#Ask Well: Does Foot Size Affect Running?

By GRETCHEN REYNOLDS

November 6, 2015

How does foot size affect running efficiency? Is there an advantage that counteracts the additional weight of a larger foot?

Running efficiency, like fuel economy in cars, reflects how well your body uses energy at any given speed and can be affected by many traits, including body weight and how it is distributed.

In general, according to a comprehensive 2004 overview of factors that influence running economy, carrying mass distally increases the aerobic demand of running to a greater extent than carrying mass closer to the center of mass. In other words, extra weight around your middle will not slow you as much as the same weight on your feet.

Specifically, the researchers wrote, adding about two pounds of additional weight to your body s core could reduce your running efficiency by about 1 percent; adding that same amount to your feet likely drops your efficiency by around 10 percent, which is a good reason to look for lightweight running shoes.

Of course, even a sizable foot encased in a heavy shoe is unlikely to weigh two pounds more than the typical foot.

An average male human foot has a mass of about 1,000 grams, or 2.2 pounds, said Rodger Kram, a professor of integrative physiology at the University of Colorado at Boulder who studies the biomechanics of running.

Add 100 grams, or about 3.5 ounces, to that foot, which would be the equivalent of about a shoe size or two, and you would probably lose about 1 percent in efficiency, he says, compared with someone whose foot size is average.

So the real-world decline in efficiency among runners with oversize feet is small, he said.

At the same time there do not seem to be any offsetting advantages to large feet for runners. (This is not the case for swimmers who can flap large feet like flippers Michael Phelps reportedly wears a size 14 shoe.) Large feet have not been shown to help runners push off, for instance, or otherwise propel themselves forward more powerfully.

But in a very close sprint finish, a larger foot conceivably might enable you to win by a toe over a daintier-footed opponent.