Fatigue Series Part 5: Exercise in the heat

Anticipatory regulation of exercise in the heat: Discussion continues

About a week ago, in our last post of our Series on Fatigue, we looked in some detail at a study by Frank Marino which found that African runners paced themselves differently to White runners during 8km time-trials in hot, but not cool conditions. Part of this difference was likely the larger body size of the white runners, which meant that their rate of heat storage would be higher than the African runners' at the SAME SPEED. Therefore, the theory put forward was that the RATE OF HEAT STORAGE mediates a reduction in running speed well before any potentially limiting level of hyperthermia is reached.

A couple of things arose out of this post. First, we got quite a few posts by people saying that they should have controlled for body size, and made sure that the two groups were equally large (or small, as they case may be). This is probably correct, technically speaking, but a little harsh and maybe missing the point of the study. The key here was not so much the mechanism for the different pacing strategies of Africans and White runners, but rather the fact that they did it at all. Perhaps it's genetic, perhaps size-related, perhaps metabolic, perhaps related to running economy? That's all for future work to establish, hopefully. But the point is that athletes pace themselves differently and the rate of heat storage is a very likely candidate that mediates this difference.

One reader said that they should have controlled for calf-size as well, which is also probably true, but if you go down that road, then you have to control EVERYTHING. And physiology is simply too complex to do this. That is why, as you may recall, we discussed how for many years, scientists used to limit themselves to these fixed work rate trials to exhaustion - they are simpler to manage. As soon as you allow pacing, the complexity becomes enormous, but it's the only realistic way to assess how PHYSIOLOGY works in the field.

Today, we look at further studies that have attempted to assess this, but this time, with a possible mechanism. For that, I get to summarize my own study, which is a little self-indulgent. It was not intended in this way, but was rather the result of the fact that five or six years ago, nobody was doing this kind of work. Still today, there are some problems with it (again, the motto is "Nobody can PROVE anything"), but it's worth looking at.

Anticipatory regulation of performance in the heat

Refresh your memory on the state of the knowledge prior to 2003. The thinking regarding exercise in the heat was that you fatigued because you were hot. That is:

• Exercise increased heat production
• In hot and humid environments, you are not abe to lose that heat
• Your rate of heat storage is positive, so your body temperature rises
• It rises until it reaches a critical limiting level of about 40 degrees Celsius
• At that point, your brain fails to activate the muscle, your level of effort hits maximum, and you stop exercise

Impaired performance in the heat is thus the result of GETTING TOO HOT, to put it simply. This theory was borne out by studies that showed how brain activity was altered and EMG activity was lower when the body temperature was 40 degrees celsius. The problem was, these studies all fixed the cycling power output (or running speed), and so there was no room to slow down - it's either go or stop.

So, in 2002, I did a study in Cape Town that aimed to determine WHEN the decision is made to slow down or speed up, or, in the case of the existing theory, stop altogether?

This study, which was published in the European Journal of Physiology (Tucker et al. Eur J Physiol; 448: 422-430, 2004, for those interested), aimed to answer the following questions (in lay terms):

• During exercise in the heat, WHEN does the athlete slow down? The current thinking was that they slowed down BECAUSE they got too hot. But Marino and some others were suggesting it happened before this.
• What mechanism might exist to cause this slow down during exercise in the heat?

The study was relatively simple: 12 well-trained cyclists performed 20 km time-trials in the lab, either in the hot condition (35 degrees, 60% humidity), or cool (15 degrees, 60% humidity). During the trials, we measured something called EMG activity, which is basically the electrical signal sent from the brain, to the muscle to cause it to contract. This method, which is the same as was used previously to show how the brain activated less muscle when it reached 40 degrees, always ends up being the point of attack for people who don't buy into the whole regulation of exercise argument, but more on that later.

Things like heart rate, Rating of Perceived Exertion, skin temperature, body temperature were all measured during the trials as well. I'll sum up the two key findings below:

1. The pacing strategy differs, almost from the start of the trial

The graph below shows the power output measured through the trials. You'll not that in the heat, for the first 5 km, the power was the same as in the cold, and then it started dropping, whereas it was maintained in the cool trial. The result was that the overall power output was lower in the heat. Nothing unexpected there...

The mechanism - muscle activation and anticipatory regulation

But, what you should be asking is the following:

Why did the cyclists slow down after only 30% of the trial was completed?

There are two possible answers to that question:

You could say, based on the theory of heat LIMITING performance, that they slow down because their body temperature has risen quite high in those first 5km, and they slow down, because as was shown recently, a high body temperature directly prevents the brain from activating muscle;

OR, you might say

They slow down at this point so that they don't get hot later on during exercise. That agrees with the Marino theory for anticipatory pacing, and something other than high body temperature is responsible for reducing their power output.

The graph below shows the answer to this question:

What this graph shows is the EMG activity (as a % of maxium - we express it relative to some maximal value of muscle activity, measured before the trial when the cyclist pushes as hard as possible for 5 seconds) over the course of the trial.

You'll notice two key things:

1) First, the EMG activity is lower in the heat than in the cold, almost from the outset

2) The EMG activity increases significantly at the end of the trial - the "endspurt"

These changes in EMG activity EXPLAIN the changes in power output in our previous graph. That is, the power output in the heat is lower BECAUSE the activation of muscle is lower from very early on. Then, at the end of the trial, the power output increases substantially because the brain is activating more muscle. More muscle activation means more force, and that means more power.

But perhaps the key to all this comes from the tables I've inserted over the graph, which show that:

1. The athlete slows down (the power output graph on top) and activates less muscle (the EMG graph below) even though their body temperatures, heart rates and even their Perception of Effort (the RPE) are THE SAME as in the cool condition. If you compare the HOT to the COOL conditions, you see that the body temperatures are "only" 38.4 degrees celsius, which is not different from the COOL condition, and nor is it anywhere close to the supposed "limit" to exercise of 40 degrees.
2. Think for a moment about that for a moment - they "choose" to activate less muscle, to cycle at a lower power output, despite the fact that they are NOT HOT, and nowhere near the supposed "critical limiting temperature". This may strike you as obvious, but again, you need to ask HOW they could possibly know this, and based on what information is such a 'decision' made?
3. Then, at the end of the trial, the athlete is able to SPEED UP in the cold trial, activate MORE MUSCLE, even though their body temperature is higher than it was before

Quite clearly, the decision to speed up or slow down has nothing to do with body temperature, which is what the textbooks say. These findings show that the activation of muscle, the power output and hence performance are regulated by something much more complex that simply the direct effect of body temperature.

The most amazing of all - you slow down, even though you feel the same!

What is perhaps most remarkable of all is that the cyclists slowed down in the heat even though their perception of effort was the same as in the cool condition. This perception of effort basically measures an overall Rating of Exertion, which is to say it's a mix of fatigue, effort and general perception. It's a highly complex measurement, and we'll come back to it later in this series.

Point is, it's not as though they felt worse, and therefore slowed down! That's what you might think, but the finding above suggests this is not the case. In other words:

• you feel the same in terms of your effort and fatigue levels
• you're equally as hot as you were in the cold condition
• your heart is working at about the same level

yet you slow down through the activation of less muscle.

Now, there are many issues here that I won't get into for this post, but will gladly discuss in question and answer things (so do read the comments at the bottom of this post because your question may well come up there!). So yes, there are some grey areas, there are mechanisms still missing (what causes them to slow down, for example?) and there's much to be discovered still. But the take-home message here is that:

A model that says that you fatigue in the heat because you get too hot is clearly incorrect. Rather, fatigue in the heat is complex, and impaired performances happen long before athletes ever get hot. The regulation of exercise happens in anticipation of overheating, and it's mediated by factors that are still too complex to pin down exactly. However, there are theories, and that's what we will address next.

Join us then!

Ross

Fatigue Series Part 4: Exercise in the Heat

Exercise in the heat: Predicting the physiological future - African runners outperform white runners in the heat

We're back with Part 4 (or is it 5 or 6? I've lost count!) of our Series on Fatigue during exercise. In our last post, we looked at exercise in the heat, and found that:

• Laboratory research shows that human beings will stop exercise when their body temperature rises to a certain level. That level is of course dependent on the athlete's motivational levels, though interestingly, not necessarily on their training status or performance.
• We also saw that the science has shown that when the body temperature rises to reach about 40 degrees, the brain actually activates less muscle than a "cooler" brain, and that there is evidence for reduced arousal and motivation.

So, the hypothesis, based on these constant workload studies, is that the heat affects performance because:

A high body temperature DIRECTLY inhibits the ability of the brain to activate muscle.
Therefore, exercise stops (because in these studies, remember, slowing down is not an option)

What happens when the athlete CAN slow down? Self-paced exercise

Today we turn our attention to the case where athletes can slow down - this is arguably more representative of what you will see in Beijing later this year, since any athlete can, at any stage, choose to drop off the pace. Of course, they lose their medal chance this way, but it's a much more applicable form of testing.


And to understand this, we look a few studies. We'll do it in a couple of posts, because otherwise the length would become enormous. So today, we consider one study, with more to come in the next few days.

In 2000, a study by Tatterson (J Sci Med Sport) found that cyclists slowed down soon after they started a 30-minute performance trial in hot, but not cold conditions. What was significant is that their body temperatures were not higher in the hot than in the cold when they slowed down. Obvious, yes, but quite contrary to the theory that your brain stops activating muscle AFTER your body temperature hits the "threshold". They didn't measure any index of muscle activation, however, but it was a crucial observation that something else (and not direct body temperature) was playing a role in the heat.

African runners in the heat - anticipatory regulation thanks to their smaller size?

Then, a study done by Frank Marino while he visited Cape Town a few years back, was one of the first to use the words "anticipatory", because his finding (discussed below) found differences in the pacing strategy of African runners compared to white runners in hot conditions. So the conclusion is that something is happening BEFORE the body temperature rises, slowing the runner down so that they don't overheat.


And this is obvious. Think for a moment about when you go and train on a very hot day. You do not simply go out and run or cycle at your normal pace until suddenly, overcome with a sensation of hyperthermia, you slow down! Rather, your entire approach to the session is changed and you slow down LONG BEFORE you ever get hot in the first place! Within the first few strides, you're probably already going slower. So this is one of those examples we spoke about a long time ago - intuitively, we know what happens.


The question is HOW? And also, we have to consider the prevailing expert opinion of the time. In this case, remember, the "textbook" knowledge says that exercise is impaired because the HOT BRAIN directly inhibits muscle activation after body temperatures are raised by exercise.

So, let's look at the study by Frank Marino. I'm sure he'll forgive my very rudimentary depiction of his methods below:





So he had 6 African and 6 white runners, quite well trained, doing a performance trial after a 30 minute steady run in either HOT (35 degree) or COOL (15 degree) conditions.


The starting hypotheses for this study, had you read the theories about exericse in the heat, would be:

• Performance would be impaired in the heat, so the runners would be slower during the 8km trial in the hot condition. This is fairly obvious.
• They'd slow down in the HOT trial because they'd be much hotter than in the cool trial - the high body temperature (and HOT brain) is failing to activate muscle, as we're told by other research.

This is what was found:

Graph of running speed (km/hr) against time for the 12 runners during 8km time-trial performances preceded by 30minutes run in hot and cold conditions

I've highlighted with a red circle one of the more significant findings - the white runners started the 8km trial much slower than the black runners did, from the first minute. Of course, both groups eventually slowed down in the heat compared to the cold (the black symbols on the graph), but it's this difference between black and white runners that should be of interest. So, why then, do the white runners start so much more slowly?

Option 1 is that they are already hot. They might be finishing the 30 minute steady run with higher body temperatures. That would agree with the theory that the hotter you are, the slower you go...

However, look at the graph below:

Graph of rectal temperatures during the course of the trials in hot and cold conditions

Again, I've highlighted the key point there - the black and white runners had THE SAME rectal temperature when they started the 8km run. And not only this, but the temperature was "only" 38.2 degrees, so they were way cooler than the supposed "limiting temperature".

Yet, for some reason, despite the fact that the black and white runners have the same temperature and are not in any danger, the white runners "chose" to START an 8km time-trial slower than the black runners. We can therefore dismiss Option 1 from above, and say that it's clearly not a case of a hot athlete slowing down! If it was this simple, with some "direct effect" on the athlete, then the slowing down would happen equally in the two groups. This is an amazing finding given the prevailing view that the heat impairs performance directly, I hope it strikes you that way too!

So what, then, is the reason? Well, that's of course difficult, if not impossible to PROVE (as we've seen recently courtesy the CAS, "proof" in science is not as easy to do as people think), but here's a theory from the Marino paper:

• The African runners were much smaller than the White runners - 59 kg compared to 77kg, to be exact. The white runners were taller, however, and had a larger body surface area.
• We know from previous research that a smaller runner produces less heat while running at the same speed as a larger one. That is, the total heat PRODUCTION is dependent on body mass, and smaller people produce less heat.
• Smaller runners also lose less heat, however, because they have a smaller body surface area to lose heat to environment.
• But the key is: These two factors don't exactly cancel one another out. The result is that even though they lose less heat, smaller runners are still able to lose more heat RELATIVE to heat production than larger runners. This has to do with the ratio their mass to body surface area - they may lose on surface area, but their lighter weight more than makes up for it.
• The net result of all this, is that smaller athletes have a reduced RATE OF HEAT STORAGE than bigger runners.
• Now, given this fact, if two runners are going along at the same speed, the smaller one will be storing less heat, and therefore his/her body temperature will be climbing slower than that of the big runner.
• Put differently, it means that if both athletes are concerned about how hot they are getting, then the bigger runner will have to slow down in order to prevent his heat storage from rising, which would ultimately increase his heat production.

Now, with all those facts on the table, the results start to offer an interesting theory:

The rate of heat storage is responsible for Anticipatory Regulation of exercise and pacing strategy in the heat

The theory is that the white runners, by virtue of their bigger size, have an increased rate of heat storage. (Note that this effect (the different pacing strategies, that is) is likely due to size - had the groups been matched for mass and height, the result might have been different - see the comments section to this post!)

The brain is "clever" enough to know that if the athletes starts their 8km time-trial at a fast pace, then their very high rate of heat storage is going to see their body temperature RISE very rapidly. They are in danger of reaching a core temperature of 40 degrees BEFORE the end of the time-trial (which they know is 8km long). Remember, at this temperature, the brain says "Enough" and exhaustion usually occurs (or soon after).

Therefore, the brain says "Whoa, back off a little!", long before the athlete overheats, and with the intention of making sure that they do not reach this limiting temperature before they are able to finish the trial - it would be a complete failure to do this, and reach the 6km mark by the time their brain says "enough". So instead, it REGULATES their performance IN ANTICIPATION of ever reaching that limit. That Anticipatory Regulation is achieved or mediated by the rate of heat storage, which is different from the very early stages of exercise.

On the other hand, the African runners, who are smaller, have no such problems. They thus maintain a higher speed, and a similar rate of heat storage, leading ultimately to an improved performance. Note, very importantly, that in the cold, this difference between black and white runners does not exist. Therefore, it's not a case that the white runners are just inferior to the black runners - it applies only in the heat, when the environmental temperatures bring this heat storage aspect into play.

Looking ahead

What this study does not do is measure anything related to brain function. Now, that's very difficult to do during dynamic exercise, and is often criticized, but we'll discuss a study tomorrow that looked at EMG activity (a measure of how much muscle is being activated by the brain) during trials in the hot and cold. This was the first study to find evidence for it. It was also a study I did for part of my PhD, though I'm not claiming anything here - it was be default, more than anything else!

So that's coming up in our next post - evidence of Anticipatory Regulation of Exercise Performance, along with a few more concepts to build on the ideas put forward here.

Join us then!

Ross

Fatigue Series: Part III - Exercise in the heat

Exercise in the heat: The "off-switch," the limiting temperature, and the Beijing Olympics

We're back with more on fatigue, and as promised, the strategy we'll adopt over the next few posts is to look at fatigue in very specific situations. These situations, often the intervention controlled by the scientists, offer a glimpse into how exercise performance is either limited or regulated, and help us understand how performance might be improved (by working backwards from the regulation or limit).

As we discussed in our last post, studies can look at exercise performance as being "limited" by some failure, or as a "regulated" process, where the body aims to maintain homeostasis by regulating what we've defined as the pacing strategy.

In today's post, we look at exercise in the heat. This is especially topical this year, because the Beijing Olympics promises to bring the influence of heat and humidity into the public eye in a big way. Elite athletes the world over are preparing for the heat by using special chambers to replicate the likely Beijing conditions, and it's also one of the reasons we discussed a few weeks ago that the Kenyan runners, the big favourites for the marathon, might have their work cut out, given the "levelling effect" that the heat can have.

Exercise in the heat: What ultimately limits performance?

We start our investigation of the heat by asking this question, which represents, of course, the "limitations" model for exercise. This is a crucial question, however, because if we want to know how exercise is regulated, it's important to recognize that it is ultimately limited by some variable.

The early theory - blood supply limitations

And until about 30 years ago, the early understanding of exercise in the heat is that it was limited because the body did not have enough blood to get to both the muscles and the skin, where it was needed for cooling. The result of this limited blood supply was that the muscles were deprived of oxygen, became anaerobic, and exercise stopped. Alternatively, the blood pressure was challenged to the point where exercise was completely impossible. This would, according to our discussion of constant workload vs. self-paced exercise, represent the point at which the "bridge breaks", or the light goes off!

However, in 1979, a scientist called Nadel published a study showing that blood flow was in fact not limiting during exercise in hot conditions. This was followed by studies in the 1990's from Denmark (where a lot of heat research comes from) which showed the same thing - there may be a challenge to blood supply during exercise in the heat, but the body is more than capable of meeting it in healthy individuals. And so that theory was disproven.

A clue to the limit - mental confusion

But around the same time, it was recognized that when these athletes were exercising in the laboratory, there came a point at which they actually developed mental symptoms - lack of co-ordination, dizziness, confusion and loss of ability to control their limbs! This led scientists to speculate that in fact, the limit to exercise in the heat was central, involving the brain. The speculation at the time, as far back as 1987 by a Canadian pair (Bruck and Olschiewski), was that a high body temperature affected brain function and the drive to exercise.

The famous video, shown at the end of this post, captures this situation - it is Gabrielle Andersen, staggering and swaying through the Olympic stadium in Los Angeles, typifying the human response observed in the research subjects at the point of exhaustion during exercise in the heat - paralysis on one side of the body, confusion, loss of co-ordination and balance.

Limiting body temperature - the "off-switch"

Subsequent work showed this "central fatigue hypothesis" to be a distinct possibility. It turned out that animals and humans all stopped exercise at a very distinct body temperature.

For example, in cheetahs (running on treadmills, believe it or not!), it was noticed as far back as 1973, that at a particular point, the animals displayed very strange behaviour - they simply "gave up" running and lay down! In the words of the authors (Taylor and Rowntree):

“…the cheetahs refused to run… They would simply turn over with their feet in the air and slide on the tread(mill) surface".

Later, it became possible to actually measure the body temperature of animals and humans during exercise (I can't imagine it's very easy to measure the body temperature of a Cheetah during running! Rats and goats, perhaps, are easier propositions!). It was found that all animals seemed to have a very narrow range of body temperatures at which they would stop exercise. For example, beagles stopped at body temperatures of about 42 degrees, antelope 42 degrees, and goats 43 degrees. Rats, the most tested of all, were found to stop at about 41 degrees celsius.

Human beings - a thermal limit to exercise and a proposed mechanism

Then came humans. And perhaps not surprisingly, research found that humans tended to stop at a body temperature of about 40 degrees celsius. What was most interesting is that this temperature was consistent regardless of pre-cooling, the rate of heat storage, and the degree of heat adaptation. In other words, it seemed that humans have this "off-switch" at 40 degrees celsius, irrespective of the external intervention. The only thing that changed was the time it took to get there - for example, a person who is well adapted to the heat is able to sweat more, lose more heat and therefore takes much longer to reach this limit than someone who goes straight into a hot environment. But they still stop at around the same temperature, according to this lab research.

Remember that this is found when humans exercise in a laboratory at a constant workload until they themselves decided "enough is enough" and choose to stop. When given a little more motivation (like when an Olympic gold medal is on the line, or that 10km PB you've been training for), it's likely that you'll get this body temperature up to 41 degrees, but beyond that, it seems that exercise is very nearly impossible, at least in the absence of some pathology or abnormal response.

Remember also that heat stroke, which is a very serious medical condition, happens at a temperature of 42 degrees, so the limit to voluntary exercise happens well before this level is attained. That of course raises the interesting question of why heatstroke happens - a malfunction of the "off-switch", perhaps? Or a failure of the signal to actually reach the brain to stop exercise? It's a difficult one, for which there are theories, and we'll cover them at some stage.

The mechanism - reduced muscle activation and arousal levels

So once this was discovered, science began looking for the mechanism, the HOW of the "off-switch". Because the thinking was that the central drive (from the brain) was the culprit, it made sense to look at brain function for clues, and that's exactly what the Danish researchers did. So, in a series of studies, cyclists were made to ride in the heat at a fixed workload until exhaustion, and then various measurements were made of brain function and muscle function. There were two key findings:

1. At very high (40 degrees) body temperatures, immediately after the athletes had become exhausted, they found that the activation of muscle by the brain was actually LOWER than when the body temperature was only 38 degrees. The graph below shows the EMG activity in the quadriceps muscles after exercise in the hot and cool conditions. It's quite clear that the EMG, which is a measure of activation of muscle, is lower when the body is hot. So that gives an indication of why the cyclists were no longer able to push out the required force - their brain simply prevented them from activating the required amount of muscle.
2. There was evidence of reduced arousal/motivation levels once the body temperature rose. In fact, what was found is that there was a very good correlation between a rise in body temperature and a reduction in arousal. Motivation or arousal, incidentally, was measured using EEG and the ratio of certain brain waves which are known to indicate this parameter. The key point here is that as the body temperature gets higher, the motivation declines, and this in turn is responsible for a rise in the perception of effort. They therefore found a good correlation between RPE and a rise in body temperature, though of course, correlations are often a slightly misleading. The key is: Increased body temperature = decreased motivation/arousal = increased effort perception.
   

The problem with this research: What happens before the "off-switch" is reached?

Again, the key question one should be asking is whether this solid science is actually relevant to what you are going to witness in Beijing later this year? Because in Beijing, the world's best atheltes will line up, highly motivated, take part in a race, where they can speed up or slow down, depending on the innumerable factors that go into racing strategy.

The studies have shown that when athletes go at a fixed pace until they are exhausted, they'll stop when their body temperature hits about 40 degrees. Perhaps, given the incentive of Olympic Gold, that temperature will be higher. And perhaps, when they push themselves hard enough for the rewards that are on offer in Beijing, they'll be able to raise their body temperatures so high that they end up looking like the famous Gabrielle Andersen from the 1984 Olympic Games marathon (see video below).

But, realistically, you know that this doesn't happen, because Olympic competition is not a fixed workload trial to exhaustion in a lab, and the athlete is able to slow down if they wish. And so what you will see in Beijing is athletes dropping off the lead pace after only 7 km of a 10km race, and then you have to wonder: Are they hot, or is something else in play? And you should be asking: What happens when the body temperature is 39 degrees, and there are still 20 km of the marathon left to run? Does the brain allow the athlete to just run and run until it the body temperature hits 40 degrees, and the athlete stops? Of course, you suspect the answer is no.

So the "limitations" theory for exercise in the heat, while proven in the lab, fails to explain what you'll see in Beijing later this year, and will have experienced in your own training, many times.

And that's what we'll cover in our next post. Join us then!

Ross

Spring Marathon season

Wrapping up the spring marathon season - a Kenyan season, but will the Olympic Games be the same?

Yesterday's Boston Marathon brought the curtain down on the 2008 Spring Marathon season, and all eyes now turn towards the August Beijing Olympic Marathon. That will be followed by the Autumn racing season, consisting of Berlin, Chicago and New York, where hopefully, we'll see more world-class racing performances.

Because of the proximity of the Olympic Games, the Autumn races in October are more likely to feature the "could have beens", an opportunity for the fourth, fifth and sixth best runners to show what their federations might have missed, particularly in the case of Kenya. The Berlin race will almost certainly also feature Haile Gebrselassie, who looks set, I believe, to attempt the world record there, unless he changes his mind about Beijing Marathon participation.

A Kenyan Spring: The world's roads belong to Kenyan men

However, looking back over the last month's races, without a shadow of a doubt, the month of April, and the world's roads, have belonged to Kenya. Of the four marathons we covered (Paris, London, Rotterdam and Boston), Kenyan men claimed three titles, missing out only on the Paris race, which was won by Tsegaye Kebedi in impressive fashion. You can read our analysis of the World Marathon Major races by clicking on the "Marathon analysis" tab on the top of our page (you'd have to visit the site, in case you're getting this as an email).

But it was the manner of the Kenyan dominance that stood out. On Sunday 13 April, THREE Kenyan men broke 2:06, two in London, one in Rotterdam. They also placed fourth in London, took out seven of the top 10 places in Rotterdam, and then Robert Cheruiyot won Boston with a dominant, front running performance yesterday. Martin Lel, Sammy Wanjiru and Robert Cheruiyot are a ferocius trio, and surely, will be selected for Beijing. The heat may pose a problem (discussed below), but on form, they are very, very difficult to beat, given what we've seen over the last ten days.

So all is good in the world of Kenyan marathon running. This comes three weeks after their officials were ready to hit the panic button after a very disappointing showing at the World Cross Country Championships, where they failed to win a single title, being completely overshadowed by the Ethiopians. However, that is another story, one which I'll look at in the coming weeks, with an eye on the track events in Beijing. For now, however, world marathon running is very much a Kenyan affair.

Will the Olympics deliver the same results for Kenya? The potential of a "meltdown" in the Beijing heat

So quite rightly, Kenyan officials and fans will be expecting gold come Beijing. On paper, and on form, they have three out of the top four marathon runners in the world, men who have shown the ability to get the training and performance right on the day, along with ability to produce astonishing finishing kicks (Martin Lel - 60 second final 400m ability) and aggressive front-running displays (Robert Cheruiyot, solo running over Boston's hills). So, no apparent weakness then?

Well, not quite. There is the small matter of the heat and humidity in Beijing. And the reason this is all relevant is because no one really knows how these athletes will be affected.

A false perception that heat favours Africans?

There is a perception, certainly among the non-African media, that a hot race favours the Africans. And ordinarily, this would be so - they do train in Equatorial climates, after all, where summer temperatures are regularly in the 30's, with high humidity! However, it becomes very interesting to consider what happens in Kenya during the month of July, which is when the major training phase will take place in Kenya.

There is an important assumption to be made first, however. This assumption is based on my own personal interaction with scientists and coaches who have worked with the top Kenyan athletes, so I believe that it is reliable, though admittedly second-hand:

That is, most of the Kenyan athletes will not be leaving their normal training base to do any heat adaptation training in the lead up to Beijing. The reason, according to scientists at the Kenyatta University in Nairobi who we in Cape Town have done some work with, is that the athletes prefer the familiar environments and the single-minded focus these bases provide them with. So rather than adopt the approach of a Paula Radcliffe, and the US Olympic team, who are planning training camps in the hotter European climates, many of Kenya's best will remain in their high-altitude camps right until the Games.

This has major implications for their ability to adapt to the heat. Because contrary to popular belief, Kenya is nowhere near hot enough to acclimatize during the winter months of June and July! Cold is of course a relative term, but if you take a look at the historic weather data for Kenya in July, you'll see that in Eldoret (perhaps the most famous training base), the average peak temperature is ONLY 20 degrees celsius (69F), and the typical morning temperature is 10 to 11 degrees Celsius (52 F). Remember that Eldoret is at altitude (2,100m), and so it's neither hot nor humid there in the winter months.

This means, of course, that a Kenyan training in Eldoret during June and July has zero exposure to temperatures likely to be encountered in Beijing. For the record, the average daily temperature in Beijing in August is expected to range between 20 and 30 degrees, with a humidity in excess of 70%. Those are seriously challenging conditions, and if an athlete heads into that situation unprepared from a heat-physiology perspective, the effects will be severe.

The Ethiopian approach to Osaka, and Kenya's options

What is interesting to consider is the difference in approach taken by Ethiopian athletes in the build-up to the IAAF World Athletics Championships in Osaka last year. Osaka, incidentally, is very similar to Beijing - hot and humid. I know that the Ethiopians, who are the same as the Kenyans in that they choose to stay in the country to prepare for the major races, actually brought in expertise that included providing access to a heat chamber before they went to Osaka.

So, given that Osaka was going to be hot and humid, the Ethiopians made use of a chamber which effectively brought the heat to them. They did training sessions which simulated Osaka conditions, and it's likely they'll be using the same in preparation for Beijing. This was a highly efficient technique since as little as 60-90 min per day in the heat chamber will stimulate the physiological adaptations that will enhance thermoregulatory function in the heat. These runners are likely already running twice a day, so once in the chamber should not have impacted their high-quality efforts.

Whether the Kenyans will adopt a similar approach remains to be seen. From a physiological point of view, it is absolutely crucial that any athlete who wants to be competitive in Beijing be adapted to the heat.

It doesn't matter how good you are, how dominant a marathon runner, if you are unfamiliar with the expected heat in Beijing, physiological function will be compromised when you are first exposed to the heat, and it takes a minimum of five days of exposure to start to see any adaptations.

The scientific evidence on this is very clear - it takes between 5 and 8 exposures to hot and humid conditions before the body has made most of the adaptations and is able to keep its temperature down. The problem for the Kenyan runners, then, is that unless they figure out a way to expose their physiology to the Beijing heat and humidity, they will be entering the race "cold". This has happened before, and there's a chance it will happen again.

If it does, then don't be surprised if a relatively unknown athlete comes in and wins a surprise Gold medal. It is for the reasons explained above that I believe that Sammy Wanjiru, thanks to his familiarity with the Far East, and possibly the fact that he'll be based in the East during his build-up, is the bigger favourite, despite the fact that I believe that Martin Lel is the world's greatest marathoner today. Lel, all things being equal, wins any marathon he runs in. Unfortunately, things are rarely equal, and the heat is the great leveler. Kenya, for all its dominance over the roads of London, Boston and Rotterdam, may yet find itself neutralized by a failure to prepare for the heat in Beijing.

As the Olympics draws nearer, this issue of heat will become much more relevant. We will certainly bring you all the insights and explanations, including a full series on heat physiology and acclimatization, and also hopefully some inside information on what the Kenyans and Ethiopians are doing!

Ross

Marathon survival: Courage and physiology

Marathon survivorship – physiology of some courageous marathon finishes

Last week, we featured the debut marathon of Kayoko Fukushi of Japan. As the fastest Japenese woman ever over the HALF MARATHON, much was expected of Fukushi’s debut marathon in Osaka, but in the end, she left the world with memories of a different kind – 15 minutes to cover the final 2km, three falls in the final 300m in the finishing stadium, and testament to the challenges posed by the marathon distance.

In the aftermath of the race (you can watch the final 400m, as well as our analysis of the race at our previous post), Fukushi’s final 400m was a hot topic on discussion boards and running websites. So in this follow up post, we thought we’d look back on other famous marathon finishers. We tip our hats, and our physiological paintbrush, at the following three famous “Marathon survivors”.

Gabrielle Andersen-Scheiss

In 1984, for the first time, women were allowed to run the marathon at the Olympic Games. The race was won by Joan Benoit, in a remarkable time of 2:24:52, beating off a stellar field including Weitz, Kristiansen, and Rosa Mota. The time was remarkable for a number of reasons. Not least of all, conditions in LA were hot and heavy – ahead of the Games, there was a great deal of anxiety over potential problems caused by the pollution – much as there are around the Beijing Olympic Games this year.

But in the end, the heat caused the problems, and the biggest problems of all were encountered by Gabriela Andersen-Scheiss, of Switzerland.

Andersen-Scheiss entered Olympic Games AND Physiology folklore thanks to her performance over the final 400m of the race. This video, shown below, is often shown at physiological conferences as a demonstration of what happens to the physiology when the body temperatures rises to reach a ‘critical threshold’.

What you will see in the video below (apologies for the poor quality – if anyone has a better version, let us know!), is that Andersen Scheiss enters the stadium clearly in distress, and over the next 400m, staggers around the track, taking an incredible 5 minutes to cover the final lap! The video edits out much of this last lap (again, let us know if you know where a better version exists), but you can get a good idea of just what is wrong – it seems as though the left side of her body is dragging the “paralysed” right hand side behind it. And this is typical of what happens when the core body temperature rises to above 40 degrees Celsius.

The role of the brain

We’ve brought this up before, but it bears repeating – until the mid to late-1980’s, the theory for exercise in the heat was that you fatigued because the body was unable to provide sufficient blood to the skin for cooling AND the muscles for exercise. In this theory, dehydration was a problem because it meant less blood, which only worsened the problem. But in 1979, Ethan Nadel found the first evidence that the blood flow was not the problem. This finding was repeated in numerous studies, where they found that the body was perfectly capable of getting enough blood to muscle and to skin.

However, the body temperature can still rise (this is a function of exercise intensity and the environment), and when it happens, the evidence began to suggest that the brain was involved. Why? Because scientists started to observe that when people in LABORATORIES hit a body temperature of 40 degrees, they started to display symptoms of neurological problems. Which is exactly what you see in Andersen-Scheiss – “paralysis” of one half of her body, inability to control the limbs, and so forth. This classic symptom was strongly suggestive of the neural contribution to fatigue.

It was later found that when the brain gets too hot, it actually recruits less muscle (Nybo and Nielsen, 2001). Of course, when you exercise in the heat, it’s not quite as simple as a brain the stops activating muscle when you get too hot – I (Ross) did a study in 2004 that found that the activation of muscle actually goes down BEFORE you get too hot. In other words, the brain slows you down by activating less muscle IN ADVANCE of hyperthermia, specifically so that you don’t reach this point of complete exhaustion and ‘paralysis’.

However, as the video above testifies, it happens, with dramatic consequences. Andersen-Scheiss, for her part, became something of an Olympic legend as a result of her courage. She ended up finishing in 37^th place, some 20 minutes after Benoit. She was treated and released within 2 hours, showing how even the most intense effort is probably still within the reserve capacity for the body.

Jim Peters – the Vancouver 1954 marathon

Jim Peters of England was the Paula Radcliffe of his generation - he had broken the world record four times and was the first man to run under the 2:20 barrier, taking the record down by an astonishing eight minutes to 2:17:39!

So when he lined up in the 1954 Vancouver Empire State Games (today called the Commonwealth Games), he was the overwhelming favourite. This was the same Games, incidentally, that Roger Bannister and John Landy raced in what would later be called “the mile of the century”, with Bannister outkicking Landy to win. That race actually happed while this marathon was being run, and so Bannister actually sat in the stadium waiting for the men to finish.

Anyway, the marathon that day was particularly hot, and Jim Peters staggered into the stadium in first place, but was looking like he'd had too much to drink. He was swaying from side to side, and it looked as though one half of his body had been paralysed – much in the same way as Andersen-Scheiss would look 30 years later.

The conditions in Vancouver were pretty warm with starting temperatures in the shade in the high 20's Celsius. Reports were that the sun was so warm that the tar melted during the race! The temperatures may not jump out as being exceptionally high for those in the hotter parts of the world right now, but given that most of the athletes were not adapted to the heat, it was a tough day in the marathon. The conditions were so severe that out of 16 starters, only 6 finished the race.

Jim Peters was not one of them. After entering the stadium, with only 385 yards to run, Peters fell SIX TIMES within the first 200 yards. He took 11 minutes to cover that distance (making Fukushi look like a greyhound in her race!), before eventually collapsing for the final time – 200 yards SHORT of the finish line! He was taken to hospital, where he spent 7 hours being treated intensively before being released.

Incidentally, the athlete who was in second position with about two miles to run, Stan Cox, had also collapsed and ended up in hospital. At the 25 mile mark, he was so disoriented that he ran into a lamp-post, collapsing again. Eventually, police helped him to an ambulance, and he was taken to the hospital, where he’d later be joined by Peters.

And then finally, the eventual winner was a Scot, Joe McGee, who had actually collapsed five times on the course as well! But he heard that the two men who had been in front of him failed to finish, he picked himself up and went on to win! An attritional race if ever there was one!

The IronMan duel – Sian Welch and Wendy Ingram

And finally, for perhaps the most dramatic video we know of, we go to the IronMan Hawaii Triathlon of 1997, where Sian Welch and Wendy Ingram “race” over the final few hundred meters for fourth and fifth place.

This video, shown below, is difficult to watch, for the sheer agony that I’m sure most of you can relate to in some manner. It’s absolutely remarkable because it shows two elite athletes, both struggling with a combination of fatigue, muscle cramp and in the case of Welch in particular, hypoglycaemia. It’s quite clear that she’s in a disoriented state, and struggles to balance, find direction and stay co-ordinated.

Wendy Ingram, for her part, is cramping quite severely, and modifies her running style drastically in the final straight before the finish line.

What is most amazing, from a physiological point of view, is that the women move through different stages of what I would call “muscle activation patterns”. It’s as though there is a Plan A, which is to run absolutely normally, finishing strong (like some of the men who are finishing at around the same time as these two, you’ll see them in the background).

But given the difficulties both are experiencing, the brain quickly switches over the Plan B, which is this “modified running technique” – anything to keep going forward. Ingram’s “spider walk” is amazing, she’s clearly putting everything she has into what looks an incredibly uncomfortable running style!

Welch is unable to do even this – her muscles have simply been “switched off” and she has nothing left, mostly as a result of the low energy she has available and her fatigue – tired muscles with little fuel, and the brain says “No chance you’re running any more!” She’s unbalanced, uncoordinated and out of control. Eventually she staggers and walks to within meters of the finish line – she is on Plan C. But then she falls, taking Ingram down as well. And you’ll see in the video, the eventual winner between the two of them is the one who first realises the need for Plan D – Crawl!

So it’s an astonishing video, and you’ll hear reference to Julie Moss, a link you’ll find in the comments section of our Fukushi post from last week.

But this finish, and these two women, must surely go down as one of the bravest and most courageous, dramatic finishers in history!

Can you ever overcome the body’s limit through sheer willpower?

One question that is often asked when this whole area of “limits to performance” is discussed is this whole issue of “mind over matter”. What we are saying is that brain decides when “enough is enough”, and reduces the activation of muscle fibers BEFORE you even get near the dangerous levels of body temperature or fuel depletion, for example.

The logical question, however, is “Can an athlete, through sheer willpower, find that little bit extra, over-ride the brain’s protective reduction in muscle activation, and allow the athlete to go that little bit faster?” Professor Tim Noakes, who is one of the primary drivers of the theory of the brain protecting the body, often talks about the psychology and willpower aspects. And while they are relevant, I feel it’s not quite correct – it’s not simply a case that the guy who wants it most will win, which is unfortunately the spin that is often put on it.

So the answer is complex. Certainly, willpower and psychology play a role, and different people will tolerate different levels of discomfort. But I think that what these videos and stories show is that eventually, physiology wins the day. Peters, Welch, Andersen-Scheiss, and Ingram are all examples of athletes who have dug deep, found EVERYTHING their physiology has to offer, and quite literally run to the “edge of the limit”, but eventually, their physiology shuts down so completely that they simply could not run anymore. And yes, they survived. So in that sense, the brain did its job of protecting them, because all made recoveries, none “exercised themselves to death” (this happens, but it requires some special circumstances, we’ll discuss that in a future post).

So, to use a morbid analogy – no matter how badly you want to go, you cannot commit suicide by holding your breath – physiology wins. And similarly, during exercise, your willpower can take you that little bit closer to the limit. In fact, training takes you nearer that limit, since you learn what is tolerable and what is not. Motivation is of course important here too – given the right motivation, you might be prepared to tolerate a lot more than usual! But as you approach that “limit”, your body begins to progressively throw barrier after barrier in front of you. It becomes more and more difficult to hold the pace. Your brain is not activating muscle at the same level, and your perception of effort rises and rises. And eventually, physiology wins the day, and you stop, either voluntarily or because your legs fail to hold you up any more. This is human performance at the very extremes, but it’s still physiology!

Join us for exercise in the cold next post!

Ross

Muscle Cramps: Part I

Theories and Fallacies of muscle cramps

As promised in yesterday's post, today we kick off our latest series - Muscle Cramps. We hope that none of you did cramp in the middle of the night, as we mentioned yesterday! Though if you did, we're sure you stretched your calf and avoided the temptation to point your toe!

This is a follow-on from our series on Fluid Intake and Dehydration, and as we were preparing to write this series, we realised that there may actually be even more nonsense and blatant lies in the media than there were for dehydration!

Conflicts of interest revisited

In the dehydration series, we dealt with the very obvious conflict of interests that arise when a company which manufactures and sells sports drinks become the company who are funding and then performing much of the research on fluid and exercise. This is what happened when Gatorade created the Gatorade Sports Science Institute, and began funding research studies all over the USA, that rather unsurprisingly told the world that thirst was not enough, and you just had to drink as much as you could.

Can you imagine Gatorade issuing the results from those first studies saying to people "Folks, we've tested the sports drinks, and we don't have much evidence that you really NEED them. You'd most likely be fine without them, but hand over your money and buy your Gatorade at the counter anyway". An unlikely scenario. Of course, it was never as simple as that, and as we tried to explain previously, some of the early lab-based science was actually sound, but its application became the problem. More than this, the manner in which the research was compromised, becoming a form of shameless endorsement for the sake of sales in subsequent years was the ultimate problem. But that was all covered in our previous series, for those who are interested...

Muscle cramps - even more pervasive mis-marketing, but a complex issue

The same marketing vs scientific integrity debate exists for muscle cramps. The industry that has sprung up around the muscle cramp issue has spread far and wide. It includes Gatorade, who advocate the use of their drinks to replace the loss of salt which is, according to their research, responsible for the cramp in the first place! But more than this, there are dozens of products that claim to prevent cramp - next time you are in a pharmacy, take a look at the range - everything from gels, to creams, to pills, to effervescent tablets.

The two broad theories for muscle cramps

All these products work off the same premise - the put back the electrolytes that exercise will take out. And it's the loss of those serum electrolytes, the theory goes, that are responsible for the cramps during exercise. This theory, over 100 years old, is one broad category of theories for muscle cramps.

The second theory is that muscle cramps are caused by a 'malfunction' in the control of the muscle by the nerves - an abnormality of neuromuscular control which is caused by fatigue.

Our objective in this series is to look at these two theories, beginning with a bit of groundwork and history...

Defining cramp

Perhaps one of the first things to do is provide a definition for cramp, as well the usual disclaimer that we cannot possibly cover all the possibilities and scenarios in this series. Firstly, cramp has been defined as a "spasmodic, painful, involuntary contraction of the skeletal muscle that occurs during or immediately after exercise".

Note that this definition applies to exercise-related cramps only, and therefore, it excludes a whole host of other possible cramps. We must point out that if you do suffer from very regular cramping, there are some conditions that can cause this - endocrinologic, neurologic, and vascular disorders, treatment with certain drugs, and occupational factors. Then of course, some cramps are what the experts call "idiopathic", which means they have no cause (but actually means we don't know what causes them, but it sounds better to say "idiopathic"!). If you are a regular cramper, it's probably worth seeing a doctor and just having an exam to determine whether any of these broad factors might be responsible.

But returning to muscle cramps, the lifetime prevalence of cramping is reported to be as high as 50%, which is remarkably high. Some people are also quite clearly more susceptible, and you can actually predict with a fair degree of accuracy who will cramp during a marathon based on their history and their racing strategies (more on this later).

The history of cramping - the electrolyte depletion theory

The earliest reports of muscle cramps come from 100 years ago, when labourers in hot and humid conditions of the mines and shipyards suffered from cramps. Even that far back, the sweat could be analysed, and it was noticed that the builders had a high chloride level in their sweat (chloride, incidentally, is one half of the salt in your sweat). The conclusion that was made was that the labourers were sweating out valuable electrolytes, causing their muscles (and nerves) to malfunction. The heat and humidity were key factors that caused this situation. It must be pointed out that no one prospectively measured the sweat of the labourers who DID NOT CRAMP, something that we'll look at in our next post.

Later, the builders of the Hoover Dam famously recovered from cramp when they were made to drink salty milk, entrenching the theory that salt loss was the cause of cramp.

And perhaps rather surprisingly, that was it - based on those anecdotal observations, the theory which you probably hold true today, was born. That is, cramp is caused by a loss of sodium, chloride, and later calcium and magnesium were added to the mix. Heat and high humidity were implicated as "accessories", and the term "Heat-Cramps" was even conceived. According to this theory (as seen by this article and the "expert" testimony) , cramps happen because athletes exercise in the heat, lose electrolytes in their sweat, and the depletion combined with high body temperatures cause muscle cramp.

For example, take these testimonies:

"When a young athlete experiences heat cramps, pull him or her off the field into a cool area and gently stretch the affected muscle. "Have them drink, drink, drink, and then drink more," says Albert C. Hergenroeder, professor of pediatrics at Baylor College of Medicine and chief of the sports medicine clinic at Texas Children's Hospital.

"High-sodium drinks will prevent children from getting heat cramps," says Jackie Berning, PhD, with the National Alliance for Youth Sports. "Gatorade has just enough sodium to prevent those cramps. But if you're a heavy sweater, and you're still getting cramps after drinking Gatorade, eat some salted pretzels or salted nuts. Those work fine.""

There is of course more to it than this, but the essence is that the serum electrolyte depletion theory was created without any controlled, clinical studies to establish whether the depletion of salt through excessive sweating was to blame. Rather, the theory was picked up on and used to spawn the numerous products you can purchase today. But, as I'm sure you've guessed, there are some holes in it.

The problems with the serum electrolyte depletion theory

First of all, there is a key conceptual problem here, and that is that when you sweat, you don't actually reduce electrolyte concentration. That is, there are certainly electrolytes in the sweat, but the concentration of these electrolytes is so low, that sweating is likely to make you HYPERTONIC, not hypotonic. We looked at this in our posts on fluid - when you sweat, you lose more water than electrolytes, because the sweat is HYPOTONIC. Therefore, sweating cannot lead to a fall in electrolyte concentration.

What transpired was that Gatorade (and the rest of the 'industry', it must be said) developed the theory of "salty sweaters", which is the term they gave to people who they said have abnormally high salt levels in their sweat. Small problem - no one actually knows what a salty sweater is. How much salt does there need to be in the sweat before you are placed in this group? No one knows. Recently, Professor Martin Schwellnus, widely published in this area, posed this question to scientists at the Gatorade Sports Science Institute at a conference on cramping - he received no answer.

The truth is, even the saltiest sweaters around still have hypotonic sweat, and so the more they sweat, the more they will cause their electrolyte levels to rise, not to decrease. This is a very obvious problem that is overlooked by the electrolyte replacement advocates.

Of course, those of you who read our fluid series might be thinking that if you then drink a lot of sports drink, you can reduce the electrolyte content, but that's yet another reason why drinking too much is not a good idea...

The cramping paradox - why specific muscles?

The second problem is something we asked you in yesterday's post. We asked whether the depletion of serum electrolytes would be expected to cause cramps in specific muscles, or all over? Hopefully it is evident that if a cramp was caused by a loss of serum electrolytes, there is no reason for the cramp to be limited to one muscle only. Rather, you would cramp everywhere. In fact, in people who have lost a great deal of salt and have become hyponatremic (not during exercise, but clinically), we know that they cramp in ALL their muscles.

But somewhat surprisingly, exercise-associated muscle cramps ONLY happen in the muscles that have been used extensively for exercise. The afore-mentioned Prof Schwellnus found in 2004 that the quadriceps, hamstrings and calves made up 95% of cramps in the 56km Two Oceans race in Cape Town.

Leading onto the next post - further evaluation of the electrolyte depletion theory

In the interest of time, we'll call it on this post for today, and say that in our next post, we'll tackle the electrolyte theory in more detail and look at some of the studies that have looked at people who cramp and those who don't and compare their values.

Join us then!
Ross

Further reading:

Schwellnus, M. (2007) Sports Medicine, vol 37, 2007

Schwellnus et al., British Journal of Sports Medicine, vol 37, 2004