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COMPARISON OF TIBIAL STRAINS AND STRAIN RATES IN BAREFOOT AND SHOD RUNNING
Allison R. Altman, Irene S. Davis
Each runner underwent a standard motion analysis
data collection session. Shod rearfoot striking, shod
forefoot striking, and barefoot running were
collected during overground running at 3.5 m/s. Leg
and torso kinematic data were sampled at 240 Hz.
Ground reaction force, along with EMG data....
The tensile and compressive strains were similar
between the three conditions
Strain rate was highest in the forefoot strike
condition in both tension and compression (Figure
3). We expected the strain rate to be highest in the
rearfoot strike condition due to the local maxima
observed around the impact peak of the vertical
ground reaction force (Figure 2). However, it is
plausible that the increased strain seen in the
forefoot strike may be a result of muscular
While peak strains were similar between conditions,
strain rates were highest in the forefoot condition
due to muscular contributions. It may be that
barefoot running requires less muscle force than the
shod forefoot condition due to the lower inclination
angle of the foot at footstrike.
Tibial Stresses in Habitual and Converted Forefoot and Rearfoot Strike Runners
Derrick T, Edwards W, Rooney B
In this paper we used a series of models to
estimate the tibial stresses in a group of habitual
forefoot runners (FF) running with a forefoot
running style (ff) and a rearfoot running style (rf)
and compared them to a group of habitual rearfoot
runners (RF) running with both styles.
Although ff running reduces the vertical impact
peak relative to rf running, it requires greater
plantar flexor activity. Since the gastrocnemius
muscle crosses the knee joint, it requires greater
cocontraction at the knee to create a similar net
moment. Even though the increased muscle forces
work to reduce the total moment acting at the crosssection
(Figure 1), it is not enough to reduce the
stresses because of the increased compressive force
caused by the muscles. This resulted in increased
stress in 3 of the 4 quadrants.
As a potential means to decrease their risk of injury, many runners are transitioning into barefoot running. Habitually shod runners tend to heel-strike (SHS), landing on their heel first, while barefoot runners tend to mid-foot or toe-strike (BTS), landing flat-footed or on the ball of their foot before bringing down the rest of the foot including the heel. This study compared muscle activity, tibial shock, and knee flexion angle in subjects between shod and barefoot conditions. Eighteen habitually SHS recreational runners ran for 3 separate 7-minute trials, including SHS, barefoot heel-strike (BHS), and BTS conditions. EMG, tibial shock, and knee flexion angle were monitored using bipolar surface electrodes, an accelerometer, and an electrogoniometer, respectively. A one-way MANOVA for repeated measures was conducted and several significant changes were noted between SHS and BTS, including significant increases in average EMG of the medial gastrocnemius (p = .05), average and peak tibial shock (p < .01), and the minimum knee flexion angle (p < .01). Based on our data, the initial change in mechanics may have detrimental effects on the runner. While it has been argued that BTS running may ultimately be less injurious, these data indicate that habitually SHS runners who choose to transition into a BTS technique must undertake the process cautiously.