The primary aim was to explore the relationship between lumbar extensor muscle force control and lifting kinematics in the sagittal and coronal planes among individuals with chronic low back pain. It hypothesised that deficiencies in lumbar extensor muscle force control are associated with altered lower limb kinematics during lifting tasks.
Thirty-three participants with chronic low back pain performed lumbar extension force-matching tasks where they increased and decreased their force output to match a variable target force within 20%–50% of their lumbar extension maximal voluntary isometric contraction using a lumbar dynamometer. The same chronic low-back pain participants were then instructed to lift weight using a self-selected technique in front of laboratory optoelectric motion capture system. Force control was quantified as the root-mean-square-error (RMSE) between participants' force output and target force across the entire, during the increasing (RMSEA), decreasing (RMSED) force portions and for the overall force error (RMSET) of the test. The average range of motion and angular velocity of the trunk, hip and knee in the sagittal and coronal planes were analysed. The relationship between lifting kinematics and RMSE variables was analysed using multiple linear regression.
Deficiencies in lumbar extensor muscle force control were significantly associated with increased knee angular velocity during lifting, both in the sagittal (R² = 0.10, β = 0.35, p = 0.046) and coronal planes (R² = 0.21, β = 0.48, p = 0.004). This suggests a compensatory mechanism involving increased knee movement in response to poor trunk muscle control.
The findings affirm that impaired lumbar extensor muscle force control in people with chronic low back pain is linked to compensatory adjustments in lower limb kinematics during lifting tasks. These adaptations may influence overall posture and lifting efficiency. Future studies should aim to investigate the effectiveness of neuromuscular retraining programs for lumbar extensor muscle force control, the impact of lower limb training on lumbar extensor force control, and the development of dynamic lumbar extensor muscle force assessment to enhance the assessment and management of lifting-related impairments in people with chronic low back pain.
Physiotherapists may introduce specific and novel exercises aimed at enhancing the accuracy of lumbar extensor force control to reduce compensatory movements during lifting.
Rehabilitation exercises that aim to improve knee control and strength may have a positive impact on lumbar extensor force control and may improve lifting movement.
This study may lead to the development of innovative methods for the assessment of lumbar extensor muscle force control assessment that mimic real-life activity challenges, such as during lifting, to evaluate and treat chronic low back pain.
Lifting
Force control
