Summary
Objectives:
Surface EMG crosstalk is the EMG signal detected over a non-active muscle and generated
by a nearby muscle. The aim of this study was to analyze the sources of crosstalk
signals in surface EMG recordings and to discuss methods proposed in the literature
for crosstalk quantification and reduction.
Methods:
The study is based on both simulated and experimental signals. The simulated signals
are generated by a structure based surface EMG signal model. Signals were recorded
with both intramuscular and surface electrodes and single motor unit surface potentials
were extracted with the spike triggered averaging approach. Moreover, surface EMG
signals were recorded from electrically stimulated muscles.
Results:
From the simulation and experimental analysis it was clear that the main determinants
of crosstalk are non-propagating signal components, generated by the extinction of
the intracellular action potentials at the tendons. Thus, crosstalk signals have a
different shape with respect to the signals detected over the active muscle and contain
high frequency components.
Conclusions:
Since crosstalk has signal components different from those dominant in case of detection
from near sources, commonly used methods to quantify and reduce crosstalk, such as
the cross-correlation coefficient and high-pass temporal filtering, are not reliable.
Selectivity of detection systems must be discussed separately as selectivity with
respect to propagating and non-propagating signal components. The knowledge about
the origin of crosstalk signal constitutes the basis for crosstalk interpretation,
quantification, and reduction.
Keywords
Surface EMG - electrically elicited contractions - spike triggered averaging - volume
conduction
