How Much Does Genetics Really Affect Your Fitness?

But genetics is also a big factor.

Weve all had that thought on bad days: Maybe Im just not cut out to succeed at this.

Where Genetics Plays a Role

Dont bother asking whether a trait is determined by nature or nurture.

For any athletic trait, Roth says, the answer is both.

Thats the idea behind the concept calledheritability.

Heritability estimates are always sort of rough, because they depend on the population that the researchers studied.

In that case, heritability will be high, close to 100%.

Here are some ballpark figures on heritability of athletic traits.

Trainability itselfhas a genetic factor, too.

Heres one more complicating, but hopeful factor: Athletic talent has many components.

Or maybe your cardio endurance isnt great, but you have long legs and an efficient running stride.

So dont give up, even if youre convinced you got a few dud genes.

In a sense, we have it easier than elites because our bar is lower.

Most of us arent trying to win a marathon, but to finishalmost anybody can train to do that.

Elites also capitalize on their genetics with training, and there we have something in common.

Genetics is hard.

The main thing we do know is that the role of genetics is complicated.

Take height, for example.

So even though there aregenetic tests availablefor fitness-related genes, theyre not very useful.

One of those genes is calledACE, and certain versions are associated with aerobic fitness in endurance athletes.

Another isACTN3, which is associated with muscular power and sprinting.

Evidence is mixed, Roth says, on whether a result on one of these tests means much.

It might contribute 1% or 2% to overall performance, he says.

He also doesnt recommend doing this testing on children.

For example, theresan adorable kidwho shows up on my Instagram all the time.

You get the idea.

you could also get a big hint about your genetics by trusting your experiences.

For example, I struggled for years with long-distance running.

Myspeedworktimes were always really good, so I dropped the marathons from my schedule and focused on short distances.

It turns outIm way better at those.

Still, dont be too quick to blame genetics for all your difficulties.

Whatever your genetics, training is never hopeless.

For almost all of us, Roth says, performance can always improve.

He is the author of theGenetics Primer for Exercise Science and Health.

Illustration by Tara Jacoby.