Modifica di Electromyography (sezione)

===Processing of sEMG Signals===
For a long time, the most common form of processing the sEMG signal was to integrate the rectified waveform. This is done by rectifying the signal, i.e., making the negative deflections of the trace positive using appropriate electronic circuits. The resulting signal is then integrated, meaning it is passed through a low-pass filter that outputs a much smoother signal, averaging all the peaks of the original rectified signal instant by instant.

This type of processing was particularly popular because it was easy to implement with simple electronic circuits long before the advent of computers and digital signal processing.

Today, more appropriately, especially thanks to the use of digital signal processing, the root mean square (RMS) value of the signal is used.<ref>E M Spinelli 1, N H Martinez, M A Mayosky. [https://pubmed.ncbi.nlm.nih.gov/11410389/ A single supply biopotential amplifier.] Med Eng Phys. 2001 Apr;23(3):235-8. doi: 10.1016/s1350-4533(01)00040-6.<br /></ref> In this case, each signal value is squared and then averaged over time. In this way, the negative values of the signal become positive since squaring a negative value gives a positive result. Another type of processing is the one that provides the mean rectified value. This, along with integrated rectification, is an approximate measure of the area under the sEMG signal, but neither has a precise physical, physiological, or clinical meaning. The RMS value, on the other hand, is a measure of signal power and therefore has a more relevant clinical meaning. For this reason, it is increasingly used today.

In addition to these amplitude-related measurements, it is essential to remember the time measurements related to the onset of various sEMG signals. These times can be correlated with an external mechanical or electrical stimulus, as in the study of reflexes, or with movements or forces applied or exerted by one or more skeletal segments. These measurements are of interest in biomechanical studies.


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