20 March 2014

Hypothermia and cold-induced injuries when trail running in the mountains

I am on Frankfurt airport on my way back to Sweden having been a couple of days on a business trip to Ottawa in Canada. It has been a great trip not the least due to the good training. It was a while since I was on a business trip now and I was surprised how well the running on the treadmill worked – it is quite easy to run way too fast and I therefore mix speed with climbing on the maximum incline (15 degrees on most machines). I climbed 1000 meters (3280 feet) each morning and in combination with running some kilometers at high speed and strength training for in particular my legs I feel like I am back in form after the long slow winter training.

It was certainly winter in Ottawa, however, with temperatures below  -20 degrees Celsius (-4  degrees Fahrenheit), yesterday and lots of snow – a real contrast to Uppsala where the spring was in full bloom when I left. I have not been much outside during this trip, and did not bring training clothes for running outside, but feeling the cold icy wind in the face made me almost long for putting on running shoes and head out in the snow. Now I had to settle for some walks through the inner city.
 
The Centennial Flame at Parliament Hill in Ottawa
The Parliament in Ottawa surrounded by snow and cold
One of my long-term dreams is to run one of the long winter races in North America like Yukon Arctic Ultra, Iditarod Trail Invitational or the Extreme Winter Ultra Marathon. There is a growth in ultramarathon trail racing in the winter and in Scandinavia there are now a number of winter races like Rovaniemi 150, Ice Ultra and ArvikaActic Ultra. There is also a growth in the number of winter fastest known time (FKT) running attempts and I have for instance with great interest followed the very interesting detailed race report in many chapters from the Swedish runner Otto Elmgart whoran alone from Kiruna to  Narvik, adistance of roughly 180 kilometers (110 miles) in a Project he calls Goodfire. While I think the cold will be a major challenge in winter races I think you are expecting it and therefore come much more prepared for it than during races in the summertime.  Unexpectedly changing weather leading to cold conditions and risk of hypothermia (body core temperature below 36°C (97 °F)) of the runners in summer races could be much more dangerous than constant cold during a winter race. I have in a previous blog post described some of the dangers with running in the mountains andnotably most of the deaths of runners during mountain trail races have occurreddue to hypothermia in summer races.

Looking in the literature for studies of hypothermia during mountain running there is surprisingly few studies published. Most studies published appear to be of military operations and the influence of fatigue on the thermoregulatory control, for instance coming from the research by John W Castellani at US Army Research Institute of Environmental Medicine in Natick, MA, USA (see for instance “Thermoregulation during cold exposure after several days of exhaustive exercise” published in J Appl Physiol 2001; 90: 939–946 and “Prevention of cold injuries during exercise” published in Med & Sci in Sport & Exer 2006; DOI: 10.1249/01.mss.0000241641.75101.64). That there is not much literature on the area was noted already in 2003 in the excellent review “Physiology of accidental hypothermia in the mountains: a forgotten story” by Ainslie and Reilly in Br J Sports Med 2003; 37: 548–550. In this review, the authors outline the dangers of switching from an activity of high metabolic heat production, like running or walking in the mountains, to an activity of low heat production, for instance due to slow down due to fatigue or an accidental fall. It can be rather difficult to manage this during a long mountain ultramarathon like Tor des Géants (TDG) and towards the end of the race you have certainly become more proficient in rapidly putting on and removing clothes depending on the surrounding terrain, temperature/wind/moisture conditions, and your exertion level. One study has found that clothing with at least four times as much insulation is required to maintain body temperature at rest at an effective air temperature of 0°C as when running at 16 km/h at the same temperature (Noakes “Exercise and the cold” Ergonomics 2000; 43: 1461–79). Extra clothes and an insulation rescue blanket required in most mountain trail races could certainly be life-saving and are clearly motivated not only during racing but also when training in the mountains. There have recently been a controlled study of the beneficial effects of clothing published by Burtscher et al entitled “Effects of lightweight outdoor clothing on the prevention of hypothermia during low-intensity exercise in the cold” Clin J Sport Med 2012; 22: 505-507.
 
Predisposing factors for hypothermia. From Castelanni et al 2006 

Obviously, the risk of frostbite is much higher during winter when ambient temperatures are constantly lower during races. However, at high altitudes with low temperature and winds the windchill effect might certainly be notable. I really suffered on my third night at Tor des Géants running down from Col Lasoney to the life base in Gressoney St Jean – it was only around 0°C and light snowfall, but the wind coming from the north was incredibly strong blowing away some of the reflective race track signs. When I came to the Ober Loo aid station on my way to Gressoney St Jean it felt like I had begun develop some frostbite on my checks and I stayed some extra time to warm up with a cup of Tea Caldo with plenty of sugar. It has been shown that hypoglycemia impairs shivering and increases the risk for hypothermia so the sugar was probably extra beneficial in this situation.  Looking at the windchill chart in consensus article “International Olympic Committee consensus statement on thermoregulatory and altitude challenges for high-level athletes” by Bergeron et al published in Br J Sports Med (2012). doi: 10.1136/bjsports-2012-091296, however, it was probably not that as the risk of frostbite at 0°C should be very low. For PTL this August I will bring a wind meter and thermometer to better assess the winc chill temperature (WCT) during the race. 
Wind Chill Temperature (WCT) chart from Meterological Society of Canada

Something which will not require an instrument to measure is rain and moisture and that this has an effect on the thermoregulation when running was recently shown in a Japanese study by Ito et al entitled “Effects of rain on energy metabolism while running in a cold environment” Int J Sports Med. 2013; 34: 707-11. In this pilot study, 7 healthy men ran on a treadmill at 70% VO2max intensity for 30 min in a climatic chamber at an ambient temperature of 5°C in the presence (RAIN) or absence (CON) of 40 mm/h of precipitation. Esophageal temperature and mean skin temperature were significantly lower (P<0.05) in RAIN than in CON, while minute ventilation, oxygen consumption and levels of plasma lactate and norepinephrine were significantly higher (P<0.05) in RAIN than in CON. The light snowfall making in particular my hands and face wet during the third night at TDG was certainly a contributing factor to my suffering. Another factor was probably that this was the third night and that I had been racing for over 60 hours and thus had started to become rather sleep deprived. That sleep deprivation can affect thermoregulation has also been studied, for instance in the study by Castellani et al entitled “Eighty-four hours of sustained operations alter thermoregulation during cold exposure” published in Med & Sci Sports & Exercise. 2003; 35: 175 – 181.

In summary, I think hypothermia is perhaps the most important objective danger during mountain ultramarathon races also during the summer months and proper preparations both to prevent and to take care of this should it occur during races is paramount.

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