The objective of this research is: To determine alterations in body posture in relation to the weight of the backpack in schoolchildren of the Manuel Ygnacio Monteros Valdivieso Educational Unit. Materials and methods: a quantitative, descriptive and cross-sectional study was conducted from March to August 2016. The sample consisted of 146 students from 6 to 11 years of age. A previously validated survey was executed in a pilot plan for schoolchildren, in addition to a physical examination applying the Adams test and the sagittal arrows test. The following results were obtained: 71.2% carry a backpack with a weight greater than 10% of their body weight; in this same population it was found that 84.62% move around walking and that 65.06% present fatigue; while 70.19% refer pain at shoulder level with a frequency of 3 to 4 times a week with an intensity of 4 in addition; at the physical examination 56.7% presented hyperkyphosis thus contrasting that an excessive weight of the backpack can contribute to the appearance of discomfort and postural alterations.