Ultra Wrap-Up: American College Of Sports Medicine Annual Meeting

ACSM logoEach year, the American College of Sports Medicine (ACSM) holds a meeting where physicians and scientists learn about the latest developments in the field of sports medicine. It is the largest, most comprehensive sports-medicine conference in the world. This year, I was presenting my group’s research on vision loss during ultramarathons and was grateful to have an excuse to attend.

This article is the first part of a two-part series. In addition to ACSM, I will be reporting from the Medicine & Science in Ultra-Endurance Sports conference that will take place in a couple weeks at the Western States 100.

Without further ado, here are selected dispatches from the 61st annual ACSM meeting held in Orlando, Florida from May 27 to 31, 2014.

Endurance Exercise and the Immune System

Over the last couple years, there has been increased interest in the immune system among the ultra community. Joe Uhan has written about the risk of infection in Overtraining Syndrome. But what if you don’t overtrain? What about ‘just’ running an ultra or a marathon once in a while? How does that change our immune system and risk of getting ill? More importantly, what can we do to stay healthy?

At this year’s ACSM meeting, Dr. Neil Walsh gave a lecture entitled “Environmental and Nutritional Extremes: Immune Function.” Dr. Walsh is from The University of Bangor in Wales and is the director of the Extremes Research Group. He co-authored the book Exercise Immunology. He had no conflicts of interest to disclose.

Neil Walsh's Extremes Research Group - ACSM 2014

Dr. Neil Walsh is pictured third from the left with the Extremes Research Group at Bangor University, Wales. Photo courtesy of Neil Walsh.

While doing research for this talk, I learned exercise immunology is far from a new field. Already in 1902 Dr. Ralph Larrabee found an increased white-blood-cell count (an immune-system reaction) in all six runners he studied following their completion of the Boston Marathon. More recent research at Western States indicated that 25% of runners develop symptoms of an upper-respiratory-tract infection (URI) such as a common cold in the two weeks after finishing the race (Nieman, 2003). The same study found that the lower our pre- and mid-race IgA levels (a marker of our external immunity, found in the mouth and gastrointestinal (GI) tract), the more likely we are to have these symptoms (Nieman, 2003). In other words, those who go into the race with a compromised immune system or whose immune system is affected early on are more likely to experience illness afterwards. The body produces less IgA during periods of chronic stress or intense training (Walsh, 2011a).

Dr. Walsh started his talk by introducing a study done by Peters and Bateman at the Comrades Marathon in 1983. They reported that the longer the race, the more likely runners are to report symptoms of infection in the two weeks following. 70% of those who ran the 90k race reported URI symptoms. In contrast, only 30% of the runners in the 56k race and 10% of controls reported symptoms. Essentially, the harder/longer the race, the more likely we are to have symptoms of infection. That those running the longer (90k) race were more likely to experience symptoms suggests it is not travel and/or lack of sleep alone that produces symptoms; if that were the case, there would have been approximately the same incidence of symptoms in both groups.

But (and this is a strange concept), just because you report symptoms of an infection does not mean you are actually infected. In fact, in one study, only 1/3 of athletes who experience infection symptoms following a race tested positive for a virus or bacteria out of a very extensive testing battery (Spence, 2005). The cause of remaining 2/3 of the symptoms is not well defined, but seem to come from various sources, including allergies and our body’s reaction to racing. (For example, IL-6, which can cause fever, is released from our muscles after periods of hard exercise (Pedersen, 2008).)

Dr. Walsh reviewed the reasons endurance athletes may have an increased risk of infection:

  1. Racing. As mentioned above, intense exercise decreases our immune response (Walsh, 2011a), but he mentioned that moderate training, even at the elite level, seems to decrease the risk of infection compared to sedentary controls (Malm, 2006).
  2. Heat. Exercising in high temperatures (Shephard, 1998). (Whereas passive heating–such as saunas–actually decreases our risk of infections (Ernst, 1990).)
  3. Cold Either cold body temperature or just a cold nose (Eccles 2002; Johnson, 2005).
  4. Altitude. Ascending to 3,800 meters causes a lowered immune response (Oliver, 2013).
  5. Malnutrition. If you are low on calories, your lymphocyte count (part of your immune system) is lowered (Diment, 2012).
  6. Poor sleep (Walsh, 2011b).
Excercise Immunology - ACSM 2014

For futher reading, you can check out ‘Exercise Immunology’ (2013) by Gleeson, Bishop, and Walsh.

So, what can we do about it?

  1. Eat or drink carbohydrates while racing. This appears to help restore our immune system. (Dr. Walsh mentioned IgA levels specifically.)
  2. Wash your hands.
  3. Wear masks in cold air. (Think hotels or airports with extreme air conditioning systems.)
  4. Avoid touching your eyes, nose, and mouth.
  5. Consider taking probiotics. (They lower the rate of upper-respiratory and GI infections.)
  6. Sleep more! (See Caldwell and Dunican’s iRunFar article on the importance of sleep in performance.)

Are there substances we can take to boost our immune system pre-race?

Perhaps:

  • Probiotics
  • Vitamin D (specifically from the sun)

But not necessarily these:

  • Vitamin C. Supplementation may blunt healthy effects of exercise (Ristow, 2009); evidence that it is an effective immunostimulant pre-race is thin.
  • Vitamin D. Pill supplementation may blunt responses to training.
  • Zinc in high-enough doses can lower immune response.

There is no good evidence for:

  • Echinacea
  • Quercetin
  • Colostrum (antibody-rich cow’s first milk)

Dr. Walsh pointed out that the immune system is constantly trying to strike a balance. When it overreacts, you get inflammation, atherosclerosis, and auto-immune diseases. There is good evidence that exercise lowers inflammation and symptoms of autoimmune diseases. However when the immune system underreacts, for example due to a hard exercise effort, we have tipped the balance and increased our risk of infection.

Altitude Training

For a physician who has dedicated his career to studying altitude training, it was refreshing to hear Dr. Benjamin Levine essentially conclude that high-altitude training only rarely improves athletic performance and only under very specific circumstances.

Benjamin Levine - ACSM 2014

Benjamin Levine. Photo courtesy of Benjamin Levine.

Dr. Levine is a distinguished professor of Exercise Sciences at the University of Texas Southwestern. He received his Doctor of Medicine from Harvard Medical School and did his residency in Internal Medicine at Stanford University. He is the cardiac-unit director for NASA and has been honored by the U.S. Olympic Committee for his contributions to the understanding of altitude training. He had no conflicts of interest to disclose.

There was a great deal of interest in altitude training following the 1968 Summer Olympics in Mexico City (elevation 2,400 meters). Exercise scientists were surprised to see altitude-adapted athletes beating athletes who normally would have won at sea level.

While studying this phenomenon during the 1970s, scientists discovered, on average, athletes’ VO2 max would increase after training a week or more at altitude and returning to sea level.

Dr. Levine went through over 30 years of research, which included much of his own work. He has, for example, been credited with proposing the concept of “live high, train low.”

Here is what we currently understand about altitude’s effect on human endurance performance:

  • Altitude increases VO2max by increasing our red-blood-cell mass, stimulated by excess erythropoietin (EPO) production (Wherlin, 2006).
  • Altitude training, if done correctly, will only help in sports that are dependent on VO2max (think 5,000 meters in running) and makes no difference in sports like swimming.
  • In order for altitude to have an effect on your VO2max and performance, you need to be at altitude for at least 12 hours a day (Wilber, 2007a).
  • From a practical standpoint, altitude tents may not work. A randomized, double-blinded, controlled trial where athletes spent 16 hours a day in an altitude (nitrogen) tent resulted in no difference in performance or blood tests compared with controls (Siebenmann, 2012), possibly because lying around in a tent for so many hours (16) a day prevented the expected physiological changes.
  • The most important element of altitude training is the training. If you can’t train your intervals well, there is no point in altitude exposure (Levine, 1992).
  • Athletes new to altitude appear to not run intervals as effectively and do not experience significant improvement. This is where the “live high, train low” philosophy comes from and is extensively backed by research, including that of Dr. Levine (Levine, 1992).
  • Because traveling to a lower altitude multiple times a week for harder workouts is expensive and impractical, the current format adopted by elite American coaches and athletes is to live and train at altitude, but perform the hardest workouts with supplemental oxygen. [Author’s Note: I have seen discussion of this training inducing more injuries and requiring longer recovery time (Pfitzinger, 2000).]
  • Non-responders. Not everyone responds to altitude exposure. The most notable example is people with iron-deficiency anemia (Levine, 1992). [Author’s Note: Rasmus Høeg, my haematologist husband explains, “Your EPO production is already high when you have iron-deficiency anemia; you can’t make it go higher with altitude.”] There is an additional subset of people (up to 50%) who are non-responders to altitude (de Paula, 2012) and it is currently unknown exactly why, though Dr. Levine noted that beyond anemia, there is evidence for a genetic component to some of these cases.

Dr. Levine suggested at the end of his talk that perhaps the reason there is so much interest in the field of high-altitude medicine and science is that even researchers love spending time in the mountains. :)

[Author’s note: Dr. Levine did not cover how much living at altitude helps for races at altitude or how long it takes to adapt. Because I know there is interest in this subject among iRunFar readers, I have included an evidence-based table (Chapman, 2013) below to help with your upcoming races at altitude:

Altitude chart - ACSM 2014IHE refers to exposure through an altitude (nitrogen) tent and a review of over 40 studies on this subject found no clear advantages of the tent beyond decreased shortness of breath (Wilber, 2007b).]

The Endurance Athlete’s Heart

Aaron Baggish - ACSM 2014

Aaron Baggish. Photo courtesy of Aaron Baggish.

Dr. Aaron Baggish gave, in my mind, the most outstanding talk of the conference when he went through the history of research of the effect of endurance exercise on the heart. Dr. Baggish will probably forever best be known as the medical director of the tragic Boston Marathon in 2013. He is also the director of the Cardiovascular Performance Program at Massachusettes General Hospital and he’s a runner.

And that is probably his only bias, that he loves to run. But he was very open about that and reported no other conflicts of interest.

Dr. Baggish presented over 10 epidemiological studies that indicated the more you exercise, the less likely you are to die sooner or develop life-threatening diseases. In some of these, the more you exercised during the week, the better. In some, a moderate amount was the best, but even sedentary was never better than “extreme.”

Dr. Baggish made the good point that everyone expects exercise to be like any other medication–the “right amount” is good, but too much is toxic. But this model has not panned out for exercise. And in fact, the current “normal,” which is being sedentary, appears to be the least healthy and perhaps “toxic,” if you will, in terms of what the body can handle.

Below is just one sample (Wen, 2011) from the studies Dr. Baggish cited. Their data (Wen, 2011) suggest the more you exercise, the less likely you are to die sooner, develop cancer, cardiovascular disease, or diabetes.

Wen figure 1 - ACSM 2014

Risk of mortality by disease based on amount of reported physical activity (Wen, 2011).

Wen figure 2 - ACSM 2014

The percent the risk of mortality is reduced by number of minutes of physical activity per day (Wen, 2011).

Given the overwhelming evidence that exercise is healthy, what has caused the recent concern in the press?

  1. The Missouri Study found 50 long-term male marathon runners had a higher amount of coronary-artery plaque than their age-matched controls (Schwartz, 2014). Baggish says this should be interpreted with caution because it was not a well-controlled study. He says that runners tend to have had heart disease in the family, a previous history of smoking, a history of hypertension, poor diet (all things they are “running away from”), and this study did not control for those factors.
  2. Anecdotal evidence. When Micah True, known as Caballo Blanco in Chris McDougall’s Born to Run, died, many were quick to point to his excess running as the cause. However, Dr. Baggish showed a copy of Micah True’s autopsy, which showed an enlarged heart, which he suggested was expected for a long-distance runner like True and that there was no sign of disease. [Author’s Note: The autopsy can be viewed publicly. (Be warned, this is a full, public autopsy that contains graphic information.) Dr. Baggish disagreed with the autopsy’s conclusion of “cardiomyopathy.” Upon reviewing the autopsy, I am not certain what the significance of the small areas of “inflammatory infiltrate” is in the heart and lungs.]
  3. Following marathons, multiple studies have measured the heart’s distress through lab tests called cardiac enzymes, which are found to be elevated during a heart attack. Invariably, runners emit these enzymes after marathons and longer races, which concerned many physicians and scientists. However, in the context of running, this has not been associated with death or disease and the significance of these enzymes in athletes is not currently understood (Siegel, 1997).
  4. Enlarged hearts. Even in 1899 and probably earlier, there was evidence that athletes’ hearts were different. Both in America and Europe there were reports of very large hearts in athletes. Baggish described that the heart remodels with repeated endurance exercise so that it becomes larger (eccentric hypertrophy, to be exact) and better at relaxing. In essence, the endurance athlete’s heart becomes more effective. However, there is a small part of the heart (between the right and left ventricles) that gets stiffer and seems to build up scar tissue over years of exercise. [Author’s note: This has also been seen in ultramarathon runners (George, 2011).] The exact significance of this is not known, but it may lead to number 5.
  5. Irregular heartbeats. This is, indeed, the one concern that has been shown to be true in multiple studies–that atrial fibrillation and atrial flutter, related types of irregular heart rhythms, are more common in older (middle-aged and older) male athletes (Claessen, 2011; Myrstad, 2013). This is not that feeling you get infrequently, that your heart is skipping a beat, your chest gets tight, and you feel panicky. Those are premature ventricular contractions and are normal. Atrial fibrillation sometimes goes unnoticed in older populations, but would generally be experienced as an inability to exercise (fatigue and shortness of breath). The increased risk of atrial irregular rhythms was not found in younger athletes (Pelliccia, 2005). The most likely explanation for this seems to be the larger size of the right atrium, possibly reacting to that “stiffer” area of heart muscle described above.

[Author’s Notes: 1. I could not find any studies demonstrating an increased risk of atrial fibrillation in older female endurance athletes. 2. Atrial flutter and fibrillation can be diagnosed with an electrocardiogram (EKG).]

Dr. Baggish gave the following advice for endurance athletes:

  1. It is not appropriate to be unhealthy in your other habits (diet, sleep, smoking, excess alcohol, etceteras) just because you run.
  2. Plan annual periods of recovery (less exercise, “off season”).
  3. Warm ups and cool downs. Though sudden cardiac death is excessively rare, a proper warm up will help reduce your risk.
  4. Careful event preparation. Know what kind of race you are getting into and train appropriately.
  5. Respect a virus. (Drop your hard workouts if you are sick.)
  6. Listen to warning signs. [Author’s Note: In my clinical experience, athletes are generally the best population at noticing something is “off.” If you are worried, get it checked out! If the doctor ignores your complaint, get a second opinion.]

[Author’s Note: None of the studies Baggish referred to was a randomized-controlled trial, so it is impossible to determine cause and effect. It is, however, very important that people not be discouraged from starting an exercise program due to theoretical concerns at the extreme end of the exercise spectrum. Finally, with growing interest in ultramarathon medicine, it will be interesting to follow the work of Dr. David Oxborough (who will be speaking at the Western States conference) and others who do cardiac studies specific to ultra-endurance athletes. Currently the amount of exercise that is considered “extreme” has not been well-defined and it’s therefore difficult to know exactly which studies and findings apply to ultramarathon runners.]

Call for Comments (from Meghan)

  • What are your thoughts on any or all of these dispatches? On endurance exercise and the immune system, altitude training, and the endurance athlete’s heart?
  • Have you experienced symptoms of an upper-respiratory-tract infection after a long ultra?
  • How does your body react to altitude?
  • What are your thoughts on Dr. Baggish’s discussion of endurance athletes’ heart health?

Acknowledgements

I would like to thank Meghan Hicks, Rasmus Høeg, and Joan and Don Prachthauser for their editorial help with this article.

References

  1. Baggish AL, Yared K, Wang F, Weiner RB, Hutter AM, Wood MJ. The impact of endurance exercise training on the left ventricular systolic mechanics. Am J Physiol Heart Circ Physiol (2008) 295:1109-16.
  2. Claessen G, et al. Long Term endurance sport is a risk factor for development of lone atrial flutter. Heart (2011) 97(11):918-22.
  3. Chapman RF, Laymon AS, Levine BD. Timing of arrival and pre-acclimitization strategies for the endurance athlete competing at moderate to high altitudes. High Alt Med Biol. (2013) 14(4):319-24.
  4. De Paula P, Niebauer J. Effects of high altitude training on exercise capacity: facto r myth. Sleep Breath (2012) 16(1) 233-9.
  5. Diment BC, et al. Effect of daily mixed nutrional supplementation on immune indices in soldiers undertaking an 8-week arduous training programme. Eur J Appl Physiolol. (2012) 112(4):1411-8.
  6. Eccles R. Accute cooling of the body surface and the common cold. Rhinology (2002) Sep;40(3):109-14. Review.
  7. Ernst E, Pecho E, Wirz P, Saradeth T. Regular sauna bathing and the incidence of common colds. Ann Med. 1990;22(4):225-7.
  8. George KP, Warburton DE, Oxborough D, Scott JM, Esch BTA, Williams K, Charlesworth S, Foulds H, Oxborough A, Hoffman MD, Shave R. Upper Limits of Physiological Cardiac Adaptation in Ultramarathon Runners. JACC (2011) 57(6) 754-5
  9. Johnson C, Eccles R. Acute cooling of the feet and onset of common cold symptoms. Fam Pract. 2005 Dec;22(6):608-13. Epub 2005 Nov 14.
  10. Larrabee RC. Leucocytosis after violent exercise. J. Med. Res (1902) 7:76-82.
  11. Levine BD, Stray-Gundersen J. A practical approach to altitude training: where to live and train for optimal performance enhancement. Int J Sports Med (1992) 13 Suppl:1 S209-S212.
  12. Malm C. Susceptibility to infections in elite athletes: the S-curve. Scand J Med Sci Sports. 2006 Feb; 26(1):4-6.
  13. Myrstad M, Løchen ML, Graff-Iversen S, Gulsvik AK, Thelle DS, Stigum H, Ranhoff AH. Increased risk of atrail fibrillation among elderly Norwegian men with a history of long-term endurance sport practice. Scand J Med Sci Sports (2013). [Epub Ahead of Print]
  14. Nieman DC, Dumke CI, Henson DA, McAnulty SR, McAnulty LS, Lind RH, Morrow JD. Immune and oxidative changes during and following the Western States Endurance Run. Int J Sports Med (2003) 42 (7):541-7.
  15. Oliver SJ et al. High Altitude impairs In Vivo Immunity in Humans. High Altitude Medicine & Biology (2013) 14(2):144-9.
  16. Pedersen BK, Febbraio MA. Muscle as an endocrine organ: focus on muscle-derived interleukin-6. Physiol. Rev. (2008) 88(4):1379-406.
  17. Pelliccia A, Maron BJ, Di Paolo FM, Biffi A, Quattrini FM, Pisicchio C, et al. Prevalence and clinical significance of left atrial remodeling in competitive athletes. J Am Coll Cardiol (2005) 46:690-6.
  18. Peters EM, Bateman ED. Ultramarathon running and upper respiratory infections. An epidemiological survey. S Afr Med J. 1983 1; 64(15):582-4.
  19. Pfitzinger P. Highlights of the Third Annual International Atitude Training Symposium. (2000) http://www.sportsci.org/jour/0001/pf.html. Accessed June 3rd, 2014.
  20. Ristow M et al. Antioxidants prevent health-promoting effects of physical exercise in humans. Proc Natl Acad Scie U S A. (2009) 106(21):8665-70.
  21. Shephard RJ. Immune changes induced by exercise in an adverse environment. Can J Physiol Pharmacol. 1998 76(5):539-46.
  22. Siebenmann C et al. “Live high-train low” using normobaric hypoxia: a double-blinded, placebo-controlled study. J Appl Phyiol (2012) 112(1):106-17.
  23. Schwartz et al. Increased Coronary Artery Plaque Volume among Male Marathon Runners. Missouri Medicine (2014) 111(2):85-97.
  24. Seigel AJ, Sholar M, Yang J, Dhanak E, Lewandrowski KB. Elevated serum cardiac markers in asymptomatic marathon runners after competition: is the myocardium stunned? Cardiology (1997) 88(6):487-91.
  25. Spence L, Nissen MD, Sloots TP, McCormack JG, Locke AS, Pyne DB, Fricker PA, Brown WJ.Upper respiratory illness aetiology and symptomatology in elite and recreationally-competitive athletes.Brain Behav Immun 19: 469–470, 2005.
  26. Walsh (a) NP et al. Position statement. Part one: Immune function and exercise. Exerc Immunol Rev. 2011; 17:6-63. Review.
  27. Walsh (b) NP et al. Position statement. Part two: Maintaining immune health. Exerc Immunol Rev 2011; 17:64-103.
  28. Wen CP et al. Minimum amount of physical activity for reduced mortality and extended life expectancy: a prospective cohort study. The Lancet (2011) 379(9798):1244-53.
  29. Wehrlin JP, Zuest P, Hallén J, Marti B. Live high-train low for 24 days increases hemoglobin mass and red cell volume in elite endurance athletes. J Appl Physiol (2006): 1938-45.
  30. Wilber (a) RL, Stray-Gundersen J, Levine BD. Effect of hypoxic “dose” on physiological responses and sea-level performance. Med Sci Sports Exerc (2007) 39: 1590-99.
  31. Wilber (b) RL. Application of altitude/hypoxic training by elite athletes. Med Sci Sports Exerc (2007) 39:1610-24.
Tracy Beth Høeg MD, PhD

practices at UC Davis. She has training in physical medicine and rehabilitation as well as ophthalmology. She is a Danish-American double citizen who ran for the United States on an international level in trail ultramarathon. She is married to Dr. Rasmus Høeg and they have two sons.

There are 20 comments

  1. @dyldahl

    Regarding the Immune Sections:

    "Vitamin D. Pill supplementation may blunt responses to training."

    Extremely curious why the claim behind this? Is this your claim [author] or is this Dr. Walsh's? For example, Vitamin D supplementation has actually been linked to improving recovery (1, 2), not hindering it…Curious if you meant to put Vitamin "C" (or more so antioxidants) not "D" here, due to antioxidants attenuating mitochondrial biogensis (3).

    References:

    (1) http://www.ncbi.nlm.nih.gov/pubmed/23595134

    (2) http://www.nutritionandmetabolism.com/content/10/

    (3) http://www.ncbi.nlm.nih.gov/pubmed/21085043

    1. @TracyBethHoeg

      Great question! This was something Dr. Walsh said, but I debated including it since he did not provide a reference and I could not find one. Dr. Walsh also mentioned that zinc can blunt responses to training and because Vitamin D increases the absorption of zinc, perhaps it is an indirect effect – I am not sure, but admit I can not find a specific study that has found this (so thank you for providing insight!). You are correct that Vitamin C and E have recently been identified as potentially blunting responses to training.

      The studies you included about increasing muscle recovery are interesting. It seemed that Dr. Walsh looked at regular vitamin supplementation a lot like I do as a clinician, which is that, especially fat soluble vitamins (like vitamin D) can build up and become toxic or simply cause side effects. Vitamin D toxicity is rare, but having too much can cause side effects like weakness and fatigue.

      He mentioned that low vitamin D levels are associated with an increased risk of infection, but shied away from recommending supplementation (and recommended sun exposure). This may partly be due to the fact that supplementation to prevent infection has not been proven and (this is my own addition) a low vitamin D level may most often be a RESULT of poor health rather than a cause (Autier P, Boniol M, Pizot C, Mullie P (December 2013). "Vitamin D status and ill health: a systematic review". The Lancet Diabetes & Endocrinology).

      Not sure if that answers the fundamental question here, but hopefully provides some insight for people considering vitamin D supplementation. Perhaps someone reading this will be aware of the study Dr. Walsh was referring to.

      1. @dyldahl

        First off, thanks for the response!

        Getting to the zinc absorption and VITD increasing this absorption, sounds like another claim by Dr. Walsh, without a reference? Any idea for a source on that one?

        Secondly, regarding your work as a clinician (which congrats at being a MD, I envy peoples work ethic and drive to face med school – currently pursuing a MSc and hopefully a PhD) and how fat soluble vitamins can build up causing ill effects, are these ill effects related to mega dosages seen in rat models? I do know that obeses individuals (typically the general population and individuals you deal with in clinics) that they require less Vitamin D then a lean individual (due to as you mentioned, VIT D is a fat soluble vitamin thus stored in fat).

        Thirdly, regarding the "fatigue and weakness", link to study?

        Sun exposure would be awesome, but if you are living in the northern latitude (I think it is something like 30-degrees, don't quote me on that) it is almost impossible to receive the needed sun exposure for optimal ranges (minus the summers), thus supplementation is needed.

        Here is a recent gem from Dr. Rhonda Patrick on Vit D supplementation and Autism:
        http://www.ncbi.nlm.nih.gov/pubmed/?term=rhonda+p

        1. @TracyBethHoeg

          Regarding vitamin D and zinc, my understanding is secosteroids like vitamin D help with the absorption of divalent cations like zinc. Here is a review of zinc homeostasis, which explains it much better than I could: http://www.oucom.ohiou.edu/dbms-li/Publication%20….

          You ask a good question about fat soluble vitamins. Hypervitaminosis (effect of excess supplementatino) can occur in lean as well as obese individuals (I'm not sure about the difference in risk). Here is more info: http://en.wikipedia.org/wiki/Hypervitaminosis and you can click on Vitamin D to see the specifics. I do clinical PhD research right now and work with a pretty lean population but fat soluble vitamin supplementation toxicity comes up often. Again, it is very rare with vitamin D. The fatigue and weakness with excess vitamin D comes from excess calcium that builds up concomittantly. (haha, never thought I'd go into such detail with this topic).

          I have to add that in areas of low sunlight exposure that, at least in children, vitamin D supplementation is recommended. I live in Denmark and all infants receive supplementation here because it is such a high latitude, so good point with the lack of sunlight! Inadequate vitamin D in children at high latitudes can cause rickets (not to mention the low calcium which can be deadly). The adult equivalent, osteomalacia, occurs at less than about 10 ng/mL of Vitamin D and certainly such a low level would require supplementation.

          It has just been difficult to show benefits of regular vitamin D supplementation with levels that are slightly low – and going too high can cause adverse effects. It's a tricky topic and I certainly don't have all the answers! I know people have strong opinions about vitamin D and I hate to discourage people from doing something that really works for them, whatever their health situation is.

          1. @dyldahl

            Thanks for the link on the zinc, I will certainly have to read that later.

            Regarding you clinical PhD work and supplementation toxicity – I'm curious, what type of population are you working with and what is the dosage of these vitamins? Seems as though you may be dealing with an "unhealthy" population (no matter their leanness), thus some other underlining cause could be the disordered vitamin absorption/malabsorption.

            Regarding going to low or to high, in my opinion people are better off supplementing rather then not. It is very difficult to overdose on Vitamin D (or any vitamin for that matter) – simply from the fact that the general populations diet is not adequate enough to get in the proper amounts of vitamins through natural foods. Even if there diet is on par, the nutrient/micronutrient/phytonutrients in food today, compared to what they were in the past, is still significantly inferior – thus making supplements not typically that harmful.

            1. @TracyBethHoeg

              I have to say I don't regularly see vitamin toxicities. I work with eye diseases so the patients I see don't tend to be more "sick" but on average older. Vitamin E supplementation for example may increase mortality. Vitamin A may increase the risk of lung cancer in smokers. High dose multivitamins are used to treat AMD, so we need to mention the risks to people. Vitamin D is not one that is considered high risk, but that does not mean there are no potential risks or side effects. I am not enough of an expert on the topic to advise generally at what level people should take vitamin D supplements. It really depends on the situation and the problem/disease.

  2. GMack

    Great article. I appreciate it when research and conclusions are drawn from those actually out in the field who understand sports and athletes (disclaimer: Dr. Levine is my cardiologist).

  3. npedatella

    Thanks for the thorough summary. Is it a correct interpretation of the research that sleeping in an altitude tent is not beneficial? Typical sleep times would seem to fall significantly below the 12 h threshold for gaining a benefit. Given what seems to be an increase in popularity of altitude tents this is an interesting result.

    1. @dyldahl

      If one actually looks at the data, normobaric hypoxia (what happens when you reduce the Oxygen content, but the pressure remains the same – which is what altitude tents do) impose no real significant benefits morphologically/biologically compared to hypobaric hypoxia (what happens when you reduce both Oxygen and Pressure – what happens when you go to altitude), and it is basically training your diaphragm muscles rather then any blood related benefits.

      1. @TracyBethHoeg

        In the one randomized, controlled trial of altitude tents there was no benefit seen (Siebenmann) – this was not a study about peformance at altitude, though (that was not covered by Dr. Levine). It seems one has to spend such a long time in them per day that they don't work from a practical standpoint. At least that has what research has suggested so far. Living high and training low does seem to have a positive effect on performance at sea leve, though (Dr. Levine was part of the first study to show this).

    2. @dylanbo

      Unfortunately, this article only touches on one side of the altitude conversation. There is plenty of other scientific literature and extensive anecdotal evidence to suggest the exact opposite of what Dr. Levine is asserting.

      Also, when it comes to normobaric hypoxia's application for Ultrarunning, it's not all about the tent. Performing exercise in intermittent hypoxia is also hugely helpful from a performance and acclimatization perspective. Again, there are lots of studies on the subject but I'll point to one here that is easy to digest http://www.ncbi.nlm.nih.gov/pubmed/11374111.

      Anecdotally, Hypoxico works with some of the top mountain guiding outfits to provide pre-acclimatization for their clients in order to do accelerated attempts on the highest mountains in the world. Cutting itineraries so significantly would not be safe or likely even possible without the use of normobaric hypoxic equipment. The same principle of pre-acclimatization applies for Ultrarunning.

      1. @dyldahl

        @dylanbo,

        Curious, you linked a "hypobaric hypoxia" study, not a "normobaric hypoxia" study. Do you have one that links the benefits towards normobaric hypoxia (e.g., altitude tents).

        I'm not saying intermittent hypoxic training isn't beneficial, but as I stated above, the hypoxic environment that tents such as those produced by Hypoxico do not stimulate the hematological benefits seen in actual acclimatization to real altitude (hypobaric hypoxia). There is a major difference when it comes to "acute" and "chronic" exposure to these environments as well —> link to reference: http://www.ncbi.nlm.nih.gov/pubmed/22779311

  4. Joe

    With regard to your research on vision loss during ultramarathons, will you be discussing that in part 2? I am interested in that topic.

    1. @TracyBethHoeg

      Joe- thanks for your interest! I wish I were, but that is not planned. I am a "back-up speaker" at the WS conference, so unless I speak, it probably won't get covered here, though it has been submitted for publication so hopefully the results will be out soon. If you can give me your email address I can send you the ACSM poster.

  5. @PhilJeremy

    Not sure what your conclusions were on Atrial Fibrillation and scaring in older athletes. I have a Mitral valve prolapse and have been strongly advised to quit ultra's (I'm 60). I'm sure you are aware of the Mayo clinic studies on this. You admit these issues do exist but what are your recommendations?

    1. @TracyBethHoeg

      Phil, sorry to hear about your mitral valve prolapse. I am not familiar with the Mayo Clinic studies on this. Is it associated with exercise. Is there any chance you could include a reference? I just looked it up and couldn't find anything. In terms of exercise, I would advise you follow your docs recommendations – I imagine you see a cardiologist who will be able to give better recommendations that I can. In terms of general recommendations for endurance athletes, I am looking forward to hearing Dr. Davis Oxborough's talk at the WSER conference in two weeks. Otherwise, the most recent published update on the effect of endurance exercise on the heart has not said anything about avoiding specific types of exercises. It is an emerging field, which many of us would like to know more about. Here is a link to the update: http://www.ncbi.nlm.nih.gov/pubmed/23097476 I can send a pdf if you can't access it. You can find me on twitter or Facebook and I can send it.

  6. JosephJameson

    I'm a 55 year old ultrarunner and have been doing long distance endurance sports biking, tri, and Nordic skiing for many years. I recently had a 12 hour bout of a fib and had to be cardioverted (shocked) in the ER. I have no family hx of heart disease, or any risk factors. While this is not common there is definitely an association between long distance endurance athletes and afib as we get into middle and later ages. Just google "endurance athletes and a fib" and you'll find all sorts of information._For me I am still running but no one seems to know the future for guys like me. I have cut back some and try to take two days off a week and get plenty or rest. Alcohol may play a role also in some individuals.

    1. CharlieDalziell

      Rik Myall – regular runner, 56, died of a heart attack. No family history and no risk factors. Scared me.

  7. sharmanian

    Thanks so much for this well-researched and thought out article. Very helpful and informative, plus good to counter the journalistic style of scare stories about heart problems in the press.

  8. CharlieDalziell

    I would like to see a study of ultra marathoners post-race dietary intake and the effect on the immune system. 1 large pizza and a dozen beers post race may place more undue stress on the body's immune system than the actual race.

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