Can Your Finger Length Predict Marathon Potential?

Take a look at your hands—specifically the lengths of your fingers. If your ring finger is noticeably shorter than your index finger, you might be more suited to endurance running than you think.

That’s the takeaway from a new study published in the American Journal of Human Biology, which analyzed data from over 5,000 individuals across 12 countries. The research focused on the 2D:4D ratio—the length of the second digit (index finger) compared to the fourth digit (ring finger). A lower ratio (meaning a relatively shorter ring finger) was associated with a higher ventilatory threshold—the point during exertion when breathing becomes labored.

This doesn’t necessarily mean you have a higher VO₂ max, the gold standard of cardiovascular fitness. But it does mean you might be able to push your body harder and longer before hitting the gasping-for-air stage—an important advantage in endurance events like the marathon.

Hormones Before Birth May Shape More Than We Think

The finger ratio in question is thought to reflect prenatal testosterone exposure, and the ring finger has more hormone receptors than the index finger. That means your fingers may quietly preserve a record of hormone levels you were exposed to in the womb—levels that could influence how your lungs, muscles, and nervous system respond to physical stress.

Even mental traits—like competitiveness or pain tolerance—could be shaped by these early hormone patterns. That could explain why people with a lower 2D:4D ratio might be better at pushing through discomfort during long training sessions or races—not just physically, but psychologically too.

A Clue, Not a Conclusion

It’s important to note the study’s limitations. Most of the participants were already fit—athletes, military recruits, or students—so this isn’t a broad sample of the general population. And the clearest links between finger length and endurance showed up in adults, likely because hormonal influences become more pronounced after puberty.

While it’s not a magic formula for predicting who will qualify for Boston or crack a sub-3:00 marathon, it’s a fascinating insight into how our bodies might be wired for performance long before we ever lace up a pair of running shoes.

And as the author herself put it: knowing your finger ratio might hint at potential—but it won’t get you across the finish line. That still takes consistent training, grit, and determination.

(For the record, she checked her own hands. Marathon running isn’t on her horizon anytime soon.)

posted Friday June 13th
by Ashley Fike | Adapted for My Best Runs – June 13, 2025