4th December 2015

Analysis: Froome’s physiology may explain TDF performance

Test results released by the GlaxoSmithKline (GSK) Human Performance Laboratory on Chris Froome will offer Team Sky some reassurance in explaining Froome’s performance in the Tour de France, which came under question after figures for Froome’s ascent of Mount Ventoux in 2013 were leaked and married to YouTube footage of the climb. The results of the GSK lab’s testing, featured in an article published today by Esquire magazine and reproduced below, appear to show that Froome’s physiology and changes to it have enabled him to produce extraordinary performances.

VO2 Max scores

The first finding was that Froome performs extraordinary well in VO2 Max tests, which measure the maximum amount of oxygen that an athlete can use. He recorded a score of 84.6 in the GSK tests, which at his Tour de France race weight would correlate to 88.2, since the test includes body mass. Phillip Bell, a sports scientist at the GSK laboratory, described the performance as “off the charts. We’ve never had close to that in the lab,” he told Esquire.

It is understood that an active team sports player would record a VO2 Max between 35 and 40, while Tour de France cyclists tend to record a score in the high 70s. It is understood that a VO2 score is partly due to genetics, and that the ‘team player’ referred to above would not be able to increase their score to 80, even with training. The highest VO2 Max score recorded by a cyclist is understood to be 92.5, by Greg LeMond.

In 2007, during previous tests conducted on Froome by the Lausanne anti-doping laboratory (CHUV), also reported by Esquire, Froome recorded a VO2 Max score of 80.2. However, he was over 8kg heavier at 75.6kg, with body fat of 16.9% and as previously explained, body mass plays a part in the VO2 Max score. It is understood that by losing the 8kg and reducing total body fat to 9.8%, Froome could have achieved a 10% increase in his power-to-weight ratio, which could explain his extraordinary performances in the Tour de France.

Heart rate

The GSK data does not appear to include a measurement of Froome’s resting heart rate, however in 2007 it was 32bpm, as recorded by CHUV. The average heart rate is between 60bpm and 72bpm. Miguel Indurain, who won five consecutive Tours de France from 1991 to 1995, recorded an incredibly low resting heart rate of 28pbm – one heartbeat every two seconds. GSK recorded Froome’s heart rate rising to 140bpm, which is low compared to the 174bpm allegedly recorded during the La Pierre St. Martin climb during this year’s Tour de France.

As Froome’s resting heart rate is likely to have lowered in the eight years since the CHUV analysis, it is now likely to be comparable to Indurain’s. The ability for Froome’s heart to rise from this low rate to 174bpm illustrates that he has an ‘engine’ comparable with cycling’s greats.

Blood data

Esquire also published two sets of Froome’s blood data from this year. On 13 July, Froome’s haemoglobin was 15.3 grams per litre (g/l) and 0.72% of his oxygen-carrying red blood cells were immature (the normal adult range is 0.5%–2.5%). On 20 August, Froome’s haemoglobin was 15.3 g/l and he had 0.96% per cent immature red blood cells.

An Offscore is designed to measure the balance between the amount of red blood cells in an athlete’s system and their rate of formation. If the offscore is too high, it could indicate that something has caused the body to produce extra cells. Training at altitude can do this, as can blood doping. Erythropoietin (EPO) stimulates the bone marrow, flooding the blood with immature cells, whereas a blood transfusion results in excess red blood cells, which suppresses the bone marrow and results in fewer immature red cells.

On 13 July, Froome’s offscore was 102.1 and on 20 August it was 94.21. It is understood that such scores are not generally regarded as suspicious, and that the first test was higher because it was recorded after the GSK test, and exercise can stimulate cellular production.


“I’ve seen a value of 5.8w/kg being spoken of as the upper limit of human performance for a 40-minute effort”, exercise physiologist Jeroen Swart told Esquire. “But 6.2w/kg is definitely doable for Chris for 20 minutes if not longer. Chris’s peak power is 525 watts, which corresponds to 7.51w/kg: a massive figure. But the interesting thing is that the [sustained] figure of 6w/kg – which is basically what he produced in the lab – is 79.8 per cent of his peak power. That’s a completely reasonable percentage.”

However, despite this, it appears unlikely that such figures will exonerate Froome completely. Esquire sowed the seeds of doubt in its article through comments from Antoine Vayer, a former cycling coach who has worked with teams such as Festina and who accused Froome’s GSK tests of being “stage managed”.

“I don’t think it is going to change perceptions or what people think but at the same time that’s what people have called for and he’s done it”, Froome’s former team mate, Bradley Wiggins, told BBC Radio 5 Live. “Hats off to him for doing it and I’m sure it’s not going to be something that they [he and Team Sky] are going to live and die by. I don’t think it’s going to change anything but it’s a small step maybe.”

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