Take a second and look at your hands. Specifically, compare your ring finger to your index finger. If your ring finger’s a little shorter, congratulations: you might be biologically engineered for endurance running.
A new study in the American Journal of Human Biology looked at data from over 5,000 people across 12 countries and found that finger length—specifically the 2D:4D ratio—has ties to athletic performance. People with shorter ring fingers relative to their index fingers (lower 2D:4D ratios) had a higher “ventilatory threshold,” which means they could exercise harder before their breathing turned into gasping.
They didn’t necessarily have higher VO₂ max scores (the classic gold standard of cardio fitness), but they could push through longer before their bodies hit the panic button.
Your Finger Length Might Predict If You Could Finish a Marathon
So, what does finger length have to do with stamina? It starts before you’re even born. This ratio is thought to reflect prenatal testosterone exposure. Since the ring finger has more hormone receptors than the index finger, it tends to be shaped more by fetal hormone levels.
That early testosterone doesn’t just affect finger length—it might shape everything from how your lungs respond to stress, to your muscles’ ability to use oxygen, to how your nervous system deals with fatigue.
Your Finger Length Might Predict If You Could Finish a Marathon
Researchers from the University of South Australia and the University of North Dakota say that even mental traits tied to competition and pain tolerance could be influenced by prenatal hormone levels. That could mean that people with lower 2D:4D ratios might also handle discomfort better during grueling runs or workouts—not just physically but psychologically, too.
There are caveats. The participants in these studies weren’t random—they were mostly athletes, military recruits, or students, meaning they already had above-average fitness. And the link was strongest in adults, suggesting these hormonal fingerprints show up more clearly after puberty. While this isn’t a crystal ball for your 5K time, it is a strange, fascinating peek at how your body might be wired.
Still, knowing how you’re built is just one piece of the puzzle. What really matters is what you do with it. Finger length might hint at something about your endurance potential—but it won’t carry you across a finish line. Training and hard work go a long way.
And for the record, I just checked my hands. I won’t be running a marathon anytime soon.
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