Interval workouts vs endurance/Z2


I am a 48 year-old recreational rider using Zwift in the winter months. Currently I ride 5 times a week / 7-8 hours. After two years with unstructured workouts, all-out rides outside, groups rides and races on Zwift I felt I hit a plateau and that it was to time get some structure into my training.
Since november a have been trying to train polarized. I try to do 3 pure endurance rides under LTP and 1-2 hard interval workouts each week.
I am using Xert and have seen all the videos and listened to the podcast.
According to the podcast my hard intervals should make me red/very tired and thereby help me plan recovery days.
But I am alway just yellow. :slight_smile: and Xert suggest endurance(Z2) rides all the time. even after easy 1½ hour endurance the day before. I know I can just adjust my freshness but was is the point of Xert then?
Now to my biggest question: why isnt there more difference in the data between my Z2 rides and hard interval workouts?
Yesterday I did a Z2 ride for 1½ hours. Total XSS 97 (low XSS 95, high XSS 0.9, peak XSS 1.3). Ended the ride with a short sprint. Polarity was 98:2.
Today an interval workout including 6x3 min (115% TP) ride for 1 hour. Total XSS 90 (low XSS 84, high XSS 5.1, peak XSS 0.8). Polarity was 93:7. How come 18 minutes at 115% does not result in more high XSS?
The workout felt much harder than the Z2 ride (as it should) but I cant really see that in the numbers and I just keep being yellow.
I know that the two workouts are using different systems - should that not make them more distinct in Xert? The difficulty rating was 80 for the workout and 69 for the Z2 ride. I had a 2 hour Z2 ride with a difficulty rating of 81 this weekend…
The two activites were both marked as “Rouleur”.
Can somebody help me out here? Maybe the question is a bit fuzzy :slight_smile:

What are your current Goals settings? (ATP, Athlete Type, etc.)
What is your status stars count?
Post the activity charts for your Z2 ride and that interval workout.

Freshness Feedback is the right tool to use when calculated form does not match how you feel.
I don’t think you necessarily need to use it based on what you’re saying. Post the info above so we have a clearer picture of your training.

Polarity ratio in Xert doesn’t refer to “polarized” training but you are accomplishing that based on your 5/2 week description.
See this post – Polarity stats - #3 by ManofSteele

There is a difference between 97 XSS in 90 minutes (Moderate) and 90 XSS in 60 minutes (Difficult). Think XSS per hour.
Specificity is a factor too. Do you have a grasp of that concept as it relates to the difficulty rating?

Reference –
Freshness Feedback slider
Difficulty Rating – Xert (


Actually intensity makes you yellow rather than red. Red means overall form is significantly negative and can happen due to low or high intensity. So yellow is normal with what you describe

That’s not really ‘zone 2’ (even if Xert doesn’t use zones). Rouleur means you spent time above threshold, which is well above z2. Difficulty that high is also a sign - should be much lower

I think that’s because you are adding intensity to your “z2” rides. You may want to try riding them well below LTP for the whole ride


Thank you both so much for helping me out here.

I am currently a 3 star (yellow) on a 30 day challenge with Athlete Type “GC Specialist” at a slow improvement rate.

Are these what you a asking for?

Duration 1:26. XSS: 97. Focus: Rouleur 06:01 (due to sprints). Specificity: Polar. Difficulty: 2½ diamonds.

Duration 1:05. XSS 90. Focus: Rouleur: 06:52. Specificity: Mixed. Diffictulty 3 diamonds. (intervals at approx. 115%TP)

Another “Z2” example:

Duration: 1:22. XSS: 87. Focus: Time-triallist. Specificity: pure.

The specifity makes really good sense to me. The Z2 ride was polar due to the sprint, but should have been pure if I want “clean” numbers. The workout was “mixed” which I guess is ok.

Wesley: I see your point about Z2 with sprinting at the end - not beeing really “Zone 2”. But as I understand - I should get all the Z2 benefits from the Z2 work (stimulating mitochondrial function the most) leding up to the sprint.

I guess what I am after is just a way of overviewing my high- and low intensity training during a periode. How much Z2 work have I done? How hard were my “high-intensity” workouts? Enough to raise my fittness level? I can do this with Xert but only after using much time crunching numbers and analyzing activities. Note that I have only been using Xert for a little over a month :slight_smile:
I also do realize that my Z2 training is at the upper end. Keeping it lower would perhaps create clearer numbers. But it´s so boring :slight_smile:
Thanks again for all your inputs.

Think this may solve your issue, riding towards the ‘upper end of Z2’ plus the addition of sprints is what is most likely keeping you in the yellow. There isn’t really any benefit to riding at the ‘upper end’ of Z2, you are likely just adding extra fatigue for very little (if any) physiological benefit.

Maybe try a few of the Xert Endurance workouts for a while , I suspect if you do that you will start to see more of a mix of freshness ratings and therefore a more obvious split in high and low intensity workout recommendations.

I find that if I just free ride on Zwift, I usually end up going too hard at some point, I’ve recently started using the Pacer Bots to keep me from doing this, and also mixing in the Xert endurance workouts , which at least are less monotonous than just riding plain Z2 on a trainer.

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Thank you - I think you are right.
I had given up on Xert endurance workouts. All suggested endurance workouts contains large portions of intervals over LTP, which to me is not actual Z2. Typically I create a Zwift custom workout with intervals in upper Z2 and ride with ERG and a movie on the iPad :slight_smile:

Edit: When using a filter I found the “SMART - Heart of Gold - 75” workout, which in wattage is very much similar to my own custom Z2 workout.

Just create a personal xert workout with the exact zones and interval durations you are after.

I’m not sure if you can view it or not but here is an endurance zone ride that i created and use…

Looks good!

My point was that Xert keeps suggesting me indurance rides that keeps me being yellow. I will lower my Z2 rides a bit and see if it makes a difference.

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Yes the “blue” zone ride i shared has no high and peak strain. Its either 80% of LTP or 90% of LTP. A good endurance zone based ride just under LTP.


Xert is a hybrid polarized system that includes a variety of endurance workouts (below TP) that include both easy (LTPish) and harder (tempo/SS range).
Additional easy workouts At or below LTP include –
All the Small Things
Back to Blue
After Midnight
Underclass Hero
Feeling This
The Strength to Go On (long one)

Like LikeIcon the ones you like :slight_smile: and they’ll rise on recommended lists. Dislike others to exclude them.
You can copy workouts to create tweaked versions of your own (and like them).
Liked also means they’ll show up on the drag and drop list on the Planner.

Then there are o/u LTP entries like Lucy in the Sky and Save Yourself. May not technically qualify as Z2 but I like to do them anyway and they confirm my LTP number feels about right.

Rather than mix strain levels on a Z2 ride/workout I periodically toss in a sprint workout like Adventure of a Lifetime which can easily be replicated outdoors.
Otherwise consider “Boring, for lack of a better word, is good.” :smiley:

You can use to tabulate your activities based on traditional zones and they’ll be classified as polarized, pyramidal, etc. I used icu’s Totals page for that purpose during my 120 day indoor TED experiment. I rarely visit icu nowadays, but it helped me confirm Xert was what I was looking for. Now I rely on the Progression charts to track my season-to-season fitness. I’ve gotten even better year over year results since that experiment. The key is taking further control as you learn how to self-coach.

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Spot on! 10/10 :grinning:
I will give a try on the side. Sounds like what I am after at this stage.

Thank you all for all your great input. Great forum!

Small thing but that won’t actually help with yellow status. The ‘problem’ from a Xert perspective is the amount of high intensity relative to your ‘high” training load. If you are yellow for a long time I guess your high TL is very low.

Here’s the chart explaining status.

The question then is whether ‘yellow status’ is accurate for guiding how often to do intensity and in my experience it depends… if ‘high’ TL is very low (eg after a long pure endurance base) I can take a week or more to get back to blue after a hard interval session (independent of how much ‘z2’ I do)… and if it’s higher high TL it’s quicker… there’s an algorithm with some logic there, per the chart, but whether it’s ‘optimal’ I’m not so sure. As an aside, if you want to polarise per Seiler, that would only be one high intensity workout per week (1 in 5 workouts) in your case, so perhaps following the recommended workouts is what you need… of course you can try two intensity days a week and just see how you feel / ignore the guidance.

The other thing to watch out for is that Xert considers everything below TP as endurance / helping recovery / not pushing you into yellow / in theory possible day after day, including riding at 99% TP, which is just not true. So if you do lots of threshold or sweet spot, you should pay attention to how you feel rather than relying on the training status / form / colour to guide workouts


I need to see how many days of just sub threshold workouts I could add before I went yellow. Unfortunately I think it would be a lot. More than I could I actually do, I’m pretty sure.

Having said that, if you keep your endurance days 2 stars or less, and let the intensity days push you yellow, it seems to work out.

Answer is infinite i.e. you never go yellow from purely sub threshold riding. You can try putting loads of sweet spot (or 99% TP) workouts in the planner and see.

I understand Xert 2.0 is meant to address this… and hopefully also the fact that a very long endurance ride can also reduce your ability to do high intensity the next day… let’s see!

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You would eventually go red though right?

I’ve ridden every day this week, including today (Thursday). Tuesday was intensity and put me yellow on Wednesday. I went blue today, but I was sceptical about being able to do intensity. This is where I give Xert a lot of credit. I was sluggish to start, but in fact, I was good to go. I think in the hypothetical case of 99% of TP for a few days, blue might be misleading, but those rides will tend to have enough bits over TP, where you might still go yellow. I’ll have to look back and see the conditions where multiple hard endurance put me red, which would be the other signal coming from the model to take it easy.

You know how you feel and if you are ready for another high intensity session. If xert thinks you’re ready but you know you aren’t just adjust your “Freshness Feedback” slider down a couple of points until the yellow turns back to blue on the day you feel ready to go at it again. This is one of the things the freshness feedback slider is designed for :+1: