This study investigates the prevalence, physical complaints, and impacts of heavy backpack use among junior high school students, with a focus on understanding how the weight and design of backpacks affect students' physical well-being and academic efficiency. The study was underpinned by the ergonomic theory. Using a descriptive survey design, data were collected from 300 respondents who were sampled using stratified random sampling technique. The questionnaire data was analysed via means, standard deviation and independent samples t-test. The findings reveal that heavy backpack use is common among students, with many reporting physical discomfort, including back pain, shoulder soreness, and fatigue. These complaints significantly affect students' mobility, posture, and concentration in class. Additionally, backpack design plays a crucial role in alleviating or exacerbating these issues, with well-designed backpacks improving students' ability to manage school materials and reducing physical strain. The implications of these findings highlight the need for ergonomic interventions and design improvements to reduce the adverse effects of heavy backpacks on students' health and academic performance. Recommendations include promoting awareness of backpack weight limits, encouraging the use of ergonomically designed backpacks, and incorporating guidelines for safe backpack use in school health programmes.