Tuesday, April 8, 2014

Contador: 2241 VAM @ Vuelta al Pais Vasco stage 1


Yesterday at stage 1 of the Vuelta al Pais Vasco, Alberto Contador won, finishing 14 seconds over Alejandro Valverdi and 34 seconds over Michal Kwiatkowski.

The route included 8 rated climbs, including two ascents of the steep Alto de Gaintza, which gains 290 meters in only 2.3 km (see stage preview). Four riders have uploaded the stage to Strava, Here's Kenny Ellisonde's activity. He was 40th, @ 2:42 down on Alberto.

Here's the report on Alberto's time up the last ascent of Alto de Gaintza, the final climb of the race:

If these numbers are good, that works out to a VAM of 2241 meters/hour. Assuming a CdA of 0.32 meters squared (recommended by Vetooo based on extensive comparison of VAM and rider-reported SRM data, and coincidentally measured by Tour magazine in a wind tunnel), an air density of 1.15 kg/m3, a drivetrain loss of 3%, a rolling resistance coefficient of 0.4%, a rider mass of 62 kg (Wikipedia), equipment mass of 1.5 kg, a bike mass of 6.9 kg, I get a total power of 464 watts for these 6 min 56 seconds. That's 7.49 watts/kg.

But the effort was short, and this was the first stage of the race, so Contador was fresh and ready to go at the starting line. This is a big difference from the same numbers up a Alpine or Dolimite climb late in a 3-week stage race.

I can convert to an equivalent critical power number assuming AWC/CP = 90 seconds. Then from power = CP + AWC / t = CP[1 + (AWC/CP) / t], I can estimate an upper bound on CP = power / (1 + 90 seconds / 416 seconds). That's an upper bound CP estimate of 6.16 W/kg.

Curiously, it's only 1% more than the CP estimate I got from Chris Horner climbing Sierra Road in the 2011 Tour of California, 6.12 W/kg.

And it is a very good number. Contador's altitude training clearly paid off.

1 comment:

djconnel said...

Updated from initial posting, which used 70 kg rider mass, to use 62 kg mass (from Wikipedia). W/kg increases less than 1%.