A cycling coach says most people are doing VO2 max intervals wrong.
The claim comes from CTS Cycling, a well known coaching brand.
Its argument centers on interval length, effort level, and rest between reps.
VO2 max measures how efficiently your body uses oxygen during hard exercise.
Researchers treat it as one of the strongest markers of cardiorespiratory fitness.
That makes interval design a real and well studied question in exercise science.
We dug into the peer reviewed research to see what actually holds up.
What the Video Claims About VO2 Max Intervals
The video’s title points to a common training mistake.
Many athletes assume any hard interval workout will raise their VO2 max.
The video argues that specific details matter far more than people assume.
Those details include how long each interval lasts.
They also include how hard each interval should actually feel.
And they include how much rest happens between the hard efforts.
CTS Cycling coaches endurance athletes, so the framing likely centers on cyclists.
Cyclists often train by power output or heart rate zones on a bike.
A common coaching complaint is intervals that drift too easy over time.
Another common complaint is recovery periods that run too long between efforts.
This framing lines up with a long history of exercise science research.
Coaches and researchers have studied interval structure for decades.
So the video’s basic premise is not a fringe idea.
The real question is whether its specific recommendations match the evidence.
What Research Shows About Interval Duration and Intensity
One of the most cited studies on this topic comes from Norway.
Researcher Jan Helgerud and his team tested several different training methods.
One of them became known as the Norwegian 4×4 protocol.
It uses four minutes of hard effort, repeated four times.
Short active recovery periods separate each hard effort.
The target intensity sits around 90 to 95 percent of max heart rate.
That is a genuinely hard pace, not a comfortable jog.
The same research team also tested a longer, steadier run at threshold pace.
They tested a format using much shorter fifteen second bursts as well.
The 4×4 protocol produced the largest VO2 max gains of the methods tested (Helgerud et al., 2007).
The difference between the 4×4 group and the steady pace group was statistically significant.
That is not just random noise between two similar workouts.
Study length in this line of research usually runs six to twelve weeks.
That is roughly enough time for real cardiovascular adaptation to appear.
Interval training performed at roughly 90 to 95 percent of maximum heart rate produced significantly greater gains in VO2 max than continuous training at a lower, steady intensity.
A larger analysis backs up this general pattern across many studies.
Milanović and colleagues pooled data from numerous interval training trials (Milanović et al., 2015).
High intensity interval training beat continuous training for raising VO2 max overall.
The advantage grew larger when intervals lasted between three and five minutes.
Shorter, sprint style intervals showed smaller average gains in that pooled data.
Duration and intensity, in other words, both mattered for the outcome.
There also seems to be a practical sweet spot for interval length.
Intervals much longer than five minutes usually force the pace down.
A slower pace means less time spent near true VO2 max effort.
Intervals much shorter than two or three minutes have the opposite problem.
They often end before the cardiovascular system fully ramps up.
The Mechanism: Why Recovery Length Changes the Outcome
Why does interval length matter so much for VO2 max?
The answer comes down to time spent near your true aerobic ceiling.
Your heart needs time to ramp up toward near maximal output.
A short interval can end just as your heart catches up.
That leaves less total time actually stressing the cardiovascular system.
Long rest periods create a similar problem in a different way.
If you rest too long, your heart rate drops back down.
The next interval then has to build back up all over again.
Researchers studying heart failure patients found a related pattern.
Wisløff and colleagues tested aerobic interval training in that population (Wisløff et al., 2007).
Interval training improved stroke volume more than steady exercise did.
Stroke volume is the amount of blood the heart pumps per beat.
A stronger stroke volume is a core driver of a higher VO2 max.
The same interval group also showed better blood vessel function.
This is often called a central adaptation, meaning it happens at the heart itself.
That differs from peripheral adaptations, like more capillaries inside working muscle.
Most endurance training builds some peripheral adaptation over time.
Hard, sustained intervals appear especially good at driving the central adaptation.
This mechanism helps explain why the video’s focus on structure makes sense.
Interval training is one of several evidence backed ways to support heart health, alongside habits like regular sauna use.
A Second Look: Why VO2 Max Response Varies From Person to Person
Not everyone responds to the same interval workout in the same way.
A meta-analysis by Bacon and colleagues looked closely at this question (Bacon et al., 2013).
They reviewed dozens of studies on high intensity interval training.
Some people showed large VO2 max gains from a given program.
Other people showed much smaller gains from that exact same program.
Genetics likely explains part of that individual variation.
Training history and starting fitness level also play a role.
This does not mean interval structure stops mattering.
It means the single “right” workout is not identical for everyone.
A protocol that suits a trained cyclist may feel very different for a beginner.
Beginners in particular should judge progress against their own past workouts.
Comparing your results directly to someone else’s numbers can be misleading.
Two people can follow the exact same interval program and see very different results, because genetics and training history both shape how much VO2 max actually improves.
What This Evidence Does Not Prove
It is worth being honest about the limits of this research.
The Norwegian 4×4 studies mostly used young, healthy, already active adults.
Results in untrained beginners or older adults may look somewhat different.
The heart failure study involved a specific clinical population under medical supervision.
Nobody should copy a heart failure training protocol without medical guidance.
None of these studies prove that only one exact interval format ever works.
They show that interval length, intensity, and recovery all matter together.
They do not rank every possible combination against every other combination.
Most of the underlying testing also happened on a treadmill or a stationary bike.
A lab setting is not identical to a windy road or a hilly trail.
The video’s specific claims about people “doing it wrong” go beyond what any single study tested directly.
Good coaching advice can still be reasonable even without a study on that exact claim.
But it helps to know which parts rest on strong evidence and which parts are informed opinion.
Common Mistakes and a Practical Takeaway
A few patterns show up again and again in real training logs.
The first mistake is going too easy during the hard interval.
An interval that feels comfortable rarely reaches a true VO2 max stimulus.
The second mistake is cutting the interval too short.
Intervals under two minutes often end before the heart fully ramps up.
The third mistake is resting too long between efforts.
Full recovery back to a resting heart rate wastes valuable training time.
The fourth mistake is skipping easy days around the hard sessions.
Heavy interval work needs real recovery days to actually produce adaptation.
Fitness surveys suggest many readers already lean toward strength training over running.
That same inconsistency can creep into structured interval training too.
So what does a research backed VO2 max interval actually look like?
Start with a real warm-up of ten to fifteen minutes at an easy pace.
Aim for intervals lasting roughly three to five minutes each.
Effort should feel close to 90 to 95 percent of your max heart rate.
That is hard enough that talking in full sentences is not possible.
Use active recovery between reps, like easy pedaling or a slow jog.
Keep recovery time roughly equal to or shorter than the work interval.
Four to six total repetitions is a reasonable starting range for most people.
Finish with an easy cool down instead of stopping cold.
One to two sessions like this per week is plenty for most people.
The rest of your training should stay at an easy, conversational pace.
That balance matters for long term cardiovascular health, not just VO2 max.
Our breakdown of daily activity and mortality risk covers why that base matters so much.
Simple daily movement, like walking a consistent daily distance, supports the same aerobic base.
Interval sessions build on top of that aerobic base, not instead of it.
Give any new interval routine at least six to eight weeks before judging it.
Track how you feel and how your times or power numbers trend, not just one workout.
People with heart conditions or other health concerns should get medical clearance first.
Anyone new to hard interval training should build up gradually over several weeks.
Watch the video
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References
Bacon, A. P., Carter, R. E., Ogle, E. A., & Joyner, M. J. (2013). VO2max trainability and high intensity interval training in humans: A meta-analysis. PLoS ONE, 8(9), e73182. https://doi.org/10.1371/journal.pone.0073182
Helgerud, J., Høydal, K., Wang, E., Karlsen, T., Berg, P., Bjerkaas, M., Simonsen, T., Helgesen, C., Hjorth, N., Bach, R., & Hoff, J. (2007). Aerobic high-intensity intervals improve VO2max more than moderate training. Medicine & Science in Sports & Exercise, 39(4), 665 to 671. https://doi.org/10.1249/mss.0b013e3180304570
Milanović, Z., Sporiš, G., & Weston, M. (2015). Effectiveness of high-intensity interval training (HIT) and continuous endurance training for VO2max improvements: A systematic review and meta-analysis of controlled trials. Sports Medicine, 45(10), 1469 to 1481. https://doi.org/10.1007/s40279-015-0365-0
Wisløff, U., Støylen, A., Loennechen, J. P., Bruvold, M., Rognmo, Ø., Haram, P. M., Tjønna, A. E., Helgerud, J., Slørdahl, S. A., Lee, S. J., Videm, V., Bye, A., Smith, G. L., Najjar, S. M., Ellingsen, Ø., & Skjærpe, T. (2007). Superior cardiovascular effect of aerobic interval training versus moderate continuous training in heart failure patients. Circulation, 115(24), 3086 to 3094. https://doi.org/10.1161/CIRCULATIONAHA.106.675041
This article is for general information only and is not medical advice. If you have an injury, ongoing pain, or a medical condition, talk to a doctor or physical therapist before you change how you train or eat.
