Head posture and loading of the cervical spine.

Calculations by Colombini et al. (Ergonomics of Working Postures. Taylor & Francis, London, 1985) showed that a line of gaze below the horizontal would load the cervical spine more than a horizontal gaze. Precision stadiometer tests were run, using seven subjects, to measure the effects on spinal length of different angles of gaze. After 1 h exposure whilst sitting in a controlled posture, there were significant differences in the shrinkage of the spine between the horizontal gaze and the 20 and 40 angles below the horizontal. The increased spinal loading demonstrated by the increase in spinal shrinkage calls into question the recommendations for angle of gaze recommended in textbooks.