BACKGROUND:Task-specific tremor in musicians severely impairs fine motor control. However, little is known about its pathophysiology. Here, we quantify electromyography (EMG) properties in primary bowing tremor-in particular, muscular coactivation-to determine whether primary bowing tremor affects a specific frequency range of coactivation. METHODS:We quantitatively compared EMG properties of the wrist muscles between 4 professional violinists who had task-specific tremor and 4 age-matched healthy controls. RESULTS:We observed bowing tremor-specific muscular coactivation in the frequency range of 3 to 8 Hz only in the patients but not in the healthy controls. No muscular activity was observed at the resonance-frequency range. CONCLUSIONS:Our findings indicate an association between coactivation and bowing tremor at a specific frequency range (3-8 Hz). The absence of EMG activity and coactivation in the mechanical-reflex frequency of the wrist suggests that central mechanisms play a more dominant role than mechanical-reflex mechanisms in primary bowing tremor.