Workout Library

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    I am making cycling substitutions for runs until I can safely return to outdoor running after a recent snowstorm.

    Yesterday I did a drag and drop of CF6. I notice that the TSS of the workout drops from 47 in the library to 41 when copied onto the calendar. For some reason the intensity factor is reduced.

    I made the substitution for a RF26 run workout which has a cool down and a slightly less TSS as a result. 47 vs 53 TSS, no bid deal, but 12 points lower after the copy.

    I have Training Peaks synchronized with my Zwift account and when I rode the workout Zwift would alert at the top end of Zone X. The result was that at the end of the ride I had a TSS of 50 for the ride.

    I don’t understand what is going on, but as a practical substitution I’m satisfied.


    Hey Charles,
    David may come in to give more clarification here but for now – I went and ran a test on my own account dropping a power based cycling workout from the workout library to my calendar and there was – as you experienced a change in TSS. For me it was only 1 TSS point.

    Here is my initial theory on this – The workout as it sits in your library is using a arbortery FTP number – as it is not applied to your settings in your library. I further tested this my going to the source library from our Training Peaks account and the TSS from the original workout is the same there as it is in my personal account library. Once you move it to your actual calendar it will then use your individual zones and the % time in each zone to determine your IF and then TSS (a composite number that takes into account the duration and intensity of a workout to arrive at a single estimate of the overall training load and physiological stress created by that training session). Estimate being the key word here – as it’s all estimating until you actually do the workout.

    Then if you use that workout in Zwift, there will most likely be slight variances in the zones, that don’t match precisely with the planned (estimated) workout. I would need to dig deeper to see how Zwift zones are set and what these slight variances might be, I say this is in particular from Zone 2 and up.

    So I know these changes can be perplexing I would not get too worried about the slight change you are seeing – and if ever in doubt during a workout (ie if you feel like a zone is too high and you are working too hard for what is planned) then if in ERG mode you can use your offset to reduce the load by up to 10%, or if not using ERG you can just ride a few watts less (or more) till you feel the effort matches the zones more appropriately.


    Sorry, I didn’t intend to make this a trip down the rabbit hole. From what little I know about Zwift and the various equipments that could be a career with job security for a long time…

    I just want to keep up the CTL during a spell of bad weather and I’m good.


    Thanks for asking the question Charles…this was something I noticed recently myself when working between the calender and different intensity metrics so I was happy to actually explore this a bit more.
    You never know who else out there might be wondering the same thing and now glad you asked!

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