MOTOR UNIT SIZE ESTIMATION - CONFRONTATION OF SURFACE EMG WITH MACRO EMG

Surface EMG (SEMG) is little used for diagnostic purposes in clinical neurophysiology, mainly because it provides little direct information on individual motor units (MUs). One of the techniques to estimate the MU size is intra-muscular Macro EMG. The present study compares SEMG with Macro EMG. Fifty-eight channel SEMG was recorded simultaneously w ith Macro EMG. Individual MUPs were obtained by single fiber triggered averaging. All recordings were made from the biceps brachii of health y subjects during voluntary contraction at low force. High positive co rrelations were found between all Macro and Surface motor unit potenti al (MUP) parameters: area, peak-to-peak amplitude, negative peak ampli tude and positive peak amplitude. The MUPs recorded with SEMG were dep endent on the distance between the MU and the skin surface. Normalizin g the SEMG parameters for MU location did not improve the correlation coefficient between the parameters of both techniques. The two measure ment techniques had almost the same relative range in MUP parameters i n any individual subject compared to the others, especially after norm alizing the surface MUP parameters for MU location. MUPs recorded with this type of SEMG provide useful information about the MU size. (C) 1 997 Elsevier Science Ireland Ltd.