Archive for May, 2012

Micah True and cardiac risks: what might mountaineers tell us about balancing risks and safety?

May 30, 2012

Ed Reyna, an 81 year old distance runner from California, recently sent me a very interesting article from the New York Times about Micah True, the American runner who had been inspired by the Tarahumara people of the Copper Canyon region in Mexico.  He had turned away from the soul-destroying pressure of contemporary Western society and become a champion of the traditional simple life-style of the Tarahumara, and their legendary long distance running.

Micah True had in turn become an inspiration for thousands when Chris McDougall gave him a central role in Born to Run.  I have not yet made time to read Born to Run, mainly because I have not found the time to read any book for many years, but also in part, it is because I am naturally sceptical about gurus.  On the basis of the way he presents himself in the video interviews I have seen, I am sceptical of McDougall’s writings.  I am sure he believes his message about the virtue of minimalist running, but True’s own account suggests that McDougal dramatised the story of the Tarahumara (or Raramuri – ‘the light footed ones’, as they call themselves) and of Micah True (or Caballo Blanco, as he was happy to call himself), for the sake of producing a popular book   However, whatever one might make of the authenticity of Chris McDougall’s writing, or indeed of True’s own somewhat idiosyncratic character, I think there is little doubt about the authenticity of True’s sincere belief in the spiritual richness of running, and the shallowness of modern materialism.

The NY Times article described the search for True’s body after he went missing while running in the Gila wilderness of New Mexico in March.  In a manner that I suspect True might have appreciated, his body was found by three friends who became frustrated by the orthodox procedures of the official search, and headed off late in the afternoon along the course of a stream that ran though a rugged and remote canyon, on the basis of a hunch that True would have been likely to have chosen such a route.   They found him lying with his feet in the stream and several superficial scratches and bruises suggesting that he might have suffered an injury and then died of exposure to the night-time chill.  However, the autopsy concluded that he died as a result of cardiomyopathy.

The autopsy

The autopsy report by the Chief Medical Investigator from University of New Mexico Health Sciences Centre describes the superficial scratches and bruises, but there was no evidence of substantial external trauma.  I was intrigued also to read of the congenital deformation of True’s toes.  The second and third toe had a flexion deformity and the third lay over the fourth.  I know that deformity well because I have it myself.  I was intrigued because of the light it throws on my favourite anecdote about True.    Apparently one day when he was running along a dusty road in an old pair of trainers he came face to face with a van load of paparazzi.  Noting the contrast between the imagined huarache-shod high priest of minimalist running evoked by Chris McDougall, and the real-life True shod in tatty trainers, the response of the paparazzi was “Look, he’s wearing shoes. What a phoney”.    Although I understand that that he did often run in sandals, in my imagination, tatty old trainers suit True perfectly.  He used to joke that women would faint if they saw his ugly feet.  More pragmatically, I think it is very likely that the flexion deformity of his toes was associated with downward protruding metatarsal heads, and he almost certainly found it more comfortable to have a moderate amount of padding beneath them.

However, the serious part of the autopsy was the description of the heart.  It was described as large and globular.  The wall of the left ventricle was 15 mm thick at a point halfway from apex to base.  Apart from some mild atherosclerosis partially obstructing several blood vessels, there was no other evidence of disease that might have accounted for an enlarged heart.  Not surprisingly, the Chief Medical Investigator concluded death was due to idiopathic  cardiomyopathy– meaning pathology of the heart muscle arising from no  obvious cause.  In particular, there was no appreciable fibrosis of the heart muscle, as would be expected if True had suffered from ischaemic heart disease in the past.

Was the cardiomyopathy idiopathic?

However, the term idiopathic might not be strictly accurate.  There is a very obvious reason why True should have had a large heart with thick ventricular walls.   A runner’s heart experiences both volume loading and pressure loading.  The 4 to 6 fold increase in cardiac output during running relative to rest ensures that a large volume of blood is returned to the heart at the end of each contraction.  The large volume of blood stretches the heart muscle, creating an eccentric load which causes it to contract more forcefully, and leading to the adaptive formation of new sacromeres (contractile elements) in series with the existing sarcomeres.  Thus the diameter of the heart grows larger.  In addition, the more forceful contraction creates a larger pulse pressure so the heart muscle contracts against a heavier resistance.  This subsequent concentric loading causes adaptive hypertrophy in which fibres are added in parallel with the existing sarcomeres.  This thickens the wall of the ventricles.    The overall result is a large heart with think ventricular walls, that pumps more powerfully and more efficiently.   But this raises two questions concerning True’s heart

Might the degree of cardiac hypertrophy recorded at the autopsy be accounted for by True’s extensive running?  The Medical Investigator reported that the thickness of the ventricular walls was 15 mm.  The average value in the male population is approximately 10mm.  It is conventionally regarded that 13 mm is the limit that distinguishes the normal range from cardiomyopathy.    Perhaps the most definitive study of ventricular wall thickness in athletes is the study of 947 elite athletes from various sports, published by Pelliccia and colleagues in the New England Journal of Medicine in 1991.    While the majority of the athletes had a wall thickness less than 13 mm, wall thicknesses greater than or equal to 13 mm were identified in 16 of the 947 athletes (1.7 percent), and the thickest was 16 mm.    Fifteen of the 16 were rowers or canoeists, and 1 was a cyclist.  Pelliccia included runners along with jumpers in the category of track athletes, and this group had a wall thickness that was on average 1.5 mm less than the rowers.  Part of this difference might be accounted for by the fact that  96% of the rowers were male whereas only 75% of the track athletes were male.  Perhaps even more importantly, the largest sub-group among the track athletes were sprinters, while only 12% were distance runners (covering a range of events from 3000m to marathon).  Almost certainly there were very few marathon runners, so the data for track athletes tells us little about long distance runners.  With regard to cardiac loading during training, long distance runners are probably more similar to cyclists than to sprinters.  The average wall thickness in cyclists was approximately midway between that of track athletes and rowers.

Granted that True ran for exceptionally long periods of time (up to 6 hours, often in arduous circumstances) I think it is quite likely that running was a major factor contributing to the thickness of the wall of his left ventricle, though of course, factors such as the genetic predisposition of his heart muscle to respond to training, and other aspects of his life-style including nutrition, probably contributed as well.   In their study of elite athletes, Pellicia and colleagues noted that all athletes with wall thickness greater than or equal to 13 mm also had enlarged left ventricular end-diastolic cavities.  Thus, if we accept that running probably contributed to the thickening of True’s ventricular wall, it is also probable that running contributed to the large diameter of True’s heart.

How might enlargement of the heart cause death?

But even if we accept that running made a substantial contribution to the enlargement of his heart, we are left with the question of whether or not it contributed to his death.  In an athlete’s large heart, the thickened walls are usually also well supplied with capillaries, and in most respects, the enlarged heart is strong and healthy. The absence of appreciable fibrosis suggests that his coronary arteries and capillaries provided this enlarged heart with an adequate supply of oxygen.  However,   we are left with the teasing question of the likelihood that an athlete’s enlarged heart will suffer rhythm disturbances, especially disturbance arising in the ventricles that might precipitate fatal ventricular fibrillation.  As reviewed in several of my previous posts, there us abundant evidence that many years of high volume training does produce a high rate of rhythm disturbances, mainly arising in the atrium, but a minority arising in the ventricles.  It is probable that the remodelling that occurs as the heart enlarges alters the electrical conduction pathways.

However, despite the evidence for frequent rhythm disturbances in athletes with a long history of high volume training, there is very little evidence to suggest that this leads to a higher overall mortality.  In my opinion, the balance of evidence suggest that the benefits of a strong heart outweigh any risk of rhythm disturbance under most circumstances.  But are there identifiable circumstances where the risk of rhythm disturbances outweighs the protection afforded by a strong heart?

Various nutritional and biochemical disturbances, such as elevated levels of calcium and potassium or low magnesium can increase the risk of rhythm disturbances.  Similarly decreased oxygen supply increases the risk. In a review of the literature, published in Sports Health: A Multidisciplinary Approach in  2010 (vol. 2 pp 301-306) Day and Thompson found a substantial body of evidence indicating that transient biochemical and functional abnormalities of the heart occur commonly following completion of a marathon.  There can be regions of transient ischaemia.  It is well established that the level of cardiac enzyme, toponin, in the blood stream is elevated for many days after a marathon.  While there is little reason to assume that this will lead to permanent damage to the heart, it is probable that this represents local cardiac tissue damage that might indeed be part of the stimulus to adaptive hypertrophy, but nonetheless, creates a period of vulnerability after a very long run.   Much of the evidence indicates that even well trained athletes can suffer such disturbances.

According to Chris McDougall, True had done a six hour run the day before he died.  I am very cautious about attaching much weight to such anecdotes and accept that the Medical Examiner’s  conclusion that the cause of death was ‘idiopathic  cardiomyopathy’  was a prudent conclusion in the absence of more detailed evidence.  Nonetheless, while I wish to avoid jumping to any strong conclusions about the cause of True’s death, I think that many of the features of the sad event  provide a salutary reminder of the accumulating evidence that a long history of high volume training does create a risk.  Overall this risk is largely offset by the benefits of a strong heart.   On the other hand, there are identifiable circumstances when the risk of rhythm disturbance is probably higher.  I believe it is worthwhile to try to understand these circumstances, and to develop practical procedures for monitoring cardiac stress level.

The ethics and aesthetics of mountaineering

This creates an interesting challenge that I believe that True’s life and death brings into focus.  Do we destroy the spirit of running if we make it too technical?  Years ago I was a climber – both a rock climber and also an alpine mountaineer.  When I first started climbing, we tied onto the rope with a loop around the waist secured with a bowline knot.    Some climbers used devices such as pitons or even bolts hammered into the rock face, but in my mind, there was one over-riding ethical principle in climbing and that was to leave the rock-face or mountain in a condition as near as possible to the condition in which you found it.  I was much happier with an odd collection of metal chocks and nuts threaded on wire or cord loops, that could be jammed in cracks or hung around projecting rock to provide the belay points that provide protection in case of a fall.  On snow and ice, I carried an ice axe with a stout wooden shaft.

Around 40 years ago, there was a revolution in climbing gear.  Ropes, karabiners, ice axes and much other gear became high tech items incorporating the latest developments in materials science and mechanical design.   It seemed to me that provided one was using the gear purely for safety and that one respected the principle of leaving the mountain as you found it, it was simply sensible to take advantage of the high technology.

However there was much debate in the climbing community, and a decade or so later the concept of minimalist free climbing became popular.  I remember watching spell-bound as an athletic young man moved freely, unencumbered by any gear apart from a thin pair of shorts, lightweight boots, and a pouch of resin at his waist, up and across the face of the Cow and Calf Rocks one sunny afternoon on Ilkley Moor in Yorkshire.  The sheer athleticism was a delight to the eyes.  Nonetheless, despite the fact that the Rocks are not all that high, the risk was also appreciable.  I did contemplate wryly the ethics of the resin, which the young man used to enhance the grip of his fingers on tiny nooks and crannies, and which in turn left horrible white smudges on the rock, but this was a small peccadillo in an awe inspiring display of physical and mental technique, strength and agility.   However, for the remainder of my climbing days, I continued to be happy to lug a sac of alloy chocks, synthetic tape slings and high tech karabiners with me when I went into the mountains. As long as I left a minimal mark on the mountains, I was quite content to tip the balance between risk and safety in the direction of safety.  In fact, developing the skills to maximise safety on rock or ice, and navigation skills in the wilderness, was an important part of my enjoyment of mountaineering.

What might runners learn from mountaineers?

In long distance running, the risk is less overt than in mountaineering, but the evidence indicates that the risk is real.  In most cases, the risk is small and is outweighed by the health benefits.  But just as the rock-climber faces a spectrum of choice between the simplicity of unencumbered free climbing to elaborate protection afforded by high tech gear, the long distance runner must find his/her niche along the spectrum that extends for the simplicity of the Raramuri in their huarachi’s, to high tech shoes and gadgets such as a heart rate monitor.  True was pragmatic enough to wear shoes – ranging from tatty trainers to highly commercialised ‘pseudo-minimalist’ shoes produced by Hi-Tec and Vibram, but I doubt that he ever wore a heart rate monitor.   I have experimented less with high technology shoes than True, but in my own philosophy of running, a heart rate monitor fills a niche not unlike that filled by alloy chocks, synthetic slings and high tech karabiners in a climber’s kit.

In general, I am eager to explore any technology that might help me to run with minimal risk to health.  On the other hand, I am very dubious about technology whose purpose is to enhance performance, and I am equally sceptical of the commercialization of minimalism.   I am amused rather than dismayed by Nike’s slick promotional video of its troupe of elite athletes running nude through the wilderness in an imaginative re-creation of South Dakota’s Bear Butte National Park.  It appears to me to be a clever ruse to reinforce the notion than running in Nike Frees captures the essence of running naturally.  I am even more sceptical of Nike’s Oregon project, which goes to the opposite extreme.   Nike’s elite athletes eat and sleep in buildings with reduced air pressure to mimic the effects of living at high altitude, while training at sea level.

The mechanism of healthy adaptation and of damage

Central to the emerging scientific understanding of the benefits and risks of training is the proposal that inflammation plays a crucial role in the short term beneficial adaptations to training, but that chronic inflammation might indeed be responsible not only for the generalised bodily and mental malfunction known as the over-training syndrome, but also might contribute to focal problems in lungs and heart.   The role of exercise as a trigger of asthma is well known.  However, the majority of recent studies suggest that regular mild to moderate exercise is has a beneficial effect on lung function.  Nonetheless, the possibility that very prolonged aerobic exercise might play a causal role in asthma has not been excluded.   Similarly, there is no doubt that regular mild to moderate exercise is beneficial for the heart, but, as discussed  above, the evidence indicates that beneficial adaptations can turn risk after prolonged arduous exercise, at least in some circumstances.

There is an emerging body of evidence regarding the various complex molecular signalling processes in the body that might mediate adaptive acute inflammation and also  mal-adaptive chronic inflammation.   Current understanding provides only tentative pointers towards the best way of minimising risk – but at the current state of knowledge, it appears that the most informative things to measure are heart rate and rhythm.

 What is worth measuring?

As an elderly runner with both functional and structural evidence of a heart that is strong but also large, I use a heart rate monitor with the capability to measure R-R intervals  to monitor several aspects of the electrical activity of my heart.  I keep an eye on the frequency of missed beats (which are likely to be ventricular ectopics that failed to generate the sharp R wave that the monitor is designed to detect).   I have abundant evidence that recordings made using my HRM during exercise are fairly unreliable, and I would not base any firm diagnosis on the information the device provides.  However, I consider that I understand its vagaries well enough to use it as a screen for possible problems.  Fortunately I only experience missed beats very rarely, but if these increase in frequency, I will seek an expert medical opinion.  The other aspects of cardiac function that I monitor with my HRM are intended to provide an estimate of the day to day stress on my heart.    I record resting rate and heart rate variability (HRV) regularly and in addition perform an orthostatic test on the days following exceptionally heavy training.  I record heart rate during the cool down after almost all training sessions, and have found that the stable value reached after a few minutes of the cool-down is a quite reliable guide to the amount of stress experienced during the session.

There is of course no way of entirely abolishing the risks of any activity we undertake.   I strongly believe that running generally increases the likelihood of both a higher quality and a longer life.  But I continue to try to increase my understanding of the circumstances that exacerbate the risk and also of the best way to minimize the risk.