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, 54, 210-219

Task-related and Person-Related Variables Influence the Effect of Low Back Pain on Anticipatory Postural Adjustments

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Task-related and Person-Related Variables Influence the Effect of Low Back Pain on Anticipatory Postural Adjustments

Jesse V Jacobs et al. Hum Mov Sci.

Abstract

Background: People with low back pain exhibit altered postural coordination that has been suggested as a target for treatment, but heterogeneous presentation has rendered it difficult to identify appropriate candidates and protocols for such treatments. This study evaluated the associations of task-related and person-related factors with the effect of low back pain on anticipatory postural adjustments.

Methods: Thirteen subjects with and 13 without low back pain performed seated, rapid arm flexion in self-initiated and cued conditions. Mixed-model ANOVA were used to evaluate group and condition effects on APA onset latencies of trunk muscles, arm-raise velocity, and pre-movement cortical potentials. These measures were evaluated for correlation with pain ratings, Fear Avoidance Beliefs Questionnaire scores, and Modified Oswestry Questionnaire scores.

Findings: Delayed postural adjustments of subjects with low back pain were greater in the cued condition than in the self-initiated condition. The group with low back pain exhibited larger-amplitude cortical potentials than the group without pain, but also significantly slower arm-raise velocities. With arm-raise velocity as a covariate, the effect of low back pain remained significant for the latencies of postural adjustments but not for cortical potentials. Latencies of the postural adjustments significantly correlated with Oswestry and Fear Avoidance Beliefs scores.

Interpretation: Delayed postural adjustments with low back pain appear to be influenced by cueing of movement, pain-related disability and fear of activity. These results highlight the importance of subject characteristics, task condition, and task performance when comparing across studies or when developing treatment of people with low back pain.

Keywords: Anticipatory postural adjustment; Cortex; EEG; Low back pain; Posture.

Figures

Fig. 1
Fig. 1
(A) Illustration of the arm-raise task while recording EEG (black circles), EMG (black ovals), and kinematics (gray circles). (B) Representative traces of average EMG waveforms for a subject with LBP (gray lines) and a subject without LBP (black lines), illustrating the APA onset of trunk muscles relative to deltoid onset (time = 0). (C) A subject’s average EEG signal prior to first-muscle onset (contralateral erector spinae onset, time = 0) in the self-initiated condition (solid line) and cued condition (dashed line), illustrating the epoch (gray box) from which the average amplitudes of EEG pre-movement negativity were derived.
Fig. 2
Fig. 2
Group mean (95% confidence intervals) (A) APA onset latencies, (B) amplitudes of pre-movement negativity, and (C) peak arm-raise velocities in the self-initiated (self) and cued conditions. Gray lines and symbols represent the group with LBP; black lines and symbols represent the group without LBP. IO = internal oblique, EO = external oblique, ES = erector spinae, contra = contralateral to the arm raised, and ipsi = ipsilateral to the arm raised.
Fig. 3
Fig. 3
Scatter plots illustrating associations of APA onset latencies at the contralateral EO muscle with Modified Oswestry Disability scores, Numeric Pain Ratings, and FABQ scores. Filled circles represent subjects with LBP in the self-initiated condition; open circles, in the cued condition. The solid trend line represents that of the self-initiated condition; the dashed trend line, the cued condition.

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