at risk from hypothermia when helping someone else; never create a second victim. You can’t help someone if you are also impaired.
  • If you are shivering, but can stop if you make an effort, you are suffering from mild hypothermia (core 96-98f). This will reduce your coordination, which could be a problem on technical trails. The biggest problem is that mild hypothermia will make you mildly stupid, and less lightly to make good decisions. It is important at this stage to correct the problem as soon as possible.
  • If you are shivering and cannot stop even if you try, you have moderate hypothermia (core 91 - 95). Coordination is likely to be obviously impaired and your skin is likely to be pale, possibly with blue lips, ears and fingers. This is a dangerous condition; you need to get warm and dry urgently.
  • If the shivering comes in waves, this is probably severe hypothermia. Other symptoms include difficulty speaking, very poor coordination and inability to use the hands. Collapse is likely at this stage and the victim may appear to be dead. (If you pull the victims arm away from their body and it curls back up, they are still alive.)
  • There is some evidence that hypothermia may increase the oxygen consumption for a given exercise load[1], as well as dramatically reduce muscular endurance[2], muscular force[3], and muscular power[3].

4 Prevention

To avoid hypothermia it is important to be able to adjust your clothing to stay warm.

  • A hat can be tucked into your waist band and carried easily
  • A light waterproof jacket can be wrapped around your waist and it will boost the insulation value of your other clothing dramatically. This is particularly valuable if heavy summer storms are possible.
  • Zippers on tops allows for quick and easy adjustment.

5 Dealing with Hypothermia

If in doubt, seek shelter, get warm and dry quickly. A delay is likely to result in impaired judgment, further increasing your risk. If you are with someone, especially if you are pacing them on a long race, monitor them for symptoms of hypothermia. Medical help is required for the more significant levels of hypothermia. Remember the saying "You're not dead until you're warm and dead". Even if someone appears to be dead, seek medical help as revival may be possible.

6 See also

7 References

  1. ↑ AP. Campbell, BD. Sykes, Effects of internal motions on the development of the two-dimensional transferred nuclear Overhauser effect., J Biomol NMR, volume 1, issue 4, pages 391-402, Nov 1991, PMID 1841707
  2. ↑ The duration of sustained contractions of the human forearm at different muscle temperatures http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1356726/
  3. ↑ 3.0 3.1 Anthony J. Sargeant, Effect of muscle temperature on leg extension force and short-term power output in humans, European Journal of Applied Physiology and Occupational Physiology, volume 56, issue 6, 1987, pages 693–698, ISSN 0301-5548, doi 10.1007/BF00424812
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