Automatic decomposition electromyography (ADEMG): validation and normative data in brachial biceps

We describe a new, automatic method (ADEMG) for decomposing EMG interference patterns into their constituent motor unit action potentials (MUAPs), and quantitating the configurational and firing properties of the MUAPs. ADEMG is fast (90 sec analysis time for a 10 sec EMG epoch) and efficient (33-98% of MUAP occurrences correctly identified) because of 4 signal-processing innovations designated digital prefiltering, high-resolution wave form alignment, firing-time analysis and interference-cancellation averaging. Validation experiments are described involving recruitment/derecruitment of low-threshold MUAPs, and single-fiber-triggered averaging. Normative data are presented for 2000 MUAPs from brachial biceps (mean 9.7 MUAPs per site) at 3 levels of isometric contraction (7%, 15% and 30% MVC) and contrasted with normal findings obtained using traditional, low-threshold MUAP analysis. The main advantages of ADEMG are speed of data acquisition and processing in the clinical setting; ability to analyze both low- and high-threshold MUAPs during moderately strong muscular contractions; and MUAP firing-rate information.