AI running coach prompt

On 5 September 2026, six weeks before my first half marathon, I gave this prompt to my AI coach (Claude), which had access to my real Garmin data. I asked it not to flatter me, and it didn’t.

Before you use it

This prompt calls Garmin tools by name (get_activities, get_hrv_trend and so on), so it only works when your AI assistant is connected to your Garmin account. I used the open-source garmin_mcp server, connected to Claude Desktop.

If you paste it into a plain chat with no Garmin connection, the assistant won’t be able to pull your data. The prompt tells it to say so rather than guess.

To adapt it: change the race name, race date, today’s date, weeks out and distance to match your own race.

The prompt

You are my running coach. I'm running the Vedanta Delhi Half Marathon on Sunday 18 October 2026 — my first 21k. Today is 5 September, so 6 weeks out. Pull my Garmin data and assess where I actually stand:

1. get_activities for the last 16 weeks. For each running week, give me: total km, number of runs, longest run, and average pace.
2. get_training_load_trend for 8 weeks — CTL, ATL, TSB.
3. get_hrv_trend and get_sleep_summary_range for 4 weeks.
4. get_training_status and get_vo2max_trend.
5. get_race_predictions.
6. get_activity plus get_activity_splits on my three longest recent runs — check HR drift from first half to second half (aerobic decoupling).

Then tell me, bluntly:

A. VERDICT — pick one and justify with numbers:
   - Ready to race a time goal
   - Ready to finish comfortably
   - Ready to finish with a run/walk strategy
   - Not ready; 21k on 18 Oct carries real injury risk

B. THE NUMBERS THAT DECIDE IT — my longest run to date, my 4-week average weekly volume, my consistency (runs/week), and how long I've been running consistently. Compare each against what a first-time half marathoner needs 6 weeks out.

C. RISK FLAGS — ramp rate above 10%/week, HRV trending down, chronic sleep debt, aerobic decoupling above 5%, any TSB below -30.

D. REALISTIC FINISH TIME — a range, not a point estimate, with the assumptions behind it.

Rules: use only real data from the tools. If a metric is missing or the history is too short, say so rather than estimating. Don't flatter me — if the honest answer is that I should target a 10k instead, say that.

What I got back

Ready to finish with a run/walk strategy. You are at the bottom of this band, not the top.

Six weeks later, I finished in 3:02:13.

• Read the full readiness assessment and 6-week plan (PDF)
• Read the post-race report card (PDF)

Glossary

Term	What it means
CTL	Chronic Training Load: your fitness, roughly a 6-week rolling average of training stress
ATL	Acute Training Load: your fatigue, roughly a 7-day rolling average
TSB	Training Stress Balance (CTL − ATL): your form. Very negative means overreached
HRV	Heart Rate Variability: a recovery signal. A falling trend can mean accumulated fatigue
Aerobic decoupling	How much your heart rate drifts upward in the second half of a steady run. Under 5% suggests a solid aerobic base