Two of you are standing on the same jogging trail.
One wears a chest strap. He wears a ring, and he owns a second ring he bought when the first ring turned out to be the wrong ring. He pays a monthly fee for an app that scores how recovered he is. There are eleven jars of supplements in his kitchen cupboard. He jogs three hours a week at a pace slow enough to hold a conversation, because a man on a podcast told him that was the way. He has not been out of breath since 2022.
The other one is wearing shoes. That is his whole kit. He trains forty minutes a week.
Then the trail tilts uphill at the end.
Only one of them is still talking at the top.
Same man. Same face, same bad knee. Two versions of one life that split years ago.
The one with the rings is not lazy. He puts in more hours than the other one. He turns up in the dark. He has two years of screenshots on his phone.
He believes the body is a machine you improve by buying things for it. Somebody sold him that idea. The people who sold it to him make nothing if he ever stops buying.
The number
VO2 max is how much oxygen you can burn in one minute, for every kilo of you.
Oxygen has to travel to get used. Air into the lungs. Oxygen across into the blood. Blood pushed around by the heart. Oxygen burned inside the muscle. Four steps. Whichever step is weakest decides the whole number, and everything before it sits and waits.
So nobody is testing whether you can run fast. They are testing how much spare capacity you have. A body with spare capacity survives pneumonia, surgery, a fall, a heart attack. A body already working flat out to climb the stairs has nothing left to give when something goes wrong.
That is why one fitness number predicts so many different ways of dying.
Thirty-three studies were pooled in 2009. A hundred and three thousand people. For every one unit of capacity a person had, their risk of dying of anything at all was about thirteen percent lower. One unit is roughly the difference between sitting in a chair and walking. Eight weeks of the right training usually buys more than one unit.
There is no pill, no powder and no supplement on the market that does anything like that.
Two flights of stairs
The test is free. You have been taking it for years.
You stop on the landing. Nothing hurts. You are just breathing harder than you were five years ago. So you take out your phone and look at a blank screen for eleven seconds until your breathing settles.
Everybody does this. It is always about the stairs.
That pause is your VO2 max, showing itself without a laboratory. And unlike your age, this number goes back up if you work on it.
Trondheim
Researchers in Norway took one thousand five hundred and sixty-seven people aged seventy to seventy-seven and trained them for five years.
Their fitness went up.
After seventy, fitness falls every year. It falls whatever you do, and everyone has quietly agreed not to talk about it. This group reversed it and held the reversal for five years.
The people doing hard intervals also died at about half the rate of the people doing gentle exercise. The authors of the trial said plainly that the study was too small to prove that part, so treat the death numbers as a rumour and ignore them. The fitness result on its own is the news.
Next time somebody tells you it is too late to start, ask them how old the Norwegians were.
The sentence that walked out of its own paper
You have heard that being unfit is worse than smoking.
A hundred and twenty-two thousand people ran on a treadmill at the Cleveland Clinic. Researchers then followed them for years to see who died. Being unfit came out looking bad, which is true, and which is bad enough on its own.
What the paper actually said was that the risk from poor fitness was comparable to or greater than smoking.
Comparable to or greater than. That is a hedge. It means the risk might be about the same as smoking, or it might be bigger, and the researchers could not tell you which.
By the time that sentence reached your phone, the first half had been dropped. Comparable to was gone. Greater than was all that was left. Being unfit was now worse than smoking, stated flatly, and half the internet repeated it with the serenity of a man who has read the abstract.
The trick that makes it work has two halves, and everybody uses it. Fitness is a sliding scale, so you can take the very fittest people and the very least fit and compare them, and that gap is roughly fivefold. Smoking is a yes or no, so all you can compare is smokers against non-smokers, and that gap is about 1.41. Both numbers are real. Setting a whole scale against a single yes or no is not a comparison at all.
The honest version is still good news, and it did not need dressing up. Move yourself up one fitness band and you gain roughly what you would gain by quitting cigarettes. That was always enough.
The philosophy that got tested and lost
Three years of podcasts have told you to go slow. Zone two. Conversational pace. Never out of breath. Three hours a week, and whatever else you do, do not go hard.
Somebody finally tested it against the alternatives.
Forty people, eight weeks, four groups, three sessions a week. Every group was made to do the same total amount of work. That last part matters, because it removes the obvious excuse. Nobody could say afterwards that one group simply did more.
One group jogged long and slow. One trained a notch under breathless. One did short hard intervals. One did four minutes hard, four times over.
The two slow groups finished exactly where they started. Two months of turning up in the rain and their fitness did not move.
The short intervals gained five and a half percent. The four-by-four gained about seven.
Same hours. Same total work. The only thing that differed was how hard, and how long they stayed up there. That was the whole difference.
A review published this year says the evidence does not support zone two as the best intensity for raising this number, and that swapping your hard sessions for easy ones can cost you the gain you were training for.
Easy work is not junk, and I will come back to what it is for. In beginners, other reviews do find that slow training raises the number. And forty people is forty people, not a verdict. What died is the narrower claim, that easy is the best way to raise VO2 max, said loudly for three years by people who had this trial sitting on their desk.
Four moves, forty minutes
Four minutes hard. Three minutes easy. Repeat four times. Three days a week.
Ten minutes to warm up first. You are home in forty.
The four minutes are not arbitrary. Your heart needs real time working at its ceiling, and it takes a couple of minutes to get there, so a thirty-second sprint finishes before the useful part starts. An hour of steady jogging never reaches the ceiling at all. Four minutes is long enough to matter and short enough that you will do it again on Thursday.
You do not need a gym. A hill works. A staircase works. A bike works. The machine was never the thing that mattered.
Set the effort with your own voice instead of a monitor. During the hard four minutes you should not be able to finish a sentence. Three or four words, then you need air. During the easy three you should be able to say a full sentence, but not want to sing.
Keep the easy three minutes genuinely easy. They are not filler. They let your heart come down far enough that the next hard four can be hard. Jog them at medium and you arrive at round three already tired, and round three was the one that was going to pay. So let people pass you.
Test yourself at eight weeks. Pick a hill and time yourself up it. Same hill, same watch, same hour of the day, both times. Write today’s time down before you start training, because in eight weeks you will not remember it honestly. Nobody does.
Across twenty-eight trials, the gain runs ten to twenty percent in eight to twelve weeks. More than that if you are starting from nothing.
Or forget the hill and use the stairs. You are standing at the bottom of them already.
What the industry leaves out
The two men on that trail had the same genes. That is what made the comparison fair. You will not get that comparison with anybody else, and the reason matters more than anything else in this piece.
Four hundred and eighty-one adults did twenty weeks of identical supervised training. Same programme, same coaching, measured before and after. The study is called HERITAGE and it has been in the literature since 1999.
The average person improved. The spread around that average was enormous. Some people gained double the average. Some people did every session correctly for twenty supervised weeks and gained nothing at all.
About half of how much you improve is inherited. Not your starting fitness, which you had already guessed. The size of your gain. Two brothers can train identically for eight weeks and one of them finishes where the other will be in six months.
You will not hear this from anybody selling a programme, because it cannot be sold. Every programme rests on one promise, that what you get out depends on what you put in. HERITAGE says that for a large minority of people, what you get out depends on your parents.
If you are a low responder, you find out at week eight, and it does not mean you failed. It means VO2 max is not where your effort pays. The same training is still lowering your blood pressure, steadying your blood sugar, fixing your sleep, lifting your mood, and building the strength to carry your own shopping at eighty. None of those run on the gene that governs this one.
So ask anybody selling you a protocol, me included, who it does not work for. If they cannot answer, they have not read their own literature. Or they read it and decided you would be happier not knowing.
One warning, and it is not a formality. Four minutes at your ceiling is genuinely hard work. If you have heart disease, or you get chest pain when you push, or you are past forty-five and have not moved in years, get checked by a doctor first. The protocol is not gentle. Your first eight weeks can be.
Nine minutes, with the studies on screen as they come up.
There is a new one every week.
BEFORE YOU GO
The practitioners who actually fix people are not smarter than the ones who sell you things. They are harder to distract.
Somebody arrives with a complaint. The pill pusher treats the complaint, because there is a product shaped exactly like it. The good one treats the complaint too, and then keeps going, because the thing making the noise is almost never the thing that broke.
So he asks what time you get up. What you eat standing at the sink. Whether anybody has touched you this month. Whether you have a reason to be awake at all. And he follows that chain until it stops, even when it ends somewhere he has nothing to sell you.
There are four places the chain can end. Your body. Your mind. Your spirit. And the fourth one has no good name, so call it the field. It is everything around you that acts on you and that nobody makes money from. The light you get. The ground under you. The air. The noise. The people in the room.
They are tied to each other. The three in the morning waking is the two glasses of red. The red is the Tuesday you dread. The Tuesday is a job you stopped believing in. The bloating is eating standing over the sink in four minutes flat, and that is not greed, it is having nobody to sit down with. The tiredness that iron tablets did not fix was never about iron. The anxiety that arrives at four every afternoon is what you ate at noon.
Pull one thread and three others move. Which is how a person spends ten years and a great deal of money treating whichever end of it they happened to notice first.
Energeia is that method with the reading already done. Close to three hundred protocols across those four areas, taken from practitioners who work at root causes, sorted so that all four get looked at together instead of one at a time.
The questionnaire takes four minutes. It comes back with the one change most worth your next eight weeks, whichever of the four areas that turns out to be in.
It is free.
White lettering on black is murder on my eyes.
the short intervals did almost as well as the 4 x 4 workout.