| dc.description.abstract | The primary purpose of the study was to calibrate and validate a shoe impact
machine designed to replicate heel strike impact force produced during running.
The secondary purpose was to compare impact force attenuation magnitudes of
four selected brands of running shoes. A major focus of footwear research has
been on heel strike impact force due to its link to pain and injury (Frederick,
1984; Nigg, 1986; Nigg, Cole, Bruggemann, 1995). However gross participant
gait variation during testing has made it difficult to consistently measure and
compare impact forces between shoes. To correct for this variance, an ideal
testing method would be mechanical simulation of heel strike to validate actual
human response (Frederick, 1986, B). Eleven healthy male participants
performed 25 trials of barefoot force platform running at 3 m sec. Using the
vertical ground reaction force (VGRF) curves generated, mean barefoot impact
force values were calculated. An impact machine was calibrated to the mean
barefoot impact force scores produced from the force platform running for each
participant. The impact machine then duplicated 5 heel strikes using four
selected brand name running shoes. All impact force data was represented in
percent body weight to normalize each shoe’s performance magnitude. Impact
machine validity was established through a paired sample t-test. No significant
differences were found between barefoot running and the barefoot impact
machine results where, t (11) = .222, p > .05. The results demonstrate that the
impact machine generated equivalent impact force results compared to running
over a force platform using multiple trials. A One-Way analysis of variance (ANOVA) revealed significant differences between midsole attenuation rates
between the four pairs of running shoes; where, F(3,40) = 5.766, p < .05.
Scheffe’s post hoc comparison determined that Nike was significantly different
from Adidas and New Balance. No other significant differences were found. Nike
had the greatest attenuation rate absorbing 7.9% of the impact force per step
followed by Saucony 6.5%, then Adidas 4.6%, and finally New Balance 4.5%. | |
