Electromyographic insertional activity mechanically provoked in the biceps brachii.

Clinically, some electromyographers have felt that electrical activity provoked by needle insertion becomes prolonged prior to the development of positive sharp waves and fibrillation potentials in pathologic conditions. The significance of this is unclear as this electrical activity has not been quantitatively studied in normal subjects. To approach this problem, this study was designed to evaluate insertional activity in normal subjects. A mechanical electrode inserter was designed and assembled. Insertional activity was recorded and analyzed in 20 normal subjects. Sharp spike activity, a component of the total insertional activity, was found to continue for 48 +/- 18 msec following the cessation of electrode movement in the biceps brachii.