Pez Cycling News Toolbox Articles

Hi everyone - I’m a contributing author to the content on Pez Cycling News. I submit an article roughly once a month and aim to highlight some cycling-related research. I also try to explain how you can incorporate the results of that research into your own training.

In this months article, I discussed some of the science behind micro-intervals and why they’re such a potent training stimulus. Hope you enjoy it!

If you do get a chance to spend a few minutes reading through it…Let me know what you think, or if you have any other questions!


Interesting read, I’ve tried to do a couple of the micro interval workouts that Xert has recommended to me recently but I’ve had to quit on the last set each time as I just couldn’t hold the power and then the Smart demands increased leaving me in a death spiral of failure and despair! I do very much prefer them to the 5 x 3 mins at 120% intervals though.

FWIW, I do my micro-intervals (20-10’s, 30-15’s, and 30-30’s) in SLOPE mode (2.0%) - I don’t rely on ERG.

There are some micro-workouts in Xert that I will use ERG/AUTO mode for, such as Smart - Let the Sparks Fly and SMART - My Way or the Highway workouts.

I don’t think literally anyone likes doing those… :face_vomiting:

Yes I do them in slope mode, it’s my legs that go into a spiral of failure. I do all my workouts in slope as I don’t like ERG mode at all, probably all the years of riding a mag trainer and then a fluid trainer before we got a smart trainer.

I really like to do micro intervals. Only with irl started again I only seem to have yellow stars, so when to do these workouts?

Been seeing some of your hard rides & races on Strava. I’d bet that those races give a similar Focus duration to Ronnestads/Billats! Mind sharing the Focus (and specificity) for some of your races?

For example, I just did a 30 min Billat-style workout on Thursday and ended up with a PURE 4:30 focus (Puncheur Focus Type).

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Yesterday’s race for example had a 2:58 focus with mixed specificity.

They are easier if you do what you’re showing in the screen shots above. You reaaly need to do the on intervals at a much higher power that for the steady state.

My own favourite way of doing these is 4 x 8 x 40:20 with XSSR goals, say 200xssr for 40 seconds and 100xssr for 20 seconds this is the same as doing 167xssr x 8 minutes.


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Have you had a chance to work through the Academy series videos? (at least twice :slight_smile: )
They are meant to be watched in order but this snippet shows you why %FTP based intervals are not ideal (VO2max example) –
Episode D3 - Mastering Xert - Discover - Fitness Signatures and Conclusion - YouTube

This article outlines the various SMART interval options including MMP (video snippet example) versus XSSR and others –
Advanced Workout Design using SMART Intervals – Xert (

You can also skip to the XSSR sections in podcast #4.
Scroll down to discussion points timeline.

The gist of the PCN article is there is another way to achieve the benefits of VO2max training.
You can get similar training benefits (or arguably better) without the higher risk of failing long intervals. You can see that displayed in your two examples. They aren’t quite equitable but the principle applies.
The first shows predicted failure points on three out of four intervals.
The second is a walk-in-the-park in comparison, BUT you got the intended training benefit.
Which would you rather do? Perform a workout that potentially beats you to death or consistently complete workouts scaled to your signature and/or constructed in ways that achieve intended training benefits without leading to failure?

Keep in mind Xert’s model is based on low, high, and peak strain. There is no TiZ to track. :wink:
That is one of the paradigm shifts in their model.

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For me there are a couple of thing that I like about the XSSr intervals:

The difficulty of a particular workout never changes if every step is XSSr even as your Fitness Signature changes.

The really nice thing about constant XSSr (whether long or short intervals) is that they start off hard and then tend towards threshold. This has the effect of getting your heartrate up quickly and keeping it there.

Here’s an example of a 1 x 8 x 40:20 at 300:150 XSSr. I wouldn’t have wanted to do another set of these at this intensity but you can see that my heartrate was at it’s highest value by the end of the second interval and stayed there.

The difference between the stead state and intermittent intervals you showed above, is that MPA is drawn down for longer on the intermittent ones and that is what drives the higher difficulty score.



I actually talk a little about XSSR intervals in the newly published Mastering Xert - Perform videos! I talk about SMART Intervals (including XSSR intervals) in Episode P2 :slight_smile:


The benefits of SMART intervals are prevalent all around. Low, high, or peak intensity. Even RIBs.
Go to Xert - Workouts (
Set to Show 100.
Search for “smart”
Sort by difficulty rating (diamonds),
Click on a title to view a workout in Workout Designer to see which intervals are SMART (several types).
Even the active recovery workouts rely on XSSR.
SMART intervals ensure precise doses of strain tailored to your current fitness signature.

If you prefer traditional workouts by all means include them if you’d like, but remember.
%FTP blocks are dumb in comparison. :wink:


You left out the nitty-gritty below the chart. :wink:

This particular workout doesn’t have any %FTP intervals. Some intervals are based on LTP.

I am unclear what you are expecting to happen. It will feel like any other trainer-controlled workout. Where you may notice a difference is with SMART dynamic duration or dynamic power intervals.
For example, a dynamic duration interval can lengthen or shorten depending how closely you maintain target watts. A dynamic power interval will modulate power depending how closely you maintain the target. With my trainer I will notice a bit of a kick right before the interval ends if I consistently undershot the target. Other times it may ease up early (overshot the target).

Here’s a workout with dynamic types in action for both work and rest intervals – (1) Xert - Workout Designer (

If you want to view all possible options, click on an entry under the Power column and select the dropdown menu. Same goes for RIB power.

Reference –
Introducing Smart Workouts – Xert (

I touch on this a bit in the latest videos (as mentioned previously).

XSSR intervals will only be dynamic when fatigue is involved (either the interval starts with MPA < PP or the interval intensity is set to > 100 XSSR). The way XSSR works (in a simplified explanation) is to fix the Strain Rate by keeping your current power output equal to some proportion of MPA - notice how the Power line in this workout tracks identically to the MPA line:

Notice that the grey arrows (signifying the difference between MPA & power) will stay fixed throughout the duratino of the interval. Assuming that your smart trainer can hold power fairly steady, you likely won’t notice any change in the target power outside the pre-determined curvilinear decline in target power.

Just know that if you were to be below target or above target, that would affect MPA which would, in turn, affect the current power target.

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