• Mark Turnbull

INSCYD view: A scientific analysis of Chris Froome’s Giro d’Italia performance

Shane Stokes (Cyclingtips) and Sebastian Weber (INSCYD)

The 2018 Giro d’Italia is fading in the rearview mirror, but debate continues to rage. Was Chris Froome’s stage 19 comeback plausible, or did it stretch credibility? Can we believe what we saw? Are comparisons to Floyd Landis’ ride in the 2006 Tour de France unfair, or are they reasonable?

Much of the debate has been emotive, based on gut reaction and feel. Power data released by Velon is incomplete, representing only the period around Froome’s initial acceleration and the moments that followed. Yet one sports scientist has sought to use those numbers to scrutinize the ride.

These figures were juxtaposed with the data from the lab test Froome did in August 2015, and which was subsequently released in a medical paper. Data from Froome’s Stage 14 win atop Monte Zoncolan was also used, as was data from his stage 20 defence of the maglia rosa.

A number of assumptions had to be made with the analysis, not least because of the limited data Velon published. However, as a physiological exercise, the approach by Sebastian Weber to analyse using the INSCYD metabolic analysis software is an interesting one and will add to the debate surrounding Froome’s unexpected victory at the Italian Grand Tour.


First off, the Velon data. In a press release issued the day after the end of the Giro, the company revealed the details of Froome’s Stage 19 attack. It said that his move came 10 kilometres into the Finestre climb, and averaged 397 watts of power on a 9.3% gradient for 3.02 kilometres. The time for the segment was 11 minutes 3 seconds and the average cadence was 95 rpm.

Velon didn’t release heart rate data, nor any other details.

As regards the Stage 14 data, Velon said that Froome’s attack to win on the Zoncolan “was built on a 1.3km attack in which he averaged 465 watts and 12.4km/h on a 15.4% gradient.”

It released more data from Stage 20, where Froome came under repeated attacks from Tom Dumoulin. Weber identified the three most important blocks of data. These were following Dumoulin’s attacks on the Cervinia climb, which was three minutes at 450W and 24.1km/h, a segment Velon called “thwarting attacks on the final climb,” which was 9:08 long with an average power of 420 watts and a maximum power of 760 watts.

See Froome’s Velon data from the Giro d’Italia here.


Sebastian Weber is a German sports scientist who previously worked with HTC-Highroad, Katusha, Lotto and Cannondale, and is an advisor to several sporting organizations such as the French swimming federation and Cycling Ireland.

The INSCYD system is currently used by Bora-hansgrohe and LottoNL-Jumbo, as well as coaches from other sports, and is a physiological analysis tool which draws on more than 150 scientific studies to break down athletic performance. Its functions include calculating an athlete’s particular “engine,” including what their physiology and fitness level should enable them to do, as well as the mix of fuel sources they use to do work.

Lab tests can be used to create a model for each rider. So too field tests: By gathering and combining data such as power measurement, heart rate and lactate levels, it is possible to create the same model for a rider. This can be used to design training programs, and can also be tracked over time to trace improvements and to highlight areas which need work.

Importantly, the model created for a rider can also predict what they should be capable of doing. Thus, the exercise to compare the virtual Froome from 2015 with what he did in the 2018 Giro.


Three weeks after Froome’s second Tour de France victory, the Briton voluntarily underwent a lab test on August 17 at the GlaxoSmithKline Human Performance Lab in Brentford, London. He was examined by GSK senior sports scientists Phillip Bell and Matt Furber, as well as the lab’s director of research and development, Ken van Someren.

The testing was observed by Jeroen Swart, a sports physician and exercise physiologist at the University of Cape Town who is also part of South Africa’s doping control review commission.

The information gathered was used to write a scientific paper entitled The Physiological Profile of a Multiple Tour de France Winning Cyclist, which appeared in the peer-reviewed journal Medicine & Science in Sports & Exercise in early 2017.

Weber drew on this data to build a physiological profile of Froome. He explained to CyclingTips how he did this: “We went back over his lab test. We have a measurement of his VO2max, we have some lactate levels in there. We have some bodyweight and body composition/body fat measurements. We also had gross efficiency measurements, changes under different environmental conditions, and lactate concentrations at a given power output and time duration during the lab test. We used all those metrics to build a physiological model.”

Weber did have some issues with the lab test, believing that adjustments needed to be made. “There is a VO2max reading which is stated to be 84 ml/min/kg. But when you put this in perspective with the other metrics – gross efficiency, body composition, power output at the end of the ramp test, lactate values, etc, the data doesn’t line up perfectly. His functional VO2max is more likely a shade lower, something like 1.5-2.5 ml/min/kg less.

“But this said, the difference is in the normal range of error of measurement. And even in the paper the author states the coefficient of variation in the metabolic cart was 1.8%, but only tested up to 3.94 l/min. Well, Froome’s test was 5.91 l/min, so well above this range. Furthermore, at maximum effort, you might see higher VO2 measurements because of active muscle mass in the upper body. Long story short, in our calculations, we used 82.2 ml/min/kg as a ‘functional VO2max’ because it fit better with all the other metrics.”

Chris Froome en route to stage victory atop the Zoncolan on stage 14 of this year’s Giro d’Italia.

Before explaining what he did next with these corrected lab test results, Weber gave his analysis of that 2015 test, plus a theory on why he believes Froome has been so successful in three-week races. “It is an outstanding high performance, but there is nothing so different from his rivals,” he said. “No offence, but there is nothing super special compared to them; it is like if you look at Chris’ performances in a one-day race.

“He has a physical capacity similar to other GC contenders. If that was not the case, then he would not sit in the same group as them most of the time, and he would ride away every stage. But he is on par with his competition. He is maybe a tiny bit better. Maybe he is just more stable.”

This consistency is, he believes, what adds up over a Grand Tour. “His success is more about being able to not have volatility, to not have fluctuations in his performance, I think. It is more about being able to have these numbers for a constant three weeks. Look at Simon Yates. Maybe he had better numbers starting the Giro, but obviously, he has had a big fluctuation.”


Weber and the coaches of Bora-hansgrohe and LottoNL-Jumbo, as well as coaches from other Olympic sports, have been using the INSYCD software to project what is possible from their athletes. Importing raw material enables a characteristic profile to be built of each sportsperson; among the information it calculates is the fuel sources athletes use. Given that the body’s stores of glycogen are limited, but body fat is not, the fuel analysis combined with power data can help tell how hard an athlete can go and for how long.