Biomechanical model predicting values of muscle forces in the shoulder girdle during arm elevation

Eric Berthonnaud, Melissa Morrow, Guillaume Herzberg, Kai Nan An, Joannes Dimnet

Research output: Contribution to journalArticlepeer-review


A three-dimensional (3D) geometric model for predicting muscle forces in the shoulder complex is proposed. The model was applied throughout the range of arm elevation in the scapular plan. In vitro testing has been performed on 13 cadaveric shoulders. The objectives were to determine homogeneous values of physiological parameters of shoulder muscles and to locate sites of muscular attachment to any bone of the shoulder complex. Muscular fiber lengths, lengths of contractile element (CE), and muscle volumes were measured, corresponding physiological cross-sectional area (PCSA) were calculated, and force/length muscle relations were found. An in vivo biplanar radiography was performed on five volunteers. The photogrammetric reconstruction of bone axes and landmarks were coupled with a geometric modeling of bones and muscle sites of attachment. Muscular paths were drawn and changes in lengths during movement have been estimated. Directions of muscle forces are the same as that of muscular path at the point of attachment to bone. Magnitudes of muscular forces were found from muscle lengths coupled with force/length relations. Passive forces were directly determined contrary to active muscle forces. A resulting active muscle force is calculated from balancing weight and passive forces at each articular center. Active muscle forces were calculated by distributing the resulting force among active muscles based on the muscular PCSA values.

Original languageEnglish (US)
Pages (from-to)643-666
Number of pages24
JournalJournal of Mechanics in Medicine and Biology
Issue number4
StatePublished - Dec 2010
Externally publishedYes


  • Blix curves
  • Shoulder muscles
  • geometric muscle modeling
  • muscle force modeling
  • physiological cross-sectional area (PCSA)
  • shoulder elevation

ASJC Scopus subject areas

  • Biomedical Engineering


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