Assessment of the cervical range of motion over time, differences between results of the Flock of Birds and the EDI-320: A comparison between an electromagnetic tracking system and an electronic inclinometer

The objective of this study was to analyse cervical range of motion, assessed over time by means of a digital inclinometer (EDI-320) and a three-dimensional electromagnetic tracking device (Flock of Birds).The maximum active cervical range of motion was assessed with two measurement devices in three sessions over time, with 6-week intervals. In total, 26 women and 24 men (mean age: 44.4, SD: 9.9) without known pathology of the cervical spine participated. Four movements were measured axial rotation with the cervical spine in a flexed and in an extended position, flexion–extension, and lateral bending.The results showed that the factor time was significant for rotation in extension and rotation in flexion. The factor device was significant for all movements measured, and the interaction term between time and device was significant for all movements except rotation in extension.The Flock of Birds measured significantly higher ranges of motion on all motions except for lateral bending. A substantial variation in cervical range of motion was observed over time (ranging from −5.6 to 8.1) as well as between devices (ranging from −13.1 to 29.9).Substantial and significant differences in cervical range of motion were found over time as well as differences between the Flock of Birds and the EDI-320.