Normalized power question



msummers

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Jun 27, 2005
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I did a 40 minute interval over hilly terrain trying my best to hold about 200 watts. At the end of the ride, it turned out that my normalized power was 219. I noticed that for 37 minutes of the ride I held a normalized power of 210, then the last three minutes of the interval had a short steep hill that took 40 seconds to climb at a max of 702w and an average of 442w. I was surprised to see that this relatively short event had such an impact on the overall NP for the whole 40 minutes. How is the accuracy of NP when this occurs? BTW the real average was 200w with or without the hill.

mikey
 

objective

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Jul 5, 2005
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msummers said:
I did a 40 minute interval over hilly terrain trying my best to hold about 200 watts. At the end of the ride, it turned out that my normalized power was 219. I noticed that for 37 minutes of the ride I held a normalized power of 210, then the last three minutes of the interval had a short steep hill that took 40 seconds to climb at a max of 702w and an average of 442w. I was surprised to see that this relatively short event had such an impact on the overall NP for the whole 40 minutes. How is the accuracy of NP when this occurs? BTW the real average was 200w with or without the hill.

mikey
Sounds fine to me. How did you think your NP would be effected?
 

frenchyge

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Apr 3, 2005
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msummers said:
How is the accuracy of NP when this occurs? BTW the real average was 200w with or without the hill.
My personal experience is that NP pretty accurately predicts when I will hit a physical limit for lots of different types of rides.

I don't think it's all that surprising that you were able to "kick it" for the last 3 minutes and increase the NP for the entire interval. I'm pretty confident that you could have held 219w for the entire period if you had tried.
 

msummers

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Jun 27, 2005
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objective said:
Sounds fine to me. How did you think your NP would be effected?
Just sounds strange that an effort for 1.8% (40 secs) of the total (37 min) could increase the total normalized power for the entire ride by 4.29% (210 to 219). I'm not doubting the concept, just trying to understand it better.

mikey
 

frenchyge

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msummers said:
I'm not doubting the concept, just trying to understand it better.
Normalized power differs from average power in that it attempts to quantify the physiological impact of the ride. Physiological strain does not increase linearly with power output. Instead, it is approximated by a 4th-order function of power output, which means that more intense efforts have a much greater impact on your muscles (and normalized power) than a steady effort at a lower power.

For more details, see: http://www.cyclingpeakssoftware.com/defined.html

- or -
http://www.cyclingpeakssoftware.com/PowerTrainingChapter.pdf

That last 3 minutes probably kicked the legs pretty good, right? Could you have kept riding at 200w after that?
 

msummers

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Jun 27, 2005
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frenchyge said:
Normalized power differs from average power in that it attempts to quantify the physiological impact of the ride. Physiological strain does not increase linearly with power output. Instead, it is approximated by a 4th-order function of power output, which means that more intense efforts have a much greater impact on your muscles (and normalized power) than a steady effort at a lower power.

For more details, see: http://www.cyclingpeakssoftware.com/defined.html

- or -
http://www.cyclingpeakssoftware.com/PowerTrainingChapter.pdf

That last 3 minutes probably kicked the legs pretty good, right? Could you have kept riding at 200w after that?
I see your your point frenchy. Then I wonder if doing a hilly 40K tt or road race and looking at your NP is a better indication of what you can actually do on a flat tt or road race if you could push yourself that hard. No doubt this probably has been discussed to many times already, but it does make sense.
 

frenchyge

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msummers said:
I see your your point frenchy. Then I wonder if doing a hilly 40K tt or road race and looking at your NP is a better indication of what you can actually do on a flat tt or road race if you could push yourself that hard. No doubt this probably has been discussed to many times already, but it does make sense.
For a highly variable ride, NP is much better than AP, IMO. Even a flat road race or crit (or heck, club ride) is going to be somewhat variable, so I use NP for all outdoor rides, personally. I use AP for assessing shorter duration intervals, or trainer intervals.
 

grom

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Dec 30, 2004
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frenchyge said:
For a highly variable ride, NP is much better than AP, IMO. Even a flat road race or crit (or heck, club ride) is going to be somewhat variable, so I use NP for all outdoor rides, personally. I use AP for assessing shorter duration intervals, or trainer intervals.
i never use ap any more, i even went back through my training logs and created a new row in my excel spreadsheet for NP cause it rocks :cool: now i am trying to get this IF and tss comparison going
 

Woofer

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Dec 31, 2004
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msummers said:
I see your your point frenchy. Then I wonder if doing a hilly 40K tt or road race and looking at your NP is a better indication of what you can actually do on a flat tt or road race if you could push yourself that hard. No doubt this probably has been discussed to many times already, but it does make sense.
That is almost exactly what the web page french linked to says.

Just as another data point I did a three hour ride with only fifteen minutes of L6 intervals in it and it had a higher NP than my regular two hour ride with fifty minutes of L4 intervals. It does seem strange until you look at the formula.