Marathon training plan, 12 to 16 weeks, on Garmin
Running Workout's marathon plan runs between 12 and 16 weeks — the length adjusts automatically to how much time you have before race day —, with 3 to 7 sessions per week depending on your schedule, and progressively builds marathon race pace up to long runs of two and a half hours. Every session is written by your AI coach and pushed straight to your Garmin watch.
Last updated: 2026-09-19
A 12-to-16-week plan, five phases
The plan's length depends on how much time you have before your race date: with 12 weeks of lead time, it starts directly at the base phase; with more, it first adds up to 4 lead-in weeks that get you back into a regular running rhythm.
Next comes the core of the plan, unchanged regardless of its total length: a base phase (weeks 1 to 3) that builds volume and wakes up your threshold, then a development phase (weeks 4 to 7) where marathon pace enters the picture and long runs stretch out.
Next comes the race-specific phase (weeks 8 to 10), with long blocks at marathon pace and runs of two hours or more, followed by two taper weeks to arrive fresh on race day.
| Phase | Weeks | Goal |
|---|---|---|
| Lead-in | 0 to 4 (depending on lead time) | Get back into a regular running rhythm before the plan starts |
| Base | 1 to 3 | Build volume, wake up the threshold |
| Development | 4 to 7 | Marathon pace enters, long runs stretch out |
| Race-specific | 8 to 10 | Long blocks at marathon pace, runs of 2h+ |
| Taper | 11 and 12 | Two weeks to arrive fresh |
Sessions built around your own VMA, not an average
Each week combines two quality sessions and a long run, topped up with easy runs. The balance shifts as the plan progresses: more VMA work early on, more marathon pace as race day nears.
- VMA work, in short repeats of 30 seconds to 3 minutes, to push back the aerobic ceiling the whole plan builds on.
- Threshold work, in 8-to-15-minute blocks, for the best return on effort for sustained intensity.
- Marathon race pace, in repeats growing from 2 to 10 km, to get the body — and the mind — used to race-day rhythm.
- The long run, building up to two and a half hours, with a marathon-pace finish from the development phase onward.
These targets are never fixed: your AI coach converts them into a real pace automatically, from your VMA as measured or declared in the app.
Long runs, up to two and a half hours
The long run is the backbone of a marathon plan. It climbs progressively to two and a half hours, with a marathon-pace finish as soon as volume allows — the best way to teach your body to hold that pace once tired.
In the peak week, a roughly 30 km distance-based alternative is offered instead of the time-based version, whenever it stays under 2h50 at your pace — a full dress rehearsal, fueling included, before race day.
That same peak week also carries the plan's key session: 2 times 8 km at marathon pace, 16 km total at race pace — the biggest specific block before tapering.
How to start this marathon plan
You pick your marathon date and weekly session count, from 3 to 7, on the app's Plan screen. Your AI coach — Claude, ChatGPT or Gemini connected via MCP — then reviews these settings with you, and builds and pushes the sessions to your Garmin watch, week by week.
The plan stays editable at any time: date, variant or stopping it all happen from the same screen. The connection guide explains how to link your AI assistant the first time.
Frequently asked questions
How long is Running Workout's marathon plan?
Between 12 and 16 weeks depending on how much time you have before your race, across five phases: lead-in (optional, up to 4 weeks), base, development, race-specific and taper.
Does the plan adapt to my level and availability?
Yes: you choose between 3 and 7 sessions a week, and target paces — threshold, VMA, marathon pace — are calculated automatically from your VMA.
Are sessions sent automatically to my Garmin watch?
Yes. Once the plan is confirmed with your AI coach, sessions are built and pushed to your Garmin Connect calendar week by week.
Can I change or stop the plan partway through?
Yes, from the Plan screen: you can change the race date, the variant, or stop the plan — sessions already sent to Garmin stay in place.
How is marathon pace calculated if I have no target time?
It's graded from your VMA: under 14 km/h, it targets 75% of your VMA (beginner or finisher profile); between 14 and 17 km/h, 79% (trained profile); above 17 km/h, 82% (strong level). If you enter a target time for your marathon, it replaces this grading directly.
What changes between 3 and 7 sessions a week?
The two quality sessions and the long run stay identical no matter what you pick — only easy runs are added on top of that base: a first one from 4 sessions, a second from 5, a third from 6, a fourth at 7.
How is the plan's exact length chosen?
Automatically, from the lead time between today and your race date: exactly 12 weeks adds no lead-in weeks, 16 weeks or more adds the full 4, and anything in between adds a matching share — there's nothing for you to choose yourself.
Ready to prepare for your marathon?
Pick your race date and weekly session count: your AI coach builds the plan and pushes it to your Garmin.
Start the marathon plan