Effects of schoolbag-carrying methods and load on body strains and postures among young male students

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This study investigated the influences of carrying mode combining with carrying weight on participants’ left and right trapezius (LTZ and RTZ) and erector spinae (LES and RES) muscle activations and the body posture alterations (i.e., head angle (HA), trunk angle (TA), lateral shoulder tilt (LST), and lumbosacral angle (LSA)). All data were collected after participants walking for 10 min on a treadmill. Twenty male university students were recruited as participants in this study and carried in nine test combinations of 3 carrying methods (two-strap backpack, one-strap backpack, and crossbody bag) and 3 loads (5%, 10%, and 15% of their respective body weights, BWs). Results show that carrying load and methods significantly affected body postures (i.e., TA, LST, and LSA), whereas HA was only affected by carrying load. Additionally, carrying method had a significant effect only on RTZ activation and it was more noticeable when asymmetrically carrying backpack with 1-strap. Carrying with 1-strap backpack should be avoided because of relatively high LST, TA, HA and RTZ activation, this unbalance load may cause uneven shoulders posture therefore can be served as a warning of possible spinal scoliosis. The findings from this study can be references for the daily backpack carrying use.