[Anonymous]

OKee doke, here’s the nuts and bolts of CTL/ATL/TSB for those who want these details, I also attached a PDF if you’d like to just have it as a reference so you don’t have to go back to find this forum post.

Fitness (CTL)
TrainingPeaks represents Fitness (CTL) in blue font and the blue line (in the Performance Management Chart) through the TrainingPeaks ecosystem.
What is Fitness (CTL)
Chronic Training Load (Fitness) combines duration and intensity to provide a value of how much an athlete has trained historically. TrainingPeaks calculates CTL, by default, as the exponentially weighted average of daily TSS for the past 42 days (7 weeks). Note that, in effect, CTL represents the training an athlete has done in the past 3 months given the nature of exponentially weighted averages. 
Formula
CTLtoday = CTLyesterday + (TSStoday – CTLyesterday)(1/CTL time constant)
Fatigue (ATL)
TrainingPeaks represents Fatigue (ATL) in purple font and the purple line (in the Performance Management Chart) throughout the TrainingPeaks ecosystem.
What is Fatigue (ATL)?
Acute Training Load (Fatigue) combines duration and intensity to provide a value of how much an athlete has recently trained. TrainingPeaks calculates ATL, by default, as the exponentially weighted average of daily TSS for the past 7 days.  Note that, in effect, ATL represents the training an athlete has done in the past two weeks given the nature of exponentially weighted averages. 
Formula
ATLtoday = ATLyesterday + (TSStoday – ATLyesterday)(1/ATL time constant)

Form (TSB)
TrainingPeaks represents TSB (Form) in yellow font and the yellow line (in the Performance Management Chart) through the TrainingPeaks ecosystem.
What is TSB (Form)
Training Stress Balance (Form) represents the difference in the balance of training stress. TSB provides a measure of how much an athlete trained recently (ATL), compared with how much an athlete trained historically (CTL). TrainingPeaks calculates TSB by subtracting yesterday’s Fatigue from yesterday’s Fitness. Form (TSB) = Yesterday’s Fitness (CTL) – Yesterday’s Fatigue (ATL). TSB is not as a predictor of performance but as a measure of how adapted an athlete is to their training load. 
Formula
Form (TSB) = Yesterday’s Fitness (CTL) – Yesterday’s Fatigue (ATL)
Note:
The TSB value for today represents tomorrow’s value, not today’s, because athletes want to know how fresh they’ll be before tomorrow’s workout or race. 
A positive TSB number means that you are ‘Fresh’, or over adapted to your current training load.  
A neutral or nearly neutral TSB number means that you are adapted to your current training load. 
A negative TSB number means you are not adapted to a training load.

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