VAM and direct comparison to Watts per Kg

[Merckx index]

Stage 11 , Plateau de Beille

Pantani : VAM 1724 m/h, 6.19 w/kg
Ullrich : VAM 1661 m/h, 5.96 w/kg

Stage 15 , Les Deux Alpes

Pantani : VAM 1699 m/h, 6.32 w/kg
Ullrich : VAM 1334 m/h, 4.96 w/kg

How did you come up with these numbers? VAM is directly proportional to watts/kg., so If Pantani had a higher VAM on Stage 11 than 15, how could he have a lower watts/kg? Your numbers show that proportionality comparing the two riders on the two stages, but something seems to be off comparing the two stages?

I know there are other factors like wind conditions, but VAM is all that could have been measured during a race, the watts/kg would have been calculated from VAM.

 

[Escarabajo]

...

Stage 16 , Col de la Madeleine

Pantani and Ullrich : VAM 1727 m/h, 6.26 w/kg

How is this possible for two riders with totally different weights? I don't have clips of that day but if they rode together these numbers are wrong IMHO. Usually W/kg numbers for Pantani were very high because he was small and skinny. Just saying.

 

[roundabout]

Probably normalized to a same weight.

 

[Escarabajo]

Probably normalized to a same weight.

Thats OK but then you have to specify because then the numbers don't mean anything.

 

[Rydberg]

How is this possible for two riders with totally different weights? I don't have clips of that day but if they rode together these numbers are wrong IMHO. Usually W/kg numbers for Pantani were very high because he was small and skinny. Just saying.

To a good approximation, for two riders going at the same speed on a steep climb, W/kg will be about the same. In this case, Pantani has lower Watts and lower mass, Ullrich has higher watts and higher mass, but W/kg are the same for both - no normalisation is needed.

If you were to be more accurate, you would find that Ullrich had higher W/kg because he needs to do relatively less work against the air etc, but at low climbing speeds this is not so important.

 

[Escarabajo]

To a good approximation, for two riders going at the same speed on a steep climb, W/kg will be about the same. In this case, Pantani has lower Watts and lower mass, Ullrich has higher watts and higher mass, but W/kg are the same for both - no normalisation is needed.

If you were to be more accurate, you would find that Ullrich had higher W/kg because he needs to do relatively more work against the air etc, but at low climbing speeds this is not so important.

If you were to be more accurate I'll bet you a dollar Pantani will always come up with the higher Watts/Kg.

Having said that you have a good point about the compensation estimation. But smaller guys will have the tendency to come up with higher watts/kg.

 

[Rydberg]

If you were to be more accurate I'll bet you a dollar Pantani will always come up with the higher Watts/Kg.

Having said that you have a good point about the compensation estimation. But smaller guys will have the tendency to come up with higher watts/kg.

If they were going at the same speed up the same hill, and not drafting each other, then you'll lose that dollar. Smaller guys having higher power to weight is the explanation as to why they climb faster. If they are climbing at the same speed, they are developing the same power to weight, or worse* since the bigger guy is doing relatively more work against the air resistance (surface area increases slowly with rider weight).

If your bet is about which rider usually had the higher power to weight, then because Pantani usually won those head to heads I agree with you. Pantani's climbing was usually better, because on those occasions he had a higher power to weight. But that one time on the Madelaine, they climbed with very similar power to weight.

Edit: * should be "better"!

 

[Magnus]

How did you come up with these numbers? VAM is directly proportional to watts/kg.

At what steepness?

 

[Merckx index]

At what steepness?

At any grade. Riders will have a particular grade at which their VAM is maximal, with falloff at gentler and at steeper grades, but then their watts/kg. also falls off. To reiterate what I said in an earlier post, VAM is directly proportional to watts/kg. You can, and usually do, calculate watts/kg from VAM values, excluding some factors that are generally quite minor. So, e.g., if you look at Science of Sport analyses (or any others) of particular climbs in the Tour, they will use VAM values to calculate wattage outputs of the various riders. Usually in such analyses, they calculate a value for a rider of a fixed weight, such as 70 kg., so you will see values like 390 watts or 425 watts, etc. But they arrive at these values from watts/kg. values, which are then multiplied by a constant like 70 kg. to give total watts. These watts/kg values in turn are derived from VAM values.

So if two riders finish together on a climb, they have the same watts/kg as well as VAM. Pantani was generally a better climber than Ulle (who was no slouch at that, of course), and this can be attributed to his lighter weight and greater watts/kg. But when they stayed together on a climb, they were putting out identical watts/kg numbers.

Of course, watts/kg can be measured more precisely in a laboratory, but out on the road in a race this is generally not possible, and VAM gives a very close approximation, if the climb has no false flats and is in a common grade range for its entire length.

 

[Escarabajo]

If they were going at the same speed up the same hill, and not drafting each other, then you'll lose that dollar. Smaller guys having higher power to weight is the explanation as to why they climb faster. If they are climbing at the same speed, they are developing the same power to weight, or worse since the bigger guy is doing relatively less work against the air resistance (surface area increases slowly with rider weight).

If your bet is about which rider usually had the higher power to weight, then because Pantani usually won those head to heads I agree with you. Pantani's climbing was usually better, because on those occasions he had a higher power to weight. But that one time on the Madelaine, they climbed with very similar power to weight.

Hypothetical case: Herrera (My Avatar) and Armstrong up the Alpe the Huez. I used the clean value from Herrera's ride back in the 80's of 41.83 minutes on a hot day with an average density of air close to 1 kg/m3. I used the weight of Armstrong to be around 163 lbs versus Herrera of 140 lbs. I assumed no drafting, 3 kph constant head wind riding side by side. 3% mechanical losses. The results are as follows:

Armstrong: 426 Watts for 5.76 watts/kg
Herrera: 378 Watts for 5.95 Watts/kg

I have a program but as you probably know anybody can do these calculations in the quizzillion programs out there. Some of them are as follows:

http://www.oocities.com/mdetting/sports/cycling.html

http://www.rst.mp-all.de/bergauf.htm

http://www.mne.psu.edu/lamancusa/ProdDiss/Bicycle/bikecalc1.htm

I want my dollar.

 

[Escarabajo]

Hypothetical case: Herrera (My Avatar) and Armstrong up the Alpe the Huez. I used the clean value from Herrera's ride back in the 80's of 41.83 minutes on a hot day with an average density of air close to 1 kg/m3. I used the weight of Armstrong to be around 163 lbs versus Herrera of 140 lbs. I assumed no drafting, 3 kph constant head wind riding side by side. 3% mechanical losses. The results are as follows:

Armstrong: 426 Watts for 5.76 watts/kg
Herrera: 378 Watts for 5.95 Watts/kg

I have a program but as you probably know anybody can do these calculations in the quizzillion programs out there. Some of them are as follows:

http://www.oocities.com/mdetting/sports/cycling.html

http://www.rst.mp-all.de/bergauf.htm

http://www.mne.psu.edu/lamancusa/ProdDiss/Bicycle/bikecalc1.htm

I want my dollar.

Now I had to increase Armstrong frontal area by 30% to match Herrera's numbers due to the increase in drag power, but I think that is forcing the issue too much. I used a theorethical formula to estimate the frontal area (Uses weight and height) and I got around 10% increment only.

Again we are splitting hairs here.

 

[Rydberg]

Hypothetical case: Herrera (My Avatar) and Armstrong up the Alpe the Huez. I used the clean value from Herrera's ride back in the 80's of 41.83 minutes on a hot day with an average density of air close to 1 kg/m3. I used the weight of Armstrong to be around 163 lbs versus Herrera of 140 lbs. I assumed no drafting, 3 kph constant head wind riding side by side. 3% mechanical losses. The results are as follows:

Armstrong: 426 Watts for 5.76 watts/kg
Herrera: 378 Watts for 5.95 Watts/kg

I have a program but as you probably know anybody can do these calculations in the quizzillion programs out there. Some of them are as follows:

http://www.oocities.com/mdetting/sports/cycling.html

http://www.rst.mp-all.de/bergauf.htm

http://www.mne.psu.edu/lamancusa/ProdDiss/Bicycle/bikecalc1.htm

I want my dollar.

Ok, you win the dollar. I made a mistake in my reasoning: when I said the smaller guy's P:W is worse, what I was actually thinking was that for the same power to weight he would go slower up the hill, and then I wrote down the wrong thing. Basically, being big with a given P:W is always better because the higher absolute power helps. I do actually have a dollar you can have!

 

[Escarabajo]

Ok, you win the dollar. I made a mistake in my reasoning: when I said the smaller guy's P:W is worse, what I was actually thinking was that for the same power to weight he would go slower up the hill, and then I wrote down the wrong thing. Basically, being big with a given P:W is always better because the higher absolute power helps. I do actually have a dollar you can have!

No worries.

Good discussion. I bet it wil come back agin during the Giro or the Tour somehow.

 

[halamala]

How is this possible for two riders with totally different weights? I don't have clips of that day but if they rode together these numbers are wrong IMHO. Usually W/kg numbers for Pantani were very high because he was small and skinny. Just saying.

The relationship between VAM and relative power output is expressed as follows:

Relative power (Watts/kg) = VAM (meters/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%

To work out the gradient factor take 2 + (% grade/10)

http://en.wikipedia.org/wiki/Velocity_Ascended,_Metres_per_hour

 

[Magnus]

At any grade.

Well, clearly VAM and watt/kg aren't proportional when riding in the flat since your VAM will be zero in that case, but your watt/kg will not be constant?

 

[Escarabajo]

http://en.wikipedia.org/wiki/Velocity_Ascended,_Metres_per_hour

Don't worry Halamala, I don't use the VAM to get to my watts/kg calculation because it omits some of the basics of physics. It is a good approximation but it is flawed. When you use the equation of state you reduce the error when compare with the VAM calculation.

In this age of computers, why not take advantage of them and do the full calculations. I accept it if you are in front of the TV and you want to do a quick calculation, but not when you are going to publish numbers to the media. Note that Ferrari usually refers to VAM numbers comparatively and not the watts/kg. When you use it as a relative measure against another similar number, then it is OK also. I do it all the time in my day to day work. But it is not good for numbers that will calculate watts/kg that will last in history.

So in summary, you will have numbers to compare performances against, the VAM numbers and the watts/kg numbers calculated by the equation of state. They can be done independently. Of course, the best method would be the by using a power meter, but we know the data is very limited and we are only left with calculations that contain larger error.

 

[Merckx index]

Well, clearly VAM and watt/kg aren't proportional when riding in the flat since your VAM will be zero in that case, but your watt/kg will not be constant?

That's when "other factors" that I mentioned come into play. Such as wind resistance, which can to a good approximation be neglected on a steep climb where the rider isn't going that fast, but which of course becomes critical in the flat. If there were no wind resistance, or other resistance like friction, the rider's speed on a flat or 0 % grade would in fact be infinite (this is the mathematical conclusion; in the real world, if there were no friction, the bicycle could not be accelerated in the first place).

 

[CowboyTx]

I don't have a powermeter to work out my wattage but I use a local very long hill regularly and put my details into the relatively simple
Calculate cycling VAM equation.

It doesn't allow for hub friction, wind resistance, tarmac quality etc but it will give me a consistent set of figures to compare as my weight changes.