MOTOR UNIT NUMBER ESTIMATES BASED ON THE AUTOMATED-ANALYSIS OF F-RESPONSES

An automated technique for estimating the number of motor units based on single motor unit action potentials in the F-response is described. The average surface detected motor unit action potential (S-MUAP) was calculated from the datapoint-by-datapoint average of a sample of S-M UAPs automatically selected from a population of F-responses. The tech nique was applied to the thenar muscles of young (n = 18, aged 31 +/- 11 years) and older (n = 15, aged 68 +/- 3) subjects. Motor unit numbe r estimates based on the automated selection of S-MUAPs from the F-res ponses compared well with those derived using a computer-assisted manu al method for selecting S-MUAPs from the F-response (automated 245 +/- 105 vs. manual 241 +/- 100, r = 0.93) and were similar to estimates o btained using multiple point stimulation (219 +/- 77). The advantages of the automated technique for collecting S-MUAPs from the F-response include the ready tolerance of the technique by subjects, the minimal amount of operator interaction required, and the additional informatio n relating to the conduction velocities and latencies of single motor axons. (C) 1994 John Wiley & Sons, Inc.