Running Economy Part I

The Zersenay Tadese study - the most economical runner ever?

Yesterday we introduced a new series, Running Economy, inspired by this study, which was published just last week in the British Journal of Sports Medicine. It makes a great start to a series that we'll build on next week, looking at the importance of running economy to performance.

We must of course make the disclaimer that just as VO₂max does not by itself guarantee performance, so too running economy is one of many possible variables, both physiological and psychological, that come into play when one tries to understand just what is goes into determining performance. But it certainly seems to be an important one...we spoke yesterday of the growing awareness of running economy as a crucial determinant of performance, and of how little is known about it.

So it is perhaps fitting to begin our series with the very latest work, and then we'll deconstruct the theories as we progress.

The Zersenay Tadese Study

The title of the research article that was published last week was "The key to top-level endurance running performance: A unique example". The researchers, based in Madrid, Spain, had access to Tadese, the World Cross Country champion who put an end to the reign of Kenenisa Bekele earlier this year. He then followed this up with a win in the World Half-Marathon championships, where he beat world record holder Sammy Wanjiru, running 58:59, in a race where some time may have been lost due to tactical manoevuring in the middle part of the race!

Zersenay Tadese is a class act. Regular readers will know that I (Ross) am a particular fan of his, and recently picked him to be the next world record holder in the marathon, when he eventually makes the move up from the track. I think he might even have a more successful marathon career than Bekele. And if he gets the preparation right, Beijing 2008 might also see him challenge Bekele on the track. So it was with some personal interest that we discovered this article, courtesy George.

Looking at the study, it is always remarkable to have access to such a uniquely talented athlete, clearly at the peak of his 'game'. It's always been one of the big barriers to understanding the 'eternal mystery' of the dominance of the Kenyans that they've never really been studied in their prime. Most of the published work done on the East Africans comes from the labs of Bengt Saltin, and while those runners were certainly talented, they were by no means the best Kenyans in their best condition. And of course, there's a potentially crucial difference between the Kenyan who can run 27:30 for 10k compared to the one who runs under 27 minutes! So the fact that Tadese was tested during the month leading up to the World Cross Country Championships, and that he allowed the results to be published is a great coup for the researchers.

So let's take a look at the results...

Blood hematocrit

The first finding of interest is the hematocrit, measured one week before the Championships. It was "only" 43.7%. I say "only" because in another endurance sport, cycling, I suspect that many riders would not even get out of bed on pull on their jerseys if it was this low! In fact, the value of 44% is pretty much in the normal range, considering that he was doing a moderate to high volume of training at the time of testing (about 150km/week).

The authors suggested that this measurement, together with other findings we won't go into here, indicates "no manipulations to artificially increase blood oxygen transport capacity", and "no artificial stimulation of erythropoiesis". I'm sure sceptics are out there (they'd hardly report it if his hematocrit was 58%, would they!), but we'll go along with that one. Let's get onto running economy.

Running economy

We introduced the concept of running economy yesterday, but it bears repeating. Running economy is a measure of how much (or little, as the case may be) oxygen the runner uses for a given, sub-maximal speed. In theory, two runners can have the same maximal capacity for oxygen use (called VO2max), and then the one who is more economical at the sub-maximal speeds is likely to be the better runner.

So there are two measurements we need to look at here. The first is the MAXIMUM - the VO2max. The second is the oxygen use at sub-max, which tells us how economical Tadese is.

VO2max

Zersenay Tadese's VO2max was reported as 83 ml/kg/min. This is a very high measurement, but that's expected of a world class long distance runner. When compared to other world class athletes, Tadese's value 'disappears' into the crowd. In otherwords, if we lined up a group of athlete's VO2max values and asked you to pick the the two-time World Champion based on VO2max alone, there's a good chance you'd be wrong! Just as you would have been completely wrong when you had to guess that Derek Clayton could run a 2:08 marathon with his VO2max of "only" 69 ml/kg/min.

Of course, when it comes to VO2max, there's a lot of hype around the measurements. It has become something of an urban legend, much like the size of the fish you caught on your last fishing expedition which gets larger every time you re-tell the story! So depending on who you believe, Greg Lemond had a VO2 max of 92.5ml/kg/min, the Cross-Country skier Bjorn Daehlie was at 96 ml/kg/min in the off-season, and the physiologist who tested him predicted that he'd be above 100 ml/kg/min when he was "fit"! We're pretty sure you can relate your own stories of this super-human measurement!

Incidentally, while we're talking super-human, the Siberian huskies who take part in Alaska's Iditarod Sled Dog Race have been reported as having VO2 max values of 240 ml/kg/min! Eat your heart out, Bjorn!

Running Economy

So now we move onto running economy.

First things first – we have to understand what they are measuring. They have measured running economy as the total volume of oxygen needed to run 1 kilometer. This is really important, because there is evidence, shown in the Figure below, that this total volume does not vary too much with running speed. In otherwords, regardless of how fast you run, you use more or less the same volume of oxygen to run 1 kilometer! Of course, there will be individuals who don’t quite follow this trend, and so some runners will become more or less efficient as they run faster, but in general, it stays similar.

Figure showing schematic values of oxygen cost to run 1 km in three
different population groups. Note that the data are schematic only,
and represent pooled values for the three groups. Note also the general
absence of a change in economy as running speed increases.
Redrawn from Foster and Lucia (2006)

Now this might be confusing at first (certainly took some figuring out from our side – it has major implications for our understanding of fatigue, actually), because you’ve no doubt heard that the faster you run, the more oxygen you use. And this is still true – the trick is to understand the units that economy is being reported in. This is illustrated in the following example:

Take a runner who runs along at 4min/km, and uses about 200 ml/kg of O₂ to run 1 km. If we look at his O₂ use per minute, then we work out that he is using 50 ml/kg/min (because it takes him 4 minutes to run that kilometer and use those 200ml/kg of oxygen). If our runner increases his speed to 3min/km, if we assume that his total oxygen to run 1 km remains 200ml/kg (again, we acknowledge that some people will differ, but generally, as the figure above shows, this is the case). But now, he’s only taking 3 minutes to run the kilometer (and hence use those 200ml/kg of O₂). Therefore, his actual use of oxygen PER MINUTE is now 67 ml/kg/min!

So in fact, the use of oxygen PER MINUTE goes up with running speed, but the use per kilometer remains relatively constant. This is important (and has MASSIVE theoretical implications, but that is for another day). The other thing about this figure is that it creates a number of questions – why are the East Africans lower than the Caucasians, for example? But that’s all for the later posts in this series. Let’s get back to Tadese.

Tadese has one of the lowest total volumes of oxygen to run 1 kilometer ever reported. In the article, the authors report the following “normal” values for running economy, measured as ml/kg/km (that is, volume used to run 1 km)

• Frank Shorter – 192 ml/kg/kilometer (running at 3:06/km)
• Elite Kenyans (including Olympic medallists) – 192 ml/kg/kilometer (running 3:00/km)
• Elite Caucasians (Spanish runners) – 211 ml/kg/kilometer (running 3:09/km)

• Zersenay Tadese – 150 ml/kg/kilometer (running at 3:09//km and at at 2:51/km)

The size of this difference is astounding. We do have reports of runners who have been tested in this range, but we just need to get permission to publish the results (we’re working on that!). But let’s put this into context:

• Tadese is running along at 3:09/km, which is a 2:13 marathon pace.
• He is using 150 ml/kg of Oxygen to cover each kilometer.
  
• If we now convert this to a volume per MINUTE, we work out that he is using 47.6 mlO₂/kg/min. This is absolutely astonishing for how low it is!
  

We cannot emphasize just how significant this is – quite what it means, and the implication thereof is something we will tackle in another post, possibly even another series (we don’t want to go off on a tangent here!).

What is wrong with this picture?

But just think about something for a moment – Tadese has a VO2max of 83 ml/kg/min, and he runs at 3:09/km using only 48 ml/kg/min. Therefore, he is using only 57% of his “maximum” at this speed.

There is good evidence that athletes are able to run for 2 hours at about 80% of their VO2max. Now, if Tadese did this, he would be able run at 66 ml/kg/min. Given his Running Economy of 150 ml/kg/km (which is 'relatively' independent of speed - see Figure, and was similar for Tadese in the two speeds he was tested at), this would mean he could cover each kilometer in 2 minutes 18 seconds! Even if his running economy worsened quite a lot and he used up 180 ml/kg/km (a 20% increase), he'd still have it in him to run 2:45/km!

Quite clearly, this is not possible. So either Tadese becomes MUCH LESS efficient as running speed increases (which is somewhat out of the ordinary, as the figure demonstrates - slight changes, sure, but not so large), or something else is going on - there's something wrong with this picture. We need to address this, but as I've said, that's another can of worms!

The inevitable disclaimer...

I have no doubt that people will attack some of the assumptions we’ve made, and so we might as well declare right now – “We know, we've made some assumptions here, the key one being that economy (as measured per kilometer) doesn't change with speed, but we use this to illustrate a potentially profound point for our understanding of what limits exercise performance”. Think about it – if you’re running along at 80% of VO2max, then you have the capacity to use more oxygen. Yet you don’t. So how then, can oxygen be limiting, as you’ve probably read many times? Interesting one that…but that’s for another day…

Explaining Tadese’s extra-ordinary running economy

So now we move onto a mechanism – how do we explain this unbelievably low use of oxygen? Well, the authors put a few things out there:

• Very efficient utilization of oxygen by working muscles
• Training
• Muscle fibre distribution
• Genetic Factors
• And then the big one, anthropometric characteristics. That is, they measured the mass and size of the calf and found that Tadese had a significantly smaller calf muscle than the Caucasian runners, who had Running economies of 211 ml/kg/km.

With that, which I’m sure many of you are thinking is a very generic set of reasons and mechanisms, we’ll sign off today! But that’s on purpose, because in our next post on the series, we’ll look at what factors contribute to running economy in more detail – what is training, muscle fibre distribution, genetics? And then we can all compare ourselves to Tadese and work out why we’ll never be that economical!

Bye for now!

Ross

Running Economy Introduction

Zersenay Tadese - the most economical runner in history?

Well, a provocative headline for sure, but that's pretty much what a SCIENTIFIC study has suggested after measuring the oxygen consumption and running economy of the World Cross Country and Half Marathon champion recently! The study, published just the other day in the British Journal of Sports Medicine, and performed by Carl Foster and Alejandro Lucia, found that Tadese has one of the best (if not THE best) running economies ever measured. That is, he uses LESS oxygen at the measured running speed than any runner reported before him.

I would not question the study for a second (well, not too critically, anyway), as Foster and Lucia are both excellent scientists, with great records in the field. Foster is famous for his modeling of pacing strategy and performance, while Lucia has been one of the leading researchers in cycling performance, doping and the physiology of performance. So some credible names, and a fascinating paper, for sure!

We are always on the lookout for interesting news stories here at The Science of Sport, and we do our best to take sports news and exaplain the science behind it. But this particular story is both newsworthy and science-worthy at the same time, and we say thanks to George (a self-described devoted reader of the blog) for bringing it to our attention!

Introduction of a new series - running economy

What we would actually like to do before we analyse this paper (and Tadese's new claim to fame) in tomorrow's post, is to use this really great story to introduce a new series and discussion around this concept of running economy. I seem to recall that about three months ago, there was a whole spate of articles on running economy - for some reason, it suddenly shot to prominence and a number of widely read newspapers started writing about it as though it was the very latest thing, even though we've known about its importance for about 30 years. And even back then, we considered the prospects of some posts about running economy, but they got kind of swept away by the heat of Chicago and the racing in New York. Well, no time like the present to go back there!

Running economy 101: What is the big deal?

To begin with, running economy in humans is probably analogous to cruising-efficiency in a car (not entirely, but we'll get there!). If you think of a human, we can measure the maximum volume of oxygen that can be used, and this is called the VO2 max or VO2 peak. The problem is, for most running events (certainly above about 5000m), runners don't use this "maximum" amount - they are sub-maximal. And so therefore, a more important measure becomes the volume of oxygen that is used up when the runner is going at a sub-maximal speed.

So to return to our fuel analogy, it's saying that the car is cruising along at a speed lower than maximal, and we're interested in how much fuel it uses per kilometer.

Now, there is plenty of reason to think that running economy is very important. There used to be a perception, which still exists in many circles, that the be-all and end-all of running performance was the VO2 max value. In other words, you'll still find people who think that the runner who has the highest VO2 max is the guaranteed winner. Many runners who have been tested wear their VO2 max like a badge of honour if it's high, whereas they hide it away if they think it's low, such is the importance that has been placed on this measurement.

And of course, it is still crucial that a world class runner have a higher than average maximum ability to use oxygen. So you'd be very hard pressed to find any world-class runner who has a VO2 max lower than about 70 mL/kg/min (this is the unit for VO2 max, by the way - it's a volume in mL, expressed relative to body weight over time). Your typical moderately fit male, weighing about 80kg, would have a VO2 max of about 50 to 60 mL/kg/min, and a fairly well trained athlete might hit the mid 60's, with the better ones being higher than this, into the 70's and 80's. So there is a "GENERAL" trend for the fitter, more highly trained athlete to have a higher VO2 max (although we would argue that is a consequence and not a cause of performance).

But then there's a catch - Maximum is not the deciding factor

The reality however, is that you don't always get this nice, uniform increase in performance with an increase in VO2 max - often times, a guy with a VO2 max of "only" 75 ml/min/kg will beat a runner whose VO2 max is "superior" at 85 ml/min/kg. And so clearly, there is more at play than simply the size of your lungs, your heart and the muscles maximum ability to use oxygen.

Intuitively, you recognized that this makes sense - as we pointed out above, because 10000m races are run about 90% of VO2 max, and marathons are run at 80 to 90% of VO2 max, there is room for difference because it's the runner's ability to use the oxygen most efficiently that contributes a substantial amount to performance.

So that's where running economy enters the equation. Whenever you read a book on this subject (be it Lore of Running, or any other text), you always see the concept of running economy introduced in this way - it's the excuse for the "little guy" (in terms of maximal oxygen use, anyway), beating the big guy!

Considering how important running economy seems to be, it's apparently been ignored in the literature. Last year, in October, a seriously high-powered gathering of exercise physiologists and scientists gathered in Chicago for a conference on Marathon Medicine and Physiology.

And at that conference, Carl Foster, one of the authors of the Tadese paper, discussed the role of running economy in performance. He suggested that the science has "ignored running economy" to date, despite knowing about it for 30 years, and as a result, relatively little is known about the topic.

It therefore seems like a nice, juicy and interesting topic to tackle in a series, and so what we'll do over the next couple of weeks is take a look at running economy. We'll begin with an analysis of the study on Zersenay Tadese, which began this post, then we move onto the importance of running economy, the factors determining running economy, and methods that you can use to improve your running economy, and hopefully performance.

So join us over the next few weeks as we get into what could be a very interesting discussion!

Ross

Fukuoka Marathon 2007

Sammy Wanjiru's debut party goes as planned

This past weekend saw the 61st running of the Fukuoka Marathon, which until a few weeks ago promised an epic dual between the seasoned veteran Paul Tergat and the up-and-coming Sammy Wanjiru. Unfortunately Tergat pulled out, leaving no one who could, on paper at least, touch Wanjiru's potential.

Wanjiru has been devouring competitors in the half-marathon since 2005, when he set his first world record over that distance (59:16 at Rotterdam). He lost that record to Gebrselassie in January 2006, only to break it again in February of this year in Ras Al Khaimah (UAE) with a new time of 58:53. However that record was not ratified as no EPO testing was carried out at the race. Undeterred, he promptly lowered that time to 58:33 in March at the Fortis City-Pier-City Half Marathon in Den Haag. He later committed to Fukuoka as his marathon debut and had all eyes upon him this weekend---could be break Evans Rutto's debut record of 2:05:50?

The race: Wanjiru never in trouble

It was a typical race of attrition as the pace setters did their job and one by one runners dropped off the pack. By 20 km only 15 runners remained in contention, and five km's later only 10 remained. At 30 km the rabbits' job was complete, leaving just two other runners to challenge the novice Wanjiru. At that point he and Japanese national Atsushi Sato tightened the screws and ripped off a few fast splits:

31 km: 2:58
32 km: 3:01
33 km: 2:57
34 km: 2:58
35 km: 2:52

It was Wanjiru himself who attacked during the 35th km, breaking Sato and leaving only Deriba Merga of Ethiopia. Wanjiru then toocontrol as he surged again to break Merga:

36 km: 2:56
37 km: 3:04
38 km: 2:57
39 km: 3:11

Merga was dropped, but hung on to smash his own PB by over six minutes and also borke the prvious course record and finished only 11 seconds behind the debutante Wanjiru. A stellar run by Wanjiru, to be certain, but very brave running by the young Ethiopian who showed class and form by clinging to Wanjiru for so long and losing by a relatively small margin.

The official splits for Wanjiru as he broke the course record by 12 seconds :

5 km	15:04
10 km	30:02
15 km	45:06
20 km	1:00:11
21.1 km	1:03:30
25 km	1:15:04
30 km	1:30:05
35 km	1:44:49
40 km	2:00:03
42.2 km	2:06:39

What is next for the young star?

So everything appears to be going exactly as planned for Wanjiru. He seems to be connecting the dots one by one from a very young age and turning in big performances along the way. Wanjiru claims to have Olympic Marathon aspirations, and so far has met his goal of debuting with a 2:06 marathon. His next goal is to run 2:05 in a spring marathon, perhaps London, in hopes that a feat of that magnitude will secure him a spot in Kenya's Olympic Marathon team. Another performance like this in London will signal his arrival on the Big City marathon scene. This past weekend, although matched against the best Japan has to offer, he did not run against such a stellar field. London's ability to secure both the fastest runners and best racers is legendary, and Wanjiru must prove he can beat the experience of guys like Felix Limo, Evans Rutto, Jaouad Gharib, Daniel Njenga, Robert Cheruiyot, Paul Tergat and Gebrselassie, among others. For now, though he owns the course record in Fukuoka and remains on a larger path to more success.

Muscle Cramps: Part V

What all this means for you

We have now run the entire gamut in this series on cramps, and it has been quite a ride. This series generated the more reader interest than any of our other posts or series, and let us say again how grateful we are for your participation in the debates and discussion. As academics, we hold fast to the old adage that there is no such thing as a stupid question, and all of us, expert or novice, must ask questions to learn and advance our own knowledge. And this was a complicated series, so we really thought it might be a good time to try to summarize what, exactly, does all of this mean for you the athlete?

Who experiences cramps?

There does seem to be a predisposition cramps. To date no one has even tried to identify the gene(s) that might predispose one to cramping, but even a general survey of the active population will reveal that some people cramp both at night and during exercise, while others never cramp. So you might indeed be a "cramper" before you even toe the line!

What causes them?

We have presented two models for the cause of cramps. The first model tries to explain them based on electrolyte disturbances and dehydration. The second model is based on neural activity and muscle excitation and relaxation. So which one is correct?

The short answer is that we do not know exactly what causes cramps, and it will likely be many years (perhaps even decades) before someone presents a more definitive model that better explains their cause. As we mentioned in a recent post, science is like watching one chess square and trying to create hypotheses based on observations of that one square. We have presented the available scientific evidence, and have drawn our conclusions based on that evidence. Does that make our conclusions correct? To be certain, "No not necessarily!" It merely represents our interpretation of the data.

The bottom line here is that it is a complicated mechanism, like so many others in the body. Also, just as our many different systems are affected by a vast array of factors and circumstances, so is the cause of cramps, and until we have a reliable laboratory protocol that can reproduce cramps in a predictable manner, we cannot really test the models further.

Ok, so I am a cramper. . .now what do I do?

There are a couple of key points here:

1. Regular stretching will help reduce the incidence of your cramps. This is because, as we explained in Part III, stretching will reduce the alpha motor neurone activity, and thus reduce muscle contraction---which is all a cramp is anyway, an uncontrolled contraction. Therefore stretching often is recommended especially if you know you are a cramper.
2. "I swallow an electrolyte pill and my cramping stops." This is a comment we hear often, and although we cannot explain this physiologically, the more important message is that you have found something that works for you. We cannot stress how important this is! All the science in the world can point to something, but if what you are doing works for you, then you are better to stick with that technique. We invest so much time and energy (i.e. blood, sweat and tears!) into our training, and if you know that taking some supplement---providing it is legal, of course---will prevent a cramp during your marathon, then by all means you must take it.

But wait. . .I am not a cramper, how can I reduce my chances?

Fatigue appears to be a common factor in cramps, and so preventing fatigue or delaying its onset is crucial. However, we can hear you all the way in Chicago and Cape Town saying, "Great! if only it were that easy. . why didn't you just say so?"

First of all, "Out running" your training could be a likely contributor to cramps. By this we mean that you know good and well that you have done the training for a 3:30 marathon, but in spite of that you decide you are going to go out at 2:55 pace. You feel great for about two hours, and then all hell breaks loose, the wheels fall off, and you are left in a crumpled heap with 5-10 km to go. Therefore we would suggest trying to race closer to your abilities in an effort to reduce the amount of fatigue you acquire during the event.

Second, progressive training is something else that we can all practice that will likely help reduce the chances that we cramp. Don't go from "zero to hero" and make large increases in your training from week to week. As many of you might already know, rest is just as important as all the intensity and distance work you do, because it is during rest periods that your body actually makes the adaptations. Therefore small and incremental increases in training with appropriate rest will provide your body with the maximum time to make the necessary adaptations, and it is those adaptations that will delay the onset of fatigue.

Physiology is a complicated topic, and the available evidence on cramps is sparse. To really advance our knowledge we need solid lab studies that help us identify exactly what is going on and why the cramps occur. In fact, just creating a reliable and reproducible lab protocol would be a major step in identifying what causes the cramps in the first place. However cramps tend to be unpredictable in most people, and even in the known "crampers" it is difficult to bring them in the lab and make them cramp 100% of the time. So the beat of science marches on, and we can only hope that even as you read this, some PhD student out there is hard at work dreaming up a thesis that investigates this issue and tries to advance our knowledge!