Article

Abdominal muscle activation increases lumbar spinal stability: Analysis of contributions of different muscle groups

Department of Orthopaedics and Rehabilitation, University of Vermont, Burlington, USA.
Clinical biomechanics (Bristol, Avon) (Impact Factor: 1.97). 05/2011; 26(8):797-803. DOI: 10.1016/j.clinbiomech.2011.04.006
Source: PubMed

ABSTRACT

Antagonistic activation of abdominal muscles and increased intra-abdominal pressure are associated with both spinal unloading and spinal stabilization. Rehabilitation regimens have been proposed to improve spinal stability via selective recruitment of certain trunk muscle groups. This biomechanical analytical study addressed whether lumbar spinal stability is increased by such selective activation.
The biomechanical model included anatomically realistic three-layers of curved abdominal musculature, rectus abdominis and 77 symmetrical pairs of dorsal muscles. The muscle activations were calculated with the model loaded with either flexion, extension, lateral bending or axial rotation moments up to 60 Nm, along with intra-abdominal pressure up to 5 or 10 kPa (37.5 or 75 mm Hg) and partial bodyweight. After solving for muscle forces, a buckling analysis quantified spinal stability. Subsequently, different patterns of muscle activation were studied by forcing activation of selected abdominal muscles to at least 10% or 20% of maximum.
Spinal stability increased by an average factor of 1.8 with doubling of intra-abdominal pressure. Forcing at least 10% activation of obliques or transversus abdominis muscles increased stability slightly for efforts other than flexion, but forcing at least 20% activation generally did not produce further increase in stability. Forced activation of rectus abdominis did not increase stability.
Based on analytical predictions, the degree of stability was not substantially influenced by selective forcing of muscle activation. This casts doubt on the supposed mechanism of action of specific abdominal muscle exercise regimens that have been proposed for low back pain rehabilitation.

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Available from: Sharon Henry, Oct 28, 2015
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    • "Sounding somewhat like a paradox, the question is vital: why should core stability be improved in chronic LBP sufferers if there is no strong evidence of tissue damage or structural body changes due to instability? And even if each case of chronic LBP was characterized by instability, the isolated training of only deep muscles should seem to be insufficient (Stokes et al., 2011; Gnat et al., 2013). Addressing this issue, a Canada-based research group has adopted a contrasting approach, which highlights the prominent role of more superficial muscles i.e. obliqus internus and externus abdominis and quadratus lumborum (McGill, 2002; Grenier and McGill, 2007; Brown and McGill, 2009) in the lumbar spine stability processes. "
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    • "For the lateral abdominal muscles, no significant difference was found in muscle thickness ratio depending on the selected angles (30 o , 60 o , 90 o ) during the two exercises . We considered that lateral abdominal muscles might mainly act on the maintenance of trunk stability instead of the exercise motion itself, leading to the results differing from those of the RA muscle[6,12,16]. In addition, we thought that there might be differences in muscle activities depending on the angles when doing the exercises, including trunk rotation or lateral bending motions; it is considered that additional studies are needed to be conducted in the future. "
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    Full-text · Article · Jan 2015 · Annals of Rehabilitation Medicine
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    • "It is believed that trunk muscle weakness is an important risk factor for this disorder [5]. Additionally, the abnormal patterns of muscle activity could affect the biomechanics of spinal movements and result in mechanically induced pain [6–8]. "
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