Individuals with Non-Specific Low Back Pain in an Active Episode Demonstrate Temporally Altered Torque Responses and Direction-Specific Enhanced Muscle Activity Following Unexpected Balance Perturbations

Authors

Stephanie L. Jones, University of Vermont
Juvena R. Hitt, University of Vermont
Michael J. DeSarno, University of Vermont
Sharon M. Henry, University of Vermont

Document Type

Article

Publication Date

9-1-2012

Publication Title

Experimental Brain Research

Abstract

Individuals with a history of non-specific low back pain (LBP) while in a quiescent pain period demonstrate altered automatic postural responses (APRs) characterized by reduced trunk torque contributions and increased co-activation of trunk musculature. However, it is unknown whether these changes preceded or resulted from pain. To further delineate the relationship between cyclic pain recurrence and APRs, we quantified postural responses following multi-directional support surface translations, in individuals with non-specific LBP, following an active pain episode. Sixteen subjects with and 16 without LBP stood on two force plates that were translated unexpectedly in 12 directions. Net joint torques of the ankles, knees (sagittal only), hips, and trunk, in the frontal and sagittal planes, were quantified and the activation of 12 muscles of the lower limb unilaterally and the dorsal and ventral trunk, bilaterally, were recorded using surface electromyography (EMG). Peaks and latencies to peak joint torques, rates of torque development (slopes), and integrated EMGs characterizing baseline and active muscle contributions were analyzed for group by perturbation direction (torques) and group by perturbation by epoch interaction (EMG) effects. In general, the LBP cohort demonstrated APRs that were of similar torque magnitude and rate but peaked earlier compared to individuals without LBP. Individuals with LBP also demonstrated increased muscle activity following perturbation directions in which the muscle was acting as a prime mover and reduced muscle activity in opposing directions, proximally and distally, with some proximal asymmetries. These altered postural responses may reflect increased muscle spindle sensitivity. Given that these motor alterations are demonstrated proximally and distally, they likely reflect the influence of central nervous system processing in this cohort.

Keywords

Ankle strategy, Automatic postural response, Hip strategy, Joint torque, Postural control, Surface electromyography

Volume

221

Issue

4

First Page

413

Last Page

426

DOI

10.1007/s00221-012-3183-8

ISSN

00144819

Rights

© Springer-Verlag 2012.

Comments

Peer reviewed accepted manuscript.

Recommended Citation

Jones, Stephanie L.; Hitt, Juvena R.; DeSarno, Michael J.; and Henry, Sharon M., "Individuals with Non-Specific Low Back Pain in an Active Episode Demonstrate Temporally Altered Torque Responses and Direction-Specific Enhanced Muscle Activity Following Unexpected Balance Perturbations" (2012). Exercise and Sport Studies: Faculty Publications, Smith College, Northampton, MA.
https://scholarworks.smith.edu/ess_facpubs/5