The aim of the paper was to determine a correlation between the weight of a child's backpack, their body weight, and certain features of their body posture.
Material and methods: The study group consisted of 109 children, all aged seven years. The parameters of body posture were determined using the Zebris Ultrasonic System.
Results: The number of children carrying a school backpack in accordance with recommendations was 44 subjects (40.37%). Statistically significant changes were found in the total length of the spine (Z = 2.223, p = 0.026) and between backpack weight and changes in the following parameters: the total length of the spine (rs = -0.3999, p = 0.017), the length and the angle of the lumbar lordosis (rs = -0.3352, p = 0.049), the angle of the lumbar lordosis (rs = -0.5065, p = 0.002), and the sacral angle (rs = -0.4279, p = 0.010).
Conclusions: Wearing a backpack heavier than 10% of one's body weight can cause shallowing of the lumbar lordosis and a tendency towards a vertical position of the sacrum. Monitoring the weight of children's school backpacks and enabling them to leave books and notebooks at school would probably be beneficial in reducing the daily burden put on children's spines.