Article

Previous studies have shown that individuals with WAD display decreased postural
stability during standing and walking tasks. However, their ability to maintain
seated upright posture has never been investigated. The objective of this study
was to characterize kinematic and electromyographic postural stabilization
patterns in individuals with chronic WAD and to compare these patterns with those
in an able-bodied control group. Ten individuals with WAD and an age- and
gender-matched group of healthy individuals were exposed to sudden forward and
backward support surface translations while they were seated. Neck and trunk
muscle activity and angular displacements as well as centers of mass (COMs)
linear displacements at four levels of the head and trunk were computed. The
displacement onset of the combined head, arms and trunk COM was significantly
delayed in persons with WAD. However, their peak trunk angles were smaller and
were reached sooner. In the WAD group, the activation onset of the lumbar erector
spinae was less affected by perturbation direction and the sternocleidomastoid
muscle, a neck flexor, showed a trend towards being activated later, compared to
the healthy group. These results suggest that individuals with WAD may alter
stretch reflex threshold and/or elicit a learned response for pain avoidance that
may be direction-specific. Such findings highlight the importance of assessing
both spatial and temporal characteristics across different levels of the spinal
musculoskeletal system to evaluate multidirectional postural responses in WAD
individuals.

Langue : ANGLAIS