How FAST are my thresholds? Training for a SUB 2:20 Marathon! - The Welsh Runner

Aug 13, 2025

Intro

This is a quick summary of How FAST are my thresholds? Training for a SUB 2:20 Marathon! 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

The runner performed a 4‑minute step lactate test on a treadmill, taking a quick lactate sample during a 1‑minute break between steps.
LT1 appeared at ≈16.5 km/h (about 5:50 min/mile). This is the pace where lactate first rises above baseline.
LT2 showed up at ≈18.5 km/h (about 5:13‑5:15 min/mile). Above this pace lactate spikes dramatically and carbohydrate reliance dominates.
Corresponding heart‑rate zones were roughly 160 bpm for LT1 and mid‑170 bpm for LT2.
Treadmill paces are slightly faster than outdoor equivalents, so expect a small adjustment when you move outside.
The test can be repeated early in a training block and again closer to the marathon to track progress.

Workout Example

Gym Threshold Session (based on the test results)

Warm‑up – 10 min easy jog.
2 × 10 min at a sub‑LT1 pace (just a shade slower than 5:50 min/mile). Keep heart‑rate around the LT1 zone.
10 × 3 min at a just‑below‑LT2 pace (≈5:13 min/mile). Aim for heart‑rate in the mid‑170 bpm range.
Cool‑down – 10 min easy jog.

If you’re short on time, you can truncate the 10 × 3 min set to a single pyramid: 3 min, 2 min, 1 min at LT2 pace, then back up (1‑2‑3 min), keeping effort strong on the short reps.

Long Run Example (outside the gym):

2‑hour run at ≈6:40–6:50 min/mile (roughly LT1‑LT2 zone) with the last 3 miles a little faster if legs feel good. This mirrors the runner’s weekend long run with Andy.

Practical Tips

Use 4‑minute steps for a clearer lactate curve; shorter (3‑min) steps work but may be noisier.
Keep the 1‑minute lactate sampling window brief to limit fatigue.
Record both pace and heart‑rate; they’ll help you translate treadmill numbers to road runs.
Adjust treadmill paces down 5–10 seconds per mile when training outdoors.
Re‑test every 4–6 weeks to see if LT1/LT2 have shifted as fitness improves.
Plug the paces into your Pacing app and customise them to your own recent runs.

Closing Note

Give these threshold‑based workouts a try and watch how your marathon speed improves. Feel free to tweak the intervals to match your current fitness, and don’t forget to log the paces in the Pacing app for easy tracking. Happy training, and be sure to watch the full video for the deeper dive!