Interpreting Training Peaks metrics; or navigating the acronym hell that is your Training Peaks dashboard.

5 min readJun 15, 2017

After years of dedicated Strava love (which I still love actually), I’ve been having an gorgeous affair with Joe Friel’s daughter — Training Peaks, and I think I’m falling in love.

But I do have an irrational hatred of acronyms, and Training Peaks, for all its value is also a level of acronym hell that is probably mentioned somewhere in the back pages of Dante’s Inferno.

New Training Peaks user trying to figure out how to use Training Peaks metrics.

** Note that the following relates to the premium version of Training Peaks, which I currently have. I’m unsure whats available in the free version **

What follows is my own reference guide to understanding the metrics on the Performance Management Charts (PMC…ARGH!), which, if you use Training Peaks regularly, you should recognise as the fancy chart that changes over time every time you log in.

The PMC. Also known as “woah what the hell is going on here?!”

Below I explain mostly for my own benefit how to interpret the various metrics. I’ve shared as it may help you figure out what the hell is going on.

Chronic Training Load (CTL)

The first metric is Chronic Training Load.

You can think of Chronic Training Load (CTL) as ‘how fit you are’. Basically it’s an ongoing average of the daily training.

If you’re training daily or every few days and the workouts are getting progressively harder (i.e. your TSS score is trending up — that’s explained next) your fitness is going to go up.

Vice versa if you’re posting less frequent training sessions or not training as hard, the CTL trend will go downwards.

CTL currently at 57.4, though trending downwards Need to sort that one out.

Training Stress Score (TSS)

Next is Training Stress Score (TSS). This is a simple measure of how hard a given workout is.

It uses the data from your cycling computer or GPS watch along with other metrics like heart rate (or power if you use it) to figure out how hard a session was. The harder you work, the higher the TSS is.

If you’ve been just puttering around South Bank promenade at a slow jog, your TSS will be low.

Or, if you’ve just made it up a long climb and your heart literally explodes out of your chest, expect it to be high.

Indiana Jones has posted a high TSS after climbing Mt Coot-tha on his single speed bicycle.

Judging effort by combining CTL & TSS scores

You can combine the CTL score with a TSS score to gauge how hard an individual workout is:

A hard workout will be a TSS score 50%-100% above your current CTL score.
A moderate workout will be a TSS score 25% above your current CTL score.
An easy workout will be a TSS score 25% or more below your current CTL score.

For example:

At the moment, Training Peaks is telling me my fitness (CTL) is around 60. Last Saturday I did a steady 15 km run with a parkrun thrown in for good measure. Training Peaks scored this work out with a TSS of 97.8, 62% higher than my current fitness.

This would mean, by Training Peaks measures, that this steady long run was a ‘hard’ workout given my current level of fitness.

This is a very handy combination of metrics to use when trying to incrementally improve and I think a great way to think about how to approach workouts. You’re essentially using these data to try improve that underlying CTL score.

Fatigue (ATL)

There is also a metric called Fatigue or in Training Peaks acronym hell ATL (Acute Training Load). How this is calculated is by using a weighted average of you TSS scores (remember, the training stress scores).

Basically, what it does is figures out how tired you should be from the recent workouts you’ve been doing, and creates a fatigue metric.

So, I would expect if you’re doing lots of high intensity workouts which have high TSS values, you’re going to have high ATL scores. I’ll assume you bring down the ATL by doing recovery workouts with low TSS in addition to resting.

My fatigue is less than my current fitness, meaning a positive form value. If I was about to race, this would be OK, but given I’m training, I need to do harder work outs so I can improve my fitness (CTL).

Form / Training Stress Balance (TSB)

Lastly, Training Stress Balance (TSB) is probably the most important metric to consider when you’re getting close to race day.

According to Joe Friel and co this means form or ‘race readiness’. This is figured out by subtracting your current fatigue (ATL) from your current fitness (CTL) — and is a projection of your race readiness for the subsequent day (i.e. you’re far too tired to actually race on a day you trained, right?).

Training Peaks has several rough rule of thumbs to let you know ideal form to hit for race day.

Friel says a range of +15 to +25 on race day is a great place to be. If your form is negative, you’re too tired to race man! Take it easy for a few days!
Friel also recommends that during training phase keeping your form between -10 and -30 is also ideal.
Going below -30 may indicate injury risk. Above 25, you’re losing fitness.

Here’s a table to reinforce.

Go out there and get training!

Now, Training Peaks does have their own articles covering these metrics (linked below). I just wanted to rewrite them in less complicated language. Unsure if I achieved that, but hopefully this helps others figure out what the hell is going on with Training Peaks data.

Once you understand these basic metrics, you can really get a lot of value out of the application.

Heres some links to Joe Friel’s more detailed blogposts on the above metrics, which I relied on heavily in my own interpretation, and I highly recommend reading them if you’re trying to maximise your utility of Training Peaks.