Curve at tip of shoes eases movement but may lead to weaker muscles,
problems
Toe springs in shoes may come at a cost

Date:
September 17, 2020
Source:
Harvard University
Summary:
The scientists found that the more curved a toe spring is, the less
power the foot inside the shoe has to exert when pushing off from
the ground while walking. That means foot muscles are doing less
work, and this, the researchers hypothesize, may have consequences
such as less endurance and make people more susceptible to medical
conditions like plantar fasciitis.



FULL STORY ==========================================================================
The toe of most shoes, especially sneakers, bends ever so slightly upward.

While that curve, called a toe spring, can make stepping more comfortable
and easier, it may also weaken feet and potentially open them up to some
common (and painful) foot-related problems.


========================================================================== That's the conclusion reached by Harvard evolutionary biologist Daniel E.

Lieberman, his former undergraduate student Oliver B. Hansen '19,
and two former post-doctoral researchers, Freddy Sichting and Nicholas
B. Holowka, who studied toe springs and their effect on the biomechanics
of walking. Their research is detailed in a new edition of Scientific
Reports.

The scientists found that the more curved a toe spring is, the less power
the foot inside the shoe has to exert when pushing off from the ground
while walking. That means foot muscles are doing less work, and this,
the researchers hypothesize, may have consequences.

"It stands to reason that if the foot muscles have to do less work,
then they're probably going to have less endurance given that many
thousands of times a day you push off on your toes," said Lieberman,
the Edwin M. Lerner II Professor of Biological Science and senior author
on the paper.

The researchers say this potential weakness could make people more
susceptible to medical conditions like plantar fasciitis -- a common,
hard to repair, and painful inflammation of the thick, web-like band of
tissue that connects the heal bone to the toes.

"One of the biggest problems in the world today of people's feet is
plantar fasciitis," Lieberman said. "We think that what happens is
that people are relying on their plantar fascia to do what muscles
normally do. When you get weak muscles and the plantar fascia has to do
more work, it's not really evolved for that, and so it gets inflamed."
The scientists say their next step is to validate their hypothesis in
future studies.



========================================================================== "From an evolutionary perspective, wearing modern shoes that have arch supports, cushioning, and other supportive features is a very recent phenomenon," said Sichting, who's now a professor of human locomotion at Chemnitz University of Technology in Germany and served as the paper's
first author. "Several lines of evidence suggest that weak foot muscles
may be partly a consequence of such features. In our research, we were interested in a nearly ubiquitous element of modern shoes that has not
been studied before: the upward curvature at the front of the shoe."
He means the toe spring, of course, which constantly flexes the toe
box above ground and has become nearly ubiquitous in modern footwear, especially in athletic shoes.

The project started after Sichting and Lieberman met at a conference
in Boston, and (of course) went for a run by the Charles River where
they talked about foot biomechanics and plantar fasciitis. That led to
Sichting coming to Lieberman's Skeletal Biology and Biomechanics Lab in
2018 to work on the project with Holowka, who's now an assistant professor
of anthropology at the University of Buffalo, and Hansen, a former
Crimson rower who graduated with a concentration in human evolutionary
biology. Hansen worked on the paper as part of his senior honor's thesis.

In the experiment, 13 participants walked barefoot and in four pairs of
custom- made sandals on a specially designed treadmill. The treadmill is equipped with force plates and an infrared camera system to measure how
much power is put into each step. The sandals each had varying degrees of
toe spring angles - - from 10 degrees to 40 degrees. They were designed
to mimic the stiffness and shape found in commercially available shoes.

It became clear while analyzing the data that the propulsive force
generated by the metatarsophalangeal or MTP joints (that's where the
toes connect to the rest of your foot bones) decreases as the curve of
the toe spring on the specially-made sandals increased. MTP joints are
one of the key features that have evolved so that humans can walk and
run on two feet so effectively and efficiently.



==========================================================================
"By reducing moments at the MTP joints, toe springs likely relieve the intrinsic foot muscles of some of the work necessary to stiffen these
joints," the researchers wrote in the study. "These small differences
in muscle work likely add up to substantial differences over time when considering that the average individual in industrialized countries takes
4,000 to 6,000 steps per day. Thus, habitually wearing shoes with toe
springs could inhibit or de- condition the force generating capacity
of intrinsic foot muscles." The researchers make clear in the paper
that more research is needed on all fronts and that their study does
not directly link toe springs with plantar fasciitis or other common
foot problems. The study also included only habitual shoe users whose
feet may already have been adapted to shoes with toe springs.

"This study isolated just one element of our shoes," said Hansen. "More research is needed to investigate how toe springs interact with other
elements of shoes such as stiff soles or cushioning. This could give us
a more complete picture of how shoes affect our biomechanics." Still,
they say the unrecognized biomechanical effects of toe springs on foot
function merits further consideration.

"Walking in shoes with comfortable features such as a toe spring has
its costs," Sichting said.

Don't expect toe springs to go anywhere anytime soon, though.

"We like comfort," Lieberman said. "That's why we sit in chairs and
take elevators."

========================================================================== Story Source: Materials provided by Harvard_University. Original written
by Juan Siliezar.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Freddy Sichting, Nicholas B. Holowka, Oliver B. Hansen, Daniel E.

Lieberman. Effect of the upward curvature of toe springs on walking
biomechanics in humans. Scientific Reports, 2020; 10 (1) DOI:
10.1038/ s41598-020-71247-9 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200917181249.htm

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