Login | August 11, 2025
VO2 intervals: Is there a best one?
PETE GLADDEN
Pete’s World
Published: August 11, 2025
I’ve occasionally written about the benefits of VO2 intervals, of which I firmly believe - when doctor approved - are a great complement to one’s cardio regime.
Now lately, since I’ve finally been able to return to a comprehensive cardio routine, I’ve begun doing VO2 workouts again.
And what with this resumption, I’ve been quizzed several times as to what I believe is to be the most beneficial VO2 interval session.
So let’s take a quick look at that question, in addition to how VO2 intervals differ from one another with respect to their length and intensity level.
But first, for those who may not have caught my previous VO2-related columns, let’s catch up on the basics of this interval before we launch into a dissection of a “best” VO2 and various VO2 formats.
So VO2 intervals are high intensity intervals used by aerobic athletes/fitness participants to improve both aerobic capacity and overall performance.
The VO2s purpose is to stress the body with near maximal intensities (anaerobic efforts) across very short to moderately short time periods.
Know also that VO2 intensity can be measured both by power and heart rate (HR).
With HR, there are numerous zonal systems that can be used, though typically a VO2 interval zone clocks in at around 89-100% of one’s maximal HR.
Also know that the difference between doing an interval at 89% max HR (a low end VO2) and doing an interval at 100% max HR (a high end VO2) is massive.
Thus, some HR zone systems break down this VO2 intensity into sub-zones - zone 5a, 5b and 5c.
Really fit individuals can sustain low end VO2 intervals - zone 5a - for six to 10 minutes, and the high end intervals like a 100% all out effort - zone 5c - for 10 or so seconds.
And finally, VO2 interval zones are built around an individual’s specific fitness level.
Thus, an individual with a low fitness level will have lower HRs while in VO2 intensity zones, whereas a highly fit individual can have higher HRs while in VO2 intensity zones.
Okay, so now comes the original question: Is there a “best” VO2 interval format?
No, there’s many ways to achieve a higher fitness level via VO2s, so the format you choose depends on what physiologic system you’re targeting and what your goals entail.
Short distance specialist will typically concentrate on shorter, more powerful VO2 intervals while moderate to long distance specialists will typically concentrate on longer steady-state VO2 intervals.
Yet there can still be a ton of crossover.
Let’s first look at shorter VO2s - zone 5b-c - where we’re talking about highly intense intervals with shorter recovery periods that will keep one’s oxygen consumption high throughout the whole workout.
With these intervals the first few might make you feel like you’re a monster, but they’ll add up quickly such that you’ll be slobber-knockered at the end.
Examples include: 10-20 x (30 seconds ON/15-second recovery); 10 x (40 seconds ON/20-second recovery); or 10 x (60 seconds ON/30-second recovery). In these examples the interval-to-rest ratio is 2:1
For the longer, steady state VO2s - zone 5a - you could go with a 1:1 interval-to-rest ratio or stay with the 2:1.
An example of a 1:1 interval-to-rest ratio would be: 4x (4 minutes ON/ 4 minutes recovery), a VO2 format I use quite often. But you could also go with 5 ON/2.5 recovery or 6 ON/4 recovery etc.
You could also go with a mixed bag format like this: 2 sets of (3:00 ON/2:00 recovery to 2:00 ON/1:20 recovery to 1:00 ON/0:40 recovery to 0:45 ON/0:30 recovery to 0:30 ON/0:20 recovery) with 5-8 minutes recovery between sets.
So as you can see, the sky’s the limit here when formatting your VO2 interval sessions.
Now as both a coach and athlete I utilize all the VO2 formats mentioned above.
So if you to want to use VO2 intervals, I’d recommend you first check with your doctor/cardiologist as I did.
If okayed then you’ll want to talk to a coach or exercise specialist to set up your HR zones in order to ascertain where a good entry point would be for you with respect to anaerobic VO2 training.
Once you begin you’ll find that VO2 intervals can be gut-wrenchingly tough…but the payoff in fitness gains can be immense!