Subjects with Low Back Pain (LBP) often have altered trunk muscle activity and postural sway during perturbations. Research suggests different perturbations have differing results on abdominal muscle activity and postural sway, however, the majority of perturbations investigated are not realistic daily tasks and little evidence exists if the changes are still present following resolution of symptoms. Aim: to determine trunk muscle activity, Lumbar multifidus (M), iliocostalis lumborum (IL), external oblique (EO), transversus abdominus/internal oblique TrA/IO and postural sway during two reaching tasks between subjects with history of LBP (HLBP) and those without. 20 volunteers, 8 HLBP (22±2yrs, 174.9±6.0cm, 68.3±6.22kgs,) and 12 without HLBP (20.58±2.23 yrs, 174.5±9.8cm, 68.6±13.9kgs) gave informed consent. Surface Electromyography (sEMG) measured muscle activity of M, IL, TrA/IO, EO and VICON force plate measured postural sway (anterior posterior (AP)centre of pressure (CoP), medial lateral(ML)CoP during high (HRT) and low reaching tasks (LRT). sEMG data was normalized to maximum voluntary contractions. Force plate data was processed using Matlab R2009b. Results: Mann-Whitney U tests noted a significant increase in EO sEMG activity in HLBP group for HRT (p=0.03). Results were insignificant for HRT: M(p=0.64), IL(0.19), TrA/IO,(p=0.14), AP CoP(p=0.44), ML CoP(p=0.69), LRT: M(p=0.58), IL(0.35) TrA/IO(p=0.58), EO(p=0.28), AP CoP (p=0.39), ML CoP (p=0.24).Background
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