Maybe Vincenzo Nibali made a mistake in trying to drop Chris Horner for good on the treacherous ramps of the Angliru: in the last 25 minutes of climbing, the italian launched 6 very violent accelerations, to which Horner did not respond, continuing with a steady pace and always gently closing on the Astana rider.
The accelerations did cost treasures of glycogen (drained by the 19 carburetors triggered by anaerobic combustion) and indeed it was a wise choice for Chris to keep cool and rely on his aerobic power, which was likely higher than that of Nibali for the whole of this uncertain Vuelta.
In my opinion Nibali should have waited the last few meters of the stage, placing a single violent and decisive acceleration, since the two contenders were separated by just three seconds anyway.
The ascent of the Angliru was preceded by the Alto de Cordal (5km at 10%), which was done at 1800m/h (6.00 w/kg), and such pace surely was felt in the legs of almost all the protagonists.
Horner won the Angliru in 42'00", VAM = 1778 m/h, 5.92 w/kg with Nibali and Valverde not far off: 42'18", thus completing the podium of this Vuelta 2013.
Once again the extreme slopes (over 15%) penalize VAM: when the speed is so low the accelerations/decelerations are greatly accentuated with each pedal stroke, involving an extra expenditure of energy.
And once again such extreme climbs have resulted in smaller gaps between the riders at the finish, compared to climbs of similar length, but with gradient more suited to road cycling.
The repeated climbing performances of Horner raised the usual concert of suspicions: "Experts and Pundits" dared venturing into treacherous terrain, not very well known to them.
It is especially the performance of Pena Cabarga (545m of elevation at 9%) that triggered the Reviewers: VAM = 1958 m/h - 6.75 w/kg - 425w (assuming Horner's weight to be 63kg).
I remind you that this performance was achieved in 16'42" of effort, partly behind the wheels of other riders, at sea level and Horner himself had already expressed similar performances in the past (see "Horner Vs Contador", my comment of 2011).
The same Nibali, whose form did not seem to match the one shown in the recent Giro d' Italia, managed to perform at similar levels, if somewhat lower: 1912 m/h - 6.59 w/kg - 415w (with 63kg of body weight).
Chris Horner is an "atypical" cyclist, with the physical conformation of a child with narrow pelvis, his ultra-light weight allows him to ride for long stretches out of the saddle, pushing long gear ratios and adopting far too low cadences (50 RPM in some sections on the Angliru), a feature that obviously suits his style but that probably he has specifically trained (Esasperazione delle Andature, I use to call it).
Horner deservedly won the Vuelta which saw a lot of uphill finishes, almost all at low altitude, facing riders who had previously engaged 100% in the TdF (Valverde, Rodriguez) or the Giro (Nibali), and who appeared not at their highest level of form, confirming that in this cycling, hysterically "needle-free", it is almost impossible to have two peaks of top condition in the same season.