The long run: how long, at what pace, and how to progress it

The 15% rule

The long run never increases by more than 15% from one week to the next, and steps back one week in four. For a marathon plan it starts at 90 minutes and climbs to 2 h 45; for a half, 60 to 90 minutes; for a 10K, 50 to 75 minutes.

The coach reads your longest run of the last 90 days on Garmin before setting the starting point. It never starts a plan from a long run you have never done.

At what pace

In easy endurance, at 65 to 75% of max HR, for two thirds of the run. The marathon plan adds, from week 6, marathon-pace blocks in the last third: 20 minutes, then 30, then 45.

These blocks at the end of the long run are the marathon's most specific session: running at target pace with already-tired legs. The watch shows the block's pace range and alerts you.

What the coach checks afterwards

In the Garmin activity: actual duration, average heart rate of the first and second third, and cardiac drift. An HR climbing by more than 10% at constant pace signals poorly managed hydration or heat.

• — Never more than 15% longer than the week before.
• — Two thirds in easy endurance, one third at target pace late in the plan.
• — Test your race fuelling during long runs.

The weekly review matches the planned long run against the completed one. A missed long run is the only session the coach has you make up, by shifting it three days at most.

Frequently asked questions