Duration of the project:
1. 1. 2024 – 31. 12. 2025
Lead partner:
University of Primorska, Faculty of Health Sciences
Project partner:
Principal investigator at UP Faculty of Health Sciences:
Assist. Prof. Žiga Kozinc (SICRIS, ResearchGate)
Team at UP Faculty of Health Sciences:
- Assoc. Prof. Matej Plevnik, PhD (SICRIS, ResearchGate)
- Prof. Nejc Šarabon, PhD (SICRIS, ResearchGate)
- Assoc. Prof. Dorjana Zerbo Šporin, PhD (SICRIS, ResearchGate)
- Assist. Prof. Urška Čeklić, PhD (SICRIS, ResearchGate)
Project results:
The project was carried out within a bilateral research collaboration between the University of Primorska, Faculty of Health Sciences (Slovenia), and the University of Banja Luka, Faculty of Physical Education and Sport (Bosnia and Herzegovina), from January 2024 to December 2025. On the Slovenian side, the project was coordinated by assist. prof. dr. Žiga Kozinc and assoc. prof. dr. Matej Plevnik.
The aim of the project was to investigate how carrying school bags of different weights affects gait kinematic parameters in primary school children aged 8 to 12 years. A total of 224 children participated – 128 from Slovenia (Anton Ukmar Primary School, Koper) and 96 from Bosnia and Herzegovina (Banja Luka). Each child underwent measurements of basic anthropometric characteristics (body height, body mass, body mass index), grip strength using a hand dynamometer, and spatiotemporal gait parameters using the OptoGait system. Gait was assessed under three conditions: without load, with a backpack weighing 20% of the child’s body mass carried on both shoulders, and with the same load carried on one shoulder.
The results showed that body height, body mass, and age were the most important factors influencing gait patterns. Taller and heavier children walked with longer step lengths and longer ground contact times. Age proved to be the most consistent factor – older children demonstrated longer step lengths, a greater proportion of the stance phase, and a smaller proportion of the swing phase, reflecting the gradual maturation of gait. The additional load of the school backpack primarily resulted in prolonged ground contact time, while the fundamental gait pattern remained largely unchanged. Sex, hand dominance, and upper limb muscle strength did not have a significant effect on gait parameters. The comparison between the two countries showed that the groups were comparable in terms of physical characteristics and muscle strength, with differences emerging mainly in the temporal organisation of the gait cycle – Slovenian children showed a greater proportion of the stance phase, while children from Bosnia and Herzegovina showed a greater proportion of the swing phase.
The findings of the project contribute to a better understanding of how school bag carriage affects children’s motor development and provide a professional basis for developing recommendations on the optimal weight of school backpacks.
Abstract
It is common for children to transport their school books and other school equipment using specialized school bags, backpacks, or school trolleys. Most (90%) wear a traditional school bag on the back. In research of this type, the influence of different masses of school bags on the spatiotemporal parameters of walking was mainly examined. The influence of carrying school bags of different weights (10-15% of the subject’s body mass) was often examined. In comparison, postural changes in static and dynamic conditions were recorded when carrying an external load greater than 20% of the child’s body mass).
Despite the lack of information on the impact of a school bag on lower back pain in children and adolescents, the authors believe that carrying too heavy school bags is an essential biomechanical factor that negatively affects children’s growth and development.
The research examines the influence of different external loads caused by carrying a school bag of different masses on the kinematic parameters of walking in children aged 8 to 12.
The sample of respondents consists of 200 boys and girls aged 8 to 12 who attend schools in the Republic of Srpska (Bosnia and Herzegovina) and the Republic of Slovenia. One of the conditions for participating in this research is that the children have signed written consent from their parents or legal representative. Children with intellectual disabilities, epilepsy, cerebral palsy, hemiparesis, diabetes mellitus, diseases of the heart and blood flow, respiratory organs, children with a history of fractures of the lower extremities in the past year, children who use mobility aids, who feel any pain, fatigue during the day testing, they will not be able to participate in the research.
Sample variables
The independent variables are:
1. Anthropometric characteristics of the subjects: body mass, body height, and percentage of fat tissue.
2. The body mass index will be used to assess the nutritional status of the examined group concerning the percentile curve for boys and girls aged 5 to 19.
3. External load:
• no load (no school bag)
• a school bag weighing 10% of the subject’s body weight
• a school bag weighing 20% of the subject’s body weight
• a school bag weighing 30% of the subject’s body weight
The dependent variables are:
Kinematic gait parameter:
• cycle length
• step length and step frequency
• duration of the stance phase
• duration of the swing phase
• duration of the contact phase with one leg (single support)
• duration of the contact phase with both legs (double support)
Research flow and procedures
With the approval of the Ministry of Education of the Government of the Republic of Srpska and the Ministry of Education, Science and Sports of the Republic of Slovenia, as well as with the approval of the management of school institutions, respondents and their parents will be informed about the subject and purpose of the research through a questionnaire. By filling out the questionnaire and signing it, the parents or legal representative of the child would consent for the child to participate in this research.
It is planned that the testing will be carried out in the physical education halls of the schools that took part in the research. In the morning hours, anthropometric measurements would be taken. A Seca (Germany) altimeter would be used to assess body height. In contrast, a specialized Tanita BC 418a scale would be used to assess other anthropometric characteristics (body mass, percentage of fat tissue, body mass index), which uses the bioelectrical impedance method to assess the subject’s body composition.
The kinematic parameter of the gait will be determined using the OptoGait system (Italy), where each of the subjects, after being thoroughly familiarized with the test tasks, first without load and then carrying a precisely determined external load on the back (a school bag weighing 10%, 20% and 30 % of the subject’s body mass), at an arbitrary speed of movement, crosses the appropriate distance (5m), within which the spatiotemporal parameters of the gait are monitored. Each subject has the opportunity to repeat the test three times, and the mean value of the obtained parameters will be taken for further analysis.
Using the statistical package SPSS , standard descriptive and comparative statistics procedures will analyze the collected data, and the obtained data will be presented graphically and tabularly.
