Velon belatedly release Chris Froome's power numbers from Giro d'Italia attack

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Power data from Chris Froome's stage-winning and race-upending ride on stage 19 of the Giro d'Italia has been made public, with the Team Sky rider averaging 397 watts for a three-kilometre stretch on the Colle delle Finestre, where his remarkable 80km solo victory began.

Froome went on to win the Giro, his third straight Grand Tour victory, but the data was only made public on Monday, the day after he'd been crowned in Rome and 72 hours after the stage itself.

In the interim, Froome's performance had ignited debate, with some at a loss to understand how the Briton, who had been listless for much of the Giro, had turned the race on its head in such spectacular fashion.

Eyebrows were raised when Velon, the business group that represents 10 WorldTour teams, released their daily 'rider data summary' from the stage. While power output figures were given for six other riders, including Tom Dumoulin, there was no data for the stage winner. The only numbers that were listed were his times, average speed, and top speed for selected sections of the course - the last 6.7km of the Finestre, the whole descent, and the subsequent Sestrière.

On Monday evening, however, they issued a press release showing 397 as 'the number behind Chris Froome's stunning attack on the Colle delle Finestre'. It was accompanied by a photo of a pink jersey signed by Froome, with 397W written on the chest along with '19' - the number of the stage.

Froome, the data says, put out an average of 397 watts over 3.02km and 11 minutes 3 seconds as he rode away from Dumoulin et al, turning the pedals at an average cadence of 95rpm on the 9.3 per cent gradients. His heart rate - the other metric used by Velon - was not made public.

Contacted by Cyclingnews, Velon explained that they didn't publish Froome's data at the time because they didn't have it available. The Briton's live tracking system, as with that of numerous other riders, cut out at certain points on the stage and the data was incomplete in the immediate aftermath. With the help of Team Sky, they said, they then went back to 'piece the puzzle together'.

"We still have lots of work to do, and we know we missed some parts of the race that we, the fans and the riders wanted to see more of. We're working to improve but in the meantime we hope people enjoyed the story of the race from a perspective that no other sport in the world currently offers," Velon CEO Graham Bartlett said in a statement. 

Velon confirmed that Froome carried a tracker under his saddle throughout the race and shared his data to the system on every stage.

In their initial post-stage 19 data summary, Velon gave Dumoulin's numbers for an unspecified stretch on the Colle delle Finestre, when he was riding in pursuit of Froome. The Dutchman put out an average of 395w over a period of 10 minutes 15 seconds on a nine per cent gradient, with a cadence of 89rpm.

Dumoulin put out similar average power over that period compared to Froome over a period of similar length, though Froome is understood to be lighter. Accurate, up-to-date weights for each rider would be needed to calculate each's watts-per-kilogram, though these are neither provided by the teams nor Velon.

Velon also published Dumoulin's power numbers from the first kilometre of the final climb of the Jafferau, where he once again averaged 395w, though it was not possible to compare Froome and Dumoulin on the same part of the course.

Velon explained that, rather than putting up full data files, they pick out sections based on what they think will be most interesting to fans.