A Kinematic Analysis of Automatic Postural Responses during Predicted and Unpredicted Postural Perturbations in People with Low Back Pain.

Abstract

Objectives: Limited evidence exists on alterations in postural response kinematics following external perturbations in individuals with chronic low back pain (LBP). Therefore, this study aimed to investigate differences in automatic postural responses between individuals with chronic LBP and asymptomatic controls during forward translation of the support surface.

Methods: A total of 21 participants with chronic non-specific low back pain (LBP) and 21 age- and sex-matched healthy adults participated in this study. Participants were exposed to both predicted and unpredicted perturbations through forward translation of the support surface, which were analyzed using a motion analysis system. Angular displacements of the trunk and lower limbs were measured across four predefined time intervals corresponding to anticipatory postural adjustments (APA) and compensatory postural adjustments (CPA).

Results: In the unpredicted condition, trunk angular displacement during the APA1 phase was significantly lower in the LBP group compared with the control group (P = 0.04). A significant main effect of group was observed for hip (P = 0.009, ηp² = 0.17), knee (P = 0.01, ηp² = 0.16), and ankle (P = 0.01, ηp² = 0.14) displacements during the CPA1 phase. Moreover, a significant group effect was found for knee (P = 0.01, ηp² = 0.20) and ankle (P = 0.04, ηp² = 0.09) displacements during the CPA2 phase. Participants with LBP exhibited greater lower-limb joint displacements than controls under predicted and unpredicted conditions.

Conclusion: Individuals with chronic low back pain (LBP) demonstrated altered kinematic strategies of the trunk and lower-limb joints in response to forward translation of the support surface. These findings suggest clinicians should consider evaluating and addressing automatic postural responses in this population.