Study design: This study comprised a cross-sectional part and a prospective part.
Objective: To study whether low lumbar extension strength, high lumbar mobility, and high mobility-extension strength ratios are related to current and future low back pain in adolescents.
Summary of background data: Knowledge is sparse about the significance of lumbar mobility and strength for low back pain in adolescents.
Methods: The study population included all the adolescents in the eighth and ninth grades of a rural municipality (n = 44) and in an urban area (n = 61) during the 1996-1997 school year. At baseline, 88 adolescents (mean age, 14.7 years) participated in the study, giving a response rate of 84%. Low back pain was assessed by questionnaire as pain or discomfort in the low back during the preceding year. Sagittal lumbar mobility was tested by Schober's modified technique, and lumbar strength as static endurance extension strength. The follow-up part was conducted 3 years later, which included 98% of the adolescents.
Results: By bivariate and multivariate analyses in the cross-sectional part of the study, low back pain was found to be highly associated with low lumbar extension strength (P = 0.004-0.02), and high lumbar mobility-extension strength ratios (P = 0.005-0.04). Baseline low lumbar extension strength and high lumbar sagittal mobility-extension strength ratios (P = 0.03 and P = 0.02, respectively) predicted low back pain at follow-up assessment in multivariate analyses when control was used for gender, previous low back pain, physical activity, and well-being. No associations were found between plain sagittal mobility and low back pain.
Conclusion: 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.