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Power Data Estimates for the climbing stages

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Mar 18, 2009
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the sceptic said:
Lets say Martin was doing 470 watts today, similar to the dauphine
If Froome produced the same power,

Given that his CdA is undoubtedly lower, he wouldn't have to.

the sceptic said:
that makes his w/kg sky high doesnt it? Almost the magical 7w/kg
(yes i know im just a pseudo scientist)

No comment.
 
Oct 17, 2011
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the sceptic said:
Lets say Martin was doing 470 watts today, similar to the dauphine
If Froome produced the same power, that makes his w/kg sky high doesnt it? Almost the magical 7w/kg
(yes i know im just a pseudo scientist)

It's hard to compare power output in TT because of the difference in aerodynamics. That's why comparisons on climbs are preferred because aerodynamics are less relevant there.

But yes for sure Froome's w/kg is sky high indeed.
 
Mar 19, 2009
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Tyler'sTwin said:
Maybe instead of estimating JV's undoped 1h FTP, based on Coggan's estimate of JV's undoped 20 min threshold, based on JV's estimate of his Ventoux TT and his claimed gains from EPO, maybe someone should just ask him what his undoped 1h FTP was? Well, as it turns out, someone did, and JV said his FTP was 5.8-6.0 W/kg (360 W, 60-62 kg). Aren't you glad you don't have to speculate anymore?

heart_attack_man said:
LOL @ Vaughters quote here from last year RE: Climbing Times being 10% slower. Slightly nescient based on what we saw in Stage 8... :rolleyes:
I dont believe Vaughters is completely honest about everything. :) He mixes alot of truth in to what he says, which is more convincing compared to say, Brailsford.

Well its hard to imagine we will see more impressive all out efforts from Froome, sadly because Contador failed to stay close to him. I think we may have to see the 2nd best climbing performance in the Alps rather than the best from this batch of riders.

acoggan said:
But, but, but...how can that be?!? After all (to quote Joe Lindsey), "what we’re dealing with here isn’t pseudo-science at all: it’s physics".
When I look at Strava records it never ceases to amaze me how low the given power numbers are. I could go and set a sprint time with my SRM averaging 1,100 watts and some guy at the top of the leader board has an average of 350.
 
May 8, 2009
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the sceptic said:
Lets say Martin was doing 470 watts today, similar to the dauphine
If Froome produced the same power, that makes his w/kg sky high doesnt it? Almost the magical 7w/kg
(yes i know im just a pseudo scientist)

If you're getting the 470W figure (471W) from http://www.cyclingpowerlab.com/ProRaceAnalysis.aspx you'll see they estimate a much more modest 436W for today. To me this just says the error bars are very big
 
Mar 13, 2009
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Alex Simmons/RST said:
Strava estimates are good for some light comic relief and that's about it.

Estimates of power from a TT, when you have no idea of the rider's aerodynamics, let alone the wind conditions, are going to be no more than wild stabs in the dark.

When you see how strava calculates, you'll understand why they are out by so much. This is the general "you", not specific to you Alex. VAM will be close, they take the top and bottom off google maps and the time is known. There are errors as Google is not perfect. However to get power, Strava calculates instant power, and then integrates for the climb. However between the inaccuracies in google and GPS, this means a constant gradient/power climb, may be interpretted as falling off a cliff and then instantly climbing it again, and being stopped and then at 60kph. It will vary from ride to ride. From strava, believe the VAM as being pretty close and forget the power.
 
Apr 11, 2013
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Tyler'sTwin said:
https://twitter.com/Vaughters/status/225617454045478913
1999 dauphine, ventoux stage: VAM 1912, w/kg 6.8.... See why I feel cycling is clean now?

This VAM number doesn't make sense.

VAM = (metres ascended x 60) / Minutes it took to ascend
VAM = (1598x60) / 56.85
VAM = 1687
http://autobus.cyclingnews.com/results/1999/jun99/dauphine993.html

if his power was 6.8w/kg :confused:
VAM = Relative power (Watts/kg) x (Gradient factor x 100)
VAM = 6.8 x 275
VAM = 1870

Maybe it's his mistake cause the elevation of Ventoux is 1912, maybe it's just for the part of the ITT. Who knows...
 
Sep 29, 2012
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RocketScientist said:
This VAM number doesn't make sense.

VAM = (metres ascended x 60) / Minutes it took to ascend
VAM = (1598x60) / 56.85
VAM = 1687
http://autobus.cyclingnews.com/results/1999/jun99/dauphine993.html

if his power was 6.8w/kg :confused:
VAM = Relative power (Watts/kg) x (Gradient factor x 100)
VAM = 6.8 x 275
VAM = 1870

Maybe it's his mistake cause the elevation of Ventoux is 1912, maybe it's just for the part of the ITT. Who knows...

JV also thinks a 15W saving for a 6 hour race equates to 1000kCal saved (vs 324 actually saved). Said as much in front of scientists and other intelligentsia at a TedX talk. Maths is probably not his strong suit.

The tweet mentioned above was more about the fact that the peloton has slowed down when going uphill. Given the average speed overall is unchanged, they must be descending and riding the flats faster. TT speed certainly doesn't appear to have diminished much at all. Not 10% at any rate.

And then Froome threw a stick in the spokes with his recent Ax3 ascent.

Keep the narrative in mind and most things make sense, despite their lack of accuracy.
 
Mar 18, 2009
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karlboss said:
When you see how strava calculates, you'll understand why they are out by so much. This is the general "you", not specific to you Alex. VAM will be close, they take the top and bottom off google maps and the time is known. There are errors as Google is not perfect. However to get power, Strava calculates instant power, and then integrates for the climb. However between the inaccuracies in google and GPS, this means a constant gradient/power climb, may be interpretted as falling off a cliff and then instantly climbing it again, and being stopped and then at 60kph. It will vary from ride to ride. From strava, believe the VAM as being pretty close and forget the power.

That's not how it was explained to me (when we were in discussions about how I might be able to help them).
 
Aug 13, 2009
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acoggan said:
It's the same physics.

Really? Please, share with us the formula that Strava uses. Do you really think it is the same level of precision as what Tucker or Vayer would produce with Froome's SRM file? Really?
 
Mar 18, 2009
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Race Radio said:
Really? Please, share with us the formula that Strava uses.

Sorry, we signed mutual NDAs.

Race Radio said:
Do you really think it is the same level of precision as what Tucker or Vayer would produce with Froome's SRM file? Really?

There's nothing magic to such calculations, as the physics are rather simple and in fact have been used since at least the 1970s (although it wasn't until 1998 that this type of approach was directly validated: http://academia.edu/239368/Martin_J...cycling_power._J_Appl_Biomech_1998_14_276-291). Thus, unless you're royally stuffing things up for some reason, any imprecision lies in uncertainties regarding the input values, and how they interact, and not in the algorithm itself.

(BTW, I don't think you actually meant Froome's SRM file, since if we had that there would no reason to try to estimate his power based on his climbing speed.)
 
acoggan said:
(BTW, I don't think you actually meant Froome's SRM file, since if we had that there would no reason to try to estimate his power based on his climbing speed.)

Of course there would !!! The SRM can go wrong for a number of reasons while, if you ignore the aero component, the calculation will always be pretty close to the true value (if you do your homework correctly).
 
Mar 18, 2009
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Le breton said:
Of course there would !!! The SRM can go wrong for a number of reasons while, if you ignore the aero component, the calculation will always be pretty close to the true value (if you do your homework correctly).

Yes, I was assuming that any SRM data would be correct.
 
Mar 13, 2009
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acoggan said:
That's not how it was explained to me (when we were in discussions about how I might be able to help them).

https://strava.zendesk.com/entries/20959332-power-calculations

and I say they take point by point and integrate as otherwise acceleration plays no part in the calculation.

However if you've seen the actual calculation used and is significantly different, i guess I'm wrong and they publish nonsense. The only other difference is that they do just average the whole lot over the climb and ignore acceleration. Which would yield similar number to anything from analytical cycling etc. The equations are the same all they can play with are the variables.
 
Mar 13, 2009
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Ventoux:
Irizar from SRM 324W at 76kg 15.67kph
Froome 22.86kph
Assuming power to weight is directly proportional (324/76)/(15.67/22.86)=5.95Wkg

Take from it what you will, I'm not claiming any sort of accuracy with this method, I already know of a number of them.
 
Dear Wiggo said:
JV also thinks a 15W saving for a 6 hour race equates to 1000kCal saved (vs 324 actually saved). Said as much in front of scientists and other intelligentsia at a TedX talk. Maths is probably not his strong suit.
.
lol someone doesn't know the difference between joules and calories :eek:

Fail.
 
karlboss said:
Ventoux:
Irizar from SRM 324W at 76kg 15.67kph
Froome 22.86kph
Assuming power to weight is directly proportional (324/76)/(15.67/22.86)=5.95Wkg

Take from it what you will, I'm not claiming any sort of accuracy with this method, I already know of a number of them.

Greg Henderson tweeted he had a strong tailwind for the climb.

Assuming that's the case, I suggest dropping estimated W/kg numbers by at least 0.5W/kg, if not more.
 
Apr 16, 2009
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Alex Simmons/RST said:
Greg Henderson tweeted he had a strong tailwind for the climb.

Assuming that's the case, I suggest dropping estimated W/kg numbers by at least 0.5W/kg, if not more.

Ten Dam said there was a headwind, as did the commentators (Phil and Paul). I suggest we add 0.5W/kg to the estimates. :)
 
Mar 4, 2010
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Mar 13, 2009
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Alex Simmons/RST said:
Greg Henderson tweeted he had a strong tailwind for the climb.

Assuming that's the case, I suggest dropping estimated W/kg numbers by at least 0.5W/kg, if not more.

Original data is irizar's SRM, so no adjustment needed using this method at least for Irizar. Are you saying linearly interpolating from this data I should knock off .5 as there was a tailwind? That seems odd. That would imply it affected Froome but not Irizar