Study aim: Backpack carriage is a daily necessity for school-going children, but excessive loads and prolonged carrying durations may disrupt gait mechanics, potentially leading to musculoskeletal strain. The present study aimed to analyse the effect of progressive backpack weights and carrying durations on the contact time during the walking gait of school-aged boys. Additionally, it assessed the symmetry between left and right foot contact times under varying conditions.
Material and methods: A total of 85 healthy male students (mean age = 11.06 ± 0.76 years, height 143.50 ± 5.11 cm, body weight 36.00 ± 4.05 kg) from Delhi National Capital Region participated in the study. Contact time was recorded using the Zebris FDM pressure plate under five backpack weights (0%, 8%, 12%, 16%, and 20% of body weight) and five intervals (0, 5, 10, 15, and 20 minutes). A 5 × 5 repeated measures design was used. Descriptive statistics, paired-sample t-tests and two-way repeated measures ANOVA were employed to evaluate the effects of backpack weight and duration.
Results: Progressive backpack weights up to 12% of body weight increased contact time, reflecting biomechanical adjustments to maintain stability. However, loads of 16% and above caused fatigue, disrupting gait patterns. Prolonged carrying durations intensified these effects, leading to greater variability and asymmetry in contact time, particularly under heavier loads. Significant differences in contact time between the left and right foot were observed (p < 0.05), indicating uneven weight distribution and compensatory gait strategies. ANOVA findings confirmed a significant main effect of backpack weight, a significant interaction between weight and duration, and a statistically significant main effect of duration for the left foot.
Conclusions: The findings suggest that excessive backpack weight and prolonged carrying duration significantly alter foot contact time and gait symmetry, which may contribute to musculoskeletal stress in school-aged children. A threshold effect emerged, where both backpack weight and duration—independently and interactively—disrupted natural gait stability, particularly in the non-dominant limb. The study supports limiting backpack weight to 10–12% of body weight and reducing prolonged carriage duration. Future studies should incorporate multifactorial models and longitudinal tracking to better understand the long-term impact of load-induced gait adaptations.
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