Interval Training for Marathon: Key Sessions by Phase
Interval training for a marathon means one key session a week, not a speed block bolted onto your mileage. Start with hills, short intervals and threshold reps, move to tempo and marathon-pace work as the race gets closer, and keep every other run easy. Put the session on Tuesday or Wednesday, well away from the weekend long run.
Quick answer
- How often: one interval or threshold session a week. With the long run, that makes your two hard days. Never put them on consecutive days.
- Which sessions: threshold reps (4×1 km to 4×2 km), short intervals (5×800 m to 6×1 km), tempo blocks (4–6 km continuous) and marathon-pace reps (2×3 km to 2×5 km).
- In what order: hills, fartlek and short intervals in the base phase, threshold and tempo in the build, marathon pace in the peak and taper.
- How fast: set from your threshold pace, not your goal time. Intervals at 104–110 % of threshold speed, threshold reps at 97–102 %, tempo and marathon pace at 89–94 %, easy runs at 75–82 %.
- How much: the fast part of the session is 1 to 10 km. About 80 % of your running time stays easy.
The four key sessions for marathon runners
| Session | What it does | Typical set | Pace | When |
|---|---|---|---|---|
| Intervals | Raises your aerobic ceiling, so marathon pace uses less of it | 5×800 m to 6×1 km, 400 m jogs | 104–110 % of threshold speed, around 5K race pace | Base, a few times in build and peak |
| Threshold reps | Raises the pace you can hold for a long time | 4×1 km to 4×2 km, 400 m jogs | 97–102 %, the pace you could race for about an hour | Base through taper |
| Tempo | Teaches you to run comfortably hard without a break | 4–6 km continuous | 89–94 % | Build |
| Marathon pace | Grooves race rhythm and lets you rehearse fueling | 2×3 km to 2×5 km, or the last 3–7 km of the long run | Goal marathon pace, inside 89–94 % | Last 10 weeks |
New to structured running? Spend the first weeks on hill repeats and fartlek by effort, then add pace targets once you know your threshold.
Yasso 800s are a benchmark, not a fifth type: 8 to 10 × 800 m, each in the minutes and seconds of your goal marathon in hours and minutes (a 3:30 goal means 3:30 per 800 m), with an equal-time jog between reps. Runner’s World describes the effort as close to threshold rather than all-out 5K, and is clear that one workout doesn’t guarantee the finish time. Use it as a check in the build phase in place of that week’s threshold session.
Paces in your numbers
The bands below are a percentage of your threshold speed (higher is faster). They are the same bands the TextFit coach uses for run targets. The example is a runner with a threshold pace of 5:00 per km (8:03 per mile):
| Run | % of threshold speed | Per km | Per mile |
|---|---|---|---|
| Easy and long | 75–82 % | 6:06–6:40 | 9:49–10:44 |
| Tempo and marathon pace | 89–94 % | 5:19–5:37 | 8:34–9:02 |
| Threshold | 97–102 % | 4:54–5:09 | 7:53–8:18 |
| Intervals | 104–110 % | 4:33–4:48 | 7:19–7:44 |
For this runner, a goal marathon pace inside the tempo band, 5:19 to 5:37 per km, means a 3:44 to 3:57 marathon. If your goal pace sits faster than that band, the goal is ahead of your current fitness. Pace the plan from where you are, and the goal pace usually moves toward you.
Don’t know your threshold pace? The race time predictor estimates race paces from a recent 10K or half marathon, or run a 30-minute solo effort as hard and as even as you can: its average pace is a close estimate. To train by heart rate instead, the heart rate zones calculator gives you the zones, and running training pace explains each zone.
Marathon intervals week by week
This is the Tuesday key session in our 16-week marathon training plan. The long run is on Sunday, and the other runs are easy. Jogs between reps are 400 m.
| Week | Phase | Beginner (4 runs a week) | Intermediate (5 runs a week) |
|---|---|---|---|
| 1 | Base | Fartlek 6×200 m, brisk | Hills 8×200 m |
| 2 | Base | Hills 6×200 m | Threshold 5×1 km |
| 3 | Base | Fartlek 8×200 m, brisk | Intervals 6×800 m |
| 4 | Recovery | Fartlek 5×200 m, brisk | Threshold 4×1 km |
| 5 | Build | Tempo 4 km | Tempo 6 km |
| 6 | Build | Threshold 4×1 km | Threshold 3×2 km |
| 7 | Build | Tempo 5 km | Intervals 5×1 km |
| 8 | Recovery | Threshold 3×1 km | Tempo 5 km |
| 9 | Build | Intervals 5×800 m | Marathon pace 2×4 km |
| 10 | Build | Marathon pace 2×3 km | Threshold 4×2 km |
| 11 | Build | Threshold 3×2 km | Marathon pace 8 km |
| 12 | Recovery | Tempo 4 km | Threshold 4×1 km |
| 13 | Peak | Marathon pace 2×3 km | Intervals 6×1 km |
| 14 | Peak | Intervals 5×1 km | Marathon pace 2×5 km, 1 km jogs |
| 15 | Taper | Marathon pace 5 km | Threshold 3×2 km |
| 16 | Race week | Marathon pace 3 km | Marathon pace 4 km |
Three patterns to copy into any plan:
- The fast part grows slowly. It goes from 1.2 km of brisk running in week 1 to 10 km at marathon pace in week 14, and the type rotates so no single system gets hammered.
- Recovery weeks keep the session, shorter. Beginner week 8 is 3×1 km, one rep fewer than week 6. You keep the rhythm while the week’s volume drops by about a third.
- Marathon pace arrives twice a week late in the block. The Tuesday reps are joined by a marathon-pace finish to the long run: 3–4 km for beginners in weeks 7, 13 and 15, and 3–7 km for intermediate runners. The long run stays mostly easy, with at most a quarter of it faster.
Those long-run finishes are where you rehearse race-day drinking and gels too. The fueling calculator turns your goal pace into carbs per hour, and the sweat rate calculator tells you how much to drink. Training for a half instead? The 12-week half marathon training plan builds on threshold reps, and the half marathon interval guide explains why.
Where the session sits in the week
Week 10 of the intermediate plan, 74 km:
- Monday: rest
- Tuesday: 14 km with 4×2 km at threshold, 400 m jogs
- Wednesday: easy 12 km
- Thursday: easy 10 km
- Friday: rest
- Saturday: easy 8 km
- Sunday: long run 30 km, the last 6 km at marathon pace
That’s two hard days, Tuesday and Sunday, with easy days or rest between them. Moving the key session to Wednesday or Thursday works. Saturday doesn’t, because it would sit right before the long run. Weekly volume rises by no more than 10 %, and every fourth week is a recovery week with 30–40 % less running. The plan pages check those rules on every week of the table.
How to run the reps
- Run the first rep no faster than the last. Aim for even splits inside the band. If rep one is your fastest by a wide margin, you started too hard.
- Jog the recoveries. A 400 m jog takes 2 to 3 minutes. Keep moving.
- Change one thing at a time. Add a rep or lengthen the reps, then hold that version for a week or two.
- Stop before your form breaks. One rep fewer beats a fade.
- Missed the session? Skip it rather than moving it next to the long run. The next one is a week away.
For more threshold variations, see lactate threshold workouts.
Your marathon intervals on your watch with TextFit
TextFit is an AI coach for iPhone and Android that builds the marathon block around your race date, the days you can train and your current fitness in your own words, like “half in 1:52 in May, 4 runs a week”. It plans each key session by the rules above (at most two hard days, never back to back, three build weeks then a recovery week, a 2-week taper), and a validator checks every week against them before you see it.
Every session goes to your Garmin or Apple Watch as a structured workout with paces in your own numbers, pushed automatically for the next 7 days. Your watch beeps through the reps and recoveries. Completed runs come back from Garmin or Apple Health, and the coach compares each one with the plan, including how many reps stayed inside the target band. When the week changes, write “move Tuesday’s intervals, I’m travelling” in the coach chat. The coach rebuilds the week, and every change shows with Undo.
See a full example week on the AI running coach page, or read how the coach builds a week and how it works with Garmin and Apple Watch. Comparing apps first? Here are the best marathon training apps side by side.
14 days free, then $14.99/month or $99.99/year: start your 14-day free trial.
FAQ
How often should marathon runners do interval training?
Once a week. Together with the long run, that makes two hard days, which is enough for most amateur marathoners. Keep the rest of the week easy.
Are intervals worth it for a 3:30 to 4:30 marathoner?
Yes, in small doses. A higher threshold makes marathon pace a smaller share of what you can sustain, so it feels easier for longer. For most runners in that range, the key sessions are mainly threshold, tempo and marathon pace, with short intervals a few times in the block.
Should intervals come early or late in marathon training?
Both, with different jobs. Hills, fartlek, short intervals and threshold reps build the base. From about 10 weeks out, marathon pace joins them, first as the finish of the long run, then as Tuesday reps. The last weeks are mostly marathon pace and threshold.
What pace should marathon intervals be?
Set it from your threshold pace: intervals at 104–110 % of threshold speed, threshold reps at 97–102 % and tempo or marathon pace at 89–94 %. With a 5:00 per km threshold, that’s 4:33–4:48, 4:54–5:09 and 5:19–5:37 per km.
Can beginners do interval training for a marathon?
Yes, by effort first. The beginner version of the 16-week plan runs fartlek and 200 m hill reps for the first 4 weeks. Paced tempo and threshold work starts in week 5, with one key session a week throughout.
Do Yasso 800s predict your marathon time?
Roughly. Running 8 to 10 × 800 m in the minutes and seconds of your goal hours and minutes shows pacing discipline and aerobic fitness. But long-run durability and fueling decide the last 10 km, so treat the result as a check, not a promise.
Should I do intervals during the marathon taper?
Yes, shorter. The key session stays in the last 2 weeks while volume drops: 5 km at marathon pace or 3×2 km at threshold in week 15, then 3 to 4 km at marathon pace on the Tuesday of race week. It keeps the rhythm without adding fatigue.