Macro electromyography, an update

The macro electromyography method was developed in the 1980s.1 Since then, technical modifications have been made, and a number of conditions have been explored.2, 3 This study is a methodological introduction and an update of findings in some nerve-muscle disorders. The spike component of a motor unit potential (MUP) recorded by a concentric or monopolar needle electromyography (EMG) electrode is generated primarily by fibers within 1-2 mm of the needle recording area. Given that a MUP's typical anatomical reach is 5-15 mm in diameter, it follows that conventional EMG is unable to record activity from the entire motor unit. Such information could promote understanding of muscle in health and disease. Macro EMG, with its large recording area, appears to provide this information by recording the activity from most of the fibers in a given motor unit. The value of combining macro EMG with single-fiber EMG and conventional EMG recordings is discussed.