How to Do VO₂ Max Intervals on the Bike

VO₂ max intervals are some of the most effective — and most demanding — sessions we use with cyclists and triathletes. But executing them well is about much more than simply hitting a prescribed power number.

The objective of VO₂ max training is to accumulate quality time at or close to maximal oxygen uptake. Power is useful for helping us achieve that, but it is only one part of the picture.

To get the most from these sessions, I encourage the athletes I coach to consider power, heart rate, breathing and rate of perceived exertion (RPE) together.

In this guide, I’ll explain how to execute VO₂ max intervals on the bike, how to pace short and long intervals, when a decline in power is acceptable, why I generally prefer not to use ERG mode, and three of my favourite VO₂ max workouts.

VO₂ Max Training Isn’t Just About Power

A power meter is an excellent training tool, but the wattage displayed on your head unit or indoor training platform isn’t the physiological objective of a VO₂ max workout.

We’re ultimately trying to increase oxygen demand and accumulate time at or close to maximal oxygen uptake.

That’s why there are four useful signals to consider during these sessions:

• Power
• Heart rate
• Breathing
• Rate of perceived exertion (RPE)

Heart Rate During VO₂ Max Intervals

Having reliable heart-rate zones is useful because we ideally want to see heart rate rise progressively through a VO₂ max session and spend time above threshold, in what many training models would describe as the VO₂ max heart-rate zone.

Don’t expect this to happen immediately.

During the first interval, your heart rate may only reach that zone towards the end of the effort — or potentially not at all. As the workout progresses, it should generally reach a high level earlier in subsequent intervals.

During a block of short intervals, you’ll often see heart rate gradually ratchet upwards: rising with each effort and falling progressively less during the short recoveries.

Pay Attention to Your Breathing

Breathing is another extremely useful indicator.

As you approach maximal oxygen uptake, breathing becomes noticeably different. It becomes much more gaspy and erratic and considerably less rhythmic and controlled than it is at lower intensities.

Learning to recognise that sensation can help you understand whether you’re achieving the type of internal load we’re looking for from a VO₂ max session.

Use RPE Alongside the Numbers

Your rate of perceived exertion should also rise progressively rather than being maximal from the opening minute.

You might begin an interval or the first block of a workout around 7–8/10 RPE, before eventually reaching something closer to 9–9.5/10 towards the end of the hardest intervals.

If you’re already at 9.5/10 during the opening minutes of a long VO₂ workout, you’ve probably started too hard.

Why Percentage of FTP Is Only a Guide

One of the reasons I don’t want athletes blindly chasing a particular wattage is the enormous variation in what constitutes an appropriate VO₂ max power target.

Using the popular Coggan power model as an example, the traditional VO₂ max training zone extends from approximately 106–120% of FTP.

That’s already a very large range.

Think about the difference between riding for 30 seconds at 106% of FTP and riding for five, six or even eight minutes at the same percentage. They are completely different efforts.

Short microbursts can also be prescribed significantly above the traditional upper end of the VO₂ max zone — sometimes at 130% of FTP or higher.

The appropriate power therefore depends on several factors:

• Duration of each interval
• Duration of the recovery
• Number of repetitions
• Number of sets
• The athlete’s physiology
• The athlete’s training history

Two athletes can have exactly the same FTP and still require substantially different power prescriptions for the same VO₂ max workout.

This is why percentages should be treated as useful starting points rather than absolute rules.

Short vs Long VO₂ Max Intervals

I broadly divide bike VO₂ max sessions into two categories: short intervals and long intervals.

Short VO₂ Max Intervals

Short intervals are typically one minute or less and are usually performed in an on/off format within blocks or sets.

Examples include:

• 30 seconds on / 30 seconds off
• 30 seconds on / 15 seconds off
• 40 seconds on / 20 seconds off
• 1 minute on / 1 minute off

These can be an excellent introduction to VO₂ max training because there are lots of individual repetitions. If you need to remove one or two repetitions from a block, you can still accumulate a considerable amount of quality work.

Short on/off intervals also work particularly well indoors. The trainer provides a controlled environment where it’s easy to repeatedly transition between hard and easy efforts.

Long VO₂ Max Intervals

Longer VO₂ max intervals commonly last between three and five minutes, although they can extend to six, seven or even eight minutes.

Typical examples include:

• 3 minutes on / 3 minutes off
• 4 minutes on / 4 minutes off
• 5 minutes on / 5 minutes off
• 5 minutes on / 3 minutes off

These require considerably more pacing discipline because getting one interval badly wrong can compromise a significant proportion of the entire workout.

I particularly like doing longer VO₂ max intervals outdoors on a suitable climb. You can complete the interval uphill and use the descent as part of the recovery.

However, don’t shorten the prescribed recovery simply because you’ve reached the bottom of the climb. Continue riding easily until you’ve completed the recovery before starting the next effort.

How to Pace VO₂ Max Intervals

One of the most common mistakes with VO₂ max training is starting too hard.

You arrive fresh, you’re motivated, the legs feel good — and the first interval becomes considerably harder than it needs to be.

With longer intervals, I often encourage athletes to think of the first repetition almost as an extension of the warm-up.

It should feel controlled.

In an ideal session, power remains reasonably consistent while heart rate rises progressively. As the session develops, heart rate reaches the desired intensity sooner and spends longer there.

But real-world workouts rarely look perfect.

Is It Okay for Power to Decline?

Yes — within reason.

I don’t believe a VO₂ max workout has failed simply because power has declined slightly between the first and final intervals.

A modest decline can be perfectly acceptable if:

• Your heart rate is still reaching the desired intensity
• Your breathing remains very hard
• You can maintain good pedalling mechanics
• You can still generate a strong cadence
• You remain on top of the effort rather than simply surviving it

What we don’t want is power completely falling off a cliff.

If you’re supposed to be completing VO₂ max efforts but can barely produce tempo power by the end of the workout, you’ve gone too far.

Sometimes Dropping a Rep Is the Right Decision

This is particularly useful with short intervals.

Imagine you have a set of ten repetitions and by number seven or eight you know that completing the final two will completely compromise the remaining sets.

Ending that block slightly early, recovering properly and completing the next block well can produce a better overall workout than stubbornly forcing yourself through every prescribed repetition.

You can then use what you’ve learned to improve your starting power the next time you perform the session.

Why I Generally Don’t Use ERG Mode for VO₂ Max Intervals

ERG mode can be extremely useful for certain indoor cycling sessions, but I generally prefer athletes to control their own resistance during VO₂ max work.

One important reason is that it gives you the ability to modulate power during an interval.

Imagine you’re two minutes into a five-minute interval and realise that maintaining the current power for another three minutes is going to destroy you.

Without ERG mode, you might reduce your power by 3–5%.

Your heart rate doesn’t immediately fall because you’ve reduced power slightly. It may continue rising while you settle into a marginally more sustainable output.

This allows you to manage the interval, maintain a very high oxygen demand and potentially complete the full session successfully.

Learning to make these small adjustments based on power, heart rate, breathing and RPE is a valuable pacing skill.

Don’t Turn Every VO₂ Workout Into a Hero Session

If you’re having an exceptional day and feel capable of finishing slightly stronger than prescribed, that’s fine.

But don’t turn every good day into a test.

VO₂ max development comes from being able to stack quality training consistently, not from creating one spectacular workout file and then being unable — or unwilling — to repeat the session the following week.

Remember: it’s a training session, not a race.

Treat VO₂ Max Day Like Game Day

VO₂ max workouts are demanding, so I like the athletes I coach to think of an important VO₂ session as game day.

Firstly, position it sensibly within your training week.

Ideally, your key VO₂ session comes after an easy day or rest day. In some cases, having two relatively easy days beforehand can be appropriate.

Avoid putting your key VO₂ session immediately after another hard interval workout or a particularly demanding long endurance day.

Then remove as many barriers as possible before you start:

• Get a good night’s sleep
• Fuel appropriately beforehand
• Start properly hydrated
• Have your bike ready
• Charge your devices
• Prepare bottles and nutrition
• Use adequate cooling if training indoors
• Get your music, kit and training environment sorted

Arrive at the session fresh, fuelled and prepared to work.

Three of My Favourite Bike VO₂ Max Workouts

There is no single perfect VO₂ max workout. Different sessions can be useful at different stages of training and for different athletes.

However, these are three sessions I use regularly with the athletes I coach.

1. Rønnestad 40/20 Intervals

This workout uses repeated 40-second efforts separated by only 20 seconds of recovery.

Workout:

• 3 × 13 repetitions
• 40 seconds hard / 20 seconds easy
• 5–8 minutes recovery between sets
• Approximately 115–125% FTP for the 40-second efforts as a starting guide

More experienced athletes may sometimes progress to four sets.

Don’t attack the opening block. Let the effort come to you and watch for heart rate gradually ratcheting upwards as the set progresses.

The 20-second recoveries pass extremely quickly, so take them genuinely easy.

2. 6 × 3-Minute VO₂ Max Intervals

This is a simple but highly effective longer-interval session using a 1:1 work-to-recovery ratio.

Workout:

• 6 × 3 minutes hard
• 3 minutes easy between intervals
• Approximately 110–120% FTP as a starting guide

Keep the first repetition deliberately controlled and take the full three-minute recovery.

This is also an excellent session to perform outdoors on a suitable climb.

When riding outside, you can naturally alternate between seated and standing riding. Just don’t get out of the saddle at the end purely to artificially rescue your average power.

3. 5 × 5-Minute VO₂ Max Intervals With a Hard Start

This is one of my favourite variations for longer VO₂ max work.

Workout:

• 5 × 5 minutes
• 3 minutes recovery between intervals
• First 30 seconds: approximately 125–140% FTP
• Remaining 4:30: approximately 103–110% FTP

Again, those percentages are guides and can vary considerably between athletes.

The harder you ride the opening 30 seconds, the lower the sustainable power is likely to be during the remaining four and a half minutes.

The purpose of the hard start is to rapidly increase oxygen demand and drive heart rate and breathing upwards earlier in the interval.

The idea is to accumulate more quality time at or close to maximal oxygen uptake during the five-minute effort.

Which VO₂ Max Workout Should You Do?

There isn’t one magical VO₂ max session that every cyclist should perform.

Different types of VO₂ max work can be used depending on your training phase, strengths and weaknesses, target event and previous experience with high-intensity training.

Whichever workout you’re doing, remember the fundamental principle: don’t blindly chase the prescribed watts.

Use power alongside heart rate, breathing and RPE. Pay attention to how your body responds and learn to improve your pacing with experience.

VO₂ max intervals can feel intimidating when you’re new to them, but repeated exposure makes you much better at judging the effort — and much more comfortable with the discomfort involved.