Myth or fact

VO2 max is mostly genes, so training barely moves it

Short answerNot the way you think

By GyroscopeUpdated November 14, 20267 sources

Not the way you think. Genes shape how fast you gain. On the same 20-week plan, some people gained almost nothing and others more than 1 liter a minute. But when people who hadn’t improved trained more, every one of them did, and with longer intervals every person in 9 studies improved.

Why people believe it

There’s a real study behind it, and a famous one. In the 1990s the HERITAGE Family Study put 481 sedentary adults from 98 families through the same 20-week training program and tested them twice before and twice after.

The average gain was about 400 milliliters of oxygen a minute. But the spread was huge. Some people gained little or nothing, and others gained more than 1 liter a minute, from exactly the same plan. Family members tended to land in the same place, with 2.5 times more variation between families than within them. The researchers estimated that up to 47 percent of the differences in response came from heritability, and they concluded that trainability “is highly familial and includes a significant genetic component.”

From there it’s a short step to “some people don’t respond, and maybe I’m one of them”. If your number hasn’t moved after a couple of months, that story is very easy to believe.

A simple way to picture it

Plant two tomato seedlings from different seed packets in the same soil and water them the same. One shoots up and the other dawdles. The seeds made the difference. But give the slow one more water and more sun and it grows too. The seeds set how fast each one grew, and both grew once they got enough.

What happened when people trained more

The 2017 researchers noted that one in five adults following the activity guidelines had been reported not to improve their fitness at all. They found that “non-response” shrank with every extra session a week and then disappeared. The biggest driver of who gained the most was the rise in total hemoglobin, the oxygen-carrying part of the blood.

What do the genes actually decide?

Two things, roughly. How fast you respond to a given amount of training, which is what HERITAGE measured. And where you started, which training studies don’t change. A pooled analysis of 28 trials found people with lower starting fitness gained more from both steady and interval training, so a low start isn’t a life sentence either.

For health, what counts is whether you can climb a group for your age and hold it, and the training studies say almost everyone can.

The best case for genes

“Up to 47 percent heritability is a lot. If half my response is genetic, why push?”

Because heritability describes why people differ from each other on a fixed plan. It doesn’t set a limit on what any one person can do with more or harder training. The HERITAGE program was the same for everyone, so the slow responders got the same dose as the fast ones. When the dose went up in the 2017 study, the slow responders caught up. Helgerud’s 2007 trial shows the same thing from the other end. Men already near the top of their age group still gained 7.2 percent in eight weeks once the sessions got hard enough.

What about age?

Age is the other thing people blame, and it’s a real force. But five Dallas men who trained for six months at 50 gained 14 percent, back to the oxygen use they’d had at 20. After 60 it’s too late covers it. And if you stop, fitness fades, but not to zero. Seven trained people who stopped for 84 days were still above people who’d never trained (Coyle 1984).

lifespan.guide makes a similar point about genes and how long you live in it’s in your genes.