KINEMATICS - Biomechanics and Motor Control of Human Movement - page 71

Toe Marker

3200

1600

0

− 1600

2 nd Order Filter
f cx 6.0 Hz
Filtered Data
Raw Data

− 3200

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Time (s)

Figure 3.19 Horizontal acceleration of the toe marker during normal walking as cal-
culated from displacement data from television. The solid line is the acceleration based
on the unprocessed “raw” data; the dotted line is that calculated after the data has been
filtered with a fourth-order zero-lag low-pass digital filter. (Reproduced by permission
from the Journal of Biomechanics. )

Figure 3.20 Plot of the residual between a filtered and an unfiltered signal as a function
of the filter cutoff frequency. See text for the interpretation as to where to set the cutoff
frequency of the filter.