Comparison of spinal posture, stiffness and motor control during pushing and pulling tasks in healthcare professional between LBP subgroups classification

Background:
Low back pain (LBP) is the leading cause of musculoskeletal disorder, with high prevalence among healthcare professionals. Although the existing paper has examined the causal relationship between pushing, pulling tasks and LBP, the motor control pattern (either adaptive or mal-adaptive) remains uncertain. This cross-sectional study compared the spinal kinematics, mechanical stiffness and motor control during pushing and pulling tasks between the healthcare professionals classified as LBP groups and asymptomatic groups, which is important to fill the knowledge gap and provide practical ergonomic advice to this population, to prevent the occurrence of LBP.

Purpose:
(1) To examine the biomechanical and neuromuscular pattern of the thoracolumbar spine during pushing and pulling tasks
(2) To examine if differential pattern is displayed between subgroups of LBP categorised by movement impairment classification.

Methods:
Thirty-nine healthcare practitioners who were classified into three subgroups, namely asymptomatic (n=14), LBP with Flexion Pattern (FP, n=11) and LBP with Active Extension Pattern (AEP, n=14) completed the real-time 3D spinal posture scanning (lumbar lordotic and thoracic kyphotic angles, lumbar and cervical linear translations), mechanical stiffness of the thoracolumbar segments (T9-L5), and electromyographic amplitude and synergic pattern of trunk muscles, were measured during quiet standing, pushing and pulling tasks at a target load of 15% of the individual’s body weight.

Results:
All biomechanical measurements showed good to excellent level of reliability (ICC: 0.723-0.981). Pulling task resulted in significantly greater lumbar posterior translation (p=0.009) and Rectus Abdominis (RA) activity (p=0.006), and smaller lumbar lordosis (F=8.448, p<0.001) and thoracic kyphosis (F=4.416, p=0.017), when compared to pushing tasks. There was no significant between-group difference in spinal kinematics and mechanical stiffness, while the AEP group showed a greater Internal Oblique (IO) activity as compared to asymptomatic group in both pushing and pulling tasks (p=0.001).

Conclusion:
Task-specific impacts were identified between the pushing and pulling tasks irrespective of the LBP subgroups of this cohort of healthcare professionals. The advocacy to transfer objects by pushing instead of pulling manoeuvre as the shearing force on lumbar spine was proven to be lower. In this study, individuals with LBP were capable to perform the low level of push/pull manoeuvre with the comparable biomechanical and neuromuscular strategies as those healthy controls, except for greater IO recruitment revealed in the AEP subgroup. Future studies to investigate the are recommended.

Implications:
The findings provide biomechanical evidence that substantiate the advocacy of pushing tasks over pulling task for manual handling. The differential neuromuscular recruitment pattern identified between LBP subgroups provide an essential foundation for prospective research in evaluating the cumulative effect of repetitive push/pull loadings on spinal motor control and spine health for healthcare practitioners.