# Training Zones

The single source for all intensity zones. EVERY power target in the
system — workouts, interval structures, plan steps — derives from these
definitions. Other files reference zones by number; they never redefine
the FTP percentages.

Zones are based on **% of FTP**. Heart rate (% of LTHR) and RPE are
secondary indicators.

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## Zone Overview

| Zone | Name               | % FTP     | % LTHR    | RPE  |
| ---- | ------------------ | --------- | --------- | ---- |
| Z1   | Recovery           | < 55%     | < 70%     | 1    |
| Z2   | Aerobic Endurance  | 56–75%    | 70–85%    | 2–3  |
| Z3   | Tempo              | 76–90%    | 85–95%    | 4–5  |
| Z4   | Threshold          | 91–105%   | 95–100%   | 7–8  |
| Z5   | VO2max             | 106–120%  | >100%     | 9–10 |
| Z6   | Anaerobic Capacity | 121–150%  | —         | 10   |
| Z7   | Sprint             | > 150%    | —         | 10   |

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## Zone Purpose

- **Z1 – Recovery:** active recovery, circulation, fatigue reduction. Very easy, full conversation.
- **Z2 – Aerobic Endurance:** aerobic base, fat metabolism, durability. Long/endurance rides, climbing pacing.
  - *Upper Z2 (aerobic threshold / AeT):* transition to Z3, approx. FATmax, RPE 3–4.
- **Z3 – Tempo:** muscular endurance, fatigue resistance, sub-threshold climbing. Controlled but demanding.
- **Z4 – Threshold:** increase FTP, sustained power. Hard but steady.
- **Z5 – VO2max:** maximal aerobic power, supports FTP. Alternative target: 90–95% of VO2max power. Up to ~8 min.
- **Z6 – Anaerobic Capacity:** anaerobic power, repeatability of hard efforts. Up to ~2 min.
- **Z7 – Sprint:** neuromuscular power. < 30 s.

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## Z4 Subdivision

- Sweet Spot: 88–94% FTP
- Threshold:  95–100% FTP
- Over:       100–105% FTP

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## Application Rules (CRITICAL)

These are zone-level rules that apply across all sessions:

- **Fatigue:** high fatigue → shift the target down by one zone.
  Fresh state → allow the upper range of the target zone.
- **Recovery rides:** Z1 only.
- **Endurance rides:** Z2 dominant; occasional Z3 depending on fatigue.

Ride-type → zone-band selection for specific workouts (e.g. which zone a
VO2max or threshold session targets) is defined with the workout library
in decision-process.md. Discipline-specific pacing (e.g. long-climb
strategy) is defined in the athlete/discipline block.
