A Recommendation for the Backpack Load Limit of Middle School Students Based on Physiological and Psychophysical Measurements

Open Access
Bauer, Denise Helen
Graduate Program:
Industrial Engineering
Doctor of Philosophy
Document Type:
Date of Defense:
August 31, 2007
Committee Members:
  • Andris Freivalds, Committee Chair
  • Leah C Newman, Committee Member
  • Ling Rothrock, Committee Member
  • Richard Donovan Koubek, Committee Member
  • John Henry Challis, Committee Member
  • children and backpacks
  • backpack load limits
Over 40 million students in the United States use a backpack to carry items to and from school everyday as it is designed to hold different objects in an organized manner. However, the load of children’s backpacks has caused debate over the recent years. Whether the problem is thought to be related to the belief that textbooks are too large for children to carry or the backpacks are loaded and carried incorrectly, the consensus is that there is a definite safety issue present and a need to be proactive in providing recommendations before severe health issues present themselves. The purpose of the planned research is to use electromyography (EMG), posture evaluation, heart rate, and ratings of perceived exertion and perceptions of pain to find an acceptable backpack load limit. These experiments will help narrow the acceptable load limit by providing additional analysis to the current literature on backpack loads and children. The study will also explore the possible differences between a backpack with many ergonomic features and a more generic backpack with only a couple ergonomic features. It may be that the type of backpack used is more of a problem than the actual load. Twenty middle school students aged 11 to 14 (10 female and 10 male) volunteered for the study. Two backpacks were used in the study: one with standard comfort features and one with ergonomic features. The subjects completed two tests: standing stationary and walking on a treadmill. For both tests, the subjects first had two trials without any load (0%) then two trials with each of the two backpacks at loads of 10, 15, and 20% of the subject’s body weight (BW). EMG activity of the trapezius, latissimus dorsi, and erector spinae was collected using triode surface electrodes while the subjects stood for 3 min. For the walking trials, the subjects walked on a treadmill at 2.41 km/hr for 3 min. In both tests, every 1 min the subjects were asked to give a Borg-RPE and their heart rate. The subjects were also asked to rate the pain they felt in their shoulders, middle back, lower back, and whole body using the Borg CR10 Scale of Perceived Pain. The study was conducted to gather more evidence on the vital problem of children carrying backpacks that may cause long-term harm, and to attempt to support one load limit over the other. The possibility of needing to adjust the Borg RPE-Scale for the study age was also explored. The research indicated that: (1) The CR10 ratings and trunk forward lean for the walking trial indicated a possible load limit of 10% BW due to the significant difference between 10 and 15% BW. (2) There was no significant difference between backpacks, concluding that the best backpack may just be a matter of personal choice. (3)The data was inconclusive on whether the RPE-Scale should be adjusted for children. Further studies on various dynamic activities should be explored. Future research should be conducted to include factors such as testing actual backpack mass instead of %BW, using BMI to group subjects, more subjects for each age, and different backpacks to generalize the results for the general population.