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: 1.88). 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.

  • [Show abstract] [Hide abstract]
    ABSTRACT: While healthy aging is associated with physiological changes that can impair control of trunk motion, few studies examine how spinal muscle responses change with increasing age. This study examined whether older (over 65years) compared to younger (20-45years) adults had higher overall amplitude and altered temporal recruitment patterns of trunk musculature when performing a functional transfer task. Surface electromyograms from twelve bilateral trunk muscle (24) sites were analyzed using principal component analysis, extracting amplitude and temporal features (PCs) from electromyographic waveforms. Two PCs explained 96% of the waveform variance. Three factor ANOVA models tested main effects (group, muscle and reach) and interactions for PC scores. Significant (p<.0125) group interactions were found for all PC scores. Post hoc analysis revealed that relative to younger adults, older adults recruited higher agonist and antagonistic activity, demonstrated continuous activation levels in specific muscle sites despite changing external moments, and had altered temporal synergies within abdominal and back musculature. In summary both older and younger adults recruit highly organized activation patterns in response to changing external moments. Differences in temporal trunk musculature recruitment patterns suggest that older adults experience different dynamic spinal stiffness and loading compared to younger adults during a functional lifting task. Copyright © 2014 Elsevier B.V. All rights reserved.
    Human Movement Science 12/2014; 38:262-80. DOI:10.1016/j.humov.2014.08.013 · 2.03 Impact Factor
  • Source
  • [Show abstract] [Hide abstract]
    ABSTRACT: Intra-abdominal pressure (IAP) and breathing behaviour are important preparative pre-lifting actions for functional stability during lifting. This study aimed to examine spontaneous changes in the peak rate of IAP development (Rate-IAP), peak IAP (Peak-IAP), the time of Rate- and Peak-IAP occurrence and respiratory volume in response to dynamic load lifting. Eleven healthy men performed quick dynamic deadlifting using 30, 45, 60 and 75 % of the isometric maximal lifting effort (iMLE). IAP was measured using an intrarectal pressure transducer. The spontaneous respiratory volume was calculated from air flow data using pneumotachography. The lifting motion onset was determined from the hip joint motion using an electrogoniometer. From 30 to 75 % of the iMLE, Rate-IAP occurred early from 2 +/- A 28 to -179 +/- A 16 ms (P < 0.01), whereas Peak-IAP occurred late from 165 +/- A 31 to 82 +/- A 23 ms (P = 0.12) relative to the lifting motion onset. Rate-IAP increased from 224 +/- A 47 to 507 +/- A 69 mmHg/s (P < 0.01), whereas Peak-IAP increased from 37 +/- A 8 to 90 +/- A 11 mmHg (P < 0.01) at 30-75 % of the iMLE. Rate-IAP strongly correlated with Peak-IAP at each lifting load (r = 0.94-0.97). Relative to the resting tidal volume, the inspiratory volume during pre-lifting significantly increased above 60 % of the iMLE, whereas expiratory volume significantly decreased at all lifting loads. Preparative pre-lifting behaviours alter IAP and breathing and are co-ordinated by the lifting load magnitude. These behaviours appear to be functionally important for dynamic lifting.
    Arbeitsphysiologie 07/2014; 114(11). DOI:10.1007/s00421-014-2944-4 · 2.30 Impact Factor


Available from