Sub-5 Mile at age 40? My FUN Birthday Challenge as a Master's Runner - Seth James DeMoor

Aug 13, 2025

Intro

This is a quick summary of “Sub-5 Mile at age 40? My FUN Birthday Challenge as a Master’s Runner” from Seth James DeMoor. It’s a fun watch — we’re breaking it down so you can try the birthday‑mile workout today. Be sure to check out the full video for all the details.

Key Points

Birthday Mile: run a single mile as close to your birthday as possible and treat it as a “birthday‑mile PR” rather than a lifetime PR.
Goal: sub‑4:38 mile at age 40, using the track for a race‑like effort.
Quarterly Tradition: plan a birthday‑mile every quarter (July, August, September) to keep speed work in check.
Training Approach: reduce weekly mileage to 80‑100 miles and focus on track speed work (200 m, 400 m, 800 m intervals) to build speed for the mile.
Pacing Insight: you can’t run a fast 1600 m if you’re not fast at 800 m, 400 m, 200 m—use progressive intervals to improve.

Workout Example

Warm‑up – easy jog + dynamic stretches, put on spikes.
Mile Time Trial
- Aim for sub‑4:38 (≈68‑69 sec per 400 m). Aim for 68 sec per 400 m (first 400 m), 70‑71 sec on the second, and try to hold it through the third lap.
- Use a track or flat loop; record split times.
Post‑run – celebrate with cake, then log the time in your Pacing app and adjust future paces.

Practical Tips

Schedule the birthday mile in your calendar and training log so you never miss a quarter‑year check‑in.
Keep weekly mileage low (80‑100 mi) to prioritize speed work.
Use interval progression (200 m → 400 m → 800 m) to build the speed needed for a fast mile.
Use the Pacing app to set target splits and adjust for your own pace.

Closing Note

Give the birthday‑mile a try this month, tweak the splits to match your current fitness, and log it in the Pacing app. You’ll see progress, have fun, and keep your speed sharp for the next decade. Happy running!