BACKGROUND AND OBJECTIVE: Low back pain (LBP) is a musculoskeletal disorder and a relatively common complaint. Muscles, as the most important stabilizers of the spine, are impaired in patients with LBP. The aim of this study is to compare the symmetry of abdominal muscle size in the dominant and non-dominant sides as well as the painful and painless sides between healthy adolescents and adolescents with LBP.

METHODS: This case-control study was conducted on 80 healthy adolescents and 80 adolescents with chronic nonspecific LBP, aged 15 to 18 years. Samples were chosen using convenience sampling method while being matched in terms of height, weight and body mass index. First, the demographic data were collected; then, their abdominal muscle size (transverse abdominus, internal oblique and external oblique) and intra-abdominal fat were measured by sonography.

FINDINGS: The difference in mean value and possibility value for transverse abdominus (p=0.024 and 0.189), internal oblique (p=0.000 and 0.861), external oblique (p=0.031 and 0.287) and intra-abdominal fat (p=0.762 and 0.081) was significant between the two groups in term of abdominal muscle size while the difference in intra-abdominal fat size was not statistically significant. Results also revealed a statistically significant difference in abdominal muscle size (except for external oblique and intra-abdominal fat) between the dominant and non-dominant sides (p<0.05) and between the painful and painless sides in adolescents with LBP (p<0.05).

CONCLUSION: The results of the present study demonstrated that abdominal muscle size in dominant and painful side is smaller than non-dominant and painless side.