What CTL, ATL, and TSB tell you
CTL (Chronic Training Load) is your 42-day rolling average of daily TSS. It represents fitness. ATL (Acute Training Load) is the 7-day average and represents fatigue. TSB (Training Stress Balance) is CTL minus ATL: how fresh you are right now relative to your fitness. The three numbers together describe whether you are building, maintaining, or burning out, which is information you can't get from looking at last week's hours.
How the optimizer plans your build
You enter your current CTL, current ATL, target CTL on race day, days until race, weekly hours cap, and rest days per week. The calculator distributes TSS across the remaining weeks with a linear ramp, then applies an automatic taper:
- Two weeks out: training volume drops by 40%.
- Race week: drops another 60% from baseline. Intensity is preserved; volume is what gets cut.
- Race-day TSB target sits between +15 and +25, the band most athletes race best in.
The injury risk warnings
The model flags any day where ACWR (Acute:Chronic Workload Ratio) exceeds 1.5 or where TSB drops below -30. Sports science research links those thresholds to elevated soft-tissue injury risk. Treat the warnings as a signal to redistribute load, not as a verdict.
Training Load Optimizer
Set your current fitness, target CTL, and race date. The optimizer projects day-by-day training stress with automatic taper scheduling and injury risk warnings.
FAQ
What is CTL and why does it matter?
Chronic Training Load (CTL) is a rolling 42-day average of daily training stress. It represents your fitness level. Higher CTL means you can sustain more training, but building it too fast risks injury.
What TSB should I have on race day?
Most athletes race best with TSB between +15 and +25. This means fitness (CTL) is high but fatigue (ATL) has dropped from the taper. The optimizer schedules a 2-week taper automatically.
What do the ACWR warnings mean?
Acute:Chronic Workload Ratio (ATL/CTL) above 1.5 indicates a spike in training load relative to your fitness base. Research links this to elevated injury risk. The optimizer flags these days so you can adjust.
Methodology
Uses Coggan's Performance Manager Chart (PMC) model with 42-day CTL and 7-day ATL exponential moving averages. TSS is distributed across training days with a linear ramp, then automatic taper (-40% week -2, -60% week -1). Warnings trigger at TSB < -30 or ACWR > 1.5.
Want to verify the math?
Explore 170+ reference calculators built by engineer-athlete Thomas Prommer. The technical foundation behind our AI.
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