Jump to comment:

• another view, another challenge forLBP
  Bernard Liew
  Published on: 11 October 2022

• Published on: 11 October 2022

  another view, another challenge forLBP

  • Bernard Liew, physiotherapy student

  Dear editor,

  I read with great interest the latest editorial on the role Transversus Abdominis (TrA) has on lumbar stability [Hodges, 2008]. The role of muscles that contribute to stability has been a matter of great controversy. This controversy, in my opinion, stems from the fact that different school of thoughts espouses their opinions in subtle ways that sway readers in directions that ultimately lead to misin...

  Show More

  Dear editor,

  I read with great interest the latest editorial on the role Transversus Abdominis (TrA) has on lumbar stability [Hodges, 2008]. The role of muscles that contribute to stability has been a matter of great controversy. This controversy, in my opinion, stems from the fact that different school of thoughts espouses their opinions in subtle ways that sway readers in directions that ultimately lead to misinterpretation. Take for example the role of TrA, it has been taken for granted that it is the most important trunk stabilizing muscle. This view is certainly not supported by the Queensland group of researchers who pioneered this exciting field of research [Richardson et al., 1999]. Whilst they have not directly mention that the TrA is the most crucial stabilizer, it is the manner in which the information is disseminated and taught, either through professional entry level programs, journals or workshops that create this misinterpretation. Those actively involved in the research of lumbar control in low back pain correctly pointed out that ALL muscles play a role in trunk stability [Kavic et al., 2004]. By taking this view and combining with available literature on motor control in neurology, I would like to offer another view on how the various trunk muscles are coordinated to offer trunk stability. There are many theories within the motor control literature that seek to explain how movement and stability are both brought about in harmonious synchrony. No one theory can adequately explain all the observed complexities. One common theory is the Dynamic Action Theory of motor control. Without elaborating too much into the theory [see Shumway &Woollacott, 2007], the dynamic action theory looks at motor control from the broader study of dynamics within the physical world [Kelso & Tuller, 1984]. This theory predicts discrete changes in the behavior of a system when there are changes in the linear dynamics of a moving system. Take walking for example, as a person walks at an increasingly faster speed, there is a discrete point when that person will transit into running. What causes the change in behavior is the ‘control parameter’, in this case, velocity. A person walks instead of runs at a certain velocity because that behavior is the preferred pattern of movement, termed the ‘Attractor states’. Let’s see how this theory can explain certain research and clinical phenomena in normal LBP people. When test subjects move their arms unilaterally [Hodges & Richardson, 1997] the pattern of neuromuscular control discovered could be the ‘attractor state’ i.e. the most stable pattern (note it is stability in the physical world). The same goes for the observation by Allison et al. [2008]. The reason why conflicting reports of TrA activation could very well be explained by different ‘attractor states’ when different experimental paradigms used. I must concede that I do not know what is the ‘control parameter’ that dictates whether TrA is activated anticipatorily. Since movement and stability emerge as an interaction between the specific individual, task and context, the view that because TrA shows feedforward activity in unilateral arm raise, TrA will show anticipatory activity in all tasks is quite a simplistic and naïve view. In LBP people, there is the view that excessive activity of global muscles may represent dysfunctional patterns of control [Radebold et al., 2000]. Another way to look at it could be that such pattern could very well be the most stable pattern of control. Again by stable, I mean in terms of dynamics in the physical world. This is the ‘new attractor state’. This state may be manifested due to a certain ‘control parameter’ being now present. If one is to change the ‘current attractor state’, one has to bring about a change in a certain ‘control parameter’ to a threshold (it could be arm movement speed). Obviously, the dynamic action theory cannot account for all the observations within the human repertoire of movement. We need more than one theory to explain, test hypothesis, create new practice regimes and reevaluate the findings. A current theory in vogue is the Adam’s Close and Open loop theory, which standing alone is INADEQUATE. It is in my sincere hope that we can move on from this current debate that focuses too narrowly on isolated muscles in action into a bigger picture framework of control. But certainly, debates like I see in this editorial are creating healthy discussion and opinions like this.

  References

  1. Hodges P. Transversus abdominis: a different view of the elephant. British J Sports Med 2008;42:941-944

  2. Allison GT. Transversus abdominis and core stability: has the pendulum swung? Br J Sports Med 2008;42:630–1.

  3. Kavic N, Grenier S, McGill S. determining the stabilizing role of individual torso muscles during rehabilitation exercises. Spine 2004; 29(11): 1254-1265

  4. Richardson C, Jull G, Hodges P, et al. (1999). Therapeutic exercise for spinal segmental stabilization in low back pain. Edinburgh, Scotland: Churchill Livingstone

  5. Hodges PW, Richardson CA. Feedforward contraction of transversus abdominis is not influenced by the direction of arm movement. Exp Brain Res 1997; 114: 362–70.

  6. Shumway-Cook A, Woollacott M. (2007). Motor control: Translating research into clinical practice. Lippincott Williams & Wilkins

  7. Kelson JAS, Tuller B. A dynamic basis for action systems. In: Gazanniga MS eds. Handbook of cognitive neuroscience. New York: Plenum, 1984: 321- 356

  8. Radebold A, Cholewicki J, Panjabi MM, Patel TC. Muscle response pattern to sudden trunk loading in healthy individuals and in patients with chronic low back pain. Spine 25: 947-954

  Show Less

  Conflict of Interest:
  None declared.

  • Back to top