SAINT-TRI plans use three working zones from the German school of endurance training: G1 (foundational aerobic endurance), G2 (upper aerobic endurance) and EB (development zone, at and above threshold). Three zones instead of five or seven — because on the road, in the water and at hour four of a race, simple is what actually gets executed.
Why a three-zone system?
Most zone charts slice intensity into 5–7 bands. Physiologically interesting; practically, athletes spend half their sessions wondering whether they're in "zone 3 low" or "zone 2 high". The German model — used for decades in European endurance sport, where Jo Spindler's coaching school comes from — keeps the distinctions an athlete can actually feel and repeat:
| Zone | Name | Feels like | What it builds | Share of training |
|---|---|---|---|---|
| G1 | Foundational endurance | Conversational. You could go on for hours. | Aerobic engine, fat metabolism, durability | The large majority |
| G2 | Upper aerobic endurance | Controlled, focused. Talking in short sentences. | Race-pace economy, aerobic power | Measured doses |
| EB | Development zone | Hard. At/above threshold. Watching the clock. | Raises your ceiling: threshold & VO₂max | Short, structured doses |
What a real session looks like
Here is an actual bike session from a SAINT-TRI plan, exactly as it arrives in the Final Surge app:
- 4h G1 with 4 × (2 min EB / 10 min G2) — four hours of foundational endurance, with four short development efforts, each followed by ten minutes of controlled upper-aerobic riding.
Every element has a job: G1 volume builds the engine that carries you through the last 90 minutes of a race; the EB touches raise the ceiling; the G2 blocks teach your body to hold strong output while already working. No junk minutes.
The mistake the zones prevent
The most expensive habit in amateur triathlon is the grey zone: too hard to develop the aerobic system, too easy to raise the ceiling. It usually comes from making G1 days faster "because it felt too easy". In a correctly built week, easy days protect hard days — that's what makes the hard days actually hard.
How to find your zones
- Field tests — a 20-minute threshold test on the bike and a similar run test give workable first estimates for each sport separately.
- Physiological testing — INSCYD-style analysis pins the zones to your metabolism and shows how they shift as you get fitter.
- Re-test every block — zones move as you adapt. A plan that never updates them is training your past self.
Every SAINT-TRI Smart plan is written in G1/G2/EB with your personal targets, delivered to your watch and bike computer — plus 50+ methodology videos where Jo explains the why behind every zone and session.
Start my plan →FAQ
What do G1 and G2 mean?
They come from the German term Grundlagenausdauer — foundational endurance. G1 is conversational aerobic work; G2 is upper aerobic endurance, noticeably harder but still controlled.
What is the EB zone?
EB — Entwicklungsbereich, the development zone: work at and above threshold, used in short structured doses (e.g. 4 × 2 min on the bike) to raise your performance ceiling.
How do I know my personal zones?
Start with per-sport field tests, or measure precisely with physiological testing such as INSCYD. Zones differ between swim, bike and run — and they move as you get fitter, so re-test each training block.
