The Effect of Backpack Carriage on Selected Biomechanical Variables of Lower Extremity of Girls and Boys With 7-10 Years Age During Walking

Abstract

Background and Aims: Due to the increasing use of backpacks among children and adolescents and conflicting reports about the advantages and disadvantages of using it in causing fatigue, pain, and some musculoskeletal injuries, the present study aimed to determine the effect of backpack carriage on selected biomechanical variables (Spatio-temporal, angular and kinetic kinematics) of the lower extremity of girls and boys with 7-10 years age during walking. Methods: In this Quasi-experimental study, the walking test was taken from 26 students (13 boys and 13 girls) while carrying a backpack at four conditions of zero, 10, 15, and 20% of body weight to analyze selected spatio-temporal, angular kinematic and Kinetic variables. To compare the mentioned variables at the four conditions, the statistical test of analysis of variance with repeated measures test was used following the Bonferroni correction coefficient post hoc test (P<0.008). Results: The results showed a significant difference between zero and 20% conditions in the levels of stride length, stride width and stride rate, percentage of single and double support and sway phases, peak angles of knee flexion and ankle dorsiflexion and plantarflexion, and first and second peaks of normalized vertical force and the depth force of depression (P<0.008). In addition, a significant difference was observed between zero and 15% conditions in the level of normalized stride width and stride rate, peak angle of ankle plantarflexion, and the first and second peaks of normalized vertical force (P<0.008). Also, there was a significant difference in the peak angle of ankle plantarflexion and the first peak of normalized vertical force between 10% to 20% conditions and the second peak of normalized vertical force between zero and 10% conditions (P<0.008). Conclusion: while using backpacks with different weights, awareness of various biomechanical effects can help prescribe the appropriate weight for carrying. Also, due to small biomechanical changes, it seems that the maximum backpack weight in the range of 10% of their body weight is suitable for children. However, necessary precautions should be taken due to individual differences in this regard.