Mean, median and mode estimation of motor unit action potential templates

Accurate estimation of motor unit action potential (MUAP) templates in the presence of background EMG activity and instrumentation noise is an important requirement of quantitative clinical EMG analysis; especially if EMG signal decomposition is utilized. Traditional mean estimation was compared with recently utilized median estimation and a new mode estimation technique. Using the isolated MUAPs within 250 trains of concentric-needle-detected MUAPs (25-740 per train), obtained using EMG signal decomposition, template baseline rms levels and their spike shape fidelities were measured. Median estimation had statistically better (p<0.05) average rms values than mode estimation, 3.1±2.6 versus 3.5±2.4 μV, respectively. Both had significantly (p<0.001) lower average rms values than mean estimation (4.6±3.4 μV). Mode estimation provided statistically better (p<0.001) spike fidelity measures than median estimation, 99.59±0.79% versus 98.68±2.17% respectively. Mode estimation results were also least variable and therefore might be clinically most useful