The effect of core stability and general exercise on abdominal muscle thickness in non-specific chronic low back pain using ultrasound imaging

Background: There is a controversy regarding whether core stability exercise (CSE) is more effective than general exercise (GE) for chronic LBP. To compare different exercises regarding their effect on improving back strength and stability, performance of abdominal muscles is a useful index. Ultrasound imaging for measuring muscle thickness could be used to assess muscle performance. Objective: The aim of this study was to compare CSE and GE in chronic LBP using ultrasound imaging for measurement of thickness of the deep stabilizing and main global trunk muscles in non-specific chronic LBP. Methods: Each program included 16 training sessions three times a week. Using ultrasound imaging, four transabdominal muscle thickness were measured before and after the intervention. Disability and pain were measured as secondary outcomes. Results: After the intervention on participants (n = 43), a significant increase in muscle thickness (hypertrophy) was seen only in right and left rectus abdominis in the GE group, but significant difference to the CSE group was only on the right side. Disability and pain reduced within the groups without a significant difference in the change between them. Conclusions: The present results provided evidence that only GE increased right and left rectus muscle thickness. The only significant difference between CSE and GE groups was the right rectus thickness. As rectus is a global muscle, the effect of GE on strength improvement (one side stronger than the other) may have a negative effect on motor control of lumbopelvic muscles and possibly increase the risk of back pain occurring or becoming worse, though this was not observed in the present study.