Sweet Spot Progression

Did my 1x90 today. Man it was a fight for the last 20min. HR was high, but I got through it to close out the block. Probably do more 3x30s, 5x20s in the upcoming intensive block, but don’t wanna touch that 1x90 again any time soon. :laughing:


How do I calculate tss for a workout?
The workouts in the SST Team here are all at 90%, so I can only see the tss for 90% intensity.
I have now completed 2x30 at 90% which felt really hard, HR was at 90% of max HR in the end.

Not sure where I should go from here. Also not sure whether I should continue with base II or Build I after the progression? I’d like to continue with the TR plan once I’ve hit 1x60.

Before the workout? Afterwards, it will just show…

TSS is IF**2 * time, IF is NP/FTP. For long steady intervals like sweetspot, you can substitute average power for NP for an estimate.

TSS = [(s x NP x IF) / (FTP x 3,600)] x 100

s - is the time in seconds
NP - Normalised Power

Pretty sure its IF squared?

Well I tried it to see if it simplifies to that and didn’t get the correct answer, I use the formula I posted and it equals the values in TrainingPeaks & WKO


Ah wait, I read your equation again, and it has IF x NP/FTP … which is of course IF squared.

It is somewhere on the TP website, but it is very hard to find, I do have a bookmark for it somewhere…

Download the TR workout creator, and play around with making workouts. It’s very easy. The workout creator calculates the TSS and IF for each workout you create.

Simplified from the above equation…

TSS = IF^2 * T * 100


  • IF is intensity factor
  • T is time in hours (e.g. 1:15:00 / 75 minutes is 1.25 hours)


TSS = .63*.63 * 1.25 * 100
TSS = 49.6125
TSS ~ 50

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Which is what I put first…well I forgot about the 100, but thats just the decimal point. :smile:

How do you calculate IF if you don’t have it provided already?

Normalised power (NP) divided by FTP.

For long steady intervals, especially indoors, NP is going to be similar to average power.

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Ahh, duh! Should have read your prior comment again. Thanks!

Yes, so if you go out and do steady aerobic endurance at 71% FTP (IF = .71) then it’s roughly 50 TSS per hour.

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Thanks, guys :wink:

Not started here yet. mFtp set to 272. Failed an FTP test last week. Blew up :-(.
Today averaged 240w NP for 3hours in Zwift Fondo. That is 88%? Guess mFTP should ben higher…

Average power in a stochastic ride and sustaining a steady effort don’t work out the same. Try it and see how it goes. Odds are you could do it.

Ok. Started with 1x40min 250w. Damn zwift erg mode only averaged me on 245w.
Should I use erg mode or not? Not really a ERG mode fan because it feels much harder. But for steady state you need a solid effort at same power as much as possible. Any tips?

turn off erg and ride it like you would outside?

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I do all my rides in level mode and if you find proper gearing to your cadence and level there is absolutely no problem with holding steady power for any amout of time.