The examination of EMG Changes of Students' Trunk Muscles When Carrying Traditional Schoolbags



The purpose of this study was to examine EMG changes in rectus abdominis (RA) and erector spinae (ES) muscles when carrying backpacks, shoulder bags and hand bags (a load equal to 10% of body weight) in male elementary school students. Twenty subjects with mean age of 9.5 years were voluntarily selected. The EMG activity of these muscles was recorded bilaterally by an EMG recorder system during 1 minute of direct standing, immediately after 15 minutes of carrying each bag on a treadmill at 1.1 m/s speed. The analysis of data by ANOVA with repeated measures indicated that shoulder bag carrying induced asymmetrical activity of right and left parts in both RA and ES muscles. The hand bag carrying induced an increase in this asymmetry so that the EMG level in both muscles increased significantly at contra lateral part of the bag and decreased significantly at the ipsilateral part of the bag. While carrying backpacks, the EMG activity level of ES had a slight significant decrease but RA muscle observed a slight significant increase. The EMG activity of right and left parts in both ES and RA muscles was symmetric when carrying backpacks. According to the results of this study, backpacks can be suggested as the best mode of schoolbags, because it minimizes the asymmetry of muscle activity and the physical stress due to carrying schoolbags.