Page 107 - Journal of Special Operations Medicine - Spring 2016

rearfoot strike pattern, whereas 57% were using a fore- runners were filmed as they ran on either a treadmill or
foot strike pattern. These investigations indicate that a track, and their foot strike patterns were assessed on
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over a relatively short time, most runners adapting to viewing the film. There were 16 forefoot strikers (31%)
minimalist shoes adopt a forefoot strike pattern. and 36 rearfoot strikers (69%). Injuries were recorded
by an athletic trainer/physical therapist with follow-up
Figure 3 shows vertical ground reaction forces for fore- consultations with physicians. A complex injury severity
foot, midfoot, and rearfoot ground strikes. 1,16,17 Vertical score was developed based primarily on the number of
ground reaction forces are the vertical forces of impact days of activity restriction and the types of restrictions.
on the ground—in this case (Figure 3), measured in terms Injury rates by foot strike patterns are shown in Figure
of body weight. All foot strike patterns have a similar 4. At the end of the study period (about 2 years), the
peak impact force (about 2.5 times body weight). How- moderate to severe overuse injury rate was higher for
ever, the rearfoot strikers have a greater rate of force the rearfoot strikers, but there was no difference by foot
development (called the loading rate) and an initial peak strike pattern for traumatic injuries.
(at about 1.5 times body weight) that precedes the peak
impact force. Note that midfoot strikers have a loading Figure 4 Moderate to severe overuse and traumatic injury
rate that lies between rearfoot and forefoot strikers. 1 incidence by foot strike patterns among Harvard University
runners.
Figure 3 Vertical ground-reaction forces (VGRF) for rearfoot
strikers (RFS), midfoot strikers (MFS), and forefoot strikers
(FFS) wearing running shoes. The line showing two peaks is
for RFS. Note that loading rates (slopes of initial VGRF)
are highest in RFS, lower in MFS, and lowest in FFS. BW,
body weight.

Data from Daoud et al. 18

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Another study examined whether transitioning individ-
uals from a rearfoot to forefoot strike pattern might af-
fect chronic exertional compartment syndrome (CECS).
In CECS, exercise results in the swelling of the lower leg
Data from Altman and Davis. 1 reduction in blood flow, with severe pain and disabil-
that increases intramuscular pressures and results in a
ity. Ten military personnel at the US Military Academy
(West Point, New York) who had CECS and were sched-
uled for surgery to alleviate this condition were enrolled
in a 6-week training program that involved transitioning
In summary, the major biomechanical differences be- from a rearfoot to a forefoot strike pattern. Six weeks
tween running in conventional versus minimalist shoes after the start of the program, the runners had consid-
appear to be a lower energy cost of minimalist shoes, erably reduced lower-leg compartment pressures during
associated with the lighter shoe weight; and the gradual running, reported less pain on running, and had consid-
adoption of a forefoot or midfoot strike pattern. The erably increased their running distance. One potential
forefoot strike typical of runners wearing minimalist reason for this reduction in CECS could be the reduced
shoes generally results in a lower loading rate when the requirement to dorsiflex the foot in preparation for heel
foot hits the ground. strike. This, in turn, would unload structures that may
have been chronically loaded over years of exposure to
heel strike running. No patient required surgery after
Injuries and Foot Strike Patterns
the program and, 1 year later, the patients reported their
There are some limited data on associations between foot lower leg function remained considerably improved
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strike patterns and injuries. One study examined this compared with before the training program.
association in 52 Division I National Collegiate Athletic
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Association runners at Harvard University. The run- A final study examined foot strike patterns and self-
ners competed in distances from 800m to 10km and ran reported injuries among 341 male Soldiers in the 1-66th
an average of about 71km/week (44 miles/week). The Armor Regiment stationed at Fort Carson, Colorado.

Injuries and Footwear 91