Article

A biomechanical study of the head-neck complex in seated subjects was conducted
to verify whether a slight load, applied at the back of the head, could
beneficially affect the head-neck posture, one of the factors of postural neck
pain. An eccentric load of 0.5 kg was applied to the subjects' head by means of a
special cap. A group of asymptomatic subjects (n=10, 28.9+/-12.1 yrs), and a
group of subjects that had experienced mild, occasional neck pain (n=10,
39.6+/-18.4 yrs) were compared. They were analyzed while maintaining a still
posture that was periodically perturbed to avoid habituation. A 3D motion
analyzer and reflective markers placed over the head, the neck and the trunk,
were used to compute head inclination and translation and head/neck flexion angle
in different conditions: before, during and after having had the load applied for
15 min. Although the moment induced by the load was extensor, a forward-oriented
movement of the head was observed in both groups. However, the forward
displacement, in relation to the initial position, was smaller in the mild neck
pain group than in the asymptomatic group (5.7+/-4.7 mm vs. 8.9+/-5.5 mm, P<0.05
and 2.6+/-5.9 mm vs. 11.0+/-9.0 mm after 15 min, P<0.05). After removing the
load, the mild neck pain subjects assumed a retracted position (-3.8+/-2.7 mm)
while the asymptomatic subjects stayed protracted (+3.5+/-5.1 mm, P<0.01). These
unexpected findings suggest that a slight load added to the head can influence
the postural control mechanisms and, in symptomatic subjects, lead to a new
strategy aimed at a reduction of the neck extensor muscle contraction.
CI - Copyright (c) 2013 Elsevier B.V. All rights reserved.

Langue : ANGLAIS