Computation of trunk stability in forward perturbations-Effects of preload, perturbation load, initial flexion and abdominal preactivation

Ali Shahvarpour, Aboulfazl Shirazi-Adl, Christian Larivière, Babak Bazrgari

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Spine stability demand influences active-passive coordination of the trunk response, especially during sudden perturbations. The objective of this study was to look at the role of passive, stationary active and reflexive subsystems on spinal stability. Spine stability was evaluated here during pre- and post-perturbation phases by computing the minimum (i.e., critical) muscle stiffness coefficient required to maintain stability. The effects of pre-perturbation conditions (preloading, initial posture and abdominal antagonistic coactivation) as well as perturbation magnitude were studied. Results revealed that higher preload, initially flexed trunk posture and abdominal pre-activation enhanced pre-perturbation stiffness and stability. In contrast to the preload, however, larger sudden load, initial flexion and abdominal preactivation significantly increased post-perturbation stability margin. As a result, much lower critical muscle stiffness coefficient was required post-perturbation. Compared to the pre-perturbation phase, the trunk stiffness and stability substantially increased post-perturbation demanding thus a much lower critical muscle stiffness coefficient. Overall, these findings highlight the crucial role of the ligamentous spine and muscles (in both passive and active states) in augmenting the trunk stiffness and hence stability during pre- and post-perturbation phases; a role much evident in the presence of initial trunk flexion.

Original languageEnglish
Pages (from-to)716-720
Number of pages5
JournalJournal of Biomechanics
Issue number4
StatePublished - Feb 26 2015

Bibliographical note

Funding Information:
This study has been supported by grants from the Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST-Québec) and the Natural Sciences and Engineering Research Council of Canada (NCERC-Canada) . Authors thank Dr. André Plamondon and Mr. Hakim Mecheri for their advice, as well as Sophie Bellefeuille and Cynthia Appleby for their technical assistance during testing at IRSST׳s laboratory.

Publisher Copyright:
© 2015 Elsevier Ltd.


  • Co-activation
  • Flexion
  • Kinematics-driven model
  • Preload
  • Stability
  • Stiffness
  • Sudden forward load
  • Trunk

ASJC Scopus subject areas

  • Biophysics
  • Biomedical Engineering
  • Orthopedics and Sports Medicine
  • Rehabilitation


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