Quick question about Normalised Power and F. threshold power

neeb

Am I right in thinking that if I have an NP value for an all-out effort of just over 1 hour on a slightly rolling course, my functional threshhold power is very unlikely to be less than that? (even if the average power was 25w less?).

For what it's worth, my average HR was also about what I think my threshold HR is based on indoor trainer efforts in the past.

Alex_Simmons/RST

neeb wrote:

Am I right in thinking that if I have an NP value for an all-out effort of just over 1 hour on a slightly rolling course, my functional threshhold power is very unlikely to be less than that? (even if the average power was 25w less?).

No.

FTP <= an all out 1-hour NP

However, your FTP will be closer to your NP, than your AP.

neeb

Alex_Simmons/RST wrote:

No.

FTP <= an all out 1-hour NP

However, your FTP will be closer to your NP, than your AP.

Ok, thanks. Is that approximately quantifiable, e.g. assuming a 25w difference between AP and NP, and assuming for sake of argument that the effort really was 100%, is FTP likely to be about NP minus 5w, NP minus 8w or whatever?

amaferanga

I'd say your FTP is probably quite close to the NP. But does it matter if it's 5W less or 8W less or even a few Watts more? How does the effort compare to the sort of numbers you can regularly put out for an hour or so?

neeb

amaferanga wrote:

I'd say your FTP is probably quite close to the NP. But does it matter if it's 5W less or 8W less or even a few Watts more? How does the effort compare to the sort of numbers you can regularly put out for an hour or so?

I guess it doesn't matter that much, it's just that because I'm new to training with power I want to get the parameters set as accurately as possible for working out power zones etc. But in any case I suppose FTP is going to vary by about that much fairly regularly just due to fitness variation.

Difficult to say how it compares to regular hour figures as I haven't been out for that many short fast rides since I got the PM, but for my best effort of just over 2 hours the figures were 87% and 92% of the one hour AP and NP figures.

I'll be able to get a better estimate when I drag the Tacx fortius out of storage for the winter and hook up the powertap to it for a one hour simulated climb (and I'll also find out exactly how much the fortius was overestimating my power... )

danowat

Humour me here..........

If you were doing an all out hour, why would the NP be 25w different to the AP, surely an all out hour would have a closer relationship between NP & AP?

neeb

danowat wrote:

Humour me here..........

If you were doing an all out hour, why would the NP be 25w different to the AP, surely an all out hour would have a closer relationship between NP & AP?

I assume it's because it's a moderately rolling course, lots of short ramps that I power up way above FTP and then I'm way below FTP briefly afterwards, plus corners etc. Also there are a couple of stops at junctions. I imagine that the two would be much closer on a flat course, but I don't claim to fully understand (yet) how NP is calculated. The AP is including zero readings (about 10% of the total time) but not actual stops.

So do you find that your AP & NP figures are much closer? On what sort of course?

danowat

neeb wrote:

danowat wrote:

Humour me here..........

If you were doing an all out hour, why would the NP be 25w different to the AP, surely an all out hour would have a closer relationship between NP & AP?

I assume it's because it's a moderately rolling course, lots of short ramps that I power up way above FTP and then I'm way below FTP briefly afterwards, plus corners etc.

This is my point, surely that's not the best way to derive your FTP?

neeb

danowat wrote:

This is my point, surely that's not the best way to derive your FTP?

You could be right..

Difficult to find a flat course where I am though, it's all heavily glaciated granite, no hills to speak of but nothing flat either...

Here's the power distribution, assuming that my FTP is 5w below the NP for that ride - not much time at actual threshold power! As I say, when I get the indoor trainer set up it'll be a lot easier.

amaferanga

neeb wrote:

danowat wrote:

Humour me here..........

If you were doing an all out hour, why would the NP be 25w different to the AP, surely an all out hour would have a closer relationship between NP & AP?

I assume it's because it's a moderately rolling course, lots of short ramps that I power up way above FTP and then I'm way below FTP briefly afterwards, plus corners etc. Also there are a couple of stops at junctions. I imagine that the two would be much closer on a flat course, but I don't claim to fully understand (yet) how NP is calculated. The AP is including zero readings (about 10% of the total time) but not actual stops.

So do you find that your AP & NP figures are much closer? On what sort of course?

Why have you excluded stops?

danowat

neeb wrote:

danowat wrote:

This is my point, surely that's not the best way to derive your FTP?

You could be right..

Difficult to find a flat course where I am though, it's all heavily glaciated granite, no hills to speak of but nothing flat either...

Here's the power distribution, assuming that my FTP is 5w below the NP for that ride - not much time at actual threshold power! As I say, when I get the indoor trainer set up it'll be a lot easier.

Any hour all out with 26mins at Endurance and 13mins at recovery? :?

neeb

amaferanga wrote:

Why have you excluded stops?

This is just the Garmin autostart/stop feature for when stopped at junctions etc. (not very many of those). Would it make more sense to include them? That would obviously bring down AP, how would it affect NP?

danowat wrote:

Any hour all out with 26mins at Endurance and 13mins at recovery? :?

And 20mins at "supramax"... I don't know, but I can't see how I could be significantly more "all out" on that particular course. If I tried to keep the power profile flatter but the time was slower, would that be more "all out"?

P.S. It's actually a bit more than an hour, 1 hour 11 I think.

danowat

neeb wrote:

And 20mins at "supramax"... I don't know, but I can't see how I could be significantly more "all out" on that particular course. If I tried to keep the power profile flatter but the time was slower, would that be more "all out"?

I just think (and correct me if I am wrong), that having such a spread of power (which was clear by the difference between NP & AP), isn't the best way to determine your FTP, either do it on a turbo / flat(ter) road, of work on your pacing.

neeb

Ok, you are probably right. I guess it depends how well NP works as an estimate of FTP when the power spread is extreme, I know that's what it's supposed to do, but the calculation must become less accurate as it is pushed more to the extreme.

It'll be interesting to compare the FTP estimate when I do a constant effort on a turbo.

jibberjim

neeb wrote:

amaferanga wrote:

Why have you excluded stops?

This is just the Garmin autostart/stop feature for when stopped at junctions etc. (not very many of those). Would it make more sense to include them? That would obviously bring down AP, how would it affect NP?

Do not use Auto-Pause. Just don't.

Alex_Simmons/RST

danowat wrote:

neeb wrote:

And 20mins at "supramax"... I don't know, but I can't see how I could be significantly more "all out" on that particular course. If I tried to keep the power profile flatter but the time was slower, would that be more "all out"?

I just think (and correct me if I am wrong), that having such a spread of power (which was clear by the difference between NP & AP), isn't the best way to determine your FTP, either do it on a turbo / flat(ter) road, of work on your pacing.

It's not, but that wasn't the question.

Inspecting NP from an all out effort is best thought of as a means to assess whether or not it's likely your current FTP estimate needs validating. e.g. if you think your FTP is 250W, and you do an hour ride (and NP is correctly calculated*) with an NP of 270W, then it's a pretty strong indicator that your FTP is higher than you think it is. How much higher is then something to be determined through consideration of one or more sins:
http://alex-cycle.blogspot.com/2008/05/ ... -sins.html
http://alex-cycle.blogspot.com/2009/07/ ... ftp-2.html


As for "all out" - that's just a function of how hard you feel you rode a particular course/race/session. For example, an all out training session might comprise maximal efforts interspersed with recovery periods.


* keep in mind that in order for NP to be correctly calculated, that the power meter needs to be accurate, and the calculation follow the correct algorithm. Things like smart recording and auto pause on a garmin typically screw with the calculations.

Alex_Simmons/RST

neeb wrote:

Alex_Simmons/RST wrote:

No.

FTP <= an all out 1-hour NP

However, your FTP will be closer to your NP, than your AP.

Ok, thanks. Is that approximately quantifiable, e.g. assuming a 25w difference between AP and NP, and assuming for sake of argument that the effort really was 100%, is FTP likely to be about NP minus 5w, NP minus 8w or whatever?

From an all out effort, FTP will be within 5% of NP.

There are rare circumstances when that may not be the case.

In many 10's of thousands of power meter files, I've seen maybe one or two legitimate "NP busters".

danowat

Alex_Simmons/RST wrote:

It's not, but that wasn't the question.

It wasn't, but it has highlighted an issue none the less.

Alex_Simmons/RST

neeb wrote:

Ok, you are probably right. I guess it depends how well NP works as an estimate of FTP when the power spread is extreme, I know that's what it's supposed to do, but the calculation must become less accurate as it is pushed more to the extreme.

Well NP from a hard hour has never been claimed to be any better than be within ~ 5% of FTP.

But keep in mind that as the variability* of an effort reduces, NP approaches AP anyway (it's a function of the algorithm).


* when that variability covers periods of ~30 seconds or more.

danowat

Thinking outside box here...........

Could the function of NP be used to give some feedback on pacing during (or after) a TT?, i.e. the closeness of NP to AP during such an event?

Alex_Simmons/RST

danowat wrote:

Thinking outside box here...........

Could the function of NP be used to give some feedback on pacing during (or after) a TT?, i.e. the closeness of NP to AP during such an event?

NP is an excellent tool to aid post hoc assessment of pacing, or to pre-plan an optimal pacing strategy*. NP enables us to develop an optimisation algorithm to combine knowledge of our physiological limits with the equations of motion for a cyclist. When you combine those with Virtual Elevation modelling, then some very cool things emerge.

The ratio of NP to AP in and of itself might be a little misleading**, but for most well paced events on courses that don't have a lot of gradient variability, then the ratio should be close to 1. (so if doing a relatively flat TT, and you see a ratio of NP to AP of 1.06, then it's almost certain your pacing was poor).

For courses that are quite variable in gradient, then it's likely optimal pacing will result in higher ratios.

A few years ago I wrote a discussion paper on this very topic, and build a model to rate and assess pacing strategies. I've run pacing assessment on TT power meter files from riders such as David Millar, Marco Pinotti through to local amateurs/club riders.


* Indeed if you are planning a training session, then calculating the NP is a very good way to determine whether or not the planned workout is physiological feasible.

** The reason that the ratio itself might be a misleading indicator of pacing, is that there are many ways one can achieve such a ratio, some might be optimal, others less so.

danowat

Alex_Simmons/RST wrote:

danowat wrote:

Thinking outside box here...........

Could the function of NP be used to give some feedback on pacing during (or after) a TT?, i.e. the closeness of NP to AP during such an event?

NP is an excellent tool to aid post hoc assessment of pacing, or to pre-plan an optimal pacing strategy*. NP enables us to develop an optimisation algorithm to combine knowledge of our physiological limits with the equations of motion for a cyclist. When you combine those with Virtual Elevation modelling, then some very cool things emerge.

The ratio of NP to AP in and of itself might be a little misleading**, but for most well paced events on courses that don't have a lot of gradient variability, then the ratio should be close to 1. (so if doing a relatively flat TT, and you see a ratio of NP to AP of 1.06, then it's almost certain your pacing was poor).

For courses that are quite variable in gradient, then it's likely optimal pacing will result in higher ratios.

A few years ago I wrote a discussion paper on this very topic, and build a model to rate and assess pacing strategies. I've run pacing assessment on TT power meter files from riders such as David Millar, Marco Pinotti through to local amateurs/club riders.


* Indeed if you are planning a training session, then calculating the NP is a very good way to determine whether or not the planned workout is physiological feasible.

** The reason that the ratio itself might be a misleading indicator of pacing, is that there are many ways one can achieve such a ratio, some might be optimal, others less so.

Thanks Alex, very helpful, is the said discussion paper available to read anywhere?

Alex_Simmons/RST

danowat wrote:

Thanks Alex, very helpful, is the said discussion paper available to read anywhere?

There are a couple of people that have it hosted on their servers but I forget where.

PM me your email address and I can send you a copy.

neeb

All very interesting, thanks!

Just for the record, the power variability over the ride above was pretty constant throughout the 1h 11m, so I don't think the difference between AP and NP was down to bad pacing in the sense of power dropping off substantially towards the end of the ride, although it's quite possible that my pacing was suboptimal in the sense of variation from one 20sec segment (or whatever) to another.

So I should definitely turn off the autopause on the Garmin then? Doesn't that lead to unrealistic under estimates of effort in terms of average power if it is including 30sec stops at traffic lights? Will NP accurately reflect effort nonetheless however, i.e. will there simply be an even bigger gap between AP and NP, or will NP come down as well if I have a couple of stops?

Alex_Simmons/RST

neeb wrote:

So I should definitely turn off the autopause on the Garmin then? Doesn't that lead to unrealistic under estimates of effort in terms of average power if it is including 30sec stops at traffic lights?

No. Consider that the power you can produce when riding is affected by the time spent not pedalling. But again a bit will depend on how you (or your software) are calculating AP.

neeb wrote:

Will NP accurately reflect effort nonetheless however, i.e. will there simply be an even bigger gap between AP and NP, or will NP come down as well if I have a couple of stops?

I don't know how you are calculating NP, so NFI.

neeb

Alex_Simmons/RST wrote:

neeb wrote:

Will NP accurately reflect effort nonetheless however, i.e. will there simply be an even bigger gap between AP and NP, or will NP come down as well if I have a couple of stops?

I don't know how you are calculating NP, so NFI.

Just using the NP figure that Garmin and/or PowerAgent calculates, they're always the same (I don't know if that's because PowerAgent takes the NP figure from the Garmin or if it recalculates it using the same algorithm).

Alex_Simmons/RST

neeb wrote:

Alex_Simmons/RST wrote:

neeb wrote:

Will NP accurately reflect effort nonetheless however, i.e. will there simply be an even bigger gap between AP and NP, or will NP come down as well if I have a couple of stops?

I don't know how you are calculating NP, so NFI.

Just using the NP figure that Garmin and/or PowerAgent calculates, they're always the same (I don't know if that's because PowerAgent takes the NP figure from the Garmin or if it recalculates it using the same algorithm).

Well what matters is whether it uses the correct algorithm (they may be both correct or both incorrect). There have been instances when that's not the case, but I don't know in this case.

SBezza

For the OP, if you want a VI of close to 1 (and this should be very possibly even on a hilly course), just find a local 25 mile TT course and use that for the all out effort (assuming it is not a busy dual carriageway). I personally wouldn't take the figure you have got from such a variable effort as a true 60 min effort. Others might feel differently but like Danowat said with such a large amount of time spent at recovery and endurance effort, it is obviously affecting the AP/NP ratio a fair bit.

I personally have always used AP for FTP determination, but then again my AP/NP relationship is always pretty close to 1, and is done on the turbo or a TT course with minimal time spent negotiating stops/turns etc.

neeb

Thanks, I might try that (it's kms where I am so I'd need to find a 40). But the indoor trainer will probably be the easiest option, just need to dig it out...

Alex_Simmons/RST

neeb wrote:

Thanks, I might try that (it's kms where I am so I'd need to find a 40). But the indoor trainer will probably be the easiest option, just need to dig it out...

Of course the trainer can throw up other issues, as it's not uncommon for people to be unable to produce the same power on a trainer as they can outdoors.

If long sections of road are tricky to find, the something that gives you 20-minutes will be enough for reasonable testing, as you can add an all out 5-min test as well and use the Critical Power Model to estimate FTP.

springtide9

Sorry to dig up this thread... but have a question on Intensity Factor (IF) and a statement I read on Training Peaks about if it goes above 1.05 for a 1hr+ race, then there is a chance your Threshold Power has changed.

The question is whether this statement holds true for other types rides, specifically where intervals are involved. For the second time in two weeks my IF has been above 1.1 - but as the sessions have been very much interval based, average power hasn't been that high. I have read about NP Busters and wonder whether this is the cause - although I'm not really sure what value of IF is considered a buster. Figures are coming from both Training Peaks as well as Garmin, although the Garmin value is a little higher (so TP is obviously calculating it)

I guess the reason for asking is that I don't think my Threshold has changed. It has previously dropped since I last did a 20min test and have been working on getting my fitness back - hence why I don't think it's changed.

Now the obvious thing to do would be to retest; but it's a struggle trying to find a bit of road without any stops for 20 mins without venturing far from home, which isn't currently possible due to current family commitments.

While I am asking questions, within Training Peaks, the Performance Management Chart... what values should be set for, CTRL Constant, CTL Start, ATL Constant & ATL Start?
And also, how low should TSB be allowed to go? It's just that even after two complete days rest, it's still -18 (I guess I'm not sure if this is normal or not)

Maybe showing the graph will help:
http://flickr.com/gp/peppernet/xt10s6

Sorry for all the questions.. :oops: