Spinal stability and role of passive stiffness in dynamic squat and stoop lifts

B. Bazrgari, A. Shirazi-Adl

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


The spinal stability and passive-active load partitioning under dynamic squat and stoop lifts were investigated as the ligamentous stiffness in flexion was altered. Measured in vivo kinematics of subjects lifting 180N at either squat or stoop technique was prescribed in a nonlinear transient finite element model of the spine. The Kinematics-driven approach was utilized for temporal estimation of muscle forces, internal spinal loads and system stability. The finite element model accounted for nonlinear properties of the ligamentous spine, wrapping of thoracic extensor muscles and trunk dynamic characteristics while subject to measured kinematics and gravity/external loads. Alterations in passive properties of spine substantially influenced muscle forces, spinal loads and system stability in both lifting techniques, though more so in stoop than in squat. The squat technique is advocated for resulting in smaller spinal loads. Stability of spine in the sagittal plane substantially improved with greater passive properties, trunk flexion and load. Simulation of global extensor muscles with curved rather than straight courses considerably diminished loads on spine and increased stability throughout the task.

Original languageEnglish
Pages (from-to)351-360
Number of pages10
JournalComputer Methods in Biomechanics and Biomedical Engineering
Issue number5
StatePublished - 2007

Bibliographical note

Funding Information:
The work was supported by grants from the NSERC-Canada, IRSST-Québec and Aga Khan Foundation.


  • Dynamic lifting
  • Finite element
  • Kinematics
  • Muscle force
  • Passive stiffness
  • Stability

ASJC Scopus subject areas

  • Bioengineering
  • Biomedical Engineering
  • Human-Computer Interaction
  • Computer Science Applications


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