Figure 2 percentage of runners with each foot strike

Figure 2. Percentage of runners with each foot strike
according to type of footwear. FFS, forefoot strike; MFS,
midfoot strike; RFS, rearfoot strike. * P = 0.03 vs barefoot
and minimalist footwear.

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although both did yield significantly shorter GCTs than did
traditional shoes (Figure 3).
Stride Cadence and Knee Angle
Both SC and KA tended to decrease as cushioning increased
(Figures 4 and 5, respectively). However, there was no
significant difference among the groups with respect to SC
( P = 0.20) or KA ( P = 0.37).
Multivariable Analysis
Considering all running biomechanics simultaneously in a
multivariable model, only GCT differed between the 3 groups.
With respect to individual comparisons in the adjusted model,
GCT in traditional shoes was significantly higher than in both
minimalist shoes ( P = 0.020) and in the socked condition
( P = 0.023).
DISCUSSION
Compared with traditional shoes, minimalist shoes and barefoot
(socked) running facilitated a midfoot or forefoot strike in the
group of experienced high school runners. Minimalist shoes and
socked running resulted in a shorter GCT than traditional
running shoes. Minimalist shoes also approximated socked
footwear in all 4 measures of running biomechanics: foot strike,
GCT, SC, and KA at ground contact.
Taken together, these findings suggest that minimalist shoes
and barefoot running are associated with improved running
biomechanics when compared with traditional shoes by certain
measures. While we did not measure VO
2
max, each of our
biomechanical outcome variables has been associated with
running efficiency.
5,7,8
Hasegawa et al
7
demonstrated that MFS or
FFS leads to increased running efficiency. In addition, a shorter
GCT correlates with a higher cadence, which may lead to
greater running efficiency.
7
Heiderscheit et al
8
found that
increases of 5% to 10% in SC can substantially reduce the
loading on the hip and knee joints. Finally, greater flexion can
reduce the peak vertical ground reaction force, suggesting that
increased KA at ground contact correlates with improved
running efficiency.
5
These correlations between biomechanics
and efficiency suggest that minimalist shoes and barefoot
footwear may improve running efficiency.
The analysis of biomechanical outcomes supports previous
work in the field.
7,10,11
Across all trials and regardless of the type
of footwear being tested, the majority of runners (64.4%) used
an RFS in this study; other studies, conducted both in road
races
7,10
and over multiyear periods,
4
suggest this finding.
Habitually shod American adults RFS 100% of the time, while
habitually barefoot American adults RFS only 25% of the time.
11
While several studies suggest improved biomechanics and
efficiency with barefoot running and/or minimalist
footwear,
6,11,13
the question of whether these perceived
advantages confer protection from injury remains
Figure 3. Mean ground contact time (GCT; in milliseconds)
according to type of footwear. Error bars represent ±1 SD.