Prolonged trunk flexion can increase spine loads during a subsequent lifting task: An investigation of the effects of trunk flexion duration and angle using a sagittally symmetric, viscoelastic spine model

N. Toosizadeh, M. A. Nussbaum

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Load-relaxation of the human trunk following prolonged flexion has been observed earlier, yet the adverse effects of such viscoelastic behaviors on performing demanding tasks (e.g. lifting) remain poorly understood. Theoretically, trunk stiffness reduces following flexion exposures and requires a compensatory increase in paraspinal muscle activation and spine loads. Here, a multi-segment model with nonlinear viscoelastic properties was developed. After evaluating the model, it was used to predict changes, due to a range of trunk flexion exposures, in several outcome measures (i.e. peak spine load, peak axial stiffness and absorbed energy) at L5/S1 during simulated lifting. All three measures increased during lifting following flexion exposures, including a ~ 9% (~ 284 N) increase in spine loads, and these changes were magnified by increasing flexion duration and angle. These results support prior epidemiological evidence that occupational low back injury risk is elevated when prolonged trunk flexion along with lifting are required. Further, the dependency of spine loads on loading conditions was determined in response to several flexion angles and loading durations. The current modeling approach is considered as an initial step toward implementing Kelvin-solid models in future viscoelastic spine models.

Original languageEnglish (US)
Article number1350022
JournalJournal of Musculoskeletal Research
Volume16
Issue number4
DOIs
StatePublished - Dec 2013
Externally publishedYes

Keywords

  • Biomechanics
  • Internal loads
  • Lifting
  • Lumbar spine
  • Prolonged task
  • Viscoelastic

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine

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