Designing the Perfect Interval Workout Using W’Bal

Starting with Progressive Overload

As most of you likely know, one of the key fundamentals of exercise is progressive overload. This means if you want to get stronger you need to go to failure or at least close to failure to tell your body it needs to repair itself and get stronger so next time this same exercise is easy.


How many intervals should I be doing?

Everyone knows that they have a limited amount of time, that they can sustain a hard-effort. We can clarify hard-effort as anything above your FTP. But how much time is that exactly? Meaning should I do four 2-minutes intervals @ 120% or maybe they should be 2:15 not 2-minutes. Since each athlete has a unique amount of anaerobic capacity (W’). You should train with custom intervals matched to your personal W’. You can hunt by trial and error, or you can use this cool TrainerDay feature called W’ Balance (W’Bal). This same feature has been in GoldenCheetah for a long time, but we feel we simplified it.


Finding the perfect interval workouts

This is a fairly deep subject but just starting with the basics is a huge step forward and something that many workout authors overlook. So for this article we are talking about intervals above your FTP. You want to tax your anaerobic system with just the right stimulus.

The basic idea is when you are above FTP your anaerobic work capacity (AWC or W’) diminishes. Many people also call this “burning matches.” You only have so many matches to burn. Although when you drop below your FTP your W’ recovers, or the match book fills back up, slowly. The great news is we have added W’Bal to our workout creator.

5000+ Is Too Many Choices

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I would like to point out, I don’t feel a 10-minute warm-up is enough, it should be closer to 20. It just improved the visibility in this example.

How to use the W’Bal Calculator

Turn on the W’Bal feature. Enter your FTP or if you know it your CP in the CP box. Enter your W’ (how to calculate) and you are good to go.

The red line shows you’re predicted remaining energy and you can see at the end of this set of intervals your remaining energy is at the bottom this W’Bal predicts you are completly fatigued at the end of the intervals. Perfect.

Many scientific studies have proven the validity of these formulas.

In this example on the left, if you have a W’ of 20kJ, and a FTP of 200, with those intervals, you will burn all your matches. The interesting thing is if you had a 300w FTP, you could not complete this workout (read this article to find out why). Another benefit is that designing workouts that you know you should be able to finish can help inspire you to push a little farther. If you make this last interval a little farther and you can finish it (i.e. you can go below zero) that frequently means your W’ or possibly FTP is likely a little higher than you thought.

View My Example W’bal Workout

Watch a 6-minute video below showing you how W’Bal works in TrainerDay

Additional Reading

Here is a good article describing the value of W’ and W’Bal
The below link is deep but if you really want to understand, Mark from GoldenCheetah knows the ins and outs
This video from Mark is a good balance between deep and useful

Mark has done lots of writing and videos about W’ and W’Bal that are worth learning more about. You can also google Dr Skiba to find the direct source of much of GoldenCheetah’s science.

We use the Skiba-Froncioni-Clark W’bal formula.

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