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


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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    • "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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    ABSTRACT: Objective: To evaluate trunk muscle strength and EMG activation during isokinetic axial rotation at different angular velocities. Method: Twenty-four healthy young men performed isokinetic axial rotation in right and left directions at 30, 60, and 120 degrees per second angular velocity. Simultaneously, surface EMG was recorded on external oblique (EO), internal oblique (IO), and latissimus dorsi (LD) bilaterally. Results: In each direction, with the increase of angular velocity, peak torque decreased, whereas peak power increased. During isokinetic axial rotation, contralateral EO as well as ipsilateral IO and LD acted as primary agonists, whereas, ipsilateral EO as well as contralateral IO and LD acted as primary antagonistic muscles. For each primary agonist, the root mean square values decreased with the increase of angular velocity. Antagonist coactiviation was observed at each velocity; however, it appears to be higher with the increase of angular velocity. Conclusion: Our results suggest that velocity of rotation has great impact on the axial rotation torque and EMG activity. An inverse relationship of angular velocity was suggested with the axial rotation torque as well as root mean square value of individual trunk muscle. In addition, higher velocity is associated with higher coactivation of antagonist, leading to a decrease in torque with the increase of velocity.
    04/2014; 2014:623191. DOI:10.1155/2014/623191
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    • "A better comprehension of how the different types of exercises recruit the RA is a necessary step for the development of specific abdominal routines that better attend customized needs of patients or trainees [2] [11] [12] [13]. Several studies investigated the effectiveness of CK in activating the RA for strength, pain relief, and rehabilitation after specific lesions [6] [7] [8] [10] [14]. Few studies focused, however, on the "
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    ABSTRACT: The aim of this feasibility study was to contrast rectus abdominis (RA) muscle strength and electrical activ-ity after two abdominal training protocols, conven-tional kinesiotherapy (CK) and Pilates mat exercises (PME). 13 participants were randomized to one of two groups: CK and PME, and were trained accord-ingly. The upper rectus abdominis (URA) and lower rectus abdominis (LRA) were independently exam-ined and inter and intra group comparisons were done. Findings demonstrate a significant increase in RA strength after both protocols, relative to baseline. Significantly increased electrical activation was seen in the URA after CK. Training with PME, although as efficient as CK in strength improvement, produced decreased activation level of muscles. CK training induced an opposite result. The differences after training suggest that CK and PME training pro-grammers may strength RA, but the neuromuscular activation strategies for that are not the same. PME can be incorporated into protocols to improve ab-dominals strength, and trunk stabilization.
    Journal of Biomedical Science and Engineering 12/2013; 06(12). DOI:10.4236/jbise.2013.612146
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    • "This causes the system to become more robust in terms of stability and less sensitive to changes in the applied load. On the other hand, numerical simulations carried out by Stokes et al. (2011) to study the improvement of lumbar spine stability as a function of the activation of certain groups of muscles also indicate that there are gains in stability by increasing the stiffness of certain groups of muscles, although the authors point out that the gain in stability might not be significant. "
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    ABSTRACT: We considered various stability issues related to biomechanical models of the spine, taking as our point of departure the scalar quantities proposed in Howarth et al. (2004). We discussed their significance and applicability by considering some mechanical toy models. In particular, we analysed the relevance of the behaviour of some of these measurements, namely, the determinant of the Hessian matrix and other quantities containing information of a similar spectral nature, and the role they may play in this type of studies. We showed that although in some cases these markers contain information about the load acting on the subject, this information may also be masked and not be detectable from these indexes. These models also allowed us to see how a system with these characteristics may become highly sensitive even to small load changes, and prompted us to put forward the hypothesis that trying to preserve stability at all costs might, under some circumstances, be an actual cause for system damage.
    Journal of the Mechanical Behavior of Biomedical Materials 04/2012; 14C:19-28. DOI:10.1016/j.jmbbm.2012.04.006 · 3.42 Impact Factor
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