The moment when Chris Froome produced a sudden, violent acceleration, spinning the pedals at an intense rate as he attempted, successfully, to ride Alberto Contador off his wheel on the ascent of Mont Ventoux may come to encapsulate the 100th Tour de France if he goes on to win on Sunday in Paris.
Inevitably the move raised eyebrows, given that seated accelerations at the high cadence Froome briefly produced are rarely seen on mountain climbs. But the Australian physiologist Tim Kerrison, who has revolutionised the way his charges at Team Sky build up to races such as the Tour, explained that such intense efforts when the body is already close to its limit are a key part of his proteges' training. In that sense, this was a relatively routine piece of riding for Froome.
"Pete Kennaugh was laughing at the end of the stage," said Kerrison. "He said the way Chris rode that climb was exactly what we do in training every second day. Our training is much more than just doing intervals at a constant pace for a set amount of time; [some of it] is about being able to handle changes of pace – to go from, say, 350 watts to 650 watts for a few seconds to attack and get a gap on a rider who is trying to follow, then come back down to 350 watts."
Kerrison's term for this kind of interval training is spiked efforts, "where we make an effort then come back to a very high but sustainable pace. The energy systems have to have the ability to produce that power, which will produce a load of lactate in the muscle, because you are well above anaerobic threshold [the point at which the body is producing more than it can handle of the lactate which is the main limiting factor in intense efforts] – then come down to a very high level, just sub-threshold, and clean out the lactate, the effects of the attack. Pretty much all our training is based on that. The guys in the team who train that way look at [Froome's attack] and think, 'He's rehearsed that way of riding, three or four times a week for the last two years'."
Most often when climbers make their attacks on a mountain, they do it standing on the pedals to gain the maximum amount of leverage from the arms and upper body. Froome remained seated while making his attack on Contador, however. There is a clear advantage in doing this, Kerrison believes: working in a wind tunnel has shown Sky that there is much less drag when a cyclist remains sitting down. That applies even at relatively low climbing speeds.
"There is a significant increase [in drag] when you attack out of the saddle compared to staying seated and keeping your body narrow. If you can [attack] as well in the saddle [as standing] you will get more speed for the same power because there is less drag. It's while you are accelerating that drag is more important, so if you accelerate in a streamlined position, you get up to your speed more efficiently."
Froome's high cadence was surprising, but not rehearsed in training, the race leader said. One explanation is he had no option but to spin the pedals faster because changing on to the larger chainring at the moment of attack brings the risk of derailing the chain and aborting the attack, as Andy Schleck found in 2011. Kerrison adds that about once a week Sky's riders practise riding in the highest cadences they can manage, basically for fun.
For those who wonder why Froome reined himself back after he caught Nairo Quintana higher up the mountain, Kerrison explains: "As a general rule attacks to drop someone like Contador aren't sustainable because the rider has to attack at such intensity to drop the guy. Chris got to Quintana, the gap was creeping up very gradually, at about a second a kilometer, then Froomie had to decide how long he and Quintana would work together for.
"Froomie was doing the bulk of the work, then there came a point where he decided to put more time into the guys behind so he stepped up a level again. He went away again at a pace he felt he could sustain for the last couple of kilometres."
That explains the difference between the sudden, abrupt effort Froome made to drop Contador, and the gradual turning up of the throttle which burned off Quintana. In the second effort, getting rid of the Colombian was incidental, as what mattered was to accelerate and gain time on the riders further behind, who were the real threats for the overall standings.
Looking further ahead, Kerrison believes that Froome could well be the strongest climber in the race at the end of the week in the Alps – although he tips Quintana to make a run for the podium –but that Sky's priority will be defending his race lead rather than going for a full house of stage victories.
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