2.2.3. Posture assessment
These assessments were performed while individuals stood on a
Bertec balance plate (model BP6040, sample rate: 100 Hz). This
device provides information about center of pressure (COP) motion in
the anterior–posterior (AP) and medio-lateral (ML) direction.
Postural motion was collected for the following conditions: 1) eyes
open/firm surface, 2) eyes closed/firm surface, 3) eyes open/foam
surface, and 4) eyes closed/foam surface. The foam surface was 15-
cm-thick and of medium density. For these assessments, COP data
were filtered using a second-order low-pass Butterworth filter (cutoff
frequency 50 Hz). The dependent measures determined for postural
sway included; total path length, mean COP velocity, mean, SD, and
range of COP motion in the ML and AP directions. Analyses of the COP
data were performed using Matlab software (Mathworks R14).