Deaths during running: Is exercise safe, Part 2

Running and safety continued - some comparisons, and the key point to the debate

One of the best things about this site is that often it is a source of information for me as much as I hope it is for you! And in response to last week's post about the safety of running, we've had some great comments and more information, which warranted a follow up. Also, I felt I should re-emphasize the purpose of that post, which was really a call to the media to change the view they project of running.

And most importantly, it was a message to runners out there to help them 'filter' out what is basically over-hyped reporting about deaths during running, akin to the "shark attack" phenomenon, where sensational reporting skews our beliefs over the relative safety of an activity (surfing in that case, running in ours). Perception does not necessarily equal reality, in other words, and the post was a call to question very hard what the risk of running is. If you do, you'll find that it's not nearly as high as is sometimes portrayed!

And now we have some points of comparison, thanks to you readers!

Host a marathon every weekend

First off, a study last year from the British Medical Journal took a rather creative (Malcolm Gladwell-esque) look at marathon safety. Canadian researchers compared the risk of dying in a motor vehicle accident with that of sudden cardiac death during marathon participation. Because courses are closed to traffic for larger races, it's possible to ask how many motor accident deaths would have been prevented as a result of the race, and compare this to actual deaths (thanks to Bengt, Tony and Amby for raising this one! As an aside, the author Redelmeier seems to be an expert on driving fatalities - another 2008 study published in JAMA is called "Driving fatalities on US presidential election days")

The diagram below summarizes the main finding:

So basically, the study found that the closure of roads for the major marathons prevented an estimated 46 deaths as a result of motor vehicle accidents. However, 26 sudden cardiac deaths were reported during those races (based on newspaper reports, it must be pointed out, and thus potentially a slight under-estimate). The relative risk - 35% lower when marathons happened.

And a final really important point - the authors have controlled for the accidents simply be relocated to other areas, and so marathon closures do not simply shift the site of the accidents. If you want the paper to check out their solid stats, please just let me know, as usual.

The author's conclusion is shown in italics above, but it was that "Organised marathons are not associated with an increase in sudden deaths from a societal perspective, contrary to anecdotal impressions fostered by news media."

Some numbers

Interesting that they picked up on the "impressions fostered by news media", which is basically the point of these last two posts. Interesting also that in 14 million hours, there were 26 deaths, which amounts to approximately 1 per 540,000 hours, a figure which agrees with that which our friend Amby Burfoot put forward in his comment to our last post. For a similar analysis, check out Amby's report on marathon deaths written last year, which is far more comprehensive than I've had time to do here - it's a big read, but if you're up for more details after this article, check it out.

This figure of 1 per ± 500,000 hours is also about the same as a (very) crude calculation would provide based on the information that about 6 deaths occur every year in the USA, and that about 3 million hours of running go into those deaths (this was all covered in the last post, if you want to read the numbers more).

My point, however, not covered by this study or the latest reports, is that marathon running hours are not limited to the hours of participation. There is substantially more time spent running in training, and by those who run but don't participate. If you factor all these people in, do the numbers change? Without quantifying training times, it may remain an unanswerable question.

These people, and their training, are the most important component of the debate, because they are most likely to be dissuaded from running as a result of the negative portrayal of running. Yet they are clearly, based on a large body of research by the likes of Paffenbarger (again, see the previous post), more protected than the sedentary population, and so should be hearing affirmation, not condemnation or warning for their choice to run. And if running in events that may have a risk of 1 death per 500,000 hours is the goal, then it too should be encouraged.

Comparing running with some other activities

To compare running a little better, have a look at the comments to the previous post, where you'll see some stats about how many deaths are caused by other activities. Smoking, for example, claims over 300,000 each year. Flu, 15,000, and car accidents, 20,000. Of course, the problem here is that these numbers don't indicate the 'exposure', or how many people spend how much time doing the activity. Smoking may simply be high because many people smoke, whereas 6 sudden deaths during running may be because hardly anyone runs.

Risk and exposure

So, for another comparison, I received data from a reader who had put together some stats on deaths per million hours of the activity. That piece can be read here, and the original article is here.

Admittedly, it's a little uncertain where this data were sourced, and in this field of epidemiology, that is crucially important. So with a proviso that the data is not "gospel", here is the summary list:


Deaths per million hours:

Skydiving - 128.71
General Flying - 15.58
Motorcycling - 8.80
Scuba Diving - 1.98
Swimming (presumably competitive) - 1.07
Snowmobiling - 0.88
Motoring - 0.47
Water skiing - 0.28
Bicycling - 0.26
Airline Flying 0.15
Hunting 0.08


Running? Depending on which number you believe, the risk during marathons is between 1.8 and 2 deaths per million hours, so it's around the same as scuba diving.


One problem - that doesn't factor in the health benefits, which I emphasized previously. Regular physical activity reduces the risk of cardiac disease and a host of other health problems, and so the risk is moderated by the benefit.

Most important of all - applying this dizzying collection of numbers to yourself

To end off (before we tackle some more enjoyable topics like coaching and science in the coming days), a word on applying this to you. I know I've thrown figures and numbers at you, and your head is probably spinning, so let's try to simplify this.

The reality, at the risk of sounding callous, is that people do die during running. A big race, with 30,000 runners, seems likely to experience such an event every 3 to 4 years. Put differently, between the six major marathons each year, there would be a sudden cardiac death each year.

People who are predisposed to cardiac death are more likely to die while running than while sitting on their couch. This is undeniable. But equally, people who run, including those who run marathons, derive enormous benefit from it - their health gains as a result of running are sufficient to over-ride habits like smoking in terms of overall risk of mortality (Paffenbarger, et al).

You can investigate whether you might be one of those predisposed, higher-risk people, but the problem, as we've discussed at length before, is that medical testing cannot currently identify all the people at risk. Some, certainly, and so medical screening, particularly if you are concerned, would be advisable.


Even in the absence of such 'confirmation', however, you still have a choice. With the risk at one death per 500,000 hours of running, and with the knowledge that running can improve your health, your choice is to remain sedentary and avoid that 0.8 in 100,000 runner chance, or you can run and benefit from the numerous positive adaptations you'll experience. It is a risk-management matrix, where running and remaining sedentary must be weighed against one another, benefits and risks understood, and a choice made. Your ability to manage the risks, by undergoing tests, by training and by adopting a healthy lifestyle, makes this choice far simpler than leaving it to guess-work.


And finally, for the media, physical activity should be encouraged, not 'demonized' with threats of death caused by activities like running. Sensational sells, but when it deters people from running, it becomes a problem. So some perspective, some affirmation and positive reporting would go a long way to fixing what is a growing problem of inactivity and obesity, subtly being driven by the media reporting. By all means, educate and inform people of how to maximize benefits, but let's not give a voice to those who view exercise as radical from the safety of their couches.

Ross

P.S. As mentioned, a series on coaching and the application of science starts tomorrow. Join us then!

Further reading:

Amby Burfoot, Editor-in-Chief of Runners World has done a comprehensive piece on safety of marathon running. I've tried to make this article (and the one before) more philosophical and directed at the media coverage, whereas his is full of information and 'hard facts'. But this is a great piece, and if you're up for more reading, this is a great read:

Amby Burfoot: SPECIAL REPORT: ARE MARATHONS DANGEROUS?

Deaths during running: Is exercise safe?

Sudden death during exercise:  The media, risk and running

For those who have not heard or read the news, three runners died during the Detroit Marathon/Half-marathon last weekend.  All three were running the half-marathon, and were aged 26, 36 and 65.  The three collapsed within 16 minutes of each other during the race.  The timing, the wide spread of ages, and the fact that three deaths occurred in one race (which was not hot, I might add) have given the story 'legs', and it was even covered on CNN.

Whenever this kind of incident happens, there is debate and discussion around the safety of running.   It's always bad press for running.  It is a topic that pops up fairly regularly, and we've actually covered it in a fair amount of detail here on The Science of Sport.  I'm not going to go into enormous detail on sudden deaths during exercise again, but for those who are interested, you may like to read the following posts:

• Sudden cardiac death in runners (a post in response to Ryan Shay's death)
• Sudden death during exercise - practical implications and perspective
  

A general perception of safety

So as I said, I wouldn't ordinarily post on this topic again and in the case of the Detroit runners, I don't know the cause or any details, and so it would be wildly speculative to discuss specifics.  However, this latest incident, and the media reporting around it, reminded me of a thought I'd had while watching the NBC coverage of the Chicago Marathon about 2 weeks ago.

You may recall that Jonathan and I were in the control area, doing real-time pacing for the race, and also spent some time in the medical tent.  But it was watching NBC's coverage, that I was struck by the fact that the person who was interviewed the most during a 3 hour broadcast was the race doctor, George Chiampas.  On no fewer than four occasions, Dr Chiampas was featured in a two -minute interview, giving his thoughts on race hydration, race safety, post-race safety, recovery, training and so forth.  And while he answered the questions very well, it was clear that the 'safety/danger' of running was of utmost importance to the broadcaster.

It struck me that there is a very real perception among mainstream media in the USA (remembering I'm from South Africa and so normally unaware of this message) that running is a risk.  That is, viewers who watched the broadcast of Chicago and who were NOT runners would be left under no illusions that attempting to run a marathon is a dangerous task.  The "shock and fear" coverage, which implies danger at every turn, sends a clear message that if you run a marathon, you are taking a chance with your life.

And this unfortunate, because it ignores the whole other side of the argument, and does so with little to back it up other than infrequent and over-hyped incidents.  A thoughtful, balanced approach would cover two additional aspects:

1. It would consider whether the risk of death during running is in fact greater than during any other activities, and;
2. It would look at whether the average  runner (from recreational to the marathon) was deriving a benefit from running, and whether this person was in fact less likely to die than someone who chose to stay on the couch because of all these "life-threatening" risks.

Millions of hours invested, but even stats don't tell the full story

Then there is the statistical approach, which many resort to in cases like this.  I read in a report from Fox News that a total of 425,000 runners completed marathons in the USA in 2008, and another 715,000 completed half-marathons.

If you convert that to time, assuming that the average marathon and half-marathon time is 4 hours and 2 hours, respectively, then you can work out that a total of 3.1 million hours of running time goes into those races.  And this does not include the training, or the 5km and 10km races done along the way.  If you assume that the average person trains 2.5 hours a week for 3 months to run a marathon or half-marathon race, then you get a grand total of 34.2 million hours of training time per year for those runners.  The total running time for marathon and half-marathon runners in the USA per year?  37.2 million hours of running (and this is an underestimate, I must point out - it does not take into account the millions who spend an hour a week jogging in the gyms, or those who train but don't race)

So what is the frequency of mortality for these runners?  Fox News reports that about 6 deaths per year occur during races.  How many during training?  We don't know, unfortunately.  But the point I'm trying to make is that these deaths are rather less common than they may seem - one per million hours, perhaps?  One per three million hours?  Until that is quantified, reports that marathon running is dangerous are simply irresponsible, the result of a classic 'media-led knee-jerk reaction', where news reporting makes us over-estimate the prevalence of such events.  A classic example is shark attacks - they are exceedingly rare, but when they happen, they're so dramatic that they receive hyped-up media exposure and so we think they're more common than they are.  I suspect the same is true for running-related deaths.  (What would be great is to compare this number with other activities - driving your car, flying, playing other sports.  If there are any economists or actuaries out there who know this, please speak up!)

The real story - the benefit that the media don't report

But these stats don't tell the whole story anyway.  What you really need to ask is whether exercise adds up to a longer, healthier life, even taking into account what I believe is a tiny risk.  In other words, you need to look at the overall benefit of being active, and ask whether those who run are less likely to die than those who do not?  There is no doubt, based on the evidence, that exercise reduces the risk of morbidity (disease) and mortality (death).  One of the most famous names in exercise science and health is Ralph Paffenbarger, and he demonstrated pretty clearly that increasing exercise was associated with decreased risk of disease and death.  The most famous study is perhaps this one, his Harvard Alumni paper.

Paffenbarger went so far as to show that people who exercised AND smoked, were less at risk than those who didn't smoke, but didn't exercise either.  So, if you want a debate about the benefits of exercise (and I include running here), the real issue is whether those three deaths, and then dozen or so that seem to happen each year during running, outweigh the fact that those same people, if inactive, would have a lower life expectancy and health status?  I doubt it does.

And I wish that the NBC, and all the other media covering running events here in the US and the rest of the world, would acknowledge that instead of focusing on the small risk of injury or death, there is a far bigger positive outcome to being active.  Maybe in future, doctors like George Chiampas will be explaining why those sitting on their couches SHOULD be getting up to run, rather than telling those who are running how not to hurt themselves doing it!

Fitness does not protect you, but nor does being under-trained increase your risk

One final point I have to make, in response to what I've seen is being discussed about this issue, is that people are not necessarily more likely to die from a cardiac event during exercise if they are untrained.  A lot of people have said that people who die during marathons are themselves responsible, because they're running when they are not fit enough.  This is not true, to the best of my knowledge.

The reality is that people who die during exercise have some underlying, probably undetected condition that predisposes them to a cardiac event during exercise.  Those who are simply unfit don't die - they just stop at the 10 mile mark (or sooner) and walk the rest of the way, because their brain does not allow them to continue running.  The fact of the matter is that there are conditions that predispose us to sudden cardiac death, and exercise can bring this out - but it could happen to the elite (Ryan Shay, a few soccer players in recent years) or to the average runner.  It's not that they're unfit or undertrained.

Of course, behaviours contribute to some deaths - overdrinking, for example, can lead to hyponatremia and death.  But even here, the criticism belongs with those who advocate excessive drinking, the dangers of "dehydration" and advertise sports drinks to unknowing consumers, not to the athlete who makes the mistake.

So in the light of the latest events, and until toxicology reports are in, deciding on the cause is premature.  Agreeing that it's sad for all involved, but recognizing that it's not running that killed them, is the way to go!

Ross

Semenya's performance advantage: An irrelevant question?

Caster Semenya's potential performance advantage may be a non-factor as medical consideration takes over

As mentioned in my tennis post below, I had a quick thought to share on Caster Semenya and the discussion around whether she has a performance advantage and should be allowed to run, assuming the reports of internal testes are correct.

A lot of the discussion revolves around whether Semenya will be banned. Politicians and officials have threatened World War III if this happens, and vowed that Semenya will continue to run regardless of her condition. Her supporters are saying that she should be allowed to run no matter what, while others are saying she should not run if she a enjoys a performance advantage as a result of the condition.

The reality is that there may never even need to be a decision, and any controversy around the issue may well be dealt with as a result of medical concerns taking precedence over performance concerns.

Having initially written this post on Saturday 12 Sep, I've learned a bit more, courtesy colleagues in pathology and from your comments, and so I've edited this post to improve its accuracy. Thanks as always for your time and comments!

The IAAF Decision: Performance advantage vs Semenya's decision: Medical

The issue of what the IAAF should do regarding Semenya's participation in sport may very well be completely irrelevant. That's because, if the reports are true, and she has internal testes, then SHE would almost certainly have to seek medical treatment.

In cases like this, three options options often exist

1. Surgical removal of the testes, which is likely the recommended option. According to Alice Dreger, an expert on intersex conditions, "Women with testes are at risk of testicular cancer. So doctors typically recommend having them taken out and having women take hormone replacement therapy (to retain bone health)". Thanks to Amby for that comment, as well.
   
2. Hormonal treatment and gender re-assignment. However, according to Dr Pete, a commenter in the post, this is very unlikely in the current scenario. It would require the correct internal anatomy and according to experts I've spoken to, is quite unlikely. Also, the testes would need to be removed anyway.
3. Do nothing. It is still possible Semenya chooses to do nothing (against medical advice). This is risky, because the danger of malignancy and cancer is substantially higher. Also, it's more difficult to detect with internal testes, and so she'd need careful monitoring. Once again, from Alice Dreger: "But one option is leaving them in and using watchful waiting so far as cancer risk is concerned, and more and more women with AIS feel that is a reasonable option"
   

Of the three, I'd say 1 and 3 remain on the table.

So why might this make the argument over performance advantages and the IAAF irrelevant? Because this situation has by now become a HEALTH issue first, and a performance one second. If Semenya has surgery, then the source of the potential advantage - the testes and the testosterone - will no longer be present and she can compete without any question (obviously, provided the issue is cleared up, as for the IAAF policy on sex reassignment). The necessary medical intervention may eliminate any debate over whether she has complete Androgen Insensitivity Syndrome or a partial AIS, and how much the testosterone might be helping her.

So rather than ask what the IAAF will do about her performance advantage, one should perhaps be asking whether the medical treatment SHE seeks is going to affect performance, and whether that medical treatment might negate the responsibility of the IAAF to make a decision at all.

Of course, it's possible that she chooses to do nothing, and then the ball is in the IAAF court once again, and they'd have to look at performance advantage. I'll look at that in the future, for sure.

But here are the two scenarios:

She goes for surgery, has the testes removed. 2010 will bring one of two results:

1. She runs just as fast as in 2009, but should then not be questioned, since the "advantage" is no longer present.
2. She slows down, but should still not be doubted. Either way, there is no issue of a 'ban' because of a performance advantage.

In this case, the Minister of Sport, ASA and everyone else 'threatening' the IAAF don't ever have to carry out their threats. In fact, the only way they would be able to stand their ground and occupy their current position is if they refuse to allow her to seek medical advice for a potentially life-threatening condition.

Meanwhile, those saying she should not run because of an advantage need not worry about the advantage. The medical concerns may well negate all the controversy.

Ross

Cardiac events during sport on TV

The dangers of WATCHING elite sport - health checks needed!

If you're reading this (or are a regular reader), then you're probably also inclined to spend fairly large periods of time actually watching sport (and wondering where we've been lately, but that's another story).

Being sports fans, you probably make it a point to follow coverage of your teams whenever possible, and live and share in the emotions of the game. People follow sport differently, of course - some dress up in the playing kit, scream at television sets and referees, and feel more anxiety and stress than the players they are supporting. Others (and I'm in this group) tend to be more dispassionate and 'cool', watching with a more analytical eye.

Uncertainty and enjoyment

Regardless, the enjoyment comes largely from the uncertainty. In marketing terms, sport on television is classified as an "instantly perishable product", which is to say that the value of sport perishes instantly once the outcome is known. Few will watch a game with emotion and enjoyment if the result is known, though of course, there are other reasons to watch matches over and over (game analysis, for example).

But what if that uncertainty is also the cause of medical problems? I have no doubt that those of you who fall into the first group - the screamers who live and breathe every moment - have been told to calm down or you'll damage your health.

Well, it turns out that this may be true! A study published in 2008 in the New England Journal of Medicine (very prestigious) looked at the incidence of cardiac events in Germany during the 2006 Football World Cup, and found that spectators are almost four times more likely to suffer cardiac events when their team played, and particularly, when they played very close, high-stakes matches.

The reason this is topical, of course, is that my country, South Africa, is gearing up for the 2010 FIFA World Cup, and is currently hosting the Confederations Cup (though I must say, when we play, the uncertainty in the outcome is perhaps not as great...!). We're also hosting the British and Irish Lions rugby team (a team picked every 4 years from the best of England, Scotland, Ireland and Wales). Yesterday was the first test, and it probably gave a few people cause for some cardiac events....!

The study - a spike during matches

The study was done from Munich, during the World Cup in Germany, and it tracked the number of cardiac events reported during German matches, during the World Cup when Germany did not play, and during a control period that was made up of about 4 months in the years before and after the 2006 World Cup.

The graph below shows the spikes that occurred when Germany played, indicated by numbers on the red line. The blue and yellow lines represent the control periods of 2003 and 2005.

In particular, games 5 and 6 are the ones of interest - those were knock-out matches where Germany first defeated Argentina in a penalty shoot-out (Game 5 - huge tension for fans), and when Germany were defeated by Italy in the semi-final (Game 6). More than 60 cardiac events per day were reported, compared to the average of about 15 per day! (Match 2, by the way, was a group game between Germany and Poland - the stakes in that game are high because it's something of a local derby, with some animosity between the teams)


Once losing that semi-final, Germany played Portugal in the 3rd-4th play-off, and you'll see how there was no spike, which confirms that the 3rd-4th play-off lacks any tension or interest! The final (not involving Germany) produced more cardiac events than this game.

This was of course the final where Zidane infamously head-butted Italy's Marco Materazzi - this was an event that probably produced its fair share of cardiac events back in France...!

Breaking the numbers down a little further, the graph below shows the number of cardiac events reported during the three stages, separated into men and women's totals. The average number of cardiac events during German matches was 43 per day, compared to only 14.6 per day during the control period (and 18.2 during the World Cup when Germany did not play - the die-hard football fans, perhaps).
Differences between men and women

Perhaps not surprisingly, the increase in cardiac events is much greater in men than in women, with an almost four-fold increase in the number of events for men during German matches, compared to a two-fold increase for women.

This is further shown by the graph below, which shows the calculated incidence ratio of cardiac events for men (in blue) and women (in magenta) during German matches, during the World Cup when Germany does NOT play, and during the control period.

Just to explain, the incidence ratio is worked out on the basis that the chance of a cardiac event during the control period is equal to 1. For example, if there were 20 cardiac events a day during the control period, and 40 during matches, then the incidence ratio would be equal to 2 - effectively, you are twice as likely to have a cardiac event during a match. In this particular study, the calculation is complicated a little by the fact that the researchers adjusted the incidence for environmental factors such as barometric pressure (which is why you won't quite get the same values as these if you do the calculation yourself).

So the graph above shows that men are 3.26 times more likely to have a cardiac event during a German match than on another day, whereas women are only 1.82 times more likely. My first reaction is that this is pretty easy to explain - men tend to follow the game more and experience the stresses that would trigger heart attacks more than women (a generalization, certainly). However, there are a couple of other possibilities - one is that men have pathophysiological differences that make them more vulnerable to heart attack, or that they are more vulnerable to emotional triggers. I'd still suggest that TV viewership stats will reflect that men are perhaps 4 times more likely to be watching the game than women, which would explain the finding almost entirely.

The point is - preventative measures needed

So the point of all this is not simply to tell a story about an interesting scientific observation. It has some very serious implications. The spike caused by live sport (and there is no reason to think this is unique to soccer, though of course a World Cup is likely to produce the greatest spikes) is significant, and something needs to be done, quite literally, to save lives.

The authors suggested options such as taking or changing the dose of beta-blockers (drugs that block the stress response and potentially protect the heart), drugs including anti-inflammatories, anti-platelet drugs like aspirin, and behavioral therapy to counsel fans on how to cope with stress. One observation that is significant is that almost 50% of those who had cardiac events were diagnosed as having coronary artery disease BEFORE the heart attack, and so simply pre-screening will identify people most at risk, and they can then be counselled or treated to further reduce the risk.

So without wishing to throw a wet blanket on your baseball/rugby/soccer/cricket watching activities, try to reign in the stress - it might be life-saving. And it's just sport, after all!

Ross

Cyclist dies in sleep

Belgian cyclist dies in sleep during Tour of Qatar

Sad news from the world of professional sports today is that a young Belgian cyclist, Frederiek Nolf, has died during his sleep between the fourth and fifth stages of the Tour of Qatar, currently underway.

Nolf, aged only 21 (and five days from his 22nd birthday), was a member of the Topsport Vlaanderen-Mercator team, which has now pulled out of the event, with the day's stage being shortened and neutralised to an uncontested 40km ride.

Cause of death speculation

Sadly, for cycling, the speculation has already begun that this is drug-related death, partly because of the reputation of the sport and the historical precedent for this type of event among cyclists. At this early stage, the ASO (the Tour's organizers) couldn't even confirm the death, and so discussing a cause is very, very premature.

However, a few people emailed me the story this morning with the very obvious implication that this was yet another in a long series of sudden deaths in fit and healthy athletes. In the 1990s, there was a spate of sudden deaths, at least a dozen, where fit amateur and professional cyclists died in their sleep. That negative publicity was at least part of the reason for the clamping down on EPO use, which was rampant at the time.

It brings to mind one of the most fascinating quotes I've ever come across in a cycling book - it was in the book "The death of Marco Pantani" by Matt Rendell, in which a story is recounted of how in the 1990's, with EPO use rampant, the cyclists would set their heart rate monitors to sound an alarm if their heart rate dropped below a certain level. On hearing the alarm, the cyclists would have to wake up, get the bike out and spend 10 minutes on the rollers, in their hotel rooms, just to jump start the circulation.

In the words of one cyclist: "During the day we live to ride, and at night, we ride to stay alive". Quite chilling, and I must confess that these were the first thoughts that went through my head upon reading of the death of Nolf.

However, and this is very important, such speculation doesn't provide answers, only more questions. There are some other reasons why cyclists might be predisposed to sudden death - riding at high intensities when carrying viral infections (as pro athletes tend to do) is one of them. And, as Ryan Shay, and a number of other high profile cases have shown recently, sudden death is a tragic, but not completely uncommon event. There are reports that Nolf's cardiogram was normal, but even that is not a guarantee of health, because those tests can often miss the quite rare conditions that cause sudden death in athletes.

So let's see what unfolds, and whether any answers emerge. In the meantime, a sad day for cycling and those who knew Nolf.

Ross

Chicago Marathon 2008

The data do not lie: The actual environmental conditions from the course

Apologies for the absence lately, it has been a hectic time at work and for other endeavors lately, but our deadlines have now passed and we can return to a more regular posting routine that we are accustomed to. Just in time, too, as the NYC Marathon is just over two weeks away, so watch for our previews of that one as Paul Tergat and Paula Radcliffe try to add to their previous victories in that race.

But for now let's look back to the Chicago Marathon, where much was said about the weather conditions on the day. All the fuss was due to last year's oppressive conditions which forced the organizers to close the course early and send people back to the finish. It was a cooking day in Chitown last year, to be sure, but this year it was a stunning day---and we have the data to prove it!

The historical record

A look at the past three runnings of the race reveal three vastly different days. In 2006 it was a miserable day---cold, in the 30s or 40s F, if I recall, and overcast the entire time. Generally a dreadful day to run a marathon! 2007 was quite literally burned into our memories - it was already in the 70s F at the start, with no wind, and glaring sun that baked an already hot city into the 90s F by day's end.

This year was cooler at the start, and much less humid as the day went on, producing a warm but dry day. Here is how the conditions stacked up from last year and this year, according to the data from the weather website Weather Underground:

These graphs show the "official" historical data on the Weather Underground site. Temperature data are on top, while relative humidity data are at the bottom. We took values from the same station, so there is no bias in that sense. The big difference is the starting temperature---it was over 10 F lower this year, and so even though the humidity was similar at the start I can tell you it was a vastly different day. And from 11:00 the humidity was consistently 10% lower than last year.

This year's weather was something runners know about. It was one of those days where you step outside in your running kit and think, "Hmmm. . .maybe I should bring a long-sleeved shirt with me to the start because I might get cold standing around before the gun." Last year, on the other hand, was muggy, hot, and oppressive. The preceding month was unusually warm for fall in Chicago, and every morning was hot and humid even before the sun came up. You never felt cool last year in September during your morning run or ride, I can tell you that much.

The "official" vs. the "actual"

But the official data tell only half the story, and after last year the race organizers knew they needed something more to inform them about the conditions on the course. The problem last year was that around 11:00 it was clear to the officials that they were going to have problems if they kept the course open as their "peripheral" resources, i.e. ambulances on the course, were all deployed and transporting runners to local hospitals. Therefore it was the best decision they could have made to close the course, because had anything else happened they would not have been able to respond to it.

Part of the solution was to invest in technology and purchase four portable devices to measure the temperature and relative humidity on the course, rather than relying on the data from weather stations. We placed these devices (together with faithful graduate students!) at strategic points on the course, namely the northern-most, western-most, and southern-most points and the finish area. Then we took readings every 15 min, although for simplicity we have included only hourly measurements here:

Again, temperature data is on top and humidity data at the bottom.

The first noticeable detail is the the readings we took on the course are quite different from the "official" data. This might not be a surprise as that weather station is likely distant to the race course, and weather is a very local phenomena. But still, as far as we know this is the first this this kind of discrepancy has been shown, and the important implication is that if you organize an event and want to know what is happening on your course, you must collect the data yourself and analyze in real time to see how things are changing and exactly what is happening.

During portions of the race the difference between the "official" values and the data we measured was as much as 40% for the humidity and 11 F for the temperature. In addition, the difference between the northern-most station, located near mile eight, and the finish was 6-7 F. The reason is probably because that part of Chicago, the neighborhood of Lakeview, consists of heavily shaded narrow streets. Compared that to the finish in Grant Park, which is totally exposed to the sun, especially for the first half of the day as it is eastern border is Lake Michigan.

So based on the data, one has to ask, "Why not run the course in the opposite direction?" After all, temps in Lakeview were 5 F lower when we stopped collecting data at 11:00 there! Of course we did not measure into the afternoon, and by then the temps on the northside might have been similar to the finish. But this is a good example of how science and data can drive critical decisions that might improve future events.

Was the weather a factor?

This question is being debated in the comments section for the race report, and we have people weighing in on both sides. Was it hot? Yes, it was, and the air temperature was close to what it was last year, in fact. The humidity was much lower, though, and the real difference was probably the starting temperature and the fact that the weeks prior to the race this year were generally much cooler. Overnight lows have been solidly in the 50s F since the beginning of September, and so the city never really heated up like it did last year.

The conditions were far from "ideal," but then again they were not dreadful by any stretch. It was a stunning day in Chicago, and normally wuhen the environmental conditions are considered "hot," it shows in the winning time. Evans Cheruiyot's 2:06:25 was incredibly fast, and not indicative of a winning time in "hot" conditions. That said, the conditions were not ideal for world record-type performances. On the day, in 'real-time', we wrote somewhat arbitrarily that the elites were probably slowed by about a minute as a result of the temperature, which seems reasonable, even now.

The early pace in the elite race was too fast, given the conditions. They paid for it in the second half, with the exception of Cheruiyot (who did also slow down, it has to be said), and large time gaps were the result of the super fast early pace, combined with the conditions. However, for the vast majority of the field, the conditions were not harmful, and the athletes running anything slower than...oh, about 2:08, were never, ever in danger of heating up too much, or becoming critically dehydrated.

The medical tent

I was sitting at the entrance to the medical tent, and in time we will analyze the data regarding symptoms, number of admissions, time to discharge, etc. One anecdote I can share now, though, is about a runner who must have run about a 3:15 or so, judging by what time he came to the tent. He was on the back of one of the golf carts used to get collapsed runners from the finish to the tent, and was sitting up with a Gatorade cup in his hand. As he passed us, he recoiled and spewed what must have been a beaker full of vomit. That in itself was not remarkable, but the volume was---the poor guy must have puked 500+ mL of Gatorade/water! Yet there he was, trying to drink MORE, probably because he'd been told he felt so terrible as a result of dehydration! Dehydrated, with maybe a liter of fluid sitting in his stomach... if something doesn't strike you as being "wrong" with that picture, then nothing will He had no business with that kind of volume in his stomach, and in case you missed it last year you should read our series on dehydration and fluid intake. Just click the "Featured Series" tab above for the links.

In the meantime feel free to weigh in, especially if you ran the race, and watch for more data from the medical tent as we analyze that!

Jonathan

Running injuries expanded

Expanding on running injuries (and some admin)

Yesterday, Jonathan did a post looking at running injuries and specifically the common training error made by runners who tend to move from one injury to the next in their training! He raised the the guideline that a 10% increase in distance from one week to the next is probably about the limit of what most people can aim for before they start running (literally) into injury territory.

And the post got some pretty good comments and discussion going, and it struck me that the whole concept of injuries in runners (and in other sports, cycling and swimming especially, since our focus is on endurance) is a topic that we have never really tackled here.

And since it's so prevalent - studies suggest that about 2 in 3 runners will be injured every year - it seems like a topic worth delving into in a bit more detail in the coming months!

Of course, it's a vast, enormous topic, and much like our Fatigue Series, it's probably too big to be discussed adequately in a nice, packaged series of three or four posts. So rather than introduce it as a series, I think I'll put forward that we will start giving a lot more thought to some posts that follow on from yesterday's post and the resultant suggestions, and then roll those posts out a little less frequently than we would in a dedicated series. But just be assured, it's on the radar screen!

So just a couple of ideas around injuries in running:

1) Running technique and injury

First, a couple of people raised the issue of running technique and injuries, which is a pretty common thought these days. I honestly don't believe that running technique, at least in the form that it's been "packaged" and then sold to runners, has a great deal of importance for injuries. I'd go with the theory that if a runner is injured, look first at training, second at training, third at training, fourth at strength and flexibility imbalances, and fifth at training. Maybe at number six, you can consider running technique.

All this is obviously within reason, and as one reader (Cassio) pointed out, there are obvious technique related things that can easily be addressed, like very obvious overstriding. So sure, in that case. But the case that is made for subtle changes is really overdone and overmarketed, in our opinion.

The issue of technique is however one that we have covered in great detail, and so this is not a debate we need to have right now - it's been had! You can read our series on running technique here for all the discussion of those ideas.

2. The inter-relatedness of it all

Of course, at this point, we must make a very very (very) important point. Nothing in your running (or cycling or any sport) can ever be looked at in perfect isolation. In otherwords, training may well be the cause of most injuries, as we've said, but there is a substantial interaction between the training you do and other variables which act externally to affect your unique response to that training. A 55 kg Kenyan might go from no running to 120 km in a matter of months, and be racing competitively in less time than that. Another person will be bed-ridden in weeks with stress fractures! Why? Because their unique physiology, anatomy and response to training means that "not all training is created equal".

So I am firmly of the belief that if correct training principles are adhered to, then any athlete can train without injury - the level they reach and their success as a runner is of course dependent on numerous other factors. But the problem that we land ourselves in is that we "train by numbers", and try to fit all athletes into the same mould. So the concept that training is simply run from a template doesn't work, precisely because we are not all average.

So the truth is, training might make up the first three areas of concern for an injured athlete (in my opinion), but you can't look at the athlete's training without considering things like flexibility and strength balance (as Sean has pointed out) because they MODERATE the athlete's response to training. That's why I'm in agreement that the athlete must address strength, flexibility and balance.

Now, if we want things to get really tricky, then we start talking about flexibility - can you be TOO flexible? I think when asked in that way, the answer is quite obviously "Yes". But what if it's asked a little differently: Should runners be stretching? Because now all of a sudden, the answer is "Maybe". And once again, we have a case where "one size does NOT fit all". There is, in other words, evidence that stretching can CAUSE injury, not prevent it. And excessive strength too. The key then is balance, and that's a topic worth getting into in the future as well

3. The influence of intensity - critical

Then lastly, the other variable in your training programme is the intensity. Yesterday, Jonathan touched primarily on VOLUME, and raised that guideline (not a rule, remember) that 10% increases are usually the limit. What that doesn't deal with is intensity, so we have to discuss the impact of increasing intensity.

What often happens is that a runner will very patiently and methodically build up VOLUME, because it's much easier to measure - time or distance. What they neglect, and it's more difficult to quantify, is intensity. Because my experience, and theory, suggests that a 5% increase in intensity is NOT the same as a 5% increase in volume.

In other words, if you increase the intensity very slightly, the volume has to drop quite a lot more in order to keep the OVERALL load the same. And so what often catches runners out is that they ramp up the volume by 5 to 10%, but the intensity goes up by 5% too, as they get fitter, or push a little harder. The net result is that the overall training quality increases too much, and they break down.

This is also why the biggest danger period for any runner is that moment when they start to add in the high intensity training to the programme. They finish base training, and suddenly start to do the odd track workout, some fartleks, or the like. But if they don't manage a reduction in volume, the combined effect can be damaging.

So that's another topic worth discussing

One final point - no research available

One thing that we must make clear right up front, is that as we tackle this topic on and off over the coming months, there is very little scientific evidence on this, and so we rely instead on theoretical insights, experience and "bald assertions". Studies often look backwards at injury, and work out after the fact that X, Y and Z are the likely predictors for injury. For example, we know that if you've had a previous hamstring injury, then you have a many-fold greater chance of a hamstring injury! (hardly rocket science...)

But scientific studies that look at the long term effects of different volumes and intensities of training are, for many reasons, just about impossible to do effectively, so it's looking backwards that reveals the evidence.

But, that's no reason not to discuss it, and we'll welcome any comment or feedback. So keep an eye out for those injury posts!

Ross

Gebrselassie out of the Olympics

Haile Gebrselassie OUT of the Beijing Olympics - the air pollution is a "threat" to his health

Dramatic news being reported today by news sources is that Haile Gebrselassie, Ethiopia’s marathon world record holder and multiple world and Olympic champion has withdrawn from the Olympic Marathon in Beijing, citing concerns over the air pollution as the reason!

Gebrselassie had previously mentioned the possibility that he might not run in Beijing, but today’s news represents a definitive ("99% sure", apparently) decision. Gebrselassie is quoted as saying the following:

"The pollution in China is a threat to my health and it would be difficult for me to run 42km in my current condition,"

“My current condition”, incidentally, refers to Gebrselassie’s asthma, which he says forced him out of the London Marathon in 2007.

How bad is Beijing? And is this a justified decision?

It is a radical decision to take, particularly with all of 150 days to go before the Olympic Games. Yes, there are concerns over the pollution, and yes, it's likely that conditions will be difficult in Beijing, heat and humidity adding to the problems. We won't go into huge detail on air pollution and exercise performance now, since we've looked at the pollution situation in Beijing in two previous posts.

First, we discussed the likely problems the athletes will encounter in Beijing, and how some nations are planning to send athletes to locations OUTSIDE Beijing to avoid the pollution. That was amidst claims and promises that Beijing was doing all it could to improve the pollution situation.

However, a few months later, it was being reported that the air pollution situation in Beijing was actually getting worse, with many of the promises about cleaning the air (including the closure of factories in Beijing) being forgotten or ignored in the face of economic pressure to keep factories open. It has been a problem that has plagued the build-up to Beijing since last year, and this is the most dramatic story arising out of the pollution controversy so far.

A premature decision?

But rather than make this decision now, why not wait out the next three or four months and see how things develop? Consult with an expert or two (because this is an issue where you'd get a sixth and seventh opinion IF you really wanted it) on asthma. Find experts on pollution, as Paula Radcliffe did, and see whether there is a contingency plan that might allow you to run and challenge for what is really the only major title or accolade you're still missing?

The British Olympic team even announced that they would provide masks to their help their athletes breathe more easily if required. Perhaps Gebrselassie has done all this, and the advice he received is that there is no way he'll be able to run in Beijing. It's still almost unbelievable that he wouldn't wait out a month or two before announcing a decision that, in the words of his manager Jos Hermens, is "99% sure".

For the reality is that Gebrselassie has achieved pretty much all he can in international running, apart from winning the Olympic Gold in the marathon. It's a goal he himself has expressed on many occasions and it really does seem peculiar to me that he could so easily let go of the goal.

Instead, his manager Hermens is quoted as saying:

"He doesn't want to put his career in danger and he still wants to run at the 2012 Olympics in London. His dream is to run in two hours and three minutes and to be the first to do that. It's more important for him than to win another gold medal."

The pollution - an unknown quantity

Quite what the long term implication for his health is is difficult to know - certainly, his career would hardly seem in danger if he raced in Beijing. His marathon race, yes, but to suggest that his long term health would be affected is a little extreme. The worst that would happen would be that he could not breathe, and so he'd stop and pull out of the race within the first 10km, and live to fight another day - there's no reason to believe that his 2012 race is at stake thanks to the Beijing air of 2008.

Then again, I'm not sure that elite athletes have ever been exposed to the kind of pollution they'll encounter in Beijing, so the Olympics will be interesting simply from that point of view. Perhaps Gebrselassie tried to jog on a recent trip to Beijing, and found that he simply could not breathe - his mind may have been made up by his lungs!

However, it would seem to be a question of priorities, which is a deviation from the usual line given by athletes (including Gebrselassie) that the medals are more important than the records. Of course, it's Gebrselassie's choice, and good luck to him going for that 2:03 marathon (that is another issue altogether - we've discussed the chances of a 2:03 before). But it certainly is a shame, and hopefully, that 1% chance will still come into play and we'll see Gebrselassie on the roads, rather than the track, in Beijing.

If not, then it's the 10,000m event, as Gebrselassie has announced his intention is to qualify for Ethiopia's team for the 10,000m race in Beijing. This might be part of the reason for such an early announcement - perhaps he felt he needed to make the decision this early to allow him to adjust the training leading into the European summer. However, even that doesn't quite ring true, and I can't help but wonder whether the decision is really as simple as saying that he has other goals, and he is concerned over his health...is there any chance that in two months' time, Gebrselassie will announce that he's changed his mind and WILL in fact run the marathon in Beijing? It would not be the first time that he'd announced his "absence" from a major championships, only to be "persuaded" to go after all...

Suspicions and questions - a valid reason?

Such is the climate around international sport these days, that there is already lively debate and cynicism about the given reason. Does Gebrselassie really have asthma? Or is this an excuse not to be tested by drug control authorities? The problem with that "conspiracy theory" is that Gebrselassie has announced that he'll try to run the 10,000m race in Beijing instead, where he'd be tested anyway. So scratch that theory off the list.

There's actually a great deal of controversy around the drug testing issue and asthmatics, incidentally - for example, if you take an average sample of people and compare it to a sample of Olympic athletes, you find that often, the Olympic group will have a much higher incidence of "asthmatics" - if , that is, you choose to believe all the medical clearances that are issued giving them exemption to use inhalers (which are otherwise banned). But again, the fact that Gebrselassie is not pulling out of the Olympics, but just the Marathon, would suggest that the drug theory is slightly misplaced, on this occasion anyway.

The Olympic Marathon without Gebrselassie

As for where this leaves the marathon, well, it's dramatically weakened by his absence. His anticipated race against the Kenyans, whoever they chose, was due to be a real highlight of the Beijing Games. The marathon will be somewhat lacking its lustre if indeed he doesn't change his mind. So a real shame for the Olympic Games, and let's hope that it's a premature decision and that he announces that he will, after all, take his place in the race come August.

Ross

Related articles

Air Pollution in Beijing: Symptoms and issues facing athletes in Beijing

Olympic events in danger: Athletes will need masks in Beijing

Ryan Shay Autopsy

Ryan Shay Autopsy: Why the delay?

In the last 4 months, everyone has waited patiently for the autopsy results of US runner Ryan Shay to be released. It was in November last year, during the US Men's Olympic Trials, that Shay collapsed at the 10km mark in Central Park, New York. He was later pronounced dead, and the story shocked the athletics world.

We have now reached March, and still no final report on the cause of death or the results from the autopsy which is performed on all sudden deaths in apparently healthy people. For example, earlier this year, actor Heath Ledger died in mysterious circumstances and an autospy report was released only two weeks later.

So not surprisingly, the voice of those who wanted to know some answers was growing steadily louder or discontented. Apparently, the Medical Director of the race was receiving 25 calls a day from various people. Even here on this site, we've received a number of questions from people asking whether we knew - of course, we are as much in the dark as anyone else. But now, it seems there may be some answers...

Runners World finds some answers

On Thursday this week, Amby Burfoot wrote an article which you can read here, detailing some of the progress made so far.

According to the article (summary for those who don't want to read the whole thing), the Medical Examiner's Office refuses to comment on any case, which is understandable, if not doubly frustrating for those wanting to know. The official word out of the Medical Examiner's office is:

"Every case is individual, and we have to do a complete job on every case that we do. We do the testing that we need until we're satisfied that we can determine the cause of death."

Apparently the four month wait for the report is not completely exceptional - it usually gets released far sooner, but four months still falls inside what the Office considers an acceptable time frame. Final testing is apparently now taking place, and according to the spokesperson, "It should be very soon now."

So within the next week or two, perhaps, we'll have some conclusive (hopefully) answers as to what would cause an apparently healthy and very fit 27 year old to collapse and die during an activity he did just about every day.

But there are some answers, provided by Ryan Shay's father, Joe. In a telephone conversation with Runners World, Shay revealed that:

A toxicology report had been conducted on the supplements Shay was using - he was sponsored by the company EAS, and so any possible contamination was investigated. Apparently, Joe Shay requested that the toxicology report be released before the rest of the results, but the Medical Examiner's Office refused, as policy is to release the report in its entireity. The toxicology report became the focus of attention because at the time, many people wondered whether drug use might have been responsible for Shay's death.

A second part of the investigation was done on tissue samples which were genetically examined. Shay's family specifically requested this to make sure that no other family members were in any danger of a similar cardiac event. Joe Shay revealed to Runners World that this testing showed that Shay DID NOT have hypertrophic cardiomyopathy, which was a widely reported candidate for the cause of death (including here).

So one possible cause has been eliminated, the others remain possibilities. The signs are encouraging that within two weeks, a report will be released, which will hopefully provide some answers. If and when that report is released, we'll do our best to bring to you.

Ross

Computer Games continued

First Post of 2008 - a New Epidemic in children: Playstation thumb!

First of all, a happy and prosperous New Year to everyone! We hope that 2008, an Olympic Year, brings everyone some Olympian success and prosperity!

I trust that all are recovered from their New Year celebrations, perhaps you've even jotted down some resolutions for 2008? Here's to making them last at least a week!

Just a short filler post today, to follow on what we have been discussing recently - health and computer games. A few days ago, we did some posts on the somewhat bizarre potential of Nintendo Wii to contribute to weight loss in children, since it is a more active form of computer game than Playstation and X-Box 360. A case of trying to gloss over a problem and justify inactivity perhaps? Or an admission that "If you can't beat them, join them"?

In any event, it reminded me of an article I came across a few years ago, while still a student. I used to share an office with three other PhD students who shared my sense of humour, and we all had a humorous appreciation for some of the more bizarre scientific research publications that our field sometimes produces (for example, check out this very bizarre case study from an Indian Medical Journal - accidental condom inhalation, anyone?).

Playstation thumb - a new epidemic in children

So here's one I came across in 2004 (don't remember how), detailing the emergence of a new "epidemic" - it's called Playstation Thumb. The condition was first mentioned in a letter written to a prestigious journal Lancet, and was followed by a synopsis in the South African Medical Journal. The condition develops due to (you guessed it) excessive use of the thumb during play - the problem is partly a dermatological one, with the formation of a blister, which can be accompanied by fatigue of the thumb. There is tendon pain (whether or not there is inflammation is debatable) which ultimately limits pain - a forced "rest" period...

In fact, there's a whole body of literature about this condition now. One of the more recent ones, in Archives of Dermatology, details "The Use of Dermoscopy to Visualize Punctate Hemorrhages and Onycholysis in "Playstation Thumb". (I don't know exactly what that means either...!)

Nintendo are not immune to this affliction. In June 2007 (last year, funnily enough!), the New England Journal of Medicine had a report detailing the condition "Wiitis". Here, a 29-year old medical student woke up with shoulder pain, had it checked out and was diagnosed with "acute tendonitis isolated to the right infraspinatus" as a result of playing too much Wii the day before! So forget Achilles tendonitis, tendinosis, ITB, patellofemoral pain and the like - computer gamers are just as injury-prone as all the runners and cyclists! Not to mention the risk of obesity, and the resultant disease - the games will one day carry a warning sticker!

But wait there's more - how about "Playstation Lip"?

If that wasn't enough, how about this letter, that was sent to the British Medical Journal in June 2000? It describes two dentist's experiences with children who apparently concentrate so hard that they damage their lower lips...

Sir, - It has come to our attention that an unusual consequence of children concentrating whilst playing their computer games of PlayStation games appears to be that of trauma to the lower lips.

We have recently seen two children who have attended Newcastle Dental Hospital children's department with severe trauma to their lower lips. On questioning it was clear that this trauma had occurred whilst playing on their PlayStations and consequently we found it necessary to provide them with lower soft splints to prevent any further damage.

Therefore, we would be very interested to know if any other readers had noticed this interesting phenomenon and had seen any other cases recently of what we have called 'PlayStation lip'.

R. L. M. Inglis
R. R. Welbury

It seems that we are on the verge of a new branch of science - computer games exercise science and medicine! First we had the possibility of studies on Wii Economy (see the comments section), now a division of medicine, even dentistry, on physical afflications caused by too much gaming! Who said that science stands still? And as for human evolution continuing to this day...

Preview of forthcoming posts

OK, so today was a bit of a tongue-in-cheek post to kick off the year. But tomorrow, I thought it would be interesting to do the "Nostradamus Post" and make some predictions for sport (and science) in 2008.

Hope you've hit 2008 running (or cycling, swimming, rowing, and figuratively!)

Ross

Muscle Cramps: Part II

The electrolyte depletion model of muscle cramps

In part one of this new series we tried to set the scene by providing some history in this area of muscle cramps. At times it might seem like we are a bit heavy on the historical side, but as we mentioned in one of our comments to Part I, understanding the historical record is crucial as often it helps us understand why we think what we do---and this affects one's interpretation of the science. In this post we will focus on the prevailing premise that dehydration and electrolyte disturbances cause muscle cramps.

The first important thing about this area of research is that Professor Martin Schwellnus is hands down the one researcher who has consistently moved this area forward. As a sports physician he has treated many a runner with cramps, and his curiosity and what he was seeing in the medical tents lead him to challenge this paradigm that dehydration and electrolyte problems cause cramps. What he found was that this model was based on not one shred of scientific data, and instead relied heavily on anecdotal evidence. Since 1997 he has published some of the only evidence available that has even attempted to determine what actually is causing the cramps and who is prone to this condition. The first paper he published in 1997 proposed a novel hypothesis for muscle cramps, but we will address that in Part III of this series.

The lab vs. the field

In our series on dehydration we discussed how the lab is not always translatable to the field, and vice versa, but that each has its own important role. Field studies are often cross sectional in nature, and although important we cannot assign direct cause and effect from them. However it is observations and findings from field studies that often lead to the very precise and mechanistic lab studies that are important in advancing our knowledge.

However one major obstacle in this area (cramping), is that no one has yet created a laboratory protocol in which we can reproduce muscle cramps in a controlled manner. Being able to do this is a crucial step in eventually identifying what causes them because it will allow us to make specific interventions to test what the effect is on cramps. So although we are still in the infancy of this area of research, the field studies are a very important starting point and have so far yielded important findings.

One study published in 1990 showed that there was no association between potassium levels and cramps. In that study cyclists rode for up to five hours. Some of the subjects did cramp, but their potassium levels were not uniformly high or low, thus showing no association between that variable and the cramps. However beyond that study (and one more that was presented at a conference but apparently not published) there is little real data out there to support or refute this hypothesis that dehydration or electrolyte disturbances cause cramps.

Study 1: Two Oceans Ultra Marathon

In a 2004 study published in the British Journal of Sports Medicine, Professor Schwellnus and his colleagues examined runners before and after the Two Oceans 56 km marathon in Cape Town. They measured quite a few variables, but since we are discussing changes in electrolytes and hydration, we will talk about those results. Remember that many people, both scientist and personal trainer alike, will profess that cramps are caused by dehydration and/or some disturbance in the electrolytes (sodium, potassium, magnesium, etc.) So the important finding from this 2004 study was that when the crampers were compared to the controls---who were matched for body mass and finishing time---the only differences were that the crampers had lower sodiums and higher magnesiums. The problem with this is that a lower sodium concentration suggests overhydration and not dehydration, and also if magnesium deficiency is meant to cause cramps then surely the crampers should have been lower here?

	Crampers (N = 21)	Controls (N = 22)
Sodium	139.8 ± 2.1	142.3 ± 2.1
Potassium	4.9 ± 0.6	4.7 ± 0.5
Magnesium	0.73 ± 0.1	0.67 ± 0.1
Osmolality	280 ± 6	284 ± 10

The relevance of this study is that if dehydration and electrolyte disturbances really play such a large role in cramps (as they are proposed to), then the crampers should have much higher electrolyte concentrations since they would be losing fluid and causing the concentrations to rise. Yet instead we see something entirely different, first that the crampers had lower sodium concentrations, and second that the crampers were not really different compared to the controls.

What is also noteworthy from this study was that the crampers had an average loss of body weight of 2.9%, compared to 3.6% for the non-cramping controls. In otherwords, the people who DID NOT cramp lost more weight than the people who did. It goes further than this, because Schwellnus et al were able to measure the change in plasma volume as well - a more direct measure for what is happening to fluids. Here, they found that the crampers actually gained a small amount of 0.2% during the race. The non-cramping control subjects LOST 0.7%. So the sum effect of this data is that it suggests very strongly that cramping is not associated with dehydration, or with lower serum electrolyte levels, which is what we have had drilled into us for many years!

The follow-up study from Iron Man - further evidence against serum electrolytes

The next year they published a study in Medicine and Science in Sports and Exercise, and instead of runners it was Ironman triathletes. According to what most of us hear day in and day out, it is these ultra-distance athletes who are exercising for 10+ hours at a time that must be most susceptible to dehydration and electrolyte deficiencies. After all, they are sweating for hours on end, and the numbers tell us that with so many liters of sweat lost then they must also be losing grams and grams of "essential electrolytes" such as sodium. Below you will see the basic data on these athletes, and the important finding here is that we see the crampers and controls were the same age and were similar in mass, had similar pre to post cahnges in mass, and also finished the Ironman in similar times:

	Crampers (N = 11)	Controls (N = 9)
Age (years)	33.5 ± 8.8	35.4 ± 8.1
Pre-race mass (kg)	79.1 ± 5.9	77.7 ± 6.4
Post race mass (kg)	76.3 ± 5.6	74.6 ± 6.5
Body mass loss (%)	3.4 ± 1.3	3.9 ± 2.0
Total race time (min)	660.8 ± 77.9	685.7 ± 48.5

So the two groups were essentially the same in that the crampers did not spend longer in the course or lose more weight (a crude measure of dehydration). Yet again the crampers and the controls looked remarkably similar on paper---except as in the 2004 study the crampers again had a statistically significant lower sodium concentration, and, we will repeat this, that suggests they were more hydrated compared to the controls. . .yet they were cramping. Here are the data from the electrolytes in the two groups:

	Crampers (N = 11)	Controls (N = 9)
Sodium	140 ± 2	143 ± 3
Potassium	4.4 ± 0.06	4.2 ± 0.5
Magnesium	0.9 ± 0.2	0.8 ± 0.1

Recall that what is most often put forward as the cause of cramps is either dehydration or some electrolyte disturbance, but the data from these two studies do not support that hypothesis. Although these are field studies and we cannot assign a cause and effect relationship, this available evidence suggests that these (normal) levels of dehydration do not appear to cause cramps. If these levels of dehydration did cause cramps and were largely responsible for cramps, then what we should see is a very high incidence of cramps in all of the race finishers with the same physiological characteristics as these subjects----or in other words, the vast majority of the race finishers.

Rejecting the old models

In science when the available evidence does not support the hypothesis, we must change the model. Based on this available evidence we see clearly that dehydration and electrolyte levels are not associated with muscle cramping during or after exercise, and therefore we must adopt a different model to explain what is causing them. We cannot just ignore the data we have shown here and keep on telling people that it is dehydration and electrolytes when new evidence suggests otherwise.

So in Part III of this short series we will lay out the newest hypothesis that tries to explain the "why" and the "how" of muscle cramps. It is novel and, as you might have guessed already, has nothing to do with electrolytes and dehydration! So come back and join us for Part III of this series, and then join us for the comments and debate!

See also:
Part I: Theories and fallacies of muscle cramps

References:
Brouns F et al., "Ammonia accumulation during highly intensive long-lasting cycling: individual observations." International Journal of Sports Medicine. 1990 May;11 Suppl 2:S78-84.

Schwellnus MP et al., "Aetiology of skeletal muscle 'cramps' during exercise: a novel hypothesis." Journal of Sports Sciences. 1997 Jun;15(3):277-85.

Schwellnus MP et al., "Serum electrolyte concentrations and hydration status are not associated with exercise associated muscle cramping (EAMC) in distance runners." British Journal of Sports Medicine. 2004 Aug;38(4):488-92.

Schwellnus MP. "Muscle cramping in the marathon : aetiology and risk factors." Sports Medicine. 2007;37(4-5):364-7

Sulzer NU et al., "Serum electrolytes in Ironman triathletes with exercise-associated muscle cramping." Medicine and Science in Sports and Exercise. 2005 Jul;37(7):1081-5.