The effect of head movement restriction on the kinematics of the spine during lifting and lowering tasks.

This study aimed to examine the effects of head movement restriction on relative angles and their derivatives using the stepwise segmentation approach during lifting and lowering tasks. Ten healthy men lifted and lowered a box using two styles (stoop and squat), with two loads (i.e. 10% and 20% of body weight); they performed these tasks with two instructed head postures [(1) Flexing the neck to keep contact between chin and chest over the task cycle; (2) No instruction, free head posture]. The neck flexion significantly affected the flexion angle of all segments of the spine and specifically the lumbar part. Additionally, this posture significantly affected the derivatives of the relative angles and manifested latency in spine segments movement, that is, cephalad-to-caudad or caudad-to-cephalad patterns. Conclusively, neck flexion as an awkward posture could increase the risk of low back pain during lifting and lowering tasks in occupational environments. Little information is available about the effects of neck flexion on other spine segments' kinematics and movement patterns, specifically about the lumbar spine. The result of this experimental study shows that neck flexion can increase the risk of low back pain by increasing lumbar flexion angle and spine awkward posture.