Biomechanical analysis of the lumbar area using surface electromyography: Flexion–relaxation ratio in maintenance workers

Abstract

Objective: This study analysed the presence and absence of electromyographic silence during the holding phase of the flexion-relaxation of the trunk. Methodology: The electrical activity of two back muscles (i.e., longissimus and multifidus) of 10 male workers in the maintenance sector, all younger than 65, was recorded when they performed an unloaded anterior flexion of the trunk for 15 seconds. The risk of suffering from low back pain was evaluated based on the calculated flexion-relaxation ratios. Results: In the sample, the average FRRs of the longissimus and multifidus muscles were 6.47 ± 4.21 and 7.99 ± 4.71, respectively. In addition, 20% of the subjects presented values under 2.98 in the longissimus; and 40%, values under 7.21 in the multifidus—which indicates an absence of silences and possible pain. The average flexion velocity was 103.67 ± 15.56°/s; the average relaxation velocity, 98.968 ± 19.11°/s; and the average flexion angle, 106.94 ± 12.60°. Conclusion: The results of this study demonstrate that, in the long term, maintenance and general service workers may suffer from chronic low back discomfort or pain as a consequence of their daily duties

Keywords

• low back pain
• lumbar region
• occupational health
• surface electromyography
• biomechanical phenomena