Page 109 - Journal of Special Operations Medicine - Spring 2016

rates are related to running injuries. This lack of clar- A study from Brigham Young University, by Ridge et
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ity results from the limitations of the cited retrospective al., compared bone stress injuries in runners using
studies, the mixed results from these retrospective inves- conventional versus minimalist shoes. Runners who
tigations, and the fact that the only prospective study participated in this study had never used minimalist
found that runners with higher loading rates were less shoes, were injury free, and ran an average of 15–30
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likely to be injured. However, it is notable that higher miles/week in the 6 months before the study. Investi-
impact forces are associated with greater bone mineral gators randomized subjects into two groups: one that
content and density, 30–32 and this finding is consistent continued running in conventional shoes for 10 weeks
with investigations suggesting that regular short bouts (n = 17) and one that gradually transitioned into a Vi-
of relatively high levels of repeated loading of bone bram 5-Fingers shoe (Vibram SpA; http://www.vibram
strengthen the bone tissue in such a way that it is resis- .com) over the 10-week period (n = 19). The transition
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tant to damage from future repeated loadings. Future program in the minimalist shoe group involved progres-
studies that prospectively examine loading rates and sively increasing the participant’s running distance in
subsequently track injuries in larger groups of runners the Vibram shoe while decreasing mileage in their usual
are necessary to determine associations between loading conventional shoe. Bone stress injuries (i.e., bone mar-
rates and running injuries. row edema determined by magnetic resonance imaging
[MRI]) were assessed at the start of the study and after
10 weeks. The results are shown in the center left of
Injuries in Minimalist Versus Figure 6. MRI changes indicative of bone stress injuries
Conventional Running Shoes
were almost nine times higher in the minimalist foot-
To date, there are at least four studies that have com- wear group after 10 weeks.
pared injury rates in minimalist versus conventional run-
ning shoes. The earliest of these (Goss et al. ) recruited Another study, conducted in Vancouver, Canada, by
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2,509 runners from universities, running websites, and Ryan et al., recruited runners through newspapers and
personnel at Fort Sam Houston, Texas. Participants who word of mouth. Runners who participated in the study
were 18–50 years old and ran at least 6 miles per week were 19–50 years old, had at least 5 years of running
were simply asked to complete a questionnaire. Runners experience, had been regularly running 20–40km/week
were included in the analysis only if they reported that (12–25 miles/week) for the past 6 months, and had no
they had not changed their foot strike pattern or shoe injuries at the time of the study. Runners were random-
type in the past year, if they were sure of their foot strike ized to three groups: one assigned a conventional shoe
pattern and shoe type, and if they completed a question (Nike Pegasus 28; Nike Inc, www.nike.com), another
involving injuries. There were 904 runners who met all assigned a cushioned minimalist shoe (Nike Free 3.0),
these criteria and, thus, were included in the study. Run- and a third assigned a barefoot minimalist shoe (Vibram
ners who reported wearing conventional running shoes 5-Fingers). Runners then participated in a supervised
were 3.4 times more likely to report injuries compared 12-week training program in which they gradually in-
with those wearing minimalist shoes, as shown on the creased running volume in preparation for a 10km race.
left in Figure 6. They also gradually increased the amount of time wear-
ing their assigned shoes from 19% of training time in
Figure 6 Results of four studies 34–37 that compared injury week 1 to 58% in week 12. Injuries experienced in the
incidence in conventional versus minimalist running shoes. three groups during the 12 weeks are shown on the cen-
C, conventional shoes; M, minimalist shoes; MB, minimalist
barefoot shoes; MC, minimalist cushioned shoes. ter right in Figure 6. If we combine the results from the
two minimalist shoes, runners in conventional shoes
tended to have fewer injuries than did runners in the
two combined minimalist groups (13% versus 28%;
p = .08). The authors concluded that those new to mini-
malist footwear had higher injury risk and that caution
should be exercised among those new to this type of
footwear.

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The final study, by Grier et al., , examined injuries in the
4th Brigade of the 4th Infantry Division at Fort Carson,
Colorado. The study involved 1,332 male Soldiers who
either wore conventional running shoes or minimalist
shoes. Shoe models and brands were recorded by the
investigating team, and a Soldier was included in the
study only if he indicated that the shoe examined was

Injuries and Footwear 93