The objective of this cross-sectional study was to investigate whether body mass index (BMI) and hip mobility are associated with low-back pain (LBP) in adolescents. The study population included all adolescents in 8th and 9th grades in a rural and in an urban area in Eastern Norway. Eighty-eight adolescents participated (mean age 14.7 years), making the response rate 84%. LBP was assessed by a questionnaire answered in the classrooms as pain/discomfort in the low back during the preceding year. Body height and weight were measured, and BMI was calculated. Hip mobility was measured as active movements by a goniometer. The level of significance was set to P< or =0.05. In bivariate analysis for the whole group, LBP was associated positively with a higher than mean BMI, while LBP among boys was associated with a less than mean hip flexion, internal rotation, and hamstrings flexibility. In multiple regression analyses, adjusting for gender and well-being, LBP was associated with a higher than mean BMI, a less than mean hamstrings flexibility, and a less than mean hip flexion. The results suggest further prospective research to investigate whether poor hip mobility and high BMI may predict juvenile LBP.

The study findings support theories suggesting insufficient strength and stability in the low back as important factors for both concurrent and future low back pain in adolescents.

Health promotion measures in order to increase physical activity should include environmental and policy approaches. Studies in natural living environments such as rural and urban areas may provide valuable information about the effects of environmental factors on physical activity. The present study was performed among 88 adolescents living in one rural and one urban area in Norway, with particular focus on the availability of cycling tracks and walking trails. The study showed that both rural and urban adolescents spent more time on sedentary activities, such as watching TV/video and playing TV/data-games, than on regular physical activity. No differences were observed between the two groups in regard to activity patterns. However, the median distance the urban adolescents walked or cycled to school was three times greater than the median distance the rural adolescents walked or cycled to a bus stop or to school. The urban adolescents also walked or cycled more to regular activities than the rural ones. Positive correlations were found between walking or cycling from home to school and walking or cycling to regular activities. In multiple regression analysis, urban area, female gender and distance walked or cycled to school or bus stop predicted increased walking or cycling to activities. The results confirm other studies on adolescents, showing that much more time is spent on sedentary rather than on physical activity. Knowledge is still lacking concerning predictors of sedentary and general physical activity, but the results indicate that access to cycling tracks and walking trails in residential areas may increase both walking or cycling to school and to leisure activities. A relevant strategy for health promotion may therefore be to make cycling tracks and walking trails accessible; some passive transport both to school and to leisure activities may thus probably be replaced by walking or cycling.

The findings indicate a persistent, but changeable, trend in LBP from midadolescence until late adolescence. The consistency and the high rates of reports of LBP provoked by manual work and sitting imply needs for more research on the persistence of LBP, and on relevant interventions during school age.