fa آسیب شناسی ورزشی و حرکات اصلاحی Sport injury and corrective exercises پژوهشي Research Objective: Low back pain is one of the most important and prevalent disorders in the field of medical sciences which occurs in human societies. Different etiology is included for LBP, but researchers have put more attention into pelvic floor muscles dysfunction, recently. This led us to design a research in order to assess these muscles` function between healthy persons and chronic low back pain (CLBP) patients in the format of an abdominal maneuver by sonography. Materials & Methods: A total number of 37 individuals (22 healthy and 15 chronic non-specific low back pain subjects) were included. The amount of bladder displacement, during Valsalva maneuver, in comparison with resting position, was recorded through ultrasound (sonography). We used K.S and independent t-test in order to assess between groups. Results: No significant bladder base displacement difference observed between people with/without CLBP. However, there was an inclination to significant difference between groups. Conclusion: The results of these researches could possibly make us not to consider the pelvic floor dysfunctions as a main factor of lumbo-sacral instability in CLBP patients. valsalva maneuver, pelvic floor muscles, sonography 69 74 http://ptj.uswr.ac.ir/browse.php?a_code=A-10-29-2&slc_lang=fa&sid=1 حامد اسدی hamed.assadi@yahoo.com Yes اسماعیل ابراهیمی No امیرمسعود عرب No جواد صراف زاده No نورالدین کریمی No حکیمه آدی گوزلی No