Effect of sub-optimal neuromotor control on the hip joint load during level walking

Saulo Martelli, Fulvia Taddei, Angelo Cappello, Serge Van Sint Jan, Alberto Leardini, Marco Viceconti

Research output: Contribution to journalArticlepeer-review

Abstract

Skeletal forces are fundamental information in predicting the risk of bone fracture. The neuromotor control system can drive muscle forces with various task- and health-dependent strategies but current modelling techniques provide a single optimal solution of the muscle load sharing problem. The aim of the present work was to study the variability of the hip load magnitude due to sub-optimal neuromotor control strategies using a subject-specific musculoskeletal model. The model was generated from computed tomography (CT) and dissection data from a single cadaver. Gait kinematics, ground forces and electromyographic (EMG) signals were recorded on a body-matched volunteer. Model results were validated by comparing the traditional optimisation solution with the published hip load measurements and the recorded EMG signals. The solution space of the instantaneous equilibrium problem during the first hip load peak resulted in 105 dynamically equivalent configurations of the neuromotor control. The hip load magnitude was computed and expressed in multiples of the body weight (BW). Sensitivity of the hip load boundaries to the uncertainty on the muscle tetanic stress (TMS) was also addressed. The optimal neuromotor control induced a hip load magnitude of 3.3BW. Sub-optimal neuromotor controls induced a hip load magnitude up to 8.93BW. Reducing TMS from the maximum to the minimum the lower boundary of the hip load magnitude varied moderately whereas the upper boundary varied considerably from 4.26 to 8.93BW. Further studies are necessary to assess how far the neuromotor control can degrade from the optimal activation pattern and to understand which sub-optimal controls are clinically plausible. However we can consider the possibility that sub-optimal activations of the muscular system play a role in spontaneous fractures not associated with falls.

Original languageEnglish
Pages (from-to)1716-1721
Number of pages6
JournalJournal of Biomechanics
Volume44
Issue number9
DOIs
Publication statusPublished - Jun 3 2011

Keywords

  • Hip loads
  • Level walking
  • Muscle force variability
  • Sub-optimal neuromotor control
  • Subject-specific musculoskeletal models

ASJC Scopus subject areas

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

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