CyclingVO2maxIntermediate 60 min

Rønnestad 30/15 intervals (3 × 13)

Rønnestad 30/15 intervals: three sets of 13 × 30 seconds at 118–130% of FTP, with 15 seconds easy between each. Nearly 20 minutes of work in an hour-long session. One of the most thoroughly studied VO₂max formats in trained cyclists.

Written by Pierre Halloo · Updated 25 October 2026

Session profile81 blocks

At a glance

Duration: 60 min
Main target: 118–130%FTP6 Z6 · Anaerobic
Time at target: 20 min
Estimated load: 71
Structure: 3 × (13 × 30″ at 118–130% FTP, 15″ recovery), 3′ between sets
Level: Intermediate
Equipment: Power meter · Smart trainer

The session in detail

FTP

Time in zone

Z121 min
Z219 min
Z620 min

What the targets mean

The session's targets, in watts for three reference FTPs
Target	Zone	Time	FTP 200 W	FTP 250 W	FTP 300 W
118–130%	6Anaerobic	20 min	236–260 W	295–325 W	354–390 W
55–65%	2Endurance	9 min	110–130 W	138–163 W	165–195 W
45–55%	1Recovery	11 min	90–110 W	113–138 W	135–165 W

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What this session is for

30/15s build your VO₂max and maximal aerobic power. The trick is in the 15-second recoveries: too short for your oxygen uptake to drop, but long enough to give your legs a little relief. Each 9 min 30 set behaves like one long effort at varying power, ridden harder than you could manage continuously.

Bent Rønnestad's group in Norway put it to the test in competitive cyclists, then in elite riders: over several weeks, 30/15s beat 4 × 5 minutes on VO₂max and maximal aerobic power. The name 'Rønnestad intervals' is common usage, not one the author gave them.

Who it's for

Intermediate to advanced riders already used to VO₂max work, such as 30/30s. The studies were on trained competitive cyclists: it's a demanding session, not one for discovering intensity. You need a recently measured FTP.

When to do it

One or two VO₂max sessions a week is a common guideline, with at least one easy day between hard sessions. In the 2015 study, riders did two a week for 10 weeks. Avoid the day before a long ride or a race. To ease in, start with two sets, then move to three.

How to do it

Warm-up
15 min
5′ at 45–55% FTP + 5′ at 56–65% FTP + 5′ at 66–75% FTP
15 minutes building from 45 to 75% of FTP, in 5-minute steps. On a smart trainer, switch to resistance or slope mode: in ERG, the trainer can't keep up with a change every 15 to 30 seconds.
Main set
35 min
3 × (13 × 30″ at 118–130% FTP, 15″ recovery), 3′ between sets
Three sets of 13 × 30 seconds at 118–130% of FTP, or 295 to 325 W for an FTP of 250 W, each followed by 15 seconds at 55–65%, or 138 to 163 W, with 3 easy minutes between sets. In the studies, the 30 seconds are ridden at the hardest effort you can sustain for the whole session, not a fixed power: the range is a starting point. Aim for even power across every rep rather than a flying start, and keep pedalling through the 15 seconds.
Cool-down
10 min
10′ at 40–55% FTP
10 very easy minutes at 40–55% of FTP. Compare the power of your first and last sets: if the last dropped noticeably, start lower next time; if it held steady, you can aim for the top of the range.

How it should feel

The first set feels almost reasonable. By the second, the 15-second recoveries seem to shrink: barely time to loosen your grip on the bars. The last reps of the third set are very hard, legs burning and breathing maxed out. Guide: 9 out of 10.

Common mistakes

Blowing it on the first set

With only 15 seconds of recovery, a first set that's too fast costs you over the next two. A 30/15 session is judged on the third set: it should come out at the same power as the first.

Freewheeling the 15 seconds

The recovery is pedalled, at around half your effort power. Coast and every restart costs more, and you lose the rhythm that turns each set into one long continuous effort.

Staying in ERG mode

The trainer takes several seconds to switch targets: over a 15-second recovery it barely gets there. Resistance or slope mode lets you pace to the rhythm of the session.

Treating the range as fixed

The studies don't prescribe a percentage but the hardest sustainable effort. If 118% feels easy in the third set, go higher next time; if it's out of reach, come down.

When to skip it

Before you start

A recently measured FTP.
Several VO₂max sessions already done, short or long.

Skip it if

You're very tired, or a long ride or race is planned for the next day.
You have doubts about your health: get medical advice before near-maximal efforts.

Origin and evidence

Level of evidence

Good evidenceLevel 4 of 5

Rønnestad and colleagues (Scand J Med Sci Sports 2015), 20 competitive cyclists, 2 sessions a week for 10 weeks: VO₂max +8.7% with 30/15s, against +2.6% with 4 × 5 minutes at equal effort, with better performance over 30 seconds, 5 minutes and 40 minutes. In 2020, in elite cyclists (VO₂max 73 mL/kg/min), 9 sessions in 3 weeks: maximal aerobic power +3.7%, against −0.3%. Caveat: when both formats are ridden at a freely chosen maximal effort, the advantage in time near VO₂max disappears within a single session. In the studies, the 30 seconds are ridden at the hardest sustainable effort, with recovery at about half the effort power (secondary analysis); a 2023 study used a fixed version at 118% and 60% of FTP. The 118–130% range, the intensity of the 3 minutes between sets, which the sources don't specify, the warm-up and the cool-down are Wattson choices. Bottom line: good evidence.

Sources

Rønnestad B. R. et al., Scand J Med Sci Sports 2015
Rønnestad B. R. et al., Scand J Med Sci Sports 2020
Rønnestad B. R., Hansen J., J Strength Cond Res 2016

Frequently asked questions

What power should I ride Rønnestad 30/15s at?

Here, at 118–130% of FTP: 236 to 260 W for an FTP of 200 W, 295 to 325 W for 250 W, 354 to 390 W for 300 W, with recoveries at 55–65%. In the studies, the intensity is the hardest effort you can sustain over all three sets: adjust within the range based on your third set.

Why do 30/15s work better than 4 × 5 minutes?

The 15-second recoveries don't let your oxygen uptake fall, but they do ease your legs a little: you ride harder than you could continuously while staying close to your VO₂max. One caveat: when both formats are ridden at a freely chosen maximal effort, the advantage within a single session disappears.

30/15 or 30/30: what's the difference?

The recovery. In a 30/30 it lasts as long as the effort, and your breathing has time to settle a little. In a 30/15 it's half as long: the set becomes one long effort at varying power. 30/30s are for getting started, 30/15s for going further.

How many 30/15 sessions a week?

One, sometimes two, with at least one easy day between hard sessions: a common guideline. The two sessions a week in the 2015 study were part of a 10-week protocol, in competitive cyclists.

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