0.58
body weights
impact force for
barefoot runners
who forefoot strike
1.74
body weights
impact force for
shod runners who
strike heel first
famed endurance runners who grew up
not wearing shoes. The researchers found
that, as expected, these runners typically
strike the ground with either the forefoot
or the midfoot before lowering the heel.
In contrast, shod runners in the United
States typically landed on the heel first.
“This study is unique in that they actually went and found people who have
been running barefoot and are world
renowned as barefoot runners,” says bio-mechanist Reed Ferber of the University
of Calgary in Canada. Previous studies
focused on people asked to run barefoot
in laboratory experiments, he says.
In further experiments at Harvard,
Lieberman’s team used a scale called a
force plate to precisely measure force
from running. The average initial impact
force in habitually barefoot U.S. runners
who land on the forefoot first is about one-
can cause runners to flex the foot in a way
that creates more mincing steps, shorten-
ing the stride. A 6-foot, 2-inch–tall man
would have to take 7,500 more steps to
finish a marathon if running barefoot
than if with shoes, because
the length of the stride is
shorter, Ferber says. “You
could argue that if he’s going
to take 7,500 more steps he’s
more likely to get an injury.
But you could also argue that
all those steps don’t have that
impact peak, so that might be
injury protective.”
Lieberman agrees that it’s
too early for people to throw out their
fancy shoes. “It’s too complex a question,
as it depends on one’s feet, condition, abil-
ity to forefoot or midfoot strike, which
takes more calf muscle, and so on.”
third the force in shod U.S. runners who
land on the heel, the researchers found.
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February 27, 2010 | SCIENCE NEWS | 15
