# Help me interpret some power numbers...



## OldZaskar (Jul 1, 2009)

Pretty new to power - starting to amass some data... definitely in the early stages of the learning curve. I'm using Cheetah to analyze the data (Mac user).

Today was a very tough group ride; probably 60+ guys, very fast, established ride with paces in the 23-25 mph; today was very windy, dropped the pace to 22.6 mph over 50 miles. I took at least my share of turns at the front. Obviously these efforts were much higher than in the pack and made tougher because of the wind.

So that data...
- 51 miles
- Avg. power: 250
- Xpower: 268 (really have no idea what "Xpower" is)

The part I'm trying to figure out is how a group ride effects averages. The ride felt much harder than 250 watts. Is this where "normalized" power comes into play?

Thanks for any insights.


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## Rhino4Five (Nov 5, 2009)

OldZaskar said:


> Pretty new to power - starting to amass some data... definitely in the early stages of the learning curve. I'm using Cheetah to analyze the data (Mac user).
> 
> Today was a very tough group ride; probably 60+ guys, very fast, established ride with paces in the 23-25 mph; today was very windy, dropped the pace to 22.6 mph over 50 miles. I took at least my share of turns at the front. Obviously these efforts were much higher than in the pack and made tougher because of the wind.
> 
> ...


I dont' use GC, but a quick web search says that Xpower is very similar to normalized power. My understanding is that normalized power is the power output you COULD HAVE maintained if you weren't having spikes and drops in your power. See the link to Andy Coggen's article below.

If you're new to power, I highly recommend getting the book "Racing and Training With a Power Meter" and join the Wattage Google group.

Unless you're riding on an indoor trainer, your avg power and normalized power are going to differ.

TrainingPeaks | Normalized Power, Intensity Factor & Training Stress Score


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## OldZaskar (Jul 1, 2009)

Rhino4Five said:


> My understanding is that normalized power is the power output you COULD HAVE maintained if you weren't having spikes and drops in your power.


That actually makes perfect sense. And, usually wouldn't believe a program could predict or estimate what I could have maintained... but recently I did a solo 40 at 270 watts... kinda fits with that normalized 268 over 50. Huh... pretty cool. 

Thanks!


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## sdeeer (Aug 12, 2008)

xpower is only valid if your FTP is accurate as well FYI.

If your FTP is good, then xpower for 1 hour is good as well.


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## hrumpole (Jun 17, 2008)

sdeeer said:


> xpower is only valid if your FTP is accurate as well FYI.
> 
> If your FTP is good, then xpower for 1 hour is good as well.



That simply cannot be true. Xpower (like normalized power) is a rolling average average of the power exerted. It doesn't matter for purposes of that equation what FTP is. Where it matters is in computing the TSS or BikeScore for the ride; if FTP is too low, then bikescore will be too high, and vice versa. If your xpower for 3 hours is 240, and FTP is set at 240, then TSS/BikeScore for the ride will be way too high.


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## sdeeer (Aug 12, 2008)

hrumpole said:


> That simply cannot be true. Xpower (like normalized power) is a rolling average average of the power exerted. It doesn't matter for purposes of that equation what FTP is. Where it matters is in computing the TSS or BikeScore for the ride; if FTP is too low, then bikescore will be too high, and vice versa. If your xpower for 3 hours is 240, and FTP is set at 240, then TSS/BikeScore for the ride will be way too high.


Yeah......I don't know what I was thinking. I guess I was posting without (fully) thinking......or at least re-calling.


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