Is fitness in your genes? A study of 288,000 people says measure it instead

A genetic score for fitness, built from more than 900,000 points in the genome, explained 0.2% of how fit people actually were. It also did very little to predict who got ill. People who measured as fit were healthier than people who measured as unfit, whichever genes they had. That is the short version of a study published in May 2026, and it is good news for anyone who suspects they were simply born unathletic.

The study

The paper is "Evaluation of Genetics in the Association Between Cardiorespiratory Fitness and Health," by Joensuu, Sillanpää and colleagues, published in the Scandinavian Journal of Medicine & Science in Sports.1 They asked a straightforward question. Fit people get fewer chronic diseases and live longer. Is that because fitness protects them, or because the same genes that make someone fit also make them healthy?

To find out, they gave everyone a polygenic score for fitness: a single number that weights 905,707 common DNA variants by their effects in an earlier genome-wide study of aerobic fitness. Then they followed two large populations:

• FinnGen, 262,137 Finnish adults with an average age of 53.5, linked to national health registers.
• HUNT3, 26,115 Norwegian adults with an average age of 59.0, used to check whether any finding held up in a second country.

In 1,316 of the Norwegian participants, fitness had also been measured properly: a treadmill test taken to exhaustion while their breathing gas was analysed, which gives peak oxygen uptake (VO₂peak), the standard laboratory measure of aerobic fitness.

What the genes predicted

Very little. Against those 1,316 treadmill tests, the genetic score explained 0.20% of the variation in measured fitness. Each standard deviation of the score, the gap between someone average and someone in roughly the top sixth, came with just 0.4 mL/kg/min more VO₂peak.1 For scale, the authors point out that the smallest change in fitness thought to matter clinically, one MET, is 3.5 mL/kg/min, almost nine times that.

The score's links to disease were small in the same way. In FinnGen, each standard deviation was associated with about 2% lower risk of death from any cause and about 4% lower risk of type 2 diabetes. When the authors checked in the Norwegian cohort, only the diabetes association held, and it weakened once body weight was taken into account. The links to heart disease, cancer and lung disease did not replicate.1 In the authors' own estimate, favourable genes would account for roughly 1 percentage point of the 8% lower diabetes risk that comes with one MET of extra fitness.

Fit people were healthier, whatever their genes

The most useful part of the paper is a simple comparison. The authors split the 1,316 treadmill-tested Norwegians four ways: high or low measured fitness, crossed with a high or low genetic score.

The groups lined up by fitness, not by genes. Those with high VO₂peak, whatever their genetic score, had a lower resting heart rate and lower BMI. They were less likely to smoke and more physically active, and they rated their own health better. They had lower systolic blood pressure, higher HDL cholesterol, lower LDL cholesterol and triglycerides, and a lower score on the Finnish diabetes risk questionnaire. Being in the high genetic group made no consistent difference to any of it.1 In the authors' words, the associations "were mostly explained by the CRF phenotype instead of the CRF genotype": by the fitness people had, not the fitness their DNA predicted.

What this does not say

It does not say genes are irrelevant to fitness. The authors are clear that twin and family studies put the heritability of aerobic fitness at 44% to 68%, and that their score captures only a sliver of that.1 Twin studies infer how much of the difference between people runs in families. A polygenic score tries to read it from your own DNA, and for fitness it cannot yet do that well. The authors conclude that genetic measures of fitness "require further development," and their limitations are worth stating plainly:

• The score explains only a small share of fitness, so a better score might find more.
• It used only common variants, and only people of European ancestry.
• This is an observational study. It shows which people were healthier, not that changing your fitness would change your health.

So the honest reading is narrower and more practical than "genes don't matter". No genetic test can currently tell you how fit you are, or much about your health, that measuring your fitness would not tell you better. If you want to know where you stand, the treadmill beats the cheek swab.

The part you can change

Measured fitness also has an advantage your genome does not: it moves when you train.

A separate 2026 paper in the same journal, "Effects of Low-Intensity Endurance Training on Aerobic Fitness and Risk Factors of Cardiometabolic Health in Working-Age Adults" by Nuuttila and colleagues, pooled 50 randomised controlled trials of healthy adults aged 18 to 65.2 Every programme in it was easy training only: below the first ventilatory threshold, or at no more than 60% of heart rate reserve. Even so, the training had a large effect on VO₂max (Hedges' g of 0.94) and smaller but real effects on blood pressure, cholesterol and triglycerides. Within that easy range, harder training went with bigger gains in VO₂max, and for most outcomes the authors found no minimum intensity below which training stopped working. They also note wide variation between studies in how much people improved.

Put the two papers side by side and the message is consistent. Whatever your genes, the fitness you actually have is what lines up with your health, and that fitness responds to training, even easy training.

We make ZonePoints, so we have a stake in this, but it is also why the app scores what it does. It does not try to estimate your potential. It measures the training: every minute above half your heart rate reserve earns zone points, and harder minutes earn more, which matches the direction Nuuttila found. The 60% ceiling in that review is the top of zone 1.

1. Joensuu L, Lukander V, Herranen P, Tynkkynen NP, Kujala U, et al.; FinnGen; Sillanpää E. "Evaluation of Genetics in the Association Between Cardiorespiratory Fitness and Health: Insights from a Genome-Wide Polygenic Score for Cardiorespiratory Fitness in the FinnGen and HUNT cohorts." Scandinavian Journal of Medicine & Science in Sports. 2026;36(5):e70291. PubMed
2. Nuuttila OP, Matomäki P, Raitanen J, Sievänen H, Vasankari T. "Effects of Low-Intensity Endurance Training on Aerobic Fitness and Risk Factors of Cardiometabolic Health in Working-Age Adults: A Systematic Review and Meta-Analysis." Scandinavian Journal of Medicine & Science in Sports. 2026;36(1):e70208. PubMed