Article

Center of pressure (COP) trajectories summarize the complex mechanical
interaction between the foot and a contacted surface. Each trajectory itself is
also complex, comprising hundreds of instantaneous vectors over the duration of
stance phase. To simplify statistical analysis often a small number of scalars
are extracted from each COP trajectory. The purpose of this paper was to
demonstrate how a more objective approach to COP analysis can avoid particular
sensitivities of scalar extraction analysis. A previously published dataset
describing the effects of walking speed on plantar pressure (PP) distributions
was re-analyzed. After spatially and temporally normalizing the data, speed
effects were assessed using a vector-field paired Hotelling's T2 test. Results
showed that, as walking speed increased, the COP moved increasingly posterior at
heel contact, and increasingly laterally and anteriorly between approximately 60
and 85% stance, in agreement with previous independent studies. Nevertheless, two
extracted scalars disagreed with these results. Furthermore, sensitivity analysis
found that a relatively small coordinate system rotation of 5.5 degrees reversed
the mediolateral null hypothesis rejection decision. Considering that the foot
may adopt arbitrary postures in the horizontal plane, these sensitivity results
suggest that non-negligible uncertainty may exist in mediolateral COP effects. As
compared with COP scalar extraction, two key advantages of the vector-field
approach are: (i) coordinate system independence, (ii) continuous statistical
data reflecting the temporal extents of COP trajectory changes.
CI - Copyright (c) 2014 Elsevier B.V. All rights reserved.

Langue : ANGLAIS