How to Transition from 5K to 10K Training Without Sacrificing Speed - Lee Grantham

Aug 13, 2025

Ready to level up from the 5K to the 10K without losing your hard-earned speed? We’re breaking down elite runner Lee Grantham’s simple and effective strategy from his recent video. Be sure to check out the full video for all the details, and read on for a workout you can try today.

Key Points:

The biggest mistake runners make is doubling their entire weekly volume. Instead, Grantham advises you to increase your interval session volume gradually. This targeted approach is the foundation of smart progression, a concept central to Mastering Interval Training: Science-Backed Workouts and How a Smart App Can Personalize Them.
Keep your long-run distance roughly the same. The real magic happens by focusing on more 5K-style work at your new 10K pace.
To make the increased distance manageable, use slightly slower paces for your initial 10K intervals (e.g., 3:06–3:10 min/km). This is a key race-day tactic and part of a solid training plan, which you can explore further in our complete guide to Mastering the 10K: Proven Training Plans, Pace Strategies, and How a Smart App Can Elevate Your Performance.
Remember, consistency over weeks and months matters far more than a single, brutal week of extra miles.

Workout Example:

Base 5K interval: Start with a workout you know well, like 6 × 1 km at your current 5K pace (e.g., 3:00 min/km). This session should feel familiar if you’ve been focused on Mastering 5K Speed: Proven Interval Strategies to Cut Minutes off Your Time.
Transition week: Begin the transition by increasing the total interval distance to 6.5 km (e.g., 6 × 1 km + 1 × 0.5 km) while keeping the same 5K pace.
Progressive weeks: Each week, add another 0.5 km to your interval session until you reach 8 km total (e.g., 8 × 1 km). As the volume increases, you can either hold your 5K pace or, as Grantham suggests, back off slightly to your target 10K pace (e.g., 3:06–3:10 min/km) to build endurance.
Optional mix: To keep your top-end speed sharp, sprinkle in a few 5K-pace repeats (e.g., 2 × 1 km at 2:50 min/km) within the longer session. The bulk of the volume remains at 10K pace, but this keeps your legs firing.

Closing Note:

Try this gradual interval build-up this week. Be sure to adjust the paces to fit your current fitness, and watch your 10K confidence soar. You can always customize the distances and paces in the Pacing app to suit your own goals. Happy running