Rennes Green Marathon 2027: your 12-week plan on Garmin, set to race day once it's announced
The 2026 edition was run on Sunday, October 18; the next one is expected in October 2027, date not announced yet. For a mid- or late-October race, the 12-week plan starts on a Monday in late July or early August. Once the date is out, Running Workout sets the plan to it in two minutes, and your AI assistant then sends each week's workouts to your watch.
Last updated: October 27, 2026
Marathon Vert Rennes Groupe Interaction
October 2027, date to be confirmed
- Distance
- 26.2 mi
- Course
- 2 loops
- Elevation gain
- 110 m (360 ft)
Try it now
Ask your assistant
Once your Garmin is connected, paste one of these into Claude or ChatGPT:
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« Analyze my Rennes Green Marathon from October 18: did I run the second loop as fast as the first? »
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« I'm aiming for 3:30 at the Rennes Green Marathon in October 2027: what target paces per mile for marathon pace, threshold and long runs? »
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« I'm getting back to running after Rennes: send a 40-minute easy run to my watch for Thursday. »
Free to start · 4 workouts a month sent to your watch
Two 100% urban loops
In 2026, the start was on the Mail François-Mitterrand and the finish on the Esplanade Charles-de-Gaulle, in central Rennes: two loops through the city, 110 m (360 ft) of total elevation gain according to the organizers, on a measured course with the French athletics federation's international Gold label.
A two-loop course splits naturally into two halves: a good checkpoint to confirm your start wasn't too fast. The organizers will publish the 2027 course; check it before setting your paces.
The autumn preparation
Mid- or late October depending on the year (October 18 in 2026): the 12-week plan starts in late July or early August, the 16-week one in late June or early July. The peak load falls in September, when Brittany's weather suits long runs.
The AI coach follows every week what you actually ran on Garmin, compares it with the plan and decides: next week as is, lightened, or an assimilation week brought forward if the load climbs too fast.
Pacing and the Breton wind
The westerly wind can pick up on open stretches. The instruction: target pace when sheltered, low end of the range into the wind, never chasing lost time. On a two-loop course, the first loop is your test: if it went faster than planned, ease off on the second.
- July-August: volume and a long run up to 2 h.
- September: 12-to-16 km marathon-pace blocks, 2 h 45 long runs.
- October: taper, fresh legs for the finish line.
Schedule the plan's "Race" session on the watch: first three kilometres at target pace plus 10 seconds, target pace afterwards, and the last two kilometres in the centre by feel.
Frequently asked questions
When is the 2027 Rennes Green Marathon?
The 2027 date hasn't been announced yet; the 2026 edition was run on Sunday, October 18. Wait for the official date before entering it in your plan.
Is the course really fast?
Yes: the organizers describe it as very fast, with 110 m (360 ft) of climbing in 2026 over two city loops. Wind can play a part on the open stretches.
What does "green marathon" mean?
With the Fondation Yves Rocher, the organizers plant one tree for every 2 km (1.2 miles) run, which makes 21 trees per marathon runner. A cheaper "Dossard Vert" (green bib) also lets you give up the T-shirt, medal and finish-line goodies.
Is Running Workout free?
Free to start: Garmin connection, plans, reading your activities and 4 workouts a month sent to your watch. Running Workout Pro (€4.90 a month or €35 a year, no commitment) removes the limit.
Marathon Vert Rennes Groupe Interaction
Ready to prepare for your marathon?
The plan is set to that date; your assistant does the rest, week after week.