What are the Fatigue, Fitness, Form Numbers in Training Peaks?

by | Jan 25, 2021 | Training

What exactly are the Fatigue, Fitness, and Form numbers in Training Peaks? Many athletes get too concerned about these numbers, even without understanding exactly what the numbers represent or how to setup programs like training peaks to calculate the numbers accurately.

Common questions are: ‘Why is the fitness number decreasing?’, and ‘Why is my friend’s score higher?’

Don’t panic. Here, we’re going to break down what your Training Peaks Fitness Report really tells you.

This is a view from the Training Peak Mobile App


Fatigue, Fitness, and Form (also know as Chronic Training Load, Acute Training Load, and Training: Stress Balance, respectively) are metrics in Training Peaks taken from a daily Training Stress Score and reflected in the Performance Manager Chart (PMC). These numbers reflect your training load over 45 days (Fitness) versus your last 7 days (Fatigue) and the balance of these (Form).

As an example, if you train a lot this week at a training camp, then you are tired (your fatigue is high) and so your form is not going to be at your best, but after taking a week off, you will see your form recover as the fitness (average of last 45 days) comes up and the last 7 days decrease. (that’s hard to say in a simple way.)

If you are collecting good data, this can help you know how and when to progress your training load gradually up during base phases (general preparation) and then recover adequately during your race phases.

*note that Strava and other apps use similar models to express training load

More on definitions from the PMC chart and TSS from Training Peaks:

Cautions & Common Errors:

  • To use CTL/Fitness score you need good data – Your data analysis is only as good as the data you feed it, and it only knows what you feed it. So 64 tss/day in the image above won’t reflect those rides you forgot to upload, or the ride where you power meter read really high might spike it up higher, or you might have accidentally uploaded the same workout twice.
  • Changes in seasons/sports or data collection mean it needs time to recalibrate and perhaps get cleaned up (or not used!). Change to a focus on feeling, daily goals, and performance metrics (e.g. how are your times/numbers/relevant things for that period of training)
  • You may increase the intensity, or do more cross-training and be very tired/sore, but see a decrease in your Fitness (CTL) if you are training for less time (like when a cyclist runs in the offseason)… this is where context and having a plan is important.

This is a view of a workout window in Training Peaks Calendar View on a Desktop

Stressful “Problems”

  • Your friend has a higher Fitness (CTL) – They might very well train more and so they carry higher daily training stress, but if you find that you are fitter or train more, than this can be an issue in how one of you has your threshold set (remember that TSS comes from your threshold setting) and/or different modes of training, so the TSS may not be as relevant or at least different in how it is calculated.
  • My Fitness is Decreasing (Yelp!) – This isn’t a bad thing. Fitness (CTL) may drop if you are not training as much, which is common in a recovery week, or an off-period in the year. It is also possible you are quite tired/sore from starting to cross-train or strength train and so your training load is lower but you are okay with this as you expect your fitness and capacity for those sports will grow in the longer term (e.g. you have a plan!)
  • I have high Fitness (CTL) but I am performing poorly! Remember that the TSS is not performance, it’s a model of your average training stress or ‘work capacity.’ Lots of people train a lot but perform poorly. (See the graphs I use below). Higher work output does not mean better performance always (e.g. at some point you are just tired!) so we want to also watch the peak power curve and how power is developing.

So what should you pay attention to?

While putting all of our training into one number to ‘rule them all’ is tempting it is not the best way or the only way. In fact, many coaches and athletes prefer to keep track of volume separately from the intensity and find this is a better predictor of ‘how you are doing’. Gradually increase your time and periodically go hard and progress those paces appropriate to your goals and current phase of training.

If you cross-train (as any Consummate Athlete should!)  or don’t have ‘great’ data then it is ok to just not use the fitness score. You can keep track of things like your volume (total time training) and also things like your peak power or pace for running. So you might gradually increase the time you train (mostly at low intensity) and then also have a focus on a certain interval duration or a test that you like to do periodically (e.g. the classic 20 minute time trial in cycling or 5-10k TT in running).

If you’re interested in finding out more about how these numbers apply to your training, book a call here to talk through your Training Peaks data!




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