Welcome to the Science of Sport, where we bring you the second, third, and fourth level of analysis you will not find anywhere else.

Be it doping in sport, hot topics like Caster Semenya or Oscar Pistorius, or the dehydration myth, we try to translate the science behind sports and sports performance.

Consider a donation if you like what you see here!

Did you know?
We published The Runner's Body in May 2009. With an average 4.4/5 stars on Amazon.com, it has been receiving positive reviews from runners and non-runners alike.

Available for the Kindle and also in the traditional paper back. It will make a great gift for the runners you know, and helps support our work here on The Science of Sport.

Thursday, September 30, 2010

Contador tests positive

Alberto Contador tests positive for clenbuterol - thoughts and conjecture

By now, most of you will have heard the news that greeted me as I woke this morning, that multiple Grand Tour champion Alberto Contador has tested positive for Clenbuterol during this year's Tour de France victory.  The reaction has been swift - Contador apparently heard of the result on the 24th of August, so one can assume the wheels have been turning furiously for both him and the anti-doping lab that detected the substance, and so it's no surprise that there are already many theories, discussions and possibilities around what has happened.

I haven't the time to delve too deeply into it right now, and besides, it would only repeat what is already out there.  So to save you some time in searches and your own reading, here are some of the more interesting pieces, that explain what might, or might not be going on:

Contador suspended and UCI statement

A report which contains the UCI's statement on the case, in which Contador is suspended pending further scientific investigation.  They release the level of clenbuterol in the sample as well, which is interesting only because it does give weight to the defence that is being put forward by Contador.

Food contamination: valid reason or overused excuse?

That defense, that the positive test is the result of contaminated food, is discussed in more detail in this article, which includes some quotes from Prof Don Catlin, one of the eminent anti-doping experts.  The interview with Catlin clearly took place before the UCI announced the level of clenbuterol in Contador's sample, because Catlin says "Without knowing what the level [of clenbuterol] in his sample is, it's impossible to say [whether or not food contamination is a viable explanation]".

I'd be interested to hear Catlin's views now that the level of 50pg/ml has been announced. 

Medical opinion on the concentration

There are other expert views on the level, however.  This report, prepared by Dr Douwe de Boer, contains a fairly systematic explanation of clenbuterol, what it does, how contamination might occur, gives a handful of examples of previous cases or reports of food contamination, and it mentions the specifics of Contador's case.

The report focuses very heavily on the concentration of clenbuterol in the urine in various cases.  For example, it is mentioned that cases of food poisoning which produce symptoms usually occur with a concentration of around 9 ng/ml, or 200 times greater than Contador's level.  The article also explains that WADA requires that its accredited-laboratories must be able to detect Clenbuterol at a level of 2ng/ml - this is referred to as the Minimum Required Performance Level (MRPL).

Contador's level was significantly lower than this, but before there's confusion, it's important to point out that clenbuterol is not a drug for which there is a detection level (or an LOD, Limit of Detection).  In other words, a "adverse analytical finding" (or positive test) is not declared only when the level reaches a value of say X.  If there is clenbuterol in the sample, then it's an adverse finding.

However, it's also mentioned that for some drugs - stimulants, narcotics and B-blockers - it is recommended that WADA labs do not report values below 10% of the MRPL.  Clenbuterol does not fall into those classes, and that's why the finding was reported despite falling well below that 10% level.

The implications of Contador's concentration, which is 40 times lower than the MRPL (not 400 as the UCI report is saying) are two-fold:  First, another laboratory might NOT have detected it, depending on how that laboratory compared to WADA's requirements for it to detect a given level of the drug.  And second, there's a question over whether any concentration should in fact constitute an adverse finding, or whether clenbuterol should be treated like those other drugs.  That would require the policies to be revisited, but would have resulted in Contador's test going unreported.  This says a great deal about the "grey areas" of doping control, but it's important in this particular case.

Contador's specific case details

The report by Dr de Boer goes on to describe when the positive tests occurred (on page 7 of the report).  Basically, Contador is tested on six consecutive days - July 19th to July 24th.  The tests on the 19th and 20th find no trace of clenbuterol.  On the 21st, the level is 50 pg/ml, it falls to 20 pg/ml on the 22nd, and then none is found on either the 23rd or 24th.  Based on these findings, and the half-life of clenbuterol, it is concluded that the clenbuterol was administered (either deliberately or via food) after the 20th.

Dr de Boer's ultimate conclusion is that the level is so low as to offer no performance enhancement, and fits with the explanation that contamination by the ingestion of meat is "extremely likely".  At this point, it's worth nothing that the report was commissioned by Andy Ramos, acting as Alberto Contador's attorney.  That doesn't discredit the argument, of course, but it's not entirely independent either - you can detect the bias as you read the report (we've had this debate over expert testimony before on this site!).  Ultimately, though, if the science is accurate, then the bias in how it is interpreted is largely irrelevant, and I don't know enough of the pharmacology to really dig into that aspect, unfortunately.

Some other thoughts - what is natural variation in clenbuterol?

The first thing that jumps out at me, as has been the case for most of the people spoken to, is the incredibly low concentration.  Another lab might have missed it altogether, while policy for some drugs is to not report if it's as low as this particular concentration.  Also, the positive test on the two middle days of a streak of six consecutive days supports the contamination explanation, though it wouldn't be the first time an athlete has tested positive once only.

Then there's the impact it would have on performance - almost none, and given how advanced doping practices are, it seems a foolish risk to take this particular substance (it wouldn't be the first time of course).  Also, there are better drugs for the same theoretical effect.

I think what would be most instructive in resolving this particular case is a massive research study (I'm thinking hypothetically here) in which hundreds of people (who eat meat) are tracked over many weeks, and their clenbuterol levels are monitored daily.

Obviously, clenbuterol is not supposed to be the urine - that's why the presence of even tiny amounts is marked as an adverse analytical finding.  It's not like other hormones that are produced endogenously and therefore are present.  But the point here is that if food contamination is a viable excuse (and based on the report, it has happened before, to the point of poisoning), then one would need to establish a safe baseline.  Perhaps every single person's clenbuterol levels do 'spike' by 0.05 to 0.5 pg/nl when they eat meat from certain areas, because of farming practices?  That's only really possible to know if you measure it and obtain some kind of "benchmark". 

The reverse approach, of course, is to ask what kind of concentration would be expected if an athlete does ingest a tablet?  Let's say Contador did take a tablet after the July 20th test.  What would have to happen in order to return a concentration of 50 pg/nl?  How much clenbuterol would that tablet contain?  Is it possible to 'hide' the ingestion of a larger amount through dilution/diuretics?  Would the level fall away to zero in only two days if a tablet was the source?

The transfusion possibility

The final possibility, which I'm adding to this post based on discussion below, is that the clenbuterol was taken many months ago (for either weight loss or to increase lean mass), then Contador's blood was drawn, frozen, and the clenbuterol found its way into Contador's body during the Tour as a result of the re-infusion of that stored blood.  This is what many alleged happened in the case of Landis and the testosterone.  It's certainly possible.  There are some questions, however.  One is whether clenbuterol 'survives' in stored, frozen blood for months.  Let's say Contador takes a significantly larger dose in the build-up to the Tour, and then extracts that blood.  What fraction of the drug would be expected to remain before it is re-infused, presumably on July 20th or July 21st?

And related to this, how much blood would be re-infused - Landis' allegations confirmed the notion of micro-doping, and so it's possible that very small infusion volumes to avoid detection would also produce a very small increase in clenbuterol detected in the urine.  Of course, if clenbuterol does NOT last in frozen blood, this argument is irrelevant - that's something for pharmacology to answer.  If it does persist, then what concentration of clenbuterol and what volume of infused blood would be required in order to produce this positive test at the concentration measured? 

The transfusion explanation is certainly looking more and more likely, at least as the main counter-argument to the contaminated food theory.  It will be interesting to know whether biological passport data was collected, and whether there is any indication of 'altered' profile on the dates in question - I am sure many will remember that Lance Armstrong's blood data from the 2009 inspired much debate because there was evidence (not proof) of unusual changes.  The same kind of change in Contador's samples would tilt the argument heavily towards the transfusion explanation.

What happens next is the "further scientific investigations" by the UCI.  I'm not sure what that entails either - perhaps they obtain their own expert counsel to produce a report similar to that written by Dr de Boer.  If those reports agree, then Contador's excuse looks valid and cycling's ability to enforce positive tests is again undermined.  If the reports differ, then cycling's current champion joins the army of previous champions consigned to the "doper" pile, which would drive another stake through the sport.  I'm not sure how either party can offer "proof" of anything in a case like this, but perhaps pharmacology holds the answer.   Time will tell...your thoughts are welcome!


Sunday, September 26, 2010

Live now - 5th Avenue Mile coverage

Fifth Avenue mile live coverage - Live Now!

As mentioned by Jonathan in yesterday's post, we're carrying a live feed from the Fifth Avenue Mile in New York City.  The men's race in particular should be a great race, with some big names including Bernard Lagat, Leo Manzano, Amine Laalou and a returning Nick Willis and Alan Webb featuring.

The race is live below - coverage is well underway, but the elite races get going at 18h50 SA Time, in just on 90 minutes from now.  If you are getting this message in your inbox, you've got literally 5 minutes until the men's race gets going, so check out the footage, courtesy the NYRR.

nyrr on livestream.com. Broadcast Live Free


Berlin Marathon splits live

Makau wins Berlin over Mutai, Kebede dominates

The 2010 Real Berlin Marathon produced a great men's race, and a dominant women's performance to kick off the fall marathon season.

Men's race - Makau over Mutai...again

On the men's side, it was a repeat of the Rotterdam Marathon, as Patrick Makau dueled with Geoffrey Mutai over the final 10km, and edged him by 2 seconds (it was 7 seconds in Rotterdam).  The winning time of 2:05:08 was just outside the Rotterdam performance, but it was hampered by very wet conditions on the streets of Berlin, and some erratic pace-making from one kilometer to the next - that may have been gusty conditions, it may have been puddles on the roads...

Nevertheless, it produced an enthralling race, which settled at about 15km, when it became clear that the world record was not going to fall.  The race opened up at 30km, and it was Ethiopia's Bizu Worku who did much of the early work.  He was rewarded for his efforts with a third placed finish and a PB, and at just 20, he's a name to look out for in the future.

However, today it was the two established names of Makau and Mutai.  Makau made the big decisive move at 40km, pushing through a 2:51 kilometer to shake Worku's resistance.  Then it was down to two, and in the end, with 200m to go, Makau had enough to see off Mutai.  There was no Martin Lel-like kick for the line, just a high sustained pace which Mutai was unable to follow.  Makau then, has run and won two major marathons, both in around 2:05, and he is now right up there as one of the great marathon racers.

As is typical, a lot of talk after the race about what might have been in better conditions.  It's a pity there is such a pre-occupation about time, though given Berlin's history, that's to be expected.  It was great to see a race in Berlin this year.

The race splits are below


Women's race - Kebede dominant 

On the women's side, it was Aberu Kebede who dominated the race.  After a very slow opening 5km (18:03), she threw down the gauntlet with a suicidal 3:08 kilometer (I must admit some skepticism about the accuracy of that time).  Only Bekele and Getaneh were able to to follow the pace, which soon settled at around 3:25 per kilometer.  That pace eventually saw Bekele and Getaneh dropped, and Kebede ran most of the final 15km all by herself.

Having been locked together with her country-women at 25km, her lead grew enormously from that point.  At 30km, her lead was 32 seconds.  At 35km, it was 1:03.  40km, she had 1:13, and that increase in the lead was testament to her dominance on the day.  And it wasn't as though she shifted into a higher speed - she kept producing 16:40-something 5km, the others dropped below 17 minute/5km pace.

Her winning time of 2:23:58 is a PB, just outside the best in the world this year, but given the slow first 5km, and the conditions, it's a great performance.  Bezunesh Bekele held on for second, while Ganet Getaneh fell backwards progressively and dropped out before 40km.  Third was eventually taken by Tomo Morimoto, just ahead of local favourite Sabrina Mockenhaupt, giving the locals something to cheer at the end.

Next up in the marathon season, Chicago, which should be a terrific (and fast) race!

But, before that, don't forget the 5th Avenue Mile later today.  The elite race starts at 12h50 ET, or 6h50 if you're in South Africa (CAT).  And we'll have a live feed of that race here on the site, so check in later and be sure to catch what should be a great spectacle from the streets of New York!

Thanks for joining our Berlin coverage!


Race commentary

For those interested, below are comments from the race, as I watched live.

Welcome to the live splits from the Berlin Marathon.  The race is underway in a misty, wet Berlin, and the next two hours should throw up some fascinating racing, with the possibility of a world record for the men.

We'll bring you the 5km splits, projected times and updated reports as it unfolds, so join us for an evolving story/post!

Men's Race

After a "conservative" first 5km, the pace shifted up substantially from 5km to 10km, and by 10km the projected time was below Gebrselassie's world record.  However, the pace has been erratic - 2:54 followed by 3:05, followed by 2:55 again, and that may be attributable to the conditions with very wet roads.  It may also be down to mistakes on the course measurements - the 19th kilometer was reported to be a 2:34/km, which is almost inconceivable.  Hopefully the 5km times are accurate!

The pace for the 13th and 14th kilometers has slowed significantly - both were outside 3:05.  That may be the weather - the course is very wet and perhaps the puddles are affecting the pace.  In any event, the record pace has drifted below the current tempo, and another shift would be required to bring it back.

At halfway, the split is 62:36, which is quite considerably outside world record pace, and the requested pace for today (which was 62 minutes), and perhaps it's time to call of expectations of a world record and focus rather on the race.  There are currently eight elite men in the lead group, surrounded still by about four pace-makers.  All the big names are still there - Makau, Kiptanui, Mutai.

At 25km, the pace has now seemingly settled at around 3:00/km, which means a good race is on the cards from about 30km, when the last of the pacemakers should step aside.   The elite group is down to seven - Bernard Kipyego is now 8 seconds down from the leaders.  It's building towards a fascinating battle over the final 10km.

At 30km, the race has finally taken its shape - Bazu Worku of Ethiopia led at 30km, after a very quick last 5km - 14:42, 2:56/km.  That pace shook all but three other men - a pacemaker, and then Geoffrey Mutai and Patrick Makau, the big favourites from Kenya, who are in familiar territory after their race in Rotterdam earlier this year.  The rest of the elite field are almost 20 seconds behind, and include Eliud Kiptanui.

Unfortunately, the weather has affected more than just the pace, it's also preventing us from getting continued footage of the elites, and we're watching a lot of 3-hour runners at the moment.  So those of you who are struggling to get the internet footage, don't worry - you're not missing too much.  I'm watching the feed and the splits are still the most informative source of information, which doesn't say much!

The men's race is still in the balance at 35km.  The pace has remained strong - under 3:00/km, and it's Worku who is doing much of the work.  It would be a major surprise if he is able to beat BOTH of the favoured Kenyans, and Makau and Mutai are still looking comfortable in second and third.  Makau has awesome half-marathon credentials, and has won in Berlin over that distance, so he'll favour his local knowledge and is probably the favourite, based on Rotterdam this year.  Anything could still happen...

38km, and the Kenyans have gone to the front.  Makau moved past Worku and threw in a small surge, but it hasn't done any damage at all to Worku, and still the three are locked together.  It wasn't an aggressive move, more just a change in leadership.  With just over ten minutes to run, something must surely give within the next five minutes.  The pace isn't too quick - 3:01 for the 38th kilometer, so it's become a little cagey.

39km - and Worku is once again pushing on at the front.  The pace hasn't increased - another 3:01 for the 39th kilometer, so it's more attritional than explosive.

40km, and the last 5km have been run in 14:56, which is not that quick.  At exactly 40km, Makau made a big move, and that move did finally shake Worku in third.  Mutai has responded, and so it's down to the big two Kenyans, a rerun of Rotterdam.  With 2km to go, they're locked together and this could be a fabulous final few hundred meters!  And we get to watch the women's race, now, of all times...having not seen it for 45 minutes, they cut to what is actually a boring race, at the expense of a duel to the finish line...

41km, and no change, with Mutai leading Makau.  Worku is about ten seconds behind.  2:52 for the 41st kilomter, and that was Makau's decisive move as they hit the 40km timing mat.  They might come close to 2:05 here...

Very aggressive running by Mutai at the front now, he's pressing very hard with 400m to run.  Under the Brandenburg gate and locked together - a great race in Berlin.  Makau hits the front now and is this the winning kick?  They're still looking at each other...no Lel-like kick from these two!

200m to go, and now Makau sprints, and Mutai will NOT respond!  It's going to be Rotterdam again, Makau wins by 2 seconds and Mutai is second, just as in Holland earlier this year!  Great race!  The winning time 2:05:08, a great time in the conditions, with a superb finish!

Bazu Work is third, in a big PB, but it's Kenya's day.  The women's race will provide consolation for Ethiopia...

Women's race

The women's race only got going at 5km, after a very slow first 5km.  Then the pace exploded - a 3:08 kilometer, which is suicidal in the marathon, followed by a series of 3:30 kilometers.  The pace is now projecting a mid 2:20, which will be good going in the conditions. Three Ethiopians are in the lead - Kebede (who set the pace for that super-fast surge), Getaneh and pre-race favourite Bezunesh Bekele.

The pace has held for the third interval, and is now projecting a 2:25.  That projection is based on some very up and down pacing, with that very slow first 5km.  More likely, we're looking at a time in the range of 2:23.

At 20km, the time is 68:37, with a subsequent halfway split of 72:20.  The race is still being led by the three Ethiopians, and should develop into an intriguing battle over the final 15km.

A major development in the women's race at 30km - the consistent pace of high 16 per 5km has shed Bekele and Getaneh, and now Aberu Kebede is all alone at the front of the race.  Her lead is 30 seconds, and she's on course for a mid 2:23 time.  We've seen absolutely none of the race in the last 30 minutes, so if I could tell you where the gap was created, I would.  In any event, she has established what should be a decisive lead, because the others have slowed, rather than Kebede speeding up.  That suggests that she'll hold that lead to the finish.

2010 Real Berlin Marathon and 5th Ave Mile

Watch them live on the web

We are sorry to say we missed doing a preview for this year's Berlin Marathon, but personal and work commitments have silenced us recently.  Ross's work at the canoeing world champs in Poland left him in a hole back in Cape Town during his absence, out of which he has been digging himself.  On the other side of the pond the academic year has hit Jonathan with full force and coincided with the birth of their second child (another boy).  So just trying to find time for a post here or there has suddenly become a real issue!

But the preview for Berlin could have been summed up in short order---No Geb, and three (two of them young) Kenyans looking to show the running world they are not "one-hit" wonders.  All three contenders have run sub-2:05, and so on paper it has the potential to be a fast race (and not a time trial as we have seen the past four years).  The one with perhaps the most to prove is Sammy Korir, whom many of you might recognize as Paul Tergat's pacemaker in 2003 who nearly stole the show.  He lost to Tergat by one second but became the second runner to break 2:05 for the distance.  However before that race and since then he has managed to run "only" in the 2:08-2:10 range.

Of the other two, Patrick Makau ran 2:04:48 earlier this year in Rotterdam, where Geoffrey Mutai finished second to him only seven seconds back.  

The race starts at 8:30 AM in Berlin, so by the time many of you read this the results will already be up, but the good news is that no matter where you are in the world, you can catch it live on the web here.  It is a refreshing break from many other events that limit viewing to a specific locale.

And speaking of viewing races live on the web, the NYRR is permitting people like us and others to stream the event live on their site.  This is excellent forward thinking because it can only increase the exposure and help the sport.  The action starts early (9:00 AM Eastern time), but there is a full schedule of races in including age group races for the entire morning followed by the professionals toeing the line at 12:50 (Women) and 1:05 (Men) Eastern time.

So check the video for the 5th Avenue Mile below and the Berlin Marathon for a nice Sunday of racing action.  The mile race is filled with solid competitors, some of whom have much to prove (Alan Webb), with  others looking to maintain their notoriety (Bernard Lagat) while others trying to build on Beijing success (Nick Willis).  Don't forget to follow us on Twitter for live updates and for an alert on when we post our Berlin analysis!

5th Avenue Mile - LIVE stream starts at 9:00 AM Eastern

nyrr on livestream.com. Broadcast Live Free

Jonathan and Ross

Saturday, September 04, 2010

2 hour marathon physiology

The sub-2 hour marathon: What physiology will it take?

The other day, I did a post looking at the likelihood of a sub-2 hour marathon, inspired by an interesting article published in the Journal of Applied Physiology.  That was part 1, focusing on the historical evolution of world records, not only in the marathon, but over shorter 10km and 21km distances, because I'm of the opinion that a 2-hour marathon will only be possible when the 10,000m times and half-marathon times improve by at least 30 seconds and 90 seconds respectively.  So, contrary to the JAP paper, which suggested that the barrier would be broken in between 15 and 25 years, I think it will take many, many more years.

Today sees the promised Part 2, looking more at the physiology, and specifically the running economy that will be required in order to reel off 42,195 m at an average pace of 2:50/km.  It's a conceptual post, so bear with the length and the "unanswerable" questions.

And I must emphasize the point, picked up by some of you, that physiologically, our ability to separate a 2:03:59 from a 1:59:59 is limited.  Both performances are close to the "limit", and given that elite athletes are rarely tested and measured in the laboratory, and that the physiological variability is larger than the difference in performance we're looking for, you won't reach the end of this kind of discussion with a concrete answer.  However, it's an interesting process, nonetheless.

Running economy re-introduced

Way back in 2007, we did a short series on Running Economy, the first post of which can be read here.  Running economy is a measure of how much oxygen you use when running at a given (sub-maximal) speed.  The more economical the runner, the less oxygen is used, and this is crucial, because it is a characteristic of great runners that they are much more economical.

The graph below, which is redrawn from a paper by Foster and Lucia (2006), shows the running economy of a few different groups of runners.

Here, running economy has been measured as the volume of oxygen used per kilogram to run one kilometer (think of fuel economy in a car - one gallon takes you x-kilometers).  So, the Europeans shown by the pink line in the above graph are using approximately 210 ml/kg to run 1 kilometer.  You can convert this to the actual VO2 quite easily, if you know the running speed.  For example, at 20km/hour, 1 kilometer takes 3 minutes, and so these European athletes are using 70ml/kg/min at that pace.

The Africans, shown in red, are considerably more economical (this is one of the more interesting debates in physiology - there are obviously overlaps, but generally, African runners appear more economical than Europeans).  The VO2 of the Africans at 20km/hour is equal to 190 ml/kg/km, or around 63 ml/kg/min, about 10% lower than the Europeans.

Can economy and capacity predict performance?

So, knowing this, we can begin to project what kind of physiology is required in order to run a sub-2 hour marathon.  The method used is very similar to that used for cycling, when we looked at the power outputs achievable during the Tour de France in our recent Tour coverage.

There are of course assumptions that must be made, but as I tried to explain for cycling, if you make the "conservative" assumptions, you still produce an interesting picture of what is physiologically plausible.  This is an exercise in theory, not proof.  It is the first word in a debate, not the last, so bear with some assumptions and let's see what the picture reveals.

The assumptions

The first assumption that you have to make is what relative intensity an athlete can sustain for a given period, two hours in this case.

This is not too much of a guess for elite athletes, but it does vary considerably with training - an elite athlete is usually able to sustain running speeds that require about 85% - 90% of VO2max for about one hour.  Marathons are usually run at an intensity corresponding to approximately 80% of VO2max, while 10,000m is run at around 95% of VO2max.

So for a two-hour marathon, we can make the assumption that the intensity will be equal to between 80% and 85% of maximum.

Next one has to assume VO2max, the "capacity".  This is more of a lottery, because the range, even in elite athletes, can be quite wide.  Zersenay Tadese of Eritrea was measured at 83 ml/kg/min, but some elite runners have been measured as low as 70 ml/kg/min (the reason they are still competitive, incidentally, is likely due to exceptionally good running economy). 

And then finally, you must assume running economy.  This is the key assumption, because as the graph above shows, it varies quite considerably.  The east Africans have been measured as having running economies in the range of 180 to 190 ml/kg/km.  Zersenay Tadese was reported to be the most economical runner in history, using only 150 ml/kg/km.  This is so low that I'm actually skeptical about the value.  (For more on this, check out this post from 2007, and see later in this post)

Nevertheless, using three assumptions, we can create quite an interesting picture of what the sub-2 hour marathon runner will look like, at least in terms of his 'engine'.

The graph below is the first step towards bringing all three assumptions together.  It converts running economy into a VO2 (in ml/kg/min) at 2-hour marathon pace (± 2:50/km).

Obviously, this picture is only partly complete.  The next question to ask is whether an average VO2 of say 67 ml/kg/min for a marathon (at the running economy of 190 ml/kg/min on the graph) is reasonable or not?  Can an athlete sustain that intensity for the required 2 hours?  Obviously, this question is not answerable in theory, only through measurement, but we can get an idea of whether it is reasonable by asking what kind of maximal capacity is required for each of the above VO2 values to be reasonable.

The graph below attempts to establish this.  It estimates the VO2max of the runner for two conditions:  One is that the athlete is running at 80% of maximum intensity (shown in red) or 85% of maximum intensity (shown in green).

So, for a given running economy, you can now see what maximal capacity might be required, or vice-versa, given a VO2max, you can estimate the running economy required for two different conditions.

Two examples:  High economy vs lower economy

The white lines show 2 examples.  Example A is based on the measured economy of African athletes (including some Olympic medalists) who have a measured economy of around 190 ml/kg/min.  At 2-hour marathon pace, they use 67 ml/kg/min.  That athlete, running at 80% of maximum, must have a VO2 max of 84 ml/kg/min.  If they were able to sustain 85% (which I don't think is possible), they would have an estimated VO2max of 79 ml/kg/min.

Example B shows the European athletes plotted in the very first graph of this post.  Here, a running economy of 210 ml/kg/km requires a much higher maximal capacity; in this case, either 92 ml/kg/min (at 80%) or 87 ml/kg/min (at 85%).  The point is clearly that in order to run a sub-2 hour marathon, the athlete requires BOTH an exceptionally good economy, and a high maximal capacity.  I guess the third option is that they could get away with worse economy if they were able to sustain 90% of maximum for that length of time, but I don't see this as very likely (but not impossible).

The Zersenay Tadese example:  Something missing in the picture

So where does this leave us on the question of the sub-2 hour marathon?  On paper, or in theory, a two-hour marathon is possible because we have seen running economies of 180 to 190ml/kg/km, and we also see runners with VO2max values of 80 ml/kg/min.  According to the graph, a runner with these "characteristics" can run the 2-hour marathon.  However, I've yet to see the two together, with the exception of  Zersenay Tadese, with his measured economy of 150 ml/kg/min and VO2max of 83 ml/kg/min.  However, as I said earlier, there's something not quite right there...

Here's the problem:  With that kind of economy, Tadese would be able to run at a speed of 2:50/km while using only 53 ml/kg/min.  Think about that for a moment:  he is running at only 64% of his maximal capacity, at 2-hour marathon pace.  He would be jogging to the world record if that was true.

Even his 10km pace of ± 2:40/km represents an underperformance, because at that pace, he would only be using 56 ml/kg/min, or 68% of his maximum.  We know that elite athletes run at at least 90% of maximum for 10km, which means Tadese should be sustaining a VO2 of 75 ml/kg/min, which, given his economy, predicts a 10 km time of just outside 20 minutes!

Clearly, something is wrong with that picture.  I actually emailed Carl Foster about this a while back, to ask about it, and he graciously replied, but then my computer got stolen, along with that email.  So Carl, if you are reading this, feel free to chime in!  I seem to recall that it had something to do with the timing of measurements - Tadese's VO2max and running economy were not measured at the same time, and therefore using them together created a problem.  And this is crucial - when we make this kind of estimation, we're assuming that VO2max and economy are measured together.  And if they are, then the more economical a runner, the lower their VO2max is likely to be.

The VO2max-economy relationship

For this reason, the combination of high VO2max and exceptional running economy is likely to be very rare.  So, let's get back to that graph above - does the athlete shown by "Example A" exist?  Is there an athlete with such exception economy AND such a high VO2max?  Or is the athlete with that economy likely to have a VO2 max closer to 70 ml/kg/min?

That is a question I don't have the answer to.  What is clear though is that even now, the current world record represents physiology that is close to this theoretical picture presented above.  That is, the current record equates to a runner with an economy between 180 and 200 ml/kg/km and a VO2max between 75 and 85 ml/kg/min.  Both of these are reasonable assumptions, which would lead one to conclude that a sub-2 hour marathon is physiologically plausible.

However, as I emphasized in my previous post, it's not as simple as this.  First, there are other "limiting" factors - thermoregulation is one that has not been mentioned yet.  To run a sub-2 hour marathon requires significant heat loss to offset the heat production, and so the limit may well have little to do with oxygen use, and everything to do with the avoidance of hyperthermia.  This factor certainly narrows down the opportunities to break the world record, because only a cool day will suffice - Dubai, Berlin and Chicago have all produced days that are too warm in recent years.  As the 2-hour mark is neared, that becomes even more crucial, and that's a big reason why I don't think we'll see more than one, small incremental improvement every five or so years.

And then finally, I must stress that this 'pre-occupation' with VO2max and oxygen as the determinants of performance is only part of the picture.  Performance is the sum of far more physiology than just VO2max and economy, and that's why the best indication of whether that sub-2 hour performance will be possible is, in my opinion, to ask what the implications are for performance over other distances.  If the shorter distances don't improve, then the longer one is unlikely to, and you can go through this same exercise for 10km and 21km events and you realise that we're right on the limit of physiological performance.  Doping would shift that limit, yes, and perhaps training.  But I still don't see it happening within the next 20 years.

Perhaps I will be wrong...as always, your thoughts are welcome!


Thursday, September 02, 2010

Dear Sports Scientists: Will drinking fluids keep me cool?

Another look at fluid ingestion and temperature regulation

First, if you did not catch the NY Velocity interview with Ross, be sure to---Andy Shen and co do a great job over there and produce some excellent interviews.  Their site is a must read for any serious or enthusiastic cyclist, whether or not they reside in NYC.

Back in June I was very fortunate to present two sessions at the National Athletic Trainers Association annual meeting in Philadelphia, PA.  Both talks were about fluid ingestion, temperature regulation, and dehydration, and last week I received the audience feedback from the two sessions.  As usual the sessions produced polarized views on the subjects.  So I thought it might be a good time revisit this topic, one we have written about quite a bit on the site and in The Runner's Body.  After all, it is the end of summer, it is hot and humid, and plenty of people are training and racing in the heat.

The title of this post was not inspired by an email we received, but one of the core junctures where the two sides of this argument split is how much fluid is the right amount and why athletes should ingest it.  Nearly everyone will agree that ingesting fluid does have an effect on one's ability to regulate core temperature.  However one side of the argument is that athletes should try to maintain weight losses or lose less than 2% of their starting mass, while the other side feels ingesting fluid to thirst (which normally results in weight loss and some "dehydration") is the best practice.

Why ingest the fluid to prevent or minimize weight losses?  Well, some might argue that if we do not, we get too hot and this predisposes athletes to "heat illness."  The exact meaning and relevance of "heat-illness" is debatable and probably deserves its own post altogether, but the rationale for warding off dehydration by minimizing weight losses is that dehydration causes a rise in core temperature, and that causes heat illness, and that it might even cause heat stroke according to some.

The lit review (in brief!)

The evidence used to support the practice of replacing all or most of your weight losses comes from studies that control for the workload while asking subjects to run or cycle in hot and humid conditions.  The smaller scale studies measure weight losses (and sweat rates) and core temperature, the larger scale ones look at cardiac output and skin blood flow, among other variables.  This is good science, because if we permit our experimental subjects to speed up and slow down then suddenly we cannot determine what is affecting core temperature because now we have two independent variables (intensity and fluid volume) instead of one (fluid volume).  Therefore I am not slating those studies and authors and accusing them of bad science.  

The conclusions are that dehydration, as measured by weight losses, increases cardiovascular strain and results in an elevated core temperature at the same workload.  Fair enough, and as I mentioned earlier I do not think anyone, us included, will try to say that fluid ingestion has absolutely no effect on core temperature---it does, and these studies all demonstrate this effect.  And in fact their science is good, but it is the application of the conclusions that are bad.  In writing a scientific paper it is quite easy to wander off and begin to speculate about why you found what you found.  And it is at that point in your discussion that the reviewers let rip and often times sharply remind you to remain within the confines of your data and draw conclusions based only on what evidence you have available to you (i.e. your data)!

The issue with this topic of fluid and temperature is that the data are all collected within a strict set of conditions---as dictated by the scientific process--but then applied to every athlete (slow, fast, recreational, competitive, elite) in any situation (practice, race, fun) and any condition (cold, warm, hot).

Size counts

The size and magnitude of this effect is terribly small, however.  I try to teach my students in my stats class the difference between statistical and practical significance, and this is a classical exercise for this.  Take the absolute difference between the core temperatures at the end of a typical study, where the subjects exercise for up to two hours.  It is typically between 0.5-0.8 C, or maybe 38.x C in the fluid trial and <39.5 C in the no fluid trial.  Statistically significant?  Yes, most likely.  Practically significant or meaningful?  You are allowed to disagree, but I say "no."

And to follow up with that conclusion, the advice to replace fluids and prevent dehydration is dished out from this evidence even though none of the subjects in these trials ever report signs or symptoms of "heat illness."  So perhaps the real story is that even when we exercise in hot and humid conditions, our core temperatures rarely reach critical levels, and we cope with the additional stress just fine as evidenced by the lack of symptoms.  To me it begs the question, "Why are we telling people to follow this practice," because although there is a difference in temperature, it is small and not otherwise meaningful.

Ingesting fluid keeps does not keep you cool

Long ago, in an exercise lab far, far, away (ok, in Fort Worth, TX), some bored or motivated (or both) students were testing an athlete preparing for the Honolulu Marathon.  At the end of the heat acclimatization period, the runner did a performance run (80 min) at marathon pace (14-15 km/h, or  8.75-9.4 mph) and ingested quite a large volume of fluid (1.75 L) while we measured the rectal temperature response.  He did not ingest quite enough water to prevent weight losses, but came pretty close, losing only 1.6% of his body mass pre to post.

And by the way, the conditions in the heat chamber were 27.3 C and 60-65% relative humidity---the expected conditions on race day in December in Hawaii.  

So if the model is that you must prevent or minimize weight losses, and that you must do that to prevent an excessive rise in core temperature, and this model is based on the evidence I mentioned earlier, how does one explain the graph above?  According to that model, this athlete should be no where near 40 C since he lost only 1.6% of his body mass and was only minimally "dehydrated," yet after 80 min he is nearly to 41 C.  And herein lies a problem, because if some data do not support a particular conclusion, said conclusion must be scrapped and we must formulate a new one that incorporates all the available evidence.

Therefore it is not the fluid you ingest that keeps you cool, but as we have written here before it is your metabolic rate, or how hard you are exercising, that really predicts your core temperature during exercise.  Do not mistake what I am saying here, though---fluid plays a role, but only a very small one, and more importantly when we permit athletes to pace themselves they just slow down in the trials where they do not drink or receive very small volumes of fluid.  The result is that they reach the same core temperature at the end of the time trial, but take a little longer to finish.

For me the bigger message is that if performance is a desired outcome, if the runner wants to go as fast as they can, then they should drink to thirst.  Ingesting volumes that are larger than that have not been shown to produce faster performance times.  If performance is not important, the evidence from where I am sitting tells me that ignoring thirst and/or ingesting very small volumes of fluid will result in a miserable day out, but will not cause you to get heat stroke or collapse---two conditions that result from mechanisms other than changes in fluid balance.

If using a "hydration system" and lugging an additional 1-2 kg of mass during training runs makes you feel better, then please continue, but just know that you are not lowering your risk for anything by doing so.  The normal response is to replace less than what we lose, and it is perfectly normal and healthy to drink to thirst.

A look ahead:  Running economy and the marathon WR

Meanwhile, the Fall marathon season is upon us!   Berlin is around the corner and Chicago is boasting a super hot field that, under optimal conditions, is capable of a record.  Earlier we looked at the Joyner paper but left it before discussing what kind of running economy it would take to break two hours, so watch out for that analysis!