Well, the response to the post yesterday describing Contador’s climb has been overwhelming – being in SA, I slept through most of your emails and woke this morning to a deluge of comments and analysis of the climb. Thank you to everyone for your input. It would be wonderful to do a more detailed breakdown of the climb, but that would require accurate information regarding the profile and the specific gradients per kilometer.
Unfortunately, there is little chance of consensus on the actual figures for the climb. Many of you have commented in the last post and referred me to profiles, breakdowns, specific kilometer-by-kilometer gradients, and thank you very much for that. However, not a single person’s input agrees with anyone else’s!
For example, on the Tour website, the climb is listed as 8.7km at 7.5%. However, the profiles many of you provided vary quite a bit from this. The Tour profile indicates a 9km climb with a total rise of 638m (a gradient of 7.1%). Other websites were saying it was 8.8km at 7.5%, or 7.1%, or 8.3 km long. There was even a suggestion that it was only 7.2km long! Finding the real profile seems a mission impossible! This has obvious implications for the calculated wattage and VAM on the day.
I believe that the distance of the climb is 8.7km - I base this on the fact that at the bottom of climb, as the peloton turned left, the banner signalling the start of the King of the Mountains “competition” very clearly indicated 8.7km to the summit. I can believe that the Tour website might be incorrect, but I find it difficult to believe that they would also err on the actual measurement of the route. Also, one of you said that an SRM from a Tour rider showed the length of the climb to be 8.74km. So I think it’s a safe bet to say that the climb is 8.7km long.
In terms of the vertical rise, it is more difficult. It seems that most are saying that it rises 638m. A few commenters said this, and it was also the assumption used Dr Michele Ferrari in his own analysis of the climb at 53×12.com. Finally, SRM data from yesterday suggests that the climb is 640m, which differs from the 653m that is inferred from the official Tour guide and even from the mapmyride.com route, which has a 653m rise over an 8.7km length.
As a result of all this “disagreement”, doing a detailed analysis on this kind of data is fraught with assumptions and therefore possible errors. As it is, Contador’s climbing rate is either 1858m/hour or it is 1900m/hour. A small error – 2%, but still, going into more detail than this makes that error even greater.
So unfortunately, a detailed breakdown of the climb is not possible until one knows the altitude and distances with greater certainty - at the moment, the figures just don’t match up. The mere fact that there is so much “disagreement” from one profile to the next, where the climb begins and ends, and what the gradient was means it’s pretty speculative to try to work out power output per kilometer. I was really hopeful this would be possible, because it would have been fascinating to track how Contador’s power peaked and then stabilised as he first followed, then attacked and built his lead.
Comparison between Contador and the history of the Tour
Nevertheless, it is still interesting to compare Contador’s climb to those of riders in the past. I said yesterday that Contador’s rate of 1900m/hour (based on the 8.7km @ 7.5% assumption, recall) was a record in the Tour. I know a lot of people have said that VAMs alone cannot be used to compare one climb to another. If you do so ‘blindly’, I agree, but provided you acknowledge that length of the climb and its gradient influences VAMs, as you’ll see below, then this analysis is still quite intriguing. It will reveal, for example, that Contador’s high VAM was achieved on the least steep of all the top 10 climbs in the history of the Tour. Therefore, on a steeper climb, it would be even higher. Yes, it was also a short climb, but more on that below.
If we go with the more conservative climb of 640m (as per SRM data), then the climbing rate is lower, at 1864m/hour. That is still a record in the Tour, mind you, as the graph below shows. This is a graph of the twelve highest VAMs ever in the Tour de France (click on it to enlarge if it’s too small):
So Contador surpasses Riis’ climb of Hautacam 13 years ago, as well as those of Pantani, Armstrong, Leblanc (a surprise name on this list!) and Ullrich. Just as an aside, Pantani’s form in 1997 was astonishing.
VAM and relative power output, and influence of gradient
VAM (or vertical ascent in meters per hour) is a measurement popularised by Dr Michele Ferrari (yes, that one) as a means of comparison between riders and climbs, because it can be used to calculate relative power output.
It is important to understand that VAM is affected by the gradient. According to Dr Ferrari himself, the higher the grade, the greater the VAM at a given power output. The relationship between VAM and relative power output is defined as follows:
Relative power (W/kg) = VAM (m/hour) / (Gradient factor x 100)
This gradient factor ranges between 2.6 for a gradient of 6% and 3.1 for a gradient of 11% (The gradient factor is equal to [2 plus (% grade/10)]. You can read more on this relationship here)
Implications for the Contador climb
This has implications for Contador’s climb. For Contador, the relative power output can be calculated by taking the VAM (1864m/h) and dividing by 275 (the constant for 7.5%). This gives a relative power output of 6.78 W/kg. (Ferrari calculates 6.73W/kg, but he uses a VAM of 1852m/h, because his ascent is 638m, not 640m. This shows again the discrepancies in measuring this Verbier climb!)
The point I have to make is that on a steeper climb, the same power output would produce an EVEN HIGHER VAM. Therefore, if you look at that graph above, Contador’s record VAM would have been higher on any of the other slopes – Alpe d’Huez at 8.1%, Hautacam at 7.7% and Joux Plane at 8.5% would produce higher VAMS. For example, had Contador been on an 8.5% slope, producing the same power output, his VAM would increase to 1932m/hour.
In other words, Contador’s climb was a record IN SPITE of the more gradual climb.
Confounders and explainers
There are a number of things that have to be factored into all these performances, particularly that of Contador. I touched on some yesterday, but here are some other contributing factors:
It’s been reported that there was quite a strong wind blowing up the valley on the climb. Alex very helpfully calculated what impact a wind would have on the required power output on the climb. It turns out that with NO WIND, the power output required on the climb is approximately 422W. A tail-wind speed of 3m/s (10km/hour) reduces the power output required to 387W, which is a pretty sizeable difference. Of course, the climb cannot have had a tailwind all the way up – it had hairpins and so there will have been headwinds and tailwinds. However, this is an average tailwind, and it seems reasonable. I tried to watch for signs of strong winds on the climb, but must confess it was not noticeable.
Also, in the graph above, there is no controlling for the wind. Perhaps LeBlanc had a mighty tail-wind on Hautacam in 1994? Perhaps Pantani faced a head-wind in 1997 and could even have been faster? It’s impossible to factor that in, which is why it can be risky making judgements in isolation! That is why averages over longer time-periods provide more meaningful information than once off events. The average power output on climbs over the course of a Tour tells you more than single climbs (but more on that in other posts). However, it’s safe to say that wind can have a substantial impact on climbing power calculated from ascent time.
Many have been quick to point out that the climbing rate should be higher, given that Verbier is a shorter climb than most of those done at the end of Tours. This is certainly a factor, since most of the climbs in the above list are 35 minutes long (Hautacam) or even longer (Alpe d’Huez). Soler’s climb in 2007 was short – 22 minutes, but the difference in length is certainly partly responsible. Therefore, Contador’s record VAM is at least partly due to a shorter climb.
I say “partly”, because I don’t believe that the effect of length is as great as many seem to believe. It’s certainly a factor, I don’t wish to dismiss it, but not as large as one might first thing. For example, when the Tour did the time-trial on Alpe d’Huez in 2004, the climbing times of all the main riders was only just marginally faster than when the same climb was done at the end of a 200km stage (all the other times in that list above). Similarly, long climbs like the Tourmalet and Mont Ventoux are climbed only a few percent slower than the shorter climbs, and so while length plays a role, and would account for some of Contador’s record ascent rate, it’s not as simple as saying “shorter equals faster”.
I will say that the way this Tour had gone, the first big finish was always going to be spectacular. The Tour was effectively dormant for 8 days, and the Pyrenees were done with minimal attrition. Therefore, given the situation and the way that the race had developed, the climb was always going to be fast. This again illustrates how isolated climbs can’t be taken out of context, and is the reason one should look at a collection of climbs to reduce the impact of these confounders as much as is possible.
Finally, I did mention in yesterday’s post that given the change in pro-cycling over the last few years, one would expect a drop in climbing rates, not new records. People will wonder about what this record ascent means – it’s only natural given cycling’s history!
I’ve hopefully managed to explain some of the other factors that must be considered in the Contador climb, but this question remains, without a doubt. It would be naive to dismiss it out of hand. I will say that performance analysis of single performances does not constitute proof of anything. In fact, it’s a weak method of inferring doping. That was never my intention in yesterday’s post, by the way (in case it came across that way). The better approach is to look at all climbs and work on averages, as I did for Tour winners from 1989 to 2001 in a previous post.
Why? Because doping has an effect on the repeatability of the performance, just as much as it affects performance acutely. Many will think only of the acute doping effect, but in fact, most of the doping products exert an even bigger effect on recovery, and hence the ability to produce this level of performance over and over. Think testosterone, growth hormone, cortisone, insulin – all are used to reduce stress response or improve post-exercise recovery. Even EPO would have this effect. Therefore, one cannot infer too much from a once-off performance. Rather, you have to look at a collection of performances, which also partly addresses variability provided by wind speed, temperatures and race situation.
In time, however, this performance will be placed into context – one of perhaps 10 climbs in the 2009 Tour, just as there may have been 10 climbs in 2008, 2002 or 1996. At that point, one will get a better idea of what is happening, and hopefully the analysis we did of the Tour winners 1989 to 2001 will be comparable to what is happening now.
That’s the short analysis of Contador’s climb. It was spectacular, without a doubt – a record in the Tour, even factoring in wind and climb length. There are too many unanswered questions regarding wind, absolute power, gradients and distances, however, which is a pity. Hopefully the discussion and the great debate it produces is worth the absence of a definitive answer! Certainly it has generated a lot of discussion, for which we thank you once again!
Bring on day 2 in the Alps!
This post is part of the thread: Tour de France Analysis – an ongoing story on this site. View the thread timeline for more context on this post.