Hi there,
I have 2 questions:
- Can somebody explain the non-linear relationship between the estimated TSS and the duration?
- Why you get 100 TSS for 1h for the highest (all out) intensity, when we all know that 100TSS equals 1h @ FTP?
Thanks,
Probably because they are assuming you won’t be doing IF1 time trialing for durations longer than an hour so your VI has to increase to get you up to the IF you are claiming. As your VI increases the TSS/hour you can hit increases as well due to NP having that 4th power involved.
There’s a blog talking about how to calculate all these metrics. You could attempt to back fit their assumed VI for each duration/IF tuple.
FTP is considered to be the maximum effort you can hold for 1 hour and break down afterwards (=100TSS). So if you’d be able to hold that power for 2 hours, than it wasn’t your FTP.
100TSS for one our is only possible for one our. To hold the maximum power for 2 hours, the watts need to be lower and TSS can’t be 200 for two hours but accordingly lower ( 187 in your chart).
The reason is that not duration alone is used for TSS but intensity, too. And the longer the effort, the lower your maximum intensity for that duration must be.
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Think of the intensity levels as values of RPE instead of exact Intensity Factors (IFs). Let’s say you where asked to ride all-out for 3 hours. Based on the above post there’s no way that you can ride at 100% of your FTP for the whole 3-hr duration, but you possibly can at 95%. That 95%, even if it’s not 100% of FTP, is still an all-out effort for that given duration so you give it a score of 10 on your estimate.
Sorry gays, I’m still not really satisfied by the explanations 
Of course I get it that one can not hold the FTP for longer than an hour (by its definition), but one can hold the lower intensities for hours, without the decline in the intensity, say level 2/3/4.
Other way around, what if I want to put a estimated activity of 5min@140%FTP. An all-out effort of 5min in TR estimate equals 8TSS (rate=96TSS/h). By the table of Tr.Peaks you would get a rate of 120TSS/h, for the all-out effort, what is logical. Of course, the duration is a fraction of the hour, but you have created those TSS. And again, of course you can not hold that effort of 140%FTP for a longer period of time, like an hour or more.
For the people that are maybe interested to analyse the data by themselves, I have used simple Excel:
I have made a graph of my year TSS estimate per week, from my HR data, based on the TrPeaks table. The calculation is based on average heart rate compared to my treshold heart rate. One step in between is the table from Joe Friel site, RPE to %LTHR.
I did that because a lot of time I did not have a power meter on my bike, and wanted to see if I can made a review of my training load, other the like Golden Cheetah TRIMP graph (also heart rate based) that is very similar to PMC of Tr.Peaks.
First I made a exponential function that fit the table.
The formula is: y = 1.327736e0.044035x
Where y is the TSS/h and x is the percentage of your threshold heart rate.
- See what the average heart rate is that week, and calculate the percentage of your threshold heart rate.
- Calculate the rate of TSS/h using the exponential formula.
- See how many hours did you train and multiply the rate of TSS/h with the hours.
My year graph looks like this:
You can also see that my weeks TSS were going up-and-down throughout the whole year, from week to week. That explains a lot poor results. Only positive thing was that I was not burned and had enough rest. July was intentionally low on TSS, summer vacation… and letting go of this season.
The last 2 weeks I have started the TR Traditional base (for the first time), and hope that I am going to be consequent 
I agree, the how the drop-down “intensity” list in the manual workout entry translates to estimated TSS makes no sense whatsoever. Intensity 5 is “tempo”, and it renders 56 TSS per hour, so basically a little over half of your threshold intensity. But we all know tempo is 80-90% of threshold. “Recovery” is set at 1 and gives 30 TSS per hour. Really, you don’t accumulate just 30 TSS per hour when in recovery intensity. So either change the definitions of 1 to 10 - maybe just drop the word descriptions - or change how this number translates to TSS. For example:
- Option 1 - treat this number as RPE for an hour-long effort, so 10 would be going all out (threshold) and accumulating 100 TSS per hour, 6-7 would be Zone 2 (60%-70% of FTP). Normally threshold intensity is at an RPE of about 8,5, but here you’d have to understand this as a number that’s scaled to one hour. Drop the current (misleading) word descriptions. The problem arises when you have a 20-minute workout above threshold, like a TT or 5k run, but then you can use the custom TSS box.
- Option 2 - leave the descriptions the way they are (1=recovery, 5=tempo, etc.), but translate to TSS appropriately, for example: tempo rendering 85 TSS per hour, recovery rendering 50 TSS per hour, etc.
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For MTB I wear a wrist HR (Garmin FR235) and use the HRSS score that the Strava Elevate App gives me. Its consistent and seems to be relatable to how hard it feels I went. Using the TR RPE estimates really seems to be very hit and miss.