%0 Journal Article
%T Flexion Relaxation Ratio Not Responsive to Acutely Induced Low Back Pain from a Delayed Onset Muscle Soreness Protocol
%A Maggie E. Horn
%A Mark D. Bishop
%J ISRN Pain
%D 2013
%R 10.1155/2013/617698
%X Background. The flexion relaxation ratio (FRR) has been suggested as a measure of muscular performance in patients with low back pain (LBP). The purpose of this study was to investigate whether the FRR was responsive to acute LBP produced from a delayed onset muscle soreness (DOMS) protocol. Methods. Fifty-one pain-free volunteers performed DOMS to induce LBP. Current pain intensity, trunk flexion range of motion (ROM), and passive straight leg raise (SLR) were measured at baseline, 24 and 48 hours after DOMS. Participants were categorized into pain groups based on reported current pain intensity. Changes in FRR, trunk flexion ROM, and SLR ROM were examined using two-way repeated measures analysis of variance. Results. Pain group was not found to have a significant effect on FRR ( = 0.054, ), nor were there any two-way interactions for changes in FRR. The pain group had decreased trunk flexion ROM compared to the minimal pain group ( = 7.21, ), but no decreases in SLR ROM ( = 3.51, ) over time. Interpretation. There were no differences in FRR based on reported pain intensity of LBP from a DOMS protocol. The responsiveness of FRR might be limited in patients with acute onset LBP of muscular origin. 1. Introduction During normal trunk flexion in standing the trunk extensor muscles act eccentrically and are considered myoelectrically ¡°active¡± until a distinct point in the trunk flexion range of motion (ROM) where the lumbar paraspinals relax. Passive structures and pelvic musculature provide the functional limit to terminal flexion ROM. During this time of ¡°relaxation,¡± the paraspinal muscles of the trunk are considered myoelectrically ¡°quiet¡± or electrically reduced. This process may otherwise be described as the flexion relaxation phenomenon or flexion relaxation. The flexion relaxation ratio (FRR) is a measure of muscle performance during the flexion relaxation phenomenon that can be quantified by the ratio of lumbar paraspinal muscle activity in full trunk flexion (relaxation) to the lumbar paraspinal muscle activity either during the flexion phase or extension from full flexion to upright stance using electromyography (EMG) [1]. The flexion relaxation phenomenon is often absent in persons experiencing chronic low back pain (LBP). In this population, lumbar paraspinal muscle activity actually increases during full flexion, particularly in the relaxation period where there is usually myoelectric silence in those experiencing chronic low back pain. Subsequently, changes in the FRR as measured by EMG occur based on this change in muscular activity.
%U http://www.hindawi.com/journals/isrn.pain/2013/617698/