Background: The surface electromyography (sEMG), by evaluating the paraspinal muscle activity, may be used for diagnosis and evaluation of rehabilitation effectiveness patients with low back pain.
Objective: The purpose of the study was to determine the intra- and inter-session reliability of the measurement of the activity of the lumbar erector spinae (LES) activity (extension-flexion ratio).
Methods: The study included 21 asymptomatic subjects, aged 14 to 27 years, mean 23.7 ± 2.9. The LES muscle activity was assessed with using of the sEMG during forward trunk flexion and extension by two examiners. Based on the quotient of the LES muscle activity obtained during four concentric and eccentric tasks the extension-flexion ratio was calculated.
Results: The measurements displayed excellent or fair-to-good reliability (intraclass correlation coefficient ranged from 0.90 to 0.68). The typical error and coefficient of variations, ranged from 0.34 to 0.58, and from 13.7 to 21.9, respectively.
Conclusions: The measurement of the extension-flexion ratio performed with the use of sEMG shows high level of intra- and inter-session reliability, suggesting that this parameter is a reliable tool in evaluation of the lumbar paraspinal muscles activity. However, the level of typical error should be taken into account.
Keywords: Reliability; extension-flexion ratio; surface electromyography; typical error.