30/30 intervals
Thirty seconds hard, thirty seconds easy, repeated — accumulating time near VO₂max without the strain of long reps.
Also called: Billat 30-30, short-short intervals.
Billat's finding was that alternating 30 seconds at vVO₂max with 30 seconds of jogging keeps oxygen uptake high across the whole set while blood lactate stays much lower than continuous reps would produce. In practice that means a large dose of aerobic-power work that leaves you far less wrecked than 5 × 1000 m. Useful for runners returning to intensity, and for slotting quality into a heavy week.
The session
Shown at a 4:00 marathon reference — 45 min total, about 6.9 km, including 9 min of quality work.
Warm-up
- 12 min easy (6:43–7:24/km)
- 4 × 20 s strides, jog back between
Main set
- 8 × 30 s @ 4:36/km (3K), 30 s jog between
- 3 min easy jog / walk between sets
- 8 × 30 s @ 4:36/km (3K), 30 s jog between
Cool-down
- 10 min easy (6:43–7:24/km)
Why this session works
30 s at ~vVO₂max with 30 s jogs — Billat’s protocol accumulates long durations at maximal oxygen uptake with far less strain than continuous reps. Ideal when you want the stimulus without the hammering.
Source: Billat et al. 2000. Training phase: build.
Run it at your own paces
Open the workout generator and enter a recent race time — every rep length, recovery and target pace is recalculated for your fitness, and the session exports to .fit for a Garmin watch.
Frequently asked questions
What is a 30/30 intervals?
Thirty seconds hard, thirty seconds easy, repeated — accumulating time near VO₂max without the strain of long reps. Billat's finding was that alternating 30 seconds at vVO₂max with 30 seconds of jogging keeps oxygen uptake high across the whole set while blood lactate stays much lower than continuous reps would produce.
How long is this session?
At a 4:00 marathon reference it comes to 45 min and about 6.9 km, of which 9 min is prescribed quality work. The generator scales both to your own paces, so a faster runner covers more ground in the same time.
Who is this workout for?
It is written for the build phase of a marathon build. The distances shown suit a 4:00 marathoner; enter your own recent race time in the generator and every rep length and target pace is recalculated for you.
More vo₂max intervals sessions
- VO₂max intervals — Repeats of two to five minutes at around the pace you could hold flat out for ten minutes, with equal or slightly shorter recoveries.
- Cutdown intervals — Intervals that get shorter and faster as the session goes on.
- Pyramid intervals — Reps that climb in length to a peak and then come back down.
- Hill repeats — VO₂max-effort intervals run uphill, with the gradient supplying the resistance and capping the impact.