Biomedical Engineering Reference
In-Depth Information
Figure 10.13
Results of a manual resistance test to ensure no cross-talk between the
peroneii (PER) muscle and the tibialis anterior (TA) and lateral gastrocnemius (LG)
muscles. The first trial showed negligible cross-talk between PER and TA; the second
contraction showed negligible cross-talk between PER and LG. See text for further
details. (Reprinted from the
Journal of Electromyography and Kinesiology
,Vol.4,
Winter, D. A., A. J. Fuglevand, and S. Archer. “Cross-talk in Surface Electromyography:
Theoretical and Practical Estimates,” pp. 15 - 26, 1994, with permission of Elsevier.)
Section 2.1). The adjacent channels,
x (t )
and
y(t )
, are isometrically con-
tracted for about 10 s at a moderate contraction level. The general equation
for cross-correlation,
R
xy
(
τ
)
, between signals
x (t )
and
y(t )
is:
T
T
1
x (t )
·
y (t
−
τ
) dt
0
R
xy
(
τ
)
=
R
xx
(
0
)
(10.7)
·
R
yy
(
0
)
where
x (t )
and
y(t )
, respectively, are at a phase shift of 0.
R
xx
(
0
)
and
R
yy
(
0
)
are the mean squares of
x (t )
and
y(t )
, respectively, over the time
T
.
τ
is
normally varied
30 ms, and a typical cross-correlation for two electrode
pairs located 2 cm apart is presented in Figure 10.14. Note that the peak
±
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