09/22/2020 Kevin A. Kirby, DPM
OR Podiatrist Comments on Toe Spring Running Shoes
It appears as if the “Barefoot Professor”,
Daniel Lieberman, PhD, is at it again. As some
of you may remember, Dr. Lieberman was at the
forefront of the failed Barefoot Running and
Minimalist Running Shoe Fads a decade ago when
he, and his coauthors, suggested that midfoot
and forefoot striking running would help
prevent injuries in runners in his questionable
study on barefoot running (Lieberman DE,
Vankadesan M, Werbel WA, Daoud AI, D’Andrea S,
Davis IS, Mang’Eni RO, Pitsiladis Y: Foot
strike patterns and collision forces in
habitually barefoot versus shod runners.
Nature 463: 531-536, 2010).
Lieberman then became to be known as the
“Barefoot Professor” in the barefoot-running-
crazed media of the time. His lab at Harvard
was funded for many years by Vibram FiveFinger,
a company which later on agreed to a class-
action settlement for $3.75 million due to the
false health claims Vibram FiveFinger had made
for years about their five-toed shoes. These
five-toed shoes were later found to cause
significant increases in MRI-determined bone
marrow edema in the feet of the 36 subjects,
compared to those subjects running in more
conventional cushion-soled running shoes, over
a 10-week period. Soon after this excellent
study was performed by Ridge et al, the bubble
burst on the Barefoot Running and Minimalist
Running Shoe Fads, and these unfortunate fads
that injured so many runners soon swirled into
oblivion (Ridge ST, Johnson AW, Mitchell UH et
al: Foot bone marrow edema after 10-week
transition to minimalist running shoes. Med Sci
Sports Exerc, 45(7):1363-1368, 2013).
Now, years after the Barefoot Running and
Minimalist Running Fads died a slow death,
Lieberman is back in the news again. Lieberman
and coauthors just had another study published,
again on the Nature website, which studied the
effects of walking in 10 – 40 degree toe-spring
sandals, with only 13 subjects included in the
study. These researchers studied only young
(mean age = 22 y/o) uninjured adults, not
subjects with plantar fasciitis. Lieberman’s
research did not measure plantar intrinsic
muscle strength, did not measure plantar
intrinsic muscle volume, and did not perform
electromyography of the plantar intrinsic
muscles during walking. They only studied the
motion patterns and kinetics of walking gait in
their subjects in different sandals. '
Somehow, from the results of their study,
Lieberman and coauthors then concluded that the
ubiquitous toe-spring angle, present in most
modern shoes, caused plantar intrinsic muscle
atrophy which could lead to plantar fasciitis
(Sichting, F., Holowka, N.B., Hansen, O.B. et
al. Effect of the upward curvature of toe
springs on walking biomechanics in humans. Sci
Rep 10, 14643 (2020).
https://doi.org/10.1038/s41598-020-71247-9).
This study is a classic example of how
researchers can, willingly, overstate the
conclusions of their research results. Without
measuring plantar intrinsic muscle activity,
without measuring plantar intrinsic muscle
volume in control and experimental groups, and
not studying the incidence of plantar fasciitis
in control and experimental groups, Lieberman
and coauthors were only guessing that toe-
spring in shoes could cause intrinsic muscle
atrophy and plantar fasciitis. They had
absolutely no data from their experiment that
would allow them to make such a big leap of
faith otherwise.. As such, this study and its
conclusions should be viewed with extreme
caution by scientific-minded podiatrists.
Kevin A. Kirby, DPM, Sacramento, CA
