COMPARISON OF THE PERCEPTION OF BACKPACK WEIGHT WITH OBJECTIVE MEASUREMENTS. Nancy Talbott*1; A Bhattacharya2 1. Department of Rehabilitation Sciences, University of Cincinnati, Cincinnati, OH; 2. Department of Environmental Health, University of Cincinnati, Cincinnati, OH PURPOSE: The purpose of this study was to determine the relationship between the subject perception a student has of backpack weight and an objective measurement of the weight of that backpack. BACKGROUNDS/SIGNIFICANCE: Heavy backpacks have been suggested as contributing to adolescent backpain. Because surveys are often utilized to monitor backpack weight and accompanying symptoms, the perception a student has of the weight must be accurate. Clarification of the relationship between the perception of weight and actual weight will assist physical therapists in interpreting the subjective information provided by individuals wearing backpacks. SUBJECTS: Ten students in grades 6-9 were recruited from school organizations. METHODS AND MATERIALS: Before school, each student was required to wear their normal backpack. After putting the backpack on, the students indicated to a parent if the backpack felt heavy, medium, or light. Parents recorded this rating and then weighed the backpack on a scale. The process was repeated for five consecutive school days. ANALYSES: Descriptive analysis, confidence intervals, univariate and multivariate analyses were completed. RESULTS: Backpack weight, when rated light by students, ranged from 7 to 28 lbs; when rated medium ranged from 15 to 30lbs; and when rated heavy, the range was 21 to 34lbs. Mean ratings were 17.62lbs (SEM 1.64lbs) for a rating of light, 20.12lbs(SEM 0.69lbs) for a rating of medium, and 28.23lbs(SEM 1.3lbs) for a rating of heavy. Values for the ratings were significantly different and significantly correlated with measured backpack weight. Multivariate analysis indicated that backpack weight was significantly associated with backpack rating and varied significantly between subjects. CONCLUSIONS: While the range for backpack weight appears large, students appear able to differentiate changes in backpack weight on a daily basis. Perception is consistent among students but varies between students. FUNDING SOURCE: Department of Environmental Health, College of Medicine, University of Cincinnati. No material gain by the authors. KEYWORDS: backpack, weight, surveys Copyright 2009 by the American Physical Therapy Association. Requests for reprints should be directed to the corresponding author of the article. Educators, students, and other academic customers may receive permission to reprint copyrighted material from Physical Therapy (ISSN 1538-6724) by contacting the Copyright Clearance Center Inc, 222 Rosewood Dr, Danvers, MA 01923. Other types of customers who want permission to reprint should contact the APTA Editorial Office, Attn: Physical Therapy.