Team Sky had billed their rest-day press conference as featuring their three main men for the Tour de France: Chris Froome, Geraint Thomas and Sir Dave Brailsford. But the addition of the head of athlete performance, Tim Kerrison, computer at the ready, made it clear that, as Brailsford had trailed the evening before, the team were about to reverse their long-standing policy of non-disclosure and release data on Chris Froome’s physiology in an attempt to stymie speculation about his performances.
Brailsford’s move was prompted by two videos, primarily the one shown on French television on Sunday night showing a physiologist calculating Froome’s power output at just more than seven watts per kg of body weight, which the Team Sky head described as “wildly wrong”. Power-to-weight ratio is the key statistic to indicate how well an individual can climb, boiling down to how much power a cyclist can put out in order to shift body and bike uphill. The key then is how long an individual can sustain that power.
Another key element was a video released by the anti-doping campaigner Antoine Vayer the previous week, showing what purported to be Froome’s power, cadence and pulse rate for the Mont Ventoux climb in 2013. Vayer claimed the data had been leaked to him and, intriguingly, at the press conference Froome seemed to hint the figures on the video might be genuine when he said: “Everyone knows one of my most significant files is out there, the one from Mont Ventoux.” That video set the tone for a week in which Froome’s power figures – or lack of them – overshadowed much of the actual racing.
For the climb of La Pierre-Saint-Martin last week – estimated by Kerrison at 15.3km and taking about 41 and a half minutes – the Tour leader climbed with an average power of 414 watts. Kerrison pointed out that the oval chainrings that Sky use can over-measure power by up to 6%, and the figure had not been adjusted for that.
With Froome’s race weight at about 67.5kg, and shifting the power figure downwards by that 6%, the physiologist calculated his power to weight ratio at 5.78 watts per kilogram, considerably below the value estimated by the French television station.
Froome’s climbing speed, or VAM (Velocità Ascensional Media), was 1602. Making comparisons using VAM is not an exact science because there are so many variables such as wind direction, gradient – there was a tailwind at Pierre-Saint-Martin and the gradient was apparently conducive to a high VAM; but, even given that, the figure compares favourably with the figure of about 1800 or more attained by top riders during the era when EPO was widely used.
Of all the statistics the one that probably helps to explain why Froome went so well on the climb compared with other potential winners was his maximum heart rate of 174 beats per minute. Heart rate varies from person to person so it is a figure that is of interest compared only with an individual’s other readings.
But, critically, Kerrison said: “It was equal to the highest maximum we’ve seen from Chris Froome in a Grand Tour, which suggests that he arrived at the climb very fresh.”
In other words Froome got through the first nine days of the Tour as comfortably as he could possibly have hoped and he negotiated the transfer day well enough to arrive at the foot of Pierre-Saint-Martin with his physical resources intact.
Kerrison also gave out figures which gave some idea of how Froome’s performance on the climb compared – for him personally – within a wider context. The figure chosen was the power Froome sustained for 30 minutes (the bulk of the climb): 419 watts, again an unadjusted figure. “Chris has exceeded that level by as much as 10 % on 16 occasions over the past years in racing and training,” said Kerrison.
Froome’s 60-minute power figure, which includes the flat kilometres before the climb, was 366 watts. According to Kerrison, he had “exceeded that level on 15 occasions over the past four years. In terms of what he delivered on that day, in the context of what Chris has done, it was a fantastic climb but, by comparison to what he’s done in the past, not at all unexpected.”
Chris Froome’s performance data from Stage 10 [Tarbes to La Pierre-Saint- Martin]
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: 41min 28sec
Average power: 414 watts
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.
Gearing: 52-38/11-28
Average Cadence: 97rpm
Average heart rate: 158
Maximum heart rate: 174
This is a very high heart rate for Chris suggesting he has reached the second week of the Tour/bottom of the climb in a relatively fresh state. By comparison Chris’s maximum heart rate in the second week of the Tour in 2013 was 168. In the Vuelta 2014, it was 171.
“The Attack”
Duration: 24sec
Average Power: 556 watts
Peak power: 929w
10s power: 652w (<60% max)
Average Cadence: 102rpm
Average Speed: 25.3kph
Maximum Speed: 27.7kph
Power for the 4 min 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)