Power, determining ftp

ozzzyosborn206

Hi all I have an srm and having been using my 20min power minus 5% to work out my ftp, it seems to work as the power i can do for a 10 mile pb is pretty much 5% more than a 25, today i did a 30 min crit and my 20min average for this was 15 watts more than my previous 20 min best, should i readjust my ftp for keep it at what it was from steady 20 min efforts as opposed the the on/off nature of a crit? fyi my best 20min steady power is 298 and in crit today best 20min was 315, i'm 65kg

borisface

It's not uncommon for people to have different ftp's on turbo and road and so it would seem logical for someone to have a higher ftp in a bunched race compared to a solo effort. There are many excellent roadies who don't do so well against the clock and you may be able to pull out more so to speak when in a bunch compared to on your own. You wouldn't be alone in that I'm sure.

When doing your solo efforts does the average drop off in the last 5 mins or are you fairly even throughout? This could be an indication that you are starting too fast or too slow.

What is your NP? Is this massively different from the results of the 20 minute sample?

But ultimately, if you are able to complete efforts based on your new ftp then go for it, otherwise stick with what you've been using.

colinsmith123

What was your FTP in the crit over 1 hour? If this too was more than your previous FTP, then use this, especially if your NP is well above 1.05.

Well done.

Tom Dean

If your best 20 minute average in the crit was higher than your test, it's time to re-test.

If you are talking about NP: NP over around an hour in e.g. a crit is widely used as a check on FTP, but the principle doesn't really apply over shorter durations. I would say a difference of 15w is within what you would expect but don't draw any conclusions from it.

Alex_Simmons/RST

Make sure the data is correct. There may be reasons thr crit power number is artificially inflated. Where did you get the number from?

Stalin

Alex_Simmons/RST wrote:

Make sure the data is correct. There may be reasons thr crit power number is artificially inflated. Where did you get the number from?

When you say artificially inflated do you mean the power meter over estimating power, or the software/ head unit overestimating due to say freewheeling, or some other possibility?

Many people put out much more power on the road than on a turbo. Also many put out more power in a race than a test.

Are there other reasons why a crit power might be artificially inflated?

Alex_Simmons/RST

Stalin wrote:

Alex_Simmons/RST wrote:

Make sure the data is correct. There may be reasons thr crit power number is artificially inflated. Where did you get the number from?

When you say artificially inflated do you mean the power meter over estimating power, or the software/ head unit overestimating due to say freewheeling, or some other possibility?

Many people put out much more power on the road than on a turbo. Also many put out more power in a race than a test.

Are there other reasons why a crit power might be artificially inflated?

There can be various reasons including user error. I'm not saying this is the case or a common thing, just eliminating possibilities. Knowing what was used can help narrow down/eliminate.

Stalin

Alex_Simmons/RST wrote:

Stalin wrote:

Alex_Simmons/RST wrote:

Make sure the data is correct. There may be reasons thr crit power number is artificially inflated. Where did you get the number from?

When you say artificially inflated do you mean the power meter over estimating power, or the software/ head unit overestimating due to say freewheeling, or some other possibility?

Many people put out much more power on the road than on a turbo. Also many put out more power in a race than a test.

Are there other reasons why a crit power might be artificially inflated?

There can be various reasons including user error. I'm not saying this is the case or a common thing, just eliminating possibilities. Knowing what was used can help narrow down/eliminate.

User error?

Alex_Simmons/RST

Stalin wrote:

User error?

Yes, just like any device, e.g. if a user sets their watch wrong, it'll tell them the wrong time or date. Ever known anyone to get the am/pm setting wrong on a clock and the alarm not to go off when it was expected to?

All power meters and/or head units have a certain level of user input to ensure quality of data. It's not a lot of input, but there's no harm in doing some validation and verification.

indjke

Alex_Simmons/RST wrote:

There may be reasons thr crit power number is artificially inflated.

Average not including zeros for example?
Anyway nice power..