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Help & Knowledge Center

Understand the sports science, equations, and mathematical models that power your training analytics.

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Performance Management Chart (PMC)

Learn how rolling averages of daily training stress are modeled mathematically to estimate your accumulated **Fitness (CTL)**, **Fatigue (ATL)**, and **Form (TSB)**.

CTL (Fitness) ATL (Fatigue) TSB (Form)
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Physiological & Heart Rate Metrics

Understand training load without a power meter. Includes details on Friel Heart Rate Zones, **Heart Rate Stress Score (hrSS)**, **Aerobic Decoupling**, and **Heart Rate Recovery (HRR)**.

LTHR hrSS Drift (%)
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RPE & Perceived Fatigue (sRPE)

Explore Foster's **Session RPE (sRPE)** model and how comparing subjective effort to sensor data via the **Fatigue Gap** highlights under-recovery, heat fatigue, or disease.

sRPE Load Fatigue Gap Borg CR-10

Mechanical & Power Metrics

Review the core algorithms for power meters: **FTP**, **Normalized Power (NP)**, **Intensity Factor (IF)**, **TSS**, **Critical Power (CP)**, and anaerobic tank **W-Prime ($W'$)**.

TSS W-Prime (W') NP
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