Quick Answer: TSS = (Duration × IF² × 100) / 3600. Optimal weekly TSS: Beginner 150-300 | Intermediate 300-500 | Advanced 500-800. CTL (fitness) rises slowly over 42 days, ATL (fatigue) spikes over 7 days.
Training Load Calculator
Calculate training stress, manage fatigue, and optimize your periodization strategy
Training Data
Current Training Metrics
Training Load Trends
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Training Recommendations
Periodization Calendar
The gear these numbers assume
Every pace, zone and power figure on this page assumes something is measuring it. These are the three that cover running, cycling and the threshold work in between.
Garmin Forerunner 965
Multisport with the training-load and threshold metrics most of these calculations assume you can actually see day to day.
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COROS APEX 2 Series GPS Watch
Sapphire titanium and the longest battery in its class, which is the deciding feature once sessions run past a few hours.
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Favero Assioma Uno Power Meter Pedal
Single-sided pedal power, the cheapest honest way to start training with watts instead of estimating from heart rate.
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Understanding Training Load Metrics
Key Metrics Explained
TSS (Training Stress Score)
Quantifies the training stress of a single workout based on intensity and duration.
CTL (Chronic Training Load)
Your fitness level - represents long-term training adaptations over 42 days.
ATL (Acute Training Load)
Your fatigue level - represents recent training stress over 7 days.
TSB (Training Stress Balance)
Your form/freshness - calculated as CTL minus ATL. Positive values indicate freshness.
Training Load Guidelines
TSB: +10 to +25
Peak form - ideal for racing and key workouts
TSB: -10 to +10
Training ready - good for quality training sessions
TSB: -30 to -10
Productive overreaching - building fitness but watch fatigue
TSB: Below -30
High fatigue risk - consider rest or reduced training
Pro Tip: Periodization Strategy
Build your CTL gradually during base phases (3-8 TSS points per week), maintain it during build phases, and reduce training 7-14 days before key events to optimize TSB for peak performance.