CyclingVO2maxAdvanced 62 min

Fast-start VO₂max intervals on the bike (5 × 5 min)

Fast-start VO₂max intervals: five 5-minute efforts, each opening with 2 minutes at 120–130% of FTP and finishing with 3 minutes at 104–110%, with 3 minutes' recovery. A 62-minute session for advanced riders already used to VO₂max work.

Written by Pierre Halloo · Updated 25 October 2026

Session profile18 blocks

At a glance

Duration: 62 min
Main target: 104–130%FTP6 Z6 · Anaerobic
Time at target: 25 min
Estimated load: 74
Structure: 5 × (2′ at 120–130% FTP + 3′ at 104–110% FTP + 3′ at 50–60% FTP)
Level: Advanced
Equipment: Power meter · Smart trainer

The session in detail

FTP

Time in zone

Z127 min
Z210 min
Z515 min
Z610 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
120–130%	6Anaerobic	10 min	240–260 W	300–325 W	360–390 W
104–110%	5VO2 Max	15 min	208–220 W	260–275 W	312–330 W
50–60%	1Recovery	12 min	100–120 W	125–150 W	150–180 W

Put this session on your bike computer or watch

Wattson works out the targets from your FTP and sends the session to your Garmin, Wahoo, Coros or Suunto.

Try this session

What this session is for

Your oxygen uptake doesn't jump straight to its peak: at the start of a steady effort, it takes a minute or two to get close. Over a 5-minute interval, a good chunk of the time is spent getting there. The fast start shortens that phase: 2 minutes at 120–130% of FTP drive your breathing and heart rate close to the ceiling, then you drop to 104–110% to finish without blowing up, while staying right next to your VO₂max.

The idea comes from Bent Rønnestad and his group. It has been measured within a single session: a 2-minute fast start increased the time spent near VO₂max, shorter starts didn't. Nobody has yet checked whether that turns into bigger gains over several weeks.

Who it's for

Advanced riders with several blocks of 4 × 5 min or the Norwegian 4 × 4 behind them, who want to get a bit more out of each interval. A recent FTP is essential: a start at 120–130% won't forgive an inflated FTP.

When to do it

One or two VO₂max sessions a week at most, and this counts as one: it replaces a classic 4 × 5 rather than joining it. Keep an easy day before and after, and avoid the day before a race. If five efforts feels like a lot, start with four and add the fifth once the end of the last one stays clean.

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. For a session this hard, you can add one or two 20-second pick-ups at the end, without tiring yourself.
Main set
37 min
5 × (2′ at 120–130% FTP + 3′ at 104–110% FTP + 3′ at 50–60% FTP)
Five 5-minute efforts, each in two parts: 2 minutes at 120–130% of FTP, or 300 to 325 W for an FTP of 250 W, then 3 minutes at 104–110%, or 260 to 275 W. Between efforts, 3 easy minutes at 50–60%. The start is very hard but controlled: a firm wind-up, not a sprint. When you drop the power, keep the same cadence and let your breathing stay high: that's the point. On a turbo in ERG mode, the switch happens by itself.
Cool-down
10 min
10′ at 40–55% FTP
10 very easy minutes at 40–55% of FTP. If the 104–110% part fell apart on the last efforts, bring the start down towards 120% next time rather than cutting the finish.

How it should feel

The first 2 minutes are very hard, so much so that the drop feels like relief. It isn't: your breathing stays maxed out to the end of the effort, and the 3 minutes at 104–110% feel longer than they are. Guide: 9 out of 10 on the start, barely less at the end.

Common mistakes

Turning the start into a sprint

Going flat out, out of the saddle, ruins the next 3 minutes. Hold the start at 120–130%, seated, like a very hard 2-minute effort. If you're well above the range after 15 seconds, you've gone too hard.

Easing off after the start

Dropping to 104–110% is about holding on, not recovering. Slide back down towards FTP and you lose exactly the time near VO₂max the start was meant to buy.

Fixing the finish instead of the start

If the final minutes become impossible, don't cut the end of the effort: bring the start down to 120%, or a touch lower. The settled part is the heart of the session.

Stacking it on another VO₂max session

This format is harder than a steady 4 × 5. It takes that session's place in your week, never an extra slot.

When to skip it

Before you start

A recently measured FTP.
Several weeks of steady-power VO₂max intervals.

Skip it if

You're tired, or a race or long ride is planned for the next day.
You're coming back from a break: go back to steady intervals first.
You have doubts about your health: get medical advice before near-maximal efforts.

Origin and evidence

Level of evidence

Limited evidenceLevel 2 of 5

Work by Bent Rønnestad and colleagues, partly in cross-country skiers, summarised in a review by Mølmen and Rønnestad (2024). The studies describe a start at about 100% of maximal aerobic power (or speed), then about 85%. The results are mixed: a 2-minute fast start increased the time spent above 90% of VO₂max, whereas 1 min 30 or 1 min starts made no difference. Over 8 × 60 s, decreasing, increasing or constant power gave the same result (2021 study). No multi-week study was found. Converting this to 120–130% then 104–110% of FTP is a Wattson approximation, as are the warm-up and cool-down. Bottom line: good evidence on single-session measures, weak on long-term benefits.

Sources

Mølmen K. S., Rønnestad B. R., revue sur l'entraînement par intervalles, 2024

Frequently asked questions

What power should I ride fast-start VO2max intervals at?

Start at 120–130% of FTP for 2 minutes, then 104–110% for 3 minutes. For an FTP of 200 W: 240 to 260 W, then 208 to 220 W. For 250 W: 300 to 325 W, then 260 to 275 W. For 300 W: 360 to 390 W, then 312 to 330 W. These are approximate conversions of the intensities described in the studies.

Why a 2-minute fast start and not a shorter one?

Because it's the only length that showed an effect. In measurements by Rønnestad's group, a 2-minute fast start increased the time spent near VO₂max, whereas starts of 90 seconds or 1 minute made no difference. The likely reason: oxygen uptake needs enough time to reach its ceiling before you back off.

Fast start or variable intensity: which should I choose?

Both aim for the same thing, more time near your VO₂max. The fast start front-loads the effort, then lets you hold a steady power: easier to pace. Variable intensity spreads three surges through the effort: more engaging, and more demanding on your concentration. Swap between them from one block to the next if you like variety.

Can I do fast-start intervals outdoors?

Yes, with a power meter and a clear 5-minute stretch of road, ideally a gentle drag. The tricky part is holding 120–130% without overshooting at the start, then dropping at the right moment. On a turbo in ERG mode, both happen for you, which makes the session more precise.

Take it up a level with Wattson

An intuitive workout editor to build cycling and running sessions in no time, then sync them to your watch or bike computer: Wahoo, Garmin, Suunto or Coros.