I think that there is something wrong with the way zFTP is calculated. Just take a look at the following three data sets.
1
2
3
5 sec
841
929
929
15 sec
728
792
792
30 sec
595
595
595
1 min
481
554
554
3 min
347
394
394
5 min
332
387
387
10 min
330
330
351
12 min
329
329
329
15 min
329
329
329
20 min
329
329
329
30 min
280
280
280
40 min
250
250
250
zFTP
307
313
305
zMAP
330
384
384
VO2
51,6
60,1
60,1
So, to sum it up. From session 1 to session 2 I increased my 5 sec power, 1 min power, 3 min powedr and 5 min power. This (purely anerobic and vo2max) increased my zFTP from 307 to 313.
Then from session 2 to session 3 I further increased my 10-minute power, which resultat in my zFTP DROPPING from 313 to 305. So, being a better rider at 10 minutes not only decreased my zFTP, it decreased it to a number lower than I initially had before I the first couple of increases.
So my take from this is: being a better sprinter and having a better vo2max makes you better at riding for 1 hour (zFTP), however being better at riding 10 minutes SIGNIFICANTLY makes you worse at riding for 1 hour (zFTP). This does not make any sense.
When I am freash I will raise my 40 min power, from 250 watts to probably over 300 watts. It will be interesting to see what happends to my zFTP then. It will probably decrease, since being better at riding for longer periods makes you worse at riding for longer periods, obviosly, but it will be interesting to see by how much my zFTP will decrease. If I raise my 40-min power to 300, will my zFTP drop below 300? If I ride at over 300 for 60 minutes will my zFTP drop below 275? Since the longer the period the more negative correlation to zFTP one has to wonder.
As for the zMAP, isnt it true that if rider A has 3-min power at 400 and 5-min power at 380 while rider B has both 3-min and 5-min power at 380 then rider B will have a higher zMAP even tho he should have a worse number? It seems like the zMAP is a linear trend fron the ln-values of 3, 5 and 6.2.
There are still CE races out there, just not very many. My guess is it will not be developed further since the focus is on ZRS now, and we get more value out of fixing ZRS than CE.
Yeah, the data sets are off
The VO2 max calculation is really different.
Since most formulas use the 5 min power for this, there must be a big difference in 5 min power, and that is the case.
Not all these times represent the “best” time for the specific interval.
I am so new to Zwift (less than 3 weeks) that I have not yet given it a go at all time-frames. I only do workouts or solo time trials while free-riding. I gave everything I had for 10 minutes and then saved.
Thanks for your answers but what I would need is help solving the algorithm of how the zFTP is calculated, as it is obvious that by becoming better at one time-frame (all else being equal) can lower my zFTP, which is utterly ridicilous. So I need to figure out the algorithm to play it to my advantage.
Today I will to a 100 minute session at 220 watts to see if raising the fart right end of the power curve does anything for the zFTP. Then on friday I will do either an all out 40 or 60 minute effort, depending on what result I get from todays session.
My current goal is to get into the A category within 4 weeks of starting cycling. For this I need to know what time-frames to go for and which ones I should keep as low as possible.
that is ambitious, have you never cycled before? Looks like you are a runner based on your little picture. What trainer are you using for Zwift (please don’t say its an unsupported spin bike)
zFTP is Critical Power.
It only looks at intervals 5 minutes and above, and I don’t think it looks at anything longer than 20 minutes.
It doesn’t look at fixed intervals, seems to find local peaks on the curve to use for the calculation.
Typically a flatter power curve will tend to calculate a higher zFTP, but there seems to be a limit to that as you showed from your very flat session 1 giving a lower result than session 2.
“that is ambitious, have you never cycled before? Looks like you are a runner based on your little picture. What trainer are you using for Zwift (please don’t say its an unsupported spin bike)”
No I have never cycled before if you dont count airbike, which I used last time I got injured from running which was almost a year ago. I did a test-run today and will probably be back in a week or two, but who knows how much running fitness I have lost, being out for 6 weeks, doing 10-15 hours per week of cross training.
By the way, I find it hard to believe that my vo2max, as measured on a bike, is 60.1. For running it is around 65, and I really dont believe yet that I am that close for cycling, as my HR at the 5-min max session was between my 10k and my half-marathon pace (closer to HM pace). So its still always the legs that give up before the breathing then I ride.
I have the Zwiftbike deal, with a Zwift frame and a Wahoo kicker.
Yes either one will result an upgrade. At least for me, doing a big 5-6 min PR is easier since you can do it when you are fresh on an appropriate climb, no race required.
But if it is Critical power (how long I can go for 30-40 minutes) rather than FTP (how long I can go for 45-60 minutes), then how can my FTP (20 min power * 0,95 = 313, although Zwift set my FTP to 314 so maybe it uses another formula) be higher than my critical power?
It seems strange that Zwift calculates that I can go harder for 45-60 minutes that I can for 30-40 minutes?
Also, why doesnt CP use 30-40 minutes power? I mean, if I can produce a certain wattage for that time, then it IS my CP, no calculations needed. I mean even if Zwift wants to put me at a very low number just because my 10-min power is relatively high, isnt a 30-40 min intervall proof that I can actually produce that wattage, or is this to straight forward for Zwift?
Oh, either one will result in an upgrade? Then I will surely go for the 5-minute session. I will create a workout and put a 5-min block of 410 watts, down a tripple dose of pre workout and just try to hold on for dear life.
