Study Design: A multifactorial cross-sectional nonexperimental design. Objectives: To collectively investigate the association among 17 mechanical factors and occurrence of low back pain (LBP). Background: Several physical characteristics, based on assumptions, clinical findings, and scientific experiments, have been associated with the development of LBP. Controversy exists regarding the degree of association between some of these physical characteristics and LBP. Information regarding the degree of association of each factor to LBP is needed for effective prevention and appropriate treatment strategies.
Methods and Measures:A total of 600 subjects participated in this study. Subjects were categorized into 4 groups: asymptomatic men (n = 150, age [mean ± SD] = 43 ± 15 years), asymptomatic women (n = 150, age [mean ± SD] = 43 ± 13 years), men with LBP (n = 150, age [mean ± SD] = 43 ± 14 years), and women with LBP (n = 150, age [mean ± SD] = 43 ± 13 years). Seventeen physical characteristics were measured in each group and the relative association of each characteristic with LBP was assessed. Results: Among all the factors tested, endurance of the back extensor muscles had the highest association with LBP. Other factors such as the length of the back extensor muscles, and the strength of the hip flexor, hip adductor, and abdominal muscles also had a significant association with LBP. Conclusion: It appears that muscle endurance and weakness are associated with LBP and that structural factors such as the size of the lumbar lordosis, pelvic tilt, leg length discrepancy, and the length of abdominal, hamstring, and iliopsoas muscles are not associated with the occurrence of LBP. J Orthop Sports Phys Ther 2002;32:447-460. Key Words: back extensor endurance, low back pain, lumbar lordosis, muscle length, muscle strength L ow back pain (LBP) is one of the most frequent healthrelated complaints in western societies. 110 Previous studies have indicated that 70% to 80% of the western population have had at least 1 episode of LBP in their lifetime. 110,120 Despite its detrimental association with social and workrelated activities, the exact cause of mechanical LBP has not yet been determined. Several factors, based on assumptions, clinical findings, and scientific experiments, have been associated with the development of LBP. However, with the use of different designs and testing procedures, controversial results have been reported in the literature.
