29 December 2014

Ridge running

We got a white Christmas in Uppsala after all and the past days have been absolutely stunning with snow and temperatures down to - 20°C (- 4°F). The time between Christmas and New Year is a time for reflection – reminiscence of the year past and envisioning of the year to come.  For me 2014 was a great running year with everything focused on Petite Trotte à Léon (PTL) in August. Both the training and planning before the race were great and, even though there of course are things I would change now knowing how the race went, I think I was as prepared as I could be. The race itself was an experience of a lifetime, as I have written in a previous blog post, and I am immensely grateful to have done it together with Otto Elmgart. Otto is still writing a story, in Swedish, about our long voyage around Mont Blanc, and it is very interesting and educating to relive the race through the eyes of a friend and fellow runner. As with Tor des Geants in 2013, there is not a single day when I do not think about the race. The initial nightmares I had of the bad moments have gradually transformed into good dreams about the challenging moments in the beautiful mountains. I recently got the courage to look through the photo material from PTL again. My skills as a photographer are regretfully indeed limited, but I at least attempted to clip together a short movie of ridge running when we after around 48 hours in the race passed the ridge to Pointe de Chaligne above Aosta in the Aosta Valley in Italy and when we the last evening after 120 hours ran along the beautiful ridge of Mont Jolly (see maps below). The runner in front of me in a yellow jacket is Otto. It is moments like those that make nightly runs in mid-winter freezing temperatures so much easier.
The ridge to Pointe de Chaligne

The ridge to Mont Joly

18 December 2014

Snowfall, running, skiing & mountains

This morning we had the first real snowfall of the year in Uppsala. Regretfully, the snow will likely disappear to Christmas as it is going to be warmer and rain already tomorrow. Until then I am really enjoying the shining bright light from the white ground – it has been incredibly dark without snow the past two months. I also very much prefer to run in snow rather than in slippery icy and freezing water as I have been doing during many runs the past weeks. It is not only the traction that is better; there is something about the softness of snow for the feet that is very pleasant. I have previously written about running in snow and sand from a physiological perspective, and even though there are no direct studies on running on snow specifically, I am convinced that it is a good training form just as running on sand. And, it is indeed quite fun, at least during the early winter season when the snow is new.

The first real snow of the season in Uppsala
There are no mountains in Uppsala and when I am in more mountainous terrain, as the coming weekend, I rather ski or go on snowshoes on snow. It is definitively more efficient and also more fun. It is however clearly different and it is interesting to see how much the biomechanics of walking with snowshoes differ from normal overground walking at a similar speed (Browning et al “Biomechanics of walking with snowshoes” Sports Biomech 2012; 11: 73-84). It is more energy demanding with a higher metabolic rate to walk/run on snowshoes, probably as the snowshoeing gait is characterized by a more flexed posture during stance and a greater degree of plantarflexion during swing. This ‘shuffling’ gait suggests foot position is controlled during this novel task and likely contributes to the increased metabolic rate.

Needless to say, also ski mountaineering (Skimo) has a very different biomechanics than walking or running (see for instance Tosi et al “The energy cost of ski mountaineering: effects of speed and ankle loading” J Sports Med Phys Fitness 2009; 49: 25-9; Tosi et al “Energy cost and efficiency of ski mountaineering. A laboratory study” J Sports Med Phys Fitness. 2010; 50:400-6; Duc et al “Physiology of ski mountaineering racing” Int J Sports Med 2011; 32: 856-63; Haselbacher  et al “Effect of ski mountaineering track on foot sole loading pattern” Wilderness Environ Med 2014; 25: 335-9). If snowshoeing is strenuous, ski mountaineering is extremely demanding and requires extremely high energy demands, which sometimes are difficult to fulfill as shown in a new interesting study of athletes competing in the Patrouille des Glaciers racecourses (Praz et al “Energy expenditure of extreme competitive mountaineering skiing” Eur J Appl Physiol 2014; 114: 2201-11). From a physiological perspective I can understand why mountain ultra trail runners such as Kilian Jornet and Emelie Forsberg appear to thrive and benefit so much from ski mountaineering during large parts of the year – it is simply one of the best endurance training forms there is.

Ski mountaineering also makes the middle and high mountains accessible not only during some short summer months, but for a much larger part of the year. I have become more and more interested in spending more time in the mountains also during the winter, and then not only in the pisted slopes but also backcountry, but my problem up until now has been my rather limited technical ski proficiency. While I virtually grew up with running shoes on my feet, it is not until a couple of years ago when I started with downhill skiing. I have greatly benefited from having a son who became interested in downhill skiing already when he was two years old and who now when he is eight is training and racing in alpine skiing (his favorite discipline is super-G), so I am spending a lot of time in the mountains now also during winter with my family, and this season I am hopefully good enough to at least start to train ski mountaineering. In contrast to running it is however a quite expensive sport in that there is so much more equipment needed – leaving the pisted slopes there will be a need of for instance different skis and ski boots and avalanche safety equipment. The latter is something essential as the objective dangers in the mountains during winter is so much higher than during the summer – if there is less than five runners dying each year on summer trails in the world there are over 150 people dying in avalanches in North America and Europe each year (a good recent review about avalanches and evidence-based guidelines about treatment is Brugger et al “Resuscitation of avalanche victims: Evidence-based guidelines of the international commission for mountain emergency medicine (ICAR MEDCOM). Intended for physicians and other advanced life support personnel” Resuscitation 2013; 84: 539-546). However, I am convinced that as with summer mountain trail running the risks can certainly be reduced greatly by proper training and preparations and it will be really fun to start doing this.
And, lastly, the mountains are almost more beautiful with snow – I just love the movie "The Ridge" below by Anson Fogel for Camp4 Collective  It was filmed in the Denalin National Park on June 25, utilizing Brain Farm Digital Cinema’s Cineflex technology. Completely amazing.

09 December 2014

Mountain Art

One of my absolute favorite mountain ultratrail blogs since many years is Trailplodder by the finish runner Jukka Kukkonen. It was actually his attempts to run La Boucle (now called X-Alpine) of Trail Verbier St Bernard that inspired me to take on the challenge of running that race in 2012 and it was then I really got hooked by mountain running in the Alps. His race reports in particular are truly inspiring and very educating and full of great pictures and it has been a joy to follow his success this year in finishing UTMB, Lavaredo Ultra Trail and Eiger UltraTrail, the last two races definitively high on my future bucket list. However, his blog also contains good, sometimes quite philosophical, reflections about mountain running in general and I was very happy to view the mountain art collection he has compiled and recently posted. His Mountain Art Gallery consists of 100 paintings at Google Cultural Institute and I can definitively recommend a tour.

Living in Uppsala, a city in the very flat county Uppland with the highest hill raising only 118 meters over sea level, it is certainly necessary to dream away to higher mountains when training and it is something I often do during my numerous short hill repeats.

The small and ugly, but still loved, hill on my way to work this morning
I have therefore like Jukka watched mountain art for quite some time and my favorite painter, at least for now, is the German Torben Giehler. We are of the same age and I can very much relate to his abstraction and illusionistic style and the overreaching idea that space is truly the final frontier in painting. His mountain paintings, expressed in pixilated aesthetic bright colors, resemble an inner structured virtual grid of the climbing of the summits as a mirror image of the unpredictable environment outside in real life. Giehler’s virtual studio with many of his paintings are located at http://www.torbengiehler.com/. His mountain art is mostly from 2002, but he has also done some paintings of mountains last year, for instance of Cervino/Matterhorn.

Torben Giehler's paintings Mont Blanc and Matterhorn from 2002

08 December 2014

Race plan 2015

The miracle did not happen this weekend, except for some elite runners, and my race plan for next year is therefore now more certain. As I had “only” waited two years and this was the second time I participated in the Hardrock 100 lottery I had only a 2.5% chance of getting entrance to the race. Next year I will have a "stunning" 5% chance of acceptance (yes, I am being ironic), and the fourth year the chance will approach 10% - but it is likely going to be even less as I except that the number of participants in the lottery will continue to increase in the coming years.  My qualification race for the last two lotteries has been the Tor des Géants 2013 and, since I focused on Petite Trotte à Léon (PTL) last year, that means I will have to participate in a qualifying race in next year if I want to stay in the lottery. While that is relatively easy in the US with plenty of 100 mile races, here in Europe there are only four possible qualifying races; Tor des Géants, UTMB, Ultratrail Ehunmilak and Ronda del Cims. UTMB is also the subject of a rather severe lottery process and as I only ran PTL last year I have not the qualification points any longer so that is not a possibility. I am still considering Tor des Géants for next year, it is an absolutely great race in a fantastic environment and the hospitality in the Aosta valley during the race is unprecedented and an experience in itself. However, it is also getting much harder to get entrance to this race. Remains Ehunmilak and Ronda del Cims. Even though I think both are really great races and I long to run in Spain and Andorra, I have decided to focus on other shorter more technically challenging skyrunning races at that time of next summer. So, it looks like I risk losing my place in the line in the Hardrock 100 lottery, but considering the odds it would probably have been many years before I would get entrance anyway. I guess you cannot achieve all your dreams and there are certainly other great races out there.

For 2015, my confirmed races so far are the following; firstly Ice Trail Tarentaise (ITT), a 65 km/5000 m D+ long skyrunning ultramarathon in Val d’Isère on 12 July. It is Europe’s highest skyrunning race with an average altitude of over 2500 m and the passage of La Grand Motte  at 3656 meters and L’aiguille Pers at 3386 meters. The course looks spectacular and I truly hope the snow conditions and weather permit the running of the full course next year. I was lucky to get a place in the race as it became full in just over one week.

Course of Ice Trail Tarentaise

Altitude profile of Ice Trail Tarentaise

The second confirmed race is Mont Blanc 80 km on June 26, a less technical, but still challenging ultramarathon with a D+ of 6600 km. As an early summer race it is also quite weather depending, as the highest points of the race are over 2500 meters (Col du Corbeau  at 2602 meter and Col de la Terrasse at 2643m) and the course passes some snow fields/minor glaciers. As it is only two weeks before ITT, which is my primary race, I will probably use this race as acclimatization to the altitude and mountain environment in combination with a short vacation in Chamonix depending on the family and work plans. I have looked at Mont Blanc 80 km for quite some time and as it is also a very popular race with a lottery process and here I was lucky to get entry for next year.
Course of Mont Blanc 80 km
Altitude profile of Mont Blanc 80 km

The third race where I have a slot is a short skyrunning race, Matterhorn Ultraks, on August 22. It is moderately technical and short, just 46 km with a D+ of 3600 meters, but it is in a stunning mountain environment in Switzerland around Zermatt with great views of Matterhorn and the surrounding mountains and valleys from the highest point of the race at Gornergrat at 3130 meters. I am still quite uncertain about this race, however, and are perhaps more inclined for a longer race like Echappee Belle (Ultra Traversee de Belledonne) , which is 140km with 10800m D+.  I am also considering Tromsö Skyrace earlier in August or Serre Che Skyrace in September. The registration for these races is not open yet and I guess it might be difficult to gain access at least to the Tromsö race.
Course of Matterhorn Ultraks
Altitude profile of Matterhorn Ultraks
The race I am most eager to run, but which I have promised myself and my family not to repeat in 2015, is PTL again. The UTMB organization just published the course for next year and it looks absolutely stunning with for instance a great passage of Tête de Licony near Morgex. Also some of the other passages are formidable.  I will certainly be envious of the teams taking on the challenge and I sincerely hope there will be at least one Swedish team participating.

The course of PTL 2015

02 December 2014

Exercise associated hyponatremia and ultramarathon running

November has come to an end. It was an unusually dark and cloudy month and I had actually not a single sun hour during the whole month. Something of a personal record, even worse than when I lived in Seattle one cloudy and foggy winter (and there you can always go up in the mountains). Indeed rather depressing, but from a running perspective it was a good month with warm temperatures and not too much rain. The training has been rather repetitious and I have been logging rather solid volume weeks, but without anything extraordinary. I am now looking forward to finalize my race plans for next year now so that I will get clear goals to train for and adapt my training to, but I am still waiting for the outcome of some lotteries. As the races I am considering are very different my upcoming training will to a great extent be dictated by this.

Fog during November morning commute run
I also hope I will be more inspired to write on the blog once I have clear goals. Now I have been rather content with reading others and there have neither been any new scientific articles or discussions regarding mountain ultramarathons prompting me to do research in a particular area. Nevertheless, the other day I came into a discussion again whether ultramarathon running is dangerous or not. It is a rather sensitive topic and some runners become quite agitated when someone says it indeed is dangerous. Even though it has not been shown in any good large prospective studies yet, I am personally completely convinced that ultramarathon runners, with an active lifestyle, in general are much healthier with less disease and lower mortality than people with an increasingly sedentary lifestyle. Future studies will tell me whether I am right, but early data from the ULTRA study of over 1000 ultrarunners indicated that it is correct (Hoffman & Krishnan “Health and exercise-related medical issues among 1,212 ultramarathon runners: baseline findings from the Ultrarunners Longitudinal TRAcking (ULTRA) Study” PLoS One 2014; 9:e83867).

However, I am also completely convinced that ultramarathon running, and in particular mountain ultra trail running, is quite dangerous. Just being in the mountain environment is dangerous and there is no way to avoid the sometimes lethal objective dangers on the mountain, as I have discussed before in my blog. I am also certain that running ultramarathons is quite stressful for the body and that it in some individuals can induce injuries and illness both long-term, like stress-fractures, and short-term, like exercise-associated hyponatremia (EAH), the subject of this blog post, that the affected person would not have experienced if he or she had not been putting the body to the stress of running for such long distances. The line between a healthy physiological reaction and a damaging pathological reaction to an endurance exercise is sometimes quite thin and to refuse to accept this is poor management of the subjective risks associated with ultramarathon running.

What provoked the discussion about whether it is dangerous to run an ultramarathon or not was a discussion about a post at one of the most popular Swedish trailrunning blogs where the blogger according to her self-described symptoms probably developed a very severe exercise-associated hyponatremia (EAH) during one of the UTMB races this year. It is clear from the post itself and the comments on it that the knowledge about EAH; its causes and its dangers in many ultramarathon runners appears clearly very limited. That is really sad as some knowledge about EAH literally can save lives. On the other hand, I barely had heard about EAH before I started running longer distances and there are indeed many erroneous conceptions about EAE. Some of the statements in the blog post we discussed clearly confirm this and I become quite agitated when erroneous and misleading information is given that can lead to more runners risking their health unnecessary. In the following I will at least try to give solid facts, at least as far as we know today in 2014, about EAH, ultramarathon running and hydration and to answer some of the common questions. My apologies again if the blog post is too technical.

What is Exercise-associated hyponatremia (EAH)?
EAH is defined as low serum or plasma sodium concentration below the normal reference range of 135 mEq/L (or  < 135 mmol/L) during or after exercise.

Good review articles about EAH is the WMS Practice Guideline about EAH published in 2013 (Bennett et al 2013 “Wilderness Medical Society practice guidelines for treatment of exercise-associated hyponatremia” Wild Environ Med 2013; 24: 228-240) and Rosner & Kirven’s review article from 2007 (Rosner & Kirven “Exercise-Associated Hyponatremia” Clin J Am Soc Nephrol 2007; 2: 151-161).

What is Exercise-Associated Hyponatremic Encephalopathy (EAHE)?
EAHE is EAH with symptoms of cerebral edema such as for instance altered mental status, altered level of consciousness, headache, convulsion/seizures or coma.

What are the mechanisms behind EAH?
There are three major pathological mechanisms behind EAH:

1) Excessive fluid intake (overhydration; water intoxication)
2) Impaired urinary water secretion largely due to persistent inappropriate secretion of arginine vasopressin (AVP) (also called antidiuretic hormone [ADH])
3) Failure to mobilize sodium (Na+) from osmotically inactive sodium stores in the body or alternatively inappropriate osmotic inactivation of circulating Na+

It appears that these mechanisms are needed together for development of EAH in most cases, except in those circumstances where the water intake is extremely excessive (>1500 mL/h). The causes of the inappropriate AVP secretion in EAH and its role in the disease is the focus of ongoing research (see for instance Cairns & Hew-Butler “Incidence of Exercise-Associated Hyponatremia and its association with nonosmotic stimuli of Arginine Vasopressin in the GNW100s ultra-endurance marathon” Clin J Sport Med 2014; Epub ahead of print; Hew-Butler “Arginine vasopressin, fluid balance and exercise: is exercise-associated hyponatraemia a disorder of arginine vasopressin secretion?” Sports Med 2010; 40: 459-79). However, it appears likely that in some individuals the stress of long endurance activities such as ultramarathon running might cause the high AVP secretion.

Main mechanisms behind EAH. From Bennett et al 2013
When was EAH first described?
The first case of symptomatic EAH was described in 1981 in a runner admitted to hospital after she became unconscious and had a grand mal epileptic seizure during the 56 mile (90 km) Comrades Marathon in Durban, South Africa. Her sodium concentration upon admittance to hospital was 115 mmol/L confirming EAHE. She recovered and regained consciousness after 2 days and was released from hospital after 4 days. This case and three other of ultra-endurance athletes were described by Noakes and colleagues in a seminal publication in 1985 (Noakes et al “Water intoxication: a possible complication during endurance exercise” Med Sci Sports Exerc 1985; 17: 370-5). Regretfully, it then took many years before the link between overhydration and EAH was widely accepted and hydration recommendations were changed (Noakes et al “Case proven: Exercise associated hyponatremia is due to overdrinking. So why did it take 20 years before the original evidence was accepted? Br J Sports Med 2006; 40: 567-72). It has regretfully also taken many years before a standard first-line treatment for EAH has been accepted (Moritz & Ayus “Exercise-associated hyponatremia: Why are athletes still dying?” Clin J Sport Med 2008; 18: 379-381).

What are the risk factors for EAH?
The risk factors for EAH has been studied in a number of large studies, for instance in 488 Boston Marathon runners (Almond et al “Hyponatremia among runners in the Boston Marathon” N Engl J Med 2005; 352: 1550-6) and following 2135 weighed competitive athletic endurance performances (Noakes et al “Three independent biological mechanisms cause exercise-associated hyponatremia: Evidence from 2,135 weighed competitive athletic performances” Proc Natl Acad Sci USA 2005; 102: 18550-55). The main confirmed risk factors for EAE are:

1) Excessive water intake (in particular > 1.5 L/h) during exercise
2) Pre-exercise overhydration
3) Long race time (> 4 hour)
4) Low Body Mass Index (BMI) (i.e. small athletes following fluid intake guidelines for larger individuals)
5) High Body Mass Index (BMI) (i.e. slower unfit athletes drinking generous amounts of fluid as they are exercising at a lower intensity)

In some studies female sex have been associated with a higher incidence of EAH, but when adjusted for body weight/BMI and race time this appears not to be an independent risk factor. The use of drugs such as non-steroid anti-inflammatory drugs (NSAIDs), selective serotonin reuptake inhibitors (SSRIs) and thiazide diuretics has also been associated with a higher risk for EAH, but further studies are needed to confirm this. No good study has compared the risk of EAH in various temperatures, but it appears that endurance exercise at either very high or very low temperatures might be a risk factor and more research is needed here as well.

Can you develop EAH in cold weather?
Yes, there are several case reports of EAH in cold weather conditions. Indeed, one of the highest frequencies of EAH in an ultraendurance event was recorded in the 100-mile Iditasport ultramarathon were 7/16 (44%) investigated participants were found to be hyponatremic (Stuempfle et al “Hyponatremia in a cold weather ultraendurance race” Alaska Med 2002; 44: 51-5).

Is EAH related to the sweat rate and/or content of the runner?
This is controversial and unclear. There is a highly variable degree of sweat rate and sodium loss from sweat (ranging from 15 to 65 mEq/L) and compared with the general population endurance athletes appear to have lower sweat sodium levels and loss of hypotonic sweat might raise serum sodium levels (Buono et al “ Sodium ion concentration vs sweat rate relationship in humans” J Appl Physiol 2007; 103: 990-994). However, on the contrary, sweat loss might also provide a stimulus to AVP release and impair urine excretion of water and in association with consumption of hypotonic fluids might lead to development of EAE. This might be one scenario for development of EAH in athletes with net weight loss. Furthermore, it has recently been investigated whether there could be any genetic association between impaired sweat function as in cystic fibrosis and EAH without finding any correlation (Lewis et al “The need for salt: does a relationship exist between cystic fibrosis and exercise-associated hyponatremia?” J Strength Cond Res 2014; 28: 807-13).

How common is EAH in ultramarathon running?
The incidence of EAH without symptoms (asymptomatic EAH) has in 100-mile ultramarathon races in North America been found to be between 30 and 51% (Stuempfle et al “Hyponatremia in a cold weather ultraendurance race” Alaska Med 2002; 44: 51-5; Lebus et al “Can changes in body mass and total body water accurately predict hyponatremia after a 161-km running race?” Clin J Sport Med. 2010; 20: 193-9; Hoffman et al “Hyponatremia in the 2009 161-km Western States Endurance Run” Int J Sports Physiol Perform 2012; 7: 6-10; Hoffman et al “Exercise-associated hyponatremia and hydration status in 161-km ultramarathoners” Med Sci Sports Exerc 2013; 45: 784-91). Interestingly, a recent small study of 15 runners of the Great North Walk (GNW) 100 ultramarathon showed that the incidence of EAH during any point during the race was 10/15 (67%) , while the post-race incidence was 4/15 (27%), indicating firstly that asymptomatic EAH might be even more common than this during ultramarathons, but also secondly that most runners are able to self-correct low sodium status.

The incidence of symptomatic EAH and EAHE in ultramarathon running is not known, but most likely below 5%. In collapsed runners of Boston marathon, 63/1319 (4.8%) runners were found to have hyponatremia (Siegel et al “Exertional dysnatremia in collapsed marathon runners: a critical role for point-of-care testing to guide appropriate therapy” Am J Clin Pathol 2009; 132: 336-340). Among the medical emergencies during an ultramarathon EAE is certainly something to be prepared for as a race organization (McGowan & Hoffman “Characterization of medical care at the 161-km Western States Endurance Run” Wilderness Environment Med 2014; Epub ahead of print). 

Is it only in ultramarathon running EAH is present?
No, even though the highest incidence rates of asymptomatic EAH has been reported in 100-mile ultramarathons, it has been found to be present in over 10% of athletes in other ultraendurance activities such as Ironman triathlon and open-water ultra-swimming (Knechtle “Nutrition in ultra-endurance racing – aspects of energy balance, fluid balance and exercise-associated hyponatremia” Medicina Sportiva 2013; 17: 200-10; Knechtle et al “Prevalence of exercise-associated hyponatremia in male ultraendurance athletes” Clin J Sport Med 2011; 21: 226-232). In shorter running races such as marathon the incidence of asymptomatic EAH can also be over 10%, (for instance in a study of Boston marathon runners 62/488 [13%] developed asymptomatic EAH [Almond et al “Hyponatremia among runners in the Boston Marathon” N Engl J Med 2005; 352: 1550-6]). Symptomatic EAH is rare and below 1% in marathon runners (Hew et al “The incidence, risk factors, and clinical manifestations of hyponatremia in marathon runners” Clin J Sport Med 2003; 13: 41-47), but it indeed occurs and even in shorter races such as half-marathon severe cases of EAH have been reported (Glace & Murphy “Severe hyponatremia develops in a runner following a half-marathon” JAAPA 2008; 21: 27-29). Symptomatic EAH has also been reported in hikers and military personnel with increased frequency. For instance in Grand Canyon hikers seeking medical care from exercise-associated collapse or exhaustion the incidence of EAH was 16% with an estimated rate of between 2-4 per 100,000 persons (Baker et al “Hyponatremia in recreational hikers in Grand Canyon National Park” J Wilderness Med 1993; 4: 391-306 and Baker et al “Exertional heat illness and hyponatremia in hikers” Am J Emerg Med 1999; 17; 532-39). In the US military services, there were 1329 reported cases of EAH between 1999 and 2011, giving an incidence of 12.6 per 100,000 person-years, among active duty members (O’Donnell et al “Army Medical Surveillance Activity Update:  exertional hyponatremia, active component, U.S. Armed Forces, 1999-2011” Medical Surveillance Monthly Report 2012; 19: 20-23).

What are the signs and symptoms of EAH?
In most cases there are no signs or symptoms of EAE. If there are symptoms of EAH these could be very diverse both in nature and in intensity. Common symptoms are for instance often fatigue/weakness, increased thirst, elevated temperature, tachycardia, orthostasis, nausea/vomiting, headache/dizziness, blurred vision, confusion/disorientation, obtundation, seizure, coma, respiratory distress, oliguria and diuresis.

Can EAH present with difficulties breathing?
Yes. In severe cases of EAH there might be fluid accumulation in the lungs, so called pulmonary edema. This is also called the Ayus-Arieff syndrome  (Ayus & Arieff “Pulmonary complications of hyponatremic encephalopathy. Noncardiogenic pulmonary edema and hypercapnic respiratory failure” Chest 1995; 107: 517-521).

Are you always having symptoms when you have EAH?
No, on the contrary there are no symptoms in most cases. See answers to questions above.

Are there other diseases affecting ultramarathon runners with similar symptoms?
Yes, for instance heat illness, dehydration or acute mountain sickness (AMS) often present with similar symptoms (Bennett et al 2013 “Wilderness Medical Society practice guidelines for treatment of exercise-associated hyponatremia” Wild Environ Med 2013; 24: 228-240).

How to diagnose EAH in the field and at the hospital?
Proper diagnosis of EAH requires measurement of blood sodium concentration. More and more races understand the importance of this and have point-of-care sodium measurement in the field available during the race. However, if no sodium measurement is possible in the field, as is often the case, a preliminary diagnosis of EAH can be made based on a history of overhydration and/or symptoms in severe cases and treatment initiated during transport to a medical center for proper diagnosis and further treatment. In all cases, hypotonic or isotonic fluid intake or administration should be restricted unless clear indications for fluid replacement, such as unstable blood pressure or severe acute kidney injury, are present until EAH has been ruled out with a sodium measurement as inappropriate hydration might worsen the hyponatremia with potential devastating consequences (Siegel et al “Exertional dysnatremia in collapsed marathon runners: a critical role for point-of-care testing to guide appropriate therapy” Am J Clin Pathol 2009; 132: 336-340). It should also be noted that a single venous post-race measurement of sodium might underestimate the severity of arterial hyponatremia and the patient needs to be observed and followed with repeated measurements in unclear cases, also as water remaining in the gastrointestinal tract might be quickly absorbed following cessation of exercise and result in rapid worsening of EAH (Halperin et al “Letter to the editor: Hyponatremia in marathon runners” N Engl J Med 2005; 353: 428; Ayus et al “Hyponatremia, cerebral edema and noncardiogenic pulmonary edema in marathon runners” Ann Intern Med 2000; 45: 14-19).

Can body weight change during exercise indicate EAH?
Yes, partly. Importantly, EAH can in some cases occur in individuals with weight loss so lack of weight gain can never rule out EAH. However, most individuals with EAH are gaining weight and EAH should therefore be suspected in ultramarathon runners who have gained weight during the race (Noakes et al “Three independent biological mechanisms cause exercise-associated hyponatremia: Evidence from 2,135 weighed competitive athletic performances” Proc Natl Acad Sci USA 2005; 102: 18550-55; Speedy et al “Hyponatremia in ultradistance triathletes” Med Sci Sports Exerc 1999; 31: 809-15). Many ultramarathon races and organized ultraendurance events are monitoring body weight and in the presence of weight gain fluid and sodium intake should be reduced until weight returns to 2% to 4% body weight loss from baseline level (Bennett et al 2013 “Wilderness Medical Society practice guidelines for treatment of exercise-associated hyponatremia” Wild Environ Med 2013; 24: 228-240)

Can EAH be prevented?
Yes, by avoiding overhydration. Athletes should focus on decreasing overdrinking during exercise by drinking according to thirst. Race organizers might consider reducing the overavailability of fluids (Bennett et al 2013 “Wilderness Medical Society practice guidelines for treatment of exercise-associated hyponatremia” Wild Environ Med 2013; 24: 228-240).

Is it possible to avoid EAH by taking salt tablets or drinking electrolyte solutions during a run?
No. Sodium supplementation during exercise has in several studies been shown to not prevent development of EAH in activities lasting less than 18 hours (Speedy et al “Oral salt supplementation during ultradistance exercise Clin J Sport Med. 2002; 12: 279-84; Hew-Butler et al “Sodium supplementation is not required to maintain serum sodium concentrations during an Ironman triathlon” Br J Sports Med 2006; 40: 255-59; Twerenbold et al “Effects of different sodium concentrations in replacement fluids during prolonged exercise in women Br J Sports Med 2003; 37: 300-03; Barr et al “Fluid replacement during prolonged exercise: effects of water, saline, or no fluid”
Med Sci Sports Exerc 1991; 23: 811- 17). It is a common misunderstanding that it is possible to avoid hyponatremia by ingestion of sodium, but it has in these studies convincingly been shown that it is the amount of fluid, and not sodium, ingested which is important for blood sodium concentrations during exercise.

How should EAH be treated?
Treatment of EAH should be handled by educated medical personnel. Firstly, treatment consists of avoiding further overhydration by avoiding isotonic or hypotonic fluid replacement (intravenous or oral) when the diagnosis of EAH is under consideration until urination commences. In cases of dehydration and rhabdomyolysis with impending acute kidney injury, a possible alternative diagnosis in some cases, hydration is on the contrary of importance and it is therefore important to rapidly measure sodium for a definite diagnosis. However, in the risk-balance between diagnosis with different treatments it needs to be noted that there is no documentation in the scientific literature linking exercise-related dehydration to life-threatening conditions, while EAH certainly can be lethal (Noakes “Hyponatremia in distance athletes: pulling the iv on the “dehydration myth” Phys Sportsmed 2000; 28: 71-76).  Secondly, if there is definite severe EAH or if there is suspicion of symptomatic EAH/EAHE with neurological deterioration even if no sodium measurement is available treatment with hypertonic saline should be considered. In milder cases oral hypertonic saline solution (for instance 3-4 bouillon cubes in 125 mL [½ cup] of water [~9% saline]) can be given. In more serious cases intravenous hypertonic saline should be considered (100 mL bolus of 3% hypertonic saline, which can be repeated twice at 10-minute intervals) (Bennett et al 2013 “Wilderness Medical Society practice guidelines for treatment of exercise-associated hyponatremia” Wild Environ Med 2013; 24: 228-240).

Treatment algorithm for EAH treament in the field. From Bennett et al 2013.

Can you die from EAH?
Yes. There are regretfully over 10 confirmed deaths due to EAH found in the scientific literature and most likely many more not published cases.