ABSTRACT
Surface electromyography (sEMG) is a non-invasive method with high accuracy to investigate the muscleactivation. The common outcome measurement of this method is sub-maximal voluntary muscle contraction(sub-MVC). sEMG has been shown high reliability in measuring trunk muscle. However, no study reports thereliability of sub-MVC measurement of sEMG in trunk muscles of Thai population. The aim of this study was toinvestigate the reliability of sEMG measurement for lumbar multifidus muscles (LM) and internal oblique muscles(IO) during sub-maximal voluntary muscle contraction. Subjects were 10 healthy Thai participants (5 males, 5females). sEMG of each LM and IO muscle was measured 3 times on both sides. Intraclass correlation coefficients(ICC) and standard error of measurement as a percentage of grand mean (% SEM) were estimated. The resultsshowed that there were very high reliability of left lumbar multifidus muscle (ICC mean 0.99; ICC range 0.98-1.00;% SEM = 1.06), right lumbar multifidus muscle (ICC mean 0.99; ICC range 0.98-1.00; % SEM = 1.07), leftinternal oblique muscle (ICC mean 0.96; ICC range 0.93-0.98; % SEM = 3.42) and right internal oblique muscle(ICC mean 0.99; ICC range 0.98-1.00; % SEM = 2.33). We conclude that surface electromyography is a reliabledevice that can be used to investigate the lumbar multifidus muscles and internal oblique muscles duringsub-maximal voluntary muscle contraction.