The Kenyan advantage: Is it calf elasticity?

The Kenyan advantage: Is it calf elasticity?

The most recent study investigating the fascinating dominance of East African distance runners has found that Kenyan athletes have more elastic calf muscles than non-athletic whites.  Is this the secret to their success?  The reality is far more complex, and includes some major conceptual challenges facing research studies on Kenyan athletes

- by Ross Tucker

Towards the end of last year, Jim Ferstle sent me this article, written by long-time friend Amby Burfoot.  In it, Burfoot describes the results of a recent study on international level Kenyan distance athletes.  Burfoot does an excellent job of summarizing the study, and some of its limitations and implications, but very briefly:

• The researchers compared ten international level Kenyan runners to ten non-trained white males, matching them for height
• The participants performed a maximum hopping drill which isolates, to some extent, the contribution made by the calf muscles and Achilles tendon
• They measured various anthropometric outcomes (achilles tendon length, for example), and kinematic outcomes, like power, contact time, and rebound height
• The full list of what was measured in shown the table below, and I've highlighted in yellow the key differences between the Kenyan and white participants

To summarize, the Kenyans have:

• Longer Achilles tendons
• Shorter contact times during hopping
• Longer flight time
• Greater rebound height
• Greater jumping power

All in all, it's a picture of compelling and significant differences between the Kenyan and white athletes, and points towards greater elasticity in the Kenyan calves.  

The significance for running, of course, is that if the tendons are more elastic, the running economy is improved significantly, and this means faster running at lower oxygen cost.  At least, this is the theory.

What the study does NOT show: Kenyans are great because...

What the study is NOT, however, is any kind of proof of what makes Kenyan runners so good compared to European/Caucasian runners.  

And herein lies the catch.  When performing a comparison between two groups like this, it's very important to know what you have to match.  And if you don't match the groups correctly, then the conclusions you reach will be entirely misdirected, and this is what I would suggest is happening in this research study. 

To illustrate, the authors make the following conclusion in the paper:

"the Kenyan MG muscle–tendon unit is optimized to favor efficient storage and recoil of elastic energy".  

However, you could just as easily have concluded as follows:

"The muscle tendon unit of highly trained, international caliber athletes, is optimized to favor efficient storage and recoil of elastic energy when compared to people who are inactive and untrained"

The real problem with this study, at least in terms of its definitive application to the question of Kenyan running ability, is that it makes an unfair comparison.  If you take what are clearly crucial factors for performance in highly performing athletes, and compare them to the same factors in untrained people, you are destined to find a difference that has nothing to do with ethnicity or race, and everything to do with performance.  You are not so much measuring the advantage of Kenyans, as you are the advantage possessed by people who train and are athletic, and you could read the entire research paper, inserting the word "elite" every time you see "Kenyan" and it would make just as much sense.

So a lot depends on what your question is.  If you ask "What makes the Kenyans so good?" and you answer "They have elastic calf muscles", then you'd be making the mistake of over-applying the finding of this research.  If however you ask "What physiological characteristics may set elite athletes apart from sedentary folk?", then you can point to this study as providing evidence of another factor that ALL distance runners, not just Kenyans, need to possess.  What you don't know, of course, is whether the athlete becomes elite because of highly elastic tendon, or whether the tendon elasticity improves with training - that's an answer for a longitudinal study.

An incomplete picture, but not necessarily wrong

So, I don't mean to be too critical of the research, I think it's sound and provides very interesting data.  Perhaps most crucially, it identifies yet another physiological attribute of elite athletes - high tendon elasticity.  But you cannot extrapolate this study into the debate about Kenyan running dominance.  All it does, for now, is provide evidence that Kenyan athletes possess musculo-tendinous qualities that are likely beneficial for distance running, but it has not yet shown that these characteristics do not exist the world over.  It is thus incomplete, not incorrect, and requires that elite white runners and sedentary Kenyans be included in the results, which would complete the picture and allow a broader conclusion.

The true control group, to whom the elite Kenyans should be compared, however, is a group of performance matched athletes from Europe, or America, or perhaps even Ethiopia/Uganda/Eritrea.  I strongly suspect that if Galen Rupp, or Chris Solinsky, or even the Brownlee brothers, or any one of the fifty world class white middle- and long-distance runners, were included in the control group, the differences would disappear.  This should, I hope, be relatively obvious.

On that note, if you did test all these groups of performance-matched runners, and you still find differences, then you've found something really fascinating, because you'll have shown that the same performance can be the result of many different "input" characteristics, and there's not one thing that predicts performance.  This is arguably true, and it's why so many studies trying to find differences in things like VO2max or running economy fail - performance is multi-factorial.

The catch-22 of comparative research

So, if this study can't conclusively answer the Kenyan performance question, what is the study that is required?  Let me start off by saying that in 2013, I'm going to get a taste of this very challenge, because as I write this, a friend and colleague, Dr Jordan Santos Concejero, is about to board an aeroplane from Spain to conduct post-doc research with me in Cape Town, and we are going to be investigating a number of biomechanical, neurological and physiological factors in elite Kenyan runners.

I'll tell you those details at some stage in the future, but I will say that in the planning stages, our biggest question, by far, has been figuring out who to compare the Kenyans to.  We have some decent, but not great runners in South Africa - 29 to 30 min for 10km, and so if we compare Kenyans to these guys, we'll end up finding differences, NOT because they're Kenyan, but because they are 1 to 2 min faster than our control group!  Of course their VO2, lactate, economy, fatigue profile, EMG and mechanics are different - they're at a different level of running ability.

So, we now face the Catch-22 of doing Kenyan research.  I have no answer for you yet, but it is a real problem as we grapple with the questions of Kenyan dominance.  The reality is that there are not enough non East African runners in the world who can run 27-min for 10km to answer this question.  Galen Rupp and Solinsky are really the only two, perhaps Mottram in his prime was at that level, but the cupboard is bare.  I'll let you know what we end up deciding for our research!

What can be done?  One option is to compare completely untrained individuals from Kenya to those from Europe.  In this way, you eliminate the training confounder, and your hypothesis may be that Kenyans have greater elasticity even without training.  Another is to investigate children, for the same reason.  Saltin did this many years ago, but that study struggled because even at that age, there are such vast differences in lifestyle that Kenyan and Danish (in that case) are quite different.

Even here, however, you're not really answering the question, because you're still looking for a unique attribute thing, or even a group of attributes that can explain why an individual from one group can achieve more than an individual from another group.  I'd call this is the "unique factor approach", and it's probably doomed to failure, it's highly unlikely that the Kenyans have something unique, that the rest of the world does not possess.  

This is also the reason nobody has found THE gene for performance - there's not one thing.  And it certainly won't be present in just one tiny group of people, even if it did exist.  This is a futile approach, one that is often taken, and whose failure is often used to justify the idea that genes don't matter.  Nothing could be further from the truth.  All it means is that there is no gene, or other factor (like calf elasticity) that is unique to Kenyans or Ethiopians.  Or Jamaican sprinters, for that matter.  It doesn't mean that genes aren't crucial, as some have suggested.

Rather, what you have to look at is whether that unique factor, or collection of factors, is present with a greater frequency in one group than other.  That's the key.

The numbers effect - the reason for the dominance

And that leads me to my theory for Kenyan and east African dominance, and bear with me as I play the hypotheticals.

Let's say that there are ten characteristics that make elite runners who they are.  Economy, maximal oxygen uptake, biochemistry are there, and now add calf elasticity, Achilles tendon length and muscle power to the list.  These characteristics sum together to equal the great distance men who can run sub-27 min for 10km and 2:05 marathons.

To be in this elite group, you have to possess those characteristics.  The value of the latest study on calf elasticity is not that it differentiates Kenyans from other populations, but rather that it points us towards more of the factors that are non-negotiable for elite runners.

Now, all over the world, you'll have individuals who possess these characteristics - they tick the boxes. There's nothing in the Kenyan population that is unique.  No muscle fiber, no skinny calf, no elastic tendon, no enzyme, no brain, no heart.  They do not have 'exclusive rights' to some magical 11th factor that makes them better runners than the rest of the world.

But, what they might have, and this is my current thinking, is a higher prevalence of people with the "right stuff".  Out of a group of 100 untrained east African "aspirants", I'd hypothesize that more will have the right collection of running-positive attributes than a similarly trained group of 100 anywhere else.  If that group trains and is exposed to the right culture to excel in a sport, then the result is that so many emerge from the population with the ultimate outcome - performance ability.  We know that Kenya, Ethiopia and Eritrea have the right macro- and micro-environment, allied to a culture and history of running, that creates the perfect "melting pot" for endurance running.  If it is the case that the "right" genes, and hence physiological characteristics like muscle-tendon elasticity are more prevalent, then the dominance they have becomes clearer to understand.

That's my hypothesis - a higher density or prevalence of running-beneficial characteristics, to which training and lifestyle are applied in greater numbers than anywhere else.  Now all that is required is the proof!

Summary

The latest study is intriguing because it finds that calf elasticity and Achilles tendon length are different in Kenyan athletes compared to sedentary whites.  This is not however a finding that should be used to argue that Kenyans dominate running because they have more elastic calves than whites.  This is very unlikely to be a unique advantage, and there are doubtless individuals the world over who have the same attribute.

What the study does do is provide further evidence that tendon elasticity is a crucial factor in determining performance.  With respects to the Kenyan question, the next step is to ask whether the prevalence of this characteristic is greater in the Kalenjin population, because that may start to uncover why they are able to produce so many world class athletes, not neglecting the fact that the culture and training environment that has been created in Kenyan "unearths" so many of these exceptional runners.

As always, comments and discussion welcome.

Ross

Guest post: The Last Lance?

Guest Post: The Last Lance? - Dr John McGowan

This is the week when the world will "learn" from Lance Armstrong that he used performance-enhancing drugs. There is a 1000 page report from the USADA that already tells us this, so the exact role that Oprah Winfrey will play in this evolving theatre remains to be seen. The greatest initial criticism when Armstrong announced that he would sit in Oprah's confessional was that she would be soft, uninformed and unlikely to expose the full extent of his actions. Exhibit A - Marion Jones on the Oprah couch. But then again, there are 1000-pages to tell us the truth, so we needn't despair.

As for whether Oprah will know what to ask, unless she has sequestered herself in a cave for the last two weeks, she should, because enough people have told her what to ask. That included this from William Fotheringham (10 questions Oprah should ask), these five questions that Betsy Andreu would ask, and then the ten questions from David Walsh, which were published in the Chicago Tribune.

It has also been reported that Oprah's team has been in contact with the Lemonds, the Andreus and David Walsh, to find out their perspectives on Lance's deception. But, it's one thing knowing which questions to ask, it's quite another to know the questions (and challenges) in response to the answers, as David Walsh pointed out on Twitter this week. The best example of this comes from this excellent article by Joe Lindsey, who points out that some of Armstrong's 1999 samples that tested positive for EPO contained no naturally-produced EPO. It was all synthetic. The implication? Armstrong had been doping for so long, so aggressively that his body had stopped producing its own EPO. That is the context that is necessary in the event that Armstrong argues that he only doped "a little" to keep up with the culture of the sport. These are nuances that matter, and which will likely escape this particular "confession".

Also, there's a really good chance that Lance will invoke the "everyone was doing it, so it was a level playing field" argument. This is completely nonsensical, because doping clearly doesn't affect everyone equally - it's a matter of physiology and morality, and of course some were prepared to try to get away with more than others. Having exclusive rights to the least moral doctor helped, and so did blowing the whistle on fellow dopers who were beating you. Not to mention the fact that not everyone was doping to begin with, so someone in those races was being defrauded. So let's hope that Oprah doesn't sit there with deer eyes and accept this lazy, utterly incorrect argument about a "level playing field". For more on this, refer to Point #3 in this article that I wrote in August last year

The strategic angle - how best to manipulate public opinion?

The story of Lance Armstrong has been an evolving production, now into its final act. Maybe. Probably not. I haven't written much on it at all, primarily because there are many others who do it so much better (like Joe Lindsey, and this piece, which is rightly scathing of Armstrong, and describes his likely justification for doping - "I did the bad thing for the greater good"), and whose job is to cover this kind of news. But it's also because there's "Lance fatigue" - it's been five months of endless Lance coverage. When that USADA Reasoned Decision came out, followed by the 1000-pages of supporting evidence, the book was closed. It was over. For some, of course, the denial has been more stubborn, but I think most were swayed by the sheer strength and weight of evidence.

However, the story has refused to die, and now, in the latest play, Armstrong has turned to the priestess of television. I've provided links to the best of the articles over on Facebook and Twitter, for those who want to keep up to date through the social media platforms. But the response to many links has indicated that you too are suffering from Lance-induced burn out. 

But, alas, there is more to be said. A big part of the fascination with the Oprah interview is that Lance has always been strategic and manipulative, and this is likely no different. We suspect we know his intentions - media coverage, becoming relevant again, having his ban reduced to allow him to compete again. Quite how he plans to achieve the 'end-game' has been the subject of endless speculation, and therein lies the story for now. Will he admit to everything? Will he apologize? Does he have information that hasn't been revealed, and will he name those who facilitated his fraud? That means Ferrari, Bruyneel, the UCI, Verbruggen, McQuaid and co. Doping is only part of it - the intimidation, the bribes and payoffs, the threats and the legal bullying of those who dared to tell the truth is what sets Lance Armstrong apart from the sport's other dopers. Will Oprah Winfrey recognize this? Only time will tell.

For more on this, rather than repeat what I've read, I post below a guest article written by Dr John McGowan, who has previously written for us on the Armstrong story. McGowan is the Academic Director of the Department of Applied Psychology at Canterbury Christ Church University in Kent. He previously tackled the issue of whether doping should be legalized as well as the psychology of Lance's unpopularity, and today discusses the possible outcomes of the Oprah interview. Here is his piece:

The Last Lance, by Dr John McGowan

I thought I’d had enough of Lance Armstrong. Really. Lately I’ve felt completely sated with battles, dominance, accusations, denials, aggression, petulance, banal tweets, more battles, disgrace, and ultimate capitulation. Though whether his decision not to contest USADA’s charges was indeed capitulation depends on who you ask. After all, as of today, he’s still admitting nothing. Truth told, I didn’t care. Me and Lance were through. However, suddenly it seems that his interest value might not be completely played out and that there may be one more great spectacle to rival Luz Ardiden in 2003. As anyone with a pulse-rate monitor (or even just a pulse) knows, on the 17th of January, Lance is going head-to-head with Oprah.

I’m clearly not the only one who’s been snapped out of an uninterested torpor. Suddenly all those people eager to tell us what a poor human being he is, and how they too are over him, are speculating wildly on what he will say. Will he come clean? Go on denying? Why is he doing it? Can he come back into the public’s affection? Go into politics? He’s loaded still isn’t he? Or is he broke? Is this the beginning of his rehabilitation? Or the last hurrah? I can’t pretend to know what he’ll say or what the effect will be, but I have a few thoughts on what the constraints on him are and whether or not this really is the end.

Around the time of USADA’s “Reasoned Decision” I wrote a post here discussing the ethics of doping. Though we often treat dopers as pantomime baddies, the issue is a little hazier than that. There are even those who advocate a liberalised regime around performance enhancements in sport. Such arguments are based on a judgement that fair competition and safe sport are illusory, that much of the harm caused by drugs flows from under-the-radar use, and that the authorities are unlikely to ever catch up with what the athletes are doing.

There is something to be said for all of these positions, though I went to some lengths to say why I didn’t agree. The broader point though, is that advocating doping in sport isn’t simply a kooky position that is easily dismissed. Rather an informed opinion requires appraisals about where you stand on these different issues. It’s clear that doping may be the result of a range of considerations and pressures, and the caricature of the “dirty doper” may mask a more complex reality. Given this, my other main contention in the earlier article was that the beefs many have with Lance are related to his dishonesty rather than his drug-taking, and far more about his bullying than his breaking of the rules.

Full tearful confession?

The interview with Oprah is being sold as “no holds barred”, and the primary question flying round the internet is “will Lance finally fess up?” The emerging consensus seems to be a resounding, "No". Why? Well firstly there is Oprah’s interviewing style, widely perceived as too soft to expose the more uncomfortable stuff. Additionally you might wonder whether she or her audience is likely to be informed about the nuances of Lance’s EPO profile in the year after the Festina affair. 

He may also be unwilling to come completely clean voluntarily for various reasons. There is a delicate web of legal considerations he has to navigate (outlined here in an excellent piece by Joe Lindsey). To this I’d add what we know of Lance’s own attitudes. This is a guy who didn’t just want to win races. This is someone who, as former soigneur Emma O’Reilly described it, was so alpha he basically felt he was cycling. And someone who transcended his sport completely. This was a kid from a tough background who became the “Cancer Jesus”, who courted rock stars, and who called the tune for Presidential candidates. Going from that to being an ordinary mortal, prone to weakness and error, is a long fall and you get the feeling that, if it was going to happen, the tearful confession would have come some time ago. 

It must be quite awful to be inside his head right now. We know how invested in that identity he was, from how hard he fought when it was threatened. What can it be like to to lose it? Confession might happen of course, but I suspect penitence is not really Lance’s style. With all the murky water that’s flowed under the bridge you also can’t imagine that he can do a Marion Jones (another Oprah disgrace special) and admit drug taking while saying he thought it was ginseng or intravenously administered red zinger. 

Continued denial?

If complete confession is off the table then, surely, so is continued denial. To continue on this path would maintain the current surreal limbo where his statements have no credibility and supporters cling to conspiracy theories. And anyway, if he is just going to stonewall why bother going through the whole charade? It seems likely he wishes to open the way for a return to competition (presumably dominating the world of veterans’ triathlon) and regain some measure of public esteem. If the rumour mill is to believed, the interview is partly a result of pressure from Livestrong and it’s hard to imagine that they would be happy with a continuation of the status quo.

Hedged admission?

So what can he possibly say that will help him? The most convincing prediction I’ve read comes from cycling journalist William Fotheringham. He expects a rather hedged performance, with some vague half-admissions, and suggestions that he didn’t do anything different from what everyone else was up to. That something like this will be the tactic has subsequently been borne out by advance PR from the Armstrong camp. Presumably this would make a decent platform to cast doubt on other elements of the evidence against him as exaggerated or vindictive. This kind of tightrope walk between impossible alternatives sounds like a tough gig, but I expect Lance has been training for it with the intensity he used to reserve for L'Alpe d'Huez. Still, even soft interviewers can simply give you just enough rope (as Oprah did with Marion Jones). Coming out of this unmarked is not a foregone conclusion.

Fotheringham goes on to suggest that, if Lance can pull off this strategy, then a measure of rehabilitation might be possible: among Yanks who know nothing about cycling, if not the more hostile public elsewhere. It worked for Richard Virenque who still trades on his rather soiled King of the Mountains jerseys. The path to rehabilitation is also well trodden by others. It doesn’t seem too far-fetched that admitted doper (and now vociferous clean sport campaigner) David Millar will end up as one of the governors of cycling. And who's to say that’s would be a bad thing? OK, Lance’s malfeasance may be of a different order in terms of scale and in his role as an instigator and intimidator.

However, in an environment where Mike Tyson has movie profiles devoted to his introspective complexity and Chris Brown duets with Rihianna, there doesn’t seem much that celebrities can’t come back from. Perhaps Jimmy Savile-style crimes or life-threatening violence but in the UK, even a confederate of the Kray Twins, “Mad” Frankie Fraser, has spent a good portion of his twilight years being a kind of celebrity goon. This is despite being colloquially known as “The Dentist” for levels of oral brutality that I’ll leave you to imagine.

The unforgivable sin?

For all the redeemed souls knocking about though, I’m still not confident that Lance can become one of them and mount a comeback. As I’ve argued before, the key comparison here is with Tiger Woods. In a world where so many sins can be washed away by fame, there is one that is unforgivable: that of trashing your own public image. In Tiger’s case it was the perception of him as preternaturally focused and mentally strong, above ordinary mortal weakness. Since that one went out the window he has managed to find his way back in golf (though hardly to his old form), but his public standing and commercial value have taken a permanent nosedive. Chris Brown or Frankie Fraser may have done terrible things but they were never really perceived as anything more than vicious thugs. They didn’t have any public standing to lose. In cycling Virenque or Millar hadn’t anything like the fame or the heroic stature of Lance Armstrong. The nature of his transgressions means the incompatibility between the Armstrong brand and his actions is now vast, and the hero of old is gone forever.

Tiger is still competing and there is some residual interest in whether he can win another major. I’m struggling to see what new reason Lance can give the public to pay attention to him again. Cancer inspiration once more? Good luck to those who find him so, but for most, I suspect that ship has sailed. Victim of a conspiracy by the authorities and an unfair media machine? It might appeal to a few but I certainly won’t be pre-ordering his next volume of memoirs. Anti-doping convert à la Millar? In a parallel universe maybe. A full confession might help bolster WADA and USADA’s credibility but I’m wondering now how many people would actually care. I guess it’s possible that he may have some role in sport once more but that’s hard to see unless he can find a rapprochement with USADA . Other than a complete confession I’m not sure how that would happen and they don’t really need to do a reduced-sanction deal with him anymore. His failure to strike such deal before the reasoned decision was significant misstep for the master of the well-timed move. 

Perhaps part of the interest, and the poignancy, of the Oprah appearance is that it’s not clear whether this will be a re-launch (of a minor sort), or if Lance will simply fade from view. No-one really knows but one thing is certain. Even if he does find some way back, very few of us will ever live strong again.

Dr John McGowan

Year/Academic Director,

Department of Applied Psychology

Canterbury Christ Church University

Kent

Your comments, as always, are welcome. Dr McGowan has promised to also respond for those who fancy a discussion around his piece. Until the show, discuss away!

Ross

Dangerous exercise: The hype of dehydration & heat-stroke

Dangerous exercise?  Dehydration, heatstroke and cardiac risk

Let's kick off 2013 with some thoughts on a sad, but important news story coming out of South Africa. I missed this one, being overseas at the time, but a colleague and I got to talking yesterday, and it's really a very startling reminder of the potential dangers of uncontrolled exercise, without adequate safety awareness and screening.

Here's the story:

A regional division of the South African traffic department held a recruitment drive, looking for 90 potential traffic officers.  Inundated by the response - over 35,000 applicants for the 90 jobs - the department used a 4km fitness test as a "filter" of sorts to trim down the numbers and arrive at their best 90 candidates.

In late December, in the small town of Pietermaritzburg, over 30,000 applicants, aged around 18 to 22,  took to a 4km time-trial, effectively racing for employment.  South African summers mean heat, and the temperatures were above 30 degrees Celsius (about 90F).  The end result of the catastrophe was six deaths, attributed in the media to "dehydration" (more on this below), plus a suicide after the race in frustration at not qualifying.

You can read more on this, including statements from the head official, at this link.

Whether a fitness test 4km time-trial is a suitable way to squeeze 30,000 into 90 can be debated, as can the obvious implications of this for South Africa's employment problems.  It is a story that has political, management, administrative, socio-economic and even health implications.  But let's stick with the physiology, and discuss the risk of dying during exercise, because it's a topic that unfortunately comes up often, and the lessons that can be learned are important.

Just last year, in the London Marathon, a 30-year woman died within sight of the finish line, making news headlines.  At a hot Chicago marathon in 2007, a man died amidst accusations of the danger of running in the heat - his death was attributed first to dehydration and heatstroke, later to an existing heart condition.  Even elite athletes are not immune - Ryan Shay during an Olympic-qualifying marathon in New York, and Fabrice Muamba during a Premier League Football match.  It's a recurring event, often, but not always linked to high temperatures.

Dehydration - the ever-present scapegoat, for everything

Unfortunately, the media continue to propagate a temperature and dehydration myth, which helps nobody because it obscures the more likely causes.  In the case of the six traffic officer deaths in South Africa last week, the first line in most media accounts was "six people have died from suspected dehydration".

Let's be clear - you cannot die from dehydration within the first four kilometers of any endurance event.  It's just not possible - the body has too much water to reach a critical level of dehydration, whatever that even means.  Dehydration is the easiest diagnosis to make, because we have all been so 'drowned' by marketing messages that tell us that fluid loss is a potentially catastrophic risk during exercise and that if we do lose fluid, we will be in mortal danger of dropping down dead.

Physiology says that the body is well able to withstand quite large fluid losses with no detrimental effects on performance or health.  It had to be this way, because hunting for our survival didn't benefit from an "-ade" station every 2km, and those who have heard of persistence hunting will also know that a common tactic was to hunt larger animals in the hottest part of the idea, exposing the animal (and the hunter) to many hours of prolonged exercise, without fluid, in the heat.  It worked, because we are adapted for this.

Supposedly, as little as 2% dehydration impairs performance by 10%, which is amusing because when the world's elite marathon runners finish in 2:05, they have lost at least 2% body weight, which means they're running two minutes slower than they would've done had they listened to many Gatorade advertisements and scientists sponsored to tell this "truth".  The problem is not dehydration, it's thirst - the discomfort created by feeling thirsty is without doubt detrimental, which is why drinking ad libitium, in response to thirst, is both good enough to ensure our health and to optimize performance.

But we're not talking performance here, we're talking mortality, and again, dehydration in an event lasting at most 25 min, is just not on the table.

Dehydration is also blamed for other heat-related afflictions.  On Monday night, I watched the BCS Championship Football match, and within about 30 minutes of play, the Alabama quarterback AJ McCarron was shown receiving treatment to his calf muscle on the sidelines.  The commentators (who part of me can excuse for not knowing better, but part can't), speculated that the high humidity in Florida, where the match was played, was to blame for muscle cramp.  This after probably only 20 min of playing time for the player.  It was later revealed that the calf was injured by contact, not cramp.  But again, it highlights the dogma that says that dehydration, among many other risks, also causes cramp, which simply does not make physiological sense, and has recently been discredited by laboratory studies and theoretical flaws (I'll dedicate a separate article to this in the near future)

Similarly, there is no link between fluid loss and heatstroke.  Human beings can safely lose big volumes of fluid without their body temperature shooting through the roof.  Typically, in a marathon on a reasonably warm day, we lose about 2 to 3 L of fluid over many hours.  Faster runners lose more - Haile Gebrselassie is reported to have finished his Berlin World Record 5kg lighter than at the start.  We have a race in South Africa, the Comrades Ultra-Marathon, run over 90km, from morning to evening, with temperatures typically in the mid- to high-20s for about six of those hourse, and controlled research has found that most of the field finish with around 2 to 4% body weight loss, a proxy for fluid loss.

These people are not ill.  They may be thirsty, and they sure are tired after 11 to 12 hours of exercise, but there is nothing medically wrong with them.  Their body temperature is normal for exercise - that is, elevated to perhaps 39-40 degrees, but this is expected.  I can all but guarantee that none of the six men who tragically died in South Africa, or any of the other high profile deaths, which tend to happen in people who are running relatively slowly and in cool conditions, have lost anything like 4% of their body weight.  So when next this happens (and it will), let's immediately disregard the diagnosis of dehydration being the killer, because it simply isn't true.

Heatstroke - an abnormal physiology in most instances

Heatstroke is a viable candidate for the tragic deaths that sometimes happen, but it's a grossly overstated risk and those who diagnose any athlete's collapse or medical condition on a hot day as 'heatstroke' are also taking a lazy and possibly very wrong option.  The reality is that heatstroke is a pretty complex phenomenon, and is likely to involve some kind of pathology.  Once again, I'd draw attention to the difference between the perception of being hot and actually getting to the kind of dangerous temperatures that characterize heatstroke.  We're not talking about feeling hot, uncomfortable and slowing down or stopping here.

Five years ago, I was a co-author of a paper that was written to investigate five hospitalizations during mass-participation events here in SA.  Four people died during a 109-km cycle race, and one was hospitalized during a 56-km Ultra-marathon.  As is the media way, all were blamed on dehydration and heatstroke.

However, once the specific cases were investigated, the interesting discovery is that none of these athletes was exercising at the kind of exercise intensity that would be needed to raise their body temperatures to the levels measured.  An important point is that these cases actually were CONFIRMED as heatstrokes, based on the symptoms observed in hospital, and their highly elevated body temperatures - all were well above 41 degrees celsius.  This is unusual, because many times, the temperature is not measured, but the death is attributed to heatstroke anyway because of "lazy" diagnosis.

The principle here is that body temperature rises during exercise as a result of heat produced by muscle contraction, and the harder we exercise, the higher it goes.  We lose much of the heat through convection (wind cooling) and evaporation (sweat), but we "settle" on a temperature up around 39 degrees.  That's homeostasis in action.

In these athletes, that clearly hadn't happened.  They'd overshot, gained too much heat and ended up critically ill.  Now, there are only two ways for this to happen.  The normal control of body temperature is a balance between heat production and heat loss.  So to overshoot the normal homeostatic control of body temperature, they have either produced excessive amounts of heat, or their heat loss mechanisms have failed (of course, a combination of both is possible too).

But "normal" heat production cannot explain most cases of heatstroke.  If you are running a 4-hour marathon, or cycling along at 15 km/hour, you are not producing enough heat to raise your body temperature to critical levels.  This is what the athletes were doing in the study.  It's different for elite athletes who are doing shorter, high-intensity exercise.  Running a 5km or 10km time-trial, with extreme levels of motivation, can put an athlete right on the boundary of what one would call "uncompensable heat production".  Closing the final 10km of a marathon at world record pace can push the rate of heat production high enough that if the environment is too warm, it becomes potentially limiting and the athlete must slow down.  This is why the world record for the marathon will become more and more difficult to break - it is now close to a thermal limit and so requires absolutely perfect conditions for it to happen.  Even a degree too warm over the final 10km is too much.  In our lab studies, the highest body temperatures we measure are at the end of 10km time-trials in hot conditions.

But recreational athletes don't produce enough heat to develop heatstroke through normal muscle activity.  Therefore, we look at alternative theories - either these individuals are failing to lose heat, or they produced excessive heat from unnatural means.  We called that "excessive endothermy" in the paper, and considered it more likely, because convective cooling on a bicycle is large enough that even a loss of sweating can't explain how people overheat so quickly in these events.

I'll never forget being in the medical tent for one of the cases - the runner was brought in, his temperature measured and found to be elevated - above 40.  He was placed in a large tub of ice-water for rapid cooling.  Over the next half and hour, he got even hotter.  Sitting passively in ice, with the most enormous cooling method you can imagine, this athlete was still producing enough heat to push his already high body temperature above 42 degrees celsius.

Also of interest is that many of the documented cases of heatstroke (that is, published in the literature, complete with diagnosis and description), have occurred in cool or moderate conditions, very early on during events, and with low intensities.  Here are two examples:

1. A 17-year old army trainee develops heatstroke (40C) after only 15 min of fast walking at only 8min/km.  The air temperature?  Only 17C.  One hour after admission, his body temperature has climbed to 42.8C, while he remains unconscious (Parnell, 1986)
2. Runner collapses with a body temperature of 42C only 45 min into a 10km fun run at a moderate temperature of 24C.  This study documented what were described as 15 cases of heat problems, ranging from mild to serious, out of a field of 13,000, and it wasn't even particularly warm.  Only one was true heatstroke, however, the others were just feeling hotter than usual because they were unacclimatized to the conditions, and this is often confused for 'heat illness' - there's a big difference between feeling hot, and being hot, and training status affects that more than anything (Hughson, 1978)

When you work out the rate of heat production and compare it to the potential rate of heat loss given the documented environmental conditions in these events, you discover that there is no normal way for any of these athletes to overheat unless something goes very wrong (see the Endothermy paper for more).  

So the key points from those case studies - there are 18 documented cases, I've only discussed three - is that the athletes who suffer REAL heatstroke most often are not exercising very hard, they're not in impossibly hot conditions, and they show 'abnormal' heat gain even after they've finished exercise, sitting out of the heat (in a bucket of ice, in one case).  Clearly, there's something else going on, and heatstroke does not happen just because we run hard on a hot day.  

Having said all this, in the case of the six traffic officers, you did see a perfect combination of factors for some of these athletes to develop genuine heatstroke.  That's because they were highly motivated (90 jobs available, 1 in 300 chance), untrained (our ability to tolerate and lose heat is poorer when untrained) and running for only 4km, which means a very high relative running intensity, and thus higher rates of heat production.

Were they heatstrokes?  Only by measuring body temperatures at the time would this ever be confirmed, and I don't know if this was done.  Autopsies may shed further light, if done, because they reveal changes in the muscle that point to excessively high temperatures and pathological conditions such as rhabdomyolysis, which is one of the likelier candidates for the 'abnormal' heat production that I described above.

A colleague of mine, Dr Tertius Kohn, is studying the muscles of animals that are captured or hunted in the wild, because there is evidence of heatstroke in these animals.  I once accompanied him on a muscle-obtaining trip, and remember cutting muscle out of an antelope that had been hunted.  The muscle was, quite literally, cooked.  It resembled a menu item at a restaurant, and his working theory is that under extreme stress, with the right pathology or underlying muscle condition, excessive heat production can overwhelm homeostasis.  Is this what happens in humans?  Possibly, though too little is known at this point to make any conclusions.

Exercise and sudden death

So if not heatstroke, and if not dehydration (highly, highly unlikely), then what is the most likely cause of death during exercise?  Again, this is a topic we've discussed a great deal here on The Science of Sport, and I'd point you to these two articles - one written to discuss potential causes of death after Ryan Shay's death in New York, and another giving some perspective to the issue

But if you really want to learn a bit more about the prevention of sudden cardiac death, then listen to this podcast, by BJSM with Prof Jon Drezner.  In it, he talks about the prevalence, the accuracy and sensitivity of screening, the treatment, the prevention and the education.

The problem is this - there are conditions, underlying and dormant, that increase the risk of sudden cardiac events.  A precipitating event can take the form of endurance exercise, the result of which is that the athlete, for all intents and purposes healthy and fit (the London Marathon death, Claire Squires, had just climbed Mt Kilimanjaro), can suffer a cardiac event.  Drezner describes a prevalence as high as 1 in 40,000, which means that every major city marathon has 'candidates' for this kind of tragic event.  So too, the 4-km fitness trial of the traffic officers is likely to expose at least one person to the kind of "precipitating event" to trigger sudden cardiac arrest.  It's no guarantee that it happens, and nor is it guaranteed to be limited to only one.

It's quite possible, too, that the prevalence is higher in some populations, either randomly or determined by other existing medical conditions, and that the addition of heat as a stress makes it even more likely that the event will occur.  Now, in the case of most marathons, the runners who line up on the starting line are to an extent "self-selected".  The 30,000 traffic officers were not, and so in their untrained states, exposed to the stresses of a maximal time-trial, on a very hot day, without screening for those conditions, you have the ingredients for a potential disaster, which is what transpired.

Also, the media coverage is disproportionate in the case of these events occurring during public events.  Consider how many cases of cardiac arrest go unnoticed because the person with the risk condition leads a sedentary life.  But, when it happens on a football field during a televised match, or during a US-Olympic marathon trial, then the world takes notice, because our expectation is that it shouldn't happen.

Quite what to do about it is difficult.  For professional athletes, the screening debate starts up every time there is such an event.  Drezner talks about this in detail in the podcast, and I also wrote some thoughts on it here.  Treatment is clearer - the risk of dying as a result of a cardiac arrest decreases from about 50% without an emergency defibrillator, to between 5 and 8% with an emergency defibrillator, so the presence of equipment and personnel to administer treatment is crucial.

Ultimately, there will be deaths during exercise that are neither predicted or preventable, at least for now.  Proper training, adaptation to the environment, screening and treatment greatly reduce the risk, but don't eliminate it altogether.

When trained runners line up to run a marathon, then even in very difficult environmental conditions, the risks are small and probably unrelated to the conditions.  But when untrained individuals, be it fun-run athletes, or aspirant traffic officers, try to run at maximal levels, then even short runs or moderate conditions suddenly start to pose great challenges to the physiology.  It's a lesson to heed because it emphasizes the obvious value of training, as well as the importance of staying aware that as much as trained athletes do things that seem mundane, the physiology can be, under the right (or wrong) circumstances, more 'fragile' than we think.

Ross