How do you run the Billat 30/30?

What pace do you run the Billat 30/30 at?

Your vVO₂ max pace, the slowest pace that draws your full VO₂ max. You find it with an all-out 6-minute time trial on a separate day, and you work the pace out yourself before the session, outside any app.

On a track, divide the distance you covered in the trial by 12. That's the distance each 30-second rep has to cover. Half the rep pace, the pace for the jogs and the warm-up, means half that distance in the same 30 seconds.

On a watch with no marked distance, hold the trial's average pace as the rep pace. Half the rep pace on a watch is double the minutes per kilometre.

We use a 6-minute trial because 6 minutes is about how long a runner can hold vVO₂ max before stopping, on average, with runner-to-runner variation around 25%. So the trial is about that pace, held for about that long.

Each mistake pushes the number in a known direction. Stop the trial short of your own limit and the pace reads faster than your true vVO₂ max, because a shorter all-out effort is a faster one. Run it well past 6 minutes and the pace reads slower. A 1997 field study found the same direction: its 5-minute running test read significantly faster than the velocity measured on a treadmill.

What should your heart rate do during the 30/30?

Nothing you can steer by. It arrives late in the early reps, then sits near max for the rest of the session without swinging between the hard and easy halves.

A 30-second rep ends before your heart rate has caught up with it. In the Norwegian 4x4, heart rate takes one to two minutes to reach the target inside a rep, and this rep is 30 seconds long.

Once the session is under way, the number stops moving. In Billat's study, eight endurance-trained men running the 30/30 on a track reached 99% of their max heart rate, and the number didn't vary significantly between the hard and easy 30 seconds.

Heart rate also sits above 90% for longer than your oxygen uptake does. When 12 highly trained middle-distance runners ran 24 x 30 seconds at vVO₂ max on a treadmill, with 55% jogs between, their heart rate sat above 90% of max for about 14 of the 24 minutes, and their oxygen uptake above 90% of VO₂ max for about three and a half. The study's authors say the heart-rate figure should be interpreted with caution in ordinary training.

So the number can't set a 30-second rep and can't check one. Read it afterward. A session that went right shows a trace that climbs through the first few reps and then holds near max to the end.

RunBeat's Timed Intervals runs the 30/30 as a custom build, calling every phase by voice for as many rounds as you choose, and the summary shows your heart-rate trace afterward:

Timed Intervals in RunBeat RunBeat calls every work and rest phase, and your Apple Music playlists switch with it.

How many 30/30 repetitions should you run?

16 for a first session, and 20 once every rep covers its distance. We start at 16 because the first session is where you find out whether the pace is right. We stop at 20 because 20 reps is 10 minutes at vVO₂ max.

The stop rule is the same at any count: the first rep that doesn't cover the distance ends the session.

Billat's own runners landed near that ceiling. In her study, eight endurance-trained men on a track, new to interval running, managed 19 reps on average, with a spread of about five either way.

The count matters because the first reps don't do the job. In those eight endurance-trained men on the track, oxygen uptake reached VO₂ max from about the fifth rep and stayed there to the end. The first four reps are the climb, and a short session is mostly climb.

What do you do in the 30 seconds between reps?

Jog, at half the rep pace, for the full 30 seconds.

The jog is Billat's spec. Her 2000 paper suggests the reason: active pauses keep VO₂ max up between the hard reps and stimulate lactate removal, while the runner stays close to a steady lactate level. Once the session was under way, oxygen uptake in her eight endurance-trained men on the track didn't differ between the hard and easy 30 seconds.

In her 2001 review, Billat says 30 seconds appears to be the longest work interval that still holds VO₂ max through the recovery.

Walking the recovery, or standing still, isn't the session Billat ran.

How should you warm up for the Billat 30/30?

15 minutes of easy running, at half the rep pace. That's the warm-up Billat's runners did before the session in her 2000 study.

Finish with 10 minutes easy.

How often should you run the Billat 30/30?

We run it once a week for 4 to 6 weeks, because the easy running around the session is what makes the next one repeatable.

Keep at least 48 hours between the 30/30 and any other hard session, and between it and the long run.