Spine Kinematics During Prone Extension in People With and Without Low Back Pain and Among Classification-Specific Low Back Pain Subgroups.

Study Design Cross-sectional observational design. Background Spine extension is used in physical therapy during examination and treatment for low back pain (LBP). However, kinematics during prone extension have not been examined using 3-D motion capture. Objectives The primary purpose was to determine differences in spine kinematics during prone extension between subjects with and without LBP. An exploratory analysis was conducted to examine kinematic differences among LBP subgroups. Methods Kinematics of the thoracic and lumbar spine were examined during prone extension, using optical motion capture, in 18 subjects with LBP and 17 subjects without LBP (control group). Excursion of each spinal region was calculated for the entire movement and during 25% increments of extension movement duration. Subjects with LBP were examined and assigned to subgroups using 3 different classification systems for LBP. Repeated-measures analysis-of-variance tests were used to examine effects of group (LBP, control), spine region, and increment of movement duration, and to explore effects of LBP subgroup. Results For spine kinematics, there was a significant group-by-region interaction effect (P<.05). Subjects with LBP displayed less lower lumbar extension (13.3° ± 4.9°) than control subjects (21.4° ± 9.2°). The majority of lower lumbar extension occurred during the first 50% of the motion for subjects with LBP. Subgroup-by-region interaction effects were significant for 2 of 3 LBP classification systems (P<.05). Conclusion Subjects with LBP displayed less lower lumbar extension than control subjects during prone extension. These differences should be considered when evaluating and prescribing prone extension. The interpretation of subgroup differences with prone extension kinematics is limited in the current study by the small sample size, but may need to be considered in future studies of spine kinematics. Level of Evidence Diagnosis, level 4. J Orthop Sports Phys Ther 2016;46(7):571-579. Epub 12 May 2016. doi:10.2519/jospt.2016.6159.