Training Stress Balance — how to use it

If you only watch one training-load number, watch TSB. It tells you whether you are fresh, neutral or fatigued. Here's how to read it without overthinking it.

The formula in plain English

TSB = Fitness (CTL) − Fatigue (ATL). Positive means you are above your fitness baseline of fresh. Negative means you are accumulating more fatigue than fitness.

The four zones

• +5 to +25: Fresh. Race-day window.
• +5 to −10: Neutral / productive training.
• −10 to −20: Loaded. You're building. Expect heavy legs.
• Below −20 for >5 days: Risk zone. Overreaching tipping into overtraining.

Common mistakes

1. Trying to race at TSB −15. You'll bonk.
2. Tapering too long. TSB >+30 means you've lost some fitness.
3. Reading TSB without context — it ignores sleep, HRV and life stress.

How Radiant Health folds it together

We compute your TSB from Strava / Garmin / Health Connect workouts, then combine it with HRV and sleep to call the right session for today. You don't have to memorise zones — the briefing tells you what to do.