the notion of a "normalized" watt?
03-26-07, 11:30 AM
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the notion of a "normalized" watt?
I was thinking in the car this morning (I know, bad idea), about bdcheung's race report (https://bikeforums.net/showthread.php?t=281136) and his norm power was 245W. For a bigger guy like myself, 245 watts isn't a race-pace (more like 20mph). I'm pretty sure he was going faster than that. So that lead to me thinking that a watt of power for me doesn't equal the same result as someone else. Bdcheung's 245w might equate to 300w for someone my size and weight to do the same.
So how do we normalize watts? Is it something simple like divide by the rider's weight? Or more complex, taking into account the bike ridden, etc?
(or am I overthinking?)
So how do we normalize watts? Is it something simple like divide by the rider's weight? Or more complex, taking into account the bike ridden, etc?
(or am I overthinking?)
03-26-07, 11:34 AM
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You can compare watts of different sized riders by comparing w/kg.
However the concept of "normalized power" is something different. It's an attempt to take out fluctuations in the effort to give a more accurate indication of the effort.
Training with Power, or the Cycling Peaks website can give a more scientific explanation of how normalized power is calculated.
However the concept of "normalized power" is something different. It's an attempt to take out fluctuations in the effort to give a more accurate indication of the effort.
Training with Power, or the Cycling Peaks website can give a more scientific explanation of how normalized power is calculated.
03-26-07, 11:34 AM
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nevermind, I didn't google enough before posting. Oops.
https://www.cyclingpeakssoftware.com/...11/defined.asp
Originally Posted by Cycling Peaks
Although normalized power is a better measure of training intensity than average power, it does not take into account differences in fitness within or between individuals. CyclingPeaks therefore also calculates an intensity factor (IF) for every workout or time range analyzed. IF is simply the ratio of the normalized power as described above to your threshold power (entered under "Athlete Settings" at your "Athlete Home").
03-26-07, 11:38 AM
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Normalized power is more complicated than that, and is really intended to address the incaccuracies of average power. For instance, if you ride at recovery pace for an hour but throw in 4 1200-watt sprints, the average power will be deceptive.
Here's the quick Allen/Coggan blurb about Normalized Power:
"We calculate NP by (1) starting 30 seconds into the wattage data and calculating a 30-second rolling average for powerl (2) raising the values obtained in step 1 to the fourth power; (3) taking the average of all the values obtained in step 2; and (4) taking the fourth root of the number obtained in step 3...
...Basically, it's an estimate of the wattage you would've averaged if you had pedaled smoothly for the entire effort--the power your body 'thinks' it is doing, though in reality the effort could have been a very sporadic 'on/off' race... Because of the factors it takes into account, Normalized Power provides a better measure than average power of the true physiological demands of a given training session."
Here's the quick Allen/Coggan blurb about Normalized Power:
"We calculate NP by (1) starting 30 seconds into the wattage data and calculating a 30-second rolling average for powerl (2) raising the values obtained in step 1 to the fourth power; (3) taking the average of all the values obtained in step 2; and (4) taking the fourth root of the number obtained in step 3...
...Basically, it's an estimate of the wattage you would've averaged if you had pedaled smoothly for the entire effort--the power your body 'thinks' it is doing, though in reality the effort could have been a very sporadic 'on/off' race... Because of the factors it takes into account, Normalized Power provides a better measure than average power of the true physiological demands of a given training session."
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03-26-07, 11:51 AM
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good info as always, Doc. W/kg is what I couldn't put my finger on, and I think that's what I was looking for. So yeah, like I totally averaged 1.28w/kg on my ride yesterday. It was suhweet.
03-26-07, 11:53 AM
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Originally Posted by superdex
good info as always, Doc. W/kg is what I couldn't put my finger on, and I think that's what I was looking for. So yeah, like I totally averaged 1.28w/kg on my ride yesterday. It was suhweet.
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03-26-07, 11:54 AM
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Originally Posted by Allen/Coggan
Here's the quick blurb about Normalized Power:
"We calculate NP by (1) starting 30 seconds into the wattage data and calculating a 30-second rolling average for power (2) raising the values obtained in step 1 to the fourth power; (3) taking the average of all the values obtained in step 2; and (4) taking the fourth root of the number obtained in step 3...
"We calculate NP by (1) starting 30 seconds into the wattage data and calculating a 30-second rolling average for power (2) raising the values obtained in step 1 to the fourth power; (3) taking the average of all the values obtained in step 2; and (4) taking the fourth root of the number obtained in step 3...
I don't know why it isn't built into power agent 7.0
03-26-07, 11:56 AM
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Originally Posted by krazyderek
Yup
I don't know why it isn't built into power agent 7.0
I don't know why it isn't built into power agent 7.0
CyclingPeaks just has a ton of great info that PowerAgent 7 doesn't have, so I'd say it's worth the $99 if you're serious about training...
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03-26-07, 11:58 AM
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Originally Posted by DrPete
Just casually overlook that I'm dividing by 91kg and the power numbers look pretty good.
03-26-07, 12:07 PM
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can you copyright a calculation? or just the name you give it? I'm sure cycle-ops could implement the calculation with a different name, like " X-power" for "extrapolated power"
03-26-07, 12:20 PM
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Get "Lance Armstrong's War" Despite the allegations against him, Dr. Ferrari had some amazing ideas. One of them is the idea of measuring the true power of a rider (like watts/kg).
03-26-07, 12:25 PM
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Originally Posted by superdex
I was thinking in the car this morning (I know, bad idea), about bdcheung's race report (https://bikeforums.net/showthread.php?t=281136) and his norm power was 245W. For a bigger guy like myself, 245 watts isn't a race-pace (more like 20mph). I'm pretty sure he was going faster than that. So that lead to me thinking that a watt of power for me doesn't equal the same result as someone else. Bdcheung's 245w might equate to 300w for someone my size and weight to do the same.
So how do we normalize watts? Is it something simple like divide by the rider's weight? Or more complex, taking into account the bike ridden, etc?
(or am I overthinking?)
So how do we normalize watts? Is it something simple like divide by the rider's weight? Or more complex, taking into account the bike ridden, etc?
(or am I overthinking?)
How about normalizing it to speed or total weight(i.e. body weight plus full bike weight)?
03-26-07, 12:28 PM
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Originally Posted by krazyderek
can you copyright a calculation? or just the name you give it? I'm sure cycle-ops could implement the calculation with a different name, like " X-power" for "extrapolated power"
However, there's also the issue of patent protection. You can patent inventions that include software, and systems. So it's possible Cycling Peaks could not only copyright the expression of the idea ("Normaized Power') but also seek patent protection of the method of calculating it. To do that they'd have to show it really is a new invention, not just an obvious improvement of something already existing.
03-26-07, 12:32 PM
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Originally Posted by krazyderek
can you copyright a calculation? or just the name you give it? I'm sure cycle-ops could implement the calculation with a different name, like " X-power" for "extrapolated power"
Yes you can. You can also put a patent on it. Weight Watchers has their formula for the "points system" patented. Of course you can just look up the patent and use the formula anyway. You just can't sell it.
03-26-07, 12:37 PM
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Originally Posted by slowandsteady
Yes you can. You can also put a patent on it. Weight Watchers has their formula for the "points system" patented. Of course you can just look up the patent and use the formula anyway. You just can't sell it.
03-26-07, 01:17 PM
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Originally Posted by slowandsteady
Yes you can. You can also put a patent on it. Weight Watchers has their formula for the "points system" patented. Of course you can just look up the patent and use the formula anyway. You just can't sell it.
03-26-07, 01:42 PM
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Originally Posted by Enthalpic
Well you can't patent something that is common knowledge to those in the field. Normalization functions are well known to scientists and can't be patented. The application of the formula to cycling and the development of training programs / software can be.
Very true.
03-26-07, 03:20 PM
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Originally Posted by DrPete
I think it's because the calculation is actually owned by Allen and Coggan, because even in their book there's a trademark sign after it.
CyclingPeaks just has a ton of great info that PowerAgent 7 doesn't have, so I'd say it's worth the $99 if you're serious about training...
CyclingPeaks just has a ton of great info that PowerAgent 7 doesn't have, so I'd say it's worth the $99 if you're serious about training...
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03-27-07, 06:09 AM
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Originally Posted by DrPete
...Basically, it's an estimate of the wattage you would've averaged if you had pedaled smoothly for the entire effort
e.g. if my 30 second average wattage readings are: 100 100 100 600 100
Average wattage = 1000/5 = 200W, i.e. the wattage you would have averaged if you had pedalled smoothly.
Normalised power = ((100^4)+ (100^4)+ (100^4)+ (600^4)+ (100^4)) /5 ^ (1/4)
= (1.3 x 10^11) /5 ^ (1/4)
= 401
It's interesting that they chose the 4th power - any theoretical reasons why, other than it sort of works in practice?
The cube root of the wattages could also be useful because power increase with speed is roughly cubic, meaning that the cube root normalised power would represent roughly the power you would need to put out to go at roughly the same speed round the course if you had ridden completely smoothly. For the example above it calculates 157watts, which seems reasonable.
03-27-07, 10:30 AM
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Originally Posted by mrfish
I don't quite know what to call it
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03-27-07, 10:39 AM
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Originally Posted by mrfish
This is misleading. Because you raise the numbers to the fourth power, the big numbers get bigger and have a disproportionate weighting on the calculation. I don't quite know what to call it, but it's not an average as most people understand...
It's interesting that they chose the 4th power - any theoretical reasons why, other than it sort of works in practice?
It's interesting that they chose the 4th power - any theoretical reasons why, other than it sort of works in practice?
Originally Posted by Allen and Coggan, "Training and Racing with a Power Meter"
As stated before, the act of riding, training, and racing a bicycle is a highly variable, almost stochastic, exercise. There are many factors that affect every ride you take: wind, uphills, downhills, quick accelerations, long steady grinding, and so on. Because of this variability, average power is just not a sufficient indicator of the true metabolic demands of your ride. To account for this variability, we developed a special algorithm to calculate an adjusted (or 'normalized') power for each ride or segment of a ride (longer than 30 seconds) that you may want to analyze.
The algorithm is somewhat complicated but it incorporates two key pieces of information: (1) the fact that physiologic responses to rapid changes in exercise intensity are not instantaneous but follow a predictable time course; and (2) the fact that many critical physiologic responses (e.g., glycogen utilization, lactate production, stress hormone levels, and the like) are curvilinearly, rather than linearly, related to exercise intensity.
The algorithm is somewhat complicated but it incorporates two key pieces of information: (1) the fact that physiologic responses to rapid changes in exercise intensity are not instantaneous but follow a predictable time course; and (2) the fact that many critical physiologic responses (e.g., glycogen utilization, lactate production, stress hormone levels, and the like) are curvilinearly, rather than linearly, related to exercise intensity.
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03-27-07, 10:45 AM
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Originally Posted by mrfish
This is misleading. Because you raise the numbers to the fourth power, the big numbers get bigger and have a disproportionate weighting on the calculation. I don't quite know what to call it, but it's not an average as most people understand.
e.g. if my 30 second average wattage readings are: 100 100 100 600 100
Average wattage = 1000/5 = 200W, i.e. the wattage you would have averaged if you had pedalled smoothly.
Normalised power = ((100^4)+ (100^4)+ (100^4)+ (600^4)+ (100^4)) /5 ^ (1/4)
= (1.3 x 10^11) /5 ^ (1/4)
= 401
It's interesting that they chose the 4th power - any theoretical reasons why, other than it sort of works in practice?
The cube root of the wattages could also be useful because power increase with speed is roughly cubic, meaning that the cube root normalised power would represent roughly the power you would need to put out to go at roughly the same speed round the course if you had ridden completely smoothly. For the example above it calculates 157watts, which seems reasonable.
e.g. if my 30 second average wattage readings are: 100 100 100 600 100
Average wattage = 1000/5 = 200W, i.e. the wattage you would have averaged if you had pedalled smoothly.
Normalised power = ((100^4)+ (100^4)+ (100^4)+ (600^4)+ (100^4)) /5 ^ (1/4)
= (1.3 x 10^11) /5 ^ (1/4)
= 401
It's interesting that they chose the 4th power - any theoretical reasons why, other than it sort of works in practice?
The cube root of the wattages could also be useful because power increase with speed is roughly cubic, meaning that the cube root normalised power would represent roughly the power you would need to put out to go at roughly the same speed round the course if you had ridden completely smoothly. For the example above it calculates 157watts, which seems reasonable.
