Development and testing of the BONES physical activity survey for young children

Background: Weight-bearing and high intensity physical activities are particularly beneficial for stimulating bone growth in children given that bone responds favorably to mechanical load. While it is important to assess the contribution and impact of weight-bearing physical activity on health outcomes, measurement tools that quantify and provide information on these activities separately from overall physical activity are limited. This study describes the development and evaluation of a pictorial physical activity survey (PAS) that measures children's participation and knowledge of high-intensity, weight-bearing ("bone smart") physical activity. Methods: To test reliability, two identical sets of the PAS were administered on the same day to 41 children (mean age 7.1 +/- 0.8 years; 63% female) and compared. To test validity, accelerometry data from 40 children (mean age 7.7 +/- 0.8 years; 50% female) were compared to data provided by the PAS. Agreements between categorical and ordinal items were assessed with Kappa statistics; agreements between continuous indices were assessed with Spearman's correlation tests. Results: The subjects produced reliable results in all 10 physical activity participation items (kappa range: 0.36-0.73, all p < 0.05), but less reliable in answering if the physical activities were "bone smart" (kappa range: -0.04-0.66). Physical activity indices, including metabolic equivalent time and weight-bearing factors, were significant in test-retest analyses (Spearman's r range: 0.57-0.74, all p<0.001). Minutes of very vigorous activity from the accelerometer were associated with the self-reported weight-bearing activity, moderate-high, and high activity scores from the PAS (Spearman's r range: 0.47-0.48, all p<0.01). However, accelerometer counts, counts per minute, and minutes of moderate-vigorous and vigorous activity were not associated with the PAS scores. Conclusions: Together, the results of these studies suggest that the PAS has acceptable test-retest reliability, but limited validity for early elementary school children. This survey demonstrates a first step towards developing a questionnaire that measures high intensity, weight-bearing activity in schoolchildren.