The purpose of this study was to evaluate feed-forward contraction of the transversus abdominis and thickness of the transversus abdominis, obliquus internus, and obliquus externus during calm and standardized respiration in low back pain patients and pain-free subjects.

Low back pain patients have alterations in abdominal wall function, especially in the feed-forward activation of transversus muscle during limbs movements. However, there are no reports on the abdominal function in low back pain patients during physiological respiratory movement.

Inclusion Criteria:

• For the low back pain group: women with history of non-specific chronic low back pain for more than three months
• For the pain-free group: pain-free women

Exclusion Criteria:

• For both groups were: pregnancy, neurological condition, obesity (body mass index: BMI >30), or previous spine or abdominal surgery.
• For the low back pain group: rheumatology diseases other than low back pain.
• For the pain-free group: any rheumatology disease.

Community sample