Psychogenic Motor Unit Activity:

Abstract

Objectives: To investigate motor unit firing patterns responsible for prolonged psychogenic muscle activation. Methods: Integrated surface electromyography [EMG] and single motor unit EMG were recorded from the upper left trapezius muscle of a physically inactive healthy subject solving a reaction time task of 10 min. duration. Results: A stable psychogenic tension representing approximately 0.5% of maximal surface EMG activity was demonstrated, and a single motor unit firing continuously at a median rate of 11 Hz was followed for the full task duration. Conclusions: The observed continuous firing pattern is proposed as a possible injury mechanism in myofascial pain syndrome, if it occurs repeatedly in a small pool of motor units.

KEYWORDS:

• Electromyography
• single motor unit
• recruitment