Do THIS before trying DOUBLE THRESHOLD days - The Welsh Runner

Aug 13, 2025

Intro: This is a quick summary of “Do THIS before trying DOUBLE THRESHOLD days” 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:

Double‑run days are a proven way to boost weekly volume while still managing fatigue. 
Start with a controlled Zone 2 (upper Zone 2, just below LT1) morning session to rebuild aerobic capacity. 
Follow with a short, high‑intensity threshold session in the afternoon: 400 m repeats at threshold pace with very brief (≈30 s) standing recoveries. 
Keep heart‑rate below ~175 bpm and lactate under 4 mmol/L to avoid over‑cooking the workout. 
Use a COROS watch and HR strap for real‑time pacing and a lactate test post‑run to verify intensity.

Workout Example:

Morning (Zone 2) – 3 × 10 min runs at upper Zone 2 with 2 min easy jog between sets (total ~30 min). 
Afternoon (Threshold) – 20–25 × 400 m repeats at threshold pace (≈5:00–5:30 / mile when fit) with 30 s standing recovery. Stop early if heart‑rate spikes or calves feel tight. 
Cool‑down – easy jog or walk until heart‑rate returns to a comfortable zone; optional lactate check after the session.

Closing Note: Give this double‑run day a try and adjust the paces to match your own fitness using the Pacing app – you’ll feel stronger and more confident heading into longer runs and race weeks. Happy running!