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STUDY DESIGN: Clinical test validation. Objectives: Preliminary study of concurrent and discriminant validity of a clinical test of thoracolumbar dissociation. BACKGROUND: Control deficits of back muscles and trunk movement are common in chronic/recurrent low back pain (LBP). A reliable clinical test to rate an individual's ability to dissociate lumbopelvic movement from the thoracolumbar region has been described. This test rates the performance quality of 5 key aspects against criterion standards. METHODS: Concurrent validity was examined by comparison of clinical test scores (overall score and each individual criterion) against spine kinematics. Discriminant validity was evaluated by comparison of scores between pain-free controls and participants with LBP. A receiver operating characteristic curve was calculated to determine the optimal cutoff or score to differentiate between good and poor performers. RESULTS: Concurrent validity was supported by the significant correlation between the total score and motion of the T5 vertebra relative to the S1 vertebra (P<.05). Scores for some (4 correlations of 14 measures) but not all individual criteria were correlated with the kinematic features that each criterion was expected to reflect. Discriminant validity was supported by higher test scores for pain-free controls than for participants with LBP after 2 minutes of training (P = .045). Scores of less than 5.5 were more prevalent in the LBP group (pretraining LBP versus control, 72% versus 35%; P = .008; posttraining LBP versus control, 48% versus 16%; P = .018). CONCLUSION: This preliminary study of concurrent and discriminant validity of the test provides a foundation to further investigate its utility to characterize thoracolumbar movement patterns in individuals with LBP. [ABSTRACT FROM AUTHOR]

Study Design: Cross-sectional design., Objective: To investigate whether recurrent low back pain (LBP) is associated with changes in motor cortical representation of different paraspinal muscle fascicles., Summary of Background Data: Fascicles of the lumbar paraspinal muscles are differentially activated during function. Human studies indicate this may be associated with a spatially separate array of neuronal networks at the motor cortex. Loss of discrete control of paraspinal muscle fascicles in LBP may be because of changes in cortical organization., Methods: Data were collected from 9 individuals with recurrent unilateral LBP and compared with 11 healthy participants from an earlier study. Fine-wire electrodes selectively recorded myoelectric activity from short/deep fascicles of deep multifidus (DM) and long/superficial fascicles of longissimus erector spinae (LES), bilaterally. Motor cortical organization was investigated using transcranial magnetic stimulation at different scalp sites to evoke responses in paraspinal muscles. Location of cortical representation (center of gravity; CoG) and motor excitability (map volume) were compared between healthy and LBP groups., Results: Individuals with LBP had a more posterior location of LES center of gravity, which overlapped with that for DM on both hemispheres. In healthy individuals, LES center of gravity was located separately at a more anterior location to that for DM. Map volume was reduced in LBP compared to healthy individual across muscles., Conclusion: The findings highlight that LBP is associated with a loss of discrete cortical organization of inputs to back muscles. Increased overlap in motor cortical representation of DM and LES may underpin loss of differential activation in this group. The results further unravel the neurophysiological mechanisms of motor changes in recurrent LBP and suggest motor rehabilitation that includes training of differential activation of the paraspinal muscles may be required to restore optimal control in LBP.