Effect of Carrying Backpacks With Different Weights on Electromyography Activity of Rectus abdominis and Lumbar Erector Spine Muscles in Eementary Schools students

The purpose of this research was to examine the effect of carrying backpacks with different weights on electromyography activity of rectus abdominis (RA) and lumbar erector spine (ES) muscles in male elementary schools students. Twenty and two Subjects (9.1±1.5 years) were randomly selected, voluntarily. Electromyography activity of these muscles was recorded, bilaterally by an 8-channel EMG recorder System during one minute of direct standing, immediately after 15 minutes of carrying backpacks with 9.5, 11, 12.5 and 14% of body weight on a treadmill at 1.1 m/s. Analysis of data by repeated-measures ANOVA and Tokey tests revealed that carrying backpacks equal to 12.5 and 14% of body weight, induced significant decrease (P<0.003) of ES activity, significant increase (P<0.001) of RA activity and asymmetrical activity (P<0.01) of right and left parts of RA muscle, but carrying backpacks equal to 9.5 and 11 % of body weight not induced significant changes in EMG activity in both of muscles (P>0.05). Also, it is symmetric the ES EMG activity between right and left parts during carrying backpacks with different weights (P>0.05). Thus, according to the results of present study, the loads equal to 9.5 and 11% of body weight recommend for elementary schools students as optimal weight and maximum allowable weight of backpack, respectively.