Backpack Weight Affects Posture, Gait, And Forces Of Male Children With Obesity During Stair Descent

PURPOSE: To investigate the effects of backpack weight on body posture, gait pattern, and ground reaction forces in obese children to determine a safe limit for their backpack weight. METHODS: A total of 16 obese (age:11.2 ± 0.7 years, height: 148.8 ± 14.1 cm, body mass: 75.3 ± 16.0 kg, BMI: 29.8 ± 4.1 kg/m2) and 21 non-obese (age:11.1 ± 0.7 years, height: 152.2 ± 7.0 cm, body mass:48.1 ± 9.5 kg, BMI: 20.0 ± 3.1 kg/m2) schoolboys were recruited. Participants descended the stairs with or without a 15% of their body weight backpack for five trials, with a one-minute rest period between trials. Participants descended a staircase with or without carrying a backpack of 15% of their body weight, for five trials in each condition, with a one-minute rest period between trials. Two force plates and two high-speed video cameras were used to collect data during stair descent. A two-way analysis of variance with mixed design was performed to determine the effects of backpack weight and obesity condition. RESULTS: No significant interactions or obese effects were detected. Significant backpack effects were detected in the following variables. Compared to without-backpack conditions, the anterior trunk inclination angle (with:11.87 ± 4.02°, without:8.55 ± 2.61°, p = 0.015), standing phase duration (with:65.69 ± 2.61%, without:61.68 ± 2.04%, p = 0.002), and peak vertical ground reaction force (with:180.99 ± 19.00%BW, without:161.87 ± 16.86%BW, p = 0.022) increased, while the swing phase duration (with:38.32 ± 1.57%, without:34.31 ± 2.07%, p = 0.022) decreased during with-backpack conditions. CONCLUSION: Backpack weight alters children's gait patterns. For children who are obese or non-obese, backpacks weighing more than 15 percent of their body weight can lead to postural instability.