In lieu of our first official CF Endurance class, I just wanted to share some insight of mine on the topic of barefoot/minimal running. Now I don’t want to go into which choice is better for the average runner, but I would like to point out some findings I came across while researching the subject while in grad school. Check THIS out.
Kinematic Differences Between Shod and Unshod Running
Ryan R. Savard
The University of Texas at Austin
Department of Kinesiology and Health Education
ABSTRACT
The focus of this study was to compare impact forces
acting on the body between foot-striking positions
associated with “shod” (shoe) and “unshod” (barefoot)
running while also looking at differences in kinematics
associated with step length and step rate. The
subjects used in the study included 2 recreational
shod and unshod runners.
The kinematic variables under consideration were
stride rate (SR), stride length (SL), stance phase
(SP), and knee flexion angle throughout SP. The
kinetic main kinetic value measured was the horizontal
(braking and propulsive) ground reaction force (GRF)
while the vertical GRF was also examined.
A VICON 10 camera system was used in accordance
with one standard Bertec force plate to collect data
during experimentation.
Significant decreases were found in braking force and
step length while greater flexion was found in the knee
with barefoot runners. These preliminary results are
encouraging because they demonstrate that naturally
changing the foot-strike can result in a reduction of
impact forces on the body.
INTRODUCTION
There are high rates of injury in recreational and
elite runners due to repeated impact forces which
can reach two to three times the runner’s own body
weight. Recent research has been dedicated to
pinpointing conditions that put unwanted stress on the
body.
Barefoot running is becoming a more popular form
of exercise seen in recreational and elite levels and
is also emerging clinically. When running barefoot,
runners quickly refer back to a more natural mid-
foot or fore-foot strike instead of the dominant, shoe-
inducing heel-strike seen in approximately 80% of
the population. Heel-striking typically causes the
runner to make contact with the ground and initiate
the stance phase (SP) further away from the midline
of the body, ultimately increasing stride length (SL) as
seen in elite runners.
Purpose: To compare ground reaction force rates,
step length, and flexion at the knee joint of differing
foot-striking styles characteristic of shod and unshod
running.
Hypotheses:
A. There is greater braking force with the shod
runners.
B. Knee flexion is greater with unshod runners.
C. Step length is lengthened with the shod runners.
Four different subjects (3 males, 1 female) of
average age 24.25 (+/- 3.86) years took part in
this study. Kinematic markers were placed on
the subjects’ right hip, thigh, knee, tibia, ankle,
heel and second toe. All kinematic and kinetic
data was measured by the VICON system. The
subjects were asked to run on a 15-foot runway
that intersected the force plate used to measure
ground reaction forces.
After an initial warm-up period in which the
subjects were asked to go about their habitual
pre-run stretching routine, they were allowed to
practice landing on the force plate. The subjects
were then told to plant their right foot on the
force plate as naturally as possible. All trials with
“stutter-stepping” or missing of the force plate were
discarded.
Each subject completed at least three trials that
were then compared and analyzed.
RESULTS
(see poster for graphs)
These graphs show the projection of vertical GRF across the entirety of SP in all
shod and unshod subjects. The heel-strike is prevalent in the two shod runners
while not so much is the unshod runners.
DISCUSSION
Results show that the braking force, elicited from initial
impact to approximately mid-SP had a greater average
magnitude and peak value in shod runners than in
unshod runners proving the first hypothesis. The GRF
curves revealed that the main difference between heel
and mid-foot striking was the absence (or only a slight
trace) of an initial vertical impact peak in mid-foot
landing. Since braking force is contributed largely to the
heel strike, it is clear that the heel strike is a major
contributor to horizontal impact forces on the body.
Knee-flexion, while hypothesized to have been greater
in unshod runners was actually overall greater in shod
runners. This could be because of the difference in heel
height due to the running shoe cushioning that was
unaccounted for prior to experimentation or differences
in velocity. As hypothesized, SL was larger in shod
runners because of the heel-strike and associated
capability of the runner to plant farther away from the
mid-line of the hip. Since the SL was shorter for the
unshod runners, step cadence is increased in order to
maintain equal velocities. At higher rates of step
turnover along with more mid-foot striking, it is believed
that there will be less stress on the body meaning lower
rates of injury due to a more natural running gait.
Further research is needed to acquire stress levels
on separate joints (most importantly the knee) to
see if barefoot running does in fact truly aid in injury
prevention.
REFERENCES
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Sports Exerc. 22:669-677, 1990.
Cavanagh, P.R. and M. LaFortune. Ground reaction forces in
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Dufek, J.S. and B.T. Bates. The evaluation and prediction of impact
forces during landing. Med. Sci. Sports Exerc. 22:370-377, 1990.
James, S.L., B.T.Bates, and L.R. Osternig. Injuries to runners. Am.
J. Sports Med. 6:40-50, 1978.
Nigg, B.M., G.K. Cole, and G.P. Brüggemann. Impact forces during
heel-toe running. J. App. Biomech. 11:407-432, 1995.
Williams, K.R.and P.R. Cavanagh. Relationship between distance
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