Threshold intervals: 3 x 10 minutes

Thirty minutes at lactate threshold, split into three blocks so you can hold the pace cleanly for all of it.

How to run it

Warm up 15 minutes easy, run 3 x 10 minutes at threshold with 2 minutes jogging between blocks, then cool down for 10 minutes.

Threshold pace is “comfortably hard”: RPE 7 out of 10, the effort you could race for about an hour. For most runners that sits between 10K and half-marathon pace. You could speak in short sentences but would rather not, and breathing is hard but controlled, never ragged. Daniels calls this T-pace and these broken blocks cruise intervals. The short jog gives just enough relief to hold pace across 30 minutes without the effort sliding down into tempo.

Set the pace from a recent race: roughly 10K pace plus 10 to 15 seconds per kilometer, or your half-marathon pace. If you have no recent race, the race predictor estimates race paces from any recent hard run; the 10-mile or one-hour figure is a good threshold pace. By heart rate expect 85 to 90 percent of max, but heart rate takes 3 to 4 minutes to settle, so let pace or effort lead in the first block.

Run this on flat road or path. Ten minutes is long enough for hills to wreck the average, so on a hilly route hold effort rather than pace and accept slower splits on the climbs.

How to scale it

Easier: 15 min easy, 2 x 10 min at threshold with 2 min jog, 10 min cool down or 15 min easy, 4 x 6 min at threshold with 2 min jog, 10 min cool down.

Harder: 15 min easy, 3 x 12 min at threshold with 2 min jog, 10 min cool down or 15 min easy, 2 x 20 min at threshold with 3 min jog, 10 min cool down.

Aim for 20 to 40 minutes of total threshold time. Add minutes to the blocks before you add a fourth block.

Threshold reps are the Tuesday backbone of the 12-week half marathon training plan, from 3 × 1 km in the beginner version to 3 × 2 km in the intermediate one.

Common mistakes

• Running it at 5K pace. If the last block is a fight, it was a VO2max session, not threshold. The final block should feel like the first, just less fresh.
• Cutting the warm-up short. Threshold pace on cold legs feels far harder than it should and your first split comes out slow.
• Treating the jog as a rest. Two minutes of easy running is enough. If you need to stand still, the pace was wrong.

Let the coach schedule it

When TextFit’s coach puts a session like this in your plan, it counts as a hard day: never next to another one, and no more than two a week (three above eight sessions). It reaches your Garmin or Apple Watch as a structured workout with each block and each jog as its own step and a threshold-pace target worked out from your current fitness, and the watch beeps at every change so you never have to check the clock mid-block. If the day stops working, tell the coach in the chat and it moves or eases the session; every change shows with Undo. Try TextFit free for 14 days on iPhone.