Japan might not have the same monopoly on distance running as Kenya or Ethiopia, but they’re doing something right. At last month’s Tokyo Marathon, nine Japanese men finished under 2:10—a feat that only 11 American men have ever accomplished. And if these impressive runners have anything in common, a recent study suggests, it might be their forefoot bones.
Researchers at the Faculty of Sport and Health Science at Ritsumeikan University in Japan took 45 trained endurance runners and 45 untrained subjects and measured the lengths of their forefoot bones—specifically the metatarsals and phalanges of their right feet—using an MRI. They then normalized those measurements using the complete length of the foot (since a person with a longer foot probably has correspondingly longer forefoot bones) and compared the endurance runners’ bones to the untrained group.
They found that the endurance runners had longer forefoot bones in both the big and second toes (by about 1 percent and 0.5 percent, respectively) than their untrained counterparts—a trait that matches the researchers’ earlier findings when they looked at the forefoot bones of sprinters vs. non-sprinters. In both studies, they also found that longer forefoot bones correlated with faster running speeds among the trained runners, although here the studies’ findings diverged: endurance runners who reported faster 5K times had longer big toe forefoot bones, whereas sprinters who reported faster 100 meter times had longer second toe forefoot bones.
More From Runner's World
The finding that runners have longer forefoot bones doesn’t surprise Dr. Ethan Ciment, a sports medicine podiatrist at Chelsea Foot and Ankle in New York City. He generally observes that his running clients, especially sprinters, are taller and lankier than his other clients.
“If you’re built for running, it makes sense that your forefoot is built for this, too,” he told Runner’s World.
In fact, a number of studies have found correlations between physical body structures and running speed. The same group of Japanese researchers found that runners who had better running economy (i.e., those who needed to use less energy to maintain the same speed) also had longer Achilles tendons. Meanwhile, a study by Robert Trivers found that Jamaican children who had more symmetrical knees grew up to be better adult sprinters.
Yet as interesting as these findings are, what do they mean for the average runner?
“Running is slightly easier for people with certain physical traits,” Ciment said. “This isn’t surprising. People who are born genetically taller make better basketball players.” Yet knowing this information about yourself doesn’t mean you can do much with it, because anatomically, you're stuck with whatever bones you have.
“There is no evidence that running can actually lengthen your bones,” said Ciment. He went on to debunk the misconception that running makes your feet bigger. “As we age, our feet splay because of the cumulative effect of weight bearing and a certain amount of ‘stretch’ that happens to the ligaments that hold the joints and bones of our feet together. So it’s quite possible that the more higher-impact activities like running that an individual does, the greater the impact and the more accelerated this splaying process.”
In the end, while they are interesting, the findings of this study can’t inform your behavior, and you can’t change the length of your bones. But not to worry; no matter the length of your forefoot bones, other overall factors like weight and general health—which you can affect—are far more predictive of your ability to run fast.
Allison Goldstein is a freelance writer and editor who is endlessly fascinated by the scientific “why” of things. When not writing or reading, she can be found running, baking, or petting her cat, Tabouli.