292
C. Drug˘ a et al.
3 Results and Discussion
The next step was to create a graph for each type of measurement (Table 1) to track
the amplitude variation of the center of pressure. In the table below, we can see the
amplitudes for each type of measurement and each subject.
According to other studies [9], in an orthostatic position, the center of pressure
varies in an anterior–posterior direction considering the base of support, but this
study shows a greater variance in the left–right direction possibly due to the way the
vibrations were sent to the body in the frontal plane, not in the sagittal plane.
The results (Figs. 3 and 4) indicate that each subject has a personal evolution
although we tried to find a normalized group of subject (this reflects in the small
number of subjects taken into account). Amplitude was measured between the
maximum and the minimum value on the X-axis and the Y-axis of the center of
pressure. In the figures below, it can be seen the dispersion of these values. The
values of the center of pressure are obtained from the software in two columns X and
Y relative to time.
The most important ratio of the center of pressure dispersion (Figs. 5 and 6) can be
seen in the case of subject 2, in frontal plane, Y-axis, where the amplitude increases
for EC and after WBV in relation to EO situation.
Table 1 Amplitude of center of pressure on X-axis (Anterior–posterior direction) and Y-axis (Leftright direction) for every subject and experimental step
Experimental steps
Subject
Amplitude
Amplitude
X[m]-Antero-posterior
Y[m] Left-right
With EO
1
0.037
0.028
2
0.021
0.012
3
0.025
0.012
4
0.028
0.0128
With EC
1
0.013
0.014
2
0.0155
0.0175
3
0.025
0.0165
4
0.031
0.013
After exposure to WBV
1
0.028
0.03
2
0.02
0.034
3
0.031
0.021
4
0.043
0.021