Selective spatial information from surface EMG after temporal filtering: the application to interference EMG using cross-covariance analysis

Inhomogeneities in muscle activation reveal motor unit recruitment

“…Current methods to study spatial activation patterns with MCSEMG have described the intra-muscular changes that occur at different contraction levels [6,13]. The quite consistent changes in RMS correlation with altering contraction levels, seen in Figs.…”

“…Changes in the EMG amplitude distribution obtained with MCSEMG have revealed spatial inhomogeneous activation of muscles in isometric contractions at different force levels [19,13,6]. In other words, different parts of a muscle are dominantly active as a function of the force level.…”

“…Studies applying MCSEMG to examine spatial intramuscular activation have applied three main techniques to describe this phenomenon: (1) by reporting the change in the root mean square (RMS) distribution over the muscle by topographical visualization, called mapping [19,20], (2) by illustrating mapping of MU action potentials with triggered averaging [12], (3) by calculating and displaying the cross-correlation of each individual channel related to a selected reference channel [6,18].…”

Motor unit synchronization during fatigue: Described with a novel sEMG method based on large motor unit samples

“…However, it has been shown that temporal filtering also partly suppresses cross-talk (Dimitrova et al, 2002;Grassme et al, 2003) and increases spatial selectivity (Dimitrov et al, 2003;Grassme et al, 2003). In particular, the sub-band filtering approach on the monopolar signal (wavelet scale 3 is related to a sub-band center frequency of about 85 Hz) should therefore likely reduce cross-talk and enhance the spatial selectivity as compared to bipolar signals.…”

Effects of EMG processing on biomechanical models of muscle joint systems: Sensitivity of trunk muscle moments, spinal forces, and stability

“…the depth of the signal source (Dimitrova et al, 2002). This is due to the fact that the power of the nonpropagating part of action potentials does not decrease with distance as much as the power of the traveling wave and is reflected in the higher bandwidth of the total EMG power, irrespective of the spatial filter (electrode configuration) used (Dimitrova et al, 2002;Farina et al, 2004a;Grassme et al, 2003). Therefore, by eliminating low-frequency power, HP and whitening might enhance the relative contribution of distant motor units to the recorded signal.…”