Temporal patterns of the trunk muscles remain altered in a low back injured population despite subjective reports of recovery.
Arch Phys Med Rehabil. 2013 Oct 15;
Authors: Moreside JM, Quirk DA, Hubley-Kozey CL
OBJECTIVE: To compare temporal activation patterns from twenty-four abdominal and lumbar muscles between healthy subjects (ASYM) and those who reported recovery from recent low back injury (LBI).
DESIGN: Cross-sectional comparative STUDY SETTING: University Neuromuscular Function Laboratory PARTICIPANTS: 81 healthy adult volunteers: 30 LBI, 51 ASYM INTERVENTIONS: Trunk muscle EMG activity was collected during two difficulty levels of a supine trunk stability test aimed at challenging lumbo-pelvic control.
MAIN OUTCOME MEASURES: Principal component (PC) analysis was applied to determine differences in temporal and/or amplitude EMG patterns between groups. Mixed model ANOVAs were performed on PC scores that explained more than 89% of the variance (?=0.05).
RESULTS: Four PCs explained 89% and 96% of the variance for the abdominal and back muscles, respectively, with both muscle groups having similar shapes in the first 3 PCs. Significant interactions or group main effects were found for all PC scores except PC4 for the back extensors. Overall activation amplitudes for both the abdominal and back muscles (PC1 scores) were significantly (p<0.05) higher for the LBI group, with both abdominal and back muscles of the LBI group demonstrating increased response to the leg loading phase (PC2 scores) compared to the ASYM. Differences were also found between groups in their preparatory activity (PC3 scores) with LBI group having higher early relative amplitude of abdominal and back extensor activity.
CONCLUSIONS: Despite perceived readiness to return to work and low pain scores, muscle activation patterns remained altered in this LBI group, including reduced synergistic co-activation, increased overall amplitudes as well as greater relative amplitude differences during specific phases of the movement. EMG measures provide objective information to help guide therapy and may assist with determining level of healing and return-to-work readiness following a low back injury.
PMID: 24139985 [PubMed – as supplied by publisher]