Stephen Seiler said something on the podcast that changed how I programme every hard session: "The key variable isn't peak power. It's time spent at VO2max." Most riders walk into these intervals thinking the goal is to hurt as much as possible for as long as possible. Seiler's research says the opposite — the goal is to accumulate minutes near your oxygen ceiling, which means starting conservative enough to actually complete the set.
The riders who avoid VO2max sessions know they hurt and find reasons to skip them. The riders who show up tend to go too hard too early, blow up on the third rep, and spend the rest of the week flat. Same suffering. Completely different outcomes — one builds your aerobic ceiling, the other just makes you tired.
Dan Lorang programmes these blocks for Roglič at Red Bull–Bora–Hansgrohe. John Wakefield designs them for the same squad. Tim Kerrison built the periodised approach at Team Sky. What they all agree on is surprisingly simple, and it changes everything about how you should structure these sessions.
What VO2max Actually Means For You
Let me be really clear about this. VO2max is the maximum rate at which your body can consume oxygen during exercise. It is the absolute ceiling of your aerobic system. Every other metric you care about — your FTP, your threshold power, your ability to sustain efforts on climbs — sits underneath that ceiling. The higher your VO2max, the more room there is for everything else to grow.
Think of it this way. If your VO2max is the height of the building, your FTP is the floor you live on. You can renovate your floor, make it more efficient. But you cannot move your floor higher than the roof. Raising your VO2max raises the roof. And here is the good news: VO2max is trainable. The science on this is clear and it has been clear for decades. The question is how to do it in a way that actually accumulates the right stimulus without destroying you in the process.
The Key Insight: Time At VO2max
Here is where it gets really interesting. When I had Professor Seiler on the podcast, he talked about the variable that matters most for VO2max development. It is not peak power. It is not how much you suffer. It is time at VO2max — the total number of minutes your oxygen consumption spends at or near its maximum during a session.
This changes everything about how you design the intervals. A session where you go out at 140 percent of FTP, hold on for two minutes, and blow up might feel heroic. But the time you actually spent at VO2max was probably less than 90 seconds. Compare that to a well-paced 4x4 session where your oxygen consumption ramps up during the first interval, stays elevated through the recovery periods, and accumulates eight to twelve minutes of genuine time at VO2max. Same suffering. Drastically different training stimulus.
The practical consequence is counterintuitive. You often accumulate more time at VO2max by starting slightly easier and completing all the intervals than by starting hard and fading. The rider who finishes every rep at the target power gets more adaptation than the rider who crushes the first two reps and limps through the last two. This is precisely what Seiler's research shows.
The Five Session Formats
What follows are the five VO2max session formats that come up most frequently in my conversations with WorldTour coaches. I am going to give you the exact prescriptions — the power targets, the durations, the recovery periods — so you can go and do them this week.
The Classic 4x4 (The Seiler Gold Standard)
Four minutes at 106 to 115 percent of FTP, followed by four minutes of active recovery at roughly 50 percent of FTP. Four intervals. Total work time: 16 minutes. Total session time including warm-up and cool-down: roughly 50 to 60 minutes.
This is the format Seiler has studied most extensively and the one most coaches use as their default VO2max prescription. The four-minute work interval is long enough for your oxygen consumption to ramp up and reach near-maximum levels by the second or third minute. The four-minute recovery is long enough to partially recover but short enough that your VO2 does not drop all the way back to baseline. By the third and fourth intervals, you are spending almost the entire work period at or near VO2max.
The beauty of the 4x4 is its forgiveness. You can start at the lower end — 106 percent of FTP — and still accumulate meaningful time at VO2max because the intervals are long enough for oxygen consumption to climb. If you are new to VO2max work, start here. When I had John Wakefield on the podcast, he talked about the 4x4 being the bread-and-butter session at Bora-Hansgrohe. If it is good enough for WorldTour riders, it is good enough for you.
The 5x3 (Higher Intensity, Shorter Intervals)
Three minutes at 108 to 118 percent of FTP, three minutes of active recovery. Five intervals. Total work time: 15 minutes.
The 5x3 suits riders who fade during four-minute efforts. If you consistently see your power drop off in the last 60 seconds of a 4x4, the three-minute format lets you hold a slightly higher intensity without the fade. The trade-off is slightly less time at VO2max per interval because the ramp-up period eats into a higher proportion of the shorter effort. You compensate by doing five intervals instead of four.
This format is also useful as a progression from the 4x4. Once you can complete 4x4 sessions cleanly, moving to 5x3 at a slightly higher intensity provides a new stimulus without dramatically changing the session structure. Same basic framework. Higher ceiling.
The 30/30s (The Billat Protocol)
Thirty seconds at 120 to 130 percent of FTP, thirty seconds at 50 percent of FTP, repeated 15 to 20 times continuously. Total work time: 7.5 to 10 minutes of hard effort spread across 15 to 20 minutes of total elapsed time.
The physiology behind the 30/30 format is fascinating. The short recovery periods are not long enough for your oxygen consumption to drop significantly. After the first few repetitions, your VO2 climbs to near-maximum and essentially stays there for the rest of the set, even during the recovery periods. The result is that 30/30s accumulate an enormous amount of time at VO2max relative to total session duration.
The mental experience is different too. Each 30-second effort is over before the discomfort truly peaks. You are always either about to start an effort or about to get a break. Many riders who dread four-minute intervals find 30/30s surprisingly manageable, even though the physiological stimulus is comparable or greater.
The catch is precision. Too easy and your oxygen consumption never reaches VO2max. Too hard and you blow up at repetition eight. Start at 120 percent of FTP for your first 30/30 session and adjust from there.
The 3x5 (The Long Interval Challenge)
Five minutes at 105 to 112 percent of FTP, five minutes of active recovery. Three intervals. Total work time: 15 minutes.
This format is for riders who can sustain longer efforts and want maximum time at VO2max per interval. The five-minute duration means your oxygen consumption has ample time to reach and sit at maximum — you are spending the final three minutes of each interval essentially at VO2max if the intensity is right. The trade-off is that only three intervals means fewer opportunities for the effort. Each one has to count.
The 3x5 is demanding because five minutes at VO2max intensity is a long time. There is no hiding. The riders who thrive on this format are the ones comfortable with sustained discomfort — the ones who settle into a hard effort and hold it without constant mental negotiation. If that does not sound like you, the 4x4 or 30/30s will give you a comparable stimulus in a more manageable package.
The Roennestad 30/15s (For Well-Trained Riders Only)
Thirty seconds at 130 to 150 percent of FTP, fifteen seconds of recovery. Six to ten repetitions per set, two to three sets, with five minutes of easy spinning between sets.
Let me be really clear about this one. The Roennestad 30/15 protocol is aggressive. The combination of high intensity and minimal recovery accumulates lactate rapidly, and the session demands a level of fitness and fatigue resistance that most recreational cyclists have not built yet. This is not a session for someone who has just started doing VO2max work.
The research from Bent Roennestad's group in Norway shows that the protocol produces significant VO2max gains in already well-trained cyclists. Your body is essentially forced to operate at maximal oxygen consumption for the entire set because recovery periods are too short for any meaningful clearing of metabolic byproducts.
If you have been doing VO2max work consistently for at least four to six weeks and you can complete 4x4 and 30/30 sessions cleanly, the 30/15 protocol is a powerful progression. If you have not, file it away for later.
How To Find Your Right Intensity
The single most common mistake I see in VO2max training is starting too hard. Every coach I have spoken to says the same thing. Start conservative. If you cannot complete the last interval at the same power as the first, you started too hard. It really is that simple.
For your first session in any new format, start at the bottom of the prescribed intensity range. For a 4x4, that means 106 percent of FTP, not 115. If you finish the fourth interval feeling like you could have done a fifth, the intensity was right. If you did not finish the fourth interval, it was too hard. Adjust by two to three percent for the next session.
The ego wants to go harder. I get it. You know the moment when you are warming up for intervals and the legs feel good and you think "I could push this today." Resist that. Dan Lorang programmes VO2max blocks for riders who are among the most talented athletes in the history of the sport, and even they start conservative and build. The first session of a VO2max block should feel like you left something in the tank. By week four or five, it should feel like you found exactly the right edge.
Building A Six-Week VO2max Block
Here is where the practical application comes together. A well-structured six-week VO2max block might look something like this.
Weeks one and two are the foundation. Two 4x4 sessions per week at 106 to 110 percent of FTP. The focus is on completing all intervals cleanly. Every other session during the week should be zone 2 endurance work. No tempo. No sweet spot. Just easy riding and VO2max work. This is the polarised approach that Seiler's research supports.
Weeks three and four are the progression. Move to 5x4 — five intervals of four minutes — at 108 to 112 percent of FTP. The additional interval increases total work time from 16 to 20 minutes. The slightly higher intensity adds stimulus. If one of your two weekly sessions is a 5x4, the other could be a 30/30 session to provide variety and a different type of VO2max stress.
Weeks five and six are the peak. Push the intensity to the higher end — 112 to 115 percent of FTP for the 4x4 or 5x4 format. If you have tolerated the block well, introduce a single 30/15 session in week five. Your legs will be tired. That is expected. The adaptation comes during the recovery week that follows.
After six weeks, take a full recovery week — reduced volume, no intensity — and then test. You will almost certainly find that your VO2max has improved and, with it, the ceiling above which your FTP can grow.
When NOT To Do VO2max Work
Timing matters as much as execution. There are three situations where VO2max sessions do more harm than good.
During the base phase, VO2max work is premature. Your base phase builds the aerobic foundation — mitochondrial density, fat oxidation, cardiovascular efficiency — that makes VO2max training productive later. Skipping the base to get to the "exciting" intervals is like building the penthouse before pouring the foundation. Tim Kerrison built the Team Sky periodisation model around this principle. The base phase was non-negotiable.
When accumulated fatigue is high, VO2max sessions become counterproductive. If you are carrying fatigue from a heavy training week or life stress that has disrupted your sleep, session quality will be poor and recovery cost will be high. A bad VO2max session does not build fitness. It just adds fatigue. Better to ride zone 2 and come back to the intervals fresh.
More than twice per week is too much for almost every amateur cyclist. Two sessions per week, separated by at least 48 hours and surrounded by easy riding, is the ceiling. More than that and you end up in a fatigue hole where every session is compromised.
The Lorang Approach: What Amateurs Can Learn From Grand Tour Programming
When Dan Lorang sequences a season for a Grand Tour contender, VO2max blocks are placed strategically within the annual plan. There is a base period. A build period where VO2max work features prominently. A race-specific period. Recovery blocks between each phase. Nothing is random.
The lesson for amateurs is the same. Structure matters more than intensity. A six-week VO2max block placed at the right time in your season, following a proper base period, will produce dramatically better results than random VO2max sessions scattered through the year whenever you feel like doing something hard. The sessions are not complicated. The 4x4 is not a secret. What separates the riders who improve from the riders who stagnate is when they do the work, how they progress through a block, and whether they respect the recovery that makes the adaptation happen.
You are not new to the bike. You train. You have probably done some version of VO2max work before. But if you are like most riders, you have done it without a clear plan for how the sessions build on each other, when to push the intensity, and when to back off. That plan is the difference between another set of intervals and a genuine shift in your aerobic ceiling.
If you want the structure, the coaching, and a community of riders who are serious about getting faster, the Not Done Yet community at skool.com/roadmancycling is where we build training blocks like this together. Weekly live calls, structured plans, and the kind of accountability that makes the hard sessions happen even when the motivation is not there.