Relationships between coping strategies and lumbar muscle activity in subjects with chronic low back pain

Background: Concerning chronic low back pain (CLBP), different cognitive-behavioral models have hypothesized that coping strategies play a role in the chronification of pain by changes in physical activity. Strategies such as avoidance - or persistent coping may be related to changes in (lumbar) muscle activity. Aim: Investigate the different coping strategies present in CLBP and whether these are differentially related to lumbar muscle activity during walking. Methods: In a cross sectional study, 63 subjects with CLBP walked on a treadmill at 3.8 km/h. Coping strategies were measured with the Dutch version of the Coping Strategies Questionnaire and three factors were identified with principal component analysis. Surface electromyography data of the erector spinae were obtained and smooth rectified electromyography (SRE) values were averaged per periods of swing and double support. The ratio of SRE values (swing/double support) was used as a measure of relaxation. The relation between SRE values and coping strategies was analyzed with random coefficient analysis. Results: Three coping strategies (i.e. "catastrophizing", "distraction" and "persistence and control") could be discerned. "Catastrophizing" was positively related to (natural logarithm) SRE values (beta = 0.06, 95% CI = 0.01-0.10; R-2 = 7.7%). "Distraction" was negatively associated with SRE ratios (beta = -0.03, 95% CI = -0.05 to -0.01; R-2 = 7.5%). No relation was found between "persistence and control" and SRE values or ratios. Conclusions: In CLBP, a maladaptive coping strategy like "catastrophizing" is related to increased lumbar muscle activity, and an adaptive strategy like "distraction" to increased lumbar muscle relaxation during walking. (C) 2009 Published by Elsevier Ltd. on behalf of European Federation of International Association for the Study of Pain Chapters.