Tuesday, June 24, 2014

Medicine and Science in Ultra-Endurance Sports Conference Day 1

I started my first full day in Squaw Valley with a nice and easy 6 mile run in the AM.  Then I had the pleasure of attending a fascinating series of lectures in a conference titled, "Medicine and Science in Ultra-Endurance Sports".  This is the first time this event has been held and is sponsored by the Wilderness Medical Society.  I wanted to share the main bullet points from all the lectures which were all very good.

Cardiac Function in Ultra-marathoners- David Oxborough, PhD   Liverpool John Moores University
Dr. Oxborough went on to describe several acute and chronic effects on the heart in response to long distance running.  The chronic effects include eccentric hypertrophy of the Left ventricle (the main pumping chamber) and increase in the chamber dimension with normal function maintained.  This as opposed to a sick heart which will enlarge and  have decreased function.  The normal adaptive enlargement is to allow for more cardiac output during exercise.  He also observed in athletes that the Left atrium and right atrium (the top chambers) enlarged proportionally more than the left ventricle.  In the acute phase, in other words, right after the race, there appears to be significant Right ventricle enlargement and some decrease in function which improves after 1 day.  When bio markers of heart muscle injury were measured after an ultra, these were found to be slightly elevated.  This suggests microscopic heart muscle damage.  There also have been reported animal studies which show increase in fibrosis in the right ventricle and may predispose these individuals to arrhythmias.  (abnormal heart rhythms).  The most common appears to be atrial fibrillation which a few studies have shown has an increased incidence in long distance runners. He reported that all the studies do not seem to indicate an increased incidence of coronary artery disease (the cause of heart attacks) in long distance runners.  Take home point: Endurance training and competing has effects on the heart but these are not pathologic. Keep running.

Neuromuscular Fatigue: Lessons from Extreme Sport- Guillaume Millet, PhD  University of Calgary
Dr. Millet went on to differentiate the causing several elegant studies of maximum voluntary contraction before and after the ultra he showed that central fatigue is more of a factor than peripheral fatigue.  The cause of mental or central fatigue may be related to excess serotonin accumulation in the brain, or the so called "serotonin hypothesis".  There was no difference between men and women in these studies.  Take home point: fatigue is mostly in your head.

Effects of Ultra-Endurance Exercise and Carbohydrate Restriction on Membrane Fatty Acids, Inflammation, and Insulin Sensitivity- Stephen Phinney, MD, PhD  UC Davis
This lecture reinforced what has lately been the idea that a high carbohydrate diet may not be the best approach to training and participating in endurance events. As fuel, a typical 70-75 Kg athlete has 2,480 Kcal stored as muscle and liver glycogen, whereas that individual has 110,700 Kcal in the fat stores.  In order to become efficient at burning fat, a ketogenic diet (low carb, high in Fat and Protein) will dramatically enhance the capacity of fat oxidation.  This results in a reduced dependence on glycogen.  Of note, it takes weeks of adaptation when one goes on this diet before performance is restored.  The changes are at the mitochondrial level in the muscle and reduced insulin sensitivity. Take home point:  Consider altering from the conventional wisdom that carb loading is good and switch to a ketogenic diet. (paleo)

Gastrointestinal Distress in Ultramarathoners-  Kristin Stuempfle, PhD
A very common occurrence in running ultras, GI distress occurs in 37-60% of runners in 67-161 Km races.  In 161 Km races, it is the number one reason for dropping out. For one, as the cardiac output increases, there is decreased blood flow to gut and kidneys to shunt to the exercising muscles.  The causes appear to be various and include esophageal motility disruption and lower esophageal sphincter tone resulting in heart burn.  In the stomach, intense exercise causes delayed gastric emptying and this results in bloating, cramps, nausea, and vomiting. (lovely).  In the intestines, absorption of sugar and water is decreased and this can cause diarrhea.  Interestingly, they analysed what people ate and the effects of GI distress with the finding that consumption of more FAT seemed to cause fewer symptoms.   Take home point:  You are likely to have GI symptoms when you do an Ultra. Fluid and fat consumption may protect  you from it.

Sodium Supplementation, Drinking strategy and Weight change in a 100-mile Ultra- Marty Hoffman, MD  UC Davis

Marty mostly talked about taking salt tablets during the race and weight changes which are observed in the runners. He had a slide about the recommendations based on the weight, which are as follows:
  • Weight up, stop drinking until you pee off the excess.
  • Weight down, drink.
  • Mental status changes, drop and get medical help.

Take home point: Good idea to take salt tablets and drink water.

Barefoot/Minimalist Shoe Running and Foot Strike Pattern- Kevin Kirby, DPM, MS California School of Podiatric Medicine
Dr. Kirby began with a historical perspective on shoes and running shoe design. He showed how lightweight, thin-soled running shoes have been continuously available to runners for the past 40 years.  In the 70's they were called "racing flats" and were nearly identical to what today are called "minimalist shoes".  In an analysis of barefoot running, he showed that they increase stride frequency.  Also, contact time, stride duration, and flight times all decrease in barefoot running. .  Lastly, barefoot runners shorten stride length possible to avoid heel impact. He reminded us that "over-striding" has long been known to cause inefficient running form and reducing stride length often seems to lessen injury risk in runners. Lastly, he presented a study of 103 runners over 12 weeks which showed that running in minimalist footwear appears to increase likelihood of experiencing an injury. The speaker then spoke at length about heel striking vs. forefoot/midfoot striking, and found no significant difference in frequency of running injuries between the two.  However, there was evidence that CHANGING foot strike may cause injury. He also mentioned the Hokas, which he said were good and recommended changing shoes during the training week to reduce risk of injury.
Take home point: If heel striking, don't worry and don't try to change it.

Exercise-Associated Hyponatremia (EAH)- Tamara Hew-Butler, DPM, PhD  Oakland University.
An important topic for all marathon, Ironman triathletes and ultrarunners, hyponatremia can be life threatening. A low serum sodium can be caused by dilution in that you take in too much water combined with depletion of sodium via electrolyte losses in sweat or vomit. An important contributor to developing EAH  is the hormone ADH (anti diuretic hormone) also called AVP (arginine vasopressing).  Its function is to prevent water from being released in the urine, it concentrates the urine.  In an ultra or marathon, AVP levels are high during and post race which contribute to the dilution of sodium. Affected individuals can gain or lose weight and as such, body weight changes become less reliable indicators of fluid balance as race distance progresses.  When sodium is low symptoms can be vague at first but can progress to mental status changes.  The diagnosis is confirmed with a blood test and is treated with hypertonic saline.  Take home point:   Exercise-Associate hyponatremia (EAH) is bad, recognize the symptoms and treat urgently.

Rhabdomyolysis and Acute Kidney Injury - Robert H. Weiss, MD  UC Davis
Rhabdomyolysis is skeletal muscle damage that causes release of myoglobin and other muscle components into the blood stream and can in severe cases cause kidney failure to the point of needing dialysis.  It is characterized by severe muscle pain and inflammation.  In 2009, they reported on 5 cases of rhabdomyolisis and four had significant injuries that limited their training, so they came to the race under trained.  They pushed through despite being in severe pain. \Other predisposing factors include dehydration and hyperthermia.  Medications such a statins to treat cholesterol may increase risk but not proven, recommended to hold this medication before an endurance event. Take home point: If you are hurting a lot, you may need to quit.

Overall, an excellent day of lectures, if you are still reading this, I hope you get something out of it.  Tomorrow the lectures are less scientific and more practical.  I hope I still have the endurance to write it all again.


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