Although approximately 60 to 80% of people experience low back pain (LBP) at least once in their lifetime, the exact causes of LBP remain unknown in 90% of the cases (known as non-specific LBP). Intriguingly, scientists have noted that patients with LBP commonly display abnormal changes in two trunk muscles, namely the transversus abdominis and the lumbar multifidus. Specifically, these muscles as measured by electromyography and/or ultrasonic imaging show delayed muscle activation during rapid arm movement and/or reduced muscle contraction. Some patients also demonstrate muscle atrophy and/or fat infiltration in their lumbar multifidus.
While it is unclear if LBP causes the abnormality of the two trunk muscles or vice versa, some research has shown that patients with more aberrant changes in any of the two muscles may have poorer prognosis and are more likely to benefit from motor control exercises. Thus, we systematically searched and reviewed relevant literature to determine if there is evidence that baseline characteristics of transversus abdominis and lumbar multifidus can predict clinical outcomes of non-specific LBP.
What did we find? To our surprise, we only identified five relevant articles from six medical databases. Based on the findings of these articles, we concluded that deficits in transversus abdominis or lumbar multifidus at baseline tended not to be related to the short- or long-term clinical outcomes. However, patients with poorer transversus abdominis muscle contraction might have better recovery if they received motor control exercises rather than general exercises.
Many questions remain in this research area. We still don’t know whether the trunk muscle change is the result or the cause of LBP. We are uncertain if baseline characteristics of these muscles may have a better predictive value in some patient subgroups. Given the small number of relevant studies and the potential benefits of prescribing motor control exercises for patients with poorer baseline transversus abdominis muscle conditions, future studies focusing on this area are warranted.
About Arnold Wong
Arnold 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 12 awards and scholarships (including the prestigious Alberta Innovates-Health Solutions Graduate Studentship Award) from Canada and USA.
In his time off, Arnold loves good pop and country music, yoga, jogging, volunteering and traveling. Most importantly, he loves spending quality time with his beloved.
Wong AY, Parent EC, Funabashi M, Stanton TR, & Kawchuk GN (2013). Do various baseline characteristics of transversus abdominis and lumbar multifidus predict clinical outcomes in non-specific low back pain? A systematic review. Pain PMID: 23867731