The laziest
sentence in sport.

It is the genes.

It is the laziest sentence in sport.

It sounds like an explanation. It is not. It is a way to close a conversation before it reaches anybody who could have done something differently. Not the coach. Not the club. Not the parents. Not the culture the athlete grew up inside. Say it and every adult in the room is off the hook at once.

And it is wrong in a way you can measure. That is what this piece is about.

Genes decide what your body could become. Everything after that is decided by the environment. Not the environment people usually mean, the coaching and the money and the chances you get. The one almost nobody measures: what your body learned about being safe, and where it put that lesson.

Because it does put it somewhere. Into tension. Into breath. Into posture. And what sits there is what decides how you respond under pressure, whether you are able to stop, and whether you can solve a problem or only push harder at it.

I am not writing this from the outside. I am the example.

0.92 percent.

The most studied gene in sport is ACTN3. People call it the speed gene. It decides whether your body builds a protein called alpha-actinin-3, which sits inside the muscle fibres that fire fastest and hardest.

The association looks strong. In the study that made this gene famous, among sprinters who had competed at the Olympic level, twenty five men and seven women, not one was missing the protein completely. Not one.

Case closed, apparently.

Then somebody measured how much of the actual difference it explains.

In elite 200 metre sprinters, the speed gene accounted for 0.92 percent of the variation in their times (Papadimitriou et al., 2016). Not one percent of who becomes a sprinter. Under one percent of the gap between sprinters who are already at the top.

Now the honest part, because I am not going to do to this study what I am accusing other people of doing.

The researchers who produced that number argue it is substantial. In the same work, sprinters with two working copies ran 21.19 seconds over 200 metres while those with none ran 21.86, and no athlete missing the protein met the 2012 Olympic qualifying standard. At the elite margin they have a real point. Under one percent of the variation between finalists can be the difference between a medal and fourth place.

But look at what that argument is about.

It is about the last hundredths of a second between people who are already the best in the world. It is not about who becomes one of them. It is not about who is still racing at thirty five. And that second thing is what people mean when they say it is the genes.

There is also a wider problem with how confidently any of this gets repeated. A 2024 review pulled the whole literature together and found the pooled effect small enough that the authors called it of limited practical significance. And a separate review found that the bigger a genetic effect was reported to be, the less likely it was to survive when somebody repeated the study. The early headlines overstated the genes. The field corrected itself. The public story never moved.

The case is built only on the survivors.

There is a second problem with the gene argument, and it is bigger than the first.

Every one of these studies looks at champions.

Nobody has ever studied the kids with the same genotype who quit at seventeen. We do not know how many of them there were. They were never tested, because nobody tests the ones who leave.

So we look only at the people who survived their environment, and then we hand the credit to their DNA.

That is not a small technical complaint. It means the entire case for genes is built on a sample that has already been filtered by everything the argument claims does not matter.

I have the gene.

In 2012 I did a genetic test. ACTN3 came back with two working copies. The version they call the sprinter's version.

My best sprint as a professional was 830 watts, at a racing weight of 60 kilos, training full time and paid to do it.

Marcel Kittel reported peak numbers between 1900 and 2000. André Greipel hit 1903. Even Mark Cavendish, considered light in raw power and winning on technique instead, sits around 1400 to 1500.

So at my absolute peak, in the best years of my life, with the sprinter's genotype in every muscle fibre, I was at roughly half of a real sprinter. I was never in that conversation. Not close to it. I became a time trial rider and a stage racer who worked in the mountains, and I won a world title against the clock at under 23.

Everything I built a career on was the opposite of what the gene predicted.

Now the obvious objection, because anyone who knows cycling will raise it. Of course I sprinted 830 watts. I was a 60 kilo climber, permanently deep in fatigue, training the exact opposite quality for years. Sprint power is specific and I never trained it.

That is completely true. And it is the point.

Training specificity is environment. Chronic fatigue is environment. What a team needs from you at 22 is environment. A body carrying years of load that never fully released is environment. None of that is written in DNA. Every part of it was decided by where I was and what was asked of me, and together they produced a rider who could not do the one thing his genotype was supposedly built for.

There is a small piece of evidence that the material never went anywhere. Today I weigh 64 kilos and train about six hours a week, with no sprint work at all, and I sprint 1400 watts. Four kilos heavier, on a fraction of the training, producing more than I did when it was my job.

I am not claiming I got stronger. I am saying the potential was always sitting there, and for ten years I had almost no access to it.

So the gene did not decide anything. The environment decided, twice. First it made me into a rider I was not built to be. Then it kept me from the thing I was built for.

And notice where my whole career sat. Never once in that margin argument. Nobody was ever asking whether I would be first or fourth in an Olympic sprint final. The question in my career was always the other one, the one the research on hundredths of a second does not touch.

Which leaves the question this whole piece is really about. What was that environment actually doing? Not to my schedule and not to my mood. To my body, and to what I could produce on a bike.

But two brothers grow up in the same house.

This is the objection everyone raises, and it deserves a real answer.

Two children, same home, same parents, same food. One becomes a champion. The other does not. So it must be the genes.

Except they did not grow up in the same environment. Nobody ever does.

The first child arrives to different parents than the second, because people change. One is born into a good year and one into a hard one. One is the eldest and carries expectation, one is younger and is left alone. They are different ages when the same thing happens in that family, and age decides what a nervous system makes of an event.

Same address is not the same environment. It never was.

Environment is not opportunity. It is physical.

This is where most people who agree with me still get it wrong. They think environment means opportunity. It means something much more physical than that.

Take a young athlete who learns early that warmth and attention arrive after a good result and go quiet after a bad one. Nobody has to say anything. Children read it in tone of voice and in what happens at the dinner table after a race.

This has a name in the research. It is called parental conditional regard, and it has been studied directly in young athletes. It predicts what psychologists call competence contingent self worth, which is a self esteem that rises and falls with your results (Assor, Roth & Deci, 2004). In adolescent athletes it drives perfectionism. In adults, people who experienced conditional regard as children report lower general self esteem for the rest of their lives.

Four things follow, and all four are physical.

The system stops downshifting. If safety depends on producing, the body never gets clear permission to switch into recovery. It stays ready, day and night.

The body holds on. Feelings that were not safe to show get held instead of released. That holding becomes real tension in the shoulders, the jaw, the chest wall. Over years it becomes the athlete's normal and he stops noticing it entirely.

The breath gets small. Tension through the chest and abdomen means the diaphragm cannot move fully. The breath moves up and gets faster. And because the breath is one of the main signals the body uses to judge whether it is safe, a high fast breath keeps telling the system that the threat is still here. The pattern now feeds itself. This runs both ways, which is the useful part: slow, low breathing reliably shifts the body toward its recovery side, and that has been shown across hundreds of studies (Laborde et al., 2022).

Rest stops paying. This is measured, not theorised. Athletes carrying higher chronic psychological stress recover more slowly from the same training session. Their strength comes back later, their soreness lasts longer, and their energy takes days to rebound (Stults-Kolehmainen & Bartholomew, 2012). Same session. Same body. Different recovery, because of what the system was carrying before the session started.

None of that shows on a power meter. It shows up as a rider who does everything right and gets less back than everybody else.

The beliefs I raced on.

I did not understand any of this while it was happening to me.

I could not rest. I was obsessed with hours and kilojoules. If the number was not big enough, the day did not count.

That came out of the environment I grew up in and what it taught me about my own worth. Low self esteem. A feeling of not being enough. A quiet certainty that I did not deserve it. So I sabotaged myself, and I did it hardest exactly when I had a real chance to shine.

Every one of those sounds like a champion's mindset. Every one of them was working against me.

Look at when I actually rode well. It was when nobody expected anything from me, so there was no pressure. It was when I surprised myself. And it was when I got sick before a race and was forced to rest.

I did not learn anything from that at the time. I went back to the same beliefs, because to me the win looked like luck and the training looked like virtue.

The rider who destroys himself.

You know this rider. He has the material and everyone saw it in the juniors. He also has enormous willpower, which everyone praises, and which is the actual problem.

A rest day feels wrong in his body, not just in his head. Easy days turn into medium days because slow feels like losing. His mood tracks his numbers exactly. He gets sick or injured right as he approaches his best form, again and again, and calls it bad luck every time.

He never says any of it out loud, because he believes the compulsion is his talent.

I believed that for years.

You watched a rider this year who was called a genetic gift at twenty and was gone by twenty eight. That was not the genes running out.

You cannot argue a nervous system out of safety.

The coach says take three days off. The athlete agrees, means it, and is out for five hours on day two. Everyone decides he lacks discipline, which is absurd, because he is the most disciplined person in the room.

It fails because the drive is not a decision. It is an old survival strategy. Somewhere early, the body learned that being ordinary was not safe, and the adult athlete is still running that program. You cannot argue a nervous system out of something it treats as safety.

You can only give it a different experience, in the body, often enough that the old rule loosens. That means three things. Feeling the tension he has carried since he was fifteen and never noticed. Releasing it so the breath can go low and full again. And practising being a person on a day with no training, no result and no proof.

The one thing you can check tonight.

There is one thing you can check tonight, and it costs nothing.

Notice what happens in your voice when the young athlete comes home after a bad race, and compare it with what happens after a good one. Not what you say. What your voice does, and how long you stay in the room.

Children do not hear our sentences. They read our tone, and they store what it tells them about the conditions of being loved.

If those two arrivals sound different in your house, that difference is already being written into a body, and it will still be there at thirty.

"If I let go of the drive, I lose my edge."

It goes the other way, and the reason is simple.

The compulsion is not free. It runs off the same system as your training. A body that never comes down spends capacity all day staying ready for nothing, and that spending shows up nowhere you are measuring. It comes out of the same account.

Take it away and the capacity is still there. It is available now.

I saw it in my own numbers. The potential did not arrive later. It was there at 22, sitting behind a system that was spending everything it had just staying ready.

What changes is that the intensity becomes something you can aim. It arrives on race day, fully, and then it switches off. That is not less fire. That is fire with a switch.

The genes were never the point.

When a talent breaks at 26 and everybody agrees it was always going to happen, notice who that sentence is protecting.

It is never the athlete.

Genes give you the material, and that is real. What the material becomes is decided by everything around it. And whether you get to keep it is decided by whether the body underneath ever learned that it was safe to stop.

I have the sprinter's gene. At my peak, training full time, I sprinted 830 watts and won a world title against the clock instead.

The genes were never the point.

— JB