Training Peaks – Fitness, Fatigue & Form What does it mean?

Form, Fitness and Fatigue.  It is the first thing you see as you log into your training Peaks app. Many athletes buzz over it but for some, it is an immediate cause for anxiety.  Why does that number keep climbing? Pink, that is close to red and it is my fatigue rating…Is it a bad thing that number is so high today?  OH NO!  Why is my form in the negatives?

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Fatigue (ATL) – Fatigue is a representation of acute training load.  This is the impact that each individual workout has on the overall training load.  A multiple hour workout, or a workout with very high intensity will have a greater ATL score than a recovery workout or a very short run.


Fitness (CTL) – Fitness or Chronic Training Load is an indication of the cumulative effects that training has had over time.  With consistent training and workouts this will continue to climb.  During periods of lower training stress, recovery weeks and down times your CTL will decrease.  You can even see periods of decrease when doing incredibly hard VO2 intervals.  Because this is based on frequency, intensity and duration a change the decrease in duration can cause a downward shift in CTL.


Form (TSB) – Form or Training Stress balance is the difference between Chronic and Accute training loads resulting in an estimation of your level of fatigue/freshness.  This is a gauge of where your fatigue level and a low or even a negative number is a good indication that the body is being stressed, which, with recovery, will ultimately lead to fitness gains.

It is important to know that each of these measures is directly linked to your threshold (power/pace/hr) and without accurate ranges, these numbers will hold very little validity.  

It is also very common for these numbers to seem exaggerated when coming off of longer bouts of little/no activity as the data is starting from a baseline of zero.  These numbers will stabilize as the algorithm has more data to process and a better understanding of what your training load is.  Think of it like Garmin’s Recovery score (if you are familiar with that).  When you don’t exercise much for 3-4 weeks and hop back into it your Garmin gives an alert recover of 76 hours, or some other crazy value, before your next workout.  Fatigue does not feel high and you are ready for the next day’s workout but your Garmin thinks you have been a lazy bum and have come in off the couch.

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