Da. Winter et al., CROSSTALK IN SURFACE ELECTROMYOGRAPHY - THEORETICAL AND PRACTICAL ESTIMATES, Journal of electromyography and kinesiology, 4(1), 1994, pp. 15-26
The purpose of this paper is to address four aspects of surface electr
omyography associated with crosstalk between adjacent recording sites.
The first issue that is addressed is the potential crosstalk between
electrodes located on muscles with different functions: antagonist pai
rs, or muscles with one common and one different function (i.e. soleus
/peroneus longus or soleus/gastrocnemius). Practical functional tests
are utilized to demonstrate the crosstalk between muscle pairs to be n
egligible. The second goal is to estimate the depth of pick-up and the
crosstalk between myoelectric signals from agonist muscles using a th
eoretical model. The depth of pick-up was estimated to be 1.8 cm (incl
uding a 2 mm layer of skin and fat) using electrodes of 49 mm2 with bi
polar spacing of 2.0 cm. A cross-correlation technique is demonstrated
which predicts the common signal (crosstalk) between surface electrod
es with electrode-pair spacing of 1 cm around a hypothetical muscle. T
he predicted crosstalk using cross-correlation measures was 49% at 1 c
m electrode-pair spacing dropping to 13% at 2 cm spacing and 4% at 3 c
m. The third part compares these predictions with crosstalk measures f
rom experimental recordings taken from electrode pairs spaced 2.5 cm a
part around the quadriceps. At 2.5 cm spacing there was 22-24% common
signal dropping to between 4-7% at 5 cm and to between 1 and 2% at 7.5
cm. The fourth and last component of this report assesses three metho
ds to decrease the range of pick-up and thereby potential crosstalk: e
lectrodes of smaller surface area, reduced bipolar spacing and mathema
tical differentiation. All three techniques reduce the common signal b
y varying amounts; all three techniques combined reduce the predicted
crosstalk for the 1.0 cm electrode-pair spacing from 49-10.5%.