| Sumario: | The purpose of this study was to examine the effects of monopolar electrode placement over the innervation zone (IZ) on both the amplitude and frequency contents of the surface electromyographic (EMG) signal. Ten men (mean ± SD age = 23.6 ± 3.0 years) volunteered to perform submaximal to maximal isometric muscle actions of the dominant leg extensors, and two separate monopolar EMG signals were detected from the vastus lateralis. One electrode was placed directly over the IZ, while the second electrode was between the IZ and distal tendon. All EMG signals were analyzed with a wavelet analysis designed specifically for EMG. The results showed that the total EMG intensity (which is analogous to power) in each wavelet band increased with torque, and the EMG signals from the electrode over the IZ had more total intensity in wavelet bands 2-4 (approximately 20-65 Hz) than the corresponding signals from the electrode distal to the IZ. It is possible that these differences in total EMG intensity were due to detection of non-propagating components that, although still present distal to the IZ, were not as strong as they were over the IZ.
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