FTP vs Normalized Power

power-meter

#1

Hi all,

I have recently acquired a stages (left side only) power meter and have noticed the following:

  1. My normalized power on a 3.5 hour ride is at least 12% higher than my tested FTP.
  2. I have recently spent more time riding outdoors (during our lovely South African summer) than indoors on the trainer. So about 6 weeks after my previous test, I tested at EXACTLY the same FTP this morning. I tested using the 2x8 min FTP test.

So my questions are:

  1. Should I adjust my FTP based on outdoor NP? Or rather stick to the tested FTP? From perceived effort, I am not sure that I will be able to sustain that NP on an indoor trainer.
  2. Why the major difference? Overheating?

Look forward to some valuable input.


#2

What type of trainer are you using? Can you use powermatch now you have the power meter?

Have you calibrated the Stages properly?


#3

outdoor and indoor FTP’s are normally different: sometime very different, 10-15% (mine is 12% less)


#4

But 12% higher than your FTP on a 3.5 hour ride can’t be fully explained by that difference. Unless the turbo is in a REALLY hot room.


#5

In the past when I use to ride hard crits, the NP for a one hour race was very close to my FTP. In fact, I could use it as an FTP estimate. There must be something wrong with your tested FTP.


#6

Are you even using the same power meter indoors and outdoors? My Stages underreported by 6,5% vs. my Tacx Neo and I attribute that to leg discrepancy, had surgery on my left leg. In any case you need to be using the same PM or atleast have your power meters calibrated equally.


#7

I’m sorry, there was a misunderstanding and, perhaps, I have not explained well: my FTP indoor is 12% lower than the outdoor one, and, in my experience, I think it’s normal


#8

Thanks for all the feedback.

I am running a Cycleops PowerBeam Pro on the legacy app off mac, with the stages on the same bike. Operating the software with power meter set to control the trainer in ERG mode. Spindown and Stages zero/calibration before each ride. Room temp sat at 23degrC this morning which should be about the average indoors.

I have in the past 2 weeks been consistently higher on NP outside. Granted I have only done about 10-12 hrs with the Stages, with only a single sustained power type ride being 7% higher than FTP for a 1h20 ride. Longer rides 3h50, 2h and even a 3h54 being close to 12% higher NP outdoors than indoor tested FTP.

I would understand an occasional variance due to group pace etc, but this feels weird. I would understand the opposite, with FTP being higher than what I am able to produce on a 3-4hr ride.

Something to ponder…


#9

Now that seems consistent to what I am seeing…although 1hr NP seems similar for me on 3-4hrs. Maybe I just suck at 1hr rides and need to step up. :grin:


#10

let me also say that NP is not FTP because FTP has a continuous detection in a period of time while NP is, in fact, normalized


#11

On a 3.5 hour ride, I would think your NP should be close to your avg Power for the ride, which would be in the range of 60 to 70% of your FTP. If you weren’t over say 95% of your max HR during your FTP test, you weren’t working hard enough. Something is either wrong with your equipment or your FTP test protocol.


#12

23 is quite hot for indoors.

But still, I agree with @apond58 - something isn’t quite right with the equipment. Can you post your ramp test and one of your rides?


#13

From what I have experienced, NP will be much different compared to AP if your ride contains numerous sprints or hard efforts. NP is not effected by back pedaling or coasting like AP

On a steady effort ride, NP and AP will be similar.

:slight_smile:


#14

Look up the formula for ‘normalized power’. The idea behind it may be good, but it is very simple formula and originated when the power of bike computers was very limited. Also, it assumes you are the same as everyone else. If you think it is nonsense then just ignore it. I would not adjust your real FTP based on the silly maths of NP.


#15

Can you link the test and the ride you are referencing?

Something sounds off with your equipment setup.


#16

Sure thing…let me give it a try.

2 x 8min FTP @ 233W Calculated FTP

3h50 ride @ 250W NP (SLOW AND WET CONDITIONS)

2h05 ride @ 258 NP


#17

Your profile needs to be public for us to view them.


#18

I’m a twitchy" guy and big so even small changes in grade result in big spikes in power. My NP on multi-hour rides is pretty regularly well above the average power I’d have a prayer of holding for an hour or more. I had a ride of 3:40 that had an NP equal to my then FTP. Obviously, there’s no way I could hold my actual FTP for almost four hours. NP rewards higher wattage efforts. Not all power curves are equal in the sense that 120% or 200% for me might not have the same effect on my lungs/legs as it would someone else. Repeat-ability of VO2 max efforts differs. People are not robots, FTP tests are at best an estimate. I wouldn’t read too much into your numbers so long as the workouts that are derived from them are hard but not too hard. Nobody won a race based solely on their FTP results.


#19

That makes sense…probably pushing my 110kg up a hill also requires those big spikes and would explain why I run out of steam on the longer sustained efforts. Traditionally I have tended to more “fast twitch” sports, rugby, weighlifting etc. So it think the NP “formula” may be the thing causing the offset between the figures.

Guess I will trust the process. Test for FTP and try to manage it outdoors.

Thanks all.


#20

Sorry…made public.