At the Tour de France's second race day in Gap Team Sky released power data from race leader Chris Froome's stage 10 ride to enable a greater understanding of his performance.

The Brit took victory on the climb to La Pierre-Saint-Martin, the first summit finish of the 2015 event.

Speaking to gathered press, Team Sky Team Principal Sir Dave Brailsford said: "We thought we'd give people concrete numbers and facts. We’re not going to get caught up in endless debate. We’ll give you info, carry on racing and then address it after the Tour if necessary. 

Head of Athlete Performance Tim Kerrison added: "We have a lot of data on our riders and the way we apply and use it, we see that gives us a competitive advantage. As in most industries, knowledge and intelligence is giving a competitive advantage.

"It’s difficult to indicate the exact start of the climb, so I’ve analysed the last 15.3km, which is an effort of about 41 and a half minutes."

Below is the data that was sent out to media attending the press conference:

Analysis of final 15.3km of the stage

(It is difficult to identify the exact start point of the climb as there is no clear landmark defining the start.)

Time: 41:28

Average power: 414w

VAM: 1602

Chris's weight: 67.5kg

Corrected power/weight for the whole climb: 5.78w/kg

When used in conjunction with osymetric chainrings, power meters over-report power by approximately 6%. The above figure of 5.78 w/kg is corrected to take this into account. Without making this correction, the power/weight would be 6.13w/kg. All other power values stated here are the actual reported power values - i.e. not corrected.

(To go from this value to estimates of physiology (e.g. VO2max) requires assumptions about relative aerobic and anaerobic contribution, sustainable percentage of VO2max for the duration of the climb, and efficiency and economy of the rider. There is significant margin for compounding error in making these such assumptions.)

Gearing:​ 52-38 / 11-28

Average Cadence:​ 97rpm

Average HR: 158

Maximum HR: 174

This is a very high heart rate for Chris suggesting that he has reached the second week of the Tour/bottom of the climb in a relatively fresh state. By comparison, Chris's maximum HR in the second week of the Tour in 2013 was 168. In the Vuelta 2014, it was 171.

"The Attack"

Duration:​ 24s

Average Power: 556w

Peak power: 929w

10s power: 652w​ (

Average Cadence: 102rpm

Average Speed:​ 25.3kph

Maximum Speed:​ 27.7kph

Power for the 4 minutes before the attack: 449w (18.2kph, 1777VAM, 9.8% gradient, 94 rpm)

Power for the 4 minutes after the attack: 435w (20.4kph, 1718VAM, 8.4% gradient, 103 rpm)

After the initial attack, when Chris continued to ride away from the field, his power and climbing speed (VAM) were lower than before the attack. 

Comparisons with Chris's performance in the past:

30min power: 419w

Chris has exceeded this level (by as much as 10%) on 16 occasions over the past 4 years in racing and training

60min power (run-in plus climb): 366w

Chris has exceeded this level on 15 occasions over the past 4 years in racing and training

Comparison with Stage 12 - Plateau de Beille - where there was a front group of 9 riders:

30min power: 414w​ (5 watts less)

60min power: 373w ​(7 watts more)