The Power of the 15-Mile Long Run: Transform Your Marathon Training - Lee Grantham

Aug 13, 2025

Intro: This is a quick summary of The Power of the 15-Mile Long Run: Transform Your Marathon Training 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:

The “right miles” matter more than total mileage; a well‑structured 15‑mile long run can dramatically improve marathon performance.
Lee outlines three progressive long‑run formats that target speed, endurance, and mental toughness, with paces expressed as percentages of marathon pace (MP) and converted to minutes per kilometer.
Warm‑up (5‑15 min of walking, dynamic stretches, and accelerations) and a gradual cool‑down are essential for injury‑free, high‑quality sessions.
The workouts are designed to be done on weekends (often Sunday) after a mid‑week interval session.

Workout Example 1 – Progressive 8‑8‑8 km Run (24 km total):

Warm‑up: 5‑10 min walk + light jog + dynamic stretches + a few accelerations.
First 8 km: 20 % slower than marathon pace (≈4 min/km).
Middle 8 km: 10 % slower than marathon pace (≈3:40 min/km).
Final 8 km: Marathon pace (≈3:20 min/km for a 2:20 hr target, adjust accordingly for your goal).
Cool‑down: Gradual jog → static stretching → walking.

Example 2 – Alternating 2 km @ MP + 1 km @ +20 % (8 repeats, 24 km total):

Repeat 8 times:
- 2 km at marathon pace (e.g., 3:20 min/km for a 2:20 target).
- 1 km at 20 % slower (≈4 min/km).
Warm‑up and cool‑down as above. This pattern keeps heart‑rate stable and makes the slower recovery leg feel easy, building comfort at marathon pace.

Example 3 – 5‑15‑5 km Structure (25 km total):

5 km at 4 min/km (easy warm‑up pace).
15 km at marathon pace (3:20 min/km for a 2:20 target).
5 km at marathon pace or slightly faster (e.g., half‑marathon pace) for a stronger finish.
Same warm‑up and cool‑down routine.

Practical Tips:

Use a pacing app to convert the %‑based paces to your target marathon pace.
Keep the warm‑up long enough (10‑20 min) to avoid a shock to the system.
After the run, gradually bring the heart‑rate down with a reverse‑warm‑up, then refuel (e.g., a fruit smoothie) to replenish glycogen.
Aim for 22 quality sessions in 11 weeks (13‑week cycle) and focus on getting 80 % of them right.

Closing Note: Give one of these 15‑mile long‑run formats a try this week, tweak the paces to match your goal, and track it in the Pacing app. You’ll be on your way to a stronger, faster marathon—go for it! 🎉