Help me understand Training Peaks lingo please


I’m a noob to training and to fitness in general. I’ve been using TrainerRoad for about 10 weeks now, and it has really helped me focus on form. When I first picked up cycling again after many years, I tended to throw myself at every challenge and blew up quickly. I’m now a disciple of Coach Chad and know my tempo from my threshold etc :smile:

I also use Training Peaks, although it may be too much analysis for me. I’m someone who likes data though. Here’s my TrainingPeaks data as of this morning:

Fitness 41
Fatigue 40
Form -5

I get that a bigger fitness number is better, and 41 is about my peak since starting all this ~3 months ago. But I’m looking for a ‘for Dummies’ explanation of the other two. I’ve read about the exponential weightings and the different timescales used, but it doesn’t help me answer what I hope is a very simple question:

Given the data above, should today be a workout day or a rest day?

All help in interpreting the data is gratefully received!

  • Pasta


Fitness = how much work you done over the last several month
Fatigue = how much work you’ve done over the last several weeks
Form = how much more fitness you have than fatigue

More fitness isn’t also better. The numbers are just a guide.



Link to the official source.


Fitness (CTL) is a rolling 6-week average of your training load (TSS). Fatigue (ATL - Acute Training Load) is a short term measure of your average training load, showing how far down you’ve pushed yourself in the last 7 days. Form (Training Stress Balance - TSB) is an estimate of how well rested you are relative to your fitness.

Looking at those numbers, you’ve been working the last week at about the same load as you have the last six weeks. It is not at all uncommon for me to have Fatigue numbers significantly higher than Fitness numbers, and larger negative form numbers this past season. As I tapered, Fatigue came down, Fitness stayed about the same and Form came up towards race day.

As to your question, you won’t like the answer… “It depends”.

With those numbers, I would train as normal, but I have trained at TSB (Forms) in the -30s before. I don’t let the CTL/ATL/TSB (Fitness/Fatigue/Form) numbers drive my training. What I do look at is when TSB is trending negatively and is down below -20, -25, -30… I check how I feel. Do I have other indicators that I’m tired and need to back off from a planned hard workout? Is there a recovery day or week coming up soon? If so, I’m more likely to push through that workout. If not, I’ll reduce the work, or just turn it into a recovery workout.

(Disclaimer - those are my numbers as a 70.3 triathlete this past season. In seasons past with lower CTL and overall training loads, I would know I was in a hole with a TSB closer to -15.)

There’s really no way anyone can look at your numbers and tell you exactly what to do with certainty, because those numbers will vary from person to person and situation to situation. I would guess that with those numbers, you’re fine to train as normal, but without seeing the graph and knowing anything else, I can’t be 100% sure.


Hey Nash, thank you for the reply. To the other respondents, thanks also. I’m aware of the definitions, it’s the meaning and use of the data I’m curious about.

OK, so let’s drop the exactly, and with certainty…Looking at my numbers, or the trend of my numbers, what information is actually there? My fitness and fatigue are both approximately 10*my form, and my fitness and fatigue are roughly equal. My goals are just to ‘get fitter’, with no specific competition in mind. How much help to me are these numbers?


  • Pasta


Honestly not much. Getting fitter is simply raising your CTL. To do that, your ATL will necessarily go higher and TSB will go lower. TSB (Form) is generally used to dial in peaks for competitions, so it will be of little use to you unless you feel like you’re over training, in which case it will go excessively negative.

Over time, if you’re pushing your training stress higher and higher, your CTL will go up. ATL will flucuate depending on how hard you’re working in one particular week. CTL and ATL don’t relate directly to Form in terms of how much larger they are, so the fact that they’re 10* form or 2* form is irrelevant.

If you’re not building to a particular goal, but just want to get fitter, I wouldn’t bother even looking at ATL/Fatigue and TSB/Form. Just work to keep CTL going higher. That said, you can get exactly that by using the TR calendar and just looking at the 6-week average TSS, which is basically the same thing as Training Peaks’ CTL.


I’ll take a shot at how I use them, although I really think @nash031 covered most of it above.

I think of them as Fitness/Fatigue/Balance - so my apologies if I switch terms somewhere along the way.

Over the long term you want to see increases in your fitness. This is your long term stress, and as you train longer (think over the years) your body will become capable of handling higher levels of TSS consistently. So the overall trend for your fitness should be upwards, but gradually. In particular you will see increases in the fitness number as you progress through a base and build program (if you look at those plans the TSS increases gradually week over week. Whereas with a speciality plan the TSS numbers tend to be lower - so the burden on your body is less while providing more specific training.

Basically - you want a negative balance most of the time, and only want to go positive when you are in a taper for an event.

So, how do you use this? Well, pick a structured training plan and volume level that you think will work for you and have at it. If you can handle the stress of your indoor and outdoor rides and are still hitting your interval targets then all is good. If you start having trouble hitting your intervals and your FTP is correct then you are likely overtrained - take a look at your balance, note it down, and try to avoid going that deep again.

For reference, I am currently sitting at a fitness of 96, fatigue of 124, and thus a balance of -28. At this balance level I’m fine for base rides and that’s about it - I couldn’t do any VO2 work and would struggle with threshold work. But that’s fine, because I’m in Sweet Spot Base High Volume II so I know I can afford to go that negative to really build that pyramid base. Once I transition to a build plan I will be much more cautious with my fatigue number to ensure I am able to hit my interval targets.

For someone new to structured work I’d honestly recommend not watching any of these numbers that closely. Your body will answer most of these questions for you and the primary benefit of these is tracking longer term trends and tapering for specific events.


This is succintly what I’d recommend. The new TR calendar shows the rolling 6-week average TSS calculation, which is enough for what Pasta wants and might actually be better since the other numbers aren’t there to confuse/distract. In fact, I asked Nate if they had plans to bring ATL/TSB numbers into their calendar, and he said they didn’t because they thought most athletes wouldn’t find much use in them, particularly if they’re just following a TR plan.


Brilliant. Thank you very much guys, that makes sense. I have only really been looking at Fitness, and the other two have never seemed that relevant to me. Fitness only!

  • Pasta