Zone 2 and AI
Zone 2 Training with AI: Check It on Watch Data
Zone 2 training is easy to get wrong by feel. Instead of a separate zone 2 training app, connect your watch data through Intervals.icu and STAS, and ask ChatGPT or Claude whether your zone 2 heart rate training stayed in zone, using your own zones and recorded heart rate.
Connect Intervals.icu dataSTAS starts free, no credit card. A custom connector in ChatGPT or Claude depends on your ChatGPT or Claude plan.
Short answer
Set your heart rate zones in Intervals.icu, send your workouts there from the watch, connect STAS, and ask ChatGPT or Claude to check how much of a session was in zone 2. The answer comes from recorded heart rate, not from how the effort felt.
- ✓The check is only as good as your zone settings, so verify them first. The heart rate zone calculator gives an estimate to start from.
- ✓STAS passes zones, heart rate and workout detail from Intervals.icu to the AI when they are available.
- ✓If a workout has no heart rate data, the AI should say so instead of guessing.
- ✓STAS starts free, no credit card.
First useful action
A useful AI running coach starts with real training data
The difference is not a better prompt. It is pace, heart rate, load, workouts, goals, and recent context available in the chat.
Connect the source of truth
Intervals.icu keeps workouts, calendar, load, zones, and recent history in one place.
Let AI see real context
STAS prepares that data so ChatGPT or Claude can answer from your actual training, not a pasted summary.
Ask for the next decision
Start with a clear analysis or action: recovery check, missed workout, next week, or one session to adjust.
STAS reads only the training data you approve through Intervals.icu. Start with one practical question: current condition, a workout review, or what to change next.
Connect Intervals.icu dataRoutes compared
There are several ways to check zone 2. Each suits a different need.
The watch or its app alone
Pros: no setup, available during the workout. Cons: history across weeks is hard to review in one place, and the zones may not match your own.
Intervals.icu alone
Pros: free for personal use, zones and time in zone per workout, long history. Cons: you read and interpret the charts yourself.
Intervals.icu's own AI connector
Pros: official, works with several AI apps. Cons: needs the Supporter plan ($4 a month on 6 November 2026).
STAS with ChatGPT or Claude
Pros: one STAS account and shared saved context across ChatGPT and Claude, your zones and recent workouts as context, a written explanation and a next-step suggestion. Cons: needs an Intervals.icu account, and the AI cannot judge what the watch did not record.
What to ask the AI
- ✓Update my data, then check my last three easy runs: how much time was in zone 2, and did heart rate drift upward?
- ✓Which of my recent workouts that I planned as easy were above zone 2 for long stretches?
- ✓Based on the last four weeks, how much of my weekly volume was in zone 2?
- ✓My zones may be out of date. What in my recent data suggests I should re-test?
Steps: check zone 2 on your own data
Zones come first. If they are wrong, every later answer is wrong too.
- 1Connect your watch brand to Intervals.icu in Settings → Connections.
- 2Open your sport settings in Intervals.icu and check the heart rate zones. If you are unsure, use the heart rate zone calculator for an estimate.
- 3Open Activities and check that a recent workout shows heart rate and time in zones.
- 4Sign in to STAS with the same Intervals.icu account.
- 5Connect ChatGPT or Claude as shown below and ask about one recent easy workout.
Connect STAS to ChatGPT or Claude
ChatGPT and Claude use the same STAS data. Sign in with the Intervals.icu account that receives your workouts.
ChatGPT
- 1Open chatgpt.com on a computer, in a browser. Turn on Developer mode: Settings → Security and login → Developer mode.
- 2Go to Plugins, select + and choose Add custom MCP server.
- 3In Name, enter STAS. Keep Server URL and paste https://stas.run/api/mcp. In Authentication, choose OAuth.
- 4Tick I understand and want to continue and select Create. When ChatGPT asks you to sign in, use Intervals.icu.
- 5In a chat, type @, select STAS and ask your question.
No Developer mode or Add custom MCP server in your ChatGPT? Use the older option, STAS GPT. It opens as a separate chat, runs on an older ChatGPT model and is no longer updated.
Claude
- 1In Claude, open Customize → Connectors → Add custom connector.
- 2Paste the STAS connector URL: https://stas.run/api/mcp.
- 3Finish the sign-in through Intervals.icu with the same account.
- 4Enable STAS in the chat and ask Claude to update your data first.
Check your next easy run against your real zones
Connect Intervals.icu and ask ChatGPT or Claude how much of it was zone 2.
Connect STASSTAS starts free, no credit card. A custom connector in ChatGPT or Claude depends on your ChatGPT or Claude plan.
How to check that your first workout is visible
Confirm that the AI sees the same heart rate story as your Intervals.icu chart.
- 1In ChatGPT or Claude, write: Update my data, then show my last workout with average heart rate and time in each zone.
- 2Compare the answer with the same workout in Intervals.icu.
- 3If heart rate or zones are missing, fix the watch connection or the zone settings before asking more.
- 4Repeat with an easy workout from last week to see whether the pattern holds.
What the AI can and cannot see
The AI can see
- ✓Heart rate, time in zones and workout detail that reached Intervals.icu.
- ✓Your zones, goals, profile and rules saved in STAS, and recent history.
- ✓Wellness data such as sleep or resting heart rate when your watch sends it.
The AI cannot see
- ✓Heart rate your watch did not record, for example when the optical sensor lost contact. Treat odd spikes with care.
- ✓Why a session felt hard, unless you add a note.
- ✓A lab-tested threshold. The AI works with the zones you have set.
STAS reads only data you approve through Intervals.icu. How STAS handles it is described in the privacy policy.
How STAS differs from a direct connector
An official connector gives an AI access to one service. STAS adds the following on top of your Intervals.icu data.
One STAS account for every watch brand
Add the same STAS connector to ChatGPT and to Claude, and both work with the same saved context.
Context, not raw data
The AI gets a ready summary of load, workouts, wellness, profile, goals and rules, so answers rest on your own history.
The plan returns to the calendar
After you confirm, the plan is written to your calendar, and from there to the watch where the brand supports it.
A convenient interface instead of manual setup
No terminal or API keys. Profile and settings on the site, reports in Telegram, start without a card.
Frequently asked questions
What is a zone 2 training app?
It is any tool that tells you whether your effort stayed in zone 2. Here the check uses your watch heart rate in Intervals.icu and your own zones, and ChatGPT or Claude explain the result.
Which heart rate is zone 2?
It depends on how your zones are set. Check the zones in Intervals.icu, or use the heart rate zone calculator for a starting estimate. This guide does not give a fixed number for everyone.
Can the AI tell me if my zones are wrong?
It can point to signs in your recent data, such as easy sessions that regularly end above zone 2, and suggest a re-test. It cannot measure your threshold itself.
Does it work for cycling and swimming?
It works for any workout that has heart rate and zones in Intervals.icu. Running and cycling are the usual cases; for swimming it depends on whether your watch records heart rate.
What if my watch heart rate is unreliable?
Then the check is unreliable too. Fix the heart rate source first, and expect the AI to mention missing or odd data.
How much does it cost?
STAS starts free, no credit card. A custom connector in ChatGPT or Claude depends on your ChatGPT or Claude plan. Intervals.icu is free for personal use.
Related guides
Stop guessing your zone 2
Connect Intervals.icu, add STAS to ChatGPT or Claude and check your recent easy workouts.
Connect STASSTAS starts free, no credit card. A custom connector in ChatGPT or Claude depends on your ChatGPT or Claude plan.