Muscle strength in Brazilian firefighters with non-specific chronic low back pain: A cross-sectional study

BACKGROUND: Imbalance between flexor and extensor muscles of the trunk could negatively influence spinal stability. OBJECTIVE: Investigate the strength balance between flexor and extensor muscles of the trunk in military firefighters with non-specific chronic low back pain (NSCLBP). METHODS: One hundred and two male firefighters were assessed in an isokinetic dynamometer at 120 degrees/s and 60 degrees/s to investigate the balance ratio between flexor and extensor (F/E) muscles. RESULTS: An F/E ratio of 0.72 (SD: 0.22; 95%CI: 0.67-0.76; SEM: 0.02) was observed at 60 degrees/s and 0.94 (SD: 0.41; 95%CI: 0.85-1.03; SEM: 0.04) at 120 degrees/s. The mean peak torque of the extensor muscles was 343.1 N.m/Kg (SD: 94.87; 95% CI: 322.8-363.5; SEM: 10.23) at 60 degrees/s and 270.5 N.m/Kg (SD: 113; 95% CI 246.3-294.8; SEM: 12.18) at 120 degrees/s. The mean peak torque of the flexor muscles was 232.4 N.m/Kg (SD: 53.86; 95% CI 220.8-243.9; SEM: 5.81) at 60 degrees/s and 223.8 N.m/Kg (SD: 66.34; 95% CI 209.6-238.1; SEM: 7.15) at 120 degrees/s. All torques generated by the extensor muscles were higher than the flexor muscles (p < 0.05). CONCLUSION: Firefighters with NSCLBP presented a normal F/E balance ratio and higher strength of extensor muscles of the trunk.