Transversus abdominis (TrA) and lumbar multifidus (LM) are two deep trunk muscles implicated in maintaining spinal stability at rest and during physiological movements. A number of research studies have found that people with acute, chronic or recurrent low back pain (LBP) show abnormal changes in the physical characteristics (e.g. shape, dimension, composition, and function) of these muscles as compared to their asymptomatic counterparts. As such, different TrA/LM-targeted interventions have been designed to restore the abnormal physical characteristics of TrA/LM in an attempt to alleviate the symptoms of LBP and to reduce the risk of LBP recurrence.
Our previous systematic review has found that various baseline physical characteristics of TrA/LM cannot predict LBP clinical outcomes (i.e. pain intensity or LBP-related disability). However, there are inconsistent findings regarding the relation between changes in physical characteristics of TrA/LM during treatment or at discharge and the corresponding changes in clinical outcomes. Collectively, knowing which changes in characteristics are associated with treatment outcomes would help clinicians apply TrA/LM-targeted treatments with improved confidence and may help design interventions to increase success. Therefore, we systematically searched and reviewed the literature to summarize evidence regarding an association between changes in characteristics of TrA/LM muscles following nonsurgical interventions and the corresponding changes in clinical outcomes of patients with nonspecific LBP. We also reviewed if the relation between changes in characteristics of TrA/LM over time and the respective changes in clinical outcomes was affected by other factors (e.g. treatment types).
Our review identified 15 relevant articles from six medical databases. We found that improvements in LBP or LBP-related disability following nonsurgical treatment tended to be unrelated to the corresponding changes in characteristics of TrA. The relation between post-treatment changes in characteristics of LM and clinical improvements remains uncertain. Interestingly, although motor control exercise is generally thought to restore the dimension and motor control of TrA/LM in patients with LBP, the included studies that solely investigated motor control exercise did not support any relation between changes in TrA/LM characteristics over time and the corresponding changes in clinical outcomes of patients with nonspecific LBP.
Since many of the included studies did not adjust for confounders, these findings should be interpreted with caution. Future studies should adjust for various confounders (e.g. psychological factors) in order to uncover the potential relation between temporal changes of TrA/LM and the corresponding changes in LBP outcomes. Further, because many included studies did not demonstrate changes in TrA/LM characteristics, future studies should investigate the optimum treatment intensity and/or duration to allow for more changes to be detected in both the muscles and the clinical outcomes.
About Arnold Wong
Arnold Wong is a PhD candidate in the Faculty of Rehabilitation Medicine at the University of Alberta under Dr. Greg Kawchuk’s supervision. After working as a physiotherapist in Hong Kong for several years, he gradually developed low back pain himself. In order to find the best treatment available, he was determined to pursue a PhD degree in spinal research. Specifically, he is interested in the interconnections between pain, spinal stiffness, trunk muscle activity and treatment outcomes. Since Arnold started his PhD studies, he has won 15 awards and scholarships (including the prestigious Alberta Innovates-Health Solutions Graduate Studentship Award) from Canada and USA.
In his spare time, Arnold loves good pop and country music, yoga, jogging, volunteering and traveling. Arnold is also a two times Guinness world record holder for the world’s largest game of dodgeball.
Wong AY, Parent EC, Funabashi M, & Kawchuk GN (2013). Do changes in transversus abdominis and lumbar multifidus during conservative treatment explain changes in clinical outcomes related to non-specific low back pain? A systematic review. J Pain PMID: 24184573