Discrepancy Zwift FTP result vs Strava average Power *0.95


(Vincent Molenveld) #1

Yesterday I did a FTP test Short with a FTP result of 292.

I uploaded it into Strava and the average power for the 20min section is 325W, this results in an FTP of 308 (325*0.95).

Someone an explanation for this?

 

 


(R Idge Cyclesport) #2

I noticed this as well, the FTP “Average” power it shows while cycling is very low.

Not sure where the average power is coming from.

Strava = 332 average for the 20 minute section, Zwift showed 306 average.

This was on the FTP long test.

Believe it or not, this is stuff I do want to see fixed before I start paying for it (and the ability to create my own workouts).

Right now, Zwift offers less than Tour De Giro, so asking the same price is a no go for me. Yes, Zwift looks better, but TDG still offers customized workout plans, uploading of your own GPX files, and private rides.


(Daren Chandisingh [Vision]) #3

I’ve wondered about this myself and talked about it in another thread. But I think the Strava power curve “best 20 minutes” actually aggregates your best 20 minutes across a whole ride, even if they’re not contiguous.

So say you do 10 mins at 250w, then 5 mins at 200w, then another 10 mins at 250w, it would still say “250w for 20 mins”, and “200w for 25 mins”.

I’m not certain of that, but it would help explain the deiscrepancies between Strava and Zwift. Or I might be completely wrong… :smiley:


(Vincent Molenveld) #4

No, I have selected the period in the Strava Analyse screen from minute 20 till minute 40.


(R Idge Cyclesport) #5

What Vincent said,

Selecting the 20 minute section, and grabbing the average from that.

I’ve tried to look at where it’s getting the number, besides an odd % that doesn’t seem to be the same for either of us.

His calculates to just under X*.90 mine calculates to just over X*.92

 

They are both 20 minute tests, so the should use the same formula regardless.


(Jude Hung) #6

Hi Mic and Vincent, 

I had exactly the same issue with my FTP long test few days ago!  Zwift displayed a quite low average power during my 20 mins test segment, and then estimated my FTP to be 205w while I actually did 242w on average over the the 20 mins test segment.

I’ve reported such discrepancy in another thread, and also filed a support ticket for investigation.

 


(Anton Samrai) #7

Same here (using computrainer):

Zwift showed 291W average for 20 min

Trainingpeaks download shows 298W average for same 20 min segment

I was pretty excited that I hit good numbers, but now I’m not quite sure if either of these is accurate … 


(Kelly Lynam) #8

Same here. Strava = 214 average, so 203 FTP using *.95 math. Zwift = 197. I was really hoping to break 200 so…


(Chris Maughan) #9

Note: FTP Short test uses 95% of your 20 minute power, according to the Knowledge base.