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Muscle synergies based on a biomechanical biaxial isometric shoulder model minimizing fatigue

Nassajian Moghadam, M ; Sharif University of Technology

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  1. Type of Document: Article
  2. DOI: 10.1115/ESDA2010-25230
  3. Abstract:
  4. In this study we utilize the concept of synergy formation as a simplifying control strategy to manage the high number of degrees of freedom presented in the maintenance of the posture of the shoulder joint. We address how to find the muscle synergy recruitment map to the biomechanical demands (biaxial external torque) during an isometric shoulder task. We use a numerical optimization based shoulder model to obtain muscle activation levels when a biaxial external isometric torque is exposed at the shoulder glenohumeral joint. In the numerical simulations, different shoulder torque vectors parallel to the horizontal plane are considered. For each selected direction for the torque, the resulting muscle activation data are calculated and then used for grouping muscles in some fixed element synergies by nonnegative matrix factorization method Next, the muscle synergies are converted from activation level to the torque space to see how muscle synergy recruitment addresses the torque production in a specific direction at the shoulder joint. The results confirmed our expectation that the few dominant synergies are sufficient to address the torque vectors in directions which coincide to the basic vectors of torque space, such that each muscle contributed to more than one synergy
  5. Keywords:
  6. Muscle activation patterns ; Shoulder torque ; Synergy ; Activation level ; Control strategies ; External torque ; Glenohumeral joint ; Horizontal planes ; Isometric torque ; Muscle activation ; Nonnegative matrix factorization ; Number of degrees of freedom ; Numerical optimizations ; Numerical simulation ; One synergies ; Shoulder joints ; Shoulder models ; Torque vectors ; Biomechanics ; Matrix algebra ; Systems analysis ; Torque ; Vector spaces ; Muscle
  7. Source: ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010 ; Volume 1 , 2010 , Pages 797-804 ; 9780791849156 (ISBN)
  8. URL: http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1618050