Variation in the Cervical Range of Motion Over Time Measured by the “Flock of Birds ” Electromagnetic Tracking System

Objective. To establish the normal variation over time for active and passive cervical range of motion (ROM) measured with the Flock of Birds electromagnetic track-ing system (FOB). Summary of Background Data. Data about normal variation of cervical ROM over time are scarce but impor-tant for the interpretation of study results. Methods. Forty-eight subjects without a manifest dys-function in neck and shoulder region (asymptomatic group) and 58 subjects with a dysfunction in the neck and shoulder region (symptomatic group) participated in this study. Cer-vical active and passive ROMwas assessed in three different sessions 6 weeks apart. The following movements were measured: flexion-extension, lateral bending, and axial ro-tation in neutral, flexed, and extended position