Surface electromyography and kinetics during step descent in individuals with low-level chronic or recurrent low back pain and lumbar instability

Background: Most biomechanical studies in populations with low back pain have examined level gait or stationary tasks. This study investigates step negotiation in a subgroup of individuals with low back pain. Methods: Surface electromyography and kinetic data were collected in 22 subjects. Results: Vertical ground reaction force rise-time was slower in participants with low back pain when leading with the left leg and they had delayed muscle onsets of the right gluteus medius, left rectus abdominis with left stepping, right lumbar erector spinae with right stepping but earlier onset with left stepping. EMG activations were higher in the participants with low back pain in the right lumbar erector spinae, right gluteus medius, and left gluteus medius in both left and right steps. Conclusion: The results of this study show that the participants with low back pain have higher muscle activity levels, delayed muscle onsets, and slower weight acceptance.