How to Break 3 Hours in a Marathon: 15K Strategy - Lee Grantham

Aug 13, 2025

Intro

This is a quick summary of How to Break 3 Hours in a Marathon: 15K Strategy from Lee Grantham. It’s a great watch — we’re breaking it down so you can try the workout today. Be sure to check out the full video for all the details.

Key Points

Your lactate threshold pace (the fastest pace you can sustain for about an hour) is the biggest factor for a sub‑3‑hour marathon.
Running 15 km in ≤ 1 hour (≈ 4:00 min/km or 6:26 min/mi) or a 10‑mile race at the same pace is a reliable benchmark.
Use 10‑mile races 4‑5 weeks before marathon day for a low‑fatigue, high‑feedback test.
Blend threshold work, marathon‑pace runs, long runs with marathon‑pace sections, faster‑than‑threshold intervals, and speed work to push the threshold higher while maintaining marathon‑pace endurance.

Workout Example

Session 1 – Lactate Threshold Intervals

3 × 5 km at 4:00 min/km (6:26 min/mi) with 60 s jog/rest between repeats. (If you’re newer, start with 3 × 3 km and build up.)

Session 2 – Marathon‑Pace Run

15 km total: run the entire distance at marathon goal pace of 4:15 min/km (6:50 min/mi). This gives ~10 % slower than the 15 km target, reinforcing the feel of marathon effort.

Session 3 – Long Run with Marathon‑Pace Finish

Example: 20 km easy, then 10 km at 4:15 min/km, finish with 5 km easy. The marathon‑pace block trains you to finish strong while preserving overall mileage.

Session 4 – Above‑Threshold Repeats

6 × 1 km at 3:45 min/km (≈ 6:00 min/mi) with 60 s recovery. This pushes the threshold higher; allow extra recovery (fuel and shake) after the set.

Session 5 – Speed Work

8‑20 × 400 m at 3:30‑3:35 min/km (≈ 5:35 min/mi), about 10 % faster than threshold. Start with 8‑10 reps and build to 15‑20 as fitness improves.

Closing Note

Give these sessions a try, adjust the paces to match your current fitness, and track everything in the Pacing app so you can fine‑tune the workout to your own numbers. Consistency will bring you closer to that 15 km = 1 hour benchmark and the sub‑3‑hour marathon goal—go for it!