What is vo2 max and how to improve it
- Clem Duranseaud
- 4 days ago
- 6 min read
VO₂ max is often called the single best marker of cardiovascular fitness, for good reason. It’s strongly linked to endurance performance, overall health, and even longevity.
In simple terms, VO₂ max refers to the maximum amount of oxygen your body can use in one minute of exercise. The higher it is, the more efficiently you can turn oxygen into usable energy.
But VO₂ max isn’t just something you’re born with, and it’s not reserved for elite endurance athletes.
In this article, we’ll break down what actually determines VO₂ max, which factors matter most, and the two variables you can train to improve it.
What affects VO2 Max
VO2 max is influence by a chain of factors:
How much blood your heart can pump
This is influenced by your heart size, strength and stroke volume
How much oxygen your blood can carry
Influenced by plasma volume and red blood cells
How well muscles extract that oxygen
Influenced by capillary and mitochondria density
How much blood can you pump?
With each heartbeat, fresh, oxygen filled blood is pumped into your arteries.
Your heart is a muscle, just like your biceps or quads. The more you challenge it, the stronger and bigger it becomes. A stronger heart can pump more blood per beat, which means more oxygen gets delivered to your muscles and more energy for your workouts.
The amount of blood that is pumped with each heartbeat is called your stroke volume. On top of having a strong heart, plasma volume can increase this.
Your blood is made up of blood cells (45%) and plasma (55%). Plasma is mainly water and it's role is to carry the blood cells around.
We can increase this by doing high intensity intervals and classic VO2 intervals. We will take a closer look at training parameters in the next section.
How much oxygen your blood carries
Oxygen is carried in your blood by red blood cells, thanks to hemoglobin, these tiny cells are basically your body’s delivery service for oxygen.
The more red blood cells you have, the more oxygen your muscles get, and the better your performance.
Here’s the catch: apart from regular exercise, there’s no magic pill to boost red blood cells. Any form of aerobic activity, jogging, cycling, group fitness classes, or even dancing around your living room will help. Basically, if it gets your heart pumping and your lungs working, it counts.
You can naturally increase red blood cells by living or training at high altitudes, where oxygen is scarce.
But unless you have a mountain over 1,500m nearby, this isn’t exactly practical. (Trust me, I live in London. The tallest hill here is Primrose Hill, which peaks at… 60m. Not exactly Olympic altitude.)
Any consistent cardio will increase your red blood cells over time. No need to overthink it, just move, consistently, and your oxygen delivery system will adapt.
The best VO2 Max predictor: how well your muscles can use oxygen
Two key players make this happen: capillaries and mitochondria.
Capillaries are tiny blood vessels that branch off from your arteries. They act like delivery routes, bringing oxygen-rich blood right to your muscle fibers. The more capillaries you have, the more oxygen your muscles can receive.
Mitochondria are the power plants inside your muscle cells. They take that oxygen and turn it into energy. More mitochondria = more oxygen turned into usable fuel = higher VO₂ max.
So how do you build more capillaries and mitochondria? The answer might surprise you: long, steady-state cardio. Yes, the most “boring” form of exercise, jogging, cycling, or rowing at a steady pace, is one of the best ways to boost your VO₂ max.
It’s not flashy, it’s not fast, and it might feel slow… but it works. And if your goal is to increase how efficiently your muscles use oxygen, this is the non-negotiable foundation.
Now let's have some fun and take a deeper look at training parameters!
How to program VO2 max intervals
The goal of these interval workouts is to get close to your max heart beat to get better at pumping blood.
Some classic formats for these are:
The 4 x 4 method: 4 minutes at a high intensity, followed by 4 minutes of rest
30/30 method: alternating 30 seconds of hard work with 30 seconds rest for 5-8 minutes
20/10 method: alternating 30 seconds of hard work with 10 seconds rest for 5-8 minutes
The first few intervals wont be too hard. The goal is to maintain your pace all the way through. In these workouts, the last couple intervals are the most important. They are also the most gruelling.
How to progress your VO2 Intervals
4 x 4 method
If you've never done these before, start easy.
Week 1: 3 x 3
Week 2: 4 x 3
Week 3: 4 x 4
This will help you ease into the VO2 training.
Once you're comfortable with 4 x 4, you can progress to 5 x 4 and then to 5 x 5.
30/30 method
Week 1: 2 x (30/30 for 5 minutes), rest 3 min in between the 5 minutes
Week 2: 2 x (30/30 for 6 minutes), 3 min rest
Week 3: 2 x (30/30 for 8 minutes), 3 min rest
Week 4: 3 x (30/30 for 6 minutes), 3 min rest
Once again, this allows you to start easy and gives your body a chance to adapt to the new stimulus.
This progression method works with the 20/10 as well.
How to increase capillaries and mitochondria
If you want to boost your VO₂ max, this is the easiest and most effective way: long, steady-state cardio.
The key is intensity. Keep it low enough that you could hold a conversation throughout most of your session. This isn’t about pushing yourself to the limit, it’s about building a solid aerobic foundation.
Start simple:
Duration: 30 minutes per session
Frequency: 2–4 times per week
Over time, gradually increase the duration. Your body adapts to longer sessions by growing more capillaries and mitochondria, the exact changes that let your muscles use oxygen more efficiently.
A few guidelines to keep it realistic:
You don’t need 10 hours of cardio per week, that’s egricious.
Aim to slowly work past the 1-hour mark per session.
Long-term goal: comfortably move for 90–120 minutes in a single session.
Consistency is what matters most. Stick with it, and over time, you’ll notice that your endurance, recovery, and VO₂ max all improve, without killing yourself in high-intensity intervals every day.
Sample plan to increase VO2 max
Week one
Workout 1: Steady state cardio, 30 min
Workout 2: Intervals
Warm up 5-10 min easy jog, then 3 x 3 mins on 3 mins off
Workout 3: Steady state cardio 30 min
Week two
Workout 1: Steady state cardio, 35 min
Workout 2: Intervals
Warm up 5-10 min easy jog, then 4 x 3 mins on 3 mins off
Workout 3: Steady state cardio 35 min
Week three
Workout 1: Steady state cardio, 40 min
Workout 2: Intervals
Warm up 5-10 min easy jog, then 4 x 4 mins on 3 mins off
Workout 3: Steady state cardio 40 min
Week 4
Workout 1: Steady state cardio, 45 min
Workout 2: Intervals
Warm up 5-10 min easy jog, then 4 x 4 mins on 3 mins off
Workout 3: Steady state cardio 45 min
This sample training plan can be added to your current gym program to increase your VO2 max. Both the intervals and the steady state progress in a sustainable way to get you to a good training level.
Conclusion
VO₂ max is one of the most powerful markers of both performance and long-term health, and the good news is that it’s highly trainable.
Improving it comes down to strengthening the entire oxygen delivery chain:a heart that can pump more blood, blood that can carry more oxygen, and muscles that can actually use it.
Short, hard intervals improve how much blood your heart can push with each beat. Long, steady-state cardio builds the capillaries and mitochondria that let your muscles extract and use that oxygen efficiently. You don’t need to choose one or the other, you need both.
The key is consistency, not hero workouts. Two to three aerobic sessions per week, combined with one focused interval workout, is enough to move the needle if you stick with it.
Build the base. Sprinkle in intensity. Give it time. Do that, and not only will your VO₂ max improve, every physical task will start to feel easier.
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