Low back pain reduces reliance on the segment rotation mechanism for postural control in challenging postural...

Low back pain (LBP) is considered to alter postural control, yet postural control results remain heterogenous in the LBP population. A potential explanation is that postural control has been predominantly characterised by the 'center of pressure' (CoP) mechanism in non-challenging anatomical conditions, omitting the contribution of the 'segment rotation' mechanism (i.e. modification of whole-body angular momentum). The objective of this study was to characterise the impact of LBP on postural control in non-challenging and challenging bipedal upright postures, using indicators illustrating the contribution of both the CoP and segment rotation mechanisms to postural control.

Twenty adults with chronic LBP and twenty age-matched adults without LBP stood quietly on a forceplate in four postural conditions: anatomical with eyes open, anatomical with eyes closed, tandem with eyes open and tandem with eyes closed. ANOVAs were used to compare indicators illustrating the contribution of the CoP and segment rotation mechanisms between groups and conditions.

No difference in indicators of the CoP mechanism were observed between the two groups. Smaller results in mediolateral indicators accounting for the segment rotation mechanism were observed for the LBP group in the tandem with eyes closed condition, compared to the control group.

These findings suggest that LBP impairs reliance on the segment rotation mechanism (i.e. modification of whole-body angular momentum) for postural control, when its contribution is substantial and cannot be compensated by visual feedbacks. Consequently, the segment rotation mechanism should be quantified complementarily to the CoP mechanism in the LBP population.