Comparing Trunk Neuromuscular Measures to a Clinical Battery of Tests in a Recovered Low Back Injured Population.

Abstract

Introduction: The purpose of this study was to determine differences in trunk muscle activation patterns in recovered LBI groups classified as unstable or not. EMG from comprehensive sets of trunk muscles were compared during a controlled task between groups separated using a Modified Hicks’s protocol. Methods: 32 LBI participants who were deemed recovered were recruited from CFB Halifax within 12 weeks post-injury. EMG from trunk muscles was recorded during a standardized lift-and-replace task. Results: Significant group*muscle interaction effects were found for amplitude and temporal EMG patterns. Post hoc findings showed fewer between-muscle differences in the unstable group. Conclusions: The unstable group utilized strategies for increased active stiffness through synergistic co-activation and altered temporal responses and indicates a “bracing” strategy. These findings are consistent with the hypothesis that passive stiffness decreases are compensated by the neuromuscular system. Furthermore they provide initial evidence linking clinical tests for instability to objective physiologically-based measures.