Discussion on School Bags Using Shoulder Strap Pressure for Reducing Body Load

This study aims to obtain some guidelines for designing school bags that will reduce the body load. We analyzed school bag factors that affect shoulder strap pressure in terms of the shape of strap, its cramp and waist belt. Waist belts are not used usually in school bag design. However we thought that it would be useful for reducing the body load. Seven pupils were used as test subjects. The strap pressure of the shoulder part of the curved strap was lower than that of the straight strap. But the maximum pressure and standard deviation of the curved strap were larger than that of the straight strap. The curved strap was dependent on subject's body size. An important factor was the shape of the curve. The strap pressure of the pivoting cramp was lower than that of the fixed one. Therefore, it was shown that the pivoting cramp reduced the body load. The strap pressure of school bag with waist belt tended to reduce the body load. But the effectiveness of some waist belts were dependent on the subject's height. In particular, the waist belt with the soft and wide pad didn't fit some tall subjects. It was suggested that the change in the height of one's waist due to growth was the most important factor.