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Thursday, May 01, 2008

Fatigue and Exercise Part I A

The pacing strategy - why the "obvious" is crucially important

On Tuesday, we introduced a new series on Fatigue and Performance, which, based on the comments and responses so far, promises to provide much food for thought, interesting discussion and a few strong opinions!

And thinking about the subject (see my thoughts at the bottom of this post), it's clear that the most difficult part of this whole series is going to be controlling the logical flow of the discussion. It's such a vast, enormous topic that it's going to be impossible to put across a vast amount of information without skipping over studies that some might consider relevant. That's the nature of science - if not, then every review article would have thousands of references! So literally, ten years of academic debate and research studies have to be translated into a (hopefully) understandable and readable summary! The only way to combat this is to stick to the plan we laid out two days ago, and so that means that many of your questions and comments might be quite relevant, and there will be "gaps" in the logic of each individual post, but hopefully, they'll all be answered eventually.

So with that on the table, knowing where to start is perhaps the most crucial thing of all - the first step on the journey (warning - it's quite a long post, so I have split it into two parts - the first is published today, the second will be published tomorrow! But you might want to read it in "shifts"!).

And I thought that perhaps I'd return to yesterday's post and the question I posed about pacing strategies and the mechanism for their existence. Today's post, then, is all about the pacing strategies, which are simultaneously the most obvious, the most complex, and the most important thing about fatigue and exercise performance.

What do we mean by pacing strategy? And why is it obvious? And important?

Yesterday's question involved pacing strategies, which anyone who has ever done exercise knows all about. In particular, we spoke about the "endspurt", which is the characteristically observed "kick" for the finish line in a race. I posed the question that if the athlete has the "reserve" to be able to speed up at the end, then what was keeping them from using that reserve earlier, and potentially running faster? (In hindsight, I probably could have chosen a better illustration of pacing strategy because people tend to dismiss this profound question rather frivolously, but there's plenty of time for all those questions to be asked!)

Take a look, for example, at the following two graphs. They show the power output during cycling (on the left), and the running speed during a 10km race (on the right):

This pacing strategy is, incidentally, typical of even the elite athlete. To let the cat out of the bag, the graph on the right belongs to a world-record performance - it is the 10km performance is that of Haile Gebrselassie when he ran his 10,000m world record of 26:22.75 in 1998. His final kilometer was run in 2:31.3, compared to high 2:37's and 2:38's before that. So even the greatest of the elite follow a similar strategy as a club-level cyclist - faster start, slowing in the middle, with an endspurt to finish. Obviously, the size of the difference is important, and the elite performance shows less variation than the club-level performance. Later in this series, when we discuss pacing strategies, we'll get to that in greater detail.

A "ridiculous" question with an obvious answer?

But let's get back to that question - Why the slow down in the middle, with the endspurt at the finish line? And what keeps the athlete from accessing the "reserve" sooner than the final kilomter?

Many say it's an irrelevant, absurd question, with an obvious answer. They dismiss it out of hand. Some of the typical responses are:

"It's obvious, because they know that if they ran faster early, they would not finish. It's training and experience, what a stupid question!"...or;

"It confuses me. To me what they are describing as "anticipatory regulation" is simply wise pacing." or;

"How can this question even be asked? Any person that has run seriously would not even ask it surely." The second and third responses are actual responses to this question, incidentally.

These answers reveal two things:

Academic exercise science is often quite far removed from "common sense",

Yes, it is actually obvious that people would speed up at the end. I'll never forget that having freshly graduated with Honours in Exercise Physiology, I was trying to explain to a very successful coach (Olympic champions in his group) the physiology behind performance. Having done my best rendition of the "truth", he nodded and said "Yes, well, we've known that since the 1970's, haven't we?". And he took me home, showed me a coaching book with worn pages saying pretty much the same thing...a humbling experience, to be sure!

However, as I thought about it, I realised that firstly, there was very little new under the sun (to quote Ecclesiastes) and so some humility was never a bad idea! But secondly, it was obvious that while people in coaching have always appreciated this endspurt and its meaning, those in the sciences have pursued quite a different course, developing a model that is incomplete and ultimately unable to explain this "obvious" endspurt!

We'll work towards explaining all that, but what people don't realise is that in exercise physiology, the usual explanation for fatigue is completely irreconcilable with this endspurt observation!
So the answer, which might be obvious to athletes and coaches actually has no feasible explanation in academia!

So what is that irreconcilable theory?

If you spent time studying exercise physiology, you would be taught that fatigue is caused by metabolite accumulation/depletion, high body temperatures, or some other peripheral change, as we introduced yesterday. This suggests that fatigue (or slowing down - even the definition is contentious) is a result of some change in the muscle. You may have heard, for example, of the theory of leaky calcium channels. In this theory, fatigue happens when muscle becomes "leaky" to calcium, which lowers the contractile capacity of the muscle.

I'll go into this theory much more in tomorrow's post, but consider that this theory suggests that you'll be slowing down progressively during exercise as your calcium channels become more and more leaky. Why then, would you not simply use muscle fibres that were previously inactive in order to maintain the speed? The "endspurt" which is often dismissed as "wise pacing" shows clearly that those muscle fibres were available. Yet the athlete "chose" not to use the reserve until the very end, rather getting slower or holding the pace. Conscious? Yes, probably part of it is, but what is the physiology behind this? The athlete knows that if they don't slow down, they'll become even more fatigued? But the "fatigue" is in the muscle, how do they know this? There has to be a signal, and how do leaky calcium channels fit with the conscious decision?

The point is, from the perspective of some biochemical cause of fatigue, the "obvious" pacing strategy becomes very difficult, even impossible, to reconcile and explain. In that sense, you have to be "priviledged" enough to become "educated" before the obvious question becomes relevant! That's a problem with academia sometimes - can't see the wood for the trees, but hopefully understanding this question and its answers reveals some useful information for performance.

But, more importantly, those dismissive answers mentioned above reveal that:

2. We're still failing to acknowledge the mechanism for this observation.

It may well be a conscious decision to speed up and slow down - "wise pacing" as people say. But apart from the fact that I'm not convinced it's simply a "decision", this is also not a mechanism, it's a description. When people dismiss the question as irrelevant or obvious, and say they know the answer, they never really give it, because the mechanism requires that we explain HOW the athlete knows to slow down?

And it's not enough to simply palm it off on "training" and "experience"! HOW does training alter pacing? How does experience influence the decision to slow down and speed up? Based on what INFORMATION is the "decision" made - time, distance, memory, pain? If you can honestly say that when you ran your last 10km race, you were consiously comparing it to the one you did in March, I'll take my hat off to you! So yes, I acknowledge it's pacing, but have you ever wondered how pacing is achieved? That's the question here, and I hope that this post so far has demonstrated that a biochemical cause of fatigue is not compatible with pacing.

Speaking of the "decision", is it conscious, or sub-conscious, and does it matter? In other words, does the athlete literally DECIDE to slow down through a process of rationalization and discussing it with himself: "Mike, time you slowed down now, because if you don't, you'll be in trouble at the 8km mark". But again, HOW does Mike know this? Or does something else cause that slowing down via an independent mechanism the athlete is not aware of?

The key concept - a co-ordinated system with INPUTS and OUTPUTS

All relevant questions, but the one with most merit is this:

What cues, what signals, what experiences, what training, and what physiology are responsible for enabling the athlete to consciously slow down in the middle, and then speeding up at the end of a race and still optimize performance?

Remember, the athlete is still running as "fast as they can" for the distance - Gebrselassie finished his 10km race having gone as fast as he could, just as you probably did in your last 10km race. So you finished, having balanced the requirements to avoid any limit to exercise with the requirement of running as fast as possible. Here, we have to also make mention that some people don't get it right - they start too fast, or too slow, fail to finish, and we'll discuss why that happens at some stage. But in general, most people, if left to their own devices and time-targets, will come very close to running an "optimal" race while still avoiding the physiological failures we introduced yesterday!

And here's the crux - the pacing strategy is the OUTPUT, the work done by the muscles, which are instructed to contract by the brain. But in order to produce this conscious decision to modify the OUTPUT, something (in the brain, you'd think?) must be taking into account a wide range of INPUTS in order to generate that conscious decision.

So, far from being dismissed as an obvious conscious decision, understanding the pacing strategy is going to give us insights into two key physiological features:

1. Inputs which will consist of changes in the periphery that ultimately have to be defended or regulated. One can quite easily appreciate how changing these inputs might alter performance. Therefore, if training and preparation can alter performance through these inputs, then understanding them is incredibly useful. In this series, the most interesting input to look at is HEAT, but we'll also spend some time on ALTITUDE, DIET/ENERGY, and also DECEPTION, when athletes are "tricked" into running or cycling further or shorter than they expect.

2. Outputs, which are going to comprise the muscles, which must of course be stimulated by the brain - remember the sequence is that muscle contracts only when stimulated to do so. So when the athlete slows down, there are only two possible causes: Either the muscle is fatigued and cannot do its job any longer (the peripherial model), or less muscle is being activated. The analogy here is that if you and five men are carrying a Grand Piano, it gets heavier either because each of your six-man team gets weaker, or one or more of your team leaves, leaving the rest of you to do the work. You'd slow down in response.

3. The set of inputs and outputs must be interpreted, co-ordinated and responded to. I'm sure it's not difficult to appreciate that this job must be done by the brain, and not some "little green Martian" as some have sarcastically joked in previous discussions!

Now, if this sounds suspiciously like a homeostatic loop for all of you with some biology training, you'd be 100% correct! For those who don't know, "homeostasis" is just a fancy term for the system which maintains the internal "balance" of the body - signals in, outputs out, all designed to regulate the system.

Also, if you want to call this the Central Governor, that's fine. As I wrote on Tuesday, I'm going to steer clear of this term, because it is too easily misconstrued as a centre or a "black-box" with a specific location in the brain. It's not that at all - if you look at the ten paragraphs above, we've already introduced at least four aspects of it, which would involve perhaps four areas of the brain that could contribute, and so to pin-point one location is a futile task. So I'll go with "Anticipatory Regulation" for this series, and hopefully, this post has portrayed this anticipatory regulation as more than a simple conscious pacing strategy. That pacing strategy is in fact merely the output component of a very complex, very interesting physiological system.

Wrap-up of Part I A - more to follow tomorrow...

That's it for the first part of Part I. As I said, I'm mindful that these are "epic" articles, which might be testing your own "fatigue" just to read them! I do apologize, but hopefully you are able to break the article up and squeeze some time out to get through it. I'd rather be "longer" and more detailed than make the mistake of cutting out valuable information, so do bear with me! The one consolation for you is that because they take so long, I'll only post once every two or three days, so there's time to grind through it!

Join us tomorrow for the conclusion and an example of what we've discussed today, taken from exercise in the heat!


P.S. The paragraph below is just some musings after reading some rather heated responses to this kind of discussion - thought I'd issue a call for "open debate"! It's not crucial to read!

Last word: Debating the issues moving forward

Last night, I read through a discussion forum on LetsRun.com, where the topic of the "Central Governor" was being discussed. It was quite clear from this forum that the fatigue issue will attract its fair share of opinion, argument and debate. And that's fantastic - it is, after all, the reason for our existence! However, what I would like to request is that any debate be done with an open mind, regardless of which side you're coming from.

The discussion on LetsRun reveals a characteristic trait of people - they approach debates with their minds already made up, and little can convince them to even listen to any other possibilities - we're all that way, to some extent. Our goal with this (or any other) series is not to change minds or win people over, but rather to encourage the recognition that if your perception is ever shown to be incomplete or incorrect, then by listening to others, you may improve your own understanding enough to move nearer to the "right" answer (whatever that may be!).
The problem for many people is that the debate tends to rapidly degenerate into a situation where the facts are no longer discussed, and instead, abuse is hurled back and forth - let's hope that this series doesn't provide the platform to create this situation, as it did on the forum mentioned above!

So with the hope that it doesn't, and as I said in a response to a comment in the previous post, bear with us having to attempt to summarize literally thousands of articles and ten years worth of debate into a month-long series! Also, we're not here to indoctrinate, but to gradually work through a very complex topic, which, as I said, could literally be written as a dozen PhD theses (and has been!)


Anonymous said...

How do runners speed up at the end of a 10k race? Where does that extra energy come from?
My empirical and purely personal take is that the energy comes from adrenaline--the so called "Fight of Flight" response.
I can hear those footsteps behind me and I'll be damned if someone will outsprint me to the line. I can feel the adrenaline--it's like a shot of super caffeinated coffee. My legs lift, my heart races, the runner come abreast. Somehow, I find another level of energy, and beat him to the line. Not a first overall, just a small personal victory.
That adrenaline shot overides any other physiological factors, i.e. "Governors", that would regulate and enforce homeostatis. Could not this adrenaline factor be so strong that it would cause a heart attack in susceptible individuals--contra indicative of it's intended survival purpose? Mike McGrath

Anonymous said...

I'm going to steer clear of this term, because it is too easily misconstrued as a centre or a "black-box" with a specific location in the brain. It's not that at all - if you look at the ten paragraphs above, we've already introduced at least four areas of the brain that could contribute, and so to pin-point one location is a futile task.

Does this mean that different parts of the brain which process the "inputs", can see different pictures ? Is it possible for them to induce conflicting outputs based on different pictures ?

Great post, and well written up. Cheers.

Ross Tucker and Jonathan Dugas said...

Hi Mike, Vikram

Thanks for the comments. You're both on the money.

Mike, if we return again to the same theme of this post, which is MECHANISM, then the question we must ask based on your insight is "how does adrenaline work?". We'll get to some posts later that look at how certain other drugs act in the brain to "switch off" the sensations of fatigue and effort that we'll see are intricately linked to this regulation. So those drugs act in the brain in much the same way as adrenaline does. Add to this the fact that the brain now recognizes the imminent end of exercise, and so all the regulation is no longer required, and you have the ingredients for the finishing kick.

However, we'll get to that in time!

Vikram, you're probably right that different brain areas "see" different things, but whether or not you might confuse the overall response is completely beyond me! I would not even know where to begin, and I suspect the brain in many, many years from revealing that secret! An intriguing possibility, though, and it will come up again in the future!


Andrew said...

I'm GREATLY looking forward to this series - I've long been fascinated by the concept of a complete "human performance model" since my college days of racing solar cars. Humans are far more complex, too!

It seems that vikram has hit on the key point, that humans are a system with many, many control loops that interact a dizzying number of ways. There is no single "central governer" (and you are wise to avoid that term) but a collection of control loops each with their own purpose.

I'm impressed that you're trying to tackle this issue! You must feel like Marty McFly in Back to the Future when he plugs his guitar into Doc Brown's super amp, strums one note and gets blown across the room by the sound!

Ross Tucker and Jonathan Dugas said...

Hi Andrew, and thanks for joining the discussion on this topic.

Indeed one problem with science in general is that it tends to be "reductionist" in nature. By that I mean that scientists try to reduce the answer to their questions to one single item, be it pH or carbohydrate or temperature, etc.

As Vikram has hit on, in fact there are so many different interactions between many different inputs, and only in some situations is one small thing the real cause of something else.

So the challenge is to take a more integrated approach. . .but unfortunately this is not even what we teach students at any level, either in South Africa or America. Instead things are boiled down to one thing, which makes for a nice little neat picture---however as everyone here is beginning to see the picture is more complex than that.

Of course trying to describe this concept is difficult, but we will give it out best shot here and hope you continue in the discussions!

Kind Regards,

Unknown said...

Not to jump on the bandwagon or anything, but great post!

This series is really interesting (obviously), and I thought I would throw in my 2 cents. It seems that whenever you guys do a post on physiology, any contribution I make comes directly from the module I'm studying in school, so here are my thoughts from my nutrition module:

My professor tries to explain the use of fats and carbs during endurance exercise by quoting data that shows that in the beginning of a race you use mostly carbs, and as times goes on your body moves to using a balance of carbs and fat, but that later in the race if you speed up, you "switch" to using a higher ratio of carbs. While all of this is going on, you liver is trying to produce more glucose.

So my thoughts are that you slow down in the middle of a race b/c your body somehow knows you need to produce more glucose to keep going, and your "kick" at the end is your body knowing that you are just about done, so just use up the rest of the glucose, no worries.

Now, like you guys have said, the real question is how your body "knows" all of this. thanks again for the great post.

Ross Tucker and Jonathan Dugas said...

HI David and Andrew

First of all, to Andrew, what a great analogy! I watched the Back to the Future movies long ago, and I was very young at the time, but the one scence I do remember is the one you describe, so I can relate! This series is probably going to last weeks, if not months, and I have no idea how I'm going to do this comprehensively without losing the plot! But we should have fun being blasted across the room together!

Then David, the availability of fuel is exactly one such INPUT that I alluded to in this post. There is in fact some evidence of pacing in response to changes in glycogen availability, and that will come out in due course. But it's one of the better examples of a physiological system that influences pacing to prevent "damage". And the million dollar question, which I hope people are starting to ask themselves is "How does the brain know all this?".

In all the discussion threads I've read, the most common "criticism" of this whole argument involving pacing strategies is that it's "obvious". I appreciate why people think that, but I hope it's clear that it is far from obvious!

There are some studies that have looked at this, and we'll cover them in the coming weeks. But you're close to one of the theories - in fact, yours is something of a "spoiler" for a future post!


Anonymous said...

Hi Ross...
thanks for opening this up.

First thing about speeding up at the end of a race: not all runners do this, so I don't think this really contributes to the discussion.

It is quite obvious, at road races for instance, that a lot of runners get progressively slower towards the finish until they are just virtually staggering towards the finish line.

For those that do speed up and produce a kick, this is either the result of an intelligent pacing strategy or, as Mike says, is caused by a burst of nervous energy/excitement due to a) the presence of spectators screaming at you; b) getting involved with a last-gasp sprint with some runner who comes up alongside, or c) in Geb's case, (a) plus the realisation that he is seconds away from a world record.

Let's also throw in the fact that a lot of these finishing kicks/dying efforts are short enough to be alactic, so you're using a different source of energy than the Central Governor seems to be interested in controlling.

I mentioned "intelligent pacing". I think that too many academics haven't lined up for a race and noticed the de rigeur starting position of right hand poised to start the watch.

Runners are not racing in some sort of vacuum; they are massively aware of time, pace and splits, even if they are not wearing a stopwatch. Many of us wear GPS devices that give us a live read-out of pace as often as we want to look at it.

What I'm saying is that I believe that most runners adjust their pace consciously, according to what they think they can do. I'd suggest that very few just go out and blitz it. So there's not need for an unconscious Central Gov -- there is conscious control.

And as a case in point, take a different look at your example of Geb's 10,000m world record. Your graph is organized in such a way as to exaggerate the ups and downs in pace. In fact Geb's pace varied VERY slightly, just the normal cyclical rhythm of running produced by any animal as opposed to a machine. What you're missing is that his 5k splits for that 10k world record were 13:11...and 13:11.

Anonymous said...

Very thought provoking so far! I look forward to the rest of the series.

I think I'd take issue with your assertion that the pacing "profile" shown is "optimal", however. In other words, going out hard, backing off, and then speeding back up has been shown, in cycling anyway, to be less "optimal" than an even power output pacing strategy. In fact, I'd characterize your cyclist example as pretty poorly paced.


Of course, it helps to know ahead of time what the subject is capable of over that time period, and in that sense on-board powermeters in cycling can be invaluable.

Ross Tucker and Jonathan Dugas said...

hI Simon

thanks for the comments. I will say that every single point you have raised is valid, but it's going to be discussed in great detail as the series develops - the issue of pacing by numbers, of "alactic" regulation (which the brain is very much concerned with, in fact), the issue of competition and tactics - it's all in the pipeline.

I still think you're missing the point very slightly - you say it's intelligent pacing or a function of excitement. I would ask, as i have in this post: How does that work? For you still haven't come up with a mechanism, only a description. Yes, it's intelligent pacing, but does the athlete consciously think of a previous race before they slow down? I don't believe so - I believe the slow down occurs before the athlete "decides" to slow down, and then they become aware of it.

Think of a 10km or 5km race you've run - your starting pace, in the first 400m is usually pretty close to your "optimal" pace, and it's not because you're programming it on your GPS. Better example - think of running 800m reps in training. I'd bet you that if you took off your watch, and ran them "as hard as possible", you'd follow the pacing strategy that I have shown in that graph. You'd run the first couple fast, then slow down a little, then speed up for a fast number 5. I'm sure you can relate...

FInally, the issue of why that endspurt doesn't exist is a very interesting one - it's something that happens only in race situation,when other people are present, and the tactics of the race represent ANOTHER INPUT that influences pacing. This is also something we'll tackle in detail later on - the "social" input of pacing!

Thanks for the contribution!

Anonymous said...

I agree: this really is an important topic, one I have thought about a great deal since I first starting competing many decades ago.

Given that many/most runners do indeed speed up at the end of a 10 km race,

1. Ask now why it is that not all runners in the same race or at the same position in the field speed up the same; and, why a given runner may speed up more in one 10k race than in another in the same season, irrespective of his/her finishing position time, or fitness level or even degree of speed training at that time.

2. Reverse the question: are there runners who do not usually speed up in a 10km race at the end - or if they do, they only speed up marginally?

3. Apart from 10km, do runners speed up in all longer races: eg 10k to marathons, ultra marathons, six day events? What about the shorter races: 100m, 200m and 400m, 800m, 1500m, 5000m; 3000m steeple chase; 400m hurdles; high hurdles? What about the 60m indoor and the 20m beep test shuttle run? Thus, are the proposed explanatory models the same for all these distances as they are for the 10 km race?

4. How does sex, age, VO2 (max/specific), top speed, BMI, percentage body fat, flexibility, motivation, injury and other bodily variables affect speeding up for all runners over all distances?

What about the effect of:

5. ambient conditions - wind speed; high or low ambient temperature; humidity; solar radiation and indirect radiation from road surface, buildings etc; what about an uphill at the end of the race - how steep does it have to be before runners stop speeding up?

6. time of day (early morning, afternoon or late evening races)?

7. quality of the competition eg Olympics vs fun run? Heats vs final? Olympic marathon after 10000m (heats and final) plus 5000m (heats and final) - did Zatopek speed up over the last km of his Olympic marathon victory?

8. quality of other runners in race - peers, much slower, much faster?

9. extrinsic motivators - the roar of the crowd; home turf; significant others; prize money?

10. performance enhancing drugs?

I am not trying to make an already difficult question more difficult still - rather, that by considering the parameters or the boundary conditions of the phenomenon, as one must do when constructing any mathematical model, one gradually starts to learn much more about the likely nature of the underlying variables and even the way those variables may interplay. Certainly, any scientific model must make it clear exactly what the model purports to explain: only Haile Gebrselassie’s 1998 10 km world record or does it purport to apply more widely? If the latter - how widely? What are it's likely limitations - that is where it is less likely or more likely to apply (see above 1 -10).

Mike LaChapelle said...

Have you done any studies on the impact of going out too fast in the beginning of a race vs. overall finish times?

Certainly, a early pace that is 1 second faster than an even pace is worth more than 1 second lost to fatigue at the end of the race. Is it worth 2 seconds?

Can you take the splits from an unevenly paced race and predict what the runner should be able to do in an optimal evenly paced race?

Anonymous said...

Hi Mike,

Excellent question, and thanks for joining in here.

In fact Carl Foster (currently at the University of Wisconsin-La Crosse) did a study examining just that.

They had trained cyclists do five, two km time trials. They forced the cyclists to use different pacing strategies so that the first half accounted for 55% d(a "slow" start) up to 48% (a "fast" start) and a few trials in between.

According to the abstract (sorry, the study is from 1993 and no pdf is available) the strategy that yielded the best performance was the "evenly paced trial" in which the first km was covered in 50.9% of the total time.

I cannot draw the graph here, but this is a quote from the abstract:

The starting pace to final time relationship was described by a U-shaped. . .curve with the nadir for final time at a starting pace of 51% of best total time.

So imagine performance time on the y-axis, and 55%-48% on the x-axis. The low point of the curve falls at 51% (actually 50.9% according to the abstract value).

They conclude:

The data support the concept of relatively even pacing in middle distance events with negative consequences for even small variations in this strategy.

Foster and his group have done some other pacing interventions, but I am not 100% familiar with the details of those studies and will have to scratch around on PubMed to read them.

Another study in 2006 by Gosztyla et al. looked at pacing in 5km running trials in women runners. They forced them to run 3% and 6% (about 13 s faster for the first mile) faster for the first mile than their normal pace.

However this change in pace did not result in any differences in performance time. Therefore they conclude that one can start off 3-6% faster than your normal pace and not suffer a performance decrement.

So the little evidence that is available suggests that at least over very short efforts (<20 min) a "fast-ish" start does not appear to affect your performance.

The question remains whether or not a faster start might impact your performance, say running maybe 10% or more faster for the first mile.

Kind Regards,

Anonymous said...

As other bloggers have mentioned running has a variety of "external" factors. Swimming is different - it would be interesting to see the splits of a 1,500m swim - no doubt the pace will be alot more even as it is alot more difficult in the water and alot more "punishing" if you "push" too early or sprint too late.

The Sports Scientists said...

Hi Anonymous, and thanks for visiting The Science of Sport.

In fact you can find the splits for the men's 1500 m swim here.

A quick cursory glance does reveal what you say---it is a very even paced event, with the winners and most swimmers not even speeding up over the last few lengths.

Of course this might also be a function of the competition---often times this race is not so close and therefore there might be less reason to race against someone in the lane next to you as effectively the race is wrapped up somewhere in the middle of the distance.

Thanks again for the comment!

Kind Regards,

Unknown said...

I just found your great site and appreciated it very much.

A short comment on the swimming over 1500m. The even pacing could stem from the fact that drag is a BIG issue in the water and the athlete is probably more likely to find a "comfort speed" that carries him/her all the distance. Also the performance has to be very controlled technically and loads smaller muscular groups? Are there relative differences in pacing during fixed durations of racing between other sports: skating, biking, running, rowing, swimming etc... Some peripheral feedback signals could be relative to the involved muscular mass and skill requirements?

jrb said...

Isn't it aerobic threshold during the race, then at the end you can access the anaerobic fitness, but for only a short period before all the ATP is used and the resulting lactic acid builds up.

Tom said...

I have a possible at least partial explanation for the "end spurt". It is obviously only a theory and please tell me any flaws you can find in it. Fast twitch muscle "anaerobic" fibres can't be utilised earlier, because they would fatigue too quickly. The largest motor units are recruited last and the fibres in one motor unit can't be separately activated, so you cant use "distribute" the use through out the race, therefore they are left for last.