Analysis of the weight of school backpack with double strapson the postural control of children

To investigate the influence of the weight of school backpacks on postural control of children. Cross-sectional study in healthy children  aged eight years old. The postural control was evaluated on the force plate (FP) and the Timed Up and Go test (TUG) in three distinct conditions: without backpack (WB), and the backpack adjusted with 5% (.5) and 10% (. 10) of body mass. 90 children were evaluated, and 80% of them used backpacks with two shoulder straps, and 16%  of the children carried over 10% of  their body mass in the backpacks. Regarding the postural control with load on school backpack, there was increase in the sway  area of the center of pressure (A-COP.WB = 6.92 cm²; A-COP.5 = 8.39 cm²; A-COP.10 = 7.96 cm²) and time, in seconds, the performance of the TUG (TUG.WB = 4.75 s; TUG.5 = 4.99 s; TUG.10 = 5.06 s), with statistically significant difference between the loads (p = 0.0001; p = 0.0005), respectively. The anteroposterior (VELAP.SM = 2.41cm s-1; VELAP.5 = 2.30 cm s-1; VELAP.10 = 2.22 cm s-1; p = 0.0001) and mediolateral velocity (VELML.WB = 2.38 cm s-1; VELML.5 = 2.28 cm s-1; VELML.10 = 2.20 cm s-1; p = 0.0001) had a decrease in the median values with statistically significant difference in different conditions. School backpack load  increased the COP area, the time of the TUG and modified the response mechanisms. Therefore, loads up to 5% of body mass imposed on school backpack have negatively influenced the postural control.