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Monday, March 14, 2011

The Central Governor and the Athlete's Clock: Pacing and performance

Pacing, the governor and the athlete's clock: A brief interview on a fascinating concept

Jonathan came across the video below earlier today.  Now, I must confess that I had never heard of the speaker, a Dr Thomas Rowland.  Nor have I had the opportunity to read the book about which he speaks in this interview, called "The Athlete's Clock".  But the concept grabbed my attention immediately, because as you may know, this whole aspect of the brain and the regulation of exercise performance was the subject for which I obtained my PhD.

So naturally, when the very first seconds of an interview present the question "Briefly describe the Central Governor theory and where you are in adhering to it?", my curiosity is raised.  And pleasantly, I have to say that the admittedly short summary that Rowland provides about it is a pretty good version of what has been developed and proposed (by Prof Tim Noakes, and all those who have developed this theory over the last decade or so, including, in my PhD and its research, me!).

Here's the interview, with more comments below:

In a nutshell

What Rowland describes accurately is that your ability to pace yourself during exercise is the result of an "anticipatory calculation" that is made by the brain during a race/training session, and whose purpose is to prevent you from causing physiological damage to your body.

He talks about how the brain prevents you from "over-exerting" (± 40 sec in the clip) and controls the pace you can select in order to do this.  He goes on to talk about these "dangers", and mentions the examples of "breaking bones", "shredding muscles" and causing a lack of coronary blood flow to the heart, all of which are possible but never occur.

Here's where it's a little more complex than the interview allows for (understandably), and what Rowland has not mentioned is maybe the most obvious and clear-cut illustration of how pace must be regulated to protect physiology, and that is during exercise in the heat.  When we exercise in hot conditions, our pace is regulated very early on in order to reduce the rate of heat storage.  Why?  Because if we didn't slow down, we'd soon be the "victims" of a potentially harmful rise in our core temperatures.  There's quite a lot of evidence that beyond about 40 degrees celsius (maybe 41 in a highly motivated athlete), exercise is basically impossible and we lose cognitive and motor function.  Above 41 degrees, things get risky - heat stroke and the eventual risk of death are a good reason to stay below this threshold!

But happily, that rarely happens, because our brain, and this "governor", is in control and it reduces our level of muscle activation in order to prevent us from achieving these rates of heat storage and high body temperature.  Quite literally, your brain does not allow you to activate the same amount of muscle, and thus forces you to slow down.  The end result is that we slow down BEFORE becoming too hot, and not because of it. 

That this happens is intuitively obvious, but was never really allowed for in studies where athletes were made to exercise to exhaustion - that kind of model gave us the theory that we "fail" at a certain point (high temperature, in this case).  And while this is true, it is incomplete, because during self-paced exercise, which is pretty much 99% of what we do, we have this option to slow down.  How this is achieved is a fascinating physiological question.

True in every situation

The same is true in every situation - at altitude, it's not the body temperature or rate of heat storage, but the degree of oxygenation (perhaps to the brain, according to latest work) that is regulated.  In other situations, energy supply, blood glucose and glycogen levels are defended.  In others, plasma osmolality - there are innumerable different "homeostats", all of which are monitored and regulated by the brain, and then controlled by changes in exercise intensity.  And that, in a nutshell, is the Central Governor theory.

A contentious theory

Of course, no theory fits into a nutshell, and there's a lot more to it than this, including some contentious issues.  Perhaps the most common one is that the "central governor" is not a distinct location - there is no little "black box" in the brain that is doing this calculation.  It is a concept, and therefore, allows for multiple areas to regulate performance.

This too is actually obvious, because if you think about it, in order for the brain to monitor the physiological status of so many different systems must mean it is done in multiple systems or brain areas too.  So afferent (or sensory) information must be interpreted in many different areas of the brain, each with its own function (like the anterior hypothalamus for increasing temperature, for example), and these different areas all produce this conceptual response. 

There was even a time, during the period when I actually wrote my PhD thesis in 2005/6, where we tried to move away from this term "central governor", because so many people seemed to miss the point that it was not a distinct location or brain structure that had not yet been discovered.  Rather it was the function, during exercise, of existing areas, which performed the role described by Rowland in the interview above.  However, people failed to appreciate this, mostly, I suspect, because many stopped reading the early work of Prof Noakes because it "offended" their paradigm.

The result was that the theory evolved steadily, but the knowledge of what was being proposed did not, at least among those who were opposed to it.   I remember attending conferences in the USA and Europe as a young PhD student in 2004 and 2005, and feeling enormous frustration that those who argued loudest seemed often to be the ones who had stopped reading in about 1999, and were therefore pouring enormous energy into criticizing concepts that had evolved by six years while they were looking behind them.

It was as if they expected a theory to be complete in its first iteration - that version 1.0 would be the final one, no improvements allowed (of course, if this were true in other areas, can you imagine what cell phones would look like?).  Had they spent time and energy reading the latest research, I dare say many would have agreed with much of it.  This sadly will never change, but happily, new researchers are debating the issue rather than its ancestors (and their ancestors, in this case...).  Interestingly, those who argued loudest early on have still failed to acknowledge the research, but are now producing papers were they are effectively claiming "We knew the brain was involved all along" - this is typical of the evolution of knowledge.  More on this in a future post...

Conscious vs unconscious, and the rating of perceived exertion

Another fascinating area of the debate is whether this regulation is "unconscious" or not.  Do we make a conscious decision to slow down, based on cognitive processes and experience, or does the physiological process happen unconsciously, with us becoming aware of it later?  That's open to debate, but my feeling was always that it was unconscious - it had to be, because conscious motivation can be as high as you want, but if you overheat/run out of glucose/become hypoxic, you slow down. 

Also, athletes slow down with the same perception of effort, which said to me that something in the brain was upregulating their degree of discomfort even while reducing their muscle activation and pace.  If a conscious decision was responsible, you'd see a rise in RPE either before they slowed down (in which case the RPE would be the cause - a conscious model), or you would see a fall in RPE afterwards (if RPE was the effect of a conscious decision).  The fact that it is neither, I reckon, says that the RPE is part of the regulation, which is therefore unconscious.  This is somewhat philosophical, of course.

Then related to this is the issue of "failed" pacing strategies.  What happens when athletes get it wrong, and go out too hard, and do actually overheat early?  What happens in sprinters who tie up before the finish line?  I'm actually embarking on some studies to look at this question right now, using cerebral palsy as a model.

In the end, I proposed (in my PhD) a model where the subjective rating of perception of exertion (RPE) was the "integrator" of all these different physiological cues.  Your RPE is the means by which all these different brain regions integrate those multiple signals - how hot you are, how much oxygen the tissues and brain have, how much energy is available, the mechanical strain on tendons, ligaments and muscles, and so on. 

The RPE then plays the crucial "fulcrum" role, because it is generated as a result of the sensory inputs to the brain, but is also a mediator of the reduction in muscle activation and pace, specifically to make sure that the RPE does not exceed an acceptable level - after all, the reason you slowed down in your last 10km was because you felt terrible at the pace you were running!  What was happening physiologically was responsible for this, and it changed thanks to your brain slowing you down, but you didn't know that status at the time!

For those wishing to read more, I hate to reference myself, but it seems the most distinct place to start from to learn about about pacing, and these are the two reviews of the literature that arose out of the PhD:
As for the book Rowland has written, "The Athlete's Clock", I can't vouch for the rest of it.  Hopefully, I will grab a copy at some stage, and then I can post properly on it!  But it's great to see a book reaching a wider audience on this topic (but then I'm biased!).  It also makes me think I should have written this book first!

Upcoming attractions

So I confess that this was supposed to a short "filler" post, just to keep the fire burning until the next big post.  I guess doing a "short filler" post on a topic as large as this, especially one to which I devoted years of research, was always impossible!  Apologies!

When that next post comes (hopefully later this week), it will be on the biological passport, which received a huge boost recently when the Court of Arbitration for Sport (CAS) ruled in favour of the passport by suspending two riders for "suspicious blood values".

The bio-passport has come under fire lately, because of what is perceived to be an inability to catch riders who cheat using all kinds of clever methods like micro-dosing and masking.  I think it's important to keep in mind that it's early days, and that researchers are slowly developing the tool.  I believe it has already had enormous positive effects on the sport, and I'll explain some of its limitations and why they don't necessarily destroy its value.

So I'll look at this in more detail, combined with some great inside information on the passport from one of its experts, and where it might be headed, as well as some of the legal issues it may face.

Also, stay tuned for some exciting news from Jonathan's life, and what it may mean for us here at The Science of Sport!

Until then, pace yourselves!


Dominique said...

Hi! This is a nice read. Your article is very helpful for aspiring runners who wish to improve their performance. Keep it up.

PS. I can't see your Disqus system, so I commented here.