I ran sub 5 minute/mile at 20 miles into a long run. LONGEST run of the block. LONDON MARATHON 2023 - The Welsh Runner

Aug 13, 2025

Intro

This is a quick summary of “I ran sub 5 minute/mile at 20 miles into a long run. LONGEST run of the block. LONDON MARATHON 2023” from The Welsh Runner. 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

80‑minute warm‑up at a comfortable steady pace (roughly marathon‑pace or slower) to get the legs moving before the faster work.
Three‑minute “on” intervals (hard effort) followed by three‑minute “off” (easy) repeated several times toward the end of the run. This burns glycogen quickly and boosts confidence.
Sub‑5‑minute/mile effort was hit at about mile 20, showing that you can practice race‑pace effort deep into a long run.
Finish with a 30‑minute steady cooldown to flush out metabolites and aid recovery.

Workout Example

Warm‑up: 80 min easy/steady run (≈ 10‑12 mph or comfortable conversation pace).
Main set: After the warm‑up, run 3 minutes at a hard “on” pace (aim for a pace a few seconds faster than your goal marathon pace – around 4:45‑5:00 min/mi) followed by 3 minutes easy “off” (recovery jog).
- Repeat this 3‑4 times (the video shows 8 reps total, but you can adjust).
- Aim to hit a sub‑5‑minute/mile effort on the final “on” segment around mile 20.
Cooldown: 30 min steady easy run (slow jog, 8‑9 min/mi or slower).

Closing Note

Give this long‑run with late‑run speed work a try in your next training block—adjust the paces to match your own marathon goal using the Pacing app. You’ll build endurance, sharpen race‑pace confidence, and be ready to hit those sub‑5‑minute miles on race day! 🚀