training · zones · beginners
Training zones A1, A2 and A3 explained
By Sampa Natação Team · Updated on · 3 min read
A1, A2 and A3 are aerobic intensity ranges: A1 is easy and restorative, A2 is moderate and sustainable for a long time, and A3 is hard, just below the anaerobic threshold.
In a swim workout, every set comes with a zone: "4 × 50 free @1:10 A2", for example. The zone tells you how hard that part should be swum. Getting the zone right is what turns meters into adaptation: swimming everything hard wears you out without progress, swimming everything easy doesn't challenge the body.
Why train by zones
Each intensity stimulates a different system. Easy work builds the aerobic base and helps you recover; moderate work increases your ability to hold a pace; hard work raises your threshold and speed. A well-designed cycle combines the zones across the week, alternating load, overload and recovery weeks.
The zones, one by one
| Zone | How it feels | RPE | Reference pace |
|---|---|---|---|
| A1 · easy aerobic | You could chat easily; relaxed breathing | 2–3 | CSS + 10 to 15 s |
| A2 · moderate aerobic | Comfortable but focused; you can keep it up for a long time | 4–5 | CSS + 5 to 10 s |
| A3 · hard aerobic | Takes concentration; short sentences | 6–7 | CSS + 2 to 5 s |
| Threshold | Long-race pace; at the edge of sustainable | 7–8 | ≈ CSS |
| VO2 | Very hard; short sets with rest | 8–9 | CSS − 3 to 6 s |
| Anaerobic | All-out effort, a few seconds or meters | 9–10 | Maximum speed |
A1 — easy, restorative
This is the zone for warm-up, cool-down and recovery days. It feels too easy, and it's meant to. The gain comes from piling up meters with good technique, without fatigue.
A2 — moderate, the base of training
A2 is where most of the volume lives for people who swim for health or for open water. You feel you are training, but you can repeat the whole set at the same pace.
A3 — hard, just below threshold
In A3 your breathing gets shorter and your focus sharpens. Sets usually have short rests, such as 6 × 100 with 15 seconds of rest. It's a powerful zone, but it demands recovery.
How to find your pace in each zone
The most practical way is the CSS test (critical swim speed): you swim 400 m and, after recovering, 200 m, both at your maximum sustainable effort. CSS per 100 m is calculated like this:
With that number, the table above turns into concrete paces. In the Sampa app, paces are calculated automatically from your latest assessment, and the coach re-tests every cycle. Other tests, such as the T-30 (swim for 30 minutes and measure the distance), give similar values.
Common mistakes
- Swimming A1 too hard because it "feels like too little". Easy means easy.
- Starting the set in A3 and finishing wrecked: the right way is to hold the same pace from the first to the last repeat.
- Ignoring RPE. Your watch shows heart rate, but in the water it is less reliable; perceived effort is a great compass.
- Using paces from an old test. If you have improved, your zones have changed.
After the workout, log in the app how it went and your actual RPE. Comparing the target RPE with the RPE you felt is what lets the coach adjust the load for the coming weeks.
Want to train with coaching?
At Sampa Natação every workout is prescribed set by set and adjusted based on your feedback.
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