AP vs. NP

jsirabella said:

I am sure this question has been brought up before but I started to think about it today a bit as I have been a hermit lately and have been married to the CT without having to worry about the difference between these two numbers. I opened up my outdoor training with a 4 hour tempo ride up and back 9W and downloaded the data and again there was a sizeable difference between the two numbers.

Funny thing though I opended up old files aboput 6 months ago and my AP across the board for rides of 2 hours or more were up on all the peaks but my NP was up but not as much as my AP. It seems I was able to get the numbers closer together even with my busted toe this weekend which was a pain through the ride.

If NP is not important and AP is all the counts, why have NP? How do you folks look at both numbers?

-js

Can you clarify your question please. Some of the above isn't making much sense to me.

When you download a workout from your PM into WKO+ you will get your numbers for entire workout, peak 60 minute, 30 minute, 20 minute and within those number for each grouping you have Average Power and Normalized Power. Normalized Power is defiined and calculated here:

cyclingpeakssoftware.comdefined.aspOpen ↗

Normalized Power is what your power would be if you "in essence, it is an estimate of the power that you could have maintained for the same physiological "cost" if your power output had been perfectly constant (e.g., as on a stationary cycle ergometer), rather than variable."

Do most people use the Normalized Power Number or Average Power Number when calculating their FTP. In many cases for me here, I usually have a substantial difference between the two numbers. I.e for yesterday 3 1/2 hour ride I had a peak 60 minute of 220 AP but a 270NP....so which number counts? How do you folks look at it.

For me personally six months ago my AP and NP were much further apart. It seems now my AP has shot up but my NP just not as much. In the example above my AP and NP for only a 2 1/2 hour ride was 180AP and 250NP. I believe for me that is saying I am able to give a steadier more countrolled output compared with six months ago.

Just as an FYI, last week I verified my FTP of 260. I dialed in 260 on the CT using the bike with my PM and both had AP for one hour of 260 and NP of 260.

On the CT there is no (or should be little to no difference) between your AP and NP if you dial in one number for one hour. I have a feeling I know what swampy and Tyson would say, I wonder how the rest look at it.

I hope it cleared it up...

-js

Alex Simmons said:

Can you clarify your question please. Some of the above isn't making much sense to me.

NP is a better predictor of FTP, that's why it was invented (I think). IOW, if your 3 1/2 hr ride was a time trial you could have held at least a 270 W average.

Piotr said:

NP is a better predictor of FTP, that's why it was invented (I think). IOW, if your 3 1/2 hr ride was a time trial you could have held at least a 270 W average.

I'd phrase that a bit differently. NP is a good estimate of overall stress on your metabolism or metabolic load. If you ride steady efforts at constant power NP and AP will be very close if not equal to one another. They tend to be pretty close to one another for steadily ramped efforts as well.

But when you ride things like crits or group rides or a lot of short intervals interspersed with rest AP and NP will be quite different. AP in a crit for instance usually isn't all that high with all the coasting in corners but the overall metabolic stress is still substantial with the jumps and accelerations out of those corners. NP does a better job of estimating how hard you worked during those dynamic efforts.

So you can think of NP as the effective AP you would have held if you could have put out steady power during a ride where you have a lot of bursts and rests. Sure, that can be used to estimate FTP during very dynamic rides (assuming they're roughly an hour in length and the overall effort was near your max for the duration). But I wouldn't limit the value of NP to FTP estimation, it's a way to get an effective average or estimate overall effective intensity of a dynamic ride and is used to calculate IF, TSS and from that CTL and ATL.

All in all it's a pretty useful metric for real world rides that aren't ridden isopower, if you do ride isopower efforts in training or time trials then you won't see much difference between AP and NP but ride a crit and you should see quite a bit of difference.

-Dave

jsirabella said:

When you download a workout from your PM into WKO+ you will get your numbers for entire workout, peak 60 minute, 30 minute, 20 minute and within those number for each grouping you have Average Power and Normalized Power. Normalized Power is defiined and calculated here:

cyclingpeakssoftware.comdefined.aspOpen ↗

Normalized Power is what your power would be if you "in essence, it is an estimate of the power that you could have maintained for the same physiological "cost" if your power output had been perfectly constant (e.g., as on a stationary cycle ergometer), rather than variable."

Do most people use the Normalized Power Number or Average Power Number when calculating their FTP. In many cases for me here, I usually have a substantial difference between the two numbers. I.e for yesterday 3 1/2 hour ride I had a peak 60 minute of 220 AP but a 270NP....so which number counts? How do you folks look at it.

For me personally six months ago my AP and NP were much further apart. It seems now my AP has shot up but my NP just not as much. In the example above my AP and NP for only a 2 1/2 hour ride was 180AP and 250NP. I believe for me that is saying I am able to give a steadier more countrolled output compared with six months ago.

Just as an FYI, last week I verified my FTP of 260. I dialed in 260 on the CT using the bike with my PM and both had AP for one hour of 260 and NP of 260.

On the CT there is no (or should be little to no difference) between your AP and NP if you dial in one number for one hour. I have a feeling I know what swampy and Tyson would say, I wonder how the rest look at it.

I hope it cleared it up...

-js

I think so 🙂

The difference you are noticing in the ratio between NP and AP is simply a reflection of either the type of rides you are doing, and/or the way you are riding those rides. It is quite easy to increase the NP:AP ratio simply by attacking rises and recovering down the other side. Conversely it is easy to make the ratio approach 1 by riding relatively smoothly.

Sometimes if you feel good, you are more likely to attack the rises a bit more. If you are fatigued, the tendency is to moderate the power output somewhat, even though the average overall might be similar. Perhaps you are carrying a lot of fatigue and you are tending to ride at a smoother power level than before?

I'd suggest that most people (should) formally test for FTP, and use data from rides/races (other than TT type efforts) as indicators only as to whether FTP may have changed and whether further testing is warranted.

I wrote about testing for FTP here:
alex-cycle.blogspot.comseven deadly sins.htmlOpen ↗