Analysis: what does Chris Froome’s lab test data mean?

Dig Deep coach Stephen Gallagher on the story behind Chris Froome's physiological data

The much-anticipated data from Chris Froome’s physiological tests has been released – a move which Froome hopes will silence his critics, who have raised questions over the legitimacy of his performances, and one which will undoubtedly come under scrutiny from all corners of the sport.

Froome’s data has been released in an initial article on the Esquire website, with a full piece to follow in January’s edition of the magazine, as well as a report from the GSK Human Performance Lab, where the tests were conducted on Monday August 17.

Froome completed three tests. Two submaximal tests provide an insight into how well Froome is able to sustain power, with one taking place in cool conditions and one in hot conditions, with a VO2 Max test in between to determine the maximum rate at which Froome is able to take in oxygen. Froome also revealed some of his blood data.

The data from Froome’s test in August 2015 sits alongside data from tests performed in 2007 at the UCI’s World Cycling Centre in Switzerland. This, Froome hopes, will provide justification for his rise from a 22-year-old first year pro to a two-time Tour de France winner.

Here Stephen Gallagher, a former professional cyclist and director of Dig Deep Coaching, takes a closer look at the physiology data and what it means.


First of all, for one on the best riders of our generation to release this data offers a fascinating insight into what it takes to perform at this level – to win the Tour de France – and hopefully we will see other riders follow suit.

We also need to put the information delivered in the Esquire article into context before we look at the raw data. The test on August 17 was conducted three weeks after Froome won his second Tour de France title. During the interim period, Froome would have competed in a series of post-Tour criterium races across Europe and, while these races are not physically demanding, the constant travel and external stresses associated with being the Tour de France champion will mean Froome wasn’t at his freshest come test day.

Froome can expect to have seen a small loss of fitness compared to his Tour de France form, while he also put on close to three kilogrammes compared to his Tour de France weight (67kg at the Tour de France to 69.9kg on test day). This additional weight has a significant impact on Froome’s power-to-weight ratio (w/kg) and, again, underlines that the test does not show Froome’s in absolute peak condition.

Chris Froome hopes releasing the data will “satisfy some of the questions asked” (Pic: M.L’Azou/ASO)


Froome’s VO2 test was performed on a protocol of 30-second ramps in wattage until exhaustion and show that his high VO2 continues to be one of his major strengths over rival riders, allowing Froome to launch short, killer attacks in the final kilometres of a climb and put time into his rivals.

As far as VO2 Max is concerned, in simple terms the more oxygen a rider is able to take in to fuel the muscles, the more power they are capable of producing. It’s seen as a good measure of aerobic fitness – though efficiency and sustainable power, which I’ll come on to, are just as important.

– Six things you need to know about… VO2 Max –

Froome’s data shows from August shows a VO2 Max reading of 84.6ml/min/kg (VO2 is measured as millilitres of oxygen consumed per minute and corrected for body weight to allow a comparison between riders). As a comparison, while a WorldTour professional cyclist will be expected to have a VO2 Max of around 75-90ml/min/kg, an average Joe will probably be less than 50.

Froome’s peak power is also gives as 525 watts (7.51w/kg) and although the definition of ‘peak power’ is not given by the article, it typically relates to the maximum power that can be sustained for approximately five minutes. At Tour de France race weight Froome’s VO2 Max would translate to 88ml/min/kg.

The Esquire article compares data from a physiology test in August 2015 to data from 2007 (Pic: Sirotti)

A VO2 Max of nearly 85ml/min/kg is undoubtedly doubt world class and at the upper limit of professional cycling but figures of 7.8+ w/kg have been seen at WorldTour level and, had Froome been at Tour weight and produced the same peak power, it would have seen him fall perfectly into that bracket at 7.83kg.

To put this into context, our coaching data shows many elite-level riders in the UK are in the 7.1-7.2 w/kg range, with the average Sunday racer punching in at 5-5.7w/kg for power durations of four to six minutes.

Froome’s results underline his natural physiological makeup at peak aerobic power. Your VO2 Max is one of the hardest physiological numbers to adapt and train to any great degree, with any real progress in this area largely down to genetics and, crucially in the case of Froome, weight reduction. Ultimately, Froome’s naturally high VO2 puts him in a strong position as a professional cyclist.

Froome’s previous data from 2007 shows a VO2 Max reading of 80ml/min/kg and a peak power of 540w. While his VO2 Max was a little lower, his peak power was, in fact, 15 watts higher during the 2007 test. However, the data from Froome’s 2007 and 2015 tests is very similar with one key difference – in 2007 Froome weighed nearly six kilogrammes more than when he conducted this summer’s test, and more than eight kilogrammes more than his 2015 Tour race weight. These results show that Froome’s impressive physiological make-up was there to see in 2007 and waiting to be put into action through weight loss and an improvement in sustainable power.


VO2 Max in itself is only one half of the story – the key is being able to efficiently put that oxygen to use in order to put power through the pedals.

Looking at sustainable power for twenty to forty minutes, approximately the length of a Tour de France climb, Froome’s 2015 test shows an impressive 419 watts and 5.98w/kg, while at race weight this would be 6.2w/kg – as the Esquire article notes, this is at the upper limit of human performance.

One of the key attributes of a top elite rider is to have a sustainable power which sits as close as possible to VO2 Max – essentially it underlines a rider’s efficiency. The test shows Froome’s sustainable power as 79.8%, allowing him to maintain a very high power without going into the red.

During the long mountain climbs or critical time trials of the Tour, it is that efficiency – fully utilising an incredibly high VO2 – which is really put to the test and from this data you can see why Froome is able to perform better than most in those circumstances, putting out huge amount of powers for long periods of time. The key for Froome is having a high VO2 Max and a high sustainable power.

If we look at Froome’s heart rate data taken during his 2015 submaximal test, it is possible to see another reason for his ability to maintain such a high power over a sustained effort without riding to exhaustion.

Froome’s cardiac drift as his wattage rose was minimal compared to many cyclists who would undergo such a test, with his heart rate rising only 20 beats per minute from riding at 300 watts to 420 watts.

This shallow rise in heart rate is another trait of elite endurance athletes who want to compete at the highest level and the lack of upward cardiac drift in Froome’s heart rate during this 32-minute test will be a major factor in his ability to ride at a high power for prolonged periods of time without putting excessive stress on the aerobic system.

Froome won his second Tour de France title in July 2015 (Pic: Sirotti)

Tuning the engine

Back to weight loss, and a comparison between Froome’s 2007 and 2015 tests clearly show that his power was very close, despite the progression in his career over that time. Like many riders of his generation, for example Bradley Wiggins, much of Froome’s progress can be attributed to weight loss, while maintaining much of his peak power and efficiency. Between 2007 and 2015, Froome maintained his power but lost a large amount of fat to come down to a very lean 67kg at peak race fitness.

Being able to balance this weight loss and power is a massive undertaking but one that is possible with the support a large team of sport scientists, coaches and nutritionists working on Froome’s behalf.

For elite-level cyclists in the UK, I see plenty of riders sitting at around 5.4 to 5.7w/kg for sustainable power, working at an efficiency of 70-75 per cent compared to VO2 Max. The variation between Sunday racers is quite wide but for many a figure of between 3.8 and 4.2w/kg would be expected for sustainable power.

The data shows Froome combines an incredibly high VO2 Max with an equally impressive sustainable power (Pic: X.Bourgois/ASO)

One of the main considerations that must be put into context here is Froome’s ability to produce these  numbers day after day over three weeks of racing. This is not just necessarily the case with Froome, but with all professional riders. Having the ability to recover and maintain form and fitness, as well as having a highly-efficient engine, is one of the major differences between WorldTour riders and local elite riders.

While Froome’s data is far from complete and is sure to provoke more questions from some quarters (Froome says he hopes it will “satisfy some of the questions asked [but knows it will] not convince everyone”), to see one of the sport’s leading riders provide an insight into his ability is both exciting and encouraging for fans of the sport, coaches and anyone interested in sports science, not to mention aspiring riders wishing to hit such levels.

Website: Dig Deep Coaching


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