Testing Chris Froome: what does the physiologist who conducted the tests make of the data?

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Exercise physiologist Dr. Jeroen Swart has been front and centre in the news in the past few days, having played an important role in the physiological tests that Chris Froome underwent in London in August.

Those tests, carried out at the GlaxoSmithKline (GSK) lab, looked under the hood of the two-time Tour winner, giving an insight into his physiology and also attempting to explain how Froome went from being a rider with limited early success to a multiple Grand Tour winner.

CyclingTips spoke in detail to Dr Swart about this subject, about what other testing he hopes to do with Froome and also what else the Briton could do to show he is clean.

Part 1 – background to the test:

Jeroen Swart: Basically the start of this whole story was during the Tour, with all the fan abuse and all the questioning. The directive from all these sceptics was that he should undergo testing. At that point Michelle [Froome, Chris Froome’s wife and manager] was looking at various options, and for some or other reason she and Chris decided to ask me.

I had met him back in 2011 at the Supercycling show and gave him occasional advice via SMS about injuries since then.

During this year’s Tour I had put out a brief analysis in terms of the numbers and my predictions in terms of what VO2 would be required to do the performance that he did. It actually turned out to be pretty close to what he achieved [in the later lab test].

Michelle phoned me and asked me if I would be interested in testing him. I thought it was in relation to that, but she hadn’t even seen the post. It was just a coincidence that it happened around the same time. For various logistical reasons we decided on the GSK lab in London.

CyclingTips: Although many other professional riders have done VO2 max testing, Sky have said they don’t carry it out…

JS: I believe that is true. Sky do all of their data collection in training and analyse that instead. In reality, VO2 max testing doesn’t tell you very much, in terms of performance. In a homogenous group of elite level athletes, you can’t stratify them according to VO2 max.

Otherwise we could hold the Tour de France in the lab and the guy with the biggest VO2 max would take away the yellow jersey.

There are guys with supremely high VO2 max who don’t do very well, and vice-versa. Obviously there is a threshold above which you have got to be. To climb in the front with the top guys, 80 plus would probably be a pre-requisite. Where exactly that cut-off lies we don’t know because we haven’t a lot of data on the top guys. In fact, we have almost nothing.

This is probably the first data that we have got that is realistic. Some of the data that we have seen from the past, whether that is from Armstrong – and I hesitate to say Indurain and others – we don’t know if that is credible data.

Likewise, we don’t know with absolute certainty whether Chris’ data is entirely 100 percent credible. There is no way to prove whether or not he has used any performance-enhancing substance. It is just not possible.

CT: I guess if a rider is taking substances, that would also boost a VO2 max test?

JS: Yes, it will. So you can have a very good lab performance by taking performance enhancing substances, particularly in the case of VO2 max, blood boosters – EPO, blood doping, whatever it happens to be.

Related article | Blood doping 101 – how it works

CT: So the test is only a fraction of a whole bank of data that can give a picture of a rider’s cleanliness.


Dr. Jeroen Swart conducting physiological tests with Johan Rabie (Team Bonitas)
Dr. Jeroen Swart conducting physiological tests with Johan Rabie (Team Bonitas)

JS: What is your reaction to Chris Froome’s test results?

I wasn’t really surprised, knowing what is required to produce the kind of performances that he did. As I said, I had predicted roughly what VO2 max we would expect from him. And so it wasn’t at all surprising that he was in the 80s. The question was whereabouts in the 80s will he end up? Would it be lower 81, 82, or would it be a high 80s result? And that is exactly what he delivered.

So it was really confirmatory rather than surprising in any way.

There was a surprising bit of data. One is his peak power output relative to his sustainable power output… the value that we compare it is at 4 mmol of blood lactate power output. If you look at the studies that have been published, that is a value that coincides with what you can sustain for approximately somewhere between 40 minutes and an hour. And that ratio [with Froome] is under 80 percent.

So he is not riding at an extremely high percentage of his max. I thought it would be higher. With amateur athletes and a lot of elite athletes I have worked with, those ratios are sometimes as high as 85 or so. Whether or not he can sustain closer to 85 percent we don’t know, as we haven’t put in that particular workload and said, ‘okay, ride until you fall off the bike.’ Those sorts of tests are still possibly to come.

CT: What does that figure tell you?

JS: From the inference in terms of his blood lactate concentration, he can certainly ride at six watts per kilo at the weight we have tested him at. And if he managed to maintain the same power, and lose a few kilos to be at his Tour weight – and that is always a speculative thing, if he can do the same power at his Tour weight – then 6.2 watts per kilos for him is under 80 percent of max.

It is not astronomically…extra-terrestrial or whatever words they have bandied about. It is a very realistic power output for him to do. And vis-à-vis any athlete who has got a VO2 max in the high eighties

CT: If I remember correctly, when Chris did the test in August, he said more testing would be done. But then he crashed out of the Vuelta. Had he intended doing more after?

JS: Yes. The one test that I really wanted to do, which would have been interesting, is to use a telemetric gas analyser. Measuring his expired gasses on a bike on a sustained climb of at least half an hour’s duration, going at maximum effort.

In the lab, the duration of the activity is far to short to see what happens with the onset of fatigue and other factors. So a field test would have been a nice one to add to it, and at some point we will do that. Even if it doesn’t make it into this specific publication, Chris is committed to doing further tests for his own benefit and for transparency’s sake. I think this will probably be a series of tests over time.

CT: The South African sport scientist Ross Tucker mentioned that there wasn’t an efficiency value. Will that come in the paper?

Yes, it will come in the paper, and so will a whole bunch of other data. We did two tests in two different ambient conditions, basically step tests where each step was a longer duration that we did in the VO2 max test. In that test we measured core temperature, expired gasses, heart rate, blood lactate concentration, sweat production…there might have been other ones too.

That is quite a lot of extensive data. The interesting one is his performance in the heat, and that is something that will get published in the manuscript, together with a much more in-depth analysis of the other data collected during the VO2 max test, including efficiency.


Part II – what happens next?

According to Swart, the most likely timeframe for the publication of the journal article is like next March. Those involved in writing it up are working away at it, but it still has to be accepted by a journal, tweaks may have to be made and then it must be peer reviewed.

Separate to that, Froome will be working towards what he hopes is the third Tour win of his career. In fact, if things go to plan, he will also take one or possibly two Olympic titles in 2016.

One of his reasons for undergoing the lab testing was to address some of the sceptics. Thus far, that has been an exercise with mixed results. Many observers acknowledged that he had gone further than other Grand Tour champions in the past, but others felt that more complete biological passport data would have been advantageous in terms of transparency.

CT: You said earlier the lab test doesn’t tell you if a rider is clean or not. One thing that seemed a little surprising is that Chris and Michelle [Froome, his wife and manager] only released two blood values from this year. You could argue that a more thorough release of bio passport would have helped the case of transparency.

JS: Yes, it might, but it already creates an absolutely circus and that is the problem. Already, just releasing two blood values, [American sports physician] Mike Puchowicz is jumping on it and saying his haemoglobin after the Tour is the same as it was during the Tour, therefore he is doping.

That is ridiculous. If you have got two blood values, you have no idea what you are looking at in terms of the profile.

All that is going to happen if you release your entire biological passport is you are going to have armchair scientists around the world throwing all sorts of comments out and speculating.

It would be great if everybody took a scientific approach and had the expertise to assess it, but there is just too much of speculation and looking for evidence of doping rather than really looking at it scientifically.

CT: But as you say yourself, two data points don’t tell you anything. The whole point of this exercise is to show transparency, and so releasing more blood values seems important…

JS: Well, the first thing is I asked them to release the values on the day of the testing, because I wanted to ensure that the people didn’t think that he rocked up to the lab with a haematocrit of 53 or something like that. In other words, produced a performance to justify his Tour performance by having somehow blood doped.

In the past, a haematocrit in the low 40s in the past would have raised eyebrows from the rest of the peloton in terms of how normal they were. I remember ten years ago that the average haematocrit in the peloton was 49.

So I think it is a very normal-looking blood value and the reticulocyte count and the off-score also look very normal. So that is reassuring.


CT: I’m not trying to paint Chris into a corner, but Michael Rasmussen said that he when he was blood doping, he would ride the Tour with a haematocrit in the low 40s. In that light, do you think it would have been an option to give the whole bio passport to someone like Michael Ashenden or Robin Parisotto [experts at detecting blood doping – ed.]?

You could say to them, okay, you assess this, come to your conclusions and then just release that conclusion without needing to release all the blood values publicly?

JS: Yes, I think that is a fair suggestion. And it is something that I would certainly suggest to them. So releasing it to an expert to review and for them to provide an opinion, certainly. Releasing it into the public domain doesn’t really add value.

CT: Personally, I think the lab testing was a good step, but without blood data it’s hard to form a firm conclusion. So if it went to Ashenden or someone like that, it would be good in terms of reassuring people…

JS: Yeah, I absolutely accept your point on that, totally.

CT: Do you think other riders should make a similar gesture now and also release data?

JS: Yes, I think so. In an ideal world, I think every team should be doing is doing what Fred Grappe [FDJ coach – ed.] is doing, and that is having a longitudinal data set available on all the riders, particularly the top riders. That would certainly go a long way to transparency. The question is whether or not once again you get armchair scientists analysing all of that data and speculating on it. That is always the risk, that you create more of a problem than you actually solve.

There are obviously also performance aspects in competitors having access to all of your statistics and values

So where the optimal lies in terms of how much data should be released, I don’t know. Hopefully we get more transparency, but where the optimal lies in that process is something we still need to look into further.

CT: But this could be a catalyst for others to step up and to do likewise?

JS: Yes, I think he set a good example. Hopefully other riders now follow suit.

Note: This interview has been edited for clarity and length.

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