Objective: A cross-sectional study was conducted to determine and evaluate the effects of schoolbag load on electromyography (EMG) activity of the erector spinae muscle.
Methods: Eighty-four primary schoolchildren were selected from two national medium primary schools in Seri Kembangan, 42 from Primary Two (P2) and 42 from Primary Five (PS), aged 8 and 11 respectively. Data were collected through interviews, anthropometries measurements, the weight of schoolbag load and surface electromyography (SEMG) of the erector spinae using Muscle Tester ME3000f'®. SurfaceAg-AgCl electrodes were used to measure: unloaded standing and walking, and loaded standing and walking.
Results: The study revealed that the erector spinae was found to be more efficient in loaded standing probably due to other trunk muscle co-activity compared to unloaded standing (p<0.05). However, the erector spinae was less efficient when loads were carried on the back while walking, compared to unloaded walking. When the schoolbag was carried over both shoulders, forces generated by the erector spinae were reduced and resulted in a more efficient use of the erector spinae compared to other asymmetrical carrying methods (p<0.05).
Conclusions: Bending slightly forward when carrying schoolbag was found to reduce the forces generated by the erector spinae compared to normal sagittal posture (p<0.05), however no significant difference was found between the different frontal postures. A significant inverse relationship (p<0.01) between the weight of schoolbag load and the average electromyography (AEMG), showed that the signifieance of the erector spinae muscle was reduced when a heavier schoolbag load was carried, owing to other trunk muscles co-activity. The study also revealed that apart from age of schoolchildren, family history of back pain, exposure to environmental tobacco smoke (ETS), weight of the schoolbag and method of carrying schoolbag also play important role as risk factors for back pain.
Keywords: Electromyography, schoolbag, primary school, back pain